Characterization of anti-viral immunity in recovered individuals infected by SARS-CoV-2

Chen Dong; Ling Ni; Fang Ye; Meng-Li Chen; Yu Feng; Yong-Qiang Deng; Hui Zhao; Peng Wei; Jiwan Ge; Xiaoli Li; Lin Sun; Pengzhi Wang; Peng Liang; Han Guo; Xinquan Wang; Cheng-Feng Qin; Fang Chen

At the end of 2019, patients with Coronavirus Disease 2019 (COVID- 19) were identified in Wuhan, China 1 , infected by a novel coronavirus, now named as severe acute respiratory syndrome coronavirus 2, SARS-CoV-2. The WHO then declared this outbreak a public health emergency of international concern 2 . The genome sequence of SARS-CoV-2 bears 96% 3 and 79.5% identity to that of a bat coronavirus and SARS-CoV, respectively 4 . Like SARS-CoV and MERS-CoV, SARS-CoV-2 belongs to the beta genus Coronavirus in the Corornaviridae family 5 . Clinically, several papers showed that most COVID-19 patients developed lymphopenia as well as pneumonia with higher plasma levels of pro-inflammatory cytokines in severe cases [6] [7] [8] , suggesting that the host immune system is involved in the pathogenesis 9, 10 . Patients infected by SARS-CoV or MERS-CoV were previously reported to have antibody responses [11] [12] [13] [14] , but exhibited defective expression of type I and II interferon (IFN), indicative of poor protective immune responses [15] [16] [17] . However, to date, there was hardly any study in characterizing the immune responses, especially adaptive immune responses to SARS-CoV-2 infection. Only one COVID-19 patient was shown with nucleocapsid protein (NP)-specific antibody response, in which IgM peaked at day 9 after disease onset and then switched to IgG by week 2 3 , suggesting involvement of humoral immunity. SARS-CoV-2specific T lymphocyte response was unclear. 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.