Research ArticleT CELLS

Empty peptide-receptive MHC class I molecules for efficient detection of antigen-specific T cells

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Science Immunology  19 Jul 2019:
Vol. 4, Issue 37, eaau9039
DOI: 10.1126/sciimmunol.aau9039

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Empty MHC reagents improve T cell detection

Recombinant MHC molecules displaying single peptides in their peptide-binding cleft are valuable reagents for identifying T cells that bind specific peptide-MHC complexes. Two studies in this week’s issue show that disulfide-stabilized (DS) class I MHC molecules offer a more efficient path to preparing large libraries of MHC-peptide reagents. Saini et al. developed DS versions of three class I MHC molecules and used a library of DS-HLA-A2-peptide multimers to rapidly screen T cells infiltrating human melanoma tumors for neoantigen reactivity. Moritz et al. prepared libraries of DS-HLA-A2-peptide complexes to screen an affinity-matured TCR for cross-reactivity with self–peptide-MHC complexes. Empty class I MHC molecules that are stable and easily loaded with peptide will facilitate the wider use of MHC-peptide reagents for T cell detection. See related Research Article by Moritz et al. in this issue.

Abstract

The peptide-dependent stability of MHC class I molecules poses a substantial challenge for their use in peptide-MHC multimer–based approaches to comprehensively analyze T cell immunity. To overcome this challenge, we demonstrate the use of functionally empty MHC class I molecules stabilized by a disulfide bond to link the α1 and α2 helices close to the F pocket. Peptide-loaded disulfide-stabilized HLA-A*02:01 shows complete structural overlap with wild-type HLA-A*02:01. Peptide-MHC multimers prepared using disulfide-stabilized HLA-A*02:01, HLA-A*24:02, and H-2Kb can be used to identify antigen-specific T cells, and they provide a better staining index for antigen-specific T cell detection compared with multimers prepared with wild-type MHC class I molecules. Disulfide-stabilized MHC class I molecules can be loaded with peptide in the multimerized form without affecting their capacity to stain T cells. We demonstrate the value of empty-loadable tetramers that are converted to antigen-specific tetramers by a single-step peptide addition through their use to identify T cells specific for mutation-derived neoantigens and other cancer-associated antigens in human melanoma.

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