幽门螺杆菌东、西方株CagA的序列差异及其对胃癌细胞生长与凋亡的影响

【背景】幽门螺杆菌(Helicobacter pylori,H.pylori)是胃癌的主要致病因素,其分泌的细胞毒素相关基因A蛋白(Cytotoxin associated gene A,CagA)是目前已知唯一能被H.pylori注入胃上皮细胞并模拟细胞内蛋白发挥作用的癌蛋白,参与胃癌的发生发展。【目的】比较H.pylori东亚株和西方株CagA结构差异,初步探讨H.pylori-CagA对胃癌细胞增殖与凋亡的影响。【方法】对H.pylori东亚株和西方株CagA的核酸及氨基酸序列进行生物信息学分析,构建含东亚株和西方株cagA基因的真核表达载体,转染胃癌细胞AGS,用Western blot法检测CagA蛋白的表达,用CCK8法测定细胞的生长曲线,流式细胞术检测细胞凋亡。【结果】生物信息学分析发现H.pylori东亚、西方菌株CagA的核酸序列和氨基酸序列均存在特征性差异。构建了含东亚、西方菌株cagA基因的表达载体[命名为GZ7/cagA(东亚株)和26695/cagA(西方株)]。与空载体组比较,GZ7/cagA和26695/cagA转染组均表达CagA蛋白,两组比较表达量无显著性差异,GZ7/cagA转染组细胞生长显著增加,而26695/cagA转染组细胞生长显著降低(P0.05)。GZ7/cagA转染组、26695/cagA转染组细胞的凋亡率分别为7.23±0.96及9.17±1.40,均高于空载体组(5.03±0.63),差异有统计学意义(P0.05)。【结论】东亚株与西方株CagA之间有结构和功能的差异,东亚株CagA能促进细胞增殖,而西方株CagA却抑制细胞增殖,但两者均能促进细胞凋亡。     

幽门螺杆菌vacA和cagA基因全长分子系统发育分析

文章从GenBank中下载所有含有vacA和cagA基因的H.pylori菌株的VacA和CagA全长氨基酸序列,利用ClastalX 2.0和MEGA 5.05软件构建VacA和CagA分子系统发育树,探讨两基因之间的分子系统发育关系和不同聚类群的临床感染结果与基因型特征。结果显示,VacA和CagA具有高度相似的分子系统发育树,并且所有H.pylori菌株在系统发育树中具有相同的分布特点,分别聚类为东亚株群1、2和西方株群3个聚类群。其中东亚株群1患萎缩性胃炎比例较高,vacA基因型以s1c/m1b和s1a/m1b为主,cagA基因型以EPIYA-ABD为主;东亚株群2患十二指肠溃疡的比例较高,vacA基因型以s1c/m2和s1a/m2为主,cagA基因型以EPIYA-AB’C为主;西方株群患十二指肠溃疡和胃炎的比例相当,萎缩性胃炎比例较低,vacA基因型以s1a/m1a和s1b/m1a为主,cagA基因型以EPIYA-AB/B’CC为主。这些结果说明,vacA和cagA基因可能具有共进化的遗传关系;东亚株群1、2和西方株群分别具有不同的vacA和cagA基因亚型,这可能与其临床感染结果密切相关,因此,在进行H.pylori相关性疾病分析时,有必要结合vacA和cagA基因型的亚型做深入分析。     

Evolution of cagA oncogene of Helicobacter pylori through recombination

Helicobacter pylori is a gastric pathogen that infects half the human population and causes gastritis, ulcers, and cancer. The cagA gene product is a major virulence factor associated with gastric cancer. It is injected into epithelial cells, undergoes phosphorylation by host cell kinases, and perturbs host signaling pathways. CagA is known for its geographical, structural, and functional diversity in the C-terminal half, where an EPIYA host-interacting motif is repeated. The Western version of CagA carries the EPIYA segment types A, B, and C, while the East Asian CagA carries types A, B, and D and shows higher virulence. Many structural variants such as duplications and deletions are reported. In this study, we gained insight into the relationships of CagA variants through various modes of recombination, by analyzing all known cagA variants at the DNA sequence level with the single nucleotide resolution. Processes that occurred were: (i) homologous recombination between DNA sequences for CagA multimerization (CM) sequence; (ii) recombination between DNA sequences for the EPIYA motif; and (iii) recombination between short similar DNA sequences. The left half of the EPIYA-D segment characteristic of East Asian CagA was derived from Western type EPIYA, with Amerind type EPIYA as the intermediate, through rearrangements of specific sequences within the gene. Adaptive amino acid changes were detected in the variable region as well as in the conserved region at sites to which no specific function has yet been assigned. Each showed a unique evolutionary distribution. These results clarify recombination-mediated routes of cagA evolution and provide a solid basis for a deeper understanding of its function in pathogenesis.     

