Center of Excellence for Inflammation, Infectious Disease and Immunity, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee 37614, United States; Division of Infectious Diseases, Department of Internal Medicine, Quillen College of Medicine, ETSU, Johnson City, Tennessee 37614, United States.
Center of Excellence for Inflammation, Infectious Disease and Immunity, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee 37614, United States.
Virus Res. 2021 Oct 15;304:198508. doi: 10.1016/j.virusres.2021.198508. Epub 2021 Jul 27.
The COVID-19 pandemic caused by SARS-CoV-2 infection poses a serious threat to public health. An explicit investigation of COVID-19 immune responses, particularly the host immunity in recovered subjects, will lay a foundation for the rational design of therapeutics and/or vaccines against future coronaviral outbreaks. Here, we examined virus-specific T cell responses and identified T cell epitopes using peptides spanning SARS-CoV-2 structural proteins. These peptides were used to stimulate peripheral blood mononuclear cells (PBMCs) derived from COVID-19-recovered subjects, followed by an analysis of IFN-γ-secreting T cells by enzyme-linked immunosorbent spot (ELISpot). We also evaluated virus-specific CD4 or CD8 T cell activation by flow cytometry assay. By screening 52 matrix pools (comprised of 315 peptides) of the spike (S) glycoprotein and 21 matrix pools (comprised of 102 peptides) spanning the nucleocapsid (N) protein, we identified 28 peptides from S protein and 5 peptides from N protein as immunodominant epitopes. The immunogenicity of these epitopes was confirmed by a second ELISpot using single peptide stimulation in memory T cells, and they were mapped by HLA restrictions. Notably, SARS-CoV-2 specific T cell responses positively correlated with B cell IgG and neutralizing antibody responses to the receptor-binding domain (RBD) of the S protein. Our results demonstrate that defined levels of SARS-CoV-2 specific T cell responses are generated in some, but not all, COVID-19-recovered subjects, fostering hope for the protection of a proportion of COVID-19-exposed individuals against reinfection. These results also suggest that these virus-specific T cell responses may induce protective immunity in unexposed individuals upon vaccination, using vaccines generated based on the immune epitopes identified in this study. However, SARS-CoV-2 S and N peptides are not potently immunogenic, and none of the single peptides could universally induce robust T cell responses, suggesting the necessity of using a multi-epitope strategy for COVID-19 vaccine design.
由严重急性呼吸系统综合征冠状病毒 2（SARS-CoV-2）感染引起的 COVID-19 大流行对公共卫生构成了严重威胁。明确 COVID-19 免疫反应，特别是对已康复者的宿主免疫反应的调查，将为合理设计针对未来冠状病毒爆发的疗法和/或疫苗奠定基础。在这里，我们使用跨越 SARS-CoV-2 结构蛋白的肽段来检测病毒特异性 T 细胞反应并鉴定 T 细胞表位。这些肽段用于刺激来自 COVID-19 康复患者的外周血单核细胞（PBMC），然后通过酶联免疫斑点（ELISpot）分析 IFN-γ分泌的 T 细胞。我们还通过流式细胞术测定评估了病毒特异性 CD4 或 CD8 T 细胞的激活。通过筛选 52 个基质池（由 315 个肽段组成）的刺突（S）糖蛋白和 21 个基质池（由 102 个肽段组成）跨越核衣壳（N）蛋白，我们鉴定了 28 个 S 蛋白肽段和 5 个 N 蛋白肽段作为免疫优势表位。通过使用单个肽段刺激记忆 T 细胞的第二次 ELISpot 验证了这些表位的免疫原性，并通过 HLA 限制进行了映射。值得注意的是，SARS-CoV-2 特异性 T 细胞反应与 B 细胞 IgG 和针对 S 蛋白受体结合结构域（RBD）的中和抗体反应呈正相关。我们的研究结果表明，在一些但不是所有 COVID-19 康复患者中产生了明确水平的 SARS-CoV-2 特异性 T 细胞反应，为一部分 COVID-19 暴露个体免受再感染提供了保护的希望。这些结果还表明，在未暴露个体中，使用基于本研究中鉴定的免疫表位生成的疫苗，这些病毒特异性 T 细胞反应可能会诱导保护性免疫。然而，SARS-CoV-2 S 和 N 肽段的免疫原性不强，并且没有一个单独的肽段能够普遍诱导强烈的 T 细胞反应，这表明需要使用多表位策略来设计 COVID-19 疫苗。
