Position-5–driven reorientation of an immunodominant HLA-A*24:02 SARS-CoV-2 epitope drives universal T cell escape

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Abstract

Cytotoxic T lymphocytes form a critical component of SARS-CoV-2 immunity by recognizing viral peptides bound to HLA class I molecules. Here, we identified the spike-derived peptide NYNYLYRLF448-456 (NF9) as the immunodominant HLA-A*24:02–restricted epitope in both convalescent and vaccinated donors. Across cohorts, A24/NF9-specific responses were dominated by public TCR motifs featuring TRAV12-1 paired with TRBJ2-7 and a conserved CDR3β sequence (CASSXXXGYEQYF). Using a panel of 13 TCRs, we mapped recognition of single amino acid substitutions within NF9 and identified residue 5 (L452) as the principal determinant of escape. The L452R substitution, characteristic of the Delta variant, abolished recognition across all tested TCRs despite preserved HLA binding. Crystallography of a representative public TCR (P1-15) revealed that mutation at position-5 reoriented the peptide within HLA-A*24:02, flipping the adjacent Y453 side chain into the peptide-binding groove and eliminating the dominant TCR contact. This position-5–driven conformational switch provided a structural mechanism for universal loss of NF9 recognition by HLA-A*24:02–restricted T cells. Consistent with this, Delta-infected convalescents failed to mount de novo NF9-5R–specific responses while retaining responses to the conserved A24/QI9 spike epitope. Together, these findings defined the basis of A24/NF9 recognition and showed how 1 mutation remodeled peptide presentation to abrogate TCR responses.

Authors

Takeshi Nakama, Aaron Wall, Garry Dolton, Li Rong Tan, Hannah Thomas, Hiroshi Hamana, Yoshiki Aritsu, Toong Seng Tan, Mako Toyoda, Yoshihiko Goto, Huanyu Li, Mizuki Kitamatsu, Keiko Udaka, Yusuke Miyashita, Hiroyuki Oshiumi, Kimitoshi Nakamura, Yoji Nagasaki, Rumi Minami, Hirotomo Nakata, Pierre J. Rizkallah, Hiroyuki Kishi, Takamasa Ueno, Andrew K. Sewell, Chihiro Motozono