Human leukocyte antigen (HLA) class II peptide flanking residues tune the immunogenicity of a human tumor-derived epitope

Bruce J. MacLachlan, Garry Dolton, Athanasios Papakyriakou, Alexander Greenshields-Watson, Georgina H. Mason, Andrea Schauenburg, Matthieu Besneux, Barbara Szomolay, Tim Elliott, Andrew K. Sewell, Awen Gallimore, Pierre Rizkallah, David K. Cole, Andrew Godkin

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3 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)20246-20258
Number of pages13
JournalJournal of Biological Chemistry
Issue number52
Publication statusPublished - 27 Dec 2019

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