The Molecular Mechanisms Of Viral Protein Escape From Innate Immunity In CAEV-Infection

Goat arthritis encephalitis is a chronic progressive infectious disease caused by Caprine arthritis-encephalitis virus(CAEV),which seriously threatens the development of the sheep industry.Chronic infection,lifelong poisoning,multi-tissue inflammation is the main feature of the disease.Innate antiviral immunity is essential for the host defense system and can inhibit virus infection by early detection of virus invasion and rapid initiation of defense mechanisms.Interferon ?(IFN-?)is an important marker for evaluating innate immunity and has immune regulation and a broad spectrum of antiviral activity.In order to clarify the role of CAEV in the production of IFN-? and to understand the effect of CAEV infection on innate immunity of host cells,this article analyzed the effect of six CAEV proteins and studied their molecular mechanisms in the production of IFN-?,providing basis for understanding the pathogenic and immune mechanisms of CAEV.The main results are as follows:(1)The effect of different CAEV encoding proteins on the transcription and expression of IFN-?:The virus-encoded protein plays an important role in the regulation of viral infection.In this study,six proteins of CAEV were selected: protease RVP;dUTP enzyme DU;protein Tat that facilitates viral RNA synthesis;protein IN that promotes virus genome integration;regulatory protein Vif and the main antigen protein P25.The eukaryotic expression vector carrying the gene of interest were constructed and transfected into 293 T cells and inoculated with SeV or VSV virus to detect the effect of different virus-encoded proteins on IFN-? production.The proliferation of SeV and VSV-GFP was detected by qRT-PCR and fluorescence microscopy.The results showed that DU and Vif can inhibit the transcription and expression of IFN-?,promote the proliferation of virus SeV and VSV,but other proteins have no significant effect on the expression of IFN-?.(2)Effects of DU and Vif on the inhibition of IFN-? signaling pathway: The effects of DU and Vif on the production of IFN-? and the regulatory transcription factors were investigated by using qRT-PCR and luciferase reporter systems.The RIG-I/MDA5/MAVS/TBK1 plasmid was used to transfect cells to activate the IFN-? pathway.IFN-? production was characterized by detecting the luciferase activity under the control of two different transcription factors: ISRE,NF-?B.The results showed that overexpression of DU and Vif inhibited the activity of luciferase under the control of ISRE,NF-?B and IFN-? promoters,but overexpression of DU or Vif did not affect the regulation of IRF3-activated IFN-? promoter.The activity of the luciferase was shown to indicate that DU and Vif inhibit activation of the IFN-? signaling pathway by negatively regulating the activity of IRF3 upstream signaling transduction.The amino acid 149-164 of Vif protein was deleted,and its inhibitory effect on IFN-? was significantly weakened,indicating that the amino acid sequence of this segment plays an important role in inhibiting IFN-? production and promoting CAEV infection.In summary,we found that the DU and Vif proteins encoded by the CAEV gene can inhibit the production of IFN-? by downregulating the transcription of IFN-?,which is controlled by ISRE and NF-?B.The inhibition of IFN-? signaling pathway is located upstream of IRF3.Our results indicate that CAEV can downregulate the production of IFN-? through its encoded DU and Vif proteins,thereby escaping the innate immune response of the host cells and promoting the proliferation of the virus.