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Genetic susceptibility and resistance to influenza infection and disease in humans and mice
Abstract
Although genetic risk factors for influenza infection have not yet been defined in people, differences in genetic background and related variation in the response to infection, as well as viral virulence, are all likely to influence both the likelihood of infection and disease severity. However, apart from characterization of viral binding sites in avian and mammalian hosts, relatively little investigation has focused on host genetic determinants of susceptibility or resistance to infection, or the severity of the associated disease in humans or other species. Similarly, the role of genetic background in the generation of an efficacious immune response to either infection or vaccination has not been extensively evaluated. However, genetic influences on susceptibility and resistance to numerous infectious agents and on the resultant host inflammatory and immune responses are well established in both humans and other animals. Mouse-adapted strains of human influenza viruses and the use of inbred strains of laboratory mice have supported extensive characterization of the pathogenesis and immunology of influenza virus infections. Like individual humans, inbred strains of mice vary in their reactions to influenza infection, particularly with regard to the inflammatory response and disease severity, supporting the potential use of these mice as a valuable surrogate for human genetic variation. Relying heavily on what we have learned from mice, this overview summarizes existing animal, human and epidemiologic data suggestive of host genetic influences on influenza infection.
... Host genetic factors may affect the development and progression of many infectious diseases [6]. Genetic polymorphisms appear to be important in explaining variations in immune response to influenza viruses, and specific genes may affect disease susceptibility or severity [7]. In this article, we describe a casecontrol association study to identify genetic polymorphisms associated with increased risk of severe A/H1N1 pneumonia, using HumanCVD BeadChips (Illumina, San Diego, CA, USA) containing more than 48,000 single-nucleotide polymorphism (SNP) probes targeting ,2,100 candidate genes [8]. ...
... Genomic DNA was isolated from EDTA-anticoagulated peripheral blood using Qiagen blood mini kits (Qiagen, Chatsworth, CA, USA), and was stored at -80uC. We used the ITMAT-Broad-CARe or ''IBC array'' (HumanCVD BeadChip; Illumina [7]), which incorporates ,50,000 SNPs, to efficiently capture genetic diversity across .2,000 genic regions related to cardiovascular, inflammatory and metabolic phenotypes. ...
... In the case of influenza A, wide variation in the susceptibility of different inbred laboratory strains of mice to infection indicates that the genetic background of the host makes major contributions to influenza A virus infections [28]. Nevertheless, little information is available on human genetic variation that may influence susceptibility to and severity of influenza virus infections [7]. A study of 100 candidate influenza susceptibility genes based on their potential role in the pathogenesis of influenza A infection has recently been suggested [29]. ...
The A/H1N1 influenza strain isolated in Mexico in 2009 caused severe pulmonary illness in a small number of exposed individuals. Our objective was to determine the influence of genetic factors on their susceptibility. We carried out a case-control association study genotyping 91 patients with confirmed severe pneumonia from A/H1N1 infection and 98 exposed but asymptomatic household contacts, using the HumanCVD BeadChip (Illumina, San Diego, CA, USA). Four risk single-nucleotide polymorphisms were significantly (p<0.0001) associated with severe pneumonia: rs1801274 (Fc fragment of immunoglobulin G, low-affinity IIA, receptor (FCGR2A) gene, chromosome 1; OR 2.68, 95% CI 1.69-4.25); rs9856661 (gene unknown, chromosome 3; OR 2.62, 95% CI 1.64-4.18); rs8070740 (RPA interacting protein (RPAIN) gene, chromosome 17; OR 2.67, 95% CI 1.63-4.39); and rs3786054 (complement component 1, q subcomponent binding protein (C1QBP) gene, chromosome 17; OR 3.13, 95% CI 1.89-5.17). All SNP associations remained significant after adjustment for sex and comorbidities. The SNPs on chromosome 17 were in linkage disequilibrium. These findings revealed that gene polymorphisms located in chromosomes 1 and 17 might influence susceptibility to development of severe pneumonia in A/H1N1 infection. Two of these SNPs are mapped within genes (FCGR2A, C1QBP) involved in the handling of immune complexes and complement activation, respectively, suggesting that these genes may confer risk due to increased activation of host immunity.
... Five review articles were identified. The review by Trammel and Toth summarized animal and human data on genetic influences on influenza infection, with a particular focus on studies of differential gene expression [89]. This review highlighted the earlier work of Toth et al that identified 75 immune related genes (including 13 interferon related genes and 10 chemokine related genes) that were differentially expressed in C57BL/6J compared to BALB/cByJ mice in response to influenza H3N2 HK-X31 infection [35]. ...
... Ding M (2008) [35] Complementary DNA microarray analysis of lung and basal forebrain of influenza H3N2 (HK-X31) infected and uninfected BALB/cByJ and C57BL/6J mice In lung, 361 different genes changed expression after influenza infection of BALB/cByJ mice as compared with 16 in C57BL/6J mice. Of 75 genes related to the immune response, 3 showed increased expression in the lungs of infected C57BL/6J mice, compared with 70 in infected BALB/cByJ mice.Trammell RA (2008)[89] Review article of human and animal data on host genetic susceptibility to influenza.Srivastava B (2009)[31] Comparison of response to H1N1 (PR8) infection in seven inbred laboratory mouse strains. Additional comparison of response to H7N7 (SC35M) infection in one of the susceptible strains (DBA/2J) and one of the more resistant strains (C57BL/6J). ...
The World Health Organization has identified studies of the role of host genetics on susceptibility to severe influenza as a priority. A systematic review was conducted in June 2011 to summarise the evidence on the role of host genetics in susceptibility to influenza, and this report updates that previously published review. Animal studies suggest that genetic control of susceptibility to severe influenza in mice is complex and not controlled by a single locus, but there is encouraging evidence that some of the host genetic determinants of susceptibility to severe disease may be common across influenza subtypes. Although a number of studies on genetic susceptibility to influenza in humans have been published recently, all are underpowered and unreplicated, so do not provide robust statistical evidence of an association between the identified genetic loci and susceptibility. One study does however present convincing functional evidence for an important role for IFITM3 in susceptibility to severe influenza in mice, and some evidence that this may also be important in human A/H1N1/pdm2009 infection.
... Several recent reviews (Horby et al. 2012(Horby et al. , 2013Korth et al. 2013;Trammell and Toth 2008) have discussed genetic variations of mice associated with influenza susceptibility. With the exception of MX1 (Ferris et al. 2013), the function and relative importance of most of these genetic factors are not well understood, although some are potentially associated with inflammation, such as Tnfrsf21 (Boivin et al. 2012), IL16, and Nox4 (Ferris et al. 2013). ...
... A major factor influencing the severity of influenza disease in mice is the inflammatory response induced by the virus, with increased inflammation being associated with increased disease severity (Askovich et al. 2013;Brandes et al. 2013;Cilloniz et al. 2010;Song et al. 2013a;. Many genes associated with inflammation are strongly upregulated following influenza infection of mice, especially following highly virulent viruses (Boon et al. 2011;Josset et al. 2012;Kash et al. 2006;Korth et al. 2013;Trammell and Toth 2008). Many of these genes are differentially regulated in different mouse strains (Alberts et al. 2010;Ding et al. 2008), with susceptible strains showing a more robust inflammatory response to influenza infection than do the more resistant strains (Alberts et al. 2010;Boon et al. 2011;Srivastava et al. 2009;Trammell et al. 2012), suggesting that at least one reason for differential influenza susceptibility may be variations in immune responses. ...
Mice are widely used for studying influenza virus pathogenesis and immunology because of their low cost, the wide availability of mouse-specific reagents, and the large number of mouse strains available, including knockout and transgenic strains. However, mice do not fully recapitulate the signs of influenza infection of humans: transmission of influenza between mice is much less efficient than in humans, and influenza viruses often require adaptation before they are able to efficiently replicate in mice. In the process of mouse adaptation, influenza viruses acquire mutations that enhance their ability to attach to mouse cells, replicate within the cells, and suppress immunity, among other functions. Many such mouse-adaptive mutations have been identified, covering all 8 genomic segments of the virus. Identification and analysis of these mutations have provided insight into the molecular determinants of influenza virulence and pathogenesis, not only in mice but also in humans and other species. In particular, several mouse-adaptive mutations of avian influenza viruses have proved to be general mammalian-adaptive changes that are potential markers of pre-pandemic viruses. As well as evaluating influenza pathogenesis, mice have also been used as models for evaluation of novel vaccines and anti-viral therapies. Mice can be a useful animal model for studying influenza biology as long as differences between human and mice infections are taken into account.
... Additionally, it should be pointed that there are variations in the protective response to influenca vaccine among adult individuals [16]. In the same line, using mouse models, strain-dependent variations in immune responses to influenza vaccine and susceptibility to influenza infection have been observed [17][18][19]. However, data on factors associated with individual variations in immune response to influenza vaccines are rather limited. ...
... To corroborate our findings, following immunization with either recombinant AcHERV-sH1N1-hemagglutin or killed virus vaccine, female BALB/c mice showed higher hemagglutin-specific IgG titers compared with those of C57BL/6 [33]. Moreover, although in mouse models susceptibility to influenza infection can be strongly influenced by host genetic factors [17,18], comparative studies on the susceptibility of BALB/c and C57BL/6 mice to influenza infection are also rather limited [34]. In line with the different levels of IgG responses to TIV in BALB/c and C57BL/6 mice, following the infection with influenza virus A/HKX31 (H3N2) more robust expression of many genes, including those related to immune functions, was found in BALB/cByJ compared with C57BL/6J mice [34]. ...
Aims:
The study examined the influence of sex and mouse strain on germinal center (GC) reaction and antibody responses to seasonal split trivalent influenza vaccine (TIV).
Main methods:
C57BL/6 and BALB/c mice of both sexes were immunized with TIV and examined for specific antibody response by ELISA. Splenic T follicular regulatory (Tfr), T follicular helper (Tfh) and GC B cells are detected by flow cytometry. The proliferative response of splenocytes, and concentrations of IFN-γ and IL-4 upon restimulation with vaccine antigens were examined by 7-AAD staining and ELISA, respectively.
Key findings:
BALB/c mice developed more robust IgG responses to vaccine type A antigens than their sex-matched C57BL/6 counterparts, while that to B antigen did not differ between strains. In both strains IgG responses against type A vaccine antigens were greater in females than in males. The greater IgG responses correlated with lower splenic Tfr/Tfh and Tfr/GC B cell ratios and greater vaccine antigen-specific proliferative responses of CD4+ and B cells in splenocyte cultures. In both mouse strains IgG2a(c)/IgG1 ratios were comparable between sexes, but lower in BALB/c than in C57BL/6 mice indicating a shift in Th1/Th2 balance towards Th2 response in BALB/c ones. Consistently, splenocytes from BALB/c mice produced more IL-4 and less IFN-γ than those from C57BL/6 mice.
Significance:
The study indicated that magnitude of humoral response to influenza type A haemagglutinins depends on mouse strain and sex, and thereby set background for the vaccination strategies taking into account biological sex, and in a longterm perspective individual differences in immune reactivity.
... The mouse has been shown to represent a valuable model system to evaluate the virulence and pathogenicity of presently circulating subtypes as well as newly emerging H5N1 and 2009 pandemic H1N1 subtypes (e.g. [5][6][7][8][9][10][11][12][13][14]). Bird viruses are able to infect the lungs of mice without prior adaptation but human isolates differ largely in their virulence in mice [15,16]. ...
... Studies in mice were initially performed in two inbred mouse strains, C57BL/6J and BALB/c. We and others demonstrated that the susceptibility to influenza virus infection largely varies among different inbred mouse strains [12,15,[17][18][19][20][21][22]. In particular, DBA/2J mice are highly susceptible to infections with mouse-adapted viruses. ...
Background
The mouse represents an important model system to study the host response to influenza A infections and to evaluate new prevention or treatment strategies. We and others reported that the susceptibility to influenza A virus infections strongly varies among different inbred mouse strains. In particular, DBA/2J mice are highly susceptible to several influenza A subtypes, including human isolates and exhibit severe symptoms after infection with clinical isolates.
Findings
Upon intra-muscular immunization with live H1N1 influenza A virus (mouse-adapted PR8M, and 2009 pandemic human HA04), DBA/2J mice mounted virus-specific IgG responses and were protected against a subsequent lethal challenge. The immune response and rescue from death after immunization in DBA/2J was similar to those observed for C57BL/6J mice.
Conclusions
DBA/2J mice represent a suitable mouse model to evaluate virulence and pathogenicity as well as immunization regimes against existing and newly emerging human influenza strains without the need for prior adaptation of the virus to the mouse.
... Gene variants significantly influence the susceptibility of humans to influenza virus infections (56). This is just as true in mouse and other organisms (19). ...
Acute lung injury (ALI) is an important cause of morbidity and mortality after viral infections, including influenza A virus H1N1, SARS-CoV, MERS-CoV, and SARS-CoV-2. The angiotensin I converting enzyme 2 (ACE2) is a key host membrane-bound protein that modulates ALI induced by viral infection, pulmonary acid aspiration, and sepsis. However, the contributions of ACE2 sequence variants to individual differences in disease risk and severity after viral infection are not understood. In this study, we quantified H1N1 influenza-infected lung transcriptomes across a family of 41 BXD recombinant inbred strains of mice and both parents—C57BL/6J and DBA/2J. In response to infection Ace2 mRNA levels decreased significantly for both parental strains and the expression levels was associated with disease severity (body weight loss) and viral load (expression levels of viral NA segment) across the BXD family members. Pulmonary RNA-seq for 43 lines was analyzed using weighted gene co-expression network analysis (WGCNA) and Bayesian network approaches. Ace2 not only participated in virus-induced ALI by interacting with TNF, MAPK, and NOTCH signaling pathways, but was also linked with high confidence to gene products that have important functions in the pulmonary epithelium, including Rnf128, Muc5b, and Tmprss2. Comparable sets of transcripts were also highlighted in parallel studies of human SARS-CoV-infected primary human airway epithelial cells. Using conventional mapping methods, we determined that weight loss at two and three days after viral infection maps to chromosome X—the location of Ace2. This finding motivated the hierarchical Bayesian network analysis, which defined molecular endophenotypes of lung infection linked to Ace2 expression and to a key disease outcome. Core members of this Bayesian network include Ace2, Atf4, Csf2, Cxcl2, Lif, Maml3, Muc5b, Reg3g, Ripk3, and Traf3. Collectively, these findings define a causally-rooted Ace2 modulatory network relevant to host response to viral infection and identify potential therapeutic targets for virus-induced respiratory diseases, including those caused by influenza and coronaviruses.
