OAS2 Inhibit Zika Virus Replication Through Type-? Interferon Pathway

Background:2',5'-oligoadenylate synthetase 2(OAS2)has been known as an antiviral interferon-stimulated gene(ISG).However,the role of OAS2 on Zika virus(ZIKV)replication are still unknown.In this study,we sought to explore the mechanism by which OAS2 affects on ZIKV replication.Methods:We performed RNAseq to identify the host genes regulated by ZIKV infection in A549 cells.The expression of the top 4 upregulated and 4 downregulated genes were confirmed by qRT-PCR.We selected one of the most upregulated gene,OAS2,for further investigation.Huh7.0/Huh7.5.1 and U5A/2fTGH cells were used to investigate whether the induction of OAS2 by ZIKV was dependent on RIG-I or I-IFN,respectively.To study the effect of OAS2 on ZIKV replication and anti-ZIKV activity of IFN?,OAS2 was overexpressed in A549 cells,2fTGH cells and U5A cells followed by ZIKV infection 24h post-transfection.Cells were treated with or without IFN? for 24 hours.ZIKV RNA and NS1 protein,as well as the selected genes expression were tested by RT-qPCR and Western Blot.To study the effect of OAS2 on Jak/STAT signaling pathway,OAS2 was overexpressed.Selected genes mRNA,the levels of phosphorylation of STAT1(p-STAT1)and interferon stimulated response element(ISRE)activity were examined by RT-qPCR,Western Blot and luciferase assay respectively.Results:We observed 34 significantly up-regulated genes and 10 significantly down-regulated genes in case of ZIKV infection(Iog2FC>2,p<0.05).We confirmed the top 8 deregulated gene expression using RT-qPCR.The results consisted with our RNAseq results.Of the 4 up-regulated genes,we selected OAS2,the most significant increased gene induced by ZIKV infection for further investigation.We found that ZIKV induced OAS2 in Huh7.0 cells,but not in Huh7.5.1 cells.RIG-I overexpression increased the expression of OAS2,while silencing of RIG-I decreased the expression of OAS2.These results indicated that ZIKV induced OAS2 expression through a RIG-I dependent pathway.We also found OAS2 overexpression inhibited ZIKV replication and enhanced the antiviral activity of IFN? in A549 cells and 2fTGH cells.However,in RIG-I-knockdown A549 cells and IFNAR1-deficient U5A cells,OAS2 had no effect on ZIKV replication.Further investigation showed that overexpression of OAS2 promoted IFN? production through increasing IFN? promoter signaling.Overexpression of OAS2 activated the Jak/STAT signaling pathway by increasing the phosphorylation of STAT1,ISRE activity and a subset of ISGs expression.Conclusion:OAS2 plays an important role in ZIKV replication.ZIKV induced OAS2 through a RIG-I-dependent and I-IFN-partially-dependent pathway.OAS2 exerts its anti-ZIKV activities by enhancing IFN signaling pathway activation.