CD4 and infection: Several previous reports have investigated the role of disulfides and native redox enzymes in the Env-mediated infection process, including modulating CD4’s D2 structure and membrane localization (7, 9, 14) and interactions with the Env/CD4–coreceptor complex (12, 47, –, 49), while their targeted inhibition can prevent successful infection by the virus (7, 13, 48).