Evaluation of the Pathogenesis and Virulence of Highly Virulent Eurasian Genotype Ⅱ African Swine Fever Virus with MGF505-2R Gene Deletion in Piglets

Background: African swine fever virus (ASFV) poses a significant threat to the global pig industry due to its high mortality rates and complex genetic variation. Live attenuated vaccines (LAVs) have shown promise in providing protection against ASFV. In our previous study, MGF505-2R was identified as a potent inhibitor of innate immunity in vitro. This study evaluates the pathogenesis and virulence of a recombinant Eurasian genotype 2 strain with the MGF505-2R gene deleted (ASFV-ΔMGF505-2R) in piglets. Methods: Twelve clinically healthy five-week-old crossbred pigs were divided into three groups and inoculated with either ASFV-ΔMGF505-2R, ASFV CN/GS 2018, or PBS. Clinical symptoms, viral loads, and immune responses were monitored over 30 days. Results: ASFV-ΔMGF505-2R-inoculated piglets exhibited transient fever and significantly lower viral loads compared to those inoculated with ASFV CN/GS 2018. Histopathological analysis revealed milder tissue damage in the ASFV-ΔMGF505-2R group. ELISA analysis indicated higher levels of IFN-β and IL-1β, and all ASFV-ΔMGF505-2R-inoculated piglets developed high titers of ASFV-specific antibodies. Conclusions: These findings suggest that deletion of the MGF505-2R gene attenuates ASFV virulence and enhances the host immune response, supporting the potential of ASFV-ΔMGF505-2R as a live attenuated vaccine candidate.