[An immunofluorescence assay for the detection of SARS associated coronavirus antibody based on recombinant nucleocapsid antigen and its application].
OBJECTIVE
To establish a new technique for SARS-CoV antibody test to detect infection of severer acute respiratory syndrome (SARS).


METHODS
Nucleocapsid gene was obtained by reverse transcription and polymerase chain reaction from a SARS patient and inserted into the vector pFastBacHTa expressing baculovirus. Insect Sf9 cells were transfected with the recombinant baculovirus expressing SARS nucleocapsid antigen and then cultured, fixed by acetone so as to make SARS-specific antigen. Immunofluorescence assay (IFA) technique and plaque reduction neutralization test (PRNT) were used to detect 7 samples of sera of 4 newly diagnosed SARS patients collected in different days, 48 samples of convalescent sera of SARS patients, 24 serum samples of healthy person undergoing physical examination, and 40 serum samples from non-SARS patients with fever by double blind test.


RESULTS
The recombinant SARS-specific antigen reacted only with SARS positive sera but not with normal sera. Double blind test showed that 45 of the 46 PRNT positive sera were IFA positive with an accordance rate of 97.8%. 7 samples of sera from 4 SARS patients in acute progressive stage in Guangdong province were all IFA positive. SARS antibody could be detected since the sixth day after onset, and the titer increased from 1:40 to 1:600 on the ninth day.


CONCLUSIONS
Immunofluorescence assay is highly specific and sensitive in detection of SARS. This reagent is safe and easy to prepare.
Zhu
Han-ping
HP
Institute for Virus Disease Research, Center for Disease Prevention and Control of Zhejiang Province, Hangzhou 310009, China.
Zhu
Zhi-yong
ZY
Dong
Guan-mu
GM
Yao
Ping-ping
PP
An
Qi
Q
Weng
Jing-qing
JQ
Lu
Yi-yu
YY
Xu
Fang
F
Lu
Qun-ying
QY
Yan
Ju-ying
JY
Ge
Qiong
Q
Gong
Li-ming
LM
Shi
Wen
W
Li
Min-hong
MH
Zhao
Zhi-ya
ZY
D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008297:Male; D019590:Nucleocapsid Proteins / Q000276:immunology*; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology / Q000302:isolation & purification*; D045169:Severe Acute Respiratory Syndrome / Q000175:diagnosis / Q000821:virology*
D000914:Antibodies, Viral; D019590:Nucleocapsid Proteins