Transient glycan shield reduction induces CD4-binding site broadly neutralizing antibodies in SHIV-infected macaques.

Broadly neutralizing antibodies (bNAbs) targeting the HIV-1 CD4-binding site (CD4bs) occur infrequently in macaques and humans and have not been reproducibly elicited in any outbred animal model. To address this challenge, we first isolated RHA10, an infection-induced rhesus bNAb with 51% breadth. The cryoelectron microscopy (cryo-EM) structure of RHA10 with the HIV-1 envelope (Env) resembled prototypic human CD4bs bNAbs with CDR-H3-dominated binding. Env-antibody co-evolution revealed transient elimination of two Env CD4bs-proximal glycans near the time of RHA10-lineage initiation, and these glycan-deficient Envs bound preferentially to early RHA10 intermediates, suggesting that glycan deletions in infecting SHIVs could induce CD4bs bNAbs. To test this hypothesis, we constructed SHIV.CH505 variants with CD4bs-proximal glycan deletions. Infection of 11 macaques resulted in accelerated CD4bs bNAb responses in 9 compared with 1 of 115 control macaques. Glycan hole-based immunofocusing coupled to Env-Ab co-evolution can consistently induce broad CD4bs responses in macaques and serve as a model for HIV vaccine design.