HIV broadly neutralizing antibodies with enhanced Fc-CD16 affinity increase NK cell ADCC even with limited envelope binding

Abstract

The persistence of latent HIV-1 reservoirs remains the primary barrier to a cure. Shock and kill strategies aim to reactivate these reservoirs and eliminate them via effector cells, such as Natural Killer (NK) cells. However, chronic infection leaves NK cells exhausted. In this study, we investigated the interplay between cytokine-mediated NK cell activation and antibody-dependent cellular cytotoxicity (ADCC) across diverse HIV-1 subtypes. We demonstrated that while cytokine stimulation enhanced natural cytotoxicity, it simultaneously induces shedding of the Fc receptor CD16 via the metalloproteinase enzyme ADAM17. However, restoring CD16 expression through ADAM17 inhibition (TAPI-1) did not improve ADCC, suggesting that CD16 surface levels in NK cells is not the only limiting factor. On the other hand, Fc-engineered broadly neutralizing antibodies (bNAbs) with increased CD16 affinity, in particular LPLIL and GASDALIE, significantly enhance ADCC across the six different HIV-1 subtypes, regardless of NK cells activation, CD16 downregulation or limited surface Envelope expression in CD4T cells. These findings suggest that enhancing receptor affinity of bNAbs can bypass viral immune evasion and NK cell exhaustion, supporting their potential incorporation into HIV cure strategies. ImportanceEradicating latent HIV reservoirs remains a global health priority, as it would liberate millions of people living with HIV (PLWH) from the economic and physiological burdens of lifelong antiretroviral therapy (ART). By utilizing a primary human cell model that resembles in vivo conditions across diverse viral strains, we identified that simply preventing CD16 receptor shedding from NK cells is insufficient to improve HIV-1 clearance. Instead, we demonstrated that enhancing the binding of antibodies to the CD16 receptor enables NK cells to overcome viral immune evasion and the loss of CD16 expression. This allows for potent elimination of infected cells through antibody-dependent cellular cytotoxicity (ADCC). These findings provide a clear strategy for designing more effective "kill" components in future therapeutic strategies.