Identification Of Amino-acid Residues In The V Protein Of Peste-Des-Petits-Ruminants Essential For Interference And Suppression Of IFN-mediated Innate Immune System

Peste des petits ruminants disease(PPRV) is an highly contagious, and immunosuppressive small ruminants disease caused by PPR virus(PPRV). PPRV infection causes severe damages in host organs.leading cause of death among Small ruminants including both domestic and wild, especially in goats and sheep, always cause serious economic loss. Although PPRV-induced severe damages in host organs has been established, the underlying molecular mechanism of immunosuppressive is still unclear. By luciferase assay the effect of V protein of PPRV plays a pivotal role in interfering with host innate immunity by blocking the production of IFNs and IFNs signaling. We revealed the critical role of PPRV V inhibits ds RNA-induced IFN production. First, we confirmed that PPRV V and its VCT deletion mutations can block MDA5, not RIG-I,-mediated IFN production. Second, we found that LGP2 as a positive regulator to inhibit RLRs-mediated IFN production when over-expression PPRV V protein.Finally, by using deletion and site-directed mutagenesis, we identified that Cys acid residues cluster were critical amino acids for V-induced immunosuppression. To further investigate the mechanism of PPRV V inhibits IFN-induced immuno-suppression, we used PPRV V protein and its mutations as bait to screen the effective sites of V protein in STAT-mediated IFN signaling inhibition. Cys cluster and Trp acid residues were identified as important sites of C terminal of V protein interacting with STAT2 and Y110 acid residue was important site for N terminal of V protein to interact with STAT1. Next, we found that V protein changes the distribution of STAT proteins. Taken together, our results revealed that PPRV V protein, one of the major inhibitor to block innate immunity. Mutagenesis defines that Cys cluster and Trp motif of PPRV-V are essential for STAT-mediated IFN signaling and RLRs-mediated IFN production. These findings give a new sight for the further studies to understand the delicate mechanism of PPRV to escape the innate immunity.