Foot-and-mouth disease (FMD) poses a significant threat to global livestock industries due to its high viral contagiousness. Despite inactivated viral vaccines remaining effective, their production requires stringent biocontainment and faces limitations in stability and cross-serotype immunogenicity. Here, we developed a novel bivalent mRNA@LNP vaccine targeting FMDV serotypes A and O. The design incorporated optimized immunodominant epitopes from the VP1 protein, combined with a conserved T-cell epitope from 3A non-structural protein. We validated antigen expression in vitro and evaluated the immunogenicity of mRNA@LNP in mice. It elicited faster early immune activation and stronger humoral and cellular immune responses than the inactivated virus vaccine. Throughout the entire immunization period, the antibody levels induced by 5 μg mRNA@LNP were consistently equivalent to those of the 5 μg inactivated vaccine. Furthermore, the immune efficacy of the 10 μg mRNA dose following the booster vaccination was consistent to that of the ISA 206-adjuvanted inactivated vaccine. Liquid-blocking ELISA indicated that immunization of the mRNA@LNP induced strong blocking antibody titers against both serotype A(titer>256 at 5 μg) and serotype O(titer>128 at 10 μg). Antibody isotyping (high IgG2a/IgG1 ratio) and cytokine profiling (high IFN-γ) revealed a pronounced Th1-skewed immune response, consistent with enhanced GC B cell activation and CTL activation. In contrast, the ISA-206 adjuvanted vaccine induced a weaker cellular immune response and a more Th2-biased profile, highlighting the capacity of the mRNA vaccine to achieve not only comparable humoral immunogenicity to inactivated vaccines but also a more balanced and robust cellular immunity. These findings support mRNA vaccines as a promising, virus-free platform for multivalent FMD vaccines, offering potential solutions to current limitations and providing broader protection against FMDV outbreaks.
