[Show abstract][Hide abstract] ABSTRACT: A wide range of viruses from different virus families in different geographical areas, may cause immediate or delayed neuropathological changes and neurological manifestations in humans and animals. Infection by neurotropic viruses as well as the resulting immune response can irreversibly disrupt the complex structural and functional architecture of the central nervous system, frequently leaving the patient or affected animal with a poor or fatal prognosis. Mechanisms that govern neuropathogenesis and immunopathogenesis of viral infections are highlighted, using examples of well-studied virus infections that are associated with these alterations in different populations throughout the world. A better understanding of the molecular, epidemiological and biological characteristics of these infections and in particular of mechanisms that underlie their clinical manifestations may be expected to provide tools for the development of more effective intervention strategies and treatment regimens.
Full-text · Article · Dec 2015 · Acta Neuropathologica
[Show abstract][Hide abstract] ABSTRACT: Influenza A viruses are amongst the most challenging viruses that threaten both human and animal health. Influenza A viruses are unique in many ways. Firstly, they are unique in the diversity of host species that they infect. This includes waterfowl (the original reservoir), terrestrial and aquatic poultry, swine, humans, horses, dog, cats, whales, seals and several other mammalian species. Secondly, they are unique in their capacity to evolve and adapt, following crossing the species barrier, in order to replicate and spread to other individuals within the new species. Finally, they are unique in the frequency of inter-species transmission events that occur. Indeed, the consequences of novel influenza virus strain in an immunologically naïve population can be devastating. The problems that influenza A viruses present for human and animal health are numerous. For example, influenza A viruses in humans represent a major economic and disease burden, whilst the poultry industry has suffered colossal damage due to repeated outbreaks of highly pathogenic avian influenza viruses. This review aims to provide a comprehensive overview of influenza A viruses by shedding light on interspecies virus transmission and summarising the current knowledge regarding how influenza viruses can adapt to a new host.
[Show abstract][Hide abstract] ABSTRACT: The olfactory nerve consists mainly of olfactory receptor neurons and directly connects the nasal cavity with the central nervous system (CNS). Each olfactory receptor neuron projects a dendrite into the nasal cavity on the apical side, and on the basal side extends its axon through the cribriform plate into the olfactory bulb of the brain. Viruses that can use the olfactory nerve as a shortcut into the CNS include influenza A virus, herpesviruses, poliovirus, paramyxoviruses, vesicular stomatitis virus, rabies virus, parainfluenza virus, adenoviruses, Japanese encephalitis virus, West Nile virus, Chikungunya virus, La Crosse virus, mouse hepatitis virus, and bunyaviruses. However, mechanisms of transport via the olfactory nerve and subsequent spread through the CNS are poorly understood. Proposed mechanisms are either infection of olfactory receptor neurons themselves or diffusion through channels formed by olfactory ensheathing cells. Subsequent virus spread through the CNS could occur by multiple mechanisms, including transsynaptic transport and microfusion. Viral infection of the CNS can lead to damage from infection of nervous cells per se, from the immune response, or from a combination of both. Clinical consequences range from nervous dysfunction in the absence of histopathological changes to severe meningoencephalitis and neurodegenerative disease.
Full-text · Article · Jan 2015 · The Journal of Pathology
[Show abstract][Hide abstract] ABSTRACT: The armamentarium of antiviral drugs against influenza viruses is limited. Furthermore, influenza viruses emerge that are resistant to existing antiviral drugs like the M2 and NA inhibitors. Therefore, there is an urgent need for the development of novel classes of antiviral drugs. Here we investigated the antiviral properties of recombinant porcine surfactant protein D (RpSP-D), an innate defense molecule with lectin properties, against influenza B viruses. We have previously shown that porcine SP-D has more potent neutralizing activity against influenza A viruses than human SP-D. Here we show that RpSP-D neutralizes influenza B viruses efficiently and inhibited the binding of these viruses to epithelial cells of the human trachea.
[Show abstract][Hide abstract] ABSTRACT: Recently, A/H5N1 influenza viruses were shown to acquire airborne transmissibility between ferrets upon targeted mutagenesis and virus passage. The critical genetic changes in airborne A/Indonesia/5/05 were not yet identified. Here, five substitutions proved to be sufficient to determine this airborne transmission phenotype. Substitutions in PB1 and PB2 collectively caused enhanced transcription and virus replication. One substitution increased HA thermostability and lowered the pH of membrane fusion. Two substitutions independently changed HA binding preference from α2,3-linked to α2,6-linked sialic acid receptors. The loss of a glycosylation site in HA enhanced overall binding to receptors. The acquired substitutions emerged early during ferret passage as minor variants and became dominant rapidly. Identification of substitutions that are essential for airborne transmission of avian influenza viruses between ferrets and their associated phenotypes advances our fundamental understanding of virus transmission and will increase the value of future surveillance programs and public health risk assessments.
