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

SUMMARY 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 germline-targeting trimer immunogen Q23-APEX-GT2 that primes diverse V2-apex bnAb precursors. Q23-APEX-GT2 efficiently activated V2-apex-specific B cells in humanized knock-in mice and consistently elicited immunofocused antibody responses in rhesus macaques, priming multiple long CDRH3-loop bnAb-B cell lineages. Monoclonal antibodies from immunized macaques exhibited broad heterologous HIV trimer binding and cross-neutralization. Atomic-level structural studies confirmed precise epitope targeting and revealed CDRH3-paratope configurations that mirrored those of human V2-apex bnAbs. This study provides proof-of-principle for successful priming and maturation of authentic V2-apex bnAb precursors in outbred macaques, underscoring the potential of V2-apex-targeted vaccines. HIGHLIGHTS Engineered Q23-APEX-GT2 trimer to stimulate diverse V2-apex bnAb B cell precursors Q23-APEX-GT2 primed rare V2-apex bnAb B cells in mice and outbred rhesus macaques Q23-APEX-GT2 elicited immunofocused antibody responses and diverse V2-apex B cell lineages with desirable long-CDRH3 paratope properties Q23-APEX-GT2 alone induced V2-apex antibodies with broad HIV trimer binding and modest neutralization breadth Structural analysis confirmed bnAb site targeting, mirroring human and rhesus V2-apex bnAbs