镇江地区H pylori的cagA基因及其3'可变区结构的变化

目的:评估镇江地区H pylori临床株的cagA基因阳性率、了解菌株CagA蛋白的可能分型、其羧端可变区EPIYA的数目以及与临床结果之间有无关联.方法:培养分离来自临床胃十二指肠疾病患者的H pylori,提取基因组DNA,通过PCR方法检测H pylori cagA基因的状况.随机选择不同病种的cagA基因阳性(cagA )的PCR产物,通过转化质粒,进行cagA PCR产物测序,通过ExPASY-Tranlation软件获得cagA基因相应的CagA蛋白的氨基酸序列.国际标准株NCTC11637的cagA基因以及CagA蛋白序列通过搜索NCBI(www.ncbi.nlm.nih.gov)数据库获得.结果:60株H pylori临床株中,56例为cagA ,阳性率达93.3%.20例测序的结果表明,CagA蛋白结构可分为2种类型,19株东亚型和1株西方型.所有19株东亚型均为Yamaoka分型的A型,所有20例菌株的EPIYA的数目均为3个,与临床结果无关联.结论:cagA基因阳性率在不同病种之间无差异.镇江地区H pylori临床株的CagA蛋白的一级结构,与日本、韩国菌株一样,主要为东亚型,其CagA蛋白羧端可变区EPIYA数目均为3个,与临床结果无关联.     

不同地区幽门螺杆菌cagA基因羧基端可变区及其蛋白序列差异分析

目的:比较不同地区H pylori cagA 3'端可变区序列差异及序列的地域特征,分析差异与疾病的相关性.方法:选择本实验室所收集的20例CagA 的PCR产物进行测序,并通过ExPASy-Translation软件推测其氨基酸序列,搜索并收集GenBank中已公布的不同地区3-6个H pyloricagA 3'端可变区序列及其氨基酸序列进行比较分析.结果:cagA蛋白的氨基酸序列可分为具有明显地域特征的东亚型和西方型两类;部分东亚型菌株表现出西方型变异.87.4%的菌株具有3个串联排列的EPIYA基序,8.2%的菌株具有4个或以LEPIYA基序.新发现1条具有区域特征的含有3个氨基酸的序列.cagA蛋白氨基酸序列中的EPIYA数目与临床结果没有相关性.结论:Hpylori cagA基因及其cagA蛋白序列具有明显多态性,可以根据Hpylori cagA 3'端可变区的主要序列差异进行地域分型,cagA 3'端可变区的EPIYA基序的数目与临床结果没有相关性.     

幽门螺杆菌cagA基因3''''端可变区和CagA蛋白EPIYA基序研究进展

细胞毒素相关基因A（cagA）编码CagA蛋白，是研究最多的幽门螺杆菌（H．pylori）基因之一。CagA蛋白经由Ⅳ型分泌系统进入Hpylori黏附的胃上皮细胞，其C-端发生酪氨酸磷酸化，磷酸化的CagA可引起细胞骨架重排、诱导细胞发生形态学变化、增强细胞动力，造成细胞异常运动和增殖．最终导致癌变。因此cagA阳性H．pylori菌株较cagA阴性菌株毒力更强。cagA基因3’端可变区重复序列数目的差异造成了cogA基因结构的多态性以及CagA蛋白大小、功能和细菌毒力（致病性）的差异。因此，cagA基因3’端可变区及其蛋白的EPIYA基序与H．pylori感染临床结果的相关性，成为目前H.pylori研究的热点之一。     

CagA蛋白序列可变区多态性分析

背景:幽门螺杆菌(H.pylori)与胃十二指肠疾病关系密切。由于菌株之间CagAEPIYA基序数目及其间隔的氨基酸序列的不同,导致H.pylori主要毒力因子CagA蛋白的多态性和毒力差异。目前关于CagA蛋白多态性的研究缺乏系统性。目的:系统了解H.pyloriCagA蛋白序列多态性及其特征。方法:采用生物信息学软件序列比对分析与统计学软件数据加工整理技术相结合的方法,对NCBI、swiss_prot/tremble、DDBJ三大蛋白数据库CagA蛋白的97条全长序列和442条3’端部分序列进行多态性分析。结果:CagA蛋白氨基酸序列长短不等,主要是由可变区的变化引起的,可变区平均大小为(114.2±24.9)个氨基酸。539株H.pylori菌株CagA蛋白可变区EPIYA有14种突变型,占7.8%;EPIYA基序平均重复(3.3±0.7)次,最少1次,最多7次。两个EPIYA基序间的间隔序列主要有7种,其中R3C和R4C中的“FPLKRHDKVDELIKVG”以及R4C中的“TIDDLGGP”是西方株特征序列,R3D中的“KIASAGKGVGGFSGAG”和R4D中的“FPLRRSAAVNDLSKVG”、“TIDFDEAN”是东亚株特征序列。EPIYA及其间隔序列的不同组合构成了CagA可变区的17种不同类型。东亚株EPIYA基序重复次数显著少于西方株,而EPIYA-A、EPIYA-B位点数显著多于西方株。结论:CagA蛋白可变区呈现明显多态性,但有其内在规律;进一步研究CagA蛋白多态性与细菌毒力的关系可能揭示出更多H.pylori致病的分子生物学机制。     