[Show abstract][Hide abstract] ABSTRACT: Central nervous system (CNS) disease is the most common extrarespiratory complication of influenza in humans. However, the
pathogenesis, including the route of virus entry, is largely unknown. Here we present, for the first time, evidence of influenza
virus entry into the CNS via the olfactory route in an immune-compromised infant. Since the nasal cavity is a primary site
of influenza virus replication and is directly connected to the CNS via the olfactory nerve, these results imply that influenza
virus invasion of the CNS may occur more often than previously believed.
Full-text · Article · Feb 2014 · The Journal of Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: We determined the pattern of attachment of the avian-origin H7N9 influenza viruses A/Anhui/1/2013 and A/Shanghai/1/2013 to
the respiratory tract in ferrets, macaques, mice, pigs, and guinea pigs and compared it to that in humans. The H7N9 attachment
pattern in macaques, mice, and to a lesser extent pigs and guinea pigs resembled that in humans more closely than the attachment
pattern in ferrets. This information contributes to our knowledge of the different animal models for influenza.
Full-text · Article · Jan 2014 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: Respiratory viruses that emerge in the human population may cause high morbidity and mortality, as well as concern about pandemic spread. Examples are severe acute respiratory syndrome coronavirus (SARS-CoV) and novel variants of influenza A virus, such as H5N1 and pandemic H1N1. Different animal models are used to develop therapeutic and preventive measures against such viruses, but it is not clear which are most suitable. Therefore, this review compares animal models of SARS and influenza, with an emphasis on non-human primates, ferrets and cats. Firstly, the pathology and pathogenesis of SARS and influenza are compared. Both diseases are similar in that they affect mainly the respiratory tract and cause inflammation and necrosis centred on the pulmonary alveoli and bronchioles. Important differences are the presence of multinucleated giant cells and intra-alveolar fibrosis in SARS and more fulminant necrotizing and haemorrhagic pneumonia in H5N1 influenza. Secondly, the pathology and pathogenesis of SARS and influenza in man and experimental animals are compared. Host species, host age, route of inoculation, location of sampling and timing of sampling are important to design an animal model that most closely mimics human disease. The design of appropriate animal models requires an accurate pathological description of human cases, as well as a good understanding of the effect of experimental variables on disease outcome.
Full-text · Article · Jan 2014 · Journal of comparative pathology
[Show abstract][Hide abstract] ABSTRACT: Respiratory viruses that emerge in the human population may cause high morbidity and mortality, as well as concern about pandemic spread. Examples are severe acute respiratory syndrome coronavirus (SARS-CoV) and novel variants of influenza A virus, such as H5N1 and pandemic H1N1. Different animal models are used to develop therapeutic and preventive measures against such viruses, but it is not clear which are most suitable. Therefore, this review compares animal models of SARS and influenza, with an emphasis on non-human primates, ferrets and cats. Firstly, the pathology and pathogenesis between SARS and influenza is compared. Both diseases are similar in that they affect mainly the respiratory tract and cause inflammation and necrosis centred on the pulmonary alveoli and bronchioles. Important differences are the presence of multinucleated giant cells and intra-alveolar fibrosis in SARS and more fulminant necrotizing and haemorrhagic pneumonia in H5N1 influenza. Secondly, the pathology and pathogenesis of SARS and influenza between human beings and experimental animals is compared. Host species, host age, route of inoculation, location of sampling and timing of sampling are important to design an animal model that most closely mimicshuman disease. The design of appropriate animal models requires an accurate pathological description of human cases, as well as a good understanding of the effect of experimental variables on disease outcome.
Full-text · Article · Jan 2014 · Journal of Comparative Pathology
[Show abstract][Hide abstract] ABSTRACT: The zoonotic outbreak of H7N9 subtype avian influenza virus that occurred in eastern China in the spring of 2013 resulted in 135 confirmed human cases, 44 of which were lethal. Sequencing of the viral genome revealed a number of molecular signatures associated with virulence or transmission in mammals. Here we report that, in the guinea pig model, a human isolate of novel H7N9 influenza virus, A/Anhui/1/2013 (An/13), is highly dissimilar to an H7N1 avian isolate and instead behaves similarly to a human seasonal strain in several respects. An/13 was found to have a low 50% infectious dose, grow to high titers in the upper respiratory tract, and transmit efficiently among co-caged guinea pigs. The pH of fusion of the HA and the binding of virus to fixed guinea pig tissues were also examined. The An/13 HA displayed a relatively elevated pH of fusion characteristic of many avian strains, and An/13 resembled avian viruses in terms of attachment to tissues. One important difference was seen between An/13 and both the H3N2 human and H7N1 avian viruses: when inoculated intranasally at high dose, only the An/13 virus led to productive infection of the lower respiratory tract of guinea pigs. In sum, An/13 was found to retain fusion and attachment properties of an avian influenza virus but displayed robust growth and contact transmission in the guinea pig model atypical of avian strains and indicative of mammalian adaptation.
