Evaluation of antibody responses against SARS coronaviral nucleocapsid or spike proteins by immunoblotting or ELISA.
Severe acute respiratory syndrome (SARS)-CoV is a newly emerging virus that causes SARS with high mortality rate in infected people. To study the humoral responses against SARS-CoV, we evaluated nucleocapsid (N) and spike (S) proteins-specific antibodies in patients' sera by Western blotting and enzyme-linked immunosorbent assay (ELISA). Recombinant N and S proteins of SARS-CoV were purified from transformed E. coli. Serum specimens from 40 SARS-CoV-infected patients in the convalescent phase were analyzed by Western blotting using the purified antigens. Serial serum specimens from 12 RT-PCR-confirmed SARS patients were assayed by ELISA using the recombinant N protein as coated antigen. By Western blotting, 97.5% of the SARS patients were positive for N protein-specific antibodies whereas only 47.5% of the samples were positive for S protein-specific antibodies. Using N protein-based ELISA, 10 out of the 12 patients were positive for N protein-specific antibodies and 6 of them showed seroconversion at mean of 16 days after onset of fever. Immunoblotting was useful for detecting the humoral immune response after SARS-CoV infection. Antibodies against SARS-CoV N protein appear at the early stage of infection, therefore, N protein-based ELISA could serve as a simple, sensitive, and specific test for diagnosing SARS-CoV infection.
Huang
Li-Rung
LR
Graduate Institute of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
Chiu
Chi-Ming
CM
Yeh
Shiou-Hwei
SH
Huang
Wen-Hung
WH
Hsueh
Po-Ren
PR
Yang
Wen-Zieh
WZ
Yang
Jyh-Yuan
JY
Su
Ih-Jen
IJ
Chang
Shan-Chwen
SC
Chen
Pei-Jer
PJ
D000595:Amino Acid Sequence; D000914:Antibodies, Viral / Q000096:biosynthesis / Q000097:blood*; D000917:Antibody Formation; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology; D015153:Blotting, Western; D003001:Cloning, Molecular; D000086462:Coronavirus Nucleocapsid Proteins; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology*; D008969:Molecular Sequence Data; D019590:Nucleocapsid Proteins / Q000235:genetics / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000302:isolation & purification; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology*; D045169:Severe Acute Respiratory Syndrome / Q000175:diagnosis / Q000276:immunology*; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000235:genetics / Q000276:immunology*
D000914:Antibodies, Viral; D000956:Antigens, Viral; D000086462:Coronavirus Nucleocapsid Proteins; D008562:Membrane Glycoproteins; D019590:Nucleocapsid Proteins; D011993:Recombinant Fusion Proteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus