Structure of cag pathogenicity island in Japanese Helicobacter pyloriisolates

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Abstract
BACKGROUND cagpathogenicity island (PAI) is reported to be a major virulence factor of Helicobacter pylori. AIM To characterisecagA and the cagPAI in Japanese H pylori strains. METHODS H pylori isolates from Japanese patients were evaluated for CagA by immunoblot, for cagA transcription by northern blot, and for cagA and 13 othercag PAI genes by Southern blot.cagA negative strains from Western countries were also studied. Induction of interleukin-8 secretion from gastric epithelial cells was also investigated. RESULTS All Japanese strains retained cagA. Fifty nine of 63 (94%) strains had all the cag PAI genes. In the remaining four, cag PAI was partially deleted, lacking cagA transcripts and not producing CagA protein. Details of the PAI of these strains were checked; three lacked cagB tocagQ (cagI) and continuously cagS tocag13 (cagII), and the remaining one lacked cagB tocag8. WesterncagA negative strains completely lackedcag PAI includingcagA. Nucleotide sequence analysis in one strain in which the cag PAI was partially deleted showed that the partial deletion contained 25 kb ofcag PAI and thecagA promoter. Interleukin-8 induction was lower with the cag PAI partial deletion strains than with the intact ones. All Japanesecag PAI deleted strains were derived from patients with non-ulcer dyspepsia, whereas 41 of 59 (70%) CagA-producing strains were from patients with peptic ulcers or gastric cancer (pCONCLUSIONS Most Japanese H pylori strains had the intactcag PAI. However, some lacked most of thecag PAI in spite of the presence ofcagA. Thus the presence of thecagA gene is not an invariable marker ofcag PAI related virulence in Japanese strains.