Distinct cagA EPIYA motifs are associated with ethnic diversity in Malaysia and Singapore

CagA toxin and risk of Helicobacter pylori-infected gastric phenotype: A meta-analysis of observational studies

BACKGROUND

Helicobacter pylori (H. pylori) is frequently associated with non-cardia type gastric cancer, and it is designated as a group I carcinogen. This study aimed to systematically review and meta-analyze the evidence on the prevalence of CagA status in people with gastric disorders in the Indo-Pacific region, and to examine the association of CagA positive in the risk of gastric disorders. This study focused on the Indo-Pacific region owing to the high disability adjusted life-years related to these disorders, the accessibility of efficient treatments for this common bacterial infection, and the varying standard of care for these disorders, particularly among the elderly population in the region.

METHODS

Relevant studies were identified in the health-related electronic databases including PubMed, Ovid, Medline, Ovid Embase, Index Medicus, and Google Scholar that were published in English between 1 January 2000, and 18 November 2023. For pooled prevalence, meta-analysis of proportional studies was done, after Freeman-Tukey double arcsine transformation of data. A random-effect model was used to compute the pooled odds ratio (OR) and 95% confidence interval (CI) to investigate the relationship between CagA positivity and gastric disorders.

RESULTS

Twenty-four studies from eight Indo-Pacific countries (Bhutan, India, Indonesia, Malaysia, Myanmar, Singapore, Thailand, Vietnam) were included. Overall pooled prevalence of CagA positivity in H. pylori-infected gastric disorders was 83% (95%CI = 73-91%). Following stratification, the pooled prevalence of CagA positivity was 78% (95%CI = 67-90%) in H. pylori-infected gastritis, 86% (95%CI = 73-96%) in peptic ulcer disease, and 83% (95%CI = 51-100%) in gastric cancer. Geographic locations encountered variations in CagA prevalence. There was a greater risk of developing gastric cancer in those with CagA positivity compared with gastritis (OR = 2.53,95%CI = 1.15-5.55).

CONCLUSION

Findings suggest that the distribution of CagA in H. pylori-infected gastric disorders varies among different type of gastric disorders in the study countries, and CagA may play a role in the development of gastric cancer. It is important to provide a high standard of care for the management of gastric diseases, particularly in a region where the prevalence of these disorders is high. Better strategies for effective treatment for high-risk groups are required for health programs to revisit this often-neglected infectious disease.

Helicobacter pylori cagA, vacA, and iceA genotypes and clinical outcomes: a cross-sectional study in central Vietnam

Helicobacter pylori is the most common cause of gastroduodenal diseases. The concept that cagA-positive H. pylori is a risk factor for gastric cancer appears to be true only for H. pylori strains from Western countries. Other virulent genes may have a synergistic interaction with cagA during pathogenesis. This study aims to investigate H. pylori cagA, vacA, and iceA prevalence, genotypes, and their association to clinical outcomes in Vietnamese patients. The cagA status and vacA and iceA genotypes were determined using the PCR technique on DNA extracted from gastric biopsies of 141 patients with gastroduodenal diseases. After performing molecular analysis for cagA, vacA, and iceA genes, samples with mixed H. pylori strains, positivity, or negativity for both cagA and cagPAI-empty site, or unidentified genotypes were excluded. Finally, 107 samples were examined. The presence of the cagA, vacA, and iceA genes were detected in 77.6%, 100%, and 80.4% of cases, respectively. Notably, cagA( +) with EPIYA-ABD, vacA s1i1m1, vacA s1i1m2, iceA1, and iceA2 accounted for 73.8%, 44.9%, 33.6%, 48.6%, and 31.8% of cases, respectively. Four iceA2 subtypes (24-aa, 59-aa, 94-aa, and 129-aa variants) were found, with the 59-aa variant the most prevalent (70.6%). The cagA( +)/vacAs1i1m1/iceA1 and cagA( +)/vacAs1i1m2/iceA1 combinations were found in 26.2% and 25.1% of cases, respectively. A multivariable logistic regression analysis was performed, after adjusting for age and gender, with the gastritis group was used as a reference control. Statistically significant associations were found between the vacA s1i1m2 genotype, the iceA1 variant, and the cagA( +)/vacAs1i1m2/iceA1 combination and gastric cancer; the adjusted ORs were estimated as 18.02 (95% CI: 3.39-95.81), 4.09 (95% CI: 1.1-15.08), and 16.19 (95% CI: 3.42-76.66), respectively. Interestingly, for the first time, our study found that vacA s1i1m2, but not vacA s1i1m1, was a risk factor for gastric cancer. This study illustrates the genetic diversity of the H. pylori cagA, vacA, and iceA genes across geographical regions and contributes to understanding the importance of these genotypes for clinical outcomes.

