ABSTRACT: Differences in cytokine production in human macrophages and in virulence in mice are attributable to the PA protein of H5N1 influenza viruses
Project description:Background. The pathogenesis of influenza A virus subtype H5N1 (hearafter, "H5N1") infection in humans is not completely understood, although hypercytokinemia is thought to play a role. We previously reported that most H5N1 viruses induce high cytokine responses in human macrophages, whereas some H5N1 viruses induce only a low level of cytokine production similar to that induced by seasonal viruses. Methods. To identify the viral molecular determinants for cytokine induction of H5N1 viruses in human macrophages, we generated a series of reassortant viruses between the high cytokine inducer A/Vietnam/UT3028II/03 clone 2 (VN3028IIcl2) and the low inducer A/Indonesia/UT3006/05 (IDN3006), and evaluated cytokine expression in human macrophages. Results. Viruses possessing the acidic polymerase (PA) gene of VN3028IIcl2 exhibited high levels of hypercytokinemia-related cytokine expression in human macrophages, compared with IDN3006, but showed no substantial differences in viral growth in these cells. Further, the PA gene of VN3028IIcl2 conferred enhanced virulence in mice. Conclusions. These results demonstrate that the PA gene of VN3028IIcl2 affects cytokine production in human macrophages and virulence in mice. These findings provide new insights into the cytokine-mediated pathogenesis of H5N1 infection in humans.
Project description:Background. The pathogenesis of influenza A virus subtype H5N1 (hearafter, "H5N1") infection in humans is not completely understood, although hypercytokinemia is thought to play a role. We previously reported that most H5N1 viruses induce high cytokine responses in human macrophages, whereas some H5N1 viruses induce only a low level of cytokine production similar to that induced by seasonal viruses. Methods. To identify the viral molecular determinants for cytokine induction of H5N1 viruses in human macrophages, we generated a series of reassortant viruses between the high cytokine inducer A/Vietnam/UT3028II/03 clone 2 (VN3028IIcl2) and the low inducer A/Indonesia/UT3006/05 (IDN3006), and evaluated cytokine expression in human macrophages. Results. Viruses possessing the acidic polymerase (PA) gene of VN3028IIcl2 exhibited high levels of hypercytokinemia-related cytokine expression in human macrophages, compared with IDN3006, but showed no substantial differences in viral growth in these cells. Further, the PA gene of VN3028IIcl2 conferred enhanced virulence in mice. Conclusions. These results demonstrate that the PA gene of VN3028IIcl2 affects cytokine production in human macrophages and virulence in mice. These findings provide new insights into the cytokine-mediated pathogenesis of H5N1 infection in humans. Human monocyte-derived macrophages were mock-infected, or infected with IDN3006, VN3028IIcl2, or IDN3006/cl2PA at a multiplicity of infection (MOI) of 2. At 6 hours post-infection (hpi), the cells were harvested and subjected to microarray analysis (three technical replicates per each group).
Project description:Macrophages were infected with low (PR8) and high pathogenic influenza viruses (FPV and H5N1). To our surprise a genome-wide comparative systems biology approach revealed that in contrast PR8 infections with HPAIV H5N1 and FPV result in a reduced immune response of human macrophages contradicting a primary role of this cell type for the cytokine storm. Our data point to a viral strategy of HPAIV to bypass a major amplifier of the initial local inflammatory response thereby hampering antiviral effector mechanisms and facilitating virus spreading and systemic disease. Macrophages were infected with low (PR8) and high pathogenic influenza viruses (FPV and H5N1)
Project description:Human disease caused by highly pathogenic avian influenza (HPAI) H5N1 can lead to a rapidly progressive viral pneumonia leading to acute respiratory distress syndrome. There is increasing evidence suggests a role for virus-induced cytokine dysregulation in contributing to the pathogenesis of human H5N1 disease. The key target cells for the virus in the lung are the alveolar epithelium and alveolar macrophages, and previous data has shown that compared to seasonal human influenza viruses, equivalent infecting doses of H5N1 viruses markedly up-regulate pro-inflammatory cytokines in both primary cell types in vitro. The dysregulation of H5N1-induced host responses is therefore important for understanding the viral pathogenesis. We used microarrays to analyze and compare the gene expression profiles in primary human macrophages after influenza A virus infection.
