[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) is a leading pediatric pathogen that is responsible for a majority of infant hospitalizations due to viral disease. Despite its clinical importance, no vaccine prophylaxis against RSV disease or effective antiviral therapeutic is available. In this study, we established a robust high-throughput drug screening protocol by using a recombinant RSV reporter virus to expand the pool of RSV inhibitor candidates. Mechanistic characterization revealed that a potent newly identified inhibitor class blocks viral entry through specific targeting of the RSV fusion (F) protein. Resistance against this class was induced and revealed overlapping hotspots with diverse, previously identified RSV entry blockers at different stages of preclinical and clinical development. A structural and biochemical assessment of the mechanism of unique, broad RSV cross-resistance against structurally distinct entry inhibitors demonstrated that individual escape hotspots are located in immediate physical proximity in the metastable conformation of RSV F and that the resistance mutations lower the barrier for prefusion F triggering, resulting in an accelerated RSV entry kinetics. One resistant RSV recombinant remained fully pathogenic in a mouse model of RSV infection. By identifying molecular determinants governing the RSV entry machinery, this study spotlights a molecular mechanism of broad RSV resistance against entry inhibition that may affect the impact of diverse viral entry inhibitors presently considered for clinical use and outlines a proactive design for future RSV drug discovery campaigns.
Proceedings of the National Academy of Sciences of the United States of America. 08/2014;
[Show abstract][Hide abstract] ABSTRACT: Immune-mediated lung injury is a hallmark of RSV lower respiratory tract illness. STAT4 plays a critical role in CD4+ Th1 lineage differentiation and IFN-γ protein expression by CD4+ T cells. As CD4+ Th1 differentiation is associated with negative regulation of CD4+ Th2 and Th17 differentiation, we hypothesized that RSV infection of STAT4(-/-) mice would result in enhanced lung Th2 and Th17 inflammation and impaired lung Th1 inflammation compared to WT mice. We performed primary and secondary RSV challenge in WT and STAT4(-/-) mice, and used STAT1(-/-) mice as a primary challenge positive control for the development of RSV-specific lung Th2 and Th17 inflammation. Primary RSV challenge of STAT4(-/-) mice resulted in decreased T-bet and IFN-γ expression in CD4+ T cells compared to WT mice. Lung Th2 and Th17 inflammation did not develop in primary RSV-challenged STAT4(-/-) mice. Decreased IFN-γ expression by NK cells, CD4+ T cells, and CD8+ T cells was associated with attenuated weight loss and enhanced viral clearance with primary challenge in STAT4(-/-) mice compared to WT mice. Following secondary challenge, WT and STAT4(-/-) mice also did not develop lung Th2 or Th17 inflammation. In contrast to primary challenge, secondary RSV challenge of STAT4(-/-) mice resulted in enhanced weight loss, increased lung IFN-γ expression, and an increased lung RSV-specific CD8+ T cell response compared to WT mice. These data demonstrate that STAT4 regulates the RSV-specific CD8+ T cell response to secondary infection, but does not independently regulate lung Th2 or Th17 immune responses to RSV challenge.
[Show abstract][Hide abstract] ABSTRACT: The Th17 cytokines IL-17A, IL-17F, and IL-22 are critical for the lung immune response to a variety of bacterial pathogens including Klebsiella pneumoniae (KP). Th2 cytokine expression in the airways is a characteristic feature of asthma and allergic airway inflammation. The Th2 cytokines IL-4 and IL-13 diminish ex vivo and in vivo IL-17A expression by Th17 cells. To determine the effect of IL-4 and IL-13 on IL-17-dependent lung immune responses to acute bacterial infection, we developed a combined model in which allergic airway inflammation and lung IL-4 and IL-13 expression were induced by ovalbumin sensitization and challenge prior to acute lung infection with KP. We hypothesized that pre-existing allergic airway inflammation decreases lung IL-17A expression and airway neutrophil recruitment in response to acute KP infection and thereby increases lung KP burden. As hypothesized, we found that allergic airway inflammation decreased KP-induced airway neutrophils and lung IL-17A, IL-17F, and IL-22 expression. Despite the marked reduction in post-infection airway neutrophilia and lung expression of Th17 cytokines, allergic airway inflammation significantly decreased lung KP burden and post-infection mortality. We showed that decreased lung KP burden was independent of IL-4, IL-5, and IL-17A, and partially-dependent on IL-13 and STAT6. Additionally, we demonstrated that decreased lung KP burden associated with allergic airway inflammation was both neutrophil and CCL8-dependent. These findings suggest a novel role for CCL8 in lung antibacterial immunity against KP and suggest new methods of orchestrating lung antibacterial immunity.
