SARS-CoV-2 is a novel coronavirus, not encountered before by humans. The wide spectrum of clinical expression of SARS-CoV-2 illness suggests that individual immune responses to SARS-CoV-2 play a crucial role in determining the clinical course after first infection. Immunological studies have focussed on patients with moderate to severe disease, demonstrating excessive inflammation in tissues and organ damage. In order to understand the basis of the protective immune response in COVID-19, we performed a longitudinal follow-up, flow-cytometric and serological analysis of innate and adaptive immunity in 64 adults with a spectrum of clinical presentations: 28 healthy SARS-CoV-2-negative contacts of COVID-19 cases; 20 asymptomatic SARS-CoV-2-infected cases; 8 patients with Mild COVID-19 disease and 8 cases of Severe COVID-19 disease. Our data show that high frequency of NK cells and early and transient increase of specific IgA, IgM and, to a lower extent, IgG are associated to asymptomatic SARS-CoV-2 infection. By contrast, monocyte expansion and high and persistent levels of IgA and IgG, produced relatively late in the course of the infection, characterize severe disease. Modest increase of monocytes and different kinetics of antibodies are detected in mild COVID-19. The importance of innate NK cells and the short-lived antibody response of asymptomatic individuals and patients with mild disease suggest that only severe COVID-19 may result in protective memory established by the adaptive immune response.

中文翻译：

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无症状，轻度和重度病例对SARS-CoV-2感染的不同先天性和适应性免疫反应

SARS-CoV-2是一种新型的冠状病毒，人类以前没有遇到过。SARS-CoV-2疾病的广泛临床表达表明，对SARS-CoV-2的个体免疫反应在确定首次感染后的临床过程中起着至关重要的作用。免疫学研究集中于中度至重度疾病的患者，显示出组织中过度炎症和器官损伤。为了了解COVID-19中保护性免疫应答的基础，我们对64位成人进行了先天性随访，先天性和适应性免疫的流式细胞仪和血清学分析，并进行了一系列临床表现：28种健康的SARS-CoV -2-阴性接触COVID-19病例；20例无症状的SARS-CoV-2感染病例；轻度COVID-19病8例，重度COVID-19病8例。我们的数据表明，NK细胞的高频率以及特异性IgA，IgM和IgG的早期和短暂增加与无症状SARS-CoV-2感染有关。相比之下，在感染过程中相对较晚产生的单核细胞扩增以及高水平和持续水平的IgA和IgG则是严重疾病的特征。在轻度COVID-19中检测到单核细胞的适度增加和抗体的不同动力学。先天性NK细胞的重要性以及无症状个体和轻度疾病患者的短期抗体应答表明，只有严重的COVID-19才能通过适应性免疫应答建立保护性记忆。在感染过程中相对较晚产生的单核细胞扩增以及高和持续水平的IgA和IgG是严重疾病的特征。在轻度COVID-19中检测到单核细胞的适度增加和抗体的不同动力学。先天性NK细胞的重要性以及无症状个体和轻度疾病患者的短期抗体应答表明，只有严重的COVID-19才能通过适应性免疫应答建立保护性记忆。在感染过程中相对较晚产生的单核细胞扩增以及高和持续水平的IgA和IgG是严重疾病的特征。在轻度COVID-19中检测到单核细胞的适度增加和抗体的不同动力学。先天性NK细胞的重要性以及无症状个体和轻度疾病患者的短期抗体应答表明，只有严重的COVID-19才能通过适应性免疫应答建立保护性记忆。