Rapid elicitation of neutralizing Asn332-glycan-independent antibodies to the V3-glycan epitope of HIV-1 Env in nonhuman primates

Sequential immunization is a promising approach to elicit broadly neutralizing antibodies (bNAbs) against the HIV-1 Envelope (Env). However, available protocols are inefficient and involve multiple immunizations over long periods of time. Here, we present WIN332, a new engineered Env immunogen that induces a new class of Asn332-glycan-independent antibodies to the conserved V3-glycan epitope of Env with low inhibitory activity indicative of a neutralization activity after a single bolus immunization in nonhuman primates. WIN332 binds to precursors of canonical human Asn332-glycan-dependent (type-I) V3-glycan bNAbs but also of a first-of-its-class Asn332-glycan-independent (type-II) V3-glycan bNAb. A single immunization elicits low inhibitory serum and monoclonal antibodies that are boosted and affinity matured with a heterologous immunogen. Electron microscopy polyclonal epitope mapping analysis of serum antibodies, antibody cloning and cryogenic electron microscopy analysis reveals that WIN332 elicits Asn332-glycan-independent antibodies with striking sequence and binding similarities with the most potent human type-I and type-II V3-glycan bNAbs. Thus, WIN332 is a promising vaccine candidate to streamline V3-glycan bNAb elicitation.