Identification of Conserved and Variant Epitopes of Human Immunodeficiency Virus Type 1 (HIV-1) gp120 by Human Monoclonal Antibodies Produced by EBV-Transformed Cell Lines

Using Epstein-Barr virus (EBV) transformation of B cells isolated from peripheral blood of two asymptomatic human immunodeficiency virus type 1-(HIV-1) infected subjects, we have produced four IgG₁ human monoclonal antibodies (HMAbs) that bind to HIV-1 gp120, as determined by Western blot analysis. Two of these HMAbs, designated N70-1.5e and N70-2.3a, react with epitopes of gp120 expressed by all strains tested thus far, and therefore, appear to identify conserved epitopes. The other two HMAbs, K24-3b and N70-1.9b, identify variant epitopes; K24-3b binds to an epitope which is absent from two strains but heterogeneously expressed in eight other strains; N70-1.9b binds to an epitope that is found in relatively few strains. We also describe a novel immunoassay in which viral glycoproteins, produced by HIV-1-infected cells grown in serum-free medium, are affinity immobilized in Concanavalin A-coated wells of enzyme-linked immunosorbent assay (ELISA) plates. This method greatly facilitates the preparation of solid-phase HIV envelope glycoproteins from multiple virus strains and screening immunoassays based on this method are highly sensitive and effective in detecting antibodies to gp120.