Hu Wei, He Meifang, Wang Xiaoning, Sun Qiang, Kuang Ming
Department of Oncology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, China.
Laboratory of General Surgery, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, China.
Vaccines (Basel). 2021 Sep 28;9(10):1093. doi: 10.3390/vaccines9101093.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has developed variants escaping neutralization antibody immunity established against the original virus. An understanding of broad-spectrum adaptive immunity, including CD8 T cell immunity to wide range of epitopes, could help translational efforts to improve coronavirus disease 2019 (COVID-19) prevention and therapy. However, there have been few direct studies in which such immunity exists in a population.
We selected SARS-CoV-2-conserved structural peptides that are not prone to mutation as antigens for broad-spectrum CD8 T cell immunity. Peripheral blood mononuclear cells (PBMCs) from unexposed healthy donors were stimulated with these peptides in vitro and CD8 T cell-specific response was monitored. The conserved peptide-specific CD8 T cells were sorted for T cell receptor (TCR) repertoire sequencing. The presence of specific complementary determining region 3 (CDR3) clones was analyzed in a healthy cohort.
For each structural protein, including S, E, M, N, the conserved peptides could potentially provide the largest number of major histocompatibility complex-I (MHC-I) epitopes in the Oriental and Caucasian populations. For conserved peptides from spike (S), envelope (E), membrane (M), nucleocapsid (N) proteins, we found that there were no cross-reactive memory T cells in the unexposed individuals. Instead, their T cells contain naïve TCR repertoire recognizing these conserved peptides. Using TCR sequencing and CDR3 clustering for the conserved peptides specific T cells, we found that the recovered patients had a higher proportion of TCR repertoire similar with that of specific CD8 T cells in unexposed individuals. Meanwhile, CDR3 clones of the above T cells were widely present in the healthy population.
This study provides evidence of broad-spectrum SARS-CoV-2 specific CD8 TCR repertoire in unexposed healthy population, which is implicated in the development and implementation of broad-spectrum vaccines against COVID-19.
严重急性呼吸综合征冠状病毒2（SARS-CoV-2）已产生变异株，可逃避针对原始病毒建立的中和抗体免疫。了解包括对广泛表位的CD8 T细胞免疫在内的广谱适应性免疫，有助于推动改善2019冠状病毒病（COVID-19）预防和治疗的转化研究。然而，关于人群中是否存在这种免疫的直接研究较少。
我们选择不易发生突变的SARS-CoV-2保守结构肽作为广谱CD8 T细胞免疫的抗原。用这些肽体外刺激未接触过病毒的健康供者的外周血单个核细胞（PBMC），并监测CD8 T细胞特异性反应。对保守肽特异性CD8 T细胞进行分选，用于T细胞受体（TCR）库测序。在一个健康队列中分析特异性互补决定区3（CDR3）克隆的存在情况。
对于每种结构蛋白，包括S、E、M、N，保守肽在东方人和高加索人群中可能提供最多数量的主要组织相容性复合体-I（MHC-I）表位。对于来自刺突（S）、包膜（E）、膜（M）、核衣壳（N）蛋白的保守肽，我们发现未接触过病毒的个体中不存在交叉反应性记忆T细胞。相反，他们的T细胞含有识别这些保守肽的幼稚TCR库。通过对保守肽特异性T细胞进行TCR测序和CDR3聚类，我们发现康复患者中与未接触过病毒个体的特异性CD8 T细胞具有相似TCR库的比例更高。同时，上述T细胞的CDR3克隆广泛存在于健康人群中。
本研究提供了未接触过病毒的健康人群中存在广谱SARS-CoV-2特异性CD8 TCR库的证据，这与开发和实施针对COVID-19的广谱疫苗有关。
