AEGiS-07IAC: Mouse monoclonal antibody (G3-4) defines a novel conformation-dependent epitope on gp120 important for neutralization of divergent HIV-1 isolates.

7th International AIDS Conference

Florence, Italy — June 16-21, 1991

Mouse monoclonal antibody (G3-4) defines a novel conformation-dependent epitope on gp120 important for neutralization of divergent HIV-1 isolates.

Int Conf AIDS 1991 Jun 16-21; 7:40 (abstract no. M.A.72)
Ho DD, Fund MS, Li XL, Sun C, Chang NT, Chang TW, Sun NC; The Aaron Diamond AIDS Research Center and New York University School of Medicine, New York, New York, USA

OBJECTIVE: To define domains in gp120 important for antibody neutralization of divergent HIV-1 isolates.

METHODS: G3-4 monoclonal antibody was generated by immunizing mice with purified gp120 of HIV-1 (IIIB), and it has been extensively characterized in radioimmunoprecipitation, neutralization, and gp120-CD4-binding inhibition assays, as well as epitope mapping studies.

RESULTS: G3-4 reacted with the gp120 of many (including IIIB and RF) but not all HIV-1 isolates. It also efficiently neutralized both IIIB and RF laboratory strains with 90% inhibitory doses (ID90) of 1.0 and 0.5 mug/ml, respectively. In addition, G3-4 neutralized 4 primary isolates with ID90 of approximately 0.5 to 6.0 mug/ml, while 5 other primary isolates were only partially neutralized by up to 20 mug/ml of antibody. In competition immunoassays, G3-4 and soluble CD4 were found to inhibit one another in binding to gp120. However, no competition was observed between G3-4 and mouse monoclonal antibodies directed to the V3 loop or the putative CD4-binding region of gp120. In particular, G3-4 did not compete with our human monoclonal antibody 15e (J Virol 1991;65:489), which identified the first conformational epitope on gp120 involved in group-specific neutralization of HIV-1 and in gp120-CD4 binding. Epitope mapping studies on G3-4 using synthetic or unglycosylated recombinant peptides were negative, suggesting that its epitope may be conformation-dependent. Indeed, this was confirmed by showing the loss of G3-4 serologic reactivity when gp120 was first denatured with dithiothreitol.

CONCLUSIONS: G3-4 has identified the second conformation-dependent epitope on gp120 important for the neutralization of divergent HIV-1 isolates. Experiments are now underway to examine the spatial relationship of the G3-4 epitope with the V3 loop and the CD4-binding region.

Keywords: AEGIS, HIV-1, Epitopes, Antigens, CD4, Antibodies, Monoclonal, Molecular Conformation, Protein Conformation, SK&F 106528, Human, Animal, Mice, ICA7
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