Characterization of T cell receptors reactive to HCRT_NH2, pHA_273-287, and NP_17-31 in control and narcolepsy patients

Narcolepsy type 1 (NT1), a disorder caused by hypocretin/orexin (HCRT) cell loss, is associated with human leukocyte antigen (HLA)-DQ0602 (98%) and T cell receptor (TCR) polymorphisms. Increased CD4⁺ T cell reactivity to HCRT, especially DQ0602-presented amidated C-terminal HCRT (HCRT_NH2), has been reported, and homology with pHA_273-287 flu antigens from pandemic 2009 H1N1, an established trigger of the disease, suggests molecular mimicry. In this work, we extended DQ0602 tetramer and dextramer data to 77 cases and 44 controls, replicating our prior finding and testing 709 TCRs in Jurkat 76 T cells for functional activation. We found that fewer TCRs isolated with HCRT_NH2 (∼11%) versus pHA_273-287 or NP_17-31 antigens (∼50%) were activated by their ligand. Single-cell characterization did not reveal phenotype differences in influenza versus HCRT_NH2-reactive T cells, and analysis of TCR CDR3αβ sequences showed TCR clustering by responses to antigens but no cross-peptide class reactivity. Our results do not support the existence of molecular mimicry between HCRT and pHA_273-287 or NP_17-31.