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.
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.
Denkberg
Galit
G
Faculty of Biology, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
Klechevsky
Eynav
E
Reiter
Yoram
Y
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
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