Monoclonal anti-idiotypic antibody mimics the CD4 receptor and binds human immunodeficiency virus.

A monoclonal anti-idiotypic (anti-Id) antibody, HF1.7, was generated against anti-Leu-3a, a mouse monoclonal antibody (mAb) specific for the CD4 molecule on human helper/inducer T lymphocytes. The anti-Id nature of HF1.7 was demonstrated by the following properties. (i) It reacted in a solid-phase immunoassay with anti-Leu-3a and not with a panel of irrelevant mouse mAbs. (ii) It partially inhibited the binding of anti-Leu-3a to CD4+ T cells. (iii) It detected a common idiotype present on various anti-CD4 mAbs. Because the CD4 molecule represents the receptor site for human immunodeficiency virus (HIV), the etiologic viral agent of acquired immunodeficiency syndrome, we examined the ability of the anti-mAb HF1.7 to mimic CD4 and bind HIV. This anti-Id mAb reacted with HIV antigens in commercial HIV ELISAs and recognized HIV-infected human T cells but not uninfected cells when analyzed by flow cytofluorometry. Attesting further to the HIV specificity, the anti-Id mAb reacted with a recombinant gp160 peptide and a molecule of Mr 110,000-120,000 in immunoblot analysis of HIV-infected cell lysates. The anti-Id mAb also partially neutralized HIV infection of human T cells in vitro. These results strongly suggest that this anti-Id mAb mimics the CD4 antigenic determinants involved in binding to HIV.