| Summary: | 碩士 === 國防醫學院 === 微生物及免疫學研究所 === 87 ===
Helicobacter pylori is microaerobic, gram negative bacteria. Its infection can induce gastritis, gastric ulcer, duodenal ulcer, and is closely associated with gastric cancer. Activity of vacuolating cytotoxin A (VacA) of H. pylori is related to development of peptic ulcer. The vacA gene exhibits mosaic expression in the signal (s) and midle (m) regions, and H. pylori with s1/m1 genotype in the vacA gene is significantly associated with duodenal ulcer. The previous studies from our laboratory indicated that all the H. pylori strains isolated from Taiwan exhibited VacA activity, and the activity wasn't correlated with clinical outcome following H. pylori infection.
Total of 108 H. pylori from antrum tissuse with asyptomatic gastritis, duodenal ulcer, gastric ulcer, gastric cancer or MALToma were analyzed for vacA genotype in the signal and middle regions. The result showed that s1a/m2, s1a/m1b, and s1a/m1b-m2 genotypes were detected in 58, 39, and 11 cases, respectively. No s1b, s2, m1 genotype was found. Nucleotide sequences of 485 bp m-region and 259 bp s-region DNA fragments were confirmed byautomatic DNA sequencing. In addition, 3 recombination sites located within the middle region of the vacA gene from 8 H. pylori isolates with m1b/m2 genotypes were identified. Further statistical analysis indicated that H. pylori with s1a/m1b and s1a/m1b/m2 genotypes in the vavA gene exhibited higher titer of VacA toxicity than that of the s1a/m2 genotypes. vavA genotypes were not associated with clinical manifestation following H. pylori infection.
In additon, the HelicoBlot 2.0 kit was used to analyze the association between presence of six H. pylori proteins (116 kDa, 89kDa, 35 kDa, 30 kDa, 26.5 kDa, 19.5 kDa) and clinical manifestation following H. pylori infection. Total of 106 serum samples collected from H. pylori-infected individuals with asyptomatic gastritis, duodenal ulcer, gastric ulcer, gastric cancer or colon cancer analyzed. The results showed that none of investigated of proteins was associated with clinical manifestation following H. pylori infection.
In summary, distribution of vacA genotypes in the signal and middle regions of H. pylori isolated from Taiwan are different from those reported from Western Countries. Most locally isolated H. pylori exhibit VacA toxicity, which is related to the high frequency of s1a, m1b and m1b-m2 alleles in the vacA gene. The defined mechanism of allelic specific VacA cytotoxicity needs to be studied further.
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