VH-related idiotopes detected by site-directed mutagenesis. A study induced by the failure to find CD4 anti-idiotypic antibodies mimicking the cellular receptor of HIV.
The function of the CD4 cell surface protein as coreceptor on T helper lymphocytes and as receptor for HIV makes this glycoprotein a prime target for an immune intervention with mAb. A detailed understanding of the structural determinants on the therapeutic CD4 mAb that are involved in Ag binding or are recognized by anti-idiotypic mAb (anti-Id) may be important for designing antibodies with optimal therapeutic efficacy. Seven anti-Id raised against the CD4 mAb M-T310 were selected from a large panel with the intention to obtain CD4 mimicking structures with specificity for HIV gp120. The selected anti-Id did not react with other CD4-specific mAb cross-blocking M-T310. Among these, mAb M-T404, although having the same L chain as M-T310 and a VH region sequence differing only at 14 amino acid positions, was not recognized by the anti-Id. M-T310 H chain complexed with the J558L L chain reacted with all anti-Id, thus demonstrating that the recognized idiotopes are located within the VH region. To identify the idiotopes of M-T310 seen by the anti-Id, variants of M-T404 containing one or more of the M-T310-derived substitutions were generated by oligonucleotide-directed mutagenesis. The reactivity pattern of the mutant proteins with the anti-Id demonstrated that the idiotopes reside within the complementarity determining region (CDR) 2 and CDR3 loops of the VH region. A major idiotope was defined by a single amino acid in CDR2 that was recognized by three anti-Id, whereas the four other anti-Id reacted with determinants of CDR3. Although the performed amino acid substitutions did influence the Id recognition, Ag binding was not significantly affected, suggesting that none of the anti-Id can be considered as a mimicry of the CD4 Ag.
Weissenhorn
W
W
Institute for Immunology, University of Munich, FRG.
Chen
Y H
YH
Riethmüller
G
G
Rieber
E P
EP
Weiss
E H
EH
D000595:Amino Acid Sequence; D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D001483:Base Sequence; D015704:CD4 Antigens / Q000276:immunology*; D005434:Flow Cytometry; D006801:Humans; D007130:Immunoglobulin Idiotypes; D007135:Immunoglobulin Variable Region / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011991:Receptors, Virus / Q000276:immunology*; D013329:Structure-Activity Relationship
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D007130:Immunoglobulin Idiotypes; D007135:Immunoglobulin Variable Region; D009838:Oligodeoxyribonucleotides; D011991:Receptors, Virus