Epstein-Barr virus gp350 neutralizing epitopes define distinct sites of vulnerability.

Epstein-Barr virus (EBV) is a widespread human herpesvirus linked to several malignancies, yet no vaccine has been approved. Its major surface glycoprotein, gp350, mediates attachment to B cells via CR2 binding, but gp350-based vaccines have shown limited protection, raising questions about its neutralizing epitopes and mechanisms. Here, we isolated human monoclonal antibodies from a phage-display library derived from EBV-seropositive donors. Several antibodies showed potent neutralization, including 1A12, which conferred robust protection in a humanized mouse model by markedly reducing viral load and disease pathology. Epitope mapping and structural analysis revealed three distinct antigenic clusters on gp350, including a neutralizing epitope in the distal D3 domain recognized by 1H5, which neutralizes EBV via a post-attachment mechanism. These findings define vulnerable sites on gp350 and offer structural and mechanistic insights for developing next-generation EBV vaccines and antibody-based therapies.