Department of Virology, Institute of Experimental Medicine, 197376 Saint Petersburg, Russia.
Viruses. 2021 Jul 29;13(8):1490. doi: 10.3390/v13081490.
New coronavirus SARS-CoV-2, a causative agent of the COVID-19 pandemic, has been circulating among humans since November 2019. Multiple studies have assessed the qualitative and quantitative characteristics of virus-specific immunity in COVID-19 convalescents, however, some aspects of the development of memory T-cell responses after natural SARS-CoV-2 infection remain uncovered.
In most of published studies T-cell immunity to the new coronavirus is assessed using peptides corresponding to SARS-CoV-1 or SARS-CoV-2 T-cell epitopes, or with peptide pools covering various parts of the viral proteins. Here, we determined the level of CD4 and CD8 memory T-cell responses in COVID-19 convalescents by stimulating PBMCs collected 1 to 6 months after recovery with sucrose gradient-purified live SARS-CoV-2. IFNγ production by the central and effector memory helper and cytotoxic T cells was assessed by intracellular cytokine staining assay and flow cytometry.
Stimulation of PBMCs with live SARS-CoV-2 revealed IFNγ-producing T-helper effector memory cells with CD4CD45RACCR7 phenotype, which persisted in circulation for up to 6 month after COVID-19. In contrast, SARS-CoV-2-specific IFNγ-secreting cytotoxic effector memory T cells were found at significant levels only shortly after the disease, but rapidly decreased over time.
The stimulation of immune cells with live SARS-CoV-2 revealed a rapid decline in the pool of effector memory CD8, but not CD4, T cells after recovery from COVID-19. These data provide additional information on the development and persistence of cellular immune responses after natural infection, and can inform further development of T cell-based SARS-CoV-2 vaccines.
新型冠状病毒 SARS-CoV-2 是 COVID-19 大流行的病原体，自 2019 年 11 月以来一直在人群中传播。多项研究评估了 COVID-19 恢复期患者病毒特异性免疫的定性和定量特征，然而，自然感染 SARS-CoV-2 后记忆 T 细胞反应的发展仍有一些方面尚未被揭示。
在已发表的大多数研究中，使用对应于 SARS-CoV-1 或 SARS-CoV-2 T 细胞表位的肽或覆盖病毒蛋白各个部分的肽库来评估对新型冠状病毒的 T 细胞免疫。在这里，我们通过用蔗糖梯度纯化的活 SARS-CoV-2 刺激恢复期后 1 至 6 个月采集的 PBMC，来确定 COVID-19 恢复期患者的 CD4 和 CD8 记忆 T 细胞反应水平。通过细胞内细胞因子染色和流式细胞术评估中央和效应记忆辅助和细胞毒性 T 细胞中 IFNγ 的产生。
用活 SARS-CoV-2 刺激 PBMC 揭示了具有 CD4CD45RACCR7 表型的 IFNγ 产生 T 辅助效应记忆细胞，这些细胞在 COVID-19 后可在循环中持续存在长达 6 个月。相比之下，SARS-CoV-2 特异性 IFNγ 分泌细胞毒性效应记忆 T 细胞仅在疾病后不久就以显著水平存在，但随着时间的推移迅速减少。
用活 SARS-CoV-2 刺激免疫细胞揭示了 COVID-19 恢复期后效应记忆 CD8，而不是 CD4，T 细胞群体的迅速下降。这些数据提供了关于自然感染后细胞免疫反应的发展和持续的额外信息，并可为 SARS-CoV-2 基于 T 细胞疫苗的进一步开发提供信息。
