Multivalent mpox protein nanoparticle vaccines confer cross-protection against orthopoxvirus infection

The outbreak of mpox since 2022 has driven the development of mpox virus (MPXV)-specific, subunit-based, next-generation vaccines, instead of the currently used live-attenuated vaccinia virus (VACV) vaccines. Here, we describe a self-assembling protein nanoparticle against MPXV using lumazine synthase to present viral surface proteins. Multivalent nanoparticles elicited broader and stronger immune responses against MPXV and provided superior heterologous protection in rodent models against lethal VACV challenges compared to monovalent formulations. The three antigens with the best protective efficacy (intracellular mature virus antigens M1 and E8, and extracellular enveloped virus antigen B6) were further combined as the trivalent cocktail or mosaic nanoparticle. The trivalent nanoparticles elicited higher humoral responses compared to the modified vaccinia virus Ankara, and were protective against lethal VACV challenge in mice, with the protection correlation revealed. These findings highlight the potential of multivalent nanoparticle as vaccines against MPXV and other orthopoxviruses.