Ashurov, A.; Hoffmann, K.; Ramamohan, A. R.; Karthigeyan, K. P.; Ashurov, A.; Rotzler, M.; Kohl, A.-K.; Torres, G. M.; Binuya, C.; Williams, C.; Crooks, C. M.; Schlachter, L.; Shestopal, D.; Ullrich, L.; Hornung, C.; Lotfi, R.; Kolb, P.; Kreer, C.; Koch, M.; Permar, S. R.; Hengel, H.; McLellan, J. S.; Klein, F.; Zehner, M.

Humoral immune mechanisms that may reduce HCMV disease include neutralizing antibodies that block viral entry and Fc-mediated effector functions that can promote the elimination of infected cells. Here, we identify the gH/UL116 envelope complex as a naturally immunogenic target that elicits antibodies capable of mediating both of these immune mechanisms. Using single-cell sorting of antigen-specific human memory B cells, we isolated gH/UL116-reactive monoclonal antibodies from HCMV-seropositive donors. Epitope mapping linked distinct antibody binding sites to specific functional profiles, showing that gH binding was required for virus neutralization, whereas UL116 targeting was associated with potent and broad Fc{gamma} receptor (Fc{gamma}R) activation. Furthermore, cryo-electron microscopy provided high-resolution structures of UL116-specific antibodies, revealing their modes of binding to the gH/UL116 complex. In mice, gH/UL116 immunization elicited serum IgG responses with binding titers that strongly correlated with both neutralization and mouse Fc{gamma}R activation. Together, these findings provide an epitope-level map linking antibody specificity to neutralization and Fc{gamma}R activation across HCMV gH-associated complexes and position gH/UL116 as a promising HCMV vaccine candidate.