ENZYME-IMMUNOASSAY (ELISA) FOR THE EVALUATION OF ANTIBODIES DIRECTED TO THE CD4 RECEPTOR-BINDING SITE OF THE HIV GP120 MOLECULE

The interaction between the HIV envelope glycoprotein gp120 and the CD 4 molecule is probably the most important primary event determining HI V infection. Reactivity with the native viral envelope has been diffic ult to measure due to the lack of gp120 ligand purified directly from primary virus cultures. We have developed an ELISA, utilizing Galanthu s nivalis agglutinin (GNA) which selectively binds native HIV envelope gp120 in culture medium. The GNA-based ELISA eliminates the need for isotope-labelled reagents, live cells and recombinant non-natively gly cosylated envelope proteins and offers an easy way of using gp120 dire ctly from crude HIV culture medium. The reactivities of sera from seve ral categories of HIV infected individuals were assayed for inhibition of the HIV-1 gp120-CD4 binding. 19/32 (59.3%) sera from asymptomatic individuals and 7/10 (70%) sera from ARC/AIDS patients blocked the CD4 -gp120 binding. 20 serum samples from uninfected individuals showed a gp120-CD4 interaction blocking capacity of 0-15%. Two monoclonal antib odies, T4.2 directed to CD4 and 1171 directed to the CD4 binding site of gp120 were used as positive controls. Both Mabs inhibited CD4-gp120 binding by 66-90%.