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Influenza A virus interferes with innate immune signaling in avian cells

  • Author / Creator
    Xiao, Yanna
  • Retinoic Acid-Inducible Gene I (RIG-I) plays an essential role in the host innate immune response to influenza A viruses. RIG-I is present in ducks, but absent in chickens. Our previous work suggests that it might be worthwhile to make chickens transgenic for duck RIG-I under the control of its own promoter to improve their ability to detect and respond to influenza infection. However, it was not known whether the duck RIG-I promoter would function in chicken cells. Here, I identified the duck RIG-I promoter and showed that activation of the MAVS pathway by the constitutively active N-terminal region of RIG-I or poly (I:C) led to stimulation of duck RIG-I promoter activity. Two essential cis-regulatory elements in the core promoter region, a GC-box and an interferon-sensitive response element (ISRE) were responsible for the basal and inducible expression of duck RIG-I, respectively. Chicken IRF7 rather than chicken IRF1 induced duck RIG-I promoter activity using the putative ISRE. Thus, I have identified the minimal necessary promoter for basal and inducible expression of RIG-I, which can be used in transgenes. PB1-F2 from influenza virus PR8 (H1N1) was reported to inhibit RIG-I mediated type I IFN production via interaction with MAVS in mammals, as the critical adaptor protein, duck MAVS was still not well characterized, but is very different from mammalian MAVS. PB1-F2 contributes to the high pathogenesis of A/Vietnam/1203/04 (H5N1) (VN1203) in ducks, but the underlying mechanism by which PB1-F2 increases the virulence of VN1203 was yet unknown. The multiple roles of PB1-F2 were mainly characterized in the mammalian system, and in a virus strain-, cell type-, and species-specific manner. Limited information about PB1-F2 is available in avian cells. Here, I characterized duck MAVS and PB1-F2 proteins from PR8 and three similar highly pathogenic avian influenza viruses: VN1203, reverse-genetics recombinant VN1203 (rgVN1203), and A/duck/Thailand/71.1/2004 (D4AT) in avian cells, and further investigated the association of these two proteins. DuMAVS and PR8 PB1-F2 were distributed in the mitochondria of DF-1 cells, while, H5N1 PB1-F2 proteins were distributed throughout the cells. Like human MAVS, overexpression of duck MAVS could stimulate IFN-β promoter activity and it associated with duck RIG-I 2CARD. All tested PB1-F2 proteins inhibited IFN-β promoter activities stimulated by duck RIG-I 2CARD and they all showed similar staining patterns and were co-immunoprecipitated by duck MAVS, suggesting interactions between these PB1-F2 proteins and duck MAVS are likely. These studies lead to a greater understanding of the role of PB1-F2 in the contribution to viral virulence in the reservoir host.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/r3-grzy-g666
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.