中国三个地区幽门螺杆菌CagA羧基端多态性分析

目的分析我国不同地区幽门螺杆菌(H.pylori)的CagA羧基端可变区特征,比较CagA可变区序列差异。方法选取分离自西安、浙江、云南地区的41株H.pylori,PCR扩增CagA羧基端可变区。测序后使用Primer Premier 5软件将核苷酸序列翻译为氨基酸序列,使用Vector NTI Suit6软件将所有菌株的CagA羧基端可变区氨基酸序列进行比较分析。结果41株菌的CagA氨基酸序列可分为东亚型和西方型两类:38株分离株为东亚型模式,其中有31株为典型东亚型,7株为变异东亚型;1株分离株为典型的西方型模式,2株表现为片段缺失的变异西方型。结论中国不同地区H.pylori的CagA蛋白序列以东亚型模式为主,占92.7%(38/41);但在至少2个地区的菌株中发现有2株和1株菌CagA羧基端可变区为西方型模式。     

不同种族幽门螺杆菌菌株CagA蛋白羧基端结构和生物学功能的差异

目的比较不同种族H.pylori菌株CagA蛋白羧基端结构以及诱导AGS细胞延伸、分泌IL-8能力的差异。方法 PCR扩增CagA3′端可变区DNA序列并进行测序,获得CagA3′端可变区氨基酸序列。以不同H.pylori菌株与AGS细胞孵育,观察AGS延伸细胞的百分数,测定细胞培养上清IL-8含量。结果美籍亚裔和美籍非裔菌株的CagA羧基端氨基酸第3个EPIYA前后的氨基酸序列存在明显差异。不同种族cag PAI+H.pylori导致AGS细胞延伸、分泌IL-8能力无明显差异。cag PAI+H.pylori诱导细胞延伸AGS细胞、分泌IL-8的能力明显大于cag PAI-H.pylori。结论不同种族H.pylori菌株CagA蛋白羧基端结构存在差异。H.py-lori菌株诱导AGS细胞延伸、分泌IL-8的能力与cag PAI有关。     

幽门螺杆菌中国株cagA全长基因克隆及其分子特征分析

目的克隆幽门螺杆菌中国株MEL-Hp 27cagA全长基因,并进行分子特征分析。方法参考Hp26695基因组序列,分别针对cagA基因编码区保守序列和位于cagA基因上、下游的基因序列设计两对PCR引物,交叉分段扩增包括cagA基因编码区、5′、3′非编码区在内的全长基因序列,并对cagA基因调控序列、编码序列及源自中国的CagA分子EPIYA基序分布特点进行分析。结果Hp27cagA基因编码区长3510bp,编码1169个氨基酸。5′端非编码区长649bp,-10区、-35区分别位于起始密码子ATG上游89bp和154bp处,3′端非编码区长476bp。Hp27cagA基因编码区核苷酸序列与东亚菌株同源性为96%,与西方菌株的同源性仅为86%左右。Hp27CagA分子存在典型的EPIYA基序,属于ABD型,与国际参考株NCTC11637的AB-CCC型不同。比较源自中国的HpCagA序列的EPIYA基序分布特点,未发现中国Hp分离株之间存在CagAEPIYA基序与疾病结局(胃癌、慢性胃炎和十二指肠溃疡)的聚类关系。结论成功克隆幽门螺杆菌全长ca-gA基因;cagA基因编码区及非编码区序列存在东西方差异;未发现中国Hp分离株之间存在CagA EPIYA基序与疾病结局的聚类关系。     

