Structure-based design of native-like HIV-1 envelope trimers to silence non-neutralizing epitopes and eliminate CD4 binding.

Elicitation of broadly neutralizing antibodies (bnAbs) is a primary HIV vaccine goal. Native-like trimers mimicking virion-associated spikes present nearly all bnAb epitopes and are therefore promising vaccine antigens. However， first generation native-like trimers expose epitopes for non-neutralizing antibodies (non-nAbs)， which may hinder bnAb induction. We here employ computational and structure-guided design to develop improved native-like trimers that reduce exposure of non-nAb epitopes in the V3-loop and trimer base， minimize both CD4 reactivity and CD4-induced non-nAb epitope exposure， and increase thermal stability while maintaining bnAb antigenicity. In rabbit immunizations with native-like trimers of the 327c isolate， improved trimers suppress elicitation of V3-directed and tier-1 neutralizing antibodies and induce robust autologous tier-2 neutralization， unlike a first-generation trimer. The improved native-like trimers from diverse HIV isolates， and the design methods， have promise to assist in the development of a HIV vaccine.