Modulation of Helicobacter pylori induced interleukin-8 synthesis in gastric epithelial cells mediated by cag PAI encoded VirD4 homologue

Background-Strains of Helicobacter pylori carrying the virulence associated cag pathogenicity island (PAI) induce gastric epithelial synthesis of the chemokine interleukin-8 (IL-8), a neutrophil chemoattractant, and thereby a strong inflammatory response during chronic infection of the human gastric mucosa. Previous mutational analyses have shown that many genes in the cag PAI are needed to elicit IL-8 synthesis in gastric epithelial cells, and a lso that some genes are not involved. Aim-To test the possibility that certain genes in the cag PAI also downregu late (modulate) the inflammatory response elicited by cag+ H pylori infecti on. Methods-Cells of L5F11, a derivative of the Kato-3 gastric epithelial cell line that carries an engineered IL-8 promoter-luciferase reporter gene fusi on, were cocultured with H pylori strain 26695 or with an isogenic mutant i n which most of the cag PAI ORF 10 gene, an Agrobacterium virD4 homologue, was deleted. Luciferase activity was measured to assess IL-8 gene transcrip tion and secreted IL-8 was measured by enzyme linked immunosorbent assay to assess synthesis and release of IL-8 protein from gastric epithelial cells . Results-Inactivation of ORF10 led to a 2.8-fold increase in IL-8 gene trans cription and a 3.6-fold increase in IL-8 synthesis and secretion. Conclusions-The results suggest that this VirD4 homologue participates in t he control of inflammation that H pylori infection elicits by downregulatin g (modulating) the strong induction of IL-8 synthesis mediated by other cag encoded proteins.