MGF110-2L deletion prevents IFN-I and inflammatory response, resulting in partial attenuation and protection against virulent ASFV

ABSTRACT African swine fever virus (ASFV) encodes numerous multigene family (MGF) proteins whose individual contributions to virulence and immune modulation remain poorly understood. Here, we characterize the role of MGF110-2L in shaping innate immunity and disease outcome in vivo . Deletion of MGF110-2L from the virulent Arm/07/CBM/c2 isolate markedly attenuated clinical disease and conferred complete protection against homologous challenge. In macrophages, the MGF110-2L-deficient recombinant induced enhanced type I interferon (IFN) responses, consistent with a role for MGF110-2L in antagonizing antiviral signaling. However, transcriptomic profiling of peripheral blood mononuclear cells revealed that the absence of MGF110-2L prevents the excessive IFN and inflammatory hyperactivation triggered by the parental virus in vivo , establishing a controlled antiviral program associated with reduced pathology. These findings identify MGF110-2L as a functional virulence factor that drives dysregulated innate immune responses during ASFV infection. Our work advances the molecular understanding of ASFV-host interactions and highlights the contribution of MGF110-2L protein to immune evasion and pathogenesis. IMPORTANCE Finding safe and effective vaccines is essential to impair the spread of African swine fever virus (ASFV), responsible for the largest animal pandemic. Identifying ASFV virulence factors and understanding the mechanisms of pathogenesis and protection are crucial. By using RNAseq from in vivo peripheral blood mononuclear cells, together with immunological studies, we showed that MGF110-2L regulates type I IFN production and cytokine storm in pigs. Deletion of the MGF110-2L gene results in attenuation and induces protection against the parental virulent strain. These results support the induction of an alert immune state together with dampened systemic inflammation but preserved cytotoxic readiness in vaccinated animals. Altogether, our data shed light on the mechanisms underlying protection against ASFV and contribute to the development of new protective tools.