Distinct Immune Escape Mechanisms of Bovine Cronavirus Nucleocapsid by
Suppressing beta Interferon Production via Retinoic Acid-inducible Gene
I-like Receptor Pathway
Abstract
The present study aimed to explore if bovine coronavirus nucleocapsid
(BCoV N) impacts beta interferon (IFN-β) production in the host cells
and to reveal further molecular mechanism of BCoV pathopoiesis. Human
embryonic kidney (HEK) 293T cells were transientlly transfected with
pCMV-Myc-BCoV-N recombinant plasmids, then infected with the vesicular
stomatitis virus (VSV). Expression levels of IFN-β mRNA were detected
using qPCR. The results determinated that pCMV-Myc-BCoV-N recombinant
plasmids of 1347bp was successfully constructed and transcribed into HEK
293T cells. Western-blotting assay indicated that BCoV-N recombinant
plasmids had excellent antigenicity. BCoV-N recombinant proteins
inhibited dose-dependently IFN-β production mediated by Vesicular
stomatitis virus (VSV) (P<0.01). Furthermore, MDA5, MAVS, TBK1
and IRF3 could promote transcription levels of IFN-β mRNA. But, BCoV-N
proteins demoted IFN-β levels induced by MDA5, MAVS, TBK1 and IRF3.
Expression levels of MDA5, MAVS, TBK1 and IRF3 mRNAs were reduced in
retinoic acid-inducible gene I-like receptor (RLR) pathway. In
conclusion, BCoV-N reduced IFN-β levels in RLR pathway of HEK 293T
cells. BCoV-N protein inhibited IFN-β production and activation of RLRs
signal pathway. Our findings demonstrated a new mechanism evolved by
BCoV to inhibit type I IFN production and provided a solid scientific
basis for revealing the pathogenesis of BCoV, which is beneficial for
developing novel strategy of the diagnose and therapy of BCoV disease.