Infection and immunity 06/2014; · 4.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Maternal immunization of mice with formalin inactivated respiratory syncytial virus (FI-RSV) resulted in the passive transfer of RSV antibodies but not cellular components to the offspring. The offspring born to FI-RSV immunized mothers showed serum RSV neutralizing activity, effectively controlled lung viral loads without vaccine-enhanced disease, did not induce pulmonary eosinophilia, and cytokine producing cells after live RSV infection. Therefore, this study provides evidence that maternal immunization provides an in vivo model in investigating the roles of antibodies independent of cellular components.
[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. In the present study, we investigated the effect of prophylactic treatment with the intact and F(ab’)2 forms of an anti-G protein monoclonal antibody (mAb), 131-2G, on the humoral and cellular adaptive immune response to RSV rA2-line19F (r19F) challenge in BALB/c mice. The F(ab’)2 form of 131-2G does not decrease virus replication but intact 131-2G does. The serum specimens for antibodies and spleen cells for memory T cell responses to RSV antigens were analyzed at 30, 45, 75 and 95 p.i. with/without prior treatment with 131-2G. The ratios of Th2/Th1 antibody isotypes at each time p.i indicated that both forms of mAb 131-2G shifted the subclass response from a Th2 (IgG1 and IgG2b) to a Th1 (IgG2A) bias. The ratio of IgG1/IgG2A antibody titer was 3-fold to 10-fold higher for untreated than mAb treated mice. There was also some increase in IgG (22%±13 increase) and neutralization (32% increase) in antibodies with mAb 131-2G prophylaxis at 75 days p.i. Treatment with 131-2G significantly (p≤0.001) decreased the percent of IL-4 positive CD4 and CD8 in RSV stimulated spleen cells at all times p.i. while percent of IFN-γ T cells significantly (p≤0.001) increased ≥75 days p.i. The shift from a Th2 to a Th1 biased T cell response in treated compared to untreated mice likely was directed by the much higher levels of T-box transcription factor (Tbet) (≥45% vs <10%) in CD4 and CD8 T cells and lower levels of Gata-3 (≤2% vs ≥6%) in CD4 T cells in peptide stimulated, day 75 p.i. spleen cells. These data show that the RSV G protein affects both humoral and cellular adaptive immune responses and induction of 131-2G-like antibodies might improve the safety and long term efficacy of an RSV vaccine.
[Show abstract][Hide abstract] ABSTRACT: RNA viruses are capable of rapid spread and severe or potentially lethal disease in both animals and humans. The development of reverse genetics systems for manipulation and study of RNA virus genomes has provided platforms for designing and optimizing viral mutants for vaccine development. Here, we review the impact of RNA virus reverse genetics systems on past and current efforts to design effective and safe viral therapeutics and vaccines.
[Show abstract][Hide abstract] ABSTRACT: Background
The prevalence of allergic diseases has doubled in developed countries in the past several decades. Cyclooxygenase (COX)-inhibiting drugs augmented allergic diseases in mice by increasing allergic sensitization and memory immune responses. However, whether COX inhibition can promote allergic airway diseases by inhibiting immune tolerance is not known.
To determine the role of the COX pathway and prostaglandin I2 (PGI2) signaling through the PGI2 receptor (IP) in aeroallergen-induced immune tolerance.
Wild-type (WT) BALB/c mice and IP knockout mice were aerosolized with ovalbumin (OVA) to induce immune tolerance prior to immune sensitization with an intraperitoneal injection of OVA/alum. The COX inhibitor indomethacin or vehicle was administered in drinking water to inhibit enzyme activity during the sensitization phase. Two weeks after sensitization, the mice were challenged with OVA aerosols. Mouse bronchoalveolar lavage fluid was harvested for cell counts and TH2 cytokine measurements.
WT mice treated with indomethacin had greater numbers of total cells, eosinophils, and lymphocytes, and increased IL-5 and IL-13 protein expression in BAL fluid compared to vehicle-treated mice. Similarly, IP knockout mice had augmented inflammation and TH2 cytokine responses compared to WT mice. In contrast, the PGI2 analog cicaprost attenuated the anti-tolerance effect of COX inhibition.
COX inhibition abrogated immune tolerance by suppressing PGI2 IP signaling, suggesting that PGI2 signaling promotes immune tolerance and that clinical use of COX-inhibiting drugs may increase the risk of developing allergic diseases.