... The importance of host factors to host susceptibility and resistance has been demonstrated clearly in animal models. We and others have shown in mouse infection models that the susceptibility of the host to influenza A infection strongly depends on the genetic background [9][10][11][12][13][14][15][16][17]. In particular, DBA/2J mice are highly susceptible to many influenza A virus subtypes, including those that were directly derived from human isolates without prior adaptation to the mouse [9,13,[16][17][18]. ...
There is strong but mostly circumstantial evidence that genetic factors modulate the severity of influenza infection in humans. Using genetically diverse but fully inbred strains of mice it has been shown that host sequence variants have a strong influence on the severity of influenza A disease progression. In particular, C57BL/6J, the most widely used mouse strain in biomedical research, is comparatively resistant. In contrast, DBA/2J is highly susceptible.
To map regions of the genome responsible for differences in influenza susceptibility, we infected a family of 53 BXD-type lines derived from a cross between C57BL/6J and DBA/2J strains with influenza A virus (PR8, H1N1). We monitored body weight, survival, and mean time to death for 13 days after infection. Qivr5 (quantitative trait for influenza virus resistance on chromosome 5) was the largest and most significant QTL for weight loss. The effect of Qivr5 was detectable on day 2 post infection, but was most pronounced on days 5 and 6. Survival rate mapped to Qivr5, but additionally revealed a second significant locus on chromosome 19 (Qivr19). Analysis of mean time to death affirmed both Qivr5 and Qivr19. In addition, we observed several regions of the genome with suggestive linkage. There are potentially complex combinatorial interactions of the parental alleles among loci. Analysis of multiple gene expression data sets and sequence variants in these strains highlights about 30 strong candidate genes across all loci that may control influenza A susceptibility and resistance.
We have mapped influenza susceptibility loci to chromosomes 2, 5, 16, 17, and 19. Body weight and survival loci have a time-dependent profile that presumably reflects the temporal dynamic of the response to infection. We highlight candidate genes in the respective intervals and review their possible biological function during infection.
... More than 200 commercially available, phylogenetically diverse inbred mouse strains that contain enough genetic diversity to identify major differences in response to a specific infection are available [14]. These resources have been extensively used to identify cellular and molecular factors that may contribute to different disease pathogenesis and to analyze the effect of multiple contributing genetic loci influencing disease phenotype with different pathogens [10,12,15,16] [17]. Successful stories included gene mapping for a large number of pathogens like bacteria (e.g. ...
Pseudomonas aeruginosa is a common cause of healthcare-associated infections including pneumonia, bloodstream, urinary tract, and surgical site infections. The clinical outcome of P. aeruginosa infections may be extremely variable among individuals at risk and patients affected by cystic fibrosis. However, risk factors for P. aeruginosa infection remain largely unknown. To identify and track the host factors influencing P. aeruginosa lung infections, inbred immunocompetent mouse strains were screened in a pneumonia model system. A/J, BALB/cJ, BALB/cAnNCrl, BALB/cByJ, C3H/HeOuJ, C57BL/6J, C57BL/6NCrl, DBA/2J, and 129S2/SvPasCRL mice were infected with P. aeruginosa clinical strain and monitored for body weight and mortality up to seven days. The most deviant survival phenotypes were observed for A/J, 129S2/SvPasCRL and DBA/2J showing high susceptibility while BALB/cAnNCrl and C3H/HeOuJ showing more resistance to P. aeruginosa infection. Next, one of the most susceptible and resistant mouse strains were characterized for their deviant clinical and immunological phenotype by scoring bacterial count, cell-mediated immunity, cytokines and chemokines profile and lung pathology in an early time course. Susceptible A/J mice showed significantly higher bacterial burden, higher cytokines and chemokines levels but lower leukocyte recruitment, particularly neutrophils, when compared to C3H/HeOuJ resistant mice. Pathologic scores showed lower inflammatory severity, reduced intraluminal and interstitial inflammation extent, bronchial and parenchymal involvement and diminished alveolar damage in the lungs of A/J when compared to C3H/HeOuJ. Our findings indicate that during an early phase of infection a prompt inflammatory response in the airways set the conditions for a non-permissive environment to P. aeruginosa replication and lock the spread to other organs. Host gene(s) may have a role in the reduction of cell-mediated immunity playing a critical role in the control of P. aeruginosa infection. These results now provide a basis for mapping genomic regions underlying host susceptibility to P. aeruginosa infection.
... Therefore, the loss of essential cellular proteins causes necrosis and death of all infected cells (6). There are numerous individual factors that can determine a certain degree of protection from the virus or that conversely increase the risk of a fatal outcome as the result of a particular type of flu [7], together with genetic factors that are likely to affect this individual susceptibility [8]. ...
... A large amount of information has been accumulated from experimental animal studies [14,15,16,17,18,19]. However, these data were very seldom correlated with biomarkers in body fluids. ...
Influenza A infection is a serious threat to human and animal health. Many of the biological mechanisms of the host-pathogen-interactions are still not well understood and reliable biomarkers indicating the course of the disease are missing. The mouse is a valuable model system enabling us to study the local inflammatory host response and the influence on blood parameters under controlled circumstances. Here, we compared the lung and peripheral changes after PR8 (H1N1) influenza A virus infection in C57BL/6J and DBA/2J mice using virus variants of different pathogenicity resulting in non-lethal and lethal disease. We monitored hematological and immunological parameters revealing that the granulocyte to lymphocyte ratio in the blood represents an early indicator of severe disease progression already two days after influenza A infection in mice. These findings might be relevant to optimize early diagnostic options of severe influenza disease and to monitor successful therapeutic treatment in humans.
... For example, intranasal inoculation with the influenza virus in mice results in increases in non-rapid eye movement sleep (NREM) and decreases in rapid eye movement sleep (REM), though body temperature is decreased (Fang et al., 1995(Fang et al., , 1996Toth et al., 1995;Toth and Williams, 1999;Toth and Opp, 2001). Genetics play a role in the susceptibility and resistance to infectious agents (Cooke and Hill, 2001;Hill, 2001;De Maio et al., 2005;Tuite and Gros, 2006;Trammell and Toth, 2008;Trammell et al., 2012); e.g., the increases in NREM with influenza appear to be strain dependent because C57BL/6 (B6) mice display increases whereas BALB/c mice do not (Toth et al., 1995). ...
Intranasal application of vesicular stomatitis virus (VSV) produces a well-characterized model of viral encephalitis in mice. Within one day post-infection (PI), VSV travels to the olfactory bulb and, over the course of 7 days, it infects regions and tracts extending into the brainstem followed by clearance and recovery in most mice by PI day 14 (PI 14). Infectious diseases are commonly accompanied by excessive sleepiness; thus, sleep is considered a component of the acute phase response to infection. In this project, we studied the relationship between sleep and VSV infection using C57BL/6 (B6) and BALB/c mice. Mice were implanted with transmitters for recording EEG, activity and temperature by telemetry. After uninterrupted baseline recordings were collected for 2 days, each animal was infected intranasally with a single low dose of VSV (5 x 10(4) PFU). Sleep was recorded for 15 consecutive days and analyzed on PI 0, 1, 3, 5, 7, 10, and 14. Compared to baseline, amounts of non-rapid eye movement sleep (NREM) were increased in B6 mice during the dark period of PI 1-5, whereas rapid eye movement sleep (REM) was significantly reduced during the light periods of PI 0-14. In contrast, BALB/c mice showed significantly fewer changes in NREM and REM. These data demonstrate sleep architecture is differentially altered in these mouse strains and suggests that, in B6 mice, VSV can alter sleep before virus progresses into brain regions that control sleep.
... Known risk factors for both decreased vaccine response and more severe illness include age, chronic illness, pregnancy, and immunosuppression (2). Genetic factors also contribute to both decreased vaccine response and more severe influenza illness, including specific HLA haplo-Abbreviations: HA, hemagglutinin; HAU, hemagglutination unit; HI, hemagglutination inhibition; HO, heme oxygenase; LD, lethal dose; MCP-1, monocyte chemotactic protein-1; MIP-1, macrophage inflammatory protein-1; RANTES, regulated on activation normal T cell expressed and secreted; SNP, single-nucleotide polymorphism; TCID, tissue culture infective dose; TLR, Toll-like receptor; TNF-␣, tumor necrosis factor ␣; WT, wild type types, and polymorphisms in critical mediators of the immune response, such as TLRs (TLR3), proinflammatory cytokines (IL-6, IL-12, IL-18, and IFN␥), and cytokine receptors (IL-1R, IL-2R, IL-4R, IL-10R, IL-12R, and TNFR) (1,3). ...
Underlying mechanisms of individual variation in severity of influenza infection and response to vaccination are poorly understood. We investigated the effect of reduced heme oxygenase-1 (HO-1) expression on vaccine response and outcome of influenza infection. HO-1-deficient and wild-type (WT) mice (kingdom, Animalia; phylum, Chordata; genus/species, Mus musculus) were infected with influenza virus A/PR/8/34 with or without prior vaccination with an adenoviral-based influenza vaccine. A genome-wide association study evaluated the expression of single-nucleotide polymorphisms (SNPs) in the HO-1 gene and the response to influenza vaccination in healthy humans. HO-1-deficient mice had decreased survival after influenza infection compared to WT mice (median survival 5.5 vs. 6.5 d, P=0.016). HO-1-deficient mice had impaired production of antibody following influenza vaccination compared to WT mice (mean antibody titer 869 vs. 1698, P=0.02). One SNP in HO-1 and one SNP in the constitutively expressed isoform HO-2 were independently associated with decreased antibody production after influenza vaccination in healthy human volunteers (P=0.017 and 0.014, respectively). HO-1 deficient mice were paired with sex- and age-matched WT controls. HO-1 affects the immune response to both influenza infection and vaccination, suggesting that therapeutic induction of HO-1 expression may represent a novel adjuvant to enhance influenza vaccine effectiveness.
... An important role for these cells in the early events following respiratory virus infections has been previously suggested (Capelozzi et al. 2010;Culley 2009;Du et al. 2010;Jost et al. 2011;Mao et al. 2010). Animal models have shown that NK cells recruited to the lungs after experimental influenza virus infections contribute importantly at reducing viral replication (Stein-Streilein et al. 1983;Trammell and Toth 2008). However, NK cell activation has also been shown to contribute to inflammatory lung injury (Capelozzi et al. 2010;Harker et al. 2010;Okamoto et al. 2002). ...
Introduction of a novel influenza virus into the human population leads to the occurrence of pandemic events, such as the one caused by pandemic influenza A (H1N1) 2009 virus. The severity of infections caused by this virus in young adults was greater than that observed in patients with seasonal influenza. Fatal cases have been associated with an abnormal innate, proinflammatory immune response. A critical role for natural killer cells during the initial responses to influenza infections has been suggested. In this study, we assessed the association of killer-cell immunoglobulin-like receptors (KIRs) with disease severity by comparing KIR gene content in patients with mild and severe pandemic influenza virus infections to a control group. We found that activator (KIR3DS1 and KIR2DS5) and inhibitory (KIR2DL5) genes, encoded in group B haplotypes containing the cB01, cB03 and tB01 motifs, are associated with severe pandemic influenza A (H1N1) 2009 infections. Better understanding of how genetic variability contributes to influenza virus pathogenesis may help to the development of immune intervention strategies aiming at controlling the severity of disease.
... Mouse models clearly demonstrate a strong genetic effect on susceptibility to a range of influenza viruses and the severity of influenza infection [19][20][21]. Many candidate genes for susceptibility to severe influenza have been proposed based on understanding of the pathogenesis and immune evasion strategies of influenza virus and information gained from mice model and other invitro studies [22][23][24][25]. However, relatively few human studies have systematically evaluated the influence of genetic polymorphisms on susceptibility and disease severity in influenza infections [26][27][28][29][30][31][32][33][34][35]. ...
Background:
The pandemic potential of avian influenza viruses A(H5N1) and A(H7N9) remains an unresolved but critically important question.
Methods:
We compared the characteristics of sporadic and clustered cases of human H5N1 and H7N9 infection, estimated the relative risk of infection in blood-related contacts, and the reproduction number (R).
Results:
We assembled and analyzed data on 720 H5N1 cases and 460 H7N9 cases up to 2 November 2014. The severity and average age of sporadic/index cases of H7N9 was greater than secondary cases (71% requiring intensive care unit admission vs 33%, P = .007; median age 59 years vs 31, P < .001). We observed no significant differences in the age and severity between sporadic/index and secondary H5N1 cases. The upper limit of the 95% confidence interval (CI) for R was 0.12 for H5N1 and 0.27 for H7N9. A higher proportion of H5N1 infections occurred in clusters (20%) compared to H7N9 (8%). The relative risk of infection in blood-related contacts of cases compared to unrelated contacts was 8.96 for H5N1 (95% CI, 1.30, 61.86) and 0.80 for H7N9 (95% CI, .32, 1.97).
Conclusions:
The results are consistent with an ascertainment bias towards severe and older cases for sporadic H7N9 but not for H5N1. The lack of evidence for ascertainment bias in sporadic H5N1 cases, the more pronounced clustering of cases, and the higher risk of infection in blood-related contacts, support the hypothesis that susceptibility to H5N1 may be limited and familial. This analysis suggests the potential pandemic risk may be greater for H7N9 than H5N1.
... Five review articles were identified. The review by Trammel and Toth summarized animal and human data on genetic influences on influenza infection, with a particular focus on studies of differential gene expression [89]. This review highlighted the earlier work of Toth et al that identified 75 immune related genes (including 13 interferon related genes and 10 chemokine related genes) that were differentially expressed in C57BL/6J compared to BALB/cByJ mice in response to influenza H3N2 HK-X31 infection [35]. ...
The World Health Organization has identified studies of the role of host genetics on susceptibility to severe influenza as a priority. A systematic review was conducted to summarize the current state of evidence on the role of host genetics in susceptibility to influenza (PROSPERO registration number: CRD42011001380).
PubMed, Web of Science, the Cochrane Library, and OpenSIGLE were searched using a pre-defined strategy for all entries up to the date of the search. Two reviewers independently screened the title and abstract of 1,371 unique articles, and 72 full text publications were selected for inclusion. Mouse models clearly demonstrate that host genetics plays a critical role in susceptibility to a range of human and avian influenza viruses. The Mx genes encoding interferon inducible proteins are the best studied but their relevance to susceptibility in humans is unknown. Although the MxA gene should be considered a candidate gene for further study in humans, over 100 other candidate genes have been proposed. There are however no data associating any of these candidate genes to susceptibility in humans, with the only published study in humans being under-powered. One genealogy study presents moderate evidence of a heritable component to the risk of influenza-associated death, and while the marked familial aggregation of H5N1 cases is suggestive of host genetic factors, this remains unproven.
The fundamental question "Is susceptibility to severe influenza in humans heritable?" remains unanswered. Not because of a lack of genotyping or analytic tools, nor because of insufficient severe influenza cases, but because of the absence of a coordinated effort to define and assemble cohorts of cases. The recent pandemic and the ongoing epizootic of H5N1 both represent rapidly closing windows of opportunity to increase understanding of the pathogenesis of severe influenza through multi-national host genetic studies.
