West Nile Virus NS1 Antagonizes Interferon Beta Production by Targeting RIG-I and MDA5

Abstract

West Nile virus (WNV) is a mosquito-borne flavivirus that causes epidemics of encephalitis and viscerotropic disease worldwide. This virus has spread rapidly and has posed a significant public health threat since the outbreak in New York City in 1999. The interferon (IFN)-mediated antiviral response represents an important component of virus-host interactions and plays an essential role in regulating viral replication. Previous studies have suggested that multifunctional nonstructural proteins encoded by flaviviruses antagonize the host IFN response via various means in order to establish efficient viral replication. In this study, we demonstrated that the nonstructural protein 1 (NS1) of WNV antagonizes IFN-β production, most likely through suppression of retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) activation. In a dual-luciferase reporter assay, WNV NS1 significantly inhibited the activation of the IFN-β promoter after Sendai virus infection or poly(I·C) treatment. NS1 also suppressed the activation of the IFN-β promoter when it was stimulated by interferon regulatory factor 3 (IRF3)/5D or its upstream molecules in the RLR signaling pathway. Furthermore, NS1 blocked the phosphorylation and nuclear translocation of IRF3 upon stimulation by various inducers. Mechanistically, WNV NS1 targets RIG-I and melanoma differentiation-associated gene 5 (MDA5) by interacting with them and subsequently causing their degradation by the proteasome. Furthermore, WNV NS1 inhibits the K63-linked polyubiquitination of RIG-I, thereby inhibiting the activation of downstream sensors in the RLR signaling pathway. Taken together, our results reveal a novel mechanism by which WNV NS1 interferes with the host antiviral response. WNV Nile virus (WNV) has received increased attention since its introduction to the United States. However, the pathogenesis of this virus is poorly understood. This study demonstrated that the nonstructural protein 1 (NS1) of WNV antagonizes the induction of interferon beta (IFN-β) by interacting with and degrading retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5), which are crucial viral sensors in the host innate immune system. Further experiments suggested that NS1-mediated inhibition of the RIG-I-like receptor (RLR) signaling pathway involves inhibition of RIG-I K63-linked polyubiquitination and that the proteasome plays a role in RIG-I degradation. This study provides new insights into the regulation of WNV NS1 in the RLR signaling pathway and reveals a novel mechanism by which WNV evades the host innate immune response. The novel findings may guide us to discover new therapeutic targets and develop effective vaccines for WNV infections.

Zika virus circumvents host innate immunity by targeting the adaptor proteins MAVS and MITA

“…During virus invasion, multiple signaling pathways can be activated to facilitate the high expression of type I IFN and downstream antiviral genes, mainly including RLRs and TLRs (29,30). Previously, it has been extensively shown that flaviviruses, such as dengue virus (DENV), hepatitis C virus, and West Nile virus, can target the RLR pathway, thus blocking the key processes of type I IFN signal transduction and antagonizing the innate immunity with different molecular mechanisms (22,23,31). To explore the potential correlation between NS3/NS2B3-mediated IFNb antagonism and RLR signaling pathway, we constructed Flag-tagged RIG-I-2CARD, MAVS, MITA, TBK1, IRF3-5D expression plasmids and then cotransfected them with HA-tagged NS3 or NS2B3 into HEK293T cells.…”

Comparative transcriptome analysis reveals the role of p53 signalling pathway during red‐spotted grouper nervous necrosis virus infection in Lateolabrax japonicus brain cells

“…Many viruses have developed different mechanisms to escape the antiviral response, including counteracting the activity of ISG15 (Guerra, Cáceres, Knobeloch, Horak, & Esteban, ; Yuan & Krug, ). Several studies have addressed NNV persistent infections in many fish, indicating NNV has developed some mechanisms to antagonize host innate antiviral responses (Lu et al, ; Zhang et al, ). We speculated that RGNNV might counteract the antiviral activity of ISG15 to escape the host antiviral response in LJB cells.…”

PEDV nsp16 negatively regulates innate immunity to promote viral proliferation

“…In Figs. 3 and 4, the HEK293 T cells were seeded in 24-well plates and transfected with the Flag-nsp16, Myc-nsp10, IFN-β-luc reporter, the LacZ and poly I:C or Flag-RIG-I(N) or Flag-MDA5(N) (Zhang et al, 2017) for 24 h and then the cells were lysed for luciferase assays and western blotting.…”