幽门螺杆菌iceA1、babA2基因检测及与临床关系的分析

1、幽门螺杆菌iceA1、babA2基因检测及与临床关系的分析        【中文摘要】幽门螺杆菌(Helicobacter pylori,H.pylori,Hp)感染是一个全球性的题目,也是目前人类发生率最高的慢性细菌感染之一,是慢性胃炎,消化性溃疡的直接病因,并与胃癌,胃黏膜相关淋巴组织淋巴瘤密切相关。人群中几乎有一半终身感染H.pylori,但只有部分感染者发展为明显的临床疾病,其中部分原因可能与H.pylori的致病力不同有关。大量流行病学实验调查资料显示,cagA、vacA、iceA和babA等基因是H.p

2、ylori的主要毒力因子,与消化性溃疡,胃癌的发生密切相关,但东西方的以及国内各地的研究结果并不完全一致。对cagA和vacA的分型研究比较深进,但iceA和babA的研究还存在分歧。iceA是H.pylori与胃黏膜接触后诱导表达的基因,是人们发现的新H.pylori毒力相关基因,包括iceA1、iceA2两个等位基因,分别存在于不同的H.pylori菌株中,为H.pylori的间接致病因子。血型抗原结合黏附素(babA)是目前为止的研究最为明确的H.pylori黏附素之一,它能与胃上皮细胞表面岩藻糖基化的Lewisb血型抗原结合而介导H.pylori与胃上皮细胞的黏附,从而增强H.pylo

3、ri在胃黏膜上定植的能力。babA有两个等位基因,babA1与babA2,只有babA2具有生物活性。本论文分离了镇江地区的70例H.pylori菌株(其中慢性胃炎30例,消化型溃疡26例,胃癌14例),抽提菌株的基因组DNA,以已知iceA1基因(登录号:AF 459446.1)及babA2基因(登录号;AF033654.1)分别设计引物,对iceA1与babA2基因进行鉴定,并对基因的结构特征进行比较,并分析本地区H.pylori iceA1、babA2基因型分布及其与临床消化疾病的关系。结果表明,70例H.pylori菌株的iceA1和babA2检出率分别为68.6%(48/70)和65

4、.7%(46/70)。其中iceA1的分布为胃癌85.7%(12/14),慢性胃炎60%(18/30),消化性溃疡69.2%(18/26);而babA2的检出率为胃癌66.7%(8/14),慢性胃炎63.3%(19/30),消化性溃疡73.1%(19/26)。iceA1基因结构特征的初步分析表明,镇江地区H.pylori菌株的iceA1基因有较独特的结构特征。iceA1基因读码框有3个翻译起始点,镇江株以第三个起始点翻译为主,形成较小的蛋白结构,而日本株以第二个起始点翻译为多,西方美国菌株则以第一个和第二个起始点翻译蛋白,这样的结构特点可能会造成毒力的差异。镇江地区分离的H.pylori的ic

5、eA1基因的阳性率与亚洲其他国家报道的报道相近,iceA1在胃癌中的检出率高于慢性胃炎与消化性溃疡的患者;babA2基因的阳性率明显高于西方国家,但与胃癌,消化性溃疡,慢性胃炎等疾病类型的发生无明显相关性。');【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