Human Anti-V3 HIV-1 Monoclonal Antibodies Encoded by the VH5-51/VL Lambda Genes Define a Conserved Antigenic Structure

Abstract

Preferential usage of immunoglobulin (Ig) genes that encode antibodies (Abs) against various pathogens is rarely observed and the nature of their dominance is unclear in the context of stochastic recombination of Ig genes. The hypothesis that restricted usage of Ig genes predetermines the antibody specificity was tested in this study of 18 human anti-V3 monoclonal Abs (mAbs) generated from unrelated individuals infected with various subtypes of HIV-1, all of which preferentially used pairing of the VH5-51 and VL lambda genes. Crystallographic analysis of five VH5-51/VL lambda-encoded Fabs complexed with various V3 peptides revealed a common three dimensional (3D) shape of the antigen-binding sites primarily determined by the four complementarity determining regions (CDR) for the heavy (H) and light (L) chains: specifically, the H1, H2, L1 and L2 domains. The CDR H3 domain did not contribute to the shape of the binding pocket, as it had different lengths, sequences and conformations for each mAb. The same shape of the binding site was further confirmed by the identical backbone conformation exhibited by V3 peptides in complex with Fabs which fully adapted to the binding pocket and the same key contact residues, mainly germline-encoded in the heavy and light chains of five Fabs. Finally, the VH5-51 anti-V3 mAbs recognized an epitope with an identical 3D structure which is mimicked by a single mimotope recognized by the majority of VH5-51-derived mAbs but not by other V3 mAbs. These data suggest that the identification of preferentially used Ig genes by neutralizing mAbs may define conserved epitopes in the diverse virus envelopes. This will be useful information for designing vaccine immunogen inducing cross-neutralizing Abs.

Cross-Neutralization Activity of Single-Chain Variable Fragment (scFv) Derived from Anti-V3 Monoclonal Antibodies Mediated by Post-Attachment Binding

“…The genes involved to the 2 MAb clones 0.5g and 5G2 are the same (the VH3-30 gene for VH and the VK2-28 gene for VL), although the lineages of the 2 clones differ. In contrast, the MAb 16G6 uses the VH5-51 gene and the llight chain, which were previously reported as the preferential genes used by anti-V3 antibodies with crosssubtype reactivity (38). The 16G6 MAb reacted not only with HIV-1 harboring the V3-tip sequence 315R, but also with HIV-1 harboring the V3-tip sequence 315Q, which is indicative of a non-subtype virus (11).…”

Rabbit Anti-HIV-1 Monoclonal Antibodies Raised by Immunization Can Mimic the Antigen-Binding Modes of Antibodies Derived from HIV-1-Infected Humans

“…Several recently described highly potent human MAbs, including PGT128, are also against the C-terminal region of V3, as well as its associ-ated glycans (26). Many of the anti-V3 MAbs are characterized by structural methods, including protein crystallography and the nuclear magnetic resonance (NMR) method (19,(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). These structural studies of MAbs against the V3 crown showed that they have, in general, two antigen-binding modes.…”

Functional and Structural Characterization of Human V3-Specific Monoclonal Antibody 2424 with Neutralizing Activity against HIV-1 JRFL

“…Together with the current 2424-V3 structure, many crystal structures of human V3 MAbs in complex with their cognate V3 epitopes have been resolved (35,(68)(69)(70) Abs can be generated in these individuals by vaccination. 2424-like Abs were not the dominant response elicited in mice upon immunization with gp120 JRFL alone or in complex with MAb, as indicated by the inability of serum Ab pools from the immunized animals to neutralize 2424-sensitive viruses such as JRFL or REJO (27), although the composition of dominant and nondominant Ab responses were not yet delineated and the gp120/MAb complex vaccines tested were not selected and optimized for presenting the 2424 epitope.…”