Evaluation of recombinant nucleocapsid and spike proteins for serological diagnosis of novel coronavirus disease 2019 (COVID-19)

Pingping Zhang; Qi Gao; Tang Wang; Yuehua Ke; Fei Mo; Ruizhong Jia; Wanbing Liu; Lei Liu; Shangen Zheng; Yuzhen Liu; Luping Li; Yao Wang; Lei Xu; Kun Hao; Ruifu Yang; Shiyue Li; Changqing Lin; Yong Zhao

The copyright holder for this preprint (which was not peer-reviewed) is the rS-RBD, rS-RBD-mFc) and three N proteins (rN, rN1, rN2). Because the S protein is 10 a transmembrane protein, three S protein fragments were prepared using a eukaryotic 11 expression system, while three N proteins were prepared using a prokaryotic 12 expression system. Preliminary evaluation by indirect ELISA revealed that the three S 13 proteins were superior in performance to the three N proteins. Thus, it can be inferred 14 that the eukaryotically expressed HCOV-19 recombinant S protein is suitable for 15 detection of antibodies from COVID-19 patients for early diagnosis, and is superior to 16 the N protein prepared by prokaryotic expression. However, the antigenicity of S 17 proteins and that of the N proteins could not be confirmed in this study, because the 18 influence of prokaryotic expression method used to produce the N proteins is difficult 19 to predict. The prokaryotically expressed recombinant N proteins were all insoluble 20 precipitates, especially rN2, making it likely that their natural conformations were lost 21 All rights reserved. No reuse allowed without permission.