Sequence Analysis of East Asian cagA of Helicobacter pylori Isolated from Asymptomatic Healthy Japanese and Thai Individuals

CagA, especially East Asian type, is one of the most important virulence factors of Helicobacter pylori, which is believed to contribute to the gastric cancer development. There is extreme sequence heterogeneity on 3' region of cagA gene, demonstrated by the sequence analysis of cagA of H. pylori strains isolated from gastric disease patients. However, whether such heterogeneity of the cagA gene sequence is related to the pathogenicity of H. pylori in the gastric cancer development is not certain. Therefore, in this study, the 3' region of cagA sequences isolated from asymptomatic healthy individuals in Japan and Thailand, which show high and low gastric cancer prevalence, respectively, were analyzed and compared with those from patients with gastric cancer. The CagA sequences analysis in 21 and 12 H. pylori DNA samples obtained from Japanese and Thai individuals, respectively, by the molecular phylogenetic method showed that the sequences were more conserved in the Thai individuals (concordance rates among Thai sequences, 93.9-100%) than in the Japanese individuals (concordance rates among Japanese sequences, 82.8-100%) as shown by unrooted neighbor-joining (N-J) consensus trees constructed with the sequence between Asn869 and Ala967 in CagA. CagA sequences in gastric cancer patients were obtained from published data; analysis of these sequences revealed that CagA sequences from almost all Thai individuals were concentrated in one branch. In contrast, CagA sequences from Japanese individuals were uniformly distributed throughout the N-J consensus tree. These results suggest that the difference in the CagA sequences between asymptomatic healthy Japanese and Thai individuals may be linked to the incidence of gastric cancer in Japan and Thailand.     

Attenuated CagA oncoprotein in Helicobacter pylori from Amerindians in Peruvian Amazon

Population genetic analyses of bacterial genes whose products interact with host tissues can give new understanding of infection and disease processes. Here we show that strains of the genetically diverse gastric pathogen Helicobacter pylori from Amerindians from the remote Peruvian Amazon contain novel alleles of cagA, a major virulence gene, and reveal distinctive properties of their encoded CagA proteins. CagA is injected into the gastric epithelium where it hijacks pleiotropic signaling pathways, helps Hp exploit its special gastric mucosal niche, and affects the risk that infection will result in overt gastroduodenal diseases including gastric cancer. The Amerindian CagA proteins contain unusual but functional tyrosine phosphorylation motifs and attenuated CRPIA motifs, which affect gastric epithelial proliferation, inflammation, and bacterial pathogenesis. Amerindian CagA proteins induced less production of IL-8 and cancer-associated Mucin 2 than did those of prototype Western or East Asian strains and behaved as dominant negative inhibitors of action of prototype CagA during mixed infection of Mongolian gerbils. We suggest that Amerindian cagA is of relatively low virulence, that this may have been selected in ancestral strains during infection of the people who migrated from Asia into the Americas many thousands of years ago, and that such attenuated CagA proteins could be useful therapeutically.     

