Effect of porcine epidemic diarrhea virus nsp1 on type I interferon response

Porcine epidemic diarrhea virus (PEDV) inhibits the host type I interferon and cellular antiviral response, but its inhibition mechanism is unclear, and the roles of PEDV nonstructural proteins in regulating type I interferon responses have been seldom studied. To study the effect of nsp1 on type I interferon response, nsp1 gene was cloned into a eukaryotic expression vector pCAGGS. The expression of nsp1 in transfected cells was determined by Western blot and indirect immunofluorescence assay. The effects of nsp1 on the induction of type I interferon were evaluated by dual luciferase reporter gene assay, ELISA and VSV bioassay. Western blot and indirect immunofluorescence assay showed that nsp1 was highly expressed in transfected cells and PEDV-infected cells. Dual luciferase reporter gene assay results indicated that nsp1 strongly inhibited the IFN-β promoter activity, and the inhibitory effect was nsp1 dose-dependent. ELISA results showed that nsp1 significantly inhibited the expression of IFN-β in protein level. And VSV replication-inhibition bioassay revealed that nsp1 significantly inhibited type I IFN antiviral activities induced by poly(I: C). Our results implied that nsp1 was a highly conserved protein of PEDV and exhibited antagonistic function on interferon promoter activity. The results have laid a foundation for further understanding the immune evasion mechanism of PEDV and for developing new effective vaccine against PEDV.