[Relation between infection of CagA-positive Helicobacter pylori and upper gastrointestinal diseases]

To study the relation between infection of Helicobacter pylori strains expressing CagA and upper gastrointestinal diseases, and to assess the change of anti-CagA IgG antibody levels after eradication of H. pylori.

Gastric biopsy was conducted among eight hundred and eight patients who received endoscopy to determine the pathological changes of mucosa and infectious status of H. pylori. The presence of serum anti-CagA IgG was detected in each H. pylori-positive patient by ELISA. Eradication therapy by PPI was conducted to the H. pylori-positive individuals. The anti-CagA IgG levels were reexamined among 60 patients whose H. pylori infection failed to be eradicated and 120 patients whose H. pylori infection was successfully eradicated after 3 months and 6 months.

The serum anti-CagA IgG-positive rates were 55.4%, 70.5%, 83.2%, 90.8% and 89.7% in H. pylori-positive patients with chronic superficial gastritis (CSG), chronic atrophic gastritis (CAG), gastric ulcer (GU), duodenal ulcer (DU), and gastric cancer (GC) respectively. The serum anti-CagA IgG-positive rates among the latter 4 groups were significantly higher than that in CSG group, and the serum anti-CagA IgG-positive rates among the latter 3 groups were significantly higher than that in CAG group. The serum anti-CagA IgG-positive rate among patients with CAG was significantly higher than that among patients with CSG (P < 0.05). The CagA-positive rates in the groups of intestinal metaplasia (IM), atypical hyperplasia and GC were significantly higher than those in the groups of CSG and CAG (P < 0.05). By the end of 3 and 6 months after the eradication therapy, the antibody level had decreased from a mean value of (69 +/- 38) U/ml to (47 +/- 30) U/ml and (32 +/- 15) U/ml among 120 patients with successful eradication and the serum antibody reverted to negative only in 23 cases from them. There was no significant change in serum anti-CagA IgG level among 60 patients without successful eradication.

Infection with CagA-positive H. pylori strains is associated with an increased risk of developing more severe gastroduodenal diseases and more severe gastric mucosa lesions. Despite an overall significant decrease of anti-CagA IgG level in sera after H. pylori eradication, this serological method cannot be used to monitor individual treatment effect because the anti-CagA IgG level decreases slowly.