Certain human Gp120-HIV antibodies react with anti-CD4 antibodies.

HIV+ human sera contain antibodies against most HIV proteins, including the envelope glycoprotein Gp120. Some of these antibodies may have an epitope that sterically resembles the CD4 region to which the Gp120 molecule binds. Amongst 58 HIV+ sera tested, we found three with the capacity to block the binding of anti-CD4 monoclonal antibodies to CD4+ cells. The serum with the highest blocking capacity was selected for further analysis. The inhibitor was shown to be an antibody that binds to the Gp120 molecule as well as to the anti-CD4 monoclonal T4.2. These CD4-mimicking antibodies were shown not to interfere with CD4-dependent reactions in vitro. Virus neutralizing experiments in vitro could not show any neutralizing effect with these antibodies alone. The HIV+ individual providing this antibody is still healthy, although HIV+ since 1983.