Identification of Helicobacter pylori and the cagA genotype in gastric biopsies using highly sensitive real-time PCR as a new diagnostic tool

The CagA protein is one of the virulence factors of Helicobacter pylori, and two major subtypes of CagA have been observed, the Western and East Asian type. CagA is injected from the bacteria into gastric epithelial cells, undergoes tyrosine phosphorylation, and binds to Src homology 2 domain-containing protein-tyrosine phosphatase SHP-2. The East Asian type CagA binds to SHP-2 more strongly than the Western type CagA. Here, we tried to distinguish the CagA type by highly sensitive real-time PCR with the objective of establishing a system to detect H. pylori and CagA subtypes from gastric biopsies. We designed primers and probe sets for Western or East Asian-cagA at Western-specific or East Asian-specific sequence regions, respectively, and H. pylori 16S rRNA. We could detect the H. pylori 16S rRNA gene, Western and East Asian-cagA gene from DNA of gastric biopsies. The sensitivity and specificity for H. pylori infection was 100% in this system. In Thai patients, 87.8% (36/41) were cagA-positive; 26.8% (11/41) were Western-cagA positive and 53.7% (22/41) were East Asian-cagA positive, while 7.3% (3/41) reacted with both types of cagA. These results suggest that this real-time PCR system provides a highly sensitive assessment of CagA type as a new diagnostic tool for the pathogenicity of H. pylori infection.     

The role of CagA status in gastric and extragastric complications of Helicobacter pylori.

Two major markers of virulence have been described in H. pylori. The first is a secreted protein (VacA) that is toxic to human cells in tissue culture. This cytotoxin causes vacuolation of epithelial cells in vitro and induces epithelial cell damage in mice. The second is a 40-Kb pathogenicity island for which the gene cagA (cytotoxin-associated gene A) is a marker. Approximately 60% of H. pylori isolates in Western countries are cagA+. The protein encoded by cagA+ has a molecular weight of 120-140 kDa and exhibits sequence heterogeneity among strains isolated from Western and Eastern countries. Although no specific function has been identified for CagA, there is increasing evidence that cagA+ strains are associated with increased intensity of gastric inflammation and increased mucosal concentration of particular cytokines including interleukin 8. Inactivation of picB (Hp 0544) or any of several other genes in the cag island ablates the enhanced IL-8 secretion of human gastric epithelial cells in tissue culture. Furthermore, persons colonized with cagA+ strains have an increased risk of developing more severe gastric diseases such as peptic ulcer and distal (non-cardia) gastric cancer than those harboring cagA- strains. We investigated the role of cagA status in both gastroduodenal and extragastroduodenal disease with H. pylori. Among the diseases limited to the antrum and body of the stomach and the duodenum, we demonstrated a correlation between CagA seropositivity and peptic ulcer disease. We also showed correlation between distal gastric cancer rated and CagA prevalence in populations in both developed and developing countries. In addition, we found that for several Asian populations, the relationship between CagA seropositivity and gastroduodenal diseases was complex. For extragastroduodenal diseases, our results confirmed previous reports that demonstrated that CagA status did not play a role in diseases such as rheumatoid arthritis and hyperemesis gravidarum. However, we found a clear negative association between the presence of a positive response to CagA and esophageal diseases. Therefore, CagA seropositivity (and thus gastric carriage) is associated with increased risks of certain diseases (involving the lower stomach and duodenum) and decreased risks of GERD and its sequelae. This apparent paradox can best be explained by differences in the interaction of cagA+ and cagA- strains with their hosts.     

Structural basis and functional consequence of Helicobacter pylori CagA multimerization in cells

Helicobacter pylori cagA-positive strains are associated with gastric adenocarcinoma. The cagA gene product CagA is delivered into gastric epithelial cells where it localizes to the plasma membrane and undergoes tyrosine phosphorylation at the EPIYA-repeat region, which contains the EPIYA-A segment, EPIYA-B segment, and Western CagA-specific EPIYA-C or East Asian CagA-specific EPIYA-D segment. In host cells, CagA specifically binds to and deregulates SHP-2 phosphatase via the tyrosine-phosphorylated EPIYA-C or EPIYA-D segment, thereby inducing an elongated cell shape known as the hummingbird phenotype. In this study, we found that CagA multimerizes in cells in a manner independent of its tyrosine phosphorylation. Using a series of CagA mutants, we identified a conserved amino acid sequence motif (FPLXRXXXVXDLSKVG), which mediates CagA multimerization, within the EPIYA-C segment as well as in a sequence that located immediately downstream of the EPIYA-C or EPIYA-D segment. We also found that a phosphorylation-resistant CagA, which multimerizes but cannot bind SHP-2, inhibits the wild-type CagA-SHP-2 complex formation and abolishes induction of the hummingbird phenotype. Thus, SHP-2 binds to a preformed and tyrosinephosphorylated CagA multimer via its two Src homology 2 domains. These results, in turn, indicate that CagA multimerization is a prerequisite for CagA-SHP-2 interaction and subsequent deregulation of SHP-2. The present work raises the possibility that inhibition of CagA multimerization abolishes pathophysiological activities of CagA that promote gastric carcinogenesis.     

