title: Amino acid substitutions at position 97 in HLA-A2 segregate cytolysis from cytokine release in MART-1/Melan-A peptide AAGIGILTV-specific cytotoxic T lymphocytes.
abstract: CD8+ T lymphocytes recognize antigenic peptides presented by major histocompatibility complex (MHC) class I molecules. Individual peptide termini appear to be fixed at the C- and N-terminal ends. In contrast, central peptide side chains residues may point in different directions and exhibit limited flexibility, dependent on the MHC class I structural variation. For instance, position 97 in HLA-A201 has been shown to shift individual peptide species into different coordinations, one oriented towards the peptide N terminus, or more towards the C-terminal end. The conformational shape of such non-anchor peptide residues may affect the affinity of MHC/peptide/TCR interaction, resulting in quantitative, or qualitative different T cell effector functions. To characterize the impact of different amino acid residues occupying position 97 in HLA-A2 on peptide binding and presentation to CTL, we generated a panel of mutated HLA-A2 molecules containing either M, K, T, V, G, Q, W, P or H at position 97. The HLA-A0201 presented melanoma-associated MART-1/Melan-A derived peptide AAGIGILTV was employed to assess the impact of such position-97 mutations on HLA-A2 in peptide binding measured in an HLA-A2 reconstitution assay and presentation to AAGIGILTV-specific polyclonal or clonal T lymphocytes as measured by cytotoxicity, or interferon (IFN)-gamma and granulocyte/ macrophage colony-stimulating factor (GM-CSF) secretion. The high-affinity AAGIGILTV peptide bound to all position-97 mutants, albeit with differential efficiencies, and elicited specific release of IFN-gamma and GM-CSF by CTL. CTL responses were triggered only by the HLA-A2 wild type, by HLA-A2-H97 (histidine position 97 mutant), and HLA-A2-W97. The HLA-A2-M97 presenting molecule elicited enhanced cytokine release and CTL effector functions by polyclonal and by clonal effector T cells. These results indicate that MHC class I-bound peptides can trigger specific cytokine release by effector T cells independently of their ability to induce cytolysis. We conclude that relatively minor changes in the MHC class I peptide binding groove, including substitutions at position 97, can affect recognition by antigen-specific T cells. Mutant MHC class I molecules, such as those described here, may act as partial peptide antagonists and could be useful for inducing T lymphocytes with qualitatively different effector functions.
authors.affiliation: Department of Medical Microbiology, University of Mainz, Germany. maeurer@omalley.zdv.uni-mainz.de
authors.forename: M J
authors.initials: MJ
authors.lastname: Maeurer
authors.forename: H W
authors.initials: HW
authors.lastname: Chan
authors.forename: J
authors.initials: J
authors.lastname: Karbach
authors.forename: R D
authors.initials: RD
authors.lastname: Salter
authors.forename: A
authors.initials: A
authors.lastname: Knuth
authors.forename: M T
authors.initials: MT
authors.lastname: Lotze
authors.forename: W J
authors.initials: WJ
authors.lastname: Storkus
mesh_terms: D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis* / Q000187:drug effects*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects* / Q000276:immunology*; D015789:HLA-A2 Antigen / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology*; D006801:Humans; D058965:MART-1 Antigen; D008545:Melanoma; D009363:Neoplasm Proteins / Q000276:immunology*; D011485:Protein Binding / Q000187:drug effects / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D016207:Cytokines; D015789:HLA-A2 Antigen; D058965:MART-1 Antigen; C548667:MLANA protein, human; D009363:Neoplasm Proteins