Anti-V2 Antibodies Virus Vulnerability Revealed by Envelope V1 Deletion in HIV Vaccine Candidates

The efficacy of ALVAC-based HIV and SIV vaccines in humans and macaques correlates with antibodies to envelope variable region 2 (V2). We show here that vaccine-induced antibodies to SIV variable region 1 (V1) inhibit anti-V2 antibody mediated cytotoxicity and reverse their ability to block V2 peptide interaction with the α4β7 integrin receptor. SIV vaccines engineered to delete V1 and favor an a-helix, rather than a β-sheet V2 conformation,...