... México is a country with many different environments, which in principle could affect the predisposition of the population to different immunological insults [45,46] (see also [3,68]). In particular, the recent trend of urbanization and aging of the Mexican population could be increasing the vulnerability to acute infectious respiratory diseases [1]. ...
... of the type I interferon response during influenza infection appears to be important in both human and mouse models, as evidenced by the increased expression of genes including Irf1, Ifi202, Oas1, and Mx1 in mouse microarray studies737475 (reviewed in [76]). This is consistent with the observation that viral evasion and attenuation of the IFN pathway contributes to H5N1 pathogenesis in humans and suggests potential targets for genetic studies [75, 77]. ...
Following the 2009 H1N1 pandemic and ongoing sporadic avian-to-human transmission of H5N1 viruses, an emphasis has been placed on better understanding the determinants and pathogenesis of severe influenza infections. Much of the current literature has focused on viral genetics and its impact on host immunity as well as novel risk factors for severe infection (particularly within the H1N1 pandemic). An understanding of the host genetic determinants of susceptibility and severe respiratory illness, however, is currently lacking. By better defining the role of genetic variability in influenza infection and identifying key polymorphisms that impair the host immune response or correlate with protection, we will be able to better identify at-risk populations and new targets for therapeutic interventions and vaccines. This paper will summarize known immunogenetic factors associated with susceptibility or severity of both pH1N1 and H5N1 infections and will also identify genetic pathways and polymorphisms of high relevance for future study.
... The outcome of any interaction between a virus and host is determined by genetic and environmental factors and is manifest as either susceptibility to or chronicity of infection or severity of disease [1]. This interplay between host genetics and viral strain genomic sequence has been well defined in murine models of different viral infections, such as murine cytomegalovirus, retroviruses (Friend leukemia virus), and influenza virus [2][3][4]. In some human viral infections, eg, human immunodeficiency virus (HIV) infection, the effects of various host genes on viral acquisition, disease, and survival have been well defined. ...
asymptomatically in the saliva and genital secretions, respectively. Clinical lesions develop in only a portion of the shedding population. Worldwide, 50%‐100% and 10%‐90% of populations are infected with HSV-1 and HSV-2, respectively, but only a minority of infections present with dis
... For AI H5N1, arguments for genetic susceptibility include the preponderance of familial clustering of cases, with 50 of the 54 clusters detected globally (as of March 2009) having cases that were all genetically linked [18]. Further arguments include the paucity of cases in highly exposed groups such as poultry workers and the occurrence of familial cases separated by time and place [2,22,23]. This study lends further support to a genetic basis for susceptibility to AI H5N1 infection. ...
By 30 July 2009, Indonesia had reported 139 outbreaks of avian influenza (AI) H5N1 infection in humans. Risk factors for case clustering remain largely unknown. This study assesses risk factors for cluster outbreaks and for secondary case infection.
The 113 sporadic and 26 cluster outbreaks were compared on household and individual level variables. Variables assessed include those never reported previously, including household size and genealogical relationships between cases and their contacts.
Cluster outbreaks had larger households and more blood-related contacts, especially first-degree relatives, compared with sporadic case outbreaks. Risk factors for cluster outbreaks were the number of first-degree blood-relatives to the index case (adjusted odds ratio [aOR], 1.50; 95% confidence interval [CI]: 1.20-1.86) and index cases having direct exposure to sources of AI H5N1 virus (aOR, 3.20; 95% CI: 1.15-8.90). Risk factors for secondary case infection were being aged between 5 and 17 years (aOR, 8.32; 95% CI: 1.72-40.25), or 18 and 30 years (aOR, 6.04; 95% CI: 1.21-30.08), having direct exposure to sources of AI H5N1 virus (aOR, 3.48; 95% CI: 1.28-9.46), and being a first-degree relative to an index case (aOR, 11.0; 95% CI: 1.43-84.66). Siblings to index cases were 5 times more likely to become secondary cases (OR, 4.72; 95% CI: 1.67-13.35).
The type of exposure and the genealogical relationship between index cases and their contacts impacts the risk of clustering. The study adds evidence that AI H5N1 infection is influenced by, and may even depend on, host genetic susceptibility.
... More than 200 commercially available, phylogenetically diverse inbred mouse strains that contain enough genetic diversity to identify major differences in response to a specific infection are available [14]. These resources have been extensively used to identify cellular and molecular factors that may contribute to different disease pathogenesis and to analyze the effect of multiple contributing genetic loci influencing disease phenotype with different pathogens [10,12,15,16] [17]. Successful stories included gene mapping for a large number of pathogens like bacteria (e.g. ...
... Second, based only the fitting to the initial outbreak dynamics, we obtain qualitatively similar time courses for epidemics of the whole-country and also State by State. México is a country with many different environments, which in principle could affect the predisposition of the population to different immunological insults [45, 46] (see also [3, 68]). In particular, the recent trend of urbanization and aging of the Mexican population could be increasing the vulnerability to acute infectious respiratory diseases [1]. ...
Influenza outbreaks have been of relatively limited historical interest in Mexico. The 2009 influenza pandemic not only changed Mexico's health priorities but also brought to the forefront some of the strengths and weaknesses of Mexico's epidemiological surveillance and public health system. A year later, Mexico's data show an epidemic pattern characterized by three "waves''. The reasons this three-wave patterns are theoretically investigated via models that incorporate Mexico's general trends of land transportation, public health measures, and the regular opening and closing of schools during 2009. The role of vaccination is also studied taking into account delays in access and limitations in the total and daily numbers of vaccines available. The research in this article supports the view that the three epidemic "waves" are the result of the synergistic interactions of three factors: regional movement patterns of Mexicans, the impact and effectiveness of dramatic social distancing measures imposed during the first outbreak, and the summer release of school children followed by their subsequent return to classes in the fall. The three "waves" cannot be explained by the transportation patterns alone but only through the combination of transport patterns and changes in contact rates due to the use of explicit or scheduled social distancing measures. The research identifies possible vaccination schemes that account for the school calendar and whose effectiveness are enhanced by social distancing measures. The limited impact of the late arrival of the vaccine is also analyzed.
... Murine models have proven to be useful in studying the pathogenesis of influenza viruses [25]. Many mammalian genes including Mx1, Stat1, Pkr, Ifnar1, and Ncr1 genes have been found to be important in defining host defense against influenza [26][27][28][29]. ...
... We and others have shown in animal models that the genetic background of the host strongly influences mortality and morbidity after influenza infections. In particular, major differences in susceptibility and resistance were observed between different mouse inbred strains [3][4][5][6][7][8][9][10][11][12][13]. Detailed analysis of the mouse strains C57BL/6J and DBA/2J revealed that C57BL/6J mice survived infections with a low pathogenic A/Puerto Rico/8/1934 H1N1 virus (PR8M) whereas DBA/2J mice rapidly lost weight and all infected mice died [3,14]. ...
The host response to influenza A infections is strongly influenced by host genetic factors. Animal models of genetically diverse mouse strains are well suited to identify host genes involved in severe pathology, viral replication and immune responses. Here, we have utilized a dual RNAseq approach that allowed us to investigate both viral and host gene expression in the same individual mouse after H1N1 infection.
We performed a detailed expression analysis to identify (i) correlations between changes in expression of host and virus genes, (ii) host genes involved in viral replication, and (iii) genes showing differential expression between two mouse strains that strongly differ in resistance to influenza infections. These genes may be key players involved in regulating the differences in pathogenesis and host defense mechanisms after influenza A infections. Expression levels of influenza segments correlated well with the viral load and may thus be used as surrogates for conventional viral load measurements. Furthermore, we investigated the functional role of two genes, Reg3g and Irf7, in knock-out mice and found that deletion of the Irf7 gene renders the host highly susceptible to H1N1 infection.
Using RNAseq analysis we identified novel genes important for viral replication or the host defense. This study adds further important knowledge to host-pathogen-interactions and suggests additional candidates that are crucial for host susceptibility or survival during influenza A infections.
... Macrophages appear to be the critical immune cell type driving increased NREM sleep, whereas NK cells, neutrophils, and T lymphocytes do not play a significant role (Toth and Hughes, 2004). There are strain differences in responses of mice to this challenge (Toth and Verhulst, 2003), indicating a genetic component affecting the sleep response to influenza virus (Trammell and Toth, 2008). ...
Sleep disturbances including insomnia independently contribute to risk of inflammatory disorders, and major depressive disorder. This review and overview provides an integrated understanding of the reciprocal relationships between sleep and the innate immune system and considers the role of sleep in the nocturnal regulation of the inflammatory biology dynamics, the impact of insomnia complaints, extremes of sleep duration, and experimental sleep deprivation on genomic, cellular, and systemic markers of inflammation, and the influence of sleep complaints and insomnia on inflammaging and molecular processes of cellular aging. Clinical implications of this research include discussion of the contribution of sleep disturbance to depression and especially inflammation-related depressive symptoms. Reciprocal action of inflammatory mediators on the homeostatic regulation of sleep continuity and sleep macrostructure; and the potential of interventions that target insomnia to reverse inflammation are reviewed. Togther, interactions between sleep and inflammatory biology mechanisms underscores the implications of sleep disturbance for inflammatory disesease risk, and provides a map to guide the development of treatments that modulate inflammation, improve sleep, and promote sleep-health.Neuropsychopharmacology accepted article preview online, 11 August 2016. doi:10.1038/npp.2016.148.
... However, there may be genetic and/or modifiable behavioural factors that account for why international athletes succumb to fewer URI's than national level athletes during high-volume training. For example, there may be host genetic influences on URI (Trammell & Toth, 2008); whereby, elite athletes may be predisposed to have a more efficacious immune response to challenge with respiratory viruses; but this remains speculative. Recent evidence lends some support for this notion by showing that gene polymorphisms for the high expression of pro-inflammatory cytokines predict URI in highly trained athletes (Gleeson et al., 2017). ...
Numerous studies over the last 35 years report an increase in upper respiratory infection (URI) symptoms in athletes during periods of heavy training and competition. Challenges athletes face such as heavy exercise and life stress influence immune function via activation of the hypothalamic–pituitary–adrenal axis and the sympathetic nervous system and the resulting immunoregulatory hormones. Both innate and acquired immunity are often reported to decrease transiently in the hours after heavy exertion, typically 15–70%: prolonged heavy training sessions in particular have been shown to decrease immune function; potentially providing an ‘open window’ for opportunistic infections. Whether the observed changes in immunity with acute strenuous exercise or periods of heavy training account for the increased susceptibility to URI symptoms remains contentious. Nevertheless, there is little doubt that URI symptoms hinder athletic training and competition; underpinning the need to identify the prominent risk factors and appropriate countermeasures. Recent studies have identified prominent risk factors, including: intensified training in the winter; long-haul travel; low energy availability; high levels of psychological stress and anxiety; and depression. Given the shared pathways and effector limbs for the body’s response to physical and psychological challenges, it is logical that psychological strain influences immunity and illness incidence in athletes under heavy training; indeed, stress and anxiety have recently been shown to modify the immune response to exercise. This mini-review provides new insights and evidence-based recommendations for coping with the various challenges that athletes encounter on immune health, including: heavy exercise; life stress; sleep disruption; environmental extremes and nutritional deficits.
... Because influenza virus replication requires interaction with a number of host proteins and is moderated by antiviral proteins that are induced following infection, the genetic background of the host can impact consequent disease. 1 For example, data from in vitro studies showed that interferon (IFN)-inducible transmembrane (IFITM) protein family members restrict the replication of many different viruses. 2 The impact of IFITM3 on influenza replication was demonstrated in knockout mice and in examining the predominance of an IFITM3 gene variant in hospitalized influenza cases in China; these studies suggest this protein has a significant effect on disease severity. 3 However, the association of the IFITM3 variant with severe disease is not evident in all populations. ...
Susceptibility to influenza A virus is determined by a balance of viral and host factors. The genetic background of the host contributes to the severity of disease, but the influenza-related proteome of cells from different individuals have not been compared. We used high resolution mass spectrometry to identify proteins in normal human bronchial epithelial (NHBE) cells isolated from three different donors. Infection of each NHBE cell culture with influenza A/California/07/2009 (H1N1) resulted in expression of viral proteins and a variety of host proteins, including interferons, interferon-stimulated genes, and secreted chemokines/cytokines. The expression level of viral proteins corresponded with the level of host proteins that support influenza infection (i.e., pro-viral proteins), however, production of infectious virus was inversely related to the levels of antiviral proteins, suggesting that a balance of pro-viral proteins and the antiviral response controls virus replication. In summary, our results demonstrate that expression levels of pro-viral as well as antiviral factors are different for each donor and suggest that relative quantitation of these factors may provide a way to identify individuals or population groups who are susceptible to severe influenza disease.
The mouse is one of the most important mammalian model systems for studying host-pathogen-interactions during influenza A virus infections and for assessing the virulence of newly emerging influenza viruses. Here, we provide the basic protocols for infecting mice with influenza virus and studying the main pathological changes associated with disease. Critical parameters, e.g., virus variants and subtypes or mouse strains, are discussed. Curr. Protoc. Mouse Biol. 2:177-205 © 2012 by John Wiley & Sons, Inc.
Copyright © 2012 John Wiley & Sons, Inc.
Factors from the virus and the host contribute to influenza virus pathogenicity and to the development of immunity. This study thoroughly examined the effects of an initial infectious dose of virus and unveiled new findings concerning the antiviral and inflammatory responses, innate and adaptive immunity, memory responses, and protection against secondary heterologous infection. Our results demonstrated that the initial infectious dose significantly affects the gene expression of antiviral (IFN-β) and inflammatory (TNF-α, IL-6, IL-1β) cytokines and of enzymes involved in nitrosative/oxidative stress (iNOS, HO-1, NQO1) early in the response to influenza. This response correlated with significantly increased recruitment of innate immune cells into the lungs of infected mice. We showed that this response also alters the subsequent accumulation of activated IFN-γ(+) CD44(hi) CD62L(lo) influenza-specific CD8(+) T cells into the lungs of infected mice through increased T cell-recruiting chemokine gene expression (CCL3, CCL4, CCL5, CXCL10). Furthermore, we demonstrated that the initial infectious dose determines the generation and the distribution of memory CD8(+) T cell subsets without affecting trafficking mechanisms. This impacted on immune protection against heterologous infection. Lastly, we showed that the effects on innate and adaptive immunity were not dependent on influenza strain or on the genetic background of the host. Collectively, our data show for the first time and in detail that the initial infectious dose of influenza determines the development of several aspects of antiviral immunity. This study provides new insights on virus-host interaction in the generation of the global immune response to influenza.