Virulence genotypes and drug resistance of Helicobacter pylori from Vladivostok, Russia: another feature in the Far East

Helicobacter pylori in Vladivostok, Far Eastern Russia, was investigated during 2004 to 2009. The genotype cagA(+) vacA(+) (s1/m1 or m2) accounted for 74.7%, with cagA(-) vacA(+) (s2/m2) at 11.2%. The CagA EPIYA type was mainly Western ABC, with minor types (ABCCC and novel AAABC) or non-Western/non-East Asia type (AB). Regarding drug resistance, metronidazole resistance was the highest, with a marked decrease in 6 years (from 71.4% to 30.8%); in contrast, levofloxacin and clarithromycin resistance increased. The data indicate that in Vladivostok, H. pylori was mainly the Western (not East Asian) type and dynamic changes in drug resistance occurred during 6 years.     

The diversity of vacA and cagA genes of Helicobacter pylori in East Asia

It has been reported that Helicobacter pylori infection with the type I strain, which expresses the VacA and CagA antigens, is associated with duodenal ulcer. We examined the diversity of vacA and cagA genes in 143 isolates obtained from patients with duodenal ulcer or chronic gastritis in East Asia (two different areas of Japan, Fukui and Okinawa, and also in Hangzhou, China) by polymerase chain reaction (PCR) and sequence analysis. Diversities of cagA and vacA genes were detected in East Asia. The prevalence of cagA-positive H. pylori was significantly different between Fukui and Okinawa (P=0.0032). The prevalence of Western type CagA was significantly higher in Okinawa than in Fukui (P<0.0001). However, there was no significant association between the genotype of cagA and clinical outcome. In Japan, the predominant vacA genotype was s1c/m1b. In contrast, in Hangzhou, the predominant vacA genotype was s1c/m2, and they were all East Asian CagA-positive. These findings suggest that a distinct distribution of the vacA and cagA genotypes is present in East Asia, regardless of clinical outcome.     

Helicobacter pylori CagA transfection of gastric epithelial cells induces interleukin-8

To determine the effect of Helicobacter pylori CagA expression on interleukin-8 (IL-8) induction in AGS cells, cagA and five of its fragments from strains 147A and 147C that vary in the 3' repeat region were cloned into the eukaryotic expression plasmid pSP65SRalpha. IL-8, but not RANTES or IL-Ibeta, levels were increased in AGS cells transfected with 147A-cagA and to a greater extent with 147C-cagA, compared with negative controls. The 5' b fragment from the two strains had similar effects, but the 3' d and e fragments from 147C CagA had greater effects than those from 147A-CagA. When the Western CagA-specific sequence (WSS) of 147C-cagA was replaced with East Asian CagA-specific sequence (ESS) and cloned into pSP65SRalpha as an East/West chimera, there was no significant effect on IL-8 production. Use of specific inhibitors indicates that Src kinase activation, and the mitogen-activated protein (MAP) kinase and NF-kappaB pathways are the major intermediates for CagA effects on IL-8 induction, but the p38 MAP kinase pathway has little effect. These results indicate a direct CagA effect on IL-8 induction by gastric epithelial cells, and indicate signal pathway loci that can be targeted for amelioration.     