高原地区上消化道疾病幽门螺杆菌菌型的临床研究

目的研究高原地区上消化道疾病幽门螺杆菌（Helicobacter pylori,Hp）菌型。方法应用Hp尿素酶基因（ure）和细胞毒（cagA）基因引物对330例上消道疾病患者通过聚合酶链反应（PCR）技术,检测ure和cagA基因阳性检出率;用免疫印迹法检测血清ure和CagA抗体。结果 Hp菌株ure和cagA基因阳性检出率分别为90.0%和82.4%;Ure和CagA抗体阳性率分别为89.3%和63.6%;ure和cagA基因表达率分别为99.3%和77.2%。结论高原地区消化道疾病患者中HpcagA基因阳性率较高,CagA蛋白,CagA抗体（Ⅰ型Hp）的表达率亦相应增高。     

胃癌相关幽门螺杆菌毒力和粘附基因进化分析

目的分析幽门螺杆菌(Hp)细胞毒素相关基因羧基末端(cagA 3')可变区和血型抗原结合粘附基因(babA)序列变异及进化特征,探寻致癌相关Hp亚群。方法对150株Hp菌株采用聚合酶链反应(PCR)方法扩增cagA、vacA和babA基因并进行毒力基因分型,比较毒力基因型在胃炎(91株)组和胃癌组(59株)中的分布差异;分别对Hp cagA 3'可变区和babA~+ PCR产物进行一代测序并构建系统进化树。结果在150株Hp菌株中,胃癌组cagA~+基因型为100.00%,胃炎组为93.41%,且大部分(92.14%)为携带东亚型CagA EPIYA-ABD基序的菌株;胃癌组中vacA s1/m1、vacA s1/m2和babA~+基因型Hp菌株分别占44.07%、55.93%和98.31%,胃炎组分别占48.35%、50.55%和98.90%,差异无统计学意义(P均0.05)。基于Hp cagA 3'可变区及babA基因序列构建Neighbour-Joining系统进化树,在cagA 3'Cluster I亚群和babA Cluster I亚群中胃癌组Hp菌株,分别占84.48%和80.36%,胃炎组分别为29.27%和39.47%,差异均有统计学意义(P均0.05)。结论胃癌相关Hp菌株分别在cagA 3'可变区和babA序列构建的系统进化树上明显聚集成亚群,具有更相似的遗传进化特征。     

幽门螺杆菌不同基因型和基因亚型与甲硝唑耐药性的研究

目的研究Helicobacter pylori菌株本身的毒力差异是否与H.pylori菌株对甲硝唑的敏感性有关。方法 用E-test方法检测109株H.pylori菌株对甲硝唑的敏感性;PCR检测H.pylori菌株不同的vacA基因亚型、cagA、iceA和babA2基因型。结果 云南地区甲硝唑耐药率为67.89％;vacA、cagA、iceAl、babA2基因的各种基因亚型和基因型在H.pylori菌株甲硝唑耐药率上无显著性差异。结论 H.pylori菌株本身的毒力差异与H.pylori菌株对甲硝唑的敏感性无关。     

Characterization of CagA variable region of Helicobacter pylori isolates from Chinese patients

AIM: To characterize the CagA variable region of Helicobacter pylori isolates from Chinese patients. METHODS: DNA fragments in CagA variable region were amplified and sequenced respectively from genomic DNA of 19 isolates from patients with gastric cancer and 20 isolates from patients with chronic gastritis. The tendency of phosphorylation in tyrosine(s) of CagA proteins was evaluated subsequently by phosphorylation assay in vivo and in vitro respectively. RESULTS: About 97.44% (38/39) H pylori isolates possessed CagA gene. CagA+ strains contained 2-4 tandem five-amino-acid motifs EPIYA but only one EPIYA had repeated sequence in CagA variable region in different isolates. There was no significant difference between the number of EPIYA motifs in H pylori from patients with different diseases. However, only tyrosine site in EPIYA within repeated sequence could be phosphorylated by AGS cells in vivo although all tyrosine sites in EPIYA could be phosphorylated in vitro. CONCLUSION: CagA in Chinese has no functional difference in perturbing cellular signal pathway among different H pylori isolates.     