Full-text · Article · Nov 2013 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: The hepatitis B virus (HBV), family Hepadnaviridae, is one of most relevant human pathogens. HBV origins are enigmatic, and no zoonotic reservoirs are known. Here, we screened 3,080 specimens from 54 bat species representing 11 bat families for hepadnaviral DNA. Ten specimens (0.3%) from Panama and Gabon yielded unique hepadnaviruses in coancestral relation to HBV. Full genome sequencing allowed classification as three putative orthohepadnavirus species based on genome lengths (3,149-3,377 nt), presence of middle HBV surface and X-protein genes, and sequence distance criteria. Hepatic tropism in bats was shown by quantitative PCR and in situ hybridization. Infected livers showed histopathologic changes compatible with hepatitis. Human hepatocytes transfected with all three bat viruses cross-reacted with sera against the HBV core protein, concordant with the phylogenetic relatedness of these hepadnaviruses and HBV. One virus from Uroderma bilobatum, the tent-making bat, cross-reacted with monoclonal antibodies against the HBV antigenicity determining S domain. Up to 18.4% of bat sera contained antibodies against bat hepadnaviruses. Infectious clones were generated to study all three viruses in detail. Hepatitis D virus particles pseudotyped with surface proteins of U. bilobatum HBV, but neither of the other two viruses could infect primary human and Tupaia belangeri hepatocytes. Hepatocyte infection occurred through the human HBV receptor sodium taurocholate cotransporting polypeptide but could not be neutralized by sera from vaccinated humans. Antihepadnaviral treatment using an approved reverse transcriptase inhibitor blocked replication of all bat hepadnaviruses. Our data suggest that bats may have been ancestral sources of primate hepadnaviruses. The observed zoonotic potential might affect concepts aimed at eradicating HBV.
Full-text · Article · Sep 2013 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Influenza A viruses from animal reservoirs have the capacity to adapt to humans and cause influenza pandemics. The occurrence of an influenza pandemic requires efficient virus transmission among humans, which is associated with virus attachment to the upper respiratory tract. Pandemic severity depends on virus ability to cause pneumonia, which is associated with virus attachment to the lower respiratory tract. Recently, a novel avian-origin H7N9 influenza A virus with unknown pandemic potential emerged in humans. We determined the pattern of attachment of two genetically engineered viruses containing the hemagglutinin of either influenza virus A/Shanghai/1/13 or A/Anhui/1/13 to formalin-fixed human respiratory tract tissues using histochemical analysis. Our results show that the emerging H7N9 virus attached moderately or abundantly to both upper and lower respiratory tract, a pattern not seen before for avian influenza A viruses. With the caveat that virus attachment is only the first step in the virus replication cycle, these results suggest that the emerging H7N9 virus has the potential both to transmit efficiently among humans and to cause severe pneumonia.
Full-text · Article · Sep 2013 · American Journal Of Pathology
[Show abstract][Hide abstract] ABSTRACT: Highly pathogenic avian influenza H5N1 virus causes a severe, often fatal, pneumonia in humans. The tropism and pathogenesis of highly pathogenic avian influenza H5N1 virus can partly be explained by the presence of H5N1 virus receptors in the human alveoli, which are the site of inflammation during pneumonia. Although studies on the distribution of influenza virus receptors in normal respiratory tract tissues have provided significant insights into the cell tropism and pathogenesis of influenza viruses, the distribution of influenza virus receptors have not been studied during influenza virus infection. Therefore, we studied the distribution of H5N1 virus receptors, by virus and lectin histochemistry, during highly pathogenic avian influenza H5N1 virus infection in alveolar tissues of humans, macaques, ferrets, and cats. In all species, we observed a decrease of H5N1 virus receptors in influenza virus-infected and neighboring cells. The observed decrease of H5N1 virus receptors was associated with the presence of MxA, a known marker for interferon activity. Taken together, our data suggest that the decrease of H5N1 virus receptors might be part of a defense mechanism that limits viral replication in the lower respiratory tract.
