Mapping the B cell superantigen binding site for HIV-1 gp120 on a VH3 Ig

• Published in: International immunology Vol. 12; no. 3; pp. 305 - 312
• Main Authors: Neshat, Mehran N., Goodglick, Lee, Lim, Kathleen, Braun, Jonathan
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.03.2000; Oxford Publishing Limited (England)
• Subjects: FR framework region; gp120; H hypervariable loop; HIV-1; Protein A; SPA Staphylococcus aureus Protein A; superantigen; TT tetanus toxoid; VH gene family
• ISSN: 0953-8178; 1460-2377
• 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 VH3 Ig gene family. The present study addresses the structural features of VH3 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 VH region was the major determinant of binding; diverse light chains were permissive for gp120 binding. A series of recombinant VH3–VH1 chimeric molecules was created to analyze the contribution of different subregions of VH3 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 VH, and including roles in gp120 contact and favorable conformation of the VH.