幽门螺杆菌CagA C-端功能域特征及其生物学功能研究

目的　克隆源自临床分离的幽门螺杆菌 (Hp)菌株CagADNA序列 ,比较其C 端氨基酸序列与国外菌株的差异 ,并分析其磷酸化能力和转染胃上皮细胞后的生物学功能。方法　从 39株临床分离的HpDNA基因组中用PCR方法扩增cagAC 端DNA ,经琼脂糖凝胶电泳后割胶回收DNA片段进行测序。分别构建cagA的原核细胞和真核细胞表达载体并进行CagAC 端氨基酸磷酸化能力测定。 结果　有 38株菌株检测到CagADNA片段 ,CagA阳性率为 97.4 % (38/ 39)。测序后发现 ,克隆的 38株阳性菌株CagA蛋白均仅含 1个重复序列和 2～ 4个串联的谷氨酸 脯氨酸 异亮氨酸 酪氨酸 丙氨酸(EPIYA)序列 ,且在重复序列的D2区氨基酸序列均为天冬氨酸 苯丙氨酸 天冬氨酸 (DFD)。来自胃癌和非胃癌患者的CagA蛋白串联的EPIYA序列数目差异无显著性。用原核细胞表达的CagA蛋白进行体外磷酸化试验 ,重复序列中的酪氨酸能被磷酸化 ,其余的在EPIYA中的酪氨酸也能被磷酸化 ,但转染的AGS细胞株中仅重复序列中的酪氨酸能被磷酸化。在转染AGS细胞株后少数细胞 (<10 % )因骨架重构而出现典型的“蜂鸟”样改变 ,与直接用Hp感染AGS细胞时类似 ,且对转染的AGS细胞再用Hp感染后 ,其“蜂鸟”样细胞的百分比也无明显增加。结论　源自国人的HpCagA蛋白结构不同于欧美国家     

Analysis of 3'-end variable region of the cagA gene in Helicobacter pylori isolated from Iranian population

Background and Aims:  The 3' region of the cagA gene, the most well-known virulence factor of Helicobacter pylori , contains Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs. Four segments flanking the EPIYA motifs, EPIYA-A, -B, -C, or -D, were reported to play important roles in H. pylori -related gastroduodenal pathogenesis. The aim was to determine the roles of EPIYA segments in gastroduodenal pathogenesis in an Iranian population.
Methods:  A total of 92 cagA -positive Iranian strains isolated from dyspepsia patients with non-ulcer dyspepsia ( n  = 77), peptic ulcer ( n  = 11) and gastric cancer ( n  = 4) were studied. The EPIYA motif genotyping was determined by polymerase chain reaction and sequencing.
Results:  A total of 86 (93.5%) strains had three copies of EPIYA (ABC type), three (3.3%) had four copies (ABCC type) and three (3.3%) had two copies (AB type). The alignment of the deduced protein sequences confirmed that there were no East Asian type EPIYA-D sequences (EPIYATIDFDEANQAG) in Iranian strains. When the prevalence of strains with multiple EPIYA-C segments in Iran was compared with previously published data, it was much lower than that in Colombia and Italy, but was higher than that of Iraq, and the patterns were parallel to the incidence of gastric cancer in these countries.
Conclusion:  The structure of the 3' region of the cagA gene in Iranian strains was Western type. Although we could not find differences between EPIYA types and clinical outcomes, low prevalence of strains with multiple EPIYA-C segments might be reasons for low incidence of gastric cancer in Iran.     

Determinants and consequences of different levels of CagA phosphorylation for clinical isolates of Helicobacter pylori

BACKGROUND & AIMS: The Helicobacter pylori cag pathogenicity island encodes a secretory system that translocates CagA into epithelial cells, where it becomes tyrosine phosphorylated and induces cytoskeletal rearrangements. Strains with more CagA tyrosine phosphorylation motifs are most closely associated with gastric cancer. Here we assess whether clinical strains can deliver CagA, whether strains with different numbers of CagA phosphorylation motifs have CagA phosphorylated to different degrees, and whether this induces different amounts of epithelial cytoskeletal change. METHODS: Forty-four H. pylori strains from South African patients, all cagA gene positive, were cocultured with the gastric adenocarcinoma cell line AGS. CagA expression and phosphorylation were determined by Western blot and interleukin-8 secretion by enzyme-linked immunosorbent assay. The cagA 3' variable regions of 22 strains were sequenced and shown to possess 3-6 phosphorylation motifs. These strains were used to quantify CagA phosphorylation and cytoskeletal rearrangements. RESULTS: cagA genotype and typing of cag pathogenicity island genes were poorly predictive of phenotype. Thirty-four of 44 strains expressed CagA protein that could be delivered to and phosphorylated within AGS cells. Only these 34 strains induced interleukin-8 secretion from AGS cells. Among those strains, the number of CagA tyrosine phosphorylation motifs determined the degree of CagA phosphorylation and the level of biologic activity in terms of degree and extent of AGS cell elongation. CONCLUSIONS: H. pylori strains that deliver CagA with more phosphorylation motifs induce higher levels of CagA phosphorylation in epithelial cells, induce more cytoskeletal changes, and are more likely to be associated with gastric cancer.     

