Recently, noninvasive diagnostic tests for Helicobacter pylori infection have gained in significance. We have developed a sensitive and specific noninvasive immunoassay based on the detection of an H. pylori circulating antigen (HpCA) in sera from H. pylori-infected individuals. Monospecific antibody and Western blot analyses were used to demonstrate the presence of the target antigen in H. pylori cell lysate and serum samples. A novel enzyme-linked immunosorbent assay (ELISA) was developed for the detection of HpCA in serum. Endoscopic biopsy specimens from the gastric antra of 221 individuals (143 males and 78 females) with dyspeptic symptoms were evaluated for H. pylori infection, with culture used as a "gold standard" for diagnosis. The target H. pylori antigen was identified at 58 kDa. HpCA has been detected by ELISA with high degrees of sensitivity, specificity, and efficiency (>90%), and ELISA results show no significant difference (P > 0.05) from results of H. pylori culture of gastric biopsy specimens. The test's positive and negative predictive values were also high (95 and 86%, respectively). In conclusion, a sensitive and specific immunoassay was developed for the detection of HpCA in human serum. This test can be applied for noninvasive laboratory and field diagnoses of H. pylori infection.

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Meningitis is a common life threatening disease which may be caused by a bacterium, fungus, or virus. Here, the presence of a Helicobacter pylori antigen was investigated in serum and CSF samples from 173 individuals with meningitis. The influence of H. pylori infection on CSF levels of Thl/Th2 cytokines was also evaluated. H. pylori antigen was detected using ELISA and Western blot based on specific anti-H. pylori antibody. Thl/Th2 cytokines (IFN-gamma & IL-10, respectively) were also determined. A target epitope of 58-kDa was detected in selected CSF and serum samples using Western blot. H. pylori antigen was detected in the CSF samples of 75% of meningitis patients showing H. pylori antigen in their sera. A significant correlation (p < 0.001, r = 0.21) was shown between serum and CSF levels of 58-kDa H. pylori antigen. Only the levels of Thl cytokine (IFN-gamma) were significantly higher (p < 0.05) in CSF of meningitis patients positive for H. pylori antigen than negative patients with meningitis. In conclusion, the 58-kDa H. pylori antigen crossed the blood brain barrier and entered the CSF of patients with meningitis. A significant upregulation of Thl response may be associated with H. pylori infection in patients with meningitis.