Identification of a novel myosin antigen activating CD8+ T cells in C57BL/6 mice

Heart-specific T cells play important roles in myocardial diseases, including myocarditis, myocardial infarction, and heart failure. However, only few cardiac antigens and their respective specific T cell receptors (TCRs) have been validated so far. Therefore, we sought to identify new cardiac T cell epitopes in C57BL/6 mice and to characterize the specific TCRs. Antigen mapping of myosin heavy chain alpha (MYHCA) led to the identification of a 9-mer epitope (MYHCA724-732) recognized by CD8+ T cells. Single-cell TCR sequencing (scTCR-seq) analysis of MYHCA-stimulated CD8+ T cells enabled the identification of distinct TCRs enriched on specific T cells. Selected TCRs inferred from scTCR-seq data were then expressed on reporter cell lines and functionally validated. Our study expands the toolkit required to study heart-directed immune responses by revealing a new cardiac antigen and specific TCRs. These tools will enable in vivo characterization of myosin-specific CD8+ T cells in murine models of myocardial diseases.