title: [An immunofluorescence assay for the detection of SARS associated coronavirus antibody based on recombinant nucleocapsid antigen and its application].
abstract: 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.
authors.affiliation: Institute for Virus Disease Research, Center for Disease Prevention and Control of Zhejiang Province, Hangzhou 310009, China.
authors.forename: Han-ping
authors.initials: HP
authors.lastname: Zhu
authors.forename: Zhi-yong
authors.initials: ZY
authors.lastname: Zhu
authors.forename: Guan-mu
authors.initials: GM
authors.lastname: Dong
authors.forename: Ping-ping
authors.initials: PP
authors.lastname: Yao
authors.forename: Qi
authors.initials: Q
authors.lastname: An
authors.forename: Jing-qing
authors.initials: JQ
authors.lastname: Weng
authors.forename: Yi-yu
authors.initials: YY
authors.lastname: Lu
authors.forename: Fang
authors.initials: F
authors.lastname: Xu
authors.forename: Qun-ying
authors.initials: QY
authors.lastname: Lu
authors.forename: Ju-ying
authors.initials: JY
authors.lastname: Yan
authors.forename: Qiong
authors.initials: Q
authors.lastname: Ge
authors.forename: Li-ming
authors.initials: LM
authors.lastname: Gong
authors.forename: Wen
authors.initials: W
authors.lastname: Shi
authors.forename: Min-hong
authors.initials: MH
authors.lastname: Li
authors.forename: Zhi-ya
authors.initials: ZY
authors.lastname: Zhao
mesh_terms: 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*
chemical_list: D000914:Antibodies, Viral; D019590:Nucleocapsid Proteins