Cross-Neutralizing Antibodies Against HIV-1 (HTLV-IIIB and HTLV-IIIRF) and HIV-2 (SBL-6669 and a New Isolate SBL-K135)

Abstract
A total of 57 HIV-1 antibody-positive sera and 43 HIV-2 antibody-positive sera were all tested for neutralizing capacity against two HIV-1 isolates (HTLV-IIIB and HTLV-IIIRF) and two HIV-2 isolates (SBL-6669 and SBL-K135). SBL-K135 is a new HIV-2 isolate obtained from a patient with clinical AIDS from Guinea-Bissau. Among the HIV-1-positive sera, 84% neutralized any of the HIV-1 isolates, 67% neutralized both HIV-1 isolates, and 35% neutralized any of the HIV-2 isolates. Among the HIV-2-positive sera, 91% neutralized any of the HIV-2 isolates, 67% neutralized both HIV-2 isolates, and 37% neutralized any of the HIV-1 isolates. Thus, neutralizing antibodies in HIV-1- and HIV-2-positive sera can be cross-reacting, type-specific, or strain-specific. The cross-neutralizing titers were lower than the neutralizing titers against the type-specific viral isolates. The presence of cross-neutralizing antibodies was related to the presence of neutralizing antibodies against both type-specific isolates.