Abstract: Methods and compositions are provided for the use of an envelope polypeptide or a functional variant thereof from a lentivirus that is not HIV-1 as a molecular scaffold for HIV-1 epitopes. The HIV-1 epitopes can be recognized by HIV-1 binding antibodies, HIV-1 neutralizing antibodies and/or CD4-induced antibodies. Thus, methods are provided for detecting HIV-1 binding antibodies in a subject infected with HTV-1. Further provided are methods to determine an epitope for an HIV-1 binding antibody; methods to assay for an HIV-1 binding antibody; methods to identify a soluble CD4 mimic; methods to neutralize an non-HIV-1 virus; diagnostic assays to monitor HIV disease in a subject or to monitor the subject's response to immunization by a HIV vaccine; and methods to alter the neutralization potential of an HIV-1 derived CD4-induced antibody. Chimeric polypeptides, chimeric polynucleotides, kits, cells and viruses are also provided.