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.

Altered peptide ligands: Prospects for immune intervention in autoimmune disease

“…Congruent with this prediction, Racioppi et al (1993) have reported the partial agonism of a Th1 clone specific for pigeon cytochrome c in the context of IE k when the native peptide was presented by a mutant IE molecule bearing only a single amino acid substitution. Similar findings have since been documented for the human class I molecule HLA-A0201: modification of the residue at position 97 caused the presentation of an otherwise agonistic peptide in a partially antagonistic manner (Maeurer et al, 1996).…”

Human Leukocyte Antigens A*3001 and A*3002 Show Distinct Peptide-Binding Patterns of the Mycobacterium tuberculosis Protein TB10.4: Consequences for Immune Recognition

“…Some TCRs may recognize their target peptides irrespective of the MHC presenting allele, as described for HLA-A3 and HLA-A11 (30). Not mutually exclusively, the different peptidebinding grooves of HLA-A*3002 and HLA-A*3001 might influence the conformation of the binding peptide, thereby altering the surface exposed to the TCR (32), which influences T-cell recognition. A different exposure of the peptide backbone to responder T cells may affect T-cell recognition and subsequent T-cell effector functions.…”

HLA-A29 and Birdshot Uveitis: Further Down the Rabbit Hole

“…In fact, 62-L 63-Q is detected in some other alleles such as HLA-A*43:01, HLA-A*11:11 , and HLA-A*68:130 [allele frequency of HLA-A*43:01 and HLA-A*11:11 in the European population >15,000 times less than HLA-A*29: 02 ( 54 ), and HLA-A*68:130 is not well documented ( 40 )]. However, these alleles differ from HLA-A29 alleles on various other key positions that influence peptide binding in the peptide-binding groove, including amino acid position 9 ( 55 ), 70, 76, 77, or positions 97 or 152, which influence the interaction with T cells ( 56 , 57 ). Notwithstanding these exceptional alleles, the amino acid motif 62-L 63-Q near exclusively accounts for HLA-A29 in the European population ( 54 ).…”