Population-based epidemiological studies on infectious diseases are limited by methodological problems that may not be encountered in other fields of epidemiology. The acute or asymptomatic nature of many infections hinders a timely diagnosis by trained personnel in a study centre, indicating the need for new collection methods of biological specimens. One alternative approach is to have the participants collect the specimens themselves, for instance nasal swabs for the detection of bacterial or viral pathogens. Although self-collection is widely accepted in clinical studies of specific populations (e.g., self-collection of vaginal swabs by young women to diagnose sexually transmitted infections), it has not been employed much in population-based studies. Here, we review recent experience with self-collection of nasal swabs for the detection of microorganisms and discuss future prospects and applications for this technique.
The pandemic influenza (H1N1) 2009 raised a number of issues, of which we address the following: Why did between 25 and 30% of severe influenza cases show no obvious risk factor? We hypothesize that an element that can contribute to the answer are host genetic risk factors involved in poor disease progression. Several indications led us to this hypothesis: i) studies of familial aggregation in Iceland and Utah Mormons show some heritability of influenza mortality; ii) nearly 300 known human genes are necessary for the replication of the influenza virus, and iii) the most severe cases of influenza A (H1N1) 2009 showed a deregulation of the adaptive immune system. We are addressing this problem through a case-control design (hospitalized cases of influenza (H1N1) 2009 confirmed against outpatient cases, also confirmed for (H1N1) 2009), which will be genotyped for more than a million single nucleotide polymorphisms (SNPs) and copy number variations (CNVs).
Many studies of influenza severity have focused on viral properties that confer virulence, whereas the contributory role of the host genetic background on infection severity remains largely unexplored. In this study, we measure the impact of inoculation with influenza virus in four strains of inbred mice - BALB/cByJ, C57BL/6J, A/J, and DBA/2J. To evaluate the extent to which responses are inherent to lung per se, as opposed to effects of the systemic response to lung infection, we also measured cytokines and chemokines in lung slices exposed to the virus in vitro. Finally, we evaluate the in vivo responses of recombinant inbred (RI) and select consomic strains of mice to search for genomic loci that contribute to phenotypic variance in response to influenza infection. We found marked variation among mouse strains after challenge with virus strain A/HKX31(H3N2), consistent with previous reports using more virulent strains. Furthermore, response patterns differ after in vivo versus in vitro exposure of lung to virus, supporting a predominant role of the systemic host inflammatory response in generating the strain differences. These results add to the body of information pointing to host genotype as a crucial factor in mediating the severity of influenza infections.
Considering variability in vaccine responsiveness across human populations, in respect to magnitude and quality, and importance of vaccines in the elderly, the influence of recipient genetic background on the kinetics of age-related changes in the serum IgG antibody responses to seasonal trivalent inactivated split-virus influenza bulk (TIV) was studied in BALB/c and C57BL/6 mice showing quantitative and qualitative differences in this responses in young adult ages. With ageing the total serum IgG response to influenza viruses declined, in a strain-specific manner, so the strain disparity observed in young adult mice (the greater magnitude of IgG response in BALB/c mice) disappeared in aged mice. However, the sexual dimorphisms in this response (more prominent in females of both strains) remained in aged ones. The strain-specific differences in age-related decline in the magnitude of IgG response to TIV correlated with the number of germinal centre (GC) B splenocytes. The age-related decline in GC B cell number was consistent with the decrease in the proliferation of B cells and CD4+ cells in splenocyte cultures upon restimulation with TIV. Additionally, the age-related decrease in the magnitude of IgG response correlated with the increase in follicular T regulatory (fTreg)/follicular T helper (fTh) and fTreg/GC B splenocyte ratios (reflecting decrease in fTh and GC B numbers without changes in fTreg number), and the frequency of CD4+ splenocytes producing IL-21, a key factor in balancing the B cell and fTreg cell activity. With ageing the avidity of virus influenza-specific antibody increased in females of both strains. Moreover, ageing affected IgG2a/IgG1 and IgG2c/IgG1 ratios (reflecting Th1/Th2 balance) in male BALB/c mice and female C57BL/6 mice, respectively. Consequently, differently from young mice exhibiting the similar ratios in male and female mice, in aged female mice of both strains IgG2a(c)/IgG1 ratios were shifted towards a less effective IgG1 response (stimulated by IL-4 cytokines) compared with males. The age-related alterations in IgG subclass profiles in both strains correlated with those in IFN-γ/IL-4 production level ratio in splenocyte cultures restimulated with TIV. These findings stimulate further research to formulate sex-specific strategies to improve efficacy of influenza vaccine in the elderly.
Laboratory rodent influenza infection models have been and continue to be a critical tool for understanding virus-host interactions during infection. The incidence of seasonal influenza infections coupled with the need for novel therapeutics and universal vaccines highlights the need to uncover novel mechanisms of pathogenesis and protection. Mouse models are extremely useful for the evaluation of influenza vaccines and provide an invaluable tool to probe the immune response. This chapter describes the technique of intranasal inoculation of male C57BL/6J mice with an H1N1 strain of influenza (A/Puerto Rico/8/1934) and methods for assessing the optimum dose for infection, viral titers in lung tissue, and severity of disease.
Sex-based variations in the immune response to the influenza vaccines was reported, however, the genetic basis responsible for the sex variations in the immune response toward the influenza vaccines remains unclear. Here, the genes responsible for sex-specific responses after vaccination with trivalent inactivated influenza virus were identified. These genes were enriched in virus response pathways, especially interferon signaling. A list of genes showing different responses to the vaccine between females and males were obtained next. Our results demonstrated that females generate stronger immune responses to seasonal influenza vaccines within 24 hours than males. However, most of these genes with variability between sexes had the opposite expression levels after three days, suggesting that males retained the immune responses longer than female. To summary, our study identified genes responsible for the sex variations toward influenza vaccination. Our findings might provide insights into the development of the sex-dependent influenza vaccines.
reSUMen antecedentes: la influenza humana A H1N1 tiene diferentes patrones clínicos de presentación que van desde cuadros gripales de alivio espontáneo hasta una forma grave caracterizada por síndrome de insuficiencia respiratoria aguda, estado de choque y disfunción orgánica rápidamente progresiva. objetivo: hacer una propuesta relacionada con la concordancia fisiopatológica y de presentación entre la forma grave de la influenza humana A H1N1, la sepsis grave y el choque séptico. Caso clínico: pacientes con neumonía secundaria a influenza humana A H1N1 con sepsis grave y choque séptico que se trataron siguiendo los lineamientos de la campaña para incrementar la supervivencia en sepsis. Conclusiones: la forma grave de la influenza humana A H1N1 tiene el mismo sustrato fisiopatológico y comportamiento clínico, que la sepsis y el choque séptico inducidos por infección bacteriana, lo que hace necesario un abordaje diagnóstico y terapéutico semejante. Palabras clave: influenza humana A H1N1, sepsis, choque séptico, tormenta de citocinas. aBStraCt Background: H1N1 Influenza has several clinical patterns, from the autolimited flu-like symptomatology, to severe disease, characterized by acute respiratory distress syndrome, septic shock, and progressive multiorgan failure. The objective of this work is to make an evidence based proposal about the molecular and inflammation similarities, and clinical presentation between the severe form of the H1N1 influenza, severe sepsis and septic shock. Clinic Case: Patient with pneumonia secondary to influenza virus AH1N1 infection which developed severe sepsis and septic shock. The patient was treated following the guidelines from the surviving sepsis campaing. Conclusion: Sepsis and septic shock secondary to influenza A H1N1 infection has the same pathophysiological basis and clinical presen-tation than bacteria mediated severe sepsis and septic shock. This makes diagnostic and therapeutic approach similar in both diseases.
Die Effektivität von körperlicher Aktivität in der Primär- als auch Sekundär- und Tertiärprävention ist hinlänglich bekannt. Das Immunsystem spielt eine entscheidende Rolle bei einer Vielzahl von Erkrankungen, da es durch seine Botenfunktion (z. B. durch Zytokine) in einer Vielzahl der Regulationsprozesse mit involviert ist. So kommt es durch moderat-intensive körperliche Aktivität zu einer Stärkung des Immunsystems mit konsekutiv verminderter Infektanfälligkeit sowie eher anti-inflammatorischen Effekten, wohingegen langandauernde und höher intensive Belastungen zu einer Schwächung der Abwehrfunktion sowie einem pro-inflammatorischen Effekt führen. Somit stellt eine adäquat dosierte körperliche Aktivität eine erfolgversprechende Therapieoption bei Erkrankungen des infektiologischen Formenkreises sowie des Immunsystems dar.
Two studies of H5N1 avian influenza viruses that had been genetically engineered to render them transmissible between ferrets have proved highly controversial. Divergent opinions exist about the importance of these studies of influenza transmission and about potential 'dual use' research implications. No consensus has developed yet about how to balance these concerns. After not recommending immediate full publication of earlier, less complete versions of the studies, the United States National Science Advisory Board for Biosecurity subsequently recommended full publication of more complete manuscripts; however, controversy about this and similar research remains.
Influenza infections represent a serious threat to human health. Both extrinsic and intrinsic factors determine the severity of influenza disease. The MX dynamin-like GTPase 1 (Mx1) gene has been shown to confer strong resistance to influenza A virus infections in mice. Most laboratory mouse strains, including C57BL/6J, carry nonsense or deletion mutations in Mx1 and thus a non-functional allele, whereas wild-derived mouse strains carry a wild type Mx1 allele. Congenic C57BL/6J (B6-Mx1(r/r)) mice expressing a wild type allele from the A2G mouse strain are highly resistant to influenza A infections, to both mono- and poly-basic subtypes. Furthermore, in genetic mapping studies, Mx1 was identified as the major resistance locus to influenza infections. Here, we investigated whether the Mx1 protective function is influenced by the genetic background. For this, we generated a congenic mouse strain carrying the A2G wild type Mx1 resistance allele on a DBA/2J background (D2-Mx1(r/r)). Most remarkably, congenic D2-Mx1(r/r) mice expressing a functional Mx1 wild type allele are still highly susceptible to H1N1 virus. However, pre-treatment of D2-Mx1(r/r) mice with interferon α protected them from lethal infections. Our results showed, for the first time, that the presence of an Mx1 wild type allele from A2G as such does not fully protect mice from lethal influenza A virus infections. These observations are also highly relevant for susceptibility to influenza infections in humans.
Influenza A virus represents a major health threat to humans. Seasonal influenza epidemics cause high economic loss, morbidity and deaths each year. Genetic factors of the host strongly influence susceptibility and resistance to virus infections. The Mx1 (MX dynamin-like GTPase 1) gene has been described as a major resistance gene in mice and human. Most inbred laboratory mouse strains are deficient in Mx1 but congenic B6-Mx1(r/r) mice that carry the wild type Mx1 gene from the A2G mouse strain are highly resistant. Here, we show that, very unexpectedly, congenic D2-Mx1(r/r) mice carrying the wild type Mx1 gene from the A2G strain are not fully protected against lethal influenza infections. These observations demonstrate that the genetic background is very important for the protective function of the Mx1 resistance gene. Our results are also highly relevant for understanding genetic susceptibility to influenza infections in humans.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Background
We aimed to explore the detection profile of influenza viruses following live-attenuated intranasal influenza vaccination (LAIV) in children 2-19 years of age, with and without cystic fibrosis (CF).
Methods
Before the 2013-14 influenza season, flocked nasal swabs were obtained before vaccination and 4 times in the week of follow-up from 76 participants (nCF: 57; nhealthy:19). Influenza was detected by RT-PCR assays. A Bayesian hierarchical logistic regression model was used to estimate the effect of CF status and age on influenza detection.
Results
Overall, 69% of the study cohort shed influenza RNA during follow-up. The mean duration of RT-PCR detection was 2.09 days (95% CrI: 1.73, 2.48). The odds of influenza RNA detection on day 1 following vaccination decreased with age in years (OR: 0.82 per year, 95% CrI: 0.70, 0.95), and subjects with CF had higher odds of influenza RNA detection on day 1 of follow-up (OR: 5.09, 95% CrI: 1.02, 29.9).
Conclusion
Despite the small sample size, our results indicate that LAIV vaccine strains are detectable during the week post-LAIV, mainly in younger individuals and vaccinees with CF. It remains unclear whether recommendations for avoiding contact with severely immunocompromised patients should differ for these groups.
Viral diseases are important threats to public health worldwide. With the number of emerging viral diseases increasing the last decades, there is a growing need for appropriate animal models for virus studies. The relevance of animal models can be limited in terms of mimicking human pathophysiology. In this review, we discuss the utility of animal models for studies of influenza A viruses, HIV and SARS-CoV in light of viral emergence, assessment of infection and transmission risks, and regulatory decision making. We address their relevance and limitations. The susceptibility, immune responses, pathogenesis, and pharmacokinetics may differ between the various animal models. These complexities may thwart translating results from animal experiments to the humans. Within these constraints, animal models are very informative for studying virus immunopathology and transmission modes and for translation of virus research into clinical benefit. Insight in the limitations of the various models may facilitate further improvements of the models.
Beneficial effects of certain probiotic strains have been established in the treatment and prevention of various immune and intestinal disorders in humans, including allergic diseases, chronic inflammatory diseases and diarrhoea. The proposed mechanisms underlying the immunomodulatory effects of probiotics in humans are not understood in precise detail but include enhancement of intestinal barrier function, altered epithelial signalling, competition with pathogens and effects on immune cells and immunity depending on the probiotic strain. The publication of controversial or inconclusive probiotic studies in humans highlights the need for a better understanding of the mechanisms and improved strain selection criteria. This review focuses on the immunomodulatory properties of lactobacilli and bifidobacteria in vitro and in vivo, current knowledge concerning the mechanisms in vivo and challenges in translational research on probiotics. A better understanding of the molecular mechanisms of probiotics, the effect of probiotic mixtures versus single strains, the effect of formulation of probiotics and the fate of ingested probiotics should help to clarify the value of immune assays as selection criteria for probiotics.
Despite effective vaccines, influenza remains a major global health threat due to the morbidity and mortality caused by seasonal epidemics, as well as the 2009 pandemic. Also of profound concern are the rare but potentially catastrophic transmissions of avian influenza to humans, highlighted by a recent H7N9 influenza outbreak. Murine and human studies reveal that the clinical course of influenza is the result of a combination of both host and viral genetic determinants. While viral pathogenicity has long been the subject of intensive efforts, research to elucidate host genetic determinants, particularly human, is now in the ascendant, and the goal of this review is to highlight these recent insights.