Analysis of the 3′ Variable Region of the <Emphasis Type="Italic">cagA</Emphasis> Gene of <Emphasis Type="Italic">Helicobacter pylori</Emphasis> Isolated in Koreans

CagA protein of Helicobacter pylori is injected into epithelial cells, and it undergoes tyrosine phosphorylation, resulting in inducing cytoskeletal rearrangements. A few studies have suggested that the number of CagA tyrosine phosphorylation motifs (EPIYA) and subtypes of CagA were associated with gastric cancer. This study was performed to characterize the 3' variable regions of the cagA gene of H. pylori and to investigate whether or not there is any relationship between the diversities of cagA and the disease outcome in Korea. Seventy-nine patients (chronic gastritis, 15; duodenal ulcer, 27; benign gastric ulcer, 18; gastric cancer, 19) were enrolled. Biopsy specimens were taken from the antrum for H. pylori culture, and genomic DNA was extracted. PCR and DNA sequence analysis was carried out for the 3′ variable region of the cagA gene. Seventy-eight strains (98.8%) contained three EPIYA motifs and one strain (1.2%) isolated from a patient with duodenal ulcer contained four EPIYA motifs. Seventy-six strains (96.2%) were the East Asian type. In conclusion, there was no significant difference between the number of EPIYA motifs or CagA subtypes and various gastroduodenal diseases in Korea.     

Construction of prokaryotic expression system of 2 148-bp fragment from cagA gene and detection of cagA gene, CagA protein in Helicobacter pylori isolates and its antibody in sera of patients

AIM: To construct a prokaryotic expression system of a Helicobacter pylori (H pylori) cagA gene fragment and establish enzyme-linked immunosorbent assays (ELISA) for detecting CagA and its antibody, so as to understand the manner in which the infection of CagA-expressing H pylori (CagA(+) H pylori) isolates cause diseases. METHODS: H pylori strains in gastric biopsy specimens from 156 patients with positive results in rapid urease test were isolated. PCR was used to detect the frequency of cagA gene in the 109 H pylori isolates and to amplify a 2 148-bp fragment (cagA1) of cagA gene from a clinical strain Y06. A prokaryotic expression system of cagA1 gene was constructed, and the expression of the target recombinant protein (rCagA1) was examined by SDS-PAGE. Western blotting and immunodiffusion assay were employed to determine the immunoreactivity and antigenicity of rCagA1, respectively. Two ELISAs were established to detect CagA expression in 109 H pylori isolates and the presence of CagA antibody in the corresponding patients' sera, and the correlations between infection with CagA(+) H pylori and gastritis as well as peptic ulcer were analyzed. RESULTS: Of all the clinical specimens obtained, 80.8% (126/156) were found to have H pylori isolates and 97.2% of the isolates (106/109) were positive for cagA gene. In comparison with the reported data, the cloned cagA1 fragment possessed 94.83% and 93.30% homologies with the nucleotide and putative amino acid sequences, respectively. The output of rCagA1 produced by the constructed recombinant prokaryotic expression system was approximately 30% of the total bacterial protein. rCagA1 was able to bind to the commercial antibody against the whole-cells of H pylori and to induce the immunized rabbits to produce antibody with an immunodiffusion titer of 1:4. A proportion as high as 92.6% of the H pylori isolates (101/109) expressed CagA and 88.1% of the patients' serum samples (96/109) were CagA antibody-positive. The percentage of CagA(+) H pylori strains (97.9%) isolated from the biopsy specimens of peptic ulcer appeared to be higher than that from gastritis (88.5%), but the difference was not statistically significant (chi (2)=3.48, P>0.05). CONCLUSION: rCagA1 produced by the prokaryotic expression system constructed in this study possesses good immunoreactivity and antigenicity, and the established ELISAs can be used to detect CagA of H pylori and its antibody. H pylori isolates show high frequencies of cagA gene and CagA expression, but the infections by CagA(+) H pylori strains are not the most decisive factors to cause gastric diseases.     

