Longitudinal profile of antibodies against SARS-coronavirus in SARS patients and their clinical significance.
BACKGROUND
Severe acute respiratory syndrome (SARS) is a newly discovered disease caused by a novel coronavirus. The present study studied the longitudinal profile of antibodies against SARS-coronavirus (SARS-CoV) in SARS patients and evaluated the clinical significance of these antibodies.


METHODS
Two methods, ELISA and indirect immunofluorescent assay, were used for the detection of the anti-SARS-CoV IgG and IgM in 335 serial sera from 98 SARS patients. In 18 patients, serum antibody profiles were investigated and antibody neutralization tests were performed from 7 to 720 days after the onset of symptoms.


RESULTS
The ratios of positive IgG/IgM by ELISA were 0/0, 45.4/39.4, 88.6/71.4, 96/88, 100/48.6, 100/30.9, 100/17.1, 100/0 per cent, respectively, on 1-7, 8-14, 15-21, 22-28, 29-60, 61-90, 91-180 and 181-720 days after the onset of symptoms. Antibodies were not detected within the first 7 days of illness, but IgG titre increased dramatically on day 15, reaching a peak on day 60, and remained high until day 180 from when it declined gradually until day 720. IgM was detected on day 15 and rapidly reached a peak, then declined gradually until it was undetectable on day 180. Neutralizing viral antibodies were demonstrated in the convalescence sera from SARS patients.


CONCLUSIONS
The persistence of detectable IgG antibodies and neutralizing viral antibodies for up to 720 days suggest that SARS patients may be protected from recurrent SARS-CoV infection for up to 2 years.
Mo
Hongying
H
Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical College, China.
Zeng
Guangqiao
G
Ren
Xiaolan
X
Li
Hui
H
Ke
Changwen
C
Tan
Yaxia
Y
Cai
Chaoda
C
Lai
Kefang
K
Chen
Rongchang
R
Chan-Yeung
Moira
M
Zhong
Nanshan
N
D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood*; D003289:Convalescence; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D045169:Severe Acute Respiratory Syndrome / Q000276:immunology*
D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M