Seasonal influenza is a serious respiratory illness that causes annual worldwide epidemics resulting in significant morbidity and mortality. Influenza pandemics occur about every 40 years, and may carry a greater burden of illness and death than seasonal influenza. Both seasonal influenza and pandemic influenza have profound economic consequences. The combination of current vaccine efficacy and viral antigenic drifts and shifts necessitates annual vaccination. New manufacturing technologies in influenza vaccine development employ cell culture and recombinant techniques. Both allow more rapid vaccine creation and production. In the past five years, brisk, highly creative activity in influenza vaccine research and development has begun. New vaccine technologies and vaccination strategies are addressing the need for viable alternatives to egg production methods and improved efficacy. At present, stubborn problems of sub-optimal efficacy and the need for annual immunization persist. There is an obvious need for more efficacious vaccines and improved vaccination strategies to make immunization easier for providers and patients. Mitigating this serious annual health threat remains an important public health priority.
This review outlines recent advancements in the understanding of athlete immune health. Controversies discussed include whether high levels of athletic training and environmental stress (e.g. heat acclimation, cryotherapy and hypoxic training) compromise immunity and increase upper respiratory tract infection (URTI). Recent findings challenge early exercise immunology doctrine by showing that international athletes performing high-volume training suffer fewer, not greater, URTI episodes than lower level performers and URTI incidence decreases, not increases, around the time of competition compared with heavy training. Herein we raise the possibility of host genetic influences on URTI and modifiable behavioural and training related factors underpinning these recent observations. Continued controversy concerns the proportion of URTI symptoms reported by athletes that are due to infectious pathogens, airway inflammation or as yet unknown causes and indeed whether the proportion differs in athletes and non-athletes. Irrespective of the cause of URTI symptoms (infectious or non-infectious), experts broadly agree that self-reported URTI hinders high-volume athletic training but, somewhat surprisingly, less is known about the influence on athletic performance. In athletes under heavy training both innate and acquired immunity are often observed to decrease, typically 15-25%, but whether relatively modest changes in immunity increase URTI susceptibility remains a major gap in knowledge. With the exception of cell-mediated immunity that tends to be decreased, exercising in environmental extremes does not provide an additional threat to immunity and host defence. Recent evidence suggests that immune health may actually be enhanced by regular intermittent exposures to environmental stress (e.g. intermittent hypoxia training).Immunology and Cell Biology accepted article preview online, 13 November 2015. doi:10.1038/icb.2015.99.
Purpose:
The objective of this study is to investigate the relation between sport training and the risk of common illnesses: upper respiratory tract and pulmonary infections (URTPI), muscular affections (MA), and all-type pathologies in highly trained swimmers.
Methods:
Twenty-eight French professional swimmers were monitored weekly for 4 yr. Training variables included 1) in-water and dryland intensity levels: low-load, high-load, resistance, maximal strength, and general conditioning training (expressed as the percentage of the maximal load performed by each subject, at each intensity level over the study period); and 2) training periods: moderate, intensive, taper, competition, and postcompetition. Illnesses were diagnosed by a sports physician using a standardized questionnaire. Mixed-effects logistic regression analyses were used to model odds ratios for the association between common illnesses and training variables, adjusted for sport season, semiseason (summer or winter), age, competition level, sex, and history of recent events, whereas controlling for heterogeneity among swimmers.
Results:
The risk of common illnesses was significantly higher in winter months, for national swimmers (for URTPI), and in cases of history of recent event (notably for MA). The odds of URTPI increased 1.08 (95% CI, 1.01-1.16) and 1.10 (95% CI, 1.01-1.19) times for every 10% increase in resistance and high-load trainings, respectively. The odds of MA increased by 1.49 (95% CI, 1.14-1.96) and 1.63 (95% CI, 1.20-2.21) for each 10% increase in high load and general conditioning training, respectively. The odds of illnesses were 50%-70% significantly higher during intensive training periods.
Conclusion:
Particular attention must be paid to illness prevention strategies during periods of intensive training, particularly in the winter months or in case of the recent medical episode.
Avian influenza A (H5N1) viruses cause severe disease in humans, but the basis for their virulence remains unclear. In vitro and animal studies indicate that high and disseminated viral replication is important for disease pathogenesis. Laboratory experiments suggest that virus-induced cytokine dysregulation may contribute to disease severity. To assess the relevance of these findings for human disease, we performed virological and immunological studies in 18 individuals with H5N1 and 8 individuals infected with human influenza virus subtypes. Influenza H5N1 infection in humans is characterized by high pharyngeal virus loads and frequent detection of viral RNA in rectum and blood. Viral RNA in blood was present only in fatal H5N1 cases and was associated with higher pharyngeal viral loads. We observed low peripheral blood T-lymphocyte counts and high chemokine and cytokine levels in H5N1-infected individuals, particularly in those who died, and these correlated with pharyngeal viral loads. Genetic characterization of H5N1 viruses revealed mutations in the viral polymerase complex associated with mammalian adaptation and virulence. Our observations indicate that high viral load, and the resulting intense inflammatory responses, are central to influenza H5N1 pathogenesis. The focus of clinical management should be on preventing this intense cytokine response, by early diagnosis and effective antiviral treatment.
A fundamental tenet of immunology is that primary adaptive immune responses are initiated in secondary lymphoid organs, such as lymph nodes, Peyer's patches or spleen 1–3 . These lymphoid organs are organ-ized to recruit naive lymphocytes from the blood and to promote their interaction with activated antigen-presenting cells from surrounding tissues 1 . Once lymphocytes have been activated and clonally expanded in centralized lymphoid organs, the resulting effector cells localize to the infected or inflamed tissues and perform their effector functions 4 . For example, B and T cells responding to influenza virus are first detected in the lymph nodes that drain the respiratory tract, and are only later found in the lung 5 . Consistent with an essential role for lymphoid organs in primary immune responses, splenectomized lymphotoxin-α-null (Lta –/–) mice 6,7 or alymphoplastic (aly/aly, also known as Map3k14 –/–) mice 8,9 — which lack spleen, lymph nodes and Peyer's patches — are unable to generate primary immune responses to a variety of pathogens 10 , anti-gens 11 and allografts 12 . However, Lta −/− mice infected with respiratory viruses are capable of generating antigen-specific B and T cells 13,14 , albeit with delayed kinetics, suggesting that lymphocytes can also be primed in non-lymphoid tissues. Consistent with this idea, the bone marrow seems to function as an alternative site of lymphocyte priming to systemic antigens when lymph nodes are unavailable 15,16 . Another tissue that could facilitate primary immune responses to respiratory infections is the BALT 17 . Although the presence of BALT in mouse and human lungs is controversial, there are reports that infection or inflammation triggers the organization of lymphoid structures in the lungs of both species 18–21 . These structures do not fit the classical defi-nition of BALT, as they are not formed independently of antigen 22,23 . Because inducible BALT (iBALT) appears in the lung only after infection or inflammation, it is generally assumed that iBALT is simply an accumulation of effector cells that were initially primed in conven-tional lymphoid organs; however, it is also possible that inflammatory responses directly trigger the neo-formation of iBALT, which promotes the recruitment, priming and expansion of antigen-specific lymphocytes in situ. Thus, iBALT may functionally replace conven-tional lymphoid organs in respiratory immune responses. RESULTS Respiratory immunity in the absence of lymphoid organs To determine whether CD8 + T cells could be primed in the absence of conventional lymphoid organs, we generated bone marrow chimeric mice lacking lymphoid organs or LTα (Supplementary Fig. 1 online). These chimeras include wild-type (WT) mice, which possess all lymphoid organs and are populated with Lta +/+ cells; lymphotoxin chimeric (LTCh) mice, which contain all lymphoid organs and are populated with Lta –/– cells; spleen-, lymph node– and Peyer's patch–deficient (SLP) mice, which lack lymphoid organs and are pop-ulated with Lta +/+ cells; lymphotoxin knockout (LTKO) mice, which lack lymph nodes and Peyer's patches and are populated with Lta −/− cells; and, finally, splenectomized LTKO (LTKO-S) mice, which lack lymphoid organs and are populated with Lta –/– cells. After reconstitu-tion, we infected the chimeric mice with influenza and followed influenza-specific CD8 + T cells in the lungs. Although influenza nucle-oprotein (NP)-specific CD8 + cells were observed in the lungs of WT, LTCh and SLP chimeric mice by day 7 (Fig. 1a), the appearance of NP-specific CD8 + cells was delayed until after day 9 in LTKO mice, and was even further delayed in LTKO-S mice. Despite the delayed appearance of NP-specific CD8 + cells in LTKO and LTKO-S mice, the total number of these cells in the lungs eventually reached almost wild-type levels (Fig. 1b).
Influenza A and B viruses are negative-strand RNA viruses that cause regular outbreaks of respiratory disease and substantially impact on morbidity and mortality. Our primary defense against the influenza virus infection is provided by neutralizing antibodies that inhibit the function of the virus surface coat proteins hemagglutinin and neuraminidase. Production of these antibodies by B lymphocytes requires help from CD4+ T cells. The most commonly used vaccines against the influenza virus comprise purified preparations of hemagglutinin and neuraminidase, and are designed to induce a protective neutralizing antibody response. Because of regular antigenic change in these proteins (drift and shift mutation), the vaccines have to be administered on an annual basis. Current defense strategies center on prophylactic vaccination of those individuals who are considered to be most at risk from the serious complications of infection (principally individuals aged >65 years and those with chronic respiratory, cardiac, or metabolic disease). The clinical effectiveness of influenza virus vaccination is dependent on several vaccine-related factors, including the quantity of hemagglutinin within the vaccine, the number of doses administered, and the route of immunization. In addition, the immunocompetence of the recipient, their previous exposure to influenza virus and influenza virus vaccines, and the closeness of the match between the vaccine and circulating influenza virus strains, all influence the serologic response to vaccination.
Human MxA and mouse Mx1 are interferon-induced proteins capable of inhibiting the multiplication of influenza virus. MxA protein is localized in the cytoplasm, whereas Mx1 protein accumulates in the nucleus. Taking advantage of stably transfected cell lines that constitutively express either MxA or Mx1 protein, we examined the steps at which these proteins block influenza A viruses. In infected cells expressing MxA protein, all viral mRNAs synthesized as a result of primary transcription in the nucleus by the virion-associated RNA polymerase accumulated to normal levels. These primary viral transcripts were polyadenylated, were active in directing viral protein synthesis in vitro, and appeared to be efficiently transported to the cell cytoplasm. Yet viral protein synthesis and genome amplification were strongly inhibited, suggesting that MxA protein interfered with either intracytoplasmic transport of viral mRNAs, viral protein synthesis, or translocation of newly synthesized viral proteins to the cell nucleus. However, in infected cells expressing Mx1 protein, the concentrations of the longest primary transcripts encoding the three influenza virus polymerase proteins PB1, PB2, and PA were at least 50-fold reduced. Accumulation of the shorter primary transcripts encoding the other viral proteins was also inhibited but to a lesser extent. These results demonstrate that the mouse Mx1 protein interferes with primary transcription of influenza virus in the nucleus, whereas the human MxA protein inhibits a subsequent step that presumably takes place in the cytoplasm of infected cells.
MxA and MxB are interferon-induced proteins of human cells and are related to the murine protein Mx1, which confers selective resistance to influenza virus. In contrast to the nuclear murine protein Mx1, MxA and MxB are located in the cytoplasm, and their role in the interferon-induced antiviral state was unknown. In this report we show that transfected cell lines expressing MxA acquired a high degree of resistance to influenza A virus. Surprisingly, MxA also conferred resistance to vesicular stomatitis virus. Expression of MxA in transfected 3T3 cells had no effect on the multiplication of two picornaviruses, a togavirus, or herpes simplex virus type 1. Treatment of MxA-expressing cells with antibodies to mouse alpha-beta interferon did not abolish the resistance phenotype. The conclusion that resistance to influenza virus and vesicular stomatitis virus was due to the specific action of MxA is further supported by the observation that transfected 3T3 cell lines expressing the related MxB failed to acquire virus resistance.
A single intracheal dose of liposome-encapsuled dichloro-methylene-diphosphonate resulted in the elimination of alveolar macrophages (AM) from the lung, creating a model to study the in vivo role of AM in the pulmonary immune response. Using intratracheally administered trinitrophenyl-keyhole limpet hemocyanin (TNP-KLH), the kinetics of the response, the location and number of TNP-specific antibody-forming cells, and the different Ig classes of the antibodies produced were studied in AM-depleted animals. The results show that AM elimination has a dramatic effect on the pulmonary immune responses against TNP-KLH. An increase in APC in lung-associated lymph nodes and a prolongation of the response is found, as well as an introduction of APC in lung tissue. In both experimental groups, the majority of the TNP-specific antibodies produced was IgG, followed by IgA and IgE, while very few IgM antibodies could be detected. We conclude from these results that AM are likely to play a role in controlling the pulmonary immune response in a suppressive way, thereby limiting the possible damage caused by severe immune responses in lung tissue.
Slow-wave sleep-promoting factors in brain and urine were identified as muramyl peptides (MPs), the building blocks of bacterial cell wall peptidoglycan. In this study, structural variations of MPs that occur naturally in bacterial peptidoglycan were investigated for somnogenic activity. Monomeric and dimeric MPs were isolated and purified from Neisseria gonorrhoeae and Actinomadura sp. strain R39. The structures of these MPs were verified by fast atom bombardment mass spectroscopy and tandem mass spectroscopy. After intracerebroventricular administration of MPs, electroencephalograms and brain temperatures of rabbits were recorded for 6 h and were analyzed to determine durations of slow-wave sleep, rapid-eye-movement sleep, and wakefulness. The 6-O acetylation of muramic acid enhanced the somnogenic effects of certain monomeric MPs relative to their non-O-acetylated (but otherwise identical) counterparts. Two monomeric MPs containing an unsubstituted amide (i.e., Iso-Gln) were inactive, thus confirming previous results showing that amidation of a variety of MPs can block somnogenic activity. Two peptide-cross-linked MP dimers tested had no effect on slow-wave sleep, although a third peptide-cross-linked MP containing a 1,6-anhydro muramyl end on one of its monomeric subunits, a structure that enhances somnogenic potency of un-cross-linked monomers, was somnogenic. Two dimers connected by glycosidic bonds and containing an Iso-Gln moiety were inactive. Two other glycosidically linked dimers that also contained an Iso-Gln moiety, but were of lower molecular weight, were somnogenic. In summary, 6-O acetylation of muramic acid in somnogenic MPs enhances activity, and as a class, peptide-linked dimeric MPs tend to be less active than their constituent monomers.