Helicobacter pylori genotyping from American indigenous groups shows novel Amerindian vacA and cagA alleles and Asian, African and European admixture

It is valuable to extend genotyping studies of Helicobacter pylori to strains from indigenous communities across the world to better define adaption, evolution, and associated diseases. We aimed to genetically characterize both human individuals and their infecting H. pylori from indigenous communities of Mexico, and to compare them with those from other human groups. We studied individuals from three indigenous groups, Tarahumaras from the North, Huichols from the West and Nahuas from the center of Mexico. Volunteers were sampled at their community site, DNA was isolated from white blood cells and mtDNA, Y-chromosome, and STR alleles were studied. H. pylori was cultured from gastric juice, and DNA extracted for genotyping of virulence and housekeeping genes. We found Amerindian mtDNA haplogroups (A, B, C, and D), Y-chromosome DYS19T, and Amerindian STRs alleles frequent in the three groups, confirming Amerindian ancestry in these Mexican groups. Concerning H.pylori cagA phylogenetic analyses, although most isolates were of the Western type, a new Amerindian cluster neither Western nor Asian, was formed by some indigenous Mexican, Colombian, Peruvian and Venezuelan isolates. Similarly, vacA phylogenetic analyses showed the existence of a novel Amerindian type in isolates from Alaska, Mexico and Colombia. With hspA strains from Mexico and other American groups clustered within the three major groups, Asian, African or European. Genotyping of housekeeping genes confirmed that Mexican strains formed a novel Asian-related Amerindian group together with strains from remote Amazon Aborigines. This study shows that Mexican indigenous people with Amerindian markers are colonized with H. pylori showing admixture of Asian, European and African strains in genes known to interact with the gastric mucosa. We present evidence of novel Amerindian cagA and vacA alleles in indigenous groups of North and South America.     

EPIYA motif is a membrane-targeting signal of Helicobacter pylori virulence factor CagA in mammalian cells

Helicobacter pylori contributes to the development of peptic ulcers and atrophic gastritis. Furthermore, H. pylori strains carrying the cagA gene are more virulent than cagA-negative strains and are associated with the development of gastric adenocarcinoma. The cagA gene product, CagA, is translocated into gastric epithelial cells and localizes to the inner surface of the plasma membrane, in which it undergoes tyrosine phosphorylation at the Glu-Pro-Ile-Tyr-Ala (EPIYA) motif. Tyrosine-phosphorylated CagA specifically binds to and activates Src homology 2-containing protein-tyrosine phosphatase-2 (SHP-2) at the membrane, thereby inducing an elongated cell shape termed the hummingbird phenotype. Accordingly, membrane tethering of CagA is an essential prerequisite for the pathogenic activity of CagA. We show here that membrane association of CagA requires the EPIYA-containing region but is independent of EPIYA tyrosine phosphorylation. We further show that specific deletion of the EPIYA motif abolishes the ability of CagA to associate with the membrane. Conversely, reintroduction of an EPIYA sequence into a CagA mutant that lacks the EPIYA-containing region restores membrane association of CagA. Thus, the presence of a single EPIYA motif is necessary for the membrane localization of CagA. Our results indicate that the EPIYA motif has a dual function in membrane association and tyrosine phosphorylation, both of which are critically involved in the activity of CagA to deregulate intracellular signaling, and suggest that the EPIYA motif is a crucial therapeutic target of cagA-positive H. pylori infection.     

Association between cagA and vacA genotypes and pathogenesis in a Helicobacter pylori infected population from South-eastern Sweden

ABSTRACT: BACKGROUND: Chronic gastritis, peptic ulcer disease, and gastric cancer have been shown to be related toinfection with Helicobacter pylori (H. pylori). Two major virulence factors of H. pylori,CagA and VacA, have been associated with these sequelae of the infection. In this study, totalDNA was isolated from gastric biopsy specimens to assess the cagA and vacA genotypes. RESULTS: Variations in H. pylori cagA EPIYA motifs and the mosaic structure of vacA s/m/i/dayregions were analysed in 155 H. pylori-positive gastric biopsies from 71 individuals usingPCR and sequencing. Analysis of a possible association between cagA and vacA genotypesand gastroduodenal pathogenesis was made by logistic regression analysis. We found that H. pylori strains with variation in the number of cagA EPIYA motif variants present in the samebiopsy correlated with peptic ulcer, while occurrence of two or more EPIYA-C motifs wasassociated with atrophy in the gastric mucosa. No statistically significant relation betweenvacA genotypes and gastroduodenal pathogenesis was observed. CONCLUSIONS: The results of this study indicate that cagA genotypes may be important determinants in thedevelopment of gastroduodenal sequelae of H. pylori infection. In contrast to other studies,vacA genotypes were not related to disease progression or outcome. In order to fullyunderstand the relations between cagA, vacA and gastroduodenal pathogenesis, themechanisms by which CagA and VacA act and interact need to be further investigated.     