High prevalence of cagA-positive strains in Helicobacter pylori-infected, healthy, young Chinese adults

BACKGROUND: Cytotoxin-associated gene A (cagA) has been implicated as a potential pathogenic marker for Helicobacter pylori-induced severe gastroduodenal diseases. Although the prevalence of cagA-positive strains has been reported in patient populations from developed countries, only limited information from developing countries is available. METHODS: Polymerase chain reaction (PCR) in combination with immunoblot analysis was used to determine the prevalence of cagA and its adjacent cagE genes and to evaluate the expression of CagA protein in 55 H. pylori clinical isolates from China. RESULTS: The expected PCR products derived from H. pylori cagA and cagE genes were identified in all Chinese H. pylori clinical isolates. Similarly, the CagA protein was detected in all 40 isolates tested. CONCLUSIONS: These results demonstrated that the presence of the cagA gene correlated well with expression of the CagA protein in all surveyed Chinese H. pylori isolates and that infection with cagA-positive H. pylori strains is highly common in China and independent of clinical presentation.     

Helicobacter pylori vacA genotypes and cagA status and their relationship to associated diseases

Helicobacter pylori (H. pylori ) is a major causativebacterium of chronic gastritis, peptic ulcer and mucosaassociated lymphoid tissue lymphoma in humans, and associated with an increased risk of gastric cancer[1 -8]. An important virulant factor of H. pylori is the vacuolating cytotoxin ( VacA ) encoded by vacA that induces cytoplasmic vacuolation in target cells both in vitro and in vivo[9-11]. VacA is produced as a 140 kDa precursor which contains an N-terminal signal peptide and an approximately 33 kDa C-terminal outer membrance exporter. The precursor is cleaved at both N-terminal and C-terminal and secreted into the extracellular milieu as a 95 kDa mature protein. The mature protein futher undergoes specific cleavage to yield 37 kDa and 58 kDa subunits[12-14] Although vacA is present in all H. pylori strains, only about 50% to 60% of strains can induce vacuolation of epithelial cells as assessed by the HeLa cell assay. vacA shows considerable genetic variation in H. pylori isolated from all over the world and contains at least two variable regions. The s region exists as sl or s2 allelic types. Among type sl strains, subtypes sla and slb have been identified. The m region occurs as ml or m2 allelic types. Specific vacA genotype of H. pylori strains are associated with the production of the cytotoxin in vitro, epithelial damage in vivo, and clinical consequences[15-27]. The other virulant factor is the cytotoxin-associated protein (CagA) encoded by the cytotoxin-associated gene (cagA). The cagA gene is present in about 60% to 70% of strains and all of these strains express the cagA. The presence of cagA is also associated with the production of the cytotoxin in vitro, and clinical outcome[24-30]. The aim of this study was (i) to identify vacA genotypes and cagA status of H. pylori isolated from Chinese patients; (ii) to evaluation the relatioship beween vacA genotypes, cagA status and related gastroenterological disorders.     

Distinct repeat motifs at the C-terminal region of CagA of Helicobacter pylori strains isolated from diseased patients and asymptomatic individuals in West Bengal, India

Background

Infection with Helicobacter pylori strains that express CagA is associated with gastritis, peptic ulcer disease, and gastric adenocarcinoma. The biological function of CagA depends on tyrosine phosphorylation by a cellular kinase. The phosphate acceptor tyrosine moiety is present within the EPIYA motif at the C-terminal region of the protein. This region is highly polymorphic due to variations in the number of EPIYA motifs and the polymorphism found in spacer regions among EPIYA motifs. The aim of this study was to analyze the polymorphism at the C-terminal end of CagA and to evaluate its association with the clinical status of the host in West Bengal, India.

Results

Seventy-seven H. pylori strains isolated from patients with various clinical statuses were used to characterize the C-ternimal polymorphic region of CagA. Our analysis showed that there is no correlation between the previously described CagA types and various disease outcomes in Indian context. Further analyses of different CagA structures revealed that the repeat units in the spacer sequences within the EPIYA motifs are actually more discrete than the previously proposed models of CagA variants.

Conclusion

Our analyses suggest that EPIYA motifs as well as the spacer sequence units are present as distinct insertions and deletions, which possibly have arisen from extensive recombination events. Moreover, we have identified several new CagA types, which could not be typed by the existing systems and therefore, we have proposed a new typing system. We hypothesize that a cagA gene encoding higher number EPIYA motifs may perhaps have arisen from cagA genes that encode lesser EPIYA motifs by acquisition of DNA segments through recombination events.