Investigating N332-glycan independent V3-glycan antibodies as novel targets for HIV-1 vaccine design

About This Grant

PROJECT SUMMARY / ABSTRACT A vaccine that elicits broadly neutralizing antibodies (bNAbs) against the Envelope (Env) protein of HIV-1 would be the best approach to end the AIDS epidemic; however, no efficacious vaccine has been developed to date. bNAbs targeting the conserved V3-glycan epitope of Env such as PGT121, 10-1074 and BG18 bind to the conserved GDIR motif of Env and to a key glycan at position N332 (N332 glycan). The absence of the N332 glycan in multiple HIV-1 strains limits the neutralization breadth of these bNAbs to ~60-70%. Based on observations by us and others, we hypothesized that V3-glycan antibodies that do not require the N332-glycan for binding can be elicited and matured into bNAbs by vaccination. We further hypothesized that N332-glycan independent V3-glycan antibodies will have greater neutralization breadth and that immunotherapies combining N332-glycan dependent and independent bNAbs will impose strong restrictions to viral escape, resulting in longer periods of suppressed viremia. To test these hypotheses, we developed WIN332, an Env-based immunogen that lacks the N332-glycan. Immunization with WIN332 in nonhuman primates (NHPs) induced a new class of N332-glycan independent V3-glycan antibodies. Most importantly, WIN332 elicited N332-glycan independent neutralizing antibodies to the V3-glycan epitope as early as three weeks after a single immunization. Our studies established a new classification of V3-glycan antibodies into Type-I (N332-glycan dependent) and Type-II (N332-glycan independent) and presented WIN332 as a promising vaccine candidate to streamline bNAb development (Relano et al, Nat.Immunol. in press). Further supporting our overarching hypothesis and this proposal, now two Type-II human bNAbs that target the V3-glycan epitope in a N332-glycan independent manner, EPTC112 and 007, have been reported, demonstrating that Type-II lineages can develop in humans and are a significant target for vaccine design. In this proposal, we will build on these studies and leverage WIN332 to investigate the new class of Type-II V3-glycan antibodies and its potential as a novel target for vaccine and immunotherapy design. In Aim 1, we will leverage WIN332 as a probe to isolate new Type-II bNAbs and bNAb precursors from infants and adults living with HIV-1 and from healthy donors respectively. We will characterize the newly isolated Type-II bNAbs and evaluate their capacity to increase neutralization coverage and restrict viral escape. In Aim 2, we will use our state-of-the-art methodology to produce new immunoglobulin knockin (Ig KI) mice that express unmutated precursors of human and NHP Type-II bNAbs and use these mice to investigate the maturation pathways of these bNAbs. Through advanced protein engineering approaches, structural studies and assessment in humanized mice, we will design novel vaccination strategies to mature N332-glycan independent lineages. We expect our innovative vision of the V3-glycan epitope will enable the identification and characterization of previously overlooked bNAb lineages of potential clinical value and will result in new immunization protocols to streamline bNAb development.