Journal of Allergy and Clinical Immunology. 01/2014;
[Show abstract][Hide abstract] ABSTRACT: Immunization of mice with a mixed vaccine (FdFG VLP) of virus-like nanoparticles (VLPs) containing respiratory syncytial virus (RSV) F and G glycoproteins and plasmid DNA encoding RSV F induced IgG2a antibodies dominantly specific for RSV F. After RSV challenge, FdFG VLP immunized mice controlled lung viral loads as well as showed higher levels of CD8 + T cells producing interferon-gamma and did not cause eosinophilia and pulmonary inflammatory disease compared to formalin-inactivated RSV immunized mice.
Nanomedicine: Nanotechnology, Biology and Medicine. 01/2014;
[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection (LRI) and viral death in infants. RSV disease in infants is characterized by epithelial desquamation, neutrophilic bronchiolitis and pneumonia and obstructive pulmonary mucus. Human rhinoviruses (HRVs) are by far the most common cause of symptomatic upper respiratory tract infection (URI) in people and are more recently appreciated as a significant cause of LRI. RSV and HRV are also implicated in asthma pathogenesis. Within both RSV and HRV, viral genetic differences play a role in disease severity and/or prevalence in patient populations, and viral genetic differences affect pathogenesis. Here, we review data on how viral genetic differences impact disease using RSV and HRV as examples, including effects on the host immune response. Virus genotype–phenotype relationships can be exploited in the laboratory to gain insight into mechanisms by which respiratory viruses modulate host immune responses and cause disease.
Current opinion in immunology 12/2013; 25(6):761-8. · 10.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) causes significant morbidity and mortality in children and the elderly. No vaccines for RSV are in use. Because of immunosenescence, the immunologic requirements for a successful RSV vaccine in the elderly might differ from a RSV vaccine for young children. Using an aged mouse model of RSV pathogenesis, we found that aged mice had impaired Ag-specific CD8(+) T cell responses and delayed RSV clearance compared with young mice. To study vaccine-elicited RSV-specific CD8(+) T cells in aged mice, we used a peptide vaccine approach. TriVax is a commixture of a peptide representing immunodominant RSV CD8(+) T cell epitope M282-90, a TLR agonist (polyinosinic-polycytidylic acid), and a costimulatory anti-CD40 Ab. TriVax vaccination generated robust, polyfunctional, and protective CD8(+) T cell responses in young BALB/c mice, but not in 18-mo-old (aged) BALB/c mice. We hypothesized that treatment of aged mice with agonistic anti-CD137 (41BB) mAb will partially restore T cell responses and TriVax efficacy in aged mice. We immunized 18-mo-old BALB/c mice twice with TriVax + anti-41BB mAb or TriVax + isotype control Ab. Coadministration of anti-41BB mAb with TriVax enhanced RSV-specific CD8(+) T cell responses and TriVax efficacy in challenge experiments. Triggering the 41BB costimulatory pathway may be a strategy for enhancing T cell responses to vaccines in the elderly.
The Journal of Immunology 11/2013; · 5.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Confronted with an increasing number of emerging and re-emerging viral pathogens, the identification of novel pathogen-specific and broad-spectrum antivirals has become a major developmental objective. Targeting host factors required for virus replication presents a tangible approach towards novel hits with broadened indication range. However, the identification of developable host-directed antiviral candidates remains challenging. We describe a novel screening protocol that interrogates the myxovirus host-pathogen interactome for broad-spectrum drug candidates and simultaneously probes for conventional, pathogen-directed hits. With resource-efficiency and pan-myxovirus activity as the central developmental parameters, we explored co-screening against two distinct, independently traceable myxoviruses in a single-well setting. Having identified a pair of unrelated pathogenic myxoviruses (influenza A virus and measles virus) with comparable replication kinetics, we observed unimpaired co-replication of both viruses, generated suitable firefly and renilla luciferase reporter constructs, respectively, and validated the protocol up to 384-well plate format. Combined with an independent counterscreen using a recombinant respiratory syncytial virus luciferase reporter, implementation of the protocol identified candidates with broadened anti-myxovirus profile in addition to pathogen-specific hits. Mechanistic characterization revealed a newly discovered broad-spectrum lead that does not block viral entry, but stimulates effector pathways of the innate cellular antiviral response. In summary, we provide proof-of-concept for the efficient discovery of broad-spectrum myxovirus inhibitors in parallel to para- and orthomyxovirus-specific hit candidates in a single screening campaign. The newly identified compound provides a basis for the development of a novel broad-spectrum small-molecule antiviral class.
