Mapping the B cell superantigen binding site for HIV-1 gp120 on a V(H)3 Ig

• Published in: International immunology Vol. 12; no. 3; pp. 305 - 312
• Main Authors: Neshat, M N, Goodglick, L, Lim, K, Braun, J
• Format: Journal Article
• Language: English
• Published: England 01.03.2000
• Subjects: AIDS/HIV; Amino Acid Sequence; Amino Acid Substitution; Animals; Antibodies, Monoclonal - chemistry; Antibodies, Monoclonal - genetics; Antibodies, Monoclonal - immunology; Antigen-Antibody Reactions; B-Lymphocytes - immunology; Binding Sites, Antibody - genetics; Binding Sites, Antibody - immunology; Genes, Immunoglobulin; HIV Antibodies - chemistry; HIV Antibodies - genetics; HIV Antibodies - immunology; HIV Envelope Protein gp120 - immunology; HIV-1 - immunology; Immunoglobulin Fab Fragments - chemistry; Immunoglobulin Fab Fragments - genetics; Immunoglobulin Fab Fragments - immunology; Immunoglobulin Heavy Chains - chemistry; Immunoglobulin Heavy Chains - genetics; Immunoglobulin Heavy Chains - immunology; Immunoglobulin Variable Region - chemistry; Immunoglobulin Variable Region - genetics; Immunoglobulin Variable Region - immunology; Mice; Molecular Sequence Data; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - immunology; Sequence Alignment; Sequence Homology, Amino Acid; Superantigens - immunology
• ISSN: 0953-8178
• DOI: 10.1093/intimm/12.3.305

The emerging class of B cell superantigens includes HIV-1 gp120, which binds to many members of the V(H)3 Ig gene family. The present study addresses the structural features of V(H)3 antibodies conferring gp120 binding activity using a panel of recombinant full-length and Fab Ig proteins. Binding activity was fully conferred by the Fab portion of the Ig molecule. The V(H) region was the major determinant of binding; diverse light chains were permissive for gp120 binding. A series of recombinant V(H)3-V(H)1 chimeric molecules was created to analyze the contribution of different subregions of V(H)3 to gp120 binding. Hypervariable loop 1 (H1) substitution alone caused a 10-fold reduction in binding activity. The framework subregions (FR1, FR2 and FR3) and H2 also influenced binding, since substitutions of various combinations of these subregions conferred 10- to 100-fold binding reductions. We conclude that gp120 binding occurs through a non-conventional interaction involving multiple discontinuously arrayed residues spanning the V(H), and including roles in gp120 contact and favorable conformation of the V(H).