Immune evasion by Helicobacter pylori: gastric spiral bacteria lack surface immunoglobulin deposition and reactivity with homologous antibodies.

BACKGROUND

Helicobacter pylori infection persists in the presence of potent serum and gastric mucosal antibody responses against bacterial antigens. The aim of this article is to report on a study determine whether there is antibody deposition on H. pylori in vivo in the stomach of infected patients and whether gastric and cultured forms of H. pylori differ in their antibody reactivity.

MATERIALS AND METHODS

Serum, gastric biopsies, and antral brushings were obtained from 10 patients having endoscopy. H. pylori was cultured from gastric biopsies. Bacterial samples were stained directly for immunoglobulin deposition and indirectly using rabbit antiurease serum or patient serum. Samples were examined by immunofluorescence microscopy and flow cytometry.

RESULTS

Although spiral bacteria could be identified easily by acridine orange staining and antiurease staining of gastric brushings from H. pylori infected patients, gastric bacteria did not have detectable IgG or IgA present, and only one of five samples could be stained for IgG and IgA indirectly using patient serum. In contrast, cultured bacteria could be stained readily with homologous serum for IgG and IgA in the majority of cases. Low pH inhibited immunoglobulin reactivity with cultured H. pylori.

CONCLUSIONS

Gastric H. pylori may evade humoral defense owing to poor deposition of immunoglobulin in the gastric environment or failure to express surface antigens that are present on cultured forms of H. pylori.