| Summary: | 博士 === 國立成功大學 === 基礎醫學研究所 === 102 === Motility mediated by the flagella of H. pylori is important for the cells to move toward the gastric mucus in niches adjacent to the epithelium, then H. pylori uses the adhesin SabA to interact with sialyl-Lex on inflammatory host cells for persistent infection. Previous studies indicated that CsrA was necessary for H. pylori full motility and mouse-infection ability, but its regulatory mechanism is still unclear. In the first part of this study, the clinical association of bacterial motility, SabA-sialyl-Lex interaction, and pathological outcomes was investigated. Ninety-six clinical isolates were screened for bacterial motility, and the expression of SabA of each isolate was confirmed by western blot. The mean diameter in the motility assay was 17 mm, and 8 (8.3%) of the isolates had impaired motility, with a diameter less than 5 mm. H. pylori infected patients were assessed for their bacterial density, sialyl-Lex expression, inflammatory scores and clinical diseases. The results showed that H. pylori density in cardia, the acute inflammatory score in the body locus, and the prevalence rate of gastric atrophy were increased in patients infected with higher motility strains (p = 0.023, 〈 0.001, or 〈 0.001, respectively). The total inflammatory scores (both acute and chronic) and bacterial density dramatically increased in patients expressing the sialyl-Lex antigen and infected with higher motility, SabA-positive H. pylori (p = 0.016, 0.01, or 0.005, respectively). These results suggest the higher motility of H. pylori enhances pathological outcomes, and the SabA-sialyl-Lex interaction has a synergistic effect on virulence of the higher motility strains. In the second part of this study, the molecular mechanism of CsrA regulatory system in H. pylori flagella formation was clarified. The csrA mutant showed loss of motility and 69% of adhesion compared to the wild-type J99 (p 〈 0.001 and = 0.006, respectively), and the revertant restored its motility and adhesion. The bacterial shape and flagellar structure were evaluated by transmission electron microscopy and the results showed csrA mutant was not flagellated. The expression of two major flagellins flaA/flaB and alternative sigma factor rpoN (σ54) were determined by quantitative RT-PCR and western blot. There were only 40% of flaA and 16% of flaB mRNA transcription in the csrA mutant (p 〈 0.01 and 〈 0.001, respectively), and the western blot analysis showed dramatically reduced FlaA/FlaB in the outer membrane protein of csrA mutant. The disruption of csrA also leaded to 48% decreased expression of rpoN, but the degradation rate of rpoN mRNA was not changed in the csrA mutant. These results suggest that CsrA regulates H. pylori flagella formation through controlling the expression of sigma factor rpoN, and thus affects bacterial motility and adhesion. In conclusion, the motility of H. pylori is positively correlated with pathological outcomes, and CsrA regulates H. pylori motility and flagella formation.
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