Che Xiao-yan, Hao Wei, Qiu Li-wen, Pan Yu-xian, Liao Zhi-yong, Xu Hua, Chen Jin-jun, Hou Jin-lin, Woo Patrick C Y, Lau Susanna K P, Kwok Yung Yuen, Huang Zhen
Central Laboratory, Zhujiang Hospital, First Military Medical University, Guangzhou 510282, China.
Di Yi Jun Yi Da Xue Xue Bao. 2003 Jul;23(7):637-9.
To assess serum antibody responses of patients with severe acute respiratory syndrome (SARS) to nucleocapsid (N) antigen of SARS-associated coronavirus.
The serum levels of IgM and IgG antibodies to N antigen were measured in 200 healthy blood donors and 13 SARS patients at different time points of acute and convalescent phases using indirect enzyme-linked immunosorbent assay (ELISA) with N fusion proteins of SARS-associated coronaviruses.
The IgM positive critical value of 0.233 and IgG of 0.239 were selected as the threshold value for positive results that equals the product of 2.1 and the mean IgM and IgG levels of 200 healthy blood donors. In 13 patients with SARS, the antibody responses to N antigen were not detectable in the first week after the onset of symptoms. The IgM and IgG seroprotection rates were 83.3% and 66.7% respectively in the second week, both reaching 100% at the third week. IgM seroprotection rates was 61.5% in the second month, and 38.5% at third month. The IgG peaked one month after the onset and remained at high levels in the following 2 months.
The antibody responses suggest that N protein of SARS is immunodominant and plays an important role in viral pathogenesis. This ELISA-based test for detecting anti- N antigen may be of significant value for SARS diagnosis.
评估严重急性呼吸综合征（SARS）患者对SARS相关冠状病毒核衣壳（N）抗原的血清抗体反应。
采用间接酶联免疫吸附测定（ELISA）法，以SARS相关冠状病毒的N融合蛋白为抗原，检测200名健康献血者和13例SARS患者在急性期和恢复期不同时间点血清中抗N抗原的IgM和IgG抗体水平。
选取IgM阳性临界值0.233和IgG阳性临界值0.239作为阳性结果的阈值，该阈值等于200名健康献血者IgM和IgG平均水平的2.1倍。13例SARS患者在症状出现后的第一周未检测到对N抗原的抗体反应。第二周IgM和IgG血清保护率分别为83.3%和66.7%，第三周均达到100%。第二个月IgM血清保护率为61.5%，第三个月为38.5%。IgG在发病后一个月达到峰值，并在随后的两个月内保持在高水平。
抗体反应表明SARS的N蛋白具有免疫优势，在病毒致病过程中起重要作用。这种基于ELISA法检测抗N抗原的方法对SARS诊断可能具有重要价值。
