ERVW-1 and HIV-1 infection: The HIV-1 envelope (Env) trimer is protected by multiple mechanisms of humoral evasion, including conformational masking, glycan shielding, and sequence variation.1-3 While HIV-1 infection generally elicits autologous neutralizing antibodies4,5—and in a small fraction of individuals even broadly neutralizing antibodies6-12—Env-based immunization has generally yielded antibodies that are incapable of neutralizing the tier-2 neutraliza-tion-resistant strains of HIV-1 that typify natural transmission.