[A follow up study of total IgM, IgG, nucleoprotein and spike protein antibodies against severe acute respiratory syndrome (SARS) coronavirus in patients with SARS].
OBJECTIVE
To survey the dynamic changing and persistence of the special antibodies, including total IgM, IgG, nucleocapsid protein and spike protein antibodies, against severe acute respiratory syndrome coronavirus (SARS-CoV) in patients with SARS.


METHODS
146 cases, all clinically diagnosed as SARS with positive SARS-CoV IgG, were followed up. 362 serum samples were collected from the onset of the disease to 660 days afterward. Total IgM and IgG against SARS-CoV were tested with commercial ELISA kits. For recombinant nucleoprotein and spike protein, we developed an ELISA to test these two antibodies.


RESULTS
Within 20 days of the onset, the positive rate of anti-SARS-CoV IgM was 46.5% (20/43); it reached a peak after 21 - 40 days (80.6%, 25/31). Then, the positive rate of IgM went down gradually to 8.2% (6/73) until 550 days after the onset. The patient's IgG positive rate was lower (34.9%, 15/43) than that of IgM within 20 days of the onset. Then it went up rapidly to 100%. It remained positive (98.6%, 70/71) until 600 - 660 days after the onset. When N-IgG and S-IgG were tested 40 days after the onset of the disease at three different times, the positive rate of N-IgG (92.5%, 37/40) was higher than that of S-IgG (67.5%, 27/40), but the two structure protein antibodies were always lower than the total IgG.


CONCLUSIONS
In SARS patients with definite clinical and etiological diagnosis, the highest positive rate of the antibodies against SARS-CoV was found at 21 - 40 days after the onset. IgM disappeared almost 500 days (91.8%) after the onset. Total IgG positive rate could reach 100% and 98.6% and the positivity might persist nearly two years. So it is speculated that the total IgG antibody may be positive 3 to 5 years after infection, but it seems that N-IgG and S-IgG keep positive shorter in time than total IgG antibody.
Yan
Hui-ping
HP
Central Laboratory of Infectious Diseases, Beijing Youan Hospital, Capital University of Medical Sciences, Beijing 100069, China. yhp503@vip.sina.com
Tan
Yu-fen
YF
Zhuang
Hui
H
Zhou
Yu-sen
YS
Zhao
Chun-hui
CH
Feng
Xia
X
Jin
Rong-hua
RH
Wu
Hao
H
Fu
Yan
Y
D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D019590:Nucleocapsid Proteins / Q000276:immunology*; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology*; D045169:Severe Acute Respiratory Syndrome / Q000097:blood / Q000276:immunology*; D014759:Viral Envelope Proteins / Q000276:immunology
D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D019590:Nucleocapsid Proteins; D014759:Viral Envelope Proteins