ABSTRACT
INTRODUCTION: Similar to antibody detection, severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2)-specific T-cell response evaluation is also pivotal among the coronavirus disease 2019 (COVID-19) convalescents and the vaccinated populations. Nucleocapsid (N) protein is one of the main structural proteins of SARS-CoV-2 and can trigger T-cell responses in humans. METHODS: An overlapping peptide pool covering the full length of the N protein was designed, peptides with positive T-cell activating potency in COVID-19 convalescents were screened, and CD8+ T cell epitopes were further identified. The epitope was used to detect the SARS-CoV-2-specific CD8+ T cell responses in COVID-19 convalescents based in intracellular cytokine staining and tetramer staining in flow cytometry. RESULTS: A human leukocyte antigen A (HLA-A)*1101-restricted CD8+ T cell epitope, which could stimulate the production of IFN-γ via peripheral blood mononuclear cells (PBMCs) of the convalescents was defined, and the tetramer generated with this epitope could detect SARS-CoV-2-specific T cells in the PBMCs of the convalescents. The structural investigation eliminated that the epitope was a typical HLA-A*1101-restricted T-cell epitope which was conserved among all the sarbecoviruses. DISCUSSION: The newly identified SARS-CoV-2-derived T-cell epitope was helpful to detect the cellular immunity against different sarbecoviruses including SARS-CoV and SARS-CoV-2. This study provided an evaluation method and also a peptide candidate for the research and development of T-cell based vaccine for the virus.