Inhibitory Effect Of Bovine Enterovirus 2A And 3C Protease On The Expression Of Bovine Interferon Beta By Negatively Regulating On MAVS

Bovine enterovirus(BEV)belongs to the enterovirus genus of small RNA virusclass,which is a single strand of positive strand RNA virus.BEV can be transmitted through the fecal and mouth,often lead to animal mixed infection with variety of pathogens,since it can infect the digestive tract and the stable physical properties,it can be exposed through the host defecation in the water and environment,causing harm to the ranch.In our previous studies,we found that found that BEV virus can infect young rabbits,guinea pigs,and can cause lungs,liver obviously congestion and swelling.Besides the virus particles can be tested in the liver,kidney,spleen and lung tissues.Infection of BEV may reduce the host's immune response,provide an opportunity for the infection of other bacteria and virus.In order to explore how BEV escapes host innate immune,our study conducted the following exploration.To investigate the effect of BEV infection on the expression of bovine type I IFN,ISGs,and key molecules in RLR signaling pathways,the results showed that BEV infection could not significantly increase the transcription of Bo IFN-?,ISGs and key molecules of RLR signaling pathways,which indicating that the response of type I IFN is w eak in BEV infected cells.To further explore how BEV antagonizes the production of bovine type I IFN interferon,our study cloned BEV nonstructural proteins 2A and 3C,and overexpression the 2A and 3C in MDBK and BL cells to detect their effects on Bo IFN-?,ISGs and key molecules of RLR signal pathway by Real-time fluorescence quantitative PCR.Results showed that 2A and 3C could inhibit the transcription expression of Bo IFN-?,Mx1,ISG15,RIG-I and MAVS;Western Blot results show that 2A and 3C negatively regulates the expression of MAVS protein and inhibits the expression of Mx1 and NF-?B p65 protein induced by overexpression of MAVS.2A and 3C did not inhibit the transcription expression of Bo IFN-? and ISGs in MDBK cells knocked down by MAVS.The results showed that 2A and 3C could inhibit the formation of interferon with MAVS as target molecule.Double luciferase system test results showed that 2A,3C inhibited IFN-? promoter,ISRE and NF-?B regulated luciferase activity.Real-time fluorescence quantitative PCR and cytopathic effect inhibition bioassay showed that after the infection of BEV,the virus titer of MDBKpsi MAVS and MDBKsh MAVS cells is higher than that of normal MDBK cells.This study found that the response of type I IFN is weak in BEV infected cells;2A and 3C can negatively regulate the transcription and protein expression of MAVS,inhibition the luciferase activity of Bo IFN-? promoter,ISRE,NF-?B.BEV antagonized the formation of host interferon through its non-structural proteases 2A and 3C.In breif,the study provide an idea for the study of BEV antagonizing host innate immune response.