[Show abstract][Hide abstract] ABSTRACT: The human respiratory syncytial virus (HRSV) fusion (F) protein cytoplasmic tail (CT) and matrix (M) protein are key mediators of viral assembly but the underlying mechanisms are poorly understood. A complementation assay was developed to systematically examine the role of the F protein CT in infectious virus production. The ability of F mutants with alanine substitutions in the CT to complement an Fnull virus in generating infectious progeny was quantitated by flow cytometry. Two CT regions with impact on infectious progeny production were identified: residues 557-566 (CT-R1) and 569-572 (CT-R2). Substitutions in CT-R1 decreased infectivity by 40-85% and increased the level of F-induced cell-cell fusion, but had little impact on assembly of viral surface filaments, which are believed to be virions. Substitutions in CT-R2, as well as deletion of the entire CT, abrogated infectious progeny production and impaired viral filament formation. However, CT-R2 mutations did not block but rather delayed the formation of viral filaments, which continued to form at a low rate and contained the viral M and nucleoprotein (N). Microscopy analysis revealed that substitutions in CT-R2, but not CT-R1, led to accumulation of M and F proteins within and at the perimeter of viral inclusion bodies (IB) respectively. The accumulation of M and F at IBs and coincident strong decrease in filament formation and infectivity upon CT-R2 mutations suggest that F interaction with IBs is an important step in the virion assembly process and that CT residues 569-572 act to facilitate release of M-ribonucleoprotein complexes from IBs.
[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) belongs to the family Paramyxoviridae and is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. Increased airway resistance and increased airway mucin production are two manifestations of RSV infection in children. RSV rA2-line19F infection induces pulmonary mucous production and increased breathing effort in BALB/c mice and provides a way to assess these manifestations of RSV disease in an animal model. In the present study, we investigated the effect of prophylactic treatment with the F(ab')2 form of the anti-G protein monoclonal antibody (mAb), 131-2G, on disease in RSV rA2-line19F challenged mice. F(ab')2 131-2G does not affect virus replication. It, and the intact form that does decrease virus replication, prevented increased breathing effort and airway mucin production, as well as weight loss, pulmonary inflammatory cell infiltration, pulmonary substance P levels, and pulmonary Th2 cytokine levels that occur in mice challenged with this virus. These data suggest that the RSV G protein contributes to prominent manifestations of RSV disease, and mAb 131-2G can prevent these manifestations of RSV disease without inhibiting virus infection.
[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) is the leading cause of death due to a viral etiology in infants. RSV disease is characterized by epithelial desquamation, neutrophilic bronchiolitis and pneumonia, and obstructive pulmonary mucus. It has been shown that infection of BALB/cJ mice with RSV clinical isolate A2001/2-20 (2-20) results in greater early viral load and airway necrosis, IL-13 levels, and airway mucin expression than infection with RSV laboratory strain A2. We hypothesized that the fusion (F) protein of RSV 2-20 is a mucus-inducing viral factor. In vitro, the fusion activity of 2-20 F, but not A2 F, was enhanced by expression of RSV G. We generated a recombinant F-chimeric RSV by replacing the F gene of A2 with the F gene of 2-20. Similar to the parent 2-20 strain, infection of BALB/cJ mice with A2-2-20F resulted in greater early viral load and subsequent pulmonary mucin expression than the A2 strain. A2-2-20F infection induced greater necrotic airway damage and neutrophil infiltration than A2 infection. We hypothesized that the neutrophil response to A2-2-20F infection is involved in mucin expression. Antibody-mediated depletion of neutrophils in RSV-infected mice resulted in lower TNF-α levels, fewer IL-13-expressing CD4 T cells, and less airway mucin production in the lung. Our data are consistent with a model in which F and G functional interaction leads to enhanced fusion, and F is a key factor in airway epithelium infection, pathogenesis, and subsequent airway mucin expression.