Functional variability of cagA gene in Japanese isolates of Helicobacter pylori

CagA protein of Helicobacter pylori is injected into the epithelium, where CagA undergoes tyrosine phosphorylation and activates proliferation signals. However, the importance of these CagA activities for pathogenesis has yet to be resolved. The aim of this study is to analyze the genetic and functional variability of cagA gene of clinical strains in relation to gastric diseases. Thirty-six H. pylori strains were isolated from Japanese patients with various gastric diseases and examined. All 36 strains were found to contain cagA and cagE gene and to induce CagA phosphorylation upon infection. The intensity of CagA phosphorylation expressed in HeLa cells by transfection was highly correlated to the number of R1 region. The phosphorylation intensity was slightly higher in strains from chronic atrophic gastritis (CG); however, the differences were not statistically significant. These CagA proteins also activated the serum response element (SRE) reporter by 5- to 14-fold, above the level of the control. CagA proteins which lack R2 or R3 region exhibited smaller ability for SRE activation. The average of SRE activation was slightly higher in strains from cases of gastric cancer (GC; 11.4+/-1.6), MALT lymphoma (ML; 10.7+/-1.0), and chronic atrophic gastritis (CG; 11.2+/-1.6) than in those of duodenal ulcer (DU; 8.3+/-1.9) or gastric ulcer (GU; 9.0+/-1.1). In summary, most Japanese H. pylori strains contained CagA transport system and induced CagA phosphorylation, and the levels of the intensity of phosphorylation and the ability to induce SRE varied among strains. Although the association between CagA activities and disease outcome shown in this study is not very strong, variety of CagA structure, which induces variable activities, may be one of the reasons why H. pylori induces distinct diseases on host.     

A Comprehensive Sequence and Disease Correlation Analyses for the C-Terminal Region of CagA Protein of Helicobacter pylori

Chronic Helicobacter pylori infection is known to be associated with the development of peptic ulcer, gastric cancer and gastric lymphoma. Currently, the bacterial factors of H. pylori are reported to be important in the development of gastroduodenal diseases. CagA protein, encoded by the cagA, is the best studied virulence factor of H. pylori. The pathogenic CagA protein contains a highly polymorphic Glu-Pro-Ile-Tyr-Ala (EPIYA) repeat region in the C-terminal. This repeat region is reported to be involved in the pathogenesis of gastroduodenal diseases. The segments containing EPIYA motifs have been designated as segments A, B, C, and D; however the classification and disease relation are still unclear. This study used 560 unique CagA sequences containing 1,796 EPIYA motifs collected from public resources, including 274 Western and 286 East Asian strains with clinical data obtained from 433 entries. Fifteen types of EPIYA or EPIYA-like sequences are defined. In addition to four previously reported major segment types, several minor segment types (e.g., segment B′, B′′) and more than 30 sequence types (e.g., ABC, ABD) were defined using our classification method. We confirm that the sequences from Western and East Asian strains contain segment C and D, respectively. We also confirm that strains with two EPIYA segment C have a greater chance of developing gastric cancer than those with one segment C. Our results shed light on the relationships between the types of CagAs, the country of origin of each sequence type, and the frequency of gastric disease.     

Molecular epidemiology and outcome of Helicobacter pylori infection in Thailand: a cultural cross roads