EPIYA motifs of Helicobacter pylori cagA genotypes and gastrointestinal diseases in the Iranian population: a systematic review and meta-analysis

Helicobacter pylori is one of the best risk factors for gastric cancer. Recent studies have examined the relationship between virulence factors, in particular CagA toxin, and the development of gastrointestinal diseases. According to the literature, there is a significant relationship between the polymorphism of cagA-EPIYA motifs and progression to severe clinical outcomes. The main goal of our study was to determine the possible association between cagA genotypes and the risk of severe clinical outcomes in the Iranian population. We investigated these ambiguities using a comprehensive meta-analysis study, in which we evaluated data from 1762 Iranian patients for a potential correlation between all cagA gene genotypes and gastrointestinal diseases. According to statistical analysis, the frequencies of cagA genotypes including ABC, ABCC, AB and ABCCC in the Iranian population were estimated at 80.18%, 22.81%, 5.52% and 2.76%, respectively; the ABD genotype was not detected in these PCR-based studies. There was a significant relationship between cagA genotypes ABCC and ABCCC and severe clinical outcomes of infection such as peptic ulcer and gastric cancer. Overall, it can be concluded that there is a positive correlation with the number of copies of EPIYA-C and the increase of gastric cancer. Therefore, according to our results, it seems that the EPIYA-ABCCC motif has a strong positive relationship with gastric cancer in the Iranian population.

Determination of CagA EPIYA motif in Helicobacter pylori strains isolated from patients with digestive disorder

This study was conducted to identify patterns of cagA EPIYA motifs in H. pylori strains isolated from patients with gastrointestinal diseases in Hospitals of Shahrekord, and investigate the association between these biomarkers and clinical outcomes of gastrointestinal diseases due to H. pylori. In this study, 253 patients with gastrointestinal diseases were studied within 1395-1396. Histopathological investigations and urease test showed that 207 isolates were H. pylori-positive. Then, screening using a molecular technique, PCR, confirmed that 159 isolates had cagA. Finally, the pattern and prevalence of the motifs were determined by PCR and identified a number of motifs were sequenced. Results of this study showed that the pattern of motifs was as follows: ABC (140 isolates) (93/7%), ABCC (6 isolates) (3/77%), ABCCC (4 isolates) (2/5%), AB (7 isolates) (4/4%), AC (1 isolate) (0/6%), and BC (1 isolate) (0/6%). Sequencing results showed the presence of changed EPIYA motif in some isolates. CM motif sequence was also seen in all isolates. In this study, no significant association was seen between the prevalence rate of different patterns and clinical symptoms (p = 0.71). There is a slight association between the presence of ABC motifs and the type of digestive disorder (p = 0.056). Results indicated that ABC was the most frequently seen pattern however, in such that positive cases of ABC motifs were more common in gastritis. All isolates had kinase phosphorylation region, and the observed pattern in this region was a generally western type (ABC).

