title: Modification of a tumor-derived peptide at an HLA-A2 anchor residue can alter the conformation of the MHC-peptide complex: probing with TCR-like recombinant antibodies.
abstract: A common assumption about peptide binding to the class I MHC complex is that each residue in the peptide binds independently. Based on this assumption, modifications in class I MHC anchor positions were used to improve the binding properties of low-affinity peptides (termed altered peptide ligands), especially in the case when tumor-associated peptides are used for immunotherapy. Using a new molecular tool in the form of recombinant Abs endowed with Ag-specific MHC-restricted specificity of T cells, we show that changes in the identity of anchor residues may have significant effects, such as altering the conformation of the peptide-MHC complex, and as a consequence, may affect the TCR-contacting residues. We herein demonstrate that the binding of TCR-like recombinant Abs, specific for the melanoma differentiation Ag gp100 T cell epitope G9-209, is entirely dependent on the identity of a single peptide anchor residue at position 2. An example is shown in which TCR-like Abs can recognize the specific complex only when a modified peptide, G9-209-2 M, with improved affinity to HLA-A2 was used, but not with the unmodified natural peptide. Importantly, these results demonstrate, using a novel molecular tool, that modifications at anchor residues can dramatically influence the conformation of the MHC peptide groove and thus may have a profound effect on TCR interactions. Moreover, these results may have important implications in designing modifications in peptides for cancer immunotherapy, because most such peptides studied are of low affinity.
authors.affiliation: Faculty of Biology, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
authors.forename: Galit
authors.initials: G
authors.lastname: Denkberg
authors.forename: Eynav
authors.initials: E
authors.lastname: Klechevsky
authors.forename: Yoram
authors.initials: Y
authors.lastname: Reiter
mesh_terms: D019943:Amino Acid Substitution; D001666:Binding Sites, Antibody; D002461:Cell Line, Transformed; D018984:Epitopes, T-Lymphocyte / Q000276:immunology / Q000378:metabolism; D015789:HLA-A2 Antigen / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000302:isolation & purification / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000276:immunology; D009363:Neoplasm Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D009842:Oligopeptides / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D019151:Peptide Library; D011487:Protein Conformation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D013329:Structure-Activity Relationship; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism; D014407:Tumor Cells, Cultured; D058951:gp100 Melanoma Antigen
chemical_list: D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D007140:Immunoglobulin Fab Fragments; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D009842:Oligopeptides; C548637:PMEL protein, human; D019151:Peptide Library; D011948:Receptors, Antigen, T-Cell; D011994:Recombinant Proteins; D058951:gp100 Melanoma Antigen