Antigen-agnostic identification of poxvirus broadly neutralizing antibodies targeting OPG153

Recurrent mpox outbreaks caused by the monkeypox virus (MPXV) have prompted the World Health Organization to declare a Public Health Emergency of International Concern and have stimulated the development of medical interventions. Here, we used antigen-agnostic identification of MPXV-neutralizing monoclonal antibodies from convalescent or vaccinated people, AlphaFold 3–based predictive modeling, and cryo–electron microscopy to identify the protein encoded by orthopoxviral gene (OPG) 153 (MPXV A28) as a target of broadly neutralizing antibodies. OPG153-targeting antibodies neutralized MPXV clades Ib and IIb and vaccinia virus (VACV) and cross-reacted with OPG153 orthologs from cowpox and variola viruses. Immunization with MPXV OPG153 elicited a potent neutralizing antibody response against MPXV and VACV in mice, substantiating OPG153 as both a promising vaccine antigen and a potent target for preventive and therapeutic antibodies.