Study of adhesion molecules and mixed infection in Helicobacter pylori

• Main Authors: Shew-meei Sheu, 許淑美
• Other Authors: Jiunn-Jong Wu
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/62833861373616914030

博士 === 國立成功大學 === 基礎醫學研究所 === 96 === Helicobacter pylori is an important human gastric pathogen. Bacterial adhesion is a prerequisite for colonizing the gastric mucosal surfaces. Many adhesin molecules, such as heat shock proteins, BabA, AlpAB, Hop proteins family, OipA, SabA and Lewis x (Lex) suggested to be involved in the initial colonization of H. pylori. Several investigators have extensively studied the relation between BabA and Leb antigen of host cell. In order to understand the histological role of BabA and Leb interaction in our clinical strains, we collected the gastric tissues and bacteria to analyze the correlation between the babA2 and the Le antigens on gastric tissues. The data showed that all H. pylori isolates had a positive babA2 genotype. The patients with gastric Leb expression had higher the total density of H. pylori (HPD) (p < 0.001) and chronic inflammation score (p < 0.05) than those without Leb expression. The intensity of Leb also had positive corelation with HPD and was an independent factor to affect HPD (p < 0.05). For the 49 patients without gastric Leb expression, those with Lex and Lea expression had higher HPD and Lex and Lea were independent factor to affect HPD (p < 0.05). When the stomach of patients had antral atrophy to decrease the intensity of Leb, a significant increase of the intensity of Lex over the gastric corpus and cardia maintained the bacterial density (p < 0.05). In order to demonstrate the function of bacterial Lex antigen, H. pylori was treated with anti-Le Ab and revealed that an anti-Lex MAb, but not anti-Leb MAb or anti-Ley MAb, could enhance the adhesion of H. pylori strains which expressed high levels of Lex antigen to AGS cells. The adhesion enhancement was not found on H. pylori strain with low level of Lex antigen. Anti-Lex MAb could increase the adhesion of both the wild-type strain and its isogenic babA2 mutant to AGS cells. When AGS cells were pretreated with anti-Lex MAb, the adhesion of the babA2 mutant also increased. Only anti-Lex MAb could promote bacterial agglutination, and the in situ adhesion assay further confirmed that adding anti-Lex MAb resulted in denser bacterial adhesion on the gastric epithelium collected from clinical patients. These results suggest anti-Lex MAb could specifically enhance the adhesion ability of H. pylori strains through a mechanism by which anti-Lex MAb promotes bacterial aggregation and mediates bivalent interaction (antigen-antibody-antigen) between bacteria and host cells. The prevalence of mixed H. pylori infection in Taiwan is not clear. It is worth to investigate whether Taiwanese patients were infected by mixed H. pylori strains and it would affect virulence factors (such as CagA) and disease outcomes. We isolated H. pylori from the antrum and the corpus of 30 dyspeptic patients. Four to eight colonies were randomly collected from each site. The genetic diversity of each isolate was compared by random amplified polymorphic DNA profiles. The phosphorylation level of CagA was analyzed by Western blotting. We found the prevalence of mixed infections was 23.3% (7/30) and different dominant strains were isolated from the antrum and the corpus specimens. In the 23 patients with single strain infections, the acute inflammation score (AIS), chronic inflammation score (CIS), atrophy (AT) and lymphoid follicle (LF) of the antrum were usually more severe than those of the corpus (p <= 0.002). However, for the 7 patients with mixed infections, there were similar CIS, H. pylori density (HPD), AT and LF between the antrum and the corpus (p > 0.05). Moreover, the patients with mixed infections had marginally higher CIS and HPD than those with single infection (p = 0.062 and p = 0.095) in the corpus and had a significantly higher rate of the appearance of intestinal metaplasia (IM) in the antrum (p = 0.005). We further detected the effects of the adhesin expression and acid resistance ability of the strain on gastric distribution. Our preliminary data showed that BabA similar protein and acid resistance ability played some role on strain distribution. In addition, 4-5 isolates of the antrum and the corpus from each of 4 patients with mixed infection infected AGS cells. We found that the CagA phosphorylation was affected by bacterial cagA sequence, its expression and others. These data show that mixed H. pylori strains infecting human stomach have tissue tropism, which could change the histological difference between the antrum and the corpus, and be also associated with the appearance of IM in the antrum. Moreover, there could be many mechanisms involved in the CagA phosphorylation.