Serologic differentiation between wild-type and cell-adapted African swine fever virus infections: A novel DIVA strategy using the MGF100-1L protein.

African swine fever virus (ASFV) poses a significant threat to the global swine industry and requires improved control strategies. Here, we developed a Differentiating Infected from Vaccinated Animals (DIVA) assay based on the MGF100-1L protein, which is absent in a cell-adapted ASFV strain lacking several multigene family (MGF) genes. We analyzed seven deleted genes, including MGF genes, from the right variable region of the ASFV genome against sera from convalescent pigs. MGF100-1L showed significant reactivity and was produced as a recombinant protein for use in an enzyme-linked immunosorbent assay (ELISA). The assay, with a cut-off value of 0.284, successfully differentiated between naive and infected pigs with 100% accuracy. More importantly, pigs infected with the cell-adapted ASFV showed no significant change in ELISA readouts after 27 days post-infection. However, when these pigs were subsequently challenged with wild-type virus, MGF100-1L reactivity increased significantly by 21 days post-challenge. This study demonstrates the potential of MGF100-1L as a DIVA marker for ASFV, which offers a promising tool to distinguish between infections with wild-type ASFV and those with cell-adapted variants lacking specific MGF genes, thereby improving ASFV surveillance and control strategies.