Presence of IgM antibodies which sensitize HIV-1-infected cells to cytolysis by homologous complement in long-term survivors of HIV infection.

Although human cells are resistant to homologous human complement due to the presence of species-specific membrane inhibitors, a naturally occurring IgM antibody which recognizes an asialo-oligosaccharide can sensitize HIV-1-infected cells for complement-mediated cytolysis. Therefore, we investigated whether long-term survivors of HIV-1 infection harbor such antibodies in their sera. Thirty of 31 sera from HIV-1 seropositive hemophilia patients who have survived HIV-1 infection 10 years or more showed appreciable cytolytic activity, while only 2 sera of 10 seropositive patients presumed to have been infected with HIV-1 (due to sexual contact) more recently showed cytolytic activity. On the other hand, only 7 out of 43 sera from seronegative hemophilia patients showed cytolytic activity. Immunofluorescence staining for IgM on HIV-1-infected cells essentially correlated with the cytolytic capacity of the sera. Therefore, naturally occurring IgM antibodies and/or generated IgM antibodies reactive with the HIV-1-infected cells in patients might have been responsible for long-term survival due to complement-mediated immune cytolysis which may, in conjunction with cytotoxic T lymphocytes, synergistically suppress the infected cells in vivo. Therefore, the transfusion of such IgM antibodies could be effective for the treatment of HIV-1-infected individuals.