Comparison of effectiveness of whole viral, N and N199 proteins by ELISA for the rapid diagnosis of severe acute respiratory syndrome coronavirus.

Guo, Zhong-min; Lu, Jia-hai; Han, Wen-yu; Liu, Ze-yu; Li, Guo-wei; Liao, Jia-wei; Wang, Shu-min; Wu, Ying-song; Zheng, Huan-ying; Zhong, Nan-shan; Zhu, Xing-quan

BACKGROUND Although severe acute respiratory syndrome (SARS) has been controlled, the subsequently emerging sporadic cases in 2004 emphasize the necessity of developing a rapid diagnostic method, which would be of great help in clinical diagnosis and also wild host screening. This study aims to establish an effective and rapid serological tool for the diagnosis of SARS-CoV by comparison among whole viral, N and N199 proteins by ELISA. METHODS SARS-CoV N and N199 (a truncated nucleocapsid gene) genes were cloned, expressed, identified by Western blotting, and applied in screening of human and swine samples. Sera of SARS convalescent-phase patients, normal human sera, sera of patients with other respiratory diseases, and swine sera were screened by ELISA, with whole SARS-CoV F69, N and N199 proteins as antigens. RESULTS The sensitivity and specificity of N and N199 proteins in human sera diagnosis were approximate (P = 0.743), which was higher than whole viral protein but the difference was not significant (P = 0.234). The N199 protein proved to be more specific in swine sera screening than whole viral and N protein (P < 0.001). CONCLUSION N199 protein is feasible in both clinical diagnosis and SARS-CoV reservoir screening.