Despite the growing knowledge of T cell responses in COVID-19 patients, there is a lack of detailed characterizations for T cell-antigen interactions and T cell functions. Here, with a predicted peptide library from SARS-CoV-2 S and N proteins, we found that specific CD8⁺ T cell responses were identified in over 75% of COVID-19 convalescent patients (15/20) and an epitope from the N protein, N^361-369 (KTFPPTEPK), was the most dominant epitope from our selected peptide library. Importantly, we discovered 2 N^361-369-specific T cell receptors (TCRs) with high functional avidity that were independent of the CD8 co-receptor. These TCRs exhibited complementary cross-reactivity to several presently reported N^361-369 mutant variants, as to the wild-type epitope. Further, the natural functions of these TCRs in the cytotoxic immunity against SARS-CoV-2 were determined with dendritic cells (DCs) and the lung organoid model. We found that the N^361-369 epitope could be normally processed and endogenously presented by these different types of antigen presenting cells, to elicit successful activation and effective cytotoxicity of CD8⁺ T cells ex vivo. Our study evidenced potential mechanisms of cellular immunity to SARS-CoV-2, and illuminated potential ways of viral clearance in COVID-19 patients. These results indicate that utilizing CD8-independent TCRs against SARS-CoV-2-associated antigens may provide functional superiority that is beneficial for the adoptive cell immunotherapies based on natural or genetically engineered T cells. Additionally, this information is highly relevant for the development of the next-generation vaccines with protections against continuously emerged SARS-CoV-2 mutant strains.

尽管对 COVID-19 患者 T 细胞反应的了解越来越多，但仍缺乏对 T 细胞-抗原相互作用和 T 细胞功能的详细表征。在这里，与来自SARS-CoV的-2 S和N蛋白的预测的肽文库，我们发现，特异性的CD8 ⁺ T细胞应答在COVID-19恢复期患者（15/20）的75％以上被确定，并从N的表位蛋白质 N ^361-369 (KTFPPTEPK) 是我们选择的肽库中最主要的表位。重要的是，我们发现了 2 N ^361-369特异性 T 细胞受体 (TCR)，它们具有独立于 CD8 共受体的高功能亲和力。这些 TCR 与目前报道的几个 N ^361-369表现出互补的交叉反应性突变变体，对于野生型表位。此外，这些 TCR 在针对 SARS-CoV-2 的细胞毒性免疫中的自然功能是用树突细胞 (DC) 和肺类器官模型确定的。我们发现 N ^361-369表位可以被这些不同类型的抗原呈递细胞正常加工和内源性呈递，从而在体外引发 CD8 ⁺ T 细胞的成功激活和有效细胞毒性. 我们的研究证明了细胞对 SARS-CoV-2 免疫的潜在机制，并阐明了 COVID-19 患者病毒清除的潜在途径。这些结果表明，利用 CD8 非依赖性 TCR 对抗 SARS-CoV-2 相关抗原可能会提供功能优势，这有利于基于天然或基因工程 T 细胞的过继细胞免疫疗法。此外，该信息与下一代疫苗的开发高度相关，这些疫苗可针对不断出现的 SARS-CoV-2 突变株提供保护。