HIV-1 CD4-binding site germline antibody–Env structures inform vaccine design

Abstract

BG24, a VRC01-class broadly neutralizing antibody (bNAb) against HIV-1 Env with relatively few somatic hypermutations (SHMs), represents a promising target for vaccine strategies to elicit CD4-binding site (CD4bs) bNAbs. To understand how SHMs correlate with BG24 neutralization of HIV-1, we solved 4.1 Å and 3.4 Å single-particle cryo-EM structures of two inferred germline (iGL) BG24 precursors complexed with engineered Env-based immunogens lacking CD4bs N-glycans. Structures revealed critical Env contacts by BG24iGL and identified antibody light chain structural features that impede Env recognition. In addition, biochemical data and cryo-EM structures of BG24iGL variants bound to Envs with CD4bs glycans present provided insights into N-glycan accommodation, including structural modes of light chain adaptations in the presence of the N276gp120 glycan.