The deletion of the EP402R and MGF505/360 genes attenuates a genotype I/II recombinant ASFV but fails to confer complete protection against homologous or genotype II challenge in pigs.

Abstract

African swine fever (ASF), a pig disease caused by ASFV, is highly contagious and often lethal. The recent emergence of novel ASFV with I/II genomic recombination has posed significant challenges to global ASF prevention and control. In this study, we used the Chinese I/II genomic recombinant virulent strain ASFV-HN10005 (ASFV-HN) to construct two gene-deleted viruses. ASFV-HNΔMGF lacks the-genes cluster (including, and), and ASFV-HNΔCD2vΔMGF lacks bothand the-genes cluster. ASFV-HNΔMGF still showed pathogenicity in domestic pigs, while ASFV-HNΔCD2vΔMGF showed markedly attenuated virulence, with all inoculated pigs surviving. However, these pigs did not gain complete protection against subsequent lethal challenge from the parental ASFV-HN strain or the virulent II-type strain ASFV-GZ. This implies that I/II genomic recombinant ASFV may have unique biological traits and immune evasion mechanisms. Our findings indicate the need to reassess current ASFV control strategies and provide a basis for future vaccine target selection.