Study the Regulation of Innate Immune Response upon the Novel Avian Influenza a Virus (H7N9) Infection by an ex vivo Human Airway Epithelial Cell Culture Model (I)

Infections of Influenza A virus could result in severe respiratory complications and death. In March, 2013, an H7N9 subtype of avian influenza A virus was reported to infect humans and has caused severe diseases in China. Therefore, it is urgent to elucidate the molecular mechanisms for pathogenicity of H7N9 virus. Because an ex vivo model of human airway epithelial cell cultures will be established by the 4th component project of this integrated project, we will applied this model for characterizing the role of individual gene of H7N9 virus in pathogenesis. To investigate the unique characteristics for individual genes from the highly pathogenic virus, a reverse genetics system for an H7N9 virus, A/Anhui/01/2013/H7N9, will be established. It has been shown that influenza virus employs several mechanisms to block host innate immune response for supporting virus replication at early time during infection. We intend to employ the ex vivo culture model and the H7N9 virus from reverse genetic system to investigate the regulation of type-I IFN response upon the virus infection. The results obtained from the ex vivo respiratory tract epithelial cells should be much relevant to the actual state during human infection. Since it has been demonstrated that NS1 protein of influenza A virus suppresses of type-I IFN response via different mechanisms, it is proposed that NS1 protein is involved in the pathogenicity. To reveal whether the NS1 protein of the H7N9 virus could be one of the major causes to pathogenicity due to blocking the expression of type-I IFN, we intend to determine the ability of NS1 encoded by H7N9 virus in inhibiting type-I IFN expression by the ex vivo cell cultures and the NS1-transfected HEK293T models. Furthermore, several studies showed that PA protein of H5N1 influenza virus may be involved in pathogenicity during influenza virus infection. Previous studies from Dr. Shin-Ru Shih’s and our laboratories also demonstrated that PA encoded by H5N1 not only enhances the polymerase activity of seasonal influenza but also causes strong pathogenesis in caspase-1-deficient mice. These findings indicate that PA protein of influenza virus plays a role in virulence. Additionally, our previous experiments found that PA protein interacts with several proteins that are located on mitochondrion. Because mitochondrion is on a crucial position for initiating host innate immunity, we intend to investigate the role of PA in H7N9 virus-induced innate response, such as type-I IFN response, by ex vivo and in vitro models. Moreover, the host proteins that are involved in innate immune response and interact with PA protein in the H7N9-infected respiratory tract epithelial cells will be identified. In summary, the major goals of this grant proposal are to investigate the regulation of host innate response during the novel avian influenza virus (H7N9) infection, and to reveal the roles of viral proteins, NS1 and PA, in the regulation of innate immune response by an ex vivo model. The information obtained from this research should facilitate the understanding for pathogenicity of the H7N9 virus and antiviral development.

Project ID:PC10304-0013
External Project ID:MOST103-2321-B182-011