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MacLachlan BJ, Dolton G, Papakyriakou A, Greenshields-Watson A, Mason GH, Schauenburg A, Besneux M, Szomolay B, Elliott T, Sewell AK, Gallimore A, Rizkallah P, Cole DK, Godkin A. Human leukocyte antigen (HLA) class II peptide flanking residues tune the immunogenicity of a human tumor-derived epitope. J Biol Chem 2019; 294:20246-20258. [PMID: 31619516 PMCID: PMC6937582 DOI: 10.1074/jbc.ra119.009437] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Revised: 09/18/2019] [Indexed: 01/03/2023] Open
Abstract
CD4+ T-cells recognize peptide antigens, in the context of human leukocyte antigen (HLA) class II molecules (HLA-II), which through peptide-flanking residues (PFRs) can extend beyond the limits of the HLA binding. The role of the PFRs during antigen recognition is not fully understood; however, recent studies have indicated that these regions can influence T-cell receptor (TCR) affinity and pHLA-II stability. Here, using various biochemical approaches including peptide sensitivity ELISA and ELISpot assays, peptide-binding assays and HLA-II tetramer staining, we focused on CD4+ T-cell responses against a tumor antigen, 5T4 oncofetal trophoblast glycoprotein (5T4), which have been associated with improved control of colorectal cancer. Despite their weak TCR-binding affinity, we found that anti-5T4 CD4+ T-cells are polyfunctional and that their PFRs are essential for TCR recognition of the core bound nonamer. The high-resolution (1.95 Å) crystal structure of HLA-DR1 presenting the immunodominant 20-mer peptide 5T4111-130, combined with molecular dynamic simulations, revealed how PFRs explore the HLA-proximal space to contribute to antigen reactivity. These findings advance our understanding of what constitutes an HLA-II epitope and indicate that PFRs can tune weak affinity TCR-pHLA-II interactions.
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Affiliation(s)
- Bruce J MacLachlan
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Garry Dolton
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Athanasios Papakyriakou
- Institute of Biosciences and Applications, NCSR "Demokritos," Agia Paraskevi, 15341 Athens, Greece
| | - Alexander Greenshields-Watson
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Georgina H Mason
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Andrea Schauenburg
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Matthieu Besneux
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Barbara Szomolay
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Tim Elliott
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
- Centre for Cancer Immunology, University of Southampton, Faculty of Medicine, University Hospital, Southampton SO16 6YD, United Kingdom
| | - Andrew K Sewell
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Awen Gallimore
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Pierre Rizkallah
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - David K Cole
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Andrew Godkin
- Division of Infection and Immunity and Systems Immunity Research Institute, Cardiff University, Cardiff CF14 4XN, United Kingdom
- Department of Gastroenterology and Hepatology, University Hospital of Wales, CF14 4XN Cardiff, United Kingdom
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