There is substantial evidence supporting the CD4 molecule as the principal cellular receptor for the human immunodeficiency virus type 1 (HIV-1). A number oftruncated recombinant soluble CD4 (sCD4) molecules have been produced and shown to easily neutralize infection of laboratory strains of HIlV-1 in vitro, and clinical trials using these sCD4 preparations have begun in patients with AIDS.

To define the domains in the envelope glycoprotein important for antibody neutralization of the human immunodeficiency virus type 1 (HIV-1), monoclonal antibodies (mAbs) were generated by immunizing mice with purified glycoprotein gpl20 of the MB isolate. One mAb, G3-4, reacted with the gpl20 of homologous ('fB) and heterologous (RF) isolates. In addition, mAb G3-4 efficiently neutralized both

A human monoclonal antibody designated 15e is reactive with the envelope glycoprotein (gpl20) of multiple isolates of human immunodeficiency virus type 1 (HIV-1). Antibody 15e also neutralizes HIV-1 with broad specificity and blocks gpl20 binding to CD4. Characterization of the 15e epitope shows that it is conformation dependent and is distinct from previously recognized functional domains of gpl20, suggesting that this epitope represents a novel site important for HIV-1 neutralization and CD4 binding. These findings have implications for the development of a vaccine for AIDS.