ABSTRACT Background. Thailand is at the cultural cross roads between East and South Asia. It has been suggested that this is also the region where the predominant Helicobacter pylori (H. pylori) genotype changes from East Asian to South Asian. Methods. We compared the molecular epidemiology and outcome of H. pylori infections among different ethnic groups in Thailand (Thai, Thai-Chinese and Chinese). H. pylori isolates were genotyped by polymerase chain reaction based on cagA, cag right end junction and vacA genotypes. Results. Ninety-eight isolates from 38 ethnic Thai, 20 ethnic Chinese and 40 Thai-Chinese were categorized into East Asian (45%), South/Central Asian (26%), Western (1%) or mixed type (29%). The East Asian genotype was the most common among Chinese (85%) and Thai-Chinese (55%) (p <.01 compared to ethnic Thai). The ethnicity of the mother among mixed Thai-Chinese marriages predicted the genotype of the child's H. pylori (e.g. when the mother was Chinese, 84% had East Asian type vs. 29% when the mother was Thai) (p <.001). Gastric cancer was common among ethnic Chinese with East Asian genotype (e.g. all Chinese with gastric cancer or peptic ulcer disease had East Asian genotype, whereas only 40% of Chinese with gastritis had this genotype). Conclusions. Immigration, intermarriage and the variety of H. pylori genotypes in Thailand suggest that Thailand is an ideal site for epidemiological studies attempting to relate H. pylori genotypes and host factors to outcome. Our data also support the hypothesis that the primary caretaker of the children is most likely the source of the infection.     

Diversity of Helicobacter pylori cagA and vacA genes in Costa Rica: its relationship with atrophic gastritis and gastric cancer

BACKGROUND: Associations between Helicobacter pylori gene diversity and gastric cancer have not been reported on in Costa Rica, despite its being one of the countries with the highest gastric cancer incidence and mortality rates in the world. The aim of this study was to determine the prevalence of H. pylori cagA and vacA genes and investigate whether it could be correlated with atrophic gastritis (AG) and gastric cancer (GC) in Costa Rica. MATERIALS AND METHODS: Genomic DNAs from isolates of 104 patients classified into two groups: non-atrophic gastritis group (n = 68) and atrophic gastritis group (n = 36), were subjected to PCR-based genotyping of cagA and vacA genes and their correlation with clinical outcome was investigated. Total DNA extractions from gastric tissues of 25 H. pylori-infected gastric cancer patients were utilized for comparative purposes. RESULTS: The presence of cagA (75.3%), vacA s1b (75.3%), and vacA m1 (74.2%) was detected, and colonization by strains with different vacA genotypes in the same stomach was found in 9.7% of the patients. Age- and sex-adjusted vacA s1b and vacA m1 were associated with GC while only vacA m1 was significantly associated with AG. A tendency for association between cagA and vacA s1b, and AG was reported. CONCLUSIONS: The prevalence status of the cagA and vacA (s1/m1) genes in Costa Rica seems to fall between that found in European/North American and East Asian countries, and both cagA and vacA seem to have clinical relevance in this country.     

Distinct cagA EPIYA Motifs are Associated with Ethnic Diversity in Malaysia and Singapore

Background:  In vitro studies have shown that the biologic activity of CagA is influenced by the number and class of EPIYA motifs present in its variable region as these motifs correspond to the CagA phosphorylation sites. It has been hypothesized that strains possessing specific combinations of these motifs may be responsible for gastric cancer development. This study investigated the prevalence of cagA and the EPIYA motifs with regard to number, class, and patterns in strains from the three major ethnic groups within the Malaysian and Singaporean populations in relation to disease development.
Materials and methods:  Helicobacter pylori isolates from 49 Chinese, 43 Indian, and 14 Malay patients with functional dyspepsia (FD) and 21 gastric cancer (GC) cases were analyzed using polymerase chain reaction for the presence of cagA and the number, type, and pattern of EPIYA motifs. Additionally, the EPIYA motifs of 47 isolates were sequenced.
Results:  All 126 isolates possessed cagA , with the majority encoding EPIYA-A (97.6%) and all encoding EPIYA-B. However, while the cagA of 93.0% of Indian FD isolates encoded EPIYA-C as the third motif, 91.8% of Chinese FD isolates and 81.7% of Chinese GC isolates encoded EPIYA-D ( p  < .001). Of Malay FD isolates, 61.5% and 38.5% possessed EPIYA-C and EPIYA-D, respectively. The majority of isolates possessed three EPIYA motifs; however, Indian isolates were significantly more likely to have four or more ( p  < .05).
Conclusion:  Although, H. pylori strains with distinct cagA -types are circulating within the primary ethnic groups resident in Malaysia and Singapore, these genotypes appear unassociated with the development of GC in the ethnic Chinese population. The phenomenon of distinct strains circulating within different ethnic groups, in combination with host and certain environmental factors, may help to explain the rates of GC development in Malaysia.