The Mechanism Underlying Type ? IFNs-mediated Innate Immune Response To CSFV Infection

In this study,we examined the expression of interferon-?s(IFN-?s)after infection with classical swine fever virus(CSFV)through in vitro and in vivo experiments.Porcine PK-15 cell line,IFN-?1 knockdown PK-15 cell lines,and pigs were used in this project.We firstly determined IFN-?s mRNA expression levels by RT-PCR and qRT-PCR assays in PK-15 cells infected with Shimen strain for 12 h,24 h,36 h,48 h and 60 h respectively,and the phosphorylation levels of STAT1 protein were also analysed by Western blotting.Then the protein and mRNA expression levels of IFN-?s in the spleens,submandibular lymph nodes,mesenteric lymph nodes,inguinal lymph nodes and tonsils of pigs,which were infected with CSFV Shimen strain by intramuscular injection for 5 days,were examined by ELISA,RT-PCR and qRT-PCR assays.The phosphorylation levels of STAT1 protein in those organs were also investigated by Western blotting.In addition,several important interferon stimulated genes(ISGs)playing a crucial role in antiviral infections were tested by RT-PCR and Western blotting.The results are shown as follows:1)Time course studies of CSFV infection showed that mRNA expression levels of IFN-?s in PK-15 cells were consistently increased during CSFV infection.However,the mRNA expression levels started to declined after 48 h of the infection.2)The IFN-?s mRNA levels were increased obviously in the spleens,submandibular lymph nodes,mesenteric lymph nodes,inguinal lymph nodes and tonsils of pigs after CSFV infection.3)The ability of CSFV replication was enhanced in PK-15 cells when IFN-?1 expression was silenced.4)After infection with CSFV,the phosphorylation levels of STAT1 protein in PK-15 cells and pigs were increased at the cellular and animal levels.In addition,the mRNA and protein expression level of several important ISGs levels in infected pigs were much higher than that in non-infected control pigs.These results reveal that CSFV infection can effectively induce the expression of type ? IFNs,activate JAK-STAT signaling pathway,and expression of several important ISGs in host.Our findings suggest that CSFV infection may induce the host to produce effective type ? interferons-mediated innate immune response.