The IgG subclass responses to cold-adapted (ca) influenza A/Queensland/6/72 virus and purified haemagglutinin H3 was assessed in C57BL/6 and BALB/c mice. In BALB/c mice IgG2a was present as the major subclass in serum, lung and salivary secretions after two doses of ca virus. In contrast, the serum response in C57BL/6 mice was predominantly IgG1 after primary and secondary inoculations of ca virus. However, in lung and salivary secretions no specific subclass was dominant. When purified H3 was used as the inoculum, serum responses were dominated by IgG1 in BALB/c mice after two inoculations whereas all four subclasses were present at equal levels in C57BL/6 mice. Overall the lung and salivary responses detected in C57BL/6 mice were lower than those observed in BALB/c mice with all four subclasses contributing equally to the response in BALB/c mice. The neutralizing and haemagglutination inhibition abilities of the four Protein A-Sepharose-purified IgG subclasses differed between the BALB/c, C57BL/6 and CBA/CaH mice strains. IgG1 and IgG2a were most effective in BALB/c mice and in C57BL/6 and CBA/CaH mice, IgG2a and IgG2b. These results are discussed in terms of the differing abilities of replicating and non-replicating virus to stimulate differential responses in mice and the TH1 and TH2 helper cell concept.
Human genetic variation is a major determinant of susceptibility to many common infectious diseases. Malaria was the first disease to be studied extensively and many susceptibility and resistance loci have been identified. However, genes for other diseases such as HIV/AIDS and mycobacterial infections are now being identified using a variety of approaches. A large number of genes appear to influence susceptibility to infectious pathogens and defining these can provide insights into pathogenic and protective mechanisms and identify new molecular targets for prophylactic and therapeutic interventions. Immunogenetic associations with infectious diseases have considerable potential to guide immunomodulatory interventions and vaccine design.
Background: The influence of genetic polymorphisms of interleukin (IL)-10, tumour necrosis factor (TNF)-α, and IL-6 gene promoters on severity of systemic inflammatory response syndrome (SIRS) associated with community acquired pneumonia (CAP) was studied. Methods: Using PCR-RFLP analysis we analysed a −1082G/A single nucleotide polymorphism (SNP) of the anti-inflammatory IL-10 gene, a −308G/A SNP of the pro-inflammatory TNF-α gene and a −174G/C SNP of the IL-6 gene. Illness severity was stratified according to SIRS score, calculated by presence of up to four physiological indices: temperature, white blood cell count, heart rate and respiratory rate (non-SIRS, SIRS 2, SIRS 3, and SIRS 4). Results: A statistically significant stepwise increase in frequency of the IL-10 G allele, associated with higher expression of the gene, was observed in patients with increasing severity of illness from non-SIRS (n=19) to SIRS 2 (n=17), SIRS 3 (n=33) and SIRS 4 (n=24). This was primarily due to a higher frequency of the GG genotype with increasing severity from non-SIRS through to SIRS 4. IL-10 G allele frequency was also increased in patients who died as a result of CAP (n=11) compared with CAP survivors (n=82) (p=0.01). No association was seen between the TNF-α −308G/A and IL-6 −174G/C SNPs and disease. Additionally, no interaction between all three SNP genotypes and disease severity was observed. Conclusions: A polymorphism affecting IL-10 expression may influence the severity of illness in patients with CAP.
Experiments in rabbits were designed to test the two unproven assumptions of the hypothesis proposed in the companion paper (1): that Original Antigenic Sin is fundamentally a restricted anamnestic response, and that there exists a trapping mechanism capable of deflecting antigen from one kind of cell and guiding it to another.
It is shown that whole-body X-irradiation, sufficient to abolish primary but not secondary production of antibodies, leaves all manifestations of the Original Antigenic Sin untouched. This proves the first assumption.
Primary immune animals challenged with very large doses of a related antigen produce an immediate response of cross-reactive antibodies, followed by a standard primary response to the challenging antigen. When boosted with an appropriate mixture of both antigens, the response is of standard secondary type to the homologous antigen, followed by a standard primary response to the crossreacting antigen. When animals are primarily vaccinated with a mixture of two related antigens, small booster doses of either will stimulate a standard secondary response only. When such animals are given very large booster doses of either antigen, the response is a compound of a homologous secondary and of an Original Antigenic Sin-type against the related antigen. Each of these findings demonstrates a corollary of the second assumption.
The results are discussed in terms of the limitations they impose on theories concerned with the production of antibodies.
When primary immunity is boosted not by the homologous but by a crossreacting vaccine, the newly formed antibodies react better with the primary antigen than with the antigen actually eliciting the response. This phenomenon bears the name of Original Antigenic Sin (1).
It is shown that the number of antibody molecules produced against the original and the vaccinating antigen is the same; that each of these molecules is capable of reacting with both antigens; that the activity of an antiserum can be completely absorbed with either antigen; that both residual and adsorbed-dissociated fractions of antibody exhibit the same relative affinities towards the two antigens as did the native serum; that, unlike standard primary and secondary responses, the population of antibody molecules characterizing the Original Antigenic Sin is homogeneous; that each molecule has a lower equilibrium constant (i.e. higher avidity) against the original antigen than against the antigen stimulating the present response; and that all equilibrium constants are typical of secondary antibody.
It is concluded that the Original Antigenic Sin is a partial anamnestic response, a related antigen stimulating that sector only of the originally primed cells which is destined to produce cross-reacting antibody.
A hypothesis is developed according to which the basic difference between primary and secondary reactivity rests on the presence of a trapping mechanism that allows anamnestic production of antibody against lower doses of the homologous antigen. Such a mechanism is capable of cross-trapping related antigens, thus preventing a standard primary response and allowing manifestations of Original Antigenic Sin.
Experiments in rabbits were designed to test the two unproven assumptions of the hypothesis proposed in the companion paper (1): that Original Antigenic Sin is fundamentally a restricted anamnestic response, and that there exists a trapping mechanism capable of deflecting antigen from one kind of cell and guiding it to another. It is shown that whole-body X-irradiation, sufficient to abolish primary but not secondary production of antibodies, leaves all manifestations of the Original Antigenic Sin untouched. This proves the first assumption. Primary immune animals challenged with very large doses of a related antigen produce an immediate response of cross-reactive antibodies, followed by a standard primary response to the challenging antigen. When boosted with an appropriate mixture of both antigens, the response is of standard secondary type to the homologous antigen, followed by a standard primary response to the crossreacting antigen. When animals are primarily vaccinated with a mixture of two related antigens, small booster doses of either will stimulate a standard secondary response only. When such animals are given very large booster doses of either antigen, the response is a compound of a homologous secondary and of an Original Antigenic Sin-type against the related antigen. Each of these findings demonstrates a corollary of the second assumption. The results are discussed in terms of the limitations they impose on theories concerned with the production of antibodies.
Mice develop changes in sleep during the nonspecific immune response that occurs during the initial few days after inoculation with influenza virus. T lymphocytes, neutrophils, macrophages, and natural killer (NK) cells all participate in the early host response to influenza infection. All of these cell types are potential sources of endogenous substances that modulate sleep, but the contributory role of each cell type to the alteration of somnolence during infection has not been determined. To investigate which cell types contribute to the sleep enhancement that develops during influenza infection in mice, the sleep patterns of C57BL/6J mice with perturbations of particular facets of host immune response capabilities were assessed before and after influenza infection. Targeted mutation of the gene Ccl3 (macrophage inflammatory protein 1α)) prevented development of the dark phase sleep enhancement that is characteristic of C57BL/6J mice after influenza infection. Other experimental treatments that impair macrophage or monocyte function also produced significant (administration of pentoxifylline or CNI-1493) or marginally significant (deletion of the interferon-gamma gene or intranasal administration of carrageenan) changes in influenza-induced sleep enhancement in C57BL/6J mice. In contrast, functional impairments of NK cells, neutrophils, and T lymphocytes did not significantly influence sleep responses. These data therefore support a contributory role for macrophages, but not for NK cells, neutrophils, and T lymphocytes, in eliciting the sleep response typical of influenza-infected C57BL/6J mice.
Cells which are cytotoxic for both virus-infected and uninfected target cells can be recovered from the spleens of mice injected with either infectious or non-infectious influenza A virus. Peak activity occurs at 1-2 days and decreases to low levels by day 6. The effector cells are insensitive to anti-Thy 1 antibody and complement treatment, are not H-2 restricted, do not adhere to plastic and are unaffected by silica or carrageenan. In this sense and in the pattern of susceptibility to lysis of a variety of cultured cell lines, these effector cells have the properties of natural killer (NK) cells and are referred to as such. They are present to an increased level of activity in nude (nu+/nu+) mice and to a low level of activity in beige (bg+/bg+) mice, but upon injection of virus there is a significant increase in activity in both hosts. Such cells were also recovered from the lungs of mice infected intranasally with a lethal or sublethal dose of virus. In the former case, maximum activity was reached 2 days post infection and the activity remained high until death; in the latter case, peak activity was reached 4 days after virus inoculation and by day 11 the activity had decreased to pre-infection levels. After intranasal inoculation of influenza virus, both beige mice and their heterozygous littermates contained similar levels of infectious virus in their lungs. However, this result does not eliminate the possibility that these cells may help to limit virus infection.
In experimental human influenza infection initiated by nasal inoculation, the magnitude of viral replication, fever, and symptoms correlate with nasopharyngeal lavage fluid levels of various cytokines. Our aim was to assess these relationships in patients with naturally occurring acute influenza. Patients with culture-positive influenza illness of less than 36 hr of duration were studied. Nasopharyngeal washing were collected at enrollment and on Day 2, 4, 6 and 8 for quantitative virus isolation and IL-6, TNF-alpha, INF-alpha, INF-gamma and IL-10 determinations. Blood samples collected at entry and on Day 2 and 6 were processed to assess plasma cytokines and circulating influenza RNA. Patients received either oseltamivir or placebo for 5 days. We assessed the correlation between nasopharyngeal lavage fluid or blood levels of cytokines before treatment and viral titers, symptom severity and fever. Sixteen adult subjects (median age of 22 years) were studied, in this small group of patients no significant differences between placebo and oseltamivir patients were found in viral replication or measures of cytokines. Thus the data for all 16 subjects were pooled for analysis. At entry, influenza A viruses were cultured from nasopharyngeal washes at a median titer of 4.8 log(10)TCID(50)/ml of wash. Viral titers correlated positively with symptom score (P=0.006) and temperature values (P <0.001). Viral titers, fever and symptoms were highest at enrollment and fell in parallel during the subsequent days. RT-PCR assays failed to detect influenza RNA in the white blood eel Is from any patient. We observed a significant release, in both nasopharyngeal lavage fluid and in plasma, of IL-6, TNF-alpha, INF-alpha, INF-gamma and IL-10. At entry high IL-6 levels were detected in the nasopharyngeal lavage fluid (median 10.3 pg/ml) and plasma (median 5.1 pg/ml) of all patients. We found a positive correlation between plasma IL-6 levels and both symptom scores and temperature values (P <0.05), as well as a positive correlation between nasopharyngeal lavage fluid levels of IL-6 and TNF-alpha and temperature (P <0.05). We did not find significant associations between symptoms, fever and levels of INF-alpha, INF-gamma or IL-10. The magnitude of early decrease in viral titers correlated with initial levels of INF-gamma in nasopharyngeal ravage fluid (P <0.05). Significant production of IL-6, TNF-alpha, INF-alpha ,INF-gamma and IL-10 occurs in response to community acquired influenza A illness. As in experimental influenza, symptoms and fever in natural acute influenza correlate with the release of IL-6. J. Med. Virol. 64:262-268, 2001. (C) 2001 Wiley-Liss, Inc.
The gene coding for the α,β-interferon (α,β-IFN) receptor is localized to chromosome 21. Cells from patients with Down's syndrome contain an extra chromosome 21, and thereby an expected 1.5-times increase in the number of genes located to this chromosome and in consequence a 1.5-times increase in cell surface α-IFN receptors. Actual measurements of these by competition binding experiments with human recombinant α-IFN on peripheral blood mononuclear cells (PBMC) from patients with Down's syndrome resulted in a mean of 1.69, which is in accordance to the theoretical 1.50, but slightly overestimated due to the calculation method. The increased gene dosage of the α-IFN receptor was quantitatively verified by Southern blot-hybridizations. Further characterization of α-IFN receptor binding showed insignificant differences in dissociation constants among patients and healthy individuals.
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Activation of 202 and (2′-5′)(A)n synthetase genes after injection of interferon (IFN)-inducing, double-stranded, poly rl;rC was compared in various mouse strains. The 202 mRNA level increased 4.5- to 10-fold in DBA/2, BALB/c, and C3H/HeJ mice, whereas in C57BL/6 mice it rose only to about that in untreated DBA/2, BALB/c, and C3H/He1 mice. To determine whether this low level was due to a reduced transcription rate, a nuclear “run-on” assay was performed with NIH 3T3 cells or BLK cells derived from C57BU6 mice. IFN-a increased the 202 mRNA transcription severalfold in NIH 3T3 cells only, and that of a (2′-5′)(A)n synthetase gene in both cell lines. The possibility that an alteration in transacting factors could be responsible for this difference was examined. For this purpose the 5′ terminal flanking region (called the b segment, about 0.8 kb) of the 202 gene was linked to a heterologous reporter gene-chloramphenicolacetyltransferase (CAT) and transfected into normal or transformed NIH 3T3 cells and into various C57BU6-derived cell lines. IFN-α induced strong CAT activity in transfected normal or transformed NIH 3T3 cells, but a much lower activity in those from C57BU6 mice. The b segment contains an IFN-responsive element (ISRE) (35 bp) homologous to that present in several other IFN-inducible genes. Three tandem copies of the 202 ISRE were linked to an enhancerless SV40 early promoter driving an influenza virus hemagglutinin (HA) cDNA segment. No increase in HA mRNA expression was detected in the transfected BLK cell line derived from C57BL/6 mice following IFN treatment, whereas in the NIH 3T3 cell line, the IFN treatment resulted in a 2.5-fold increase. These and other results suggest that C57BU6 mice and cell lines derived from them might carry defective transacting factors impairing the ability of IFN-α to activate the 202 gene without impairing its ability to activate a (2′–5′)(A)n synthetase gene.
Natural killer (NK) activity and antibody-dependent cell mediated cytotoxicity (ADCC) against a human myeloid target cell line (K 562) was measured in adult patients with trisomy-21 (Down's syndrome) and in chromosomally normal age and sex matched control subjects. The effect of human leucocyte interferon (IFN-alpha) on the NK activity was also estimated. Spontaneous NK activity was stronger in the adult patients with trisomy-21 than in the healthy controls, but the difference did not reach statistical significance. The augmentation of NK activity by IFN-alpha, measured using lymphocytes not depleted of monocytes as effector cells, was statistically significant in both the trisomic patients (P less than 0.004) and the healthy controls (P less than 0.0005). Using monocyte and macrophage depleted lymphocytes in the patients with trisomy-21 the NK activity proved stronger than in the healthy controls, but not significantly and IFN-alpha did not augment it as it did in the healthy controls (P = n.s., P less than 0.05), for augmentations respectively). These results support the view that monocytes and macrophages are connected with the NK cell system. ADCC correlated with NK activity in both groups. Since NK cells are important components of many immune processes, including tumour and virus and/or bacteria-infected cell elimination, and have regulatory functions in immune reactions, the deficient augmentation of trisomic NK cells shown in vitro with extrinsic human leucocyte interferon may, paradoxically be an explanation for the greater susceptibility of trisomic individuals to lymphatic leukaemia and virus and bacterial infections. In vivo, this could be explained by the more potent secondary suppression by the 'immune' interferon produced by the virus, bacteria and malignant cells. In other words, the potential of the 'fighting couple' of the immune system, NK cell/interferon, is perhaps disturbed genetically due to the chromosome 21.
