Germline-targeting HIV immunogen induces cross-neutralizing antibodies in outbred macaques

Germline targeting (GT) is a promising strategy to activate rare broadly neutralizing antibody (bnAb)-producing B cells against HIV, but induction of such responses in outbred animals has not been achieved. Using antibody-guided structure-based design, we engineered a GT HIV trimer immunogen, Q23-APEX-GT2, which primes diverse V2-apex bnAb precursors. Q23-APEX-GT2 efficiently activated rare V2-apex-specific B cells in humanized knockin mice and consistently elicited immunofocused antibody responses in outbred rhesus macaques, priming multiple long heavy-chain complementarity-determining region 3 (CDRH3)-loop bnAb-B cell lineages. Monoclonal antibodies isolated from immunized macaques showed broad heterologous HIV trimer recognition and modest cross-neutralization of diverse tier-2 viruses. Cryoelectron microscopy (cryo-EM) structural studies confirmed precise epitope targeting and revealed CDRH3-mediated binding modes that mirrored those of human V2-apex bnAbs. Together, these findings establish proof of principle for priming and early maturation of authentic V2-apex bnAb precursors in outbred macaques and highlight the promise of V2-apex-targeted HIV vaccines.