Systems-Level Comparison of Host-Responses Elicited by Avian H5N1 and Seasonal H1N1 Influenza Viruses in Primary Human Macrophages

Abstract

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 from clinical, animal models and in vitro data, which 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 we have 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. Whether this H5N1-induced dysregulation of host responses is driven by qualitative (i.e activation of unique host pathways in response to H5N1) or quantitative differences between seasonal influenza viruses is unclear. Here we used microarrays to analyze and compare the gene expression profiles in primary human macrophages at 1, 3, and 6 h after infection with H5N1 virus or low-pathogenic seasonal influenza A (H1N1) virus. We found that host responses to both viruses are qualitatively similar with the activation of nearly identical biological processes and pathways. However, in comparison to seasonal H1N1 virus, H5N1 infection elicits a quantitatively stronger host inflammatory response including type I interferon (IFN) and tumor necrosis factor (TNF)-α genes. A network-based analysis suggests that the synergy between IFN-β and TNF-α results in an enhanced and sustained IFN and pro-inflammatory cytokine response at the early stage of viral infection that may contribute to the viral pathogenesis and this is of relevance to the design of novel therapeutic strategies for H5N1 induced respiratory disease.

Distinct Macrophage Subpopulations Characterize Acute Infection and Chronic Inflammatory Lung Disease

“…Mem71 is a type A influenza strain of intermediate virulence that, given at sublethal dosages, induces a lung inflammatory response that peaks at day 3 and is resolved by day 10 (34). In contrast, infection with high-fatality influenza A strains (i.e., avian H5N1/97) leads to patient death from acute respiratory distress and multiple organ dysfunction, postulated to be caused by aberrant cytokine production from virus-exposed lung MFs (5,35). Interestingly, CCR2 2/2 mice infected with the highly virulent PR8 influenza A strain virus have decreased lung monocyte recruitment and are protected against morbidity and mortality independent of virus clearance efficiency (6,14), clearly highlighting the significant contributions of lung monocytes in acute lung disease.…”

Influenza virus replication in macrophages: balancing protection and pathogenesis

“…Combined with evidence that macrophages support productive replication of some IAV strains, excessive cytokine production following H5N1 infection may be a result of productive virus replication in macrophages. Of particular interest because of its role in immunopathology, the cytokine TNF-a is induced to high levels in human MDMs infected with HPAI H5N1 viruses or with a seasonal H3N2 virus [16,52,59]. While these studies did not directly correlate TNF-a production with virus replication, in another report, HPAI H5N1 and seasonal H3N2 IAV were shown to replicate in human MDMs [37].…”

“…On the other hand, macrophages have been implicated in the pathogenesis of severe IAV disease. Excessive pulmonary infiltration of macrophages secreting enhanced levels of pro-inflammatory cytokines is a hallmark of IAVinduced severe pneumonia [14][15][16][17]. Recently, efforts to understand the role of macrophages in IAV pathogenesis have focused on whether influenza viruses have the ability to replicate productively in macrophages.…”

Toll-like receptor 10 is involved in induction of innate immune responses to influenza virus infection

“…We next investigated whether the expression of cytokines typically up-regulated following influenza A virus infection (Fig. 4A) (14,15) is TLR10 dependent. TLR10 shRNA knockdown (KD) in THP-1 cells (Fig.…”

“…Our previous studies have demonstrated that influenza A virus replicates and induces proinflammatory cytokine responses and paracrine cytokine cascades in human peripheral blood monocyte-derived macrophages and alveolar epithelial cells (13)(14)(15).…”