To understand how a protective immune response against SARS-CoV-2 develops over time, we integrated phenotypic, transcriptional and repertoire analyses on PBMCs from mild and severe COVID-19 patients during and after infection, and compared them to healthy donors (HD). A type I IFN-response signature marked all the immune populations from severe patients during the infection. Humoral immunity was dominated by IgG production primarily against the RBD and N proteins, with neutralizing antibody titers increasing post infection and with disease severity. Memory B cells, including an atypical FCRL5⁺ T-BET⁺ memory subset, increased during the infection, especially in patients with mild disease. A significant reduction of effector memory, CD8⁺ T cells frequency characterized patients with severe disease. Despite such impairment, we observed robust clonal expansion of CD8⁺ T lymphocytes, while CD4⁺ T cells were less expanded and skewed toward T_CM and T_H2-like phenotypes. MAIT cells were also expanded, but only in patients with mild disease. Terminally differentiated CD8⁺ GZMB⁺ effector cells were clonally expanded both during the infection and post-infection, while CD8⁺ GZMK⁺ lymphocytes were more expanded post-infection and represented bona fide memory precursor effector cells. TCR repertoire analysis revealed that only highly proliferating T cell clonotypes, which included SARS-CoV-2-specific cells, were maintained post-infection and shared between the CD8⁺ GZMB⁺ and GZMK⁺ subsets. Overall, this study describes the development of immunity against SARS-CoV-2 and identifies an effector CD8⁺ T cell population with memory precursor-like features.

为了了解针对 SARS-CoV-2 的保护性免疫反应如何随着时间的推移而发展，我们对来自轻度和重度 COVID-19 患者感染期间和感染后的 PBMC 进行了表型、转录和库分析，并将其与健康供体 (HD) 进行了比较。I 型 IFN 反应特征标记了感染期间重症患者的所有免疫群体。体液免疫主要是针对 RBD 和 N 蛋白的 IgG 产生，中和抗体滴度增加感染后和疾病严重程度。记忆 B 细胞，包括非典型 FCRL5 ⁺ T-BET ⁺记忆亚群，在感染期间增加，尤其是在轻度疾病患者中。显着减少效应记忆，CD8 ⁺T细胞频率表征患有严重疾病的患者。尽管存在这种损伤，我们观察到 CD8 ⁺ T 淋巴细胞的强大克隆扩增，而 CD4 ⁺ T 细胞扩增较少并且偏向于 T _CM和 T _H 2 样表型。MAIT 细胞也被扩增，但仅限于轻度疾病患者。终末分化的 CD8 ⁺ GZMB ⁺效应细胞在感染期间和感染后均克隆扩增，而 CD8 ⁺ GZMK ⁺淋巴细胞在感染后扩增更多，代表真正的记忆前体效应细胞。TCR 库分析显示，只有高度增殖的 T 细胞克隆型（包括 SARS-CoV-2 特异性细胞）在感染后得以维持，并在 CD8 ⁺ GZMB ⁺和 GZMK ⁺亚群之间共享。总体而言，这项研究描述了针对 SARS-CoV-2 的免疫力的发展，并确定了具有类似记忆前体特征的效应 CD8 ⁺ T 细胞群。