Preliminary Studies On Kobuvirus VP3 Protein Inhibiting The IFN-?-triggered Signaling Pathway

Porcine Kobuvirus(PKV)is a non-enveloped,single-stranded,positive-sense RNA virus,belonging to the family Picornaviridae genus Kobuvirus.At present,Kobuvirus mainly causes epidemic diarrhea and infectious gastroenteritis.The virus cooperates to form a mixed infection with other porcine pathogens.The infectious disease severely harms to the swine industry since it is difficult to be cured.So it is important to explore the mechanism of Kobuvirus in innate immunity to prevent the virus from affecting swine.PKV genome structure is relatively simple.It consists of a 5' non-coding region,a large open reading frame and a 3' non-coding region.PKV genome mainly encodes 11 proteins including a leader protein(L),three structural proteins(VP0,VP3,and VP1)and seven non-structural proteins(2A-2C,and 3A-3D).In this study,we screened the structural and non-structural proteins by a dual-specific luciferase reporter assay and found that PKV VP3 inhibited the signal pathway induced by type I interferon(IFN-?)dose-dependently.In addition,the same results showed PKV VP3 negatively regulated the IFN-?-triggered signaling pathway without cell-type specificity as well.The biochemical experiments indicated PKV VP3 inhibited the pathway by blocking the interaction of STAT2-IRF9 and STAT2-STAT2 complex.This inhibitory effect also blocked the entry of STAT2-IRF9 and STAT2-STAT2 complexes to the nucleus and was not mediated by STAT2 and IRF9 phosphorylation.Co-immunoprecipitation results showed that the regions of STAT2(aa 580-680)and IRF9(aa 118-390)were essential for the PKV VP3 association.Therefore,we prelimninarily conclude that the PKV VP3 protein inhibited the type I interferon receptor signaling pathway by disrupting the the interaction of STAT2-IRF9 and STAT2-STAT2 complex.In summary,our findings reveal a novel mechanism for PKV evading innate immune responses.