Profiles of antibody responses against severe acute respiratory syndrome coronavirus recombinant proteins and their potential use as diagnostic markers.
A new coronavirus (severe acute respiratory syndrome coronavirus [SARS-CoV]) has been identified to be the etiological agent of severe acute respiratory syndrome. Given the highly contagious and acute nature of the disease, there is an urgent need for the development of diagnostic assays that can detect SARS-CoV infection. For determination of which of the viral proteins encoded by the SARS-CoV genome may be exploited as diagnostic antigens for serological assays, the viral proteins were expressed individually in mammalian and/or bacterial cells and tested for reactivity with sera from SARS-CoV-infected patients by Western blot analysis. A total of 81 sera, including 67 from convalescent patients and seven pairs from two time points of infection, were analyzed, and all showed immunoreactivity towards the nucleocapsid protein (N). Sera from some of the patients also showed immunoreactivity to U274 (59 of 81 [73%]), a protein that is unique to SARS-CoV. In addition, all of the convalescent-phase sera showed immunoreactivity to the spike (S) protein when analyzed by an immunofluorescence method utilizing mammalian cells stably expressing S. However, samples from the acute phase (2 to 9 days after the onset of illness) did not react with S, suggesting that antibodies to N may appear earlier than antibodies to S. Alternatively, this could be due to the difference in the sensitivities of the two methods. The immunoreactivities to these recombinant viral proteins are highly specific, as sera from 100 healthy donors did not react with any of them. These results suggest that recombinant N, S, and U274 proteins may be used as antigens for the development of serological assays for SARS-CoV.
Tan
Yee-Joo
YJ
Institute of Molecular and Cell Biology, Singapore, Republic of Singapore. mcbtanyj@imcb.nus.edu.sg
Goh
Phuay-Yee
PY
Fielding
Burtram C
BC
Shen
Shuo
S
Chou
Chih-Fong
CF
Fu
Jian-Lin
JL
Leong
Hoe Nam
HN
Leo
Yee Sin
YS
Ooi
Eng Eong
EE
Ling
Ai Ee
AE
Lim
Seng Gee
SG
Hong
Wanjin
W
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D000918:Antibody Specificity; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology; D015415:Biomarkers; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D010957:Plasmids; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D045169:Severe Acute Respiratory Syndrome / Q000175:diagnosis* / Q000276:immunology*
D000914:Antibodies, Viral; D000956:Antigens, Viral; D015415:Biomarkers; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M