B cell response to HCMV gH/UL116 elicits neutralizing and FcγR-activating antibodies

Abstract

Humoral immune mechanisms that can contribute to limiting HCMV disease include neutralizing antibodies that block viral entry and Fc-mediated effector functions that promote 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 memory B cells, we isolated gH/UL116-reactive monoclonal antibodies from HCMV-seropositive donors. Epitope mapping showed 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 revealing how UL116-specific antibodies bind gH/UL116. In mice, gH/UL116 immunization elicited serum IgG responses whose binding titers 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.