The immune response to influenza A virus is characterized by an influx of both macrophages and T lymphocytes into the lungs of the infected host, accompanied by induced expression of a number of CC chemokines. CC chemokine receptors CCR5 and CCR2 are both expressed on activated macrophages and T cells. We examined how the absence of these chemokine receptors would affect pulmonary chemokine expression and induced leukocyte recruitment by infecting CCR5-deficient mice and CCR2-deficient mice with a mouse-adapted strain of influenza A virus. CCR5−/− mice displayed increased mortality rates associated with acute, severe pneumonitis, whereas CCR2−/− mice were protected from the early pathological manifestations of influenza because of defective macrophage recruitment. This delay in macrophage accumulation in CCR2−/− mice caused a subsequent delay in T cell migration, which correlated with high pulmonary viral titers at early time points. Infected CCR5−/− mice and CCR2−/− mice both exhibited increased expression of the gene for MCP-1, the major ligand for CCR2−/− and a key regulator of induced macrophage migration. These studies illustrate the very different roles that CCR5 and CCR2 play in the macrophage response to influenza infection and demonstrate how defects in macrophage recruitment affect the normal development of the cell-mediated immune response.
Transpleural lavage of lungs from uninfected C3H mice yielded an average of 300,000 leukocytes per mouse. This number increased eightfold within 6 days after intranasal inoculation with virulent influenza A/Hong Kong/68 (H3N2) virus. Macrophages and lymphocytes in approximately equal numbers comprised 90% or more of the leukocytes both before and during infection. B, T, and null lymphocytes comprised, respectively, 9, 21, and 18% of the leukocytes before infection and 7, 26, and 5% by day 6. In absolute numbers, macrophages and T lymphocytes provided the major increments during infection. Cytotoxic activity of mononuclear cells from lung lavages was compared in a chromium release assay using syngeneic L929 target cells with the activity of mediastinal lymph nodes, spleens, and peripheral blood of uninfected and infected C3H mice. Nonspecific cytotoxicity for target cells infected with H3hkNeq1 or B/Lee influenza virus was found with mononuclear cells from uninfected mice. This activity tended to be highest with lavage leukocytes and was associated with adherent cells, presumably macrophages. Increased virus-specific cytotoxicity was detected with lavage cells by day 6 and persisted through day 9, the period of maximal pneumonia. Similar cytotoxic activity also appeared in cells from the nodes and spleen at this same time but was not detected in peripheral blood cells. The virus-specific cytotoxicity of lavage cells was due largely to a nonadherent cell possessing Fc receptors and theta antigen but lacking C3 receptors; these properties are compatible with actively cytotoxic T lymphocytes. The cytological characteristics of the infiltrating leukocytes and the cytotoxicity data suggest that the local T cell response to influenza virus infection in the lung is a major contributor to the pneumonia observed in this mouse model.
The role of alveolar macrophages in the pulmonary immune response against various antigens was studied after elimination of alveolar macrophages by intratracheal administration of liposome-encapsulated dichloromethylene diphosphanate. When the responses against T-cell-independent type 1 and type 2 antigens were compared, it was found that elimination of alveolar macrophages had no effect on T-cell-independent antigens. Intratracheal antigen administration resulted in low lung associated, local responses, although some response was observed in the spleen. In contrast, elimination of alveolar macrophages resulted in an increase in local pulmonary immune response against T-cell-dependent antigens. We conclude from these experiments that alveolar macrophages play an important role in controlling the local pulmonary immune response against T-cell-dependent antigens by down-regulation of local T-cell populations. The alveolar macrophages do not down-regulate the response against intratracheally administered T-cell-independent antigens, although they are important in the protection against inflammatory damage caused by bacterial endotoxins.
The cellularity of the mediastinal lymph nodes of mice infected intranasally with a high dose of an H3N2 influenza A virus increases massively within 5 days. All classes of lymphocytes are involved. A similar, but much smaller, expansion in cell numbers occurs after exposure to a comparable dilution of normal chick allantoic fluid. In the control group, this increase in lymph node size is totally prevented by the in vivo depletion of CD4+ T cells whereas there is only a 50% reduction in the virus-infected mice. The lymphocyte component of the cellular exudate in the lungs of infected mice is dominated by activated, CD8+ T cells, which are also prevalent in the mediastinal lymph nodes. Elimination of the CD4+ subset does not greatly diminish the severity of this inflammatory process. The CD4-depleted mice clear the virus from the lung, and there is little effect on the frequency of virus-specific, cytotoxic T lymphocyte precursors in either the lymph node or the lung. Substantial involvement of CD4+ T cells is not essential for the development of effective cell-mediated immunity in mice with influenza.
This chapter reviews recent work on the best-characterized interferon (IFN)-induced proteins. The focus is on IFN-induced proteins with assigned functions—namely, protein kinase P1, 2-5A synthetase, mouse and human Mx proteins, indolamine 2,3-dioxygenase, and a few other IFN-induced proteins. The Mx proteins are discussed in greatest detail, because the Mx system is under investigation in the laboratory. The chapter mentions that individual IFN-induced proteins have distinct biochemical activities that lead to discrete physiological changes in IFN-treated cells. For example, the IFN-induced protein kinase P1 can inhibit the multiplication of many different viruses by reducing the translation rates of viral mRNAs. In contrast, the antiviral activities of 2-5A synthetases and Mx proteins show a high degree of specificity for particular classes of viruses. It discusses recent work on the molecular mechanisms of IFN action toward many DNA and RNA viruses.
Activation of the interferon (IFN) system is an early defence mechanism against viral infections. The virus stimulates production of IFN by nucleated cells including the peripheral blood mononuclear cells (PBMC), and this IFN in turn activates several IFN-dependent immune mechanisms including the induction of an anti-viral state in cells, which prevents or retards further intracellular viral replication. In an ongoing study of 1,500 individuals of all ages and with various illnesses, we found 15 cases (representing 5% of patients with acute viral disease) in whom the IFN system response during an acute viral illness was absent or grossly deficient. There was no detectable IFN in the blood, PBMC did not produce IFN-alpha and IFN-gamma or produced minimal amounts of one of them in vitro following appropriate stimulation, and the patients' PBMC were not in an anti-viral state. These patients had severe progressive or fulminant viral disease, often ending fatally. IFN therapy appears to be beneficial in these cases, as it rapidly induced a cellular antiviral state in most cases, stimulated in vitro IFN-alpha and IFN-gamma production by PBMC, and led to rapid recovery in seven of the nine patients who received treatment for at least 3 days. In our opinion IFN replacement therapy should be commenced as early as possible in such cases, and before irreversible cell and organ damage occur.
To explore a possible correlation between susceptibility to Toxoplasma and interferon (IFN)-generating capacity in mice, we compared the levels of serum IFN induced by stimulation with Toxoplasma lysate antigen (TLA) in different strains of Toxoplasma-infected and uninfected mice. Injection of TLA into five strains of mice with chronic Toxoplasma infection resulted in the release of considerable amounts of IFN into the circulation. Most of these IFN activities were acid labile and not neutralized by sheep antiserum against mouse IFN-alpha/beta, indicating that IFN-gamma was the dominant form produced in this system. In contrast, the majority of IFN induced in uninfected mice was characterized as IFN-alpha/beta by their acid stability and antigenicity. The response of IFN production in Toxoplasma-infected and uninfected mice varied quantitatively depending on the mouse strains examined. C57BL/6 mice were found to be the best producers of both IFN-alpha/beta and IFN-gamma, while BALB/c mice were consistently poor producers of both IFN populations. A/J, DBA/2, and C3H/He mice could be roughly classified as intermediate producers of both IFN populations. C57BL/6 and C3H/He mice showed a significant prolongation of mean survival time following primary or secondary infection with Toxoplasma compared to that of BALB/c mice. However, there was no direct correlation between the susceptibility to Toxoplasma and the levels of serum IFN.
The interferon-regulated mouse Mx gene encodes the 72-kilodalton nuclear Mx protein that selectively inhibits influenza virus replication. Mice carrying Mx+ alleles synthesize Mx protein and resist influenza virus infection, whereas mice homozygous for Mx- alleles fail to synthesize Mx protein and, as a consequence, are influenza virus susceptible. Southern blot analysis allowed us to define the following three distinct Mx restriction fragment length polymorphism (RFLP) types among classical inbred strains: RFLP type 1 in the Mx+ strains A2G and SL/NiA, RFLP type 2 in BALB/c and 33 other Mx- strains, and RFLP type 3 in CBA/J and 2 other Mx- strains. cDNA clones of Mx mRNAs from BALB/c and CBA/J cells were isolated, and their sequences were compared with that of the wild-type Mx mRNA of strain A2G. Mx mRNA of BALB/c mice has 424 nucleotides absent from the coding region, resulting in a frame shift and premature termination of Mx protein. The missing sequences correspond exactly to Mx exons 9 through 11. These three exons, together with some flanking intron sequences, are deleted from the genomes of all Mx RFLP type 2 strains. The Mx- phenotype of the Mx RFLP type 3 strain CBA/J is due to a point mutation that converts the lysine codon in position 389 to a termination codon. Mx RFLP type 3 strains have an extra HindIII site which maps to an intron and thus probably does not affect the coding capacity of Mx mRNA. We further show that the Mx mRNA levels in interferon-treated BALB/c and CBA/J cells are about 15-fold lower than in similarly treated Mx+ cells. This is probably due to decreased metabolic stabilities of the mutant mRNAs.
To assess genetic and environmental influences on adult mortality, we followed 960 families that included children born during the period 1924 through 1926 who were placed early in life with adoptive parents unrelated to them. We evaluated the risks of dying from all causes or from specific groups of causes between the ages of 16 and 58 years for adoptees with a biologic or adoptive parent who died of the same cause before the age of either 50 or 70. We compared these risks with the adoptees' risk of dying from the same causes between the ages of 16 and 58 when either the biologic or adoptive parents were still alive at the ages of 50 and 70. The death of a biologic parent before the age of 50 resulted in relative risks of death in the adoptees of 1.71 (95 percent confidence interval, 1.14 to 2.57) for all causes, 1.98 (1.25 to 3.12) for natural causes, 5.81 (2.47 to 13.7) for infections, 4.52 (1.32 to 15.4) for cardiovascular and cerebrovascular causes, and 1.19 (0.16 to 8.99) for cancers. The death of an adoptive parent resulted in relative risks of death in the adoptees that were close to unity for all causes, natural causes, and infections, 3.02 (0.72 to 12.8) for vascular causes, and 5.16 (1.20 to 22.2) for cancers. A similar but weaker pattern was observed when either a biologic or adoptive parent died before the age of 70. We conclude that premature death in adults has a strong genetic background--especially death due to infections and vascular causes.(ABSTRACT TRUNCATED AT 250 WORDS)
The role of natural killer (NK) cells in host defenses against influenza virus infections in the lung was investigated by using rabbit antiserum to asialo GM1 (RAGM1), a neutral glycosphingolipid expressed on the plasma membrane of NK cells and some mouse pulmonary macrophages. Intravenous or intratracheal (i.t.) administration of RAGM1 resulted in depletion of the (in vitro) NK activity in lung and spleen or lung alone, respectively. The NK activity was depleted as early as 12 hr post-inoculation of antiserum, but returned to the normal range of activity by 4 days after antibody administration. RAGM1 serum treatment had no effect on the cytotoxic macrophage activity expressed by the plastic-adherent mononuclear cell populations isolated from mouse or hamster lung. Treatment of mice or hamsters with an i.t. or i.v. inoculation of RAGM1 rendered both species of laboratory animals susceptible to increased morbidity and mortality during a pulmonary influenza infection. These data support the hypothesis that a population of NK cells exist in an extravascular compartment within the lung, and that this local population of NK cells in the lung is crucial to the early natural pulmonary defenses during influenza infection.
Infection of ferrets with influenza viruses resulted in the production of large numbers of antibody molecules of low avidity. With the passage of time the number of antibody molecules decreased while the average avidity increased. Sequential infection of ferrets with serologically related viruses caused a marked increase in the number of antibody molecules reacting with the first virus. The avidity of this antibody was similar to that of the antibody before reinfection. The antibody reacting with the second virus was of secondary quality. The antibody population 18 to 21 days after secondary infection with a related virus was heterogeneous in terms of avidity, some of the antibodies reacting with either one or the other of the infecting viruses and some reacting with both viruses.
When primary immunity is boosted not by the homologous but by a crossreacting vaccine, the newly formed antibodies react better with the primary antigen than with the antigen actually eliciting the response. This phenomenon bears the name of Original Antigenic Sin (1). It is shown that the number of antibody molecules produced against the original and the vaccinating antigen is the same; that each of these molecules is capable of reacting with both antigens; that the activity of an antiserum can be completely absorbed with either antigen; that both residual and adsorbed-dissociated fractions of antibody exhibit the same relative affinities towards the two antigens as did the native serum; that, unlike standard primary and secondary responses, the population of antibody molecules characterizing the Original Antigenic Sin is homogeneous; that each molecule has a lower equilibrium constant (i.e. higher avidity) against the original antigen than against the antigen stimulating the present response; and that all equilibrium constants are typical of secondary antibody. It is concluded that the Original Antigenic Sin is a partial anamnestic response, a related antigen stimulating that sector only of the originally primed cells which is destined to produce cross-reacting antibody. A hypothesis is developed according to which the basic difference between primary and secondary reactivity rests on the presence of a trapping mechanism that allows anamnestic production of antibody against lower doses of the homologous antigen. Such a mechanism is capable of cross-trapping related antigens, thus preventing a standard primary response and allowing manifestations of Original Antigenic Sin.
