[Study on the changing regularity of special antibody and expression of stomach and enteric involvement on SARS-coronavirus infection in the recovery period of severe acute respiratory syndrome].

Objective: To study the change of special antibodies titer IgG, IgM and nucleocapsid to SARS coronavirus (CoV) and observing the expression of stomach and enteric involvement on SARS-CoV infection by monoclonal antibody against N protein of SARS-CoV in the 7-year recovery period among family clustering cases of severe acute respiratory syndrome.

Methods: Special antibody titer to SARS-CoV of 14 patients from 5 different families and their 10 kinfolks continuously tested by IFA and antigen-capturing ELISA methods. Samples were taken in the 1(st) - 7(th) year periods after SARS patients infected by SARS-CoV, being diluted and measured on it titers of three kinds of antibodies. Immunochemical staining with monoclonal antibody (mAb) against N protein of SARS-CoV was used to determine the stomach and enteric tissues among 5 SARS patients with their nucleocapsid antibody titer ascended obviously after 1(st)-7(th) year.

Results: When testing the IgG antibody titer of the 14 SARS patients by IFA method, the average titer was 1/71 (95%CI: 1/58 - 1/85) in the 1(st) year, but began to descend in the following years, and the IgG antibody of the most SARS patients disappeared in the 7(th) year. Regarding the IgM titer, it disappeared in most of the SARS patients 1 year later. The average value of nucleocapsid antibody titer was 1/146 (95%CI: 1/122 - 1/171) in the 1(st) year, and it descended as the IgG antibody titer did. In 5 cases, differences appeared. The nucleocapsid antibody titer was between 1/156 and 1/210 in 3 cases, and 2 cases were normal. Immunochemical staining with mAb against N protein of SARS-CoV was identified in the stomach and enteric tissues of 5 SARS patients with the nucleocapsid antibody titer increased significantly, 1(st)-7(th) year later. The five patients were detected by gastroscopy detection and cell immunohistochemistry test. 3 cases showed N protein antibody positive in the serum, and positive immunohistochemical expression in most of the cytoplasm in the gastric tissue mucous gland epithelial cells. 1 case also expressed in the intestinal tissue slurry columnar epithelium and interstitial cells. The other two cases showed negative on both serum N protein antibody and immunohistochemical expression. The biopsy results of the 5 patients were as follows: 1 case diagnosed as "signet-ring cell carcinoma of the stomach and rectum multiple transfer", 1 case of gastric polyp, 1 case of superficial antral gastritis and 2 cases were normal.

Conclusion: By testing the special IgG, IgM, nucleocapsid antibody to SARS-CoV of the 14 family clustering cases, we found that they all decreased in the 7(th) year, and most of them disappeared. The nucleocapsid antibody titer was related to pathogenetic condition. SARS-CoV was proved to be still present in stomach and enteric tissues of SARS patients with the nucleocapsid antibody titer increased significantly after the 7(th) year.