Lipid nanoparticle-encapsulated DNA vaccine encoding African swine fever virus p54 antigen elicits robust immune responses in pigs

African swine fever virus (ASFV) is one of the most significant viral pathogens affecting swine production worldwide. While several live attenuated ASF vaccines have been approved for clinical application in certain countries, there is a concern that the vaccine viruses might revert to virulence. Subunit vaccines containing one or a few viral immunogens provide a safer alternative. DNA plasmids are highly stable, easy to produce in large quantities at low cost, and safe for use in animals. However, unencapsulated DNA vaccines often exhibited low immunogenicity, largely due to the inefficient cellular entry of the plasmid DNA, leading to low protein expression. In this study, we used ASFV p54 as a model antigen to investigate the feasibility of using lipid nanoparticles (LNP) as nanocarriers to enhance the immunogenicity of DNA vaccines. Pigs immunized with the p54 LNP-DNA vaccine elicited high titers of p54-specific antibodies and T-cell responses after the second immunization. Using ELISAs based on an overlapping peptide library, we identified three antigenic areas within p54. Additionally, we noted that pigs vaccinated with the p54 LNP-DNA vaccine exhibited a similar antibody profile as those vaccinated with an experimental live attenuated vaccine or infected with a wild-type ASFV strain. The results highlight the promising potential of LNP-DNA as an effective platform for developing gene-based vaccines against ASFV.