Pathogenesis of Helicobacter pylori infection.

Research in the last year has provided new insights into the function of the the cag-associated type IV secretion system and the vacuolating toxin VacA. A quite new aspect was disclosed by the finding that Helicobacter pylori in Mongolian gerbils colonizes a very distinct topology in the gastric mucous layer, obviously providing optimal conditions for long-term survival. Further research activities focused on H. pylori ammonia and metal metabolism as well as on bacterial stress defence mechanisms. Differential expression of approximately 7% of the bacterial genome was found at low pH suggesting that H. pylori has evolved a multitude of acid-adaptive mechanisms. VacA was shown to interrupt phagosome maturation in macrophage cell lines as well as to modulate and interfere with T lymphocyte immunological functions. Gastric mucosa as well as the H. pylori-infected epithelial cell line AGS strongly express IL-8 receptor A and B, which might contribute to the augmentation of the inflammatory response. Accumulating evidence implicates genetic variation in the inflammatory response to H. pylori in the etiology of the increased risk of gastric cancer after H. pylori infection. The chronic imbalance between apoptosis and cell proliferation is the first step of gastric carcinogenesis. In this regard, it was demonstrated that coexpression of two H. pylori proteins, CagA and HspB, in AGS cells, caused an increase in E2F transcription factor, cyclin D3, and phosphorylated retinoblastoma protein. Taken together, we now have a better understanding of the role of different virulence factors of H. pylori. There is still a lot to be learned, but the promising discoveries summarized here, demonstrate that the investigation of the bacterial survival strategies will give novel insights into pathogenesis and disease development.