幽門螺桿菌iceA1、babA2基因檢測及與臨床關系的分析

1、幽門螺桿菌iceA1、babA2基因檢測及與臨床關系的分析        【中文摘要】幽門螺桿菌(Helicobacter pylori,H.pylori,Hp)感染是一個全球性的題目,也是目前人類發(fā)生率最高的慢性細菌感染之一,是慢性胃炎,消化性潰瘍的直接病因,并與胃癌,胃黏膜相關淋巴組織淋巴瘤密切相關。人群中幾乎有一半終身感染H.pylori,但只有部分感染者發(fā)展為明顯的臨床疾病,其中部分原因可能與H.pylori的致病力不同有關。大量流行病學實驗調查資料顯示,cagA、vacA、iceA和babA等基因是H.p

2、ylori的主要毒力因子,與消化性潰瘍,胃癌的發(fā)生密切相關,但東西方的以及國內各地的研究結果并不完全一致。對cagA和vacA的分型研究比較深進,但iceA和babA的研究還存在分歧。iceA是H.pylori與胃黏膜接觸后誘導表達的基因,是人們發(fā)現(xiàn)的新H.pylori毒力相關基因,包括iceA1、iceA2兩個等位基因,分別存在于不同的H.pylori菌株中,為H.pylori的間接致病因子。血型抗原結合黏附素(babA)是目前為止的研究最為明確的H.pylori黏附素之一,它能與胃上皮細胞表面巖藻糖基化的Lewisb血型抗原結合而介導H.pylori與胃上皮細胞的黏附,從而增強H.pylo

3、ri在胃黏膜上定植的能力。babA有兩個等位基因,babA1與babA2,只有babA2具有生物活性。本論文分離了鎮(zhèn)江地區(qū)的70例H.pylori菌株(其中慢性胃炎30例,消化型潰瘍26例,胃癌14例),抽提菌株的基因組DNA,以已知iceA1基因(登錄號:AF 459446.1)及babA2基因(登錄號;AF033654.1)分別設計引物,對iceA1與babA2基因進行鑒定,并對基因的結構特征進行比較,并分析本地區(qū)H.pylori iceA1、babA2基因型分布及其與臨床消化疾病的關系。結果表明,70例H.pylori菌株的iceA1和babA2檢出率分別為68.6%(48/70)和65

4、.7%(46/70)。其中iceA1的分布為胃癌85.7%(12/14),慢性胃炎60%(18/30),消化性潰瘍69.2%(18/26);而babA2的檢出率為胃癌66.7%(8/14),慢性胃炎63.3%(19/30),消化性潰瘍73.1%(19/26)。iceA1基因結構特征的初步分析表明,鎮(zhèn)江地區(qū)H.pylori菌株的iceA1基因有較獨特的結構特征。iceA1基因讀碼框有3個翻譯起始點,鎮(zhèn)江株以第三個起始點翻譯為主,形成較小的蛋白結構,而日本株以第二個起始點翻譯為多,西方美國菌株則以第一個和第二個起始點翻譯蛋白,這樣的結構特點可能會造成毒力的差異。鎮(zhèn)江地區(qū)分離的H.pylori的ic

5、eA1基因的陽性率與亞洲其他國家報道的報道相近,iceA1在胃癌中的檢出率高于慢性胃炎與消化性潰瘍的患者;babA2基因的陽性率明顯高于西方國家,但與胃癌,消化性潰瘍,慢性胃炎等疾病類型的發(fā)生無明顯相關性。');【Abstract】 Helicobacter pylori(H.pylori,Hp) is one of the most major factors inducing pathological changes in human gastric mucosa.It can cause chronic gastritis and gastroduodenal ulcer,and

6、 is correlated with gastric cancer.About half of people in the world were infected with it,but only part of them experience clinical diseases.The reason might be the different pathogenicity of H.pylori.Many results from epidemiological investigation showed that the cagA,vacA,iceA and babA genes are

7、the major virulence factors of H.pylori and are highly correlated with the development of gastroduodenal ulcer and gastric cancer.However,the result is not the same between the west and the east,and varies in different districts of China.The research about the genes cagA and vacA is somewhat deep go

8、ing,while there is still dissension on the research results of iceA and babA.The iceA gene is a newly found gene associated with the virulence of H.pylori.Expression of iceA can be induced by the touch between H.pylori and gastric epithelial cell.There are two alleles,iceA1 and iceA2,which is locate

9、d in different strands.The protein,blood group antigen-binding adhesion(babA),is one of the most understood adhesin of H.pylori.It can bind with the fucose glycosylated blood group antigen Lewisb on the su*ce of the gastric epithelial cell,and mediate the adhesion between H.pylori and gastric epithe

10、lial cell and reinforce the setting ability of H.pylori.babA has two kinds of allele,babA1 and babA2,while only babA2 is bio-active.We isolated H.pylori strains from 70 patients,among which 30 cases were diagnosed as chronic gastritis,26 cases as gastroduodenal ulcer and 14 cases as gastric cancer.T

11、he genome DNA of H.pylori was extracted to amplify the genes by PCR.The primers were designed according to the known sequence of gene iceA1(No.AF 459446.1) and gene babA2(No. AF 033654.1),respectively.Then we identify the products,compare their structural characteristics and analyse the distribution

12、 of gene iceA1 and babA2 in different types of gastroduodenal diseases and the relationship between certain genotype and disease.The results showed that the general positive rate of iceA1 is 68.6%, and that of babA2 is 65.7%.85.7%(12/14) of the patients diagnosed as gastric cancer,60%(18/30) of the

13、patients with chronic gastritis and 69.2%(18/26) of those with gastrodudenal ulcer were infected by iceA1 positive H.pylori.While infection rate of babA2 positive H.pylori is 66.7%(8/14) in gastric cancer,63.3%(19/30) in chronic gastritis and 73.1%(19/26) in gastrodudenal ulcer.Primary analysis on t

14、he structural characteristics of iceA1 indicates that structure of gene iceA1 isolated from H.pylori in Zhenjiang district has some specific characters.The reading frame of gene iceA1 has three translation initiation sites.Majority of the strands from Zhenjiang initiate translation from the third si

15、te and produce smaller protein.While most Japanese strands begin translation from the second sites and the western strands begin from the first or second site.This may cause the difference of virulence among different strand.The positive rate of iceA1 in H.pylori isolated from patients in Zhenjiang is consistent with the published reports from other Asian countries.The positive rate of iceA1 in patients with gastric cancer is hi