Experiments in rabbits were designed to test the two unproven assumptions of the hypothesis proposed in the companion paper (1): that Original Antigenic Sin is fundamentally a restricted anamnestic response, and that there exists a trapping mechanism capable of deflecting antigen from one kind of cell and guiding it to another. It is shown that whole-body X-irradiation, sufficient to abolish primary but not secondary production of antibodies, leaves all manifestations of the Original Antigenic Sin untouched. This proves the first assumption. Primary immune animals challenged with very large doses of a related antigen produce an immediate response of cross-reactive antibodies, followed by a standard primary response to the challenging antigen. When boosted with an appropriate mixture of both antigens, the response is of standard secondary type to the homologous antigen, followed by a standard primary response to the crossreacting antigen. When animals are primarily vaccinated with a mixture of two related antigens, small booster doses of either will stimulate a standard secondary response only. When such animals are given very large booster doses of either antigen, the response is a compound of a homologous secondary and of an Original Antigenic Sin-type against the related antigen. Each of these findings demonstrates a corollary of the second assumption. The results are discussed in terms of the limitations they impose on theories concerned with the production of antibodies.
Studies were conducted comparing interferon production of various mouse strains. Methods used included the production of interferon in vivo and in vitro using spleen cell cultures. Strain differences observed in vivo were generally consistent with the results obtained using cell culture methods. In general, high-producing strains in vivo were also high producers using in vitro methods. Strain differences in vivo were greatest using BCG with old Tuberculin (OT) as a challenge. In general, BDF1 and C57BL/6J mice were high producers while BALB/cByJ and NZB/BLNJ were consistently low responders to both type I and type II interferon inducers. C3H/He and HA/ICR mice could be classified as intermediate interferon producers.
During interferon induction in mice in vivo with various strains of influenza A virus differences in titer of produced interferon were observed. Correlation between interferon titer and neuraminidase activity of a given influenza virus strain was noted. Similar correlation was demonstrated with virus fraction purified chromatographically and used for interferon induction. The fractions with high neuraminidase activity were good interferon inducers, whereas the fractions with undeterminable neuraminidase activity did not induce interferon in vivo.
Lung fluids and leukocytes were obtained from unprimed C3H mice by transpleural lavage at intervals after infection with influenza A/Hong Kong/68 virus and were tested for interferon activity. Lavage fluid interferon titers correlated directly with lung virus titers and with initial increases in leukocyte yields from infected lungs. In contrast to cultured lymph node cells from infected animals or leukocytes from lungs of uninfected mice, washed leukocytes obtained from the lungs of mice infected 2 to 6 days earlier produced interferon spontaneously in culture. The physiochemical, biological, and antigenic properties of both the interferon in lavage fluids and that produced by lung lavage leukocytes were similar and characteristics of alpha interferon. Fractionation studies indicated that macrophages and T lymphocytes were primarily responsible for the interferon produced in culture. The early presence and significant numbers of interferon-producing leukocytes in infected lungs suggests that these cells have an early role in defense against influenza virus infection.
Natural killer (NK) and natural cytotoxic (NC) cells can be recovered from the spleens of mice. NK/NC cells are thought to serve as a first line of defense (before the development of immune responses) against tumor and virus infected cells; therefore organs such as the lung that are exposed to the environment may harbor NK/NC cells. Studies reported in this manuscript characterize a population of pulmonary cells (recovered from collagenase-treated lungs) that exhibited cytotoxic activity against 51Cr-labeled tumor targets in vitro. As with the spleen cell populations, the mononuclear cells from the lung lysed the NK-sensitive target YAC-1 as well as the NC-sensitive WEHI 164.1 tumor cells in vitro. By using flow cytometry, it was observed that 15 to 20% of nylon wool-passed (NWP) lung cells and 5 to 15% of NWP spleen cells from C57BL/6 mice could bind antibody for NK cell alloantigens (NK 1.2, defined by (CE X NZB)F1 anti-CBA sera). Treatment of lung and spleen cell populations with complement and antisera to NK 1.2, asialo GM1, and Ly-5 but not Thy-1 antigens significantly decreased lung and splenic NK (YAC-1) activity. Forty-eight hours after infection of mice by intratracheal inoculation of an infectious dose of influenza virus (PR/8/34) NK activity was stimulated in the lung and not the spleen. Therefore although NK cells in the lung and spleen are similar in antigenic phenotype and target preference there appears to be a pulmonary compartment of natural resistance cells the function of which can be modulated locally. These data are consistent with the hypothesis that the lung contains a separate compartment for NK/NC cells that may participate in the defense mechanisms of the lung.
An ongoing surveillance program was intensified to determine whether an increased risk of acquiring vaccine-related Guillain-Barré syndrome (GBS) (similar to that observed after vaccination with the A/New Jersey swine-influenza vaccine in 1976) existed for the approximately 12.5 million adults (greater than or equal to 18 years old) vaccinated in the 1978-1979 influenza campaign. In the contiguous United States (excluding Maryland) 544 cases of GBS with onset between September 1, 1978, and March 31, 1979, were reported, including 12 adults who had been vaccinated within eight weeks before the onset of GBS and 393 who had not. The relative risk of vaccine-associated GBS for adults reported in this surveillance was 1.4 (95% confidence limits, 0.7 to 2.7)--significantly below the risk (6.2) associated with A/New Jersey vaccine for the equivalent eight-week period. In contrast to the A/New Jersey vaccine, the 1978-1979 influenza vaccine was not associated with a statistically significant excess risk of GBS.
Cells which are cytotoxic for both virus-infected and uninfected target cells can be recovered from the spleens of mice injected with either infectious or non-infectious influenza A virus. Peak activity doccurs at 1-2 days and decreases to low levels by day 6. The effector cells are insensitive to anti-Thy 1 antibody and complement treatment, are not H-2 restricted, do not adhere to plastic and are unaffected by silica or carrageenan. in this sense and in the pattern of susceptibility to lysis of a variety of cultured cell lines, these effector cells have the properties of natural killer (NK) cells and are referred to as such. They are present to an increased level of activity in nude (nu+/nu+) mice and to a low level of activity in beige (bg+/bg+) mice, but upon injection of virus there is a significant increase in activity in both hosts. Such cells were also recovered from the lungs of mice infected intranasally with a lethal or sublethal dose of virus. In the former case, maximum activity was reached 2 days post infection and the activity remained high until death; in the latter case, peak activity was reached 4 days after virus inoculation and by day 11 the activity had decreased to pre-infection levels. After intranasal inoculation of influenza virus, both beige mice and their heterozygous littermates contained similar levels of infectious virus in their lungs. However, this result does not eliminate the possibility that these cells may help to limit virus infection.
Human influenza is primarily an infection of the upper respiratory tract and central airways. The interferon (IFN) system appears to have a role in limiting viral spread and initiating recovery before the development of T-cell and B-cell responses in primary infection. All cellular responses to IFNs result from interaction with cell surface receptors that trigger the expression of a number of cellular genes. Among the IFN-inducible gene products, the Mx proteins have attracted much attention because they have potential activity against influenza virus and possibly against other viruses. Mx proteins are guanosine triphosphate (GTP)-binding proteins with intrinsic GTPase activity. They seem to act indirectly against viruses by modifying cellular functions needed along the viral replication pathway. In mice the Mx1 protein has been shown to be necessary and sufficient to protect against influenza virus infection because the resistance does not require a functioning immune system. In humans the MxA protein has antiviral activities against influenza viruses. The MxA protein is encoded on the distal part of the long arm of chromosome 21 together with several other proteins implicated in the IFN system. Patients with Down's syndrome (trisomy 21) have an increased expression of MxA protein, and their cells display an increased sensitivity to IFNs in vitro because of gene dosage effects. These patients, however, are more susceptible to upper respiratory infection than normal individuals. This susceptibility has been related to deficiencies in the immune system. Therefore, induction of MxA in man does not sem sufficient to prevent influenza spreading, and, in contrast to the murine Mx system, a functioning immune system is necessary for protection.
Macrophage inflammatory protein-1 alpha (MIP-1 alpha) is a chemokine that has pro-inflammatory and stem cell inhibitory activities
in vitro. Its biologic role in vivo was examined in mice in which the gene encoding MIP-1 alpha had been disrupted. Homozygous
MIP-1 alpha mutant (-/-) mice were resistant to Coxsackievirus-induced myocarditis seen in infected wild-type (+/+) mice.
Influenza virus-infected -/- mice had reduced pneumonitis and delayed clearance of the virus compared with infected +/+ mice.
The -/- mice had no overt hematopoietic abnormalities. These results demonstrate that MIP-1 alpha is an important mediator
of virus-induced inflammation in vivo.
To characterize behavioral and physiological alterations induced by viral respiratory infection, C57BL/6 and BALB/c strains of mice were monitored for 2 days before and 4 days after intranasal inoculation with influenza virus. Both strains developed hypothermia, decrease locomotor activity, and decreased delta-wave amplitude during sleep within 24 h after inoculation. However, infected C57BL/6 mice also spent more time in slow-wave sleep, but infected BALB/c mice did not. The increased SWS in C57BL/6 mice occurred during the lights-off phase of the circadian cycle, and resulted in loss of the normal circadian rhythmicity of sleep. Increased sleep also occurred after viral challenge of immunized C57BL/6 mice, but was not observed after secondary challenge of immunized BALB/c mice. These data indicate that sleep alterations may accompany viral infections in some, but not all, strains of mice. The dissimilar sleep patterns seen in C57BL/6 and BALB/c mice after influenza infection may reflect differences in their immune response to influenza virus.
The antibody response to influenza vaccination has been variably reported to be decreased in elderly individuals. To determine the effect of ageing alone on this antibody response, a group of carefully-screened healthy elderly subjects were compared with young adult controls. Antibody titres for several strains of influenza were measured before and after vaccination with whole-virus (WVV) and split-virus influenza vaccines (SVV) in two successive years. In general, the antibody response to WVV was greater than the response to SVV. Both groups showed a similar response to the H3N2 strain but the elderly group showed a lower response to the H1N1 and B strains of virus contained in the vaccine. Antibodies to older strains of influenza A but not B were stimulated by vaccination with SVV. In the elderly group, the response to older viral strains was relatively increased compared with newer strains. In contrast, the young control group had better antibody responses to the newer than to the older strains of influenza tested. Reductions in the antibody response to influenza vaccination may, therefore, be related to the phenomenon of original antigenic sin and the cohort effect of exposure to H1N1 during childhood in the elderly group studied. The increased immunogenicity of WVV must be considered in light of the current wide use of SVV in the elderly.
2,5AS is induced by interferon-alpha, -beta (IFN-alpha, -beta) and polymerizes adenosine triphosphate (ATP) into pppA (2'p5'A) oligomers, leading to inhibition of protein synthesis and virus growth. The gene coding for the IFN-alpha, -beta receptor is localized to chromosome 21. In trisomy 21 cells from patients with Down's syndrome a 50% increase in gene dosage is present for the genes on this chromosome. Corresponding increase of gene products has been shown for several of these genes, e.g. the IFN-alpha, -beta receptor molecules. Here, we show a direct proportionality between the number of IFN-alpha, -beta receptors and both the basal activity of 2,5AS and the sensitivity of this enzyme for IFN-alpha, -beta. The relative increase of 2,5AS activity (the reactivity) becomes reduced consistent with the increased basal 2,5AS activity in trisomy 21 cells compared with control cells.
Healthy seropositive adults aged <40 (n = 15), 40–64 (n = 15), and ⩾65 (n = 17) years were parenterally immunized with trivalent subvirion influenza virus vaccine, and their cellular and humoral
immune responses were compared. Vaccination resulted in a significant enhancement of class I human leukocyte antigen-restricted
influenza A cross-reactive cytotoxic T lymphocyte (CTL) memory. Elderly subjects had significantly lower baseline and peak
postvaccination mean percentages of specific lysis of influenza A virus-infected autologous targets but nonetheless mounted
CTL responses to vaccine that were comparable in magnitude to those of younger adults. Serologic responses and nasal IgG responses
to each of 3 vaccine strains were reduced in magnitude and frequency with advancing age. Parenteral immunization was ineffective
at inducing nasal wash IgA antibodies. Between 2 and 12 weeks after vaccination, serum and nasal antibody titers decreased
modestly, although the rate of decline was comparable between age groups. The ability of elderly adults to mount CTL responses
after influenza vaccination suggests that T cell effector mechanisms may be an important determinant of vaccine-induced protection
against serious illness in this age group.
The gene coding for the alpha, beta-interferon (alpha, beta-IFN) receptor is localized to chromosome 21. Cells from patients with Down's syndrome contain an extra chromosome 21, and thereby an expected 1.5-times increase in the number of genes located to this chromosome and in consequence a 1.5-times increase in cell surface alpha-IFN receptors. Actual measurements of these by competition binding experiments with human recombinant alpha-IFN on peripheral blood mononuclear cells (PBMC) from patients with Down's syndrome resulted in a mean of 1.69, which is in accordance to the theoretical 1.50, but slightly overestimated due to the calculation method. The increased gene dosage of the alpha-IFN receptor was quantitatively verified by Southern blot-hybridizations. Further characterization of alpha-IFN receptor binding showed insignificant differences in dissociation constants among patients and healthy individuals.
Excess sleep and fever are central nervous system (CNS) facets of the acute phase response; these responses are induced by microbial products, such as muramyl peptides, via their ability to enhance cytokine production. Although peripheral macrophages are known to digest bacteria, thereby releasing muramyl peptides that, in turn, stimulate cytokine production, it was unknown whether CNS phagocytes such as microglia also had this capacity. Primary cultures of microglia were allowed to phagocytize and digest Staphylococcus aureus radiolabeled with a cell wall-specific marker. Radiolabeled low molecular weight substances released into the culture medium were partially purified and tested for the ability to induce excess sleep, fever, and cytokine production. These substances increased non-rapid eye movement sleep, electroencephalographic slow-wave activity, and brain temperature after intracerebroventricular injection into rabbits. They also induced interleukin-1, tumor necrosis factor, and the interleukin-1 receptor antagonist production in human monocytes. Results suggest that microglia perform fundamental macrophage functions and further implicate microglia as resident immunocompetent cells.
Increased slow-wave sleep accompanies influenza infection in C57BL/6 mice but not BALB/c mice. These strains of mice possess different alleles of the genetic lucus If-1, which codes for high (If-1h; C57BL/6) and low (If-1(1); BALB/c) production of interferon (IFN), a putative sleep-inducing cytokine. To evaluate the contribution of the If-1 gene to differences in murine sleep propensity, sleep patterns were evaluated in mice treated with the IFN inducers polyinosinic:polycytidilic acid (pIC) or Newcastle disease virus (NDV), with influenza virus, or with murine interferon (IFN-alpha) or IFN-alpha/beta. As compared with baseline values, C57BL/6 mice exhibited increased slow-wave sleep after all three challenges, but BALB/c mice did not. Congenic B6.C-H28c mice, which bear the BALB/c allele for low IFN production on the C57BL/6 genetic background, showed enhanced slow-wave sleep after influenza infection but not after NDV. Exogenous IFN did not enhance slow-wave sleep in either C57BL/6 or BALB/c mice. These data suggest that the If-1 allele may influence the somnogenic responsiveness of mice under some conditions but that additional mechanisms may contribute to sleep enhancement during infectious disease.