Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of the pandemic human respiratory illness COVID-19, is a global health emergency. While severe acute disease has been linked to an expansion of antibody-secreting plasmablasts, we sought to identify B cell responses that correlated with positive clinical outcomes in convalescent patients. We characterized the peripheral blood B cell immunophenotype and plasma antibody responses in 40 recovered non-hospitalized COVID-19 subjects that were enrolled as donors in a convalescent plasma treatment study. We observed a significant negative correlation between the frequency of peripheral blood memory B cells and the duration of symptoms for convalescent subjects. Memory B cell subsets in convalescent subjects were composed of classical CD24+ class-switched memory B cells, but also activated CD24-negative and natural unswitched CD27+ IgD+ IgM+ subsets. Memory B cell frequency was significantly correlated with both IgG1 and IgM responses to the SARS-CoV-2 spike protein receptor binding domain (RBD). IgM+ memory, but not switched memory, directly correlated with virus-specific antibody responses, and remained stable over time. Our findings suggest that the frequency of memory B cells is a critical indicator of disease resolution, and that IgM+ memory B cells play an important role in SARS-CoV-2 immunity.

中文翻译：

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在 SARS-CoV-2 康复期间检测到的切换和未切换记忆 B 细胞与有限的症状持续时间相关。

严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 是人类呼吸道疾病 COVID-19 大流行的病原体，是全球卫生紧急情况。虽然严重急性疾病与分泌抗体的浆母细胞的扩增有关，但我们试图确定与恢复期患者的积极临床结果相关的 B 细胞反应。我们对 40 名康复的非住院 COVID-19 受试者的外周血 B 细胞免疫表型和血浆抗体反应进行了表征，这些受试者在恢复期血浆治疗研究中作为供体登记。我们观察到外周血记忆 B 细胞的频率与恢复期受试者的症状持续时间之间存在显着的负相关。恢复期受试者的记忆 B 细胞亚群由经典的 CD24+ 类别转换记忆 B 细胞组成，而且还激活了 CD24 阴性和天然未转换的 CD27+ IgD+ IgM+ 亚群。记忆 B 细胞频率与 IgG1 和 IgM 对 SARS-CoV-2 刺突蛋白受体结合域 (RBD) 的反应显着相关。IgM+ 记忆，但不是转换记忆，与病毒特异性抗体反应直接相关，并且随着时间的推移保持稳定。我们的研究结果表明，记忆 B 细胞的频率是疾病消退的关键指标，并且 IgM+ 记忆 B 细胞在 SARS-CoV-2 免疫中发挥重要作用。与病毒特异性抗体反应直接相关，并且随着时间的推移保持稳定。我们的研究结果表明，记忆 B 细胞的频率是疾病消退的关键指标，并且 IgM+ 记忆 B 细胞在 SARS-CoV-2 免疫中发挥重要作用。与病毒特异性抗体反应直接相关，并且随着时间的推移保持稳定。我们的研究结果表明，记忆 B 细胞的频率是疾病消退的关键指标，并且 IgM+ 记忆 B 细胞在 SARS-CoV-2 免疫中发挥重要作用。