Biological significance of the antibody response to HIV antigens expressed on the cell surface.

Human antibodies to HIV antigens expressed on the surface of infected cells may inhibit cell fusion with uninfected CD 4-positive cells and mediate killing of the infected cells by effector cells bearing the Fc receptor. Sequential sera from ten HIV-antibody seroconverted men, of which five progressed to ARC or AIDS (CDC stage IV) during the follow-up period of two years, were tested for the ability to inhibit CD 4-dependent cell fusion, (CFI) and to mediate antibody-dependent cellular cytotoxicity (ADCC). Nine patients developed HIV-specific ADCC and seven CFI-antibodies using the HIV strain HTLV-IIIB as target antigen. These antibodies appeared approximately at the same time 2-12 months after primary infection, defined as antibody seroconversion or antigenaemia. ADCC antibodies were detectable at higher titers as compared to CFI-antibodies. All sera of asymptomatic individuals (CDC stage II and III) were CFI antibody positive and had a higher mean ADCC titer as compared to sera from patients progressing to AIDS or ARC. ADCC and CFI antibodies coincided in some cases in the complete absence of core antibodies. Because the relationship between ADCC and CFI was not exclusive it is concluded that distinct domains of the HIV envelope induce natural antibodies mediating ADCC and CFI.