Background/Objectives: African swine fever (ASF) is a disease of domestic pigs and wild boar caused by African swine fever virus (ASFV), in which infection often leads to high morbidity and mortality. Although subunit and mRNA vaccines based on protective antigens have been explored for ASFV, their protective efficacy remains insufficient for practical ASF control, highlighting the need to identify new potential antigens capable of inducing more potent and broadly protective immune responses. Previously, we found that the antibodies against the ASFV E120R protein (pE120R) could significantly inhibit virus replication in primary porcine alveolar macrophages (PAMs). However, it is not yet known whether anti-pE120R antibodies can induce antibody-dependent cellular cytotoxicity (ADCC). Methods: In this study, we analyzed the conservation and immunogenic features of pE120R and established an HEK293T cell line with stable expression of pE120R as target cells (HEK293T-pE120R). Additionally, a co-culture system comprising target cells and peripheral blood mononuclear cells (PBMCs) was established to evaluate the ability of the anti-pE120R antibodies to induce ADCC as measured by lactate dehydrogenase (LDH) release assays. Results: The results showed that pE120R is highly conserved among different ASFV genotypes and contains multiple B-cell and T-cell epitopes. Importantly, LDH release assays demonstrated that anti-pE120R antibodies triggered NK cell-mediated ADCC. Notably, ASFV replication in HEK293T-pE120R cells was not promoted. Conclusions: In summary, pE120R was associated with antibody production in a cytotoxicity assay. The ability of this antigen to induce protective immunity, if any, requires further evaluation in vivo.

Keywords: African swine fever; African swine fever virus; E120R protein; antibodies; antibody-dependent cellular cytotoxicity.