Helicobacter pylori antibiotic resistance and correlation with cagA motifs and homB gene

Objectives: Helicobacter pylori (H. pylori) infection caused by antibiotic-resistant strains represents a major public health threat that aggressively promotes gastric cancer progression. Antibiotic resistance evaluation is immensely important to counteract its emergence. Here we merely determine the prevalence of antibiotic resistance in H. pylori isolates and its correlation with cagA motifs and the homB gene. Methods: The antibiotic resistance pattern was investigated on 128 H. pylori isolated strains utilizing the disk diffusion method and study the correlation between it and the presence of pathogenic genes, cagA EPIYA motifs and homB gene, were accurately detected using the PCR. Results: The resistance rates to four antibiotics were 70.1% for metronidazole, 35.5% for amoxicillin, 7.2% for clarithromycin and 8.2% for tetracycline. Resistance phenotypes were separated into two groups, single resistance (63.2%) and multi-resistance (12.5%). The prevalence of cagA-ABCC resistant strains and homB⁺ resistant strains was significantly higher in cancer (p = 0.04 and p = 0.01, respectively) than those of other diseases. The prevalence of cagA-homB ⁺ resistance strains was 21.8% and had a significant correlation with PUD. A significant relationship was observed between amoxicillin resistant rate with ABC-homB (p = 0.0006). Conclusion: The Resistance rate to selected antibiotics in Shiraz is higher than years ago. The presence of cagA-homB ⁺ is associated with antibiotic resistance and also homB can be used as a marker to antibiotic resistance status prediction in H. pylori isolated in this area.

Tailor-Made Detection of Individual Phosphorylated and Non-Phosphorylated EPIYA-Motifs of Helicobacter pylori Oncoprotein CagA

The gastric pathogen and carcinogen Helicobacter pylori(H. pylori) encodes a type IV secretion system for translocation of the effector protein CagA into host cells. Injected CagA becomes tyrosine-phosphorylated at the five amino acid residue Glutamate-Proline- Isoleucine-Tyrosine-Alanine (EPIYA)-sequence motifs. These phosphorylated EPIYA-sites represent recognition motifs for binding of multiple host factors, which then manipulate signaling pathways to trigger gastric disease. Thus, efficient detection of single phosphorylated EPIYA-motifs in CagA is required. Detection of phospho-CagA is primarily performed using commercial pan-phosphotyrosine antibodies. However, those antibodies were originally generated to recognize many phosphotyrosines in various mammalian proteins and are not optimized for use in bacteria. To address this important limitation, we synthesized 11-mer phospho- and non-phospho-peptides from EPIYA-motifs A, B, and C, and produced three phospho-specific and three non-phospho-specific rabbit polyclonal CagA antibodies. These antibodies specifically recognized the corresponding phosphorylated and non-phosphorylated EPIYA-motifs, while the EPIYA-C antibodies also recognized the related East-Asian EPIYA-D motif. Otherwise, no cross-reactivity of the antibodies among EPIYAs was observed. Western blotting demonstrated that each EPIYA-motif can be predominantly phosphorylated during H. pylori infection. This represents the first complete set of phospho-specific antibodies for an effector protein in bacteria, providing useful tools to gather information for the categorization of CagA phosphorylation, cancer signaling, and gastric disease progression.

The antibiotic resistance of Helicobacter pylori to five antibiotics and influencing factors in an area of China with a high risk of gastric cancer

Background

H. pylori exhibits antibiotic resistance with regional differences. In this paper, we explored antibiotic resistance of H. pylori to five antibiotics in an area with a high risk of gastric cancer.

Results

H. pylori resistance rates to metronidazole, levofloxacin, clarithromycin, amoxicillin, and tetracycline were 78.0, 56.0, 31.0, 9.0, and 15.0%, respectively. Double, triple, quadruple, and quintuple resistance rates were 23, 20, 6, and 4%, respectively. The clarithromycin and multidrug resistance rates were significantly higher in males than females (clarithromycin: 44.4% vs 15.2%, respectively, P = 0.002; multidrug: 75.5% vs 37.2%, respectively; P < 0.001). During the three periods of 1998–1999, 2002–2004 and 2016–2017, the resistance rates to levofloxacin and amoxicillin were increasing (OR: 2.089, 95%CI: 1.142–3.821, P = 0.017; and OR: 5.035, 95%CI: 1.327–19.105, P = 0.018, respectively). The antibiotic resistance rates were unassociated with the host disease state. Metronidazole resistance was lower in the vacAs1m1/m2 group than the vacAs1m1m2 group (65% vs 85.7%, respectively; P = 0.026). As for levofloxacin resistance, it was higher with cagA⁺ than cagA⁻ (60.9% vs 23.1%, respectively; P = 0.020) but lower with slyD⁺ than slyD⁻ (41.4% vs 68.5%, respectively; P = 0.009). Clarithromycin had a lower resistance rate with iceA⁺⁺ than iceA⁻⁺ (19.7% vs 52.4%, respectively; P = 0.017). For amoxicillin, the iceA⁺⁺ group had a lower resistance rate than the iceA⁻⁻ group (1.6% vs 27.8%, respectively; P = 0.009).

