Recombinant vaccinia vectored ASFV vaccine enhances swine survival against genotype II challenge

The African Swine Fever Virus (ASFV) poses a major threat to global livestock production by infecting both domestic and wild pigs, causing significant economic loss. Despite promising protective results observed with live attenuated viruses, the safety concern blocked its extensive application. In this study, we developed a novel vaccine combining two recombinant vaccinia viruses-rTTV-D-A and rTTV-K-J-that together express eight ASFV genes, including EP402R (CD2v), B646L (p72), B602L (pB602L), D117L (p17), H240R (pH240R), B438L (p49), E183L (p54), CP204L (p30), and a synthetic T antigen composed of conserved T cell epitopes from multiple ASFV proteins, aiming to induce both humoral and T-cell immune responses against different viral antigens. After demonstrating that this vaccine induced antigen-specific humoral and cellular responses in both mice and swine, its protective efficacy in swine was examined using a lethal challenge model. The vaccinated pigs showed a promising protection against the lethal challenge of a virulent genotype II ASFV strain (100 HAD₅₀/pig), with 4 out of 6 surviving, while all control animals succumbed from 9 to 15 days post challenge. Importantly, the protection was further evidenced by the recovery to normal temperature and no ASFV infection-related clinical signs or virus shedding in surviving pigs over a 21-day observation period. Our results support the potential of rTTV-D-A and rTTV-K-J as a novel multi-immunogen vaccinia-vectored ASFV vaccine. Further studies are warranted to explore and improve its use as a standalone vaccine or in combination with other vaccine platforms to achieve broad and effective protection against ASFV.