Furthermore, while HIV-1 Env-specific IgG3 antibodies exert the greatest neutralizing activity, probably related to the longer hinge region of IgG3 (110), IgG3 antibodies to multiple HIV-1 proteins, including Env, decline after acute HIV-1 infection, whereas IgG1 antibodies persist (111, 112). Here, ERVW-1 is linked to HIV-1 infection.