Mechanism Of Antagonism Of Host CGAS-STING Signaling Pathway By African Swine Fever Virus-Encoded MGF360-13L And MGF505-3R Proteins

African Swine Fever Virus（ASFV）is a complex icosahedral DNA virus with a large genome encoding numerous functional proteins that evade the host immune system,resulting in no effective control method being developed.Therefore,it is crucial to dissect the mechanism of ASFV protein-induced immune escape.The cGAS-STING-mediated Type I Interferon（IFN-Ⅰ）signaling pathway is important for the body’s resistance to DNA virus infection.Numerous studies have shown that the ASFV-encoded proteins function to escape the IFN-Ⅰ immune response,and therefore the identification and exploration of the mechanism of action of these proteins is essential for the development of an African swine fever vaccine.It was shown that ASFV MGF360-13L inhibited cGAS-STING-mediated IFN-βand ISRE reporter gene activity,but not My D88-mediated NF-κB reporter gene activity.ASFV MGF360-13L was found to suppress the m RNA levels of IFN-β1 and ISG56by q PCR analysis.Mechanistically,ASFV MGF360-13L was able to degrade STING protein,and by adding inhibitors 3-MA and NH₄Cl it was shown that ASFV MGF360-13L degraded STING through the autophagic pathway.This study initially revealed the mechanism of action of ASFV MGF360-13L in antagonizing the IFN-Ⅰ signaling axis by targeting STING,and also suggested that It also suggests that ASFV may promote the autophagic pathway to evade host IFN-Ⅰ response,which provides a theoretical basis for the development of anti-ASFV vaccines.Studies have shown that ASFV-encoded proteins are an important factor in host immunity.In this study,we identified a negative regulator MGF505-3R,which significantly down-regulated cGAS/STING-and poly（d G:d C）-mediated IFN-βand interferon-stimulated response element（ISRE）reporter gene activity and suppressed IFN-β1 and IFIT2 m RNA levels.In addition TBK1,IRF3 and IκBαphosphorylation levels were also inhibited.Mechanistically,MGF505-3R interacted with cGAS/TBK1/IRF3 and targeted TBK1 for degradation,thereby disrupting the cGAS-STING-mediated IFN-βsignaling pathway,which appears to be highly correlated with autophagy.Knockdown of MGF505-3R expression enhanced the production of IFN-βand IL-1β.In conclusion,our study reveals a negative regulatory mechanism involving the MGF505-3R-cGAS-STING axis and provides insights into evasion strategies involving autophagy and innate signaling pathways employed by ASFV.In this study,we assessed the role of MGF505-3R,MGF360-13L genes in viral replication in cell cultures and in experimental infection in pigs.In the current study,we demonstrated that ASFV MGF505-3R,MGF360-13L is a negative regulator of the cGAS-STING DNA-sensing pathway,which controls IFN-βproduction.Mechanistically,ASFV MGF505-3R interacted with TBK1 and attenuated TBK1expression via autophagy,and ASFV MGF360-13L antagonized the IFN-Ⅰ signaling axis by targeting STING.Our findings reveal a protein that contributes to the evasion of innate immunity by ASFV and provide new theoretical support for the development of future attenuated ASFV vaccines.