An mRNA Vaccine Based on Antigens From Conserved Regions of Monkeypox Virus A35R and M1R With a Dimer-Like Conformation Confers Protection Against Both Monkeypox Virus and Vaccinia Virus Infections in Mice.

The 2022 global mpox outbreak caused by the monkeypox virus (MPXV) has underscored the urgent need for improved vaccine development. To address this need, we developed four candidate vaccine antigens based on conserved sequences of the MPXV A35R and M1R proteins utilizing a lipid nanoparticle (LNP) delivery system. All four vaccine candidates elicited varying degrees of humoral and cellular immune responses and conferred differential protection against MPXV and vaccinia virus (VACV) in BALB/c mice; notably, the dual-antigen vaccines MV1 and MV2 induced more potent immunogenicity, including higher neutralizing antibody titers and cytokine secretion levels. However, among the four candidates, only the dual-antigen vaccines MV1 and MV2 conferred protective efficacy in AGB6 mice and reduced infection-induced pox lesion formation, indicating that antigens containing both intracellular mature virus (IMV) and extracellular enveloped virus (EEV) targets may be key to exerting robust protection. Notably, MV2-which was designed via structural truncation and recombination based on poxvirus-broad-spectrum antibodies using the AlphaFold3 prediction platform and adopts a single-chain "dimer-like" configuration-exhibited not only optimal protective efficacy but also sustained durable immune responses and protection. These findings indicate that MV2 induces favorable immunogenicity and has potential for preventing MPXV and VACV infections, supporting its promise as a clinical vaccine candidate for MPXV.