Vaccine induction of broadly neutralizing antibodies (bnAbs) to human immunodeficiency virus (HIV) remains a major challenge. Germline-targeting immunogens hold promise for initiating the induction of certain bnAb classes; yet for most bnAbs, a strong dependence on antibody heavy chain complementarity determining region 3 (HCDR3) is a major barrier. Exploiting ultra-deep human antibody sequencing data, we identified a diverse set of potential antibody precursors for a bnAb with dominant HCDR3 contacts. We then developed HIV envelope trimer-based immunogens that primed responses from rare bnAb-precursor B cells in a mouse model, and in ex-vivo screens bound a range of potential bnAb-precursor human naive B cells. Our repertoire-guided germline-targeting approach provides a framework for priming the induction of many HIV bnAbs, and could be applied to most HCDR3-dominant antibodies from other pathogens.
