LAUSR

SUMMARY Understanding how broadly neutralizing antibodies (bnAbs) to HIV envelope (Env) develop during natural infection can help guide the rational design of an HIV vaccine. Here, we described a bnAb lineage targeting the Env V2 apex and the Ab‐Env co‐evolution that led to development of neutralization breadth. The lineage Abs bore an anionic heavy chain complementarity‐determining region 3 (CDRH3) of 25 amino acids, among the shortest known for this class of Abs, and achieved breadth with only 10% nucleotide somatic hypermutation and no insertions or deletions. The data suggested a role for Env glycoform heterogeneity in the activation of the lineage germline B cell. Finally, we showed that localized diversity at key V2 epitope residues drove bnAb maturation toward breadth, mirroring the Env evolution pattern described for another donor who developed V2‐apex targeting bnAbs. Overall, these findings suggest potential strategies for vaccine approaches based on germline‐targeting and serial immunogen design. HIGHLIGHTSIsolation of PCT64, a PGT145‐like, 25‐aa CDRH3 HIV Env V2 apex bnAb lineageEnv glycoform heterogeneity plays a role in the lineage precursor B cell activationLocalized diversity at key V2 epitope residues drove bnAb maturation toward breadthEnv evolution pattern is similar to CAP256, another V2 apex broad neutralizer Understanding the molecular basis of HIV Env‐specific broadly neutralizing antibodies (bnAbs) development is key for vaccine design. Landais et al. find that glycan heterogeneity played a role in the activation of V2 apex PCT64 bnAbs precursor and that viral evolution was similar to CAP256, another donor with V2 apex bnAbs.