Conclusions

The total resistance rates of H. pylori to metronidazole, levofloxacin, clarithromycin, amoxicillin, and tetracycline were high in Zhuanghe. The resistanc rates to levofloxacin and amoxicillin increased over time. Clarithromycin resistance was associated with male and iceA. The resistance of metronidazole was related to vacA. Levofloxacin resistance was concerned with cagA and slyD and amoxicillin resistance was concerned with iceA. While, the antibiotic resistance of H. pylori had nothing to do with the status of gastric disease.

A Review of Gastric Cancer Research in Malaysia

Incidence rates of gastric cancer in Malaysia has declined by 48% among males and 31% among females in the latest reporting period of 13 years. Malays used to have age-standardized-rates only a fifth of those in Chinese and Indians, but the incidence among them is slightly rising even as the rates drop in the other races. Besides ethnicity, a low level of education, high intake of salted fish and vegetables, H pylori infection and smoking are risk factors. Consumption of fresh fruit and vegetable is protective. Variation in the strains of H pylori infection affect gastric cancer risk, with hspEAsia isolates among Chinese appearing linked to a high incidence than with hpAsia2 or hpEurope strains among Indians and Malays. It was reported in the 1980s that only about 3% of patients presented with early gastric cancer, but more encouraging rates reaching 27% with Stage 1 and 2 disease have been reported in the twenty-first century from leading centres. More tumours occur in the distal stomach except in Kelantan, where the incidence is low and main site is the cardia. Prompt endoscopy is advocated and open access, with direct referrals, to such services using a weighted scoring system should be more utilized. In view of the high rate of late disease laparoscopic staging unnecessary laparotomy needs to be avoided. Late presentation of gastric cancer however, is still predominant and the mortality to incidence ratio is relatively high. Besides seeking to reduce risk factors and achieve early detection, implementation of improved care for patients with late disease must be promoted in Malaysia.

The Story of Helicobacter pylori: Depicting Human Migrations from the Phylogeography

Helicobacter pylori is a spiral-shaped Gram-negative bacterium, which has infected more than half of the human population. Besides its colonisation capability, the genetic diversity of H. pylori is exceptionally well structured and belongs to several distinct genetic populations, depicting various prehistorical human migration events. The evolutionary relationship of H. pylori with its host had been started at least ~100,000 years ago. In addition, the discovery of the ancient H. pylori genome from a European Copper Age glacier mummy, "The Iceman", gave the idea that the second out of Africa migration resulted in the recombinant population of hpEurope at least about 5300 years ago. The advancement of next-generation genome sequencing discovered the prophage of H. pylori and could discriminate the big population of hpEurope into two different subpopulations. In addition, the implementation of the chromopainter/fineSTRUCTURE algorithm to the whole genome analysis of H. pylori provides a finer resolution population genetics of H. pylori; therefore it could also depict the recent migrations within the past 500 years after colonial expansion. This discovery shows that the genetic recombination of H. pylori strains is far more dynamic compared to its human host, but still maintains the similarity to its host, suggesting that H. pylori is a handy tool to reconstruct the human migration both in the past and the recent.

Lessons learnt from the epidemiology of Helicobacter pylori infection in Malaysia: JGHF Marshall and Warren Lecture 2017

The study of Helicobacter pylori in