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

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Abstract
African swine fever virus (ASFV) poses a significant threat to the global pig industry due to high mortality rates and complex genetic variation. Live attenuated vaccines (LAVs) provide protection against ASFV. Previously, MGF505-2R was identified as a potent inhibitor of innate immunity in vitro. This study evaluates the pathogenicity of a recombinant Eurasian genotype II strain with the MGF505-2R gene deleted (ASFV-ΔMGF505-2R) in piglets. Twelve five-week-old crossbred piglets were divided into two groups, with one group of eight piglets inoculated with ASFV-ΔMGF505-2R (n = 8) and the other group of four piglets inoculated with the same dose of parental ASFV CN/GS 2018 (n = 4). Clinical symptoms, viral loads, and immune responses were monitored over 30 days. ASFV-ΔMGF505-2R-inoculated piglets exhibited transient fever and low viremia only in the beginning of the challenge, while the control group developed high levels of viremia and hyperthermia at day 2 and 8 post-challenge, respectively. Meanwhile, the control group demonstrated more severe post-mortem signs and immuno-histochemistry injury when compared to the ΔMGF505-2R group. ELISA analysis displayed higher levels of IFN-β and IL-1β in the ΔMGF505-2R group, further solidating the immunosuppressive role of MGF505-2R. All ASFV-ΔMGF505-2R-inoculated piglets developed high titers of ASFV-specific P30 antibodies at 10 days post-challenge. These findings rationalized the potential of ASFV-ΔMGF505-2R as a live attenuated candidate for ASF infection.
Funding Information
  • open competition program of top ten critical priorities of Agricultural Science and Technology Innovation for the 14th Five-Year Plan of Guangdong Province (2024KJ14)
  • National Key Research and Development Program of China (2021YFD1800100)
  • Fundamental Research Funds for the Central Universities, China Agriculture Research System of Ministry of Finance and Ministry of Agriculture and Rural Affairs (CARS-35)
  • Project of National Center of Technology Innovation for Pigs (NCTIP-XD/C03)
  • Innovation Program of Chinese Academy of Agricultural Sciences (CAAS-CSLPDCP-202302, CAAS-ASTIP-2024-LVRI)
  • Science and Technology Program of Gansu Province (24JRRA01)

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