HIV-1 vaccine design through minimizing envelope metastability

Overcoming envelope metastability is crucial to trimer-based HIV-1 vaccine design. Here, we present a coherent vaccine strategy by minimizing metastability. For 10 strains across five clades, we demonstrate that the gp41 ectodomain (gp41(ETCO)) is the main source of envelope metastability by replacing wild-type gp41(ECTO) with BG505 gp41(ECTO) of the uncleaved prefusion-optimized (UFO) design. These gp41(ECTO)-swapped trimers can be produced in CHO cells with high yield and high purity. The crystal structure of a gp41(ECTO)-swapped trimer elucidates how a neutralization-resistant tier 3 virus evades antibody recognition of the V2 apex. UFO trimers of transmitted/ founder viruses and UFO trimers containing a consensus-based ancestral gp41(ECTO) suggest an evolutionary root of metastability. The gp41(ECTO)-stabilized trimers can be readily displayed on 24- and 60-meric nanoparticles, with incorporation of additional T cell help illustrated for a hyperstable 60-mer, I3-01. In mice and rabbits, these gp140 nanoparticles induced tier 2 neutralizing antibody responses more effectively than soluble trimers.