The WHO has declared SARS-CoV-2 outbreak a public health emergency of international concern. However, to date, there was hardly any study in characterizing the immune responses, especially adaptive immune responses to SARS-CoV-2 infection. In this study, we collected blood from COVID-19 patients who have recently become virus-free and therefore were discharged, and analyzed their SARS-CoV-2-specific antibody and T cell responses. We observed SARS-CoV-2-specific humoral and cellular immunity in the patients. Both were detected in newly discharged patients, suggesting both participate in immune-mediated protection to viral infection. However, follow-up patients (2 weeks post discharge) exhibited high titers of IgG antibodies, but with low levels of virus-specific T cells, suggesting that they may enter a quiescent state. Our work has thus provided a basis for further analysis of protective immunity to SARS-CoV-2, and understanding the pathogenesis of COVID-19, especially in the severe cases. It has also implications in designing an effective vaccine to protect and treat SARS-CoV-2 infection.

中文翻译：

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感染SARS-CoV-2的恢复个体的抗病毒免疫特性

世卫组织已宣布SARS-CoV-2爆发为国际关注的突发公共卫生事件。然而，迄今为止，几乎没有任何研究来表征免疫应答，特别是针对SARS-CoV-2感染的适应性免疫应答。在这项研究中，我们从最近无病毒并因此出院的COVID-19患者中收集了血液，并分析了他们的SARS-CoV-2特异性抗体和T细胞反应。我们在患者中观察到SARS-CoV-2特异性的体液和细胞免疫。两者均在新出院的患者中检测到，表明两者均参与了免疫介导的病毒感染保护。但是，随访患者（出院后2周）表现出高滴度的IgG抗体，但病毒特异性T细胞的水平低，表明他们可能进入静止状态。因此，我们的工作为进一步分析针对SARS-CoV-2的保护性免疫，并了解COVID-19的发病机理（尤其是在严重病例中）提供了基础。它在设计保护和治疗SARS-CoV-2感染的有效疫苗方面也具有意义。