The Mechanism Of Activation Of Inflammatory Response By Peste Des Petits Ruminants Virus

Peste des petits ruminants(PPR)is a severe infectious disease with high morbidity and mortality caused by the PPR virus(PPRV),which infects goats,sheep,deer,antelope,and other artiodactyls.PPR has been listed as a statutory reported disease by the Office International Des Epizooties(OIE)and China.At present,the PPR epidemic situation is still severe in some regions of China,such as Tibet,Xinjiang,Inner Mongolia,Gansu,Ningxia,and other places that have reported the outbreak of PPR.Although wide applications of the attenuated PPR vaccines have controlled the PPR pandemic,PPRV is still popular and uninterrupted in some regions,posing a serious threat to the development of the breeding industry in our country.The inflammasome is a cytoplasmic protein complex composed of cytoplasmic sensor molecule NLRP3,effector protein caspase-1,and apoptosis-associated speck-like protein ASC.Inflammasome plays an important role in the host defense by recognizing viral infection.Activation of NLRP3 inflammasome regulates IL-1β release and plays a crucial role in viral infection.Activation of NLRP3 inflammasome is mainly caused by the maturation and release of inflammatory cytokines,which can be induced by a variety of different pathogenic and stimulating factors,with the complex activation process.Numerous studies have shown that some RNA viruses regulate NLRP3 inflammasome by self-replication.Our previous studies have shown that goats infected with PPRV present clinical symptoms including fever,inflamed lips,stomatitis,and pulmonary enteritis,which suggested that PPRV infection induces inflammation in the host.Therefore,the scientific question of this study is how PPRV infection causes an inflammatory response and the specific mechanism of PPRV induced inflammatory response.To address the scientific questions,PPRV-infected goat PAM were used to perform RNA sequencing analysis and the results showed that PPRV infection with PAM could induce upregulation of inflammatory cytokines,activation of inflammation,and NF-κB signaling pathways.The pathological changes of PPRV infected goat tissues were further observed.The results showed that the lung,kidney,and liver goats presented different degrees of pathological changes and inflammatory cell infiltration,and other typical inflammatory reactions.In addition,PPRV infection with PAM increased the expression of inflammatory cytokines,including TNF-α,IL-1β,and IL-6.Subsequently,q RT-PCR,ELISA,and Western blot(WB)were performed on THP-1 to confirm that PPRV could infect THP-1 cells and activate the NLRP3 inflammasome.And PPRV increased the expression of inflammatory cytokines,including TNF-α,IL-1β,and IL-6 in THP-1 cells.In addition,Western blot results also showed that PPRV activated the NF-κB signaling pathway by inducing phosphorylation of p65 and IκBα.Meanwhile,we found that PPRV N protein increased IL-1βexpression by ELISA and WB.In addition,a dual fluorescence reporter assay indicated that N protein promoted IL-1β-triggered Nifty promoter(a reporter of NF-κB)activation,suggesting that N protein activated an inflammatory response.Finally,immunoprecipitation and indirect immunofluorescence experiments verified that N protein directly binds NLRP3 to induce NLRP3 inflammasome assembly,and PPRV N protein can interact with My D88 to promote the formation of the My D88-TRAF6 complex.The results of q RT-PCR and WB further suggested that overexpression of N protein promotes the replication of PPRV in vitro.Taken together,these studies suggest that PPRV infection induced an inflammatory response.PPRV activated the NF-κB signaling pathway by inducing phosphorylation of p65 and IκBα,and promoted IL-1β expression by activating the NLRP3 inflammasome.Besides,PPRV N protein was involved in the activation of the inflammatory responses through direct interaction with NLRP3 and My D88.This study revealed the unique mechanism by which PPRV activated inflammatory responses and induced IL-1β release,which provides a novel idea for the pathogenesis of PPRV and provides a theoretical basis for the prevention and control or the design of new vaccines of PPR.