Project description:Human disease caused by highly pathogenic avian influenza (HPAI) H5N1 can lead to a rapidly progressive viral pneumonia leading to acute respiratory distress syndrome. There is increasing evidence suggests a role for virus-induced cytokine dysregulation in contributing to the pathogenesis of human H5N1 disease. The key target cells for the virus in the lung are the alveolar epithelium and alveolar macrophages, and previous data has shown that compared to seasonal human influenza viruses, equivalent infecting doses of H5N1 viruses markedly up-regulate pro-inflammatory cytokines in both primary cell types in vitro. The dysregulation of H5N1-induced host responses is therefore important for understanding the viral pathogenesis. We used microarrays to analyze and compare the gene expression profiles in primary human macrophages after influenza A virus infection. Peripheral-blood leucocytes were separated from buffy coats of three healthy blood donors and cells were differentiated for 14 days before use. Differentiated macrophages were infected with H1N1 and H5N1 at a multiplicity of infection (MOI) of two. Total RNA was extracted from cells after 1, 3, and 6h post-infection, and gene expression profiling was performed using an Affymetrix Human Gene 1.0 ST microarray platform.
Project description:The highly pathogenic avian influenza (HPAI) H5N1 viruses continue to circulate in nature and threaten public health. Although several viral determinants and host factors that influence the virulence of HPAI H5N1 viruses in mammals have been identified, the detailed molecular mechanism remains poorly defined and requires further clarification. In our previous studies, we characterized two naturally isolated HPAI H5N1 viruses that had similar viral genomes but differed substantially in their lethality in mice. Here, we explored the molecular determinants and potential mechanism for this difference in virulence. By using reverse genetics, we found that a single amino acid at position 158 of the hemagglutinin (HA) protein substantially affected the systemic replication and pathogenicity of these H5N1 influenza viruses in mice. We further found that the G158N mutation introduced an N-linked glycosylation at sites 158–160 of the HA protein and that this N-linked glycosylation enhanced viral productivity in infected mammalian cells and induced stronger host immune and inflammatory responses to viral infection. These findings further our understanding of the determinants of pathogenicity of H5N1 viruses in mammals.
Project description:Macrophages were infected with low (PR8) and high pathogenic influenza viruses (FPV and H5N1). To our surprise a genome-wide comparative systems biology approach revealed that in contrast PR8 infections with HPAIV H5N1 and FPV result in a reduced immune response of human macrophages contradicting a primary role of this cell type for the cytokine storm. Our data point to a viral strategy of HPAIV to bypass a major amplifier of the initial local inflammatory response thereby hampering antiviral effector mechanisms and facilitating virus spreading and systemic disease.
Project description:This study revealed important similarities but also critical differences between the H5N1 and 1918-reassortant viruses, highlighting aspects of the host–pathogen interface caused by highly virulent influenza viruses.
Project description:This study aims at elucidating how H5N1 influenza infection perturbs the host's miRNA regulatory pathways that may lead to adverse pathological events, such as cytokine storm, using the miRNA microarray approach. The cell line - NCI-H292, was infected with various preparations of H5N1 influenza viruses was analysed for miRNA expression profiles subsequently. The miRNA expression profiles were measured at 3, 6, 18, and 24 hours post infection, respectively.
Project description:Highly pathogenic influenza virus inhibit Inflammatory Responses in Monocytes via Activation of the Rar-Related Orphan Receptor Alpha (RORalpha). Low (PR8) and high pathogenic influenza viruses (FPV and H5N1) were used. Monocytes were infected with low (PR8) and high pathogenic influenza viruses (FPV and H5N1)