[Show abstract][Hide abstract] ABSTRACT: Respiratory syncytial virus (RSV) causes respiratory tract infections in young children, and significant morbidity and mortality in the elderly, imunosuppressed and immunocompromised patients, and patients with chronic lung diseases. Recently, we reported the pulmonary surfactant phospholipid, palmitoyl-oleoyl-phosphatidylglycerol (POPG), inhibited RSV infection in vitro and in vivo, by blocking viral attachment to epithelial cells. Simultaneous application of POPG along with an RSV challenge to mice, markedly attenuated infection and associated inflammatory responses. Based on these findings, we expanded our studies to determine if POPG is effective for prophylaxis and post-infection treatment for RSV infection. In vitro application of POPG at concentrations of 0.2-1.0 mg/ml at 24hrs after RSV infection of HEp-2 cells, suppressed interleukin-8 production up to 80% and reduced viral plaque formation by 2-6 log units. In vivo, the turnover of POPG in mice is relatively rapid, making post-infection application impractical. Intranasal administration of POPG (0.8-3.0 mg), 45 min before RSV inoculation in mice, reduced viral infection by 1 log unit, suppressed inflammatory cell appearance in the lung, and suppressed virus elicited interferon-γ production. These findings demonstrate that POPG is effective for short-term protection of mice against subsequent RSV infection, and has potential for application in humans.
The Journal of Lipid Research 06/2013; · 4.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Reactive airway disease (RAD) is a general term for respiratory illnesses manifested by wheezing. Respiratory syncytial virus (RSV) results in wheezing, either by causing bronchiolitis or by inducing acute exacerbations of asthma. There has been a long-standing interest in whether severe RSV bronchiolitis in infancy is a risk factor for the development of asthma later in childhood. While epidemiologic studies have suggested that such a link exists, a very recent study suggests that infants with greater airways responsiveness to methacholine instead have an increased prevalence of severe RSV bronchiolitis. Increased airways responsiveness to methacholine has been implicated as a key factor for loss of lung function in asthmatic subjects, suggesting that instead of being causal, severe RSV infection may instead be a marker of a predisposing factor for asthma. In this chapter, we will explore the evidence that RSV infection leads to RAD in infants and adults, and how these different forms of RAD may be linked.
Current topics in microbiology and immunology 01/2013; 372:105-18. · 4.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe the first example of combining bacterial artificial chromosome (BAC) recombination-mediated mutagenesis with reverse genetics for a negative strand RNA virus. A BAC-based respiratory syncytial virus (RSV) rescue system was established. An important advantage of this system is that RSV antigenomic cDNA was stabilized in the BAC vector. The RSV genotype chosen was A2-line19F, a chimeric strain previously shown to recapitulate in mice key features of RSV pathogenesis. We recovered two RSV reporter viruses, one expressing the red fluorescent protein monomeric Katushka 2 (A2-K-line19F) and one expressing Renilla luciferase (A2-RL-line19F). As proof of principle, we efficiently generated a RSV gene deletion mutant (A2-line19FΔNS1/NS2) and a point mutant (A2-K-line19F-I557V) by recombination-mediated BAC mutagenesis. Together with sequence-optimized helper expression plasmids, BAC-RSV is a stable, versatile, and efficient reverse genetics platform for generation of a recombinant Pneumovirus.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Respiratory Syncytial Virus (RSV) causes significant disease in the elderly, in part, because immunosenescence impairs protective immune responses to infection in this population. Despite previous and current efforts, there is no RSV vaccine currently licensed in infants or elderly adults. Adjuvanted RSV subunit vaccines have the potential to boost waning immune responses and reduce the burden of RSV disease in the elderly population. RESULTS: We used an aged BALB/c mouse model to evaluate immune responses to RSV Fusion (F) protein in the absence and presence of an alum adjuvant. We demonstrate that aged BALB/c mice immunized with alum-adjuvanted RSV F protein had significantly reduced lung viral titers at day 4 following challenge with wild-type (wt) RSV. Serum neutralizing antibody titers measured on day 27 correlated with protection in both young and aged vaccinated mice, although the magnitude of antibody titers was lower in aged mice. Unlike young mice, in aged mice, alum-adjuvanted RSV F did not induce lung TH2-type cytokines or eosinophil infiltration compared to non-adjuvanted F protein following wt RSV challenge. CONCLUSION: Our studies demonstrate that neutralizing anti-RSV antibody titers correlate with protection in both young and aged BALB/c mice vaccinated with RSV F protein vaccines. The F + alum formulation mediated greater protection compared to the non-adjuvanted F protein in both young and aged mice. However, while alum can boost F-specific antibody responses in aged mice, it does not completely overcome the reduced ability of a senescent immune system to respond to the RSV F antigen. Thus, our data suggest that a stronger adjuvant may be required for the prevention of RSV disease in immunosenescent populations, to achieve the appropriate balance of protective neutralizing antibodies and effective TH1-type cytokine response along with minimal lung immunopathology.