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

In order to detect anti-viral immune responses, we first constructed recombinant pET28-N-6XHis by linking 6 copies of His tag to the C-terminus of NP in the pET28-N vector (Biomed, Cat. number: BM2640). Escherichia coli transformed with pET28-N-6xHis was lysed and tested by Coomassie blue staining to confirm NP expression at 45.51 kDa. NP was further purified by Ni-NTA affinity chromatography and gel filtration. The purity of NP was approximately 90% ( Figure S1A ). The presence of NP was subsequently confirmed by anti-Flag antibody ( Figure S1B ). The RBD region of S protein (S-RBD) and main protease (doi: https://doi.org/10.1101/2020.02. 19 .956235) were produced by a baculovirus insect expression system and purified to reach the purity of 90% ( Figure S1A ).