Preview · Article · Aug 2013 · American Journal Of Pathology
[Show abstract][Hide abstract] ABSTRACT: Hepacivirus RNA concentrations in individual solid organ specimens and blood. A. Hepacivirus-positive Myodes glareolus sampled 2008–2010 in The Netherlands and Germany. Virus concentrations are given in Log10 RNA copies per gram of tissue scaled on the y-axis for each rodent organ tested (x-axis). Horizontal bars represent mean virus concentrations per organ category. The number of available specimens per organ category is indicated below. Colors represent viruses from individual rodents as identified in the legend. B. Viral load in Log10 RNA copies per mL of blood in the same 21 animals. For one animal, no blood was available. (TIF)
[Show abstract][Hide abstract] ABSTRACT: Putative cleavage sites for cellular signal peptidases within the N-terminal half of hepacivirus polyproteins. NN: neural networks; HMM: hidden Markov models (the values represent probabilities for putative SP cleavage sites). Only SP cleavage sites predicted by both NN and HMM were considered. All scores were re-calculated upon putting a suggested cleavage site at amino acid position 20 of a query polypeptide. *Y-scores were zero for these sites, however they were supported by uncorrected S-scores (not shown). Hepaciviruses included were SAR46 (KC411807) and SAR3 (KC411806) from Rhabdomys pumilio, RMU10-3382 (KC411777), NLR-365 (KC411796) and NLR-AP70 (KC411784) from Myodes glareolus, HCV-1a (NC_004102) and GBV-B (NC_001655). (DOC)
[Show abstract][Hide abstract] ABSTRACT: Oligonucleotides used for Hepacivirus RT-PCR screening, genome sequencing and virus quantification. aID = identity. bnumbered after CHV polyprotein (GenBank# JF744991); cnumbered after HCV genotype 1a polyprotein (GenBank# NC_004102);dnumbered after CHV genome (GenBank# JF744991) eR = G/A, Y = C/T, S = G/C, W = A/T, M = A/C, K = G/T, H = A/C/T, B = C/G/T, I = inosine, FAM = 6-Carboxy-Fluorescein, JOE = 2,7-Dimethoxy-4,5-dichloro-6-carboxyfluorescein, VIC = proprietary dye (Life Technologies, Darmstadt, Germany), BHQ = Black hole quencher, MGBNFQ = Minor groove binder Non fluorescent quencher; f+t/+c = Locked nucleic acids (LNA) First round RT-PCR used the SuperScript III (SSIII) one-step RT-PCR kit (Invitrogen, Karlsruhe, Germany) with 5 µL of RNA, 400 nM each of 1st-round primers or an equimolar mix of primers, 1 µg bovine serum albumin, 0.2 mM of each dNTP and 2.4 mM of MgSO4. Second round 50 µL Platinum Taq (Invitrogen) reactions used 1 µL of 1st-round PCR product, 2.5 mM MgCl2 and 400 nM each of 2nd-round primers. First round RT-PCR reactions were used a touchdown protocol with reverse transcription at 48° for 30 minutes, denaturation at 95° for 3 minutes, followed by PCR 10 cycles of 15 sec at 94°C, 20 sec at 60°C with a decrease of 1°C per cycle, and extension at 72°C for 45 seconds, followed by another 40 cycles at 50°C annealing temperature. Second round reactions used the same cycling protocol without the RT step. RNA quantification was performed in 25 µL reaction volumes using the SSIII One-Step RT-PCR system (Invitrogen) as described above with 300 nmol/L of respective forward and reverse primers and 200 nmol/L of respective probes. Amplification involved 15 min at 55°C; 3 min at 95°C; 45 cycles of 15 sec at 94°C, and 25 sec at 58°C. Fluorescence was measured at the 58°C annealing/extension step. Published assays from which oligonucleotide primers were used in this study included , , , , . (DOC)
[Show abstract][Hide abstract] ABSTRACT: 5′-non-coding genome region (5′-ncr) of European and African rodent hepaciviruses. A. 5′-end of RMU10-3382 (GenBank, KC411777). This structure was mostly related to the Pegivirus type 4 IRES. Nucleotides conserved with other pegiviruses are marked in red, paired compensatory substitutions in NLR-365 (KC411796) and the partially available NLR-AP70 5-UTR (KC411784) that support the structure are in green. The Ia loop is very similar in length and shape to HCV and GBV-B. The start codon is boxed in red, additional non-functional start codons between the poly-pyrimidine stretch typical for pegiviruses and the true start codon are boxed in blue. The binding site for microRNA-122 is underlined. B. 5′-end of SAR-46 (KC411807). This structure was mostly related to a Hepacivirus type 3 IRES. Nucleotides conserved with HCV are marked in red. The slippery site is underlined. The start codon is boxed. Stem-loop structures in both foldings are numbered according to Pegi- and Hepacivirus reference strains. (TIF)