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

  • duck RIG-I promoter
  • PB1-F2
  • duck MAVS
  • Influenza A virus

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-grzy-g666

• License

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