Pathogenicity island mediates Helicobacter pylori interaction with the host

An update on Helicobacter pylori microbiology and infection for the new millennium

The finding of the bacterium Helicobacter pylori in patients with symptomatic gastric diseases was a breakthrough for both treatment of peptic ulcer disease and studies of other infectious diseases. Helicobacter pylori infection is rare among the young, indicating that improved childhood living conditions have halted the transmission of the bacterium within families, with a parallel decrease in symptomatic gastroduodenal diseases. Extensive strain variation in H. pylori has been demonstrated at both the genomic and the protein level, and the interstrain variation is higher than in any other bacterium studied so far. Pathogenic markers in H. pylori and host genetics are both of importance for disease outcome. Genotypic or phenotypic markers of H. pylori strains may be used to discriminate patients who should undergo eradication therapy from those who might not benefit from it. Possible positive effects of the infection are still under investigation, and several hypotheses regarding the etiology of diseases in different parts of the stomach have been proposed. To be able to separate the disease-causing infections from the silent infections is a real challenge for the new millennium, and one of the most important issues for therapy and prevention, in the research field of H. pylori.

Helicobacter pylori resists phagocytosis by macrophages: quantitative assessment by confocal microscopy and fluorescence-activated cell sorting

Helicobacter pylori infection of the stomach epithelium is characterized by an infiltration of polymorphonuclear and mononuclear cells. These immune cells contribute to mucosal damage which may eventually lead to gastritis, peptic ulcer, gastric cancer, and/or MALT-associated gastric lymphoma. Here we show that H. pylori inhibits its own uptake, as well as in trans the phagocytosis of Neisseria gonorrhoeae, by human and murine macrophages. This antiphagocytic activity is dependent on the presence of the cag pathogenicity island in the H. pylori genome. We demonstrate that H. pylori also expresses its antiphagocytic activity towards the myelomonocytic cell line JOSKM, thus providing a potent model for the study of the interaction between H. pylori and phagocytes. Our data were obtained using laser confocal microscopy and flow cytometry after quenching the fluorescence of labeled extracellular bacteria. The antiphagocytic activity of H. pylori may explain the persistence of H. pylori and its pathological consequences. The use of cell lines and flow cytometry will hopefully facilitate progress in our understanding of the immune escape of these persistent bacteria.

Helicobacter pylori inhibits phagocytosis by professional phagocytes involving type IV secretion components

Gastric infections by Helicobacter pylori are characteristically associated with an intense inflammation and infiltration of mainly polymorphonuclear lymphocytes (PMNs) and monocytes. The inflammatory response by infiltrated immune cells appears to be a primary cause of the damage to surface epithelial layers and may eventually result in gastritis, peptic ulcer, gastric cancer and/or MALT-associated gastric lymphoma. Our analysis of the interaction between H. pylori and PMNs and monocytes revealed that H. pylori inhibits its own uptake by these professional phagocytes. To some degree, this effect resembles antiphagocytosis by Yersinia enterocolitica. Increasing numbers of bacteria associated per cell are more efficient at blocking their own engulfment. In H. pylori, bacterial protein synthesis is necessary to block phagocytic uptake, as shown by the time and concentration dependence of the bacteriostatic protein synthesis inhibitor chloramphenicol. Furthermore, H. pylori appears broadly to inhibit the phagocytic function of monocytes and PMNs, as infection with H. pylori abrogates the phagocytes' ability to engulf latex beads or adherent Neisseria gonorrhoeae cells. This antiphagocytic phenotype depends on distinct virulence (vir) genes, such as virB7 and virB11, encoding core components of a putative type IV secretion apparatus. Our data indicate that H. pylori exhibits an antiphagocytic activity that may play an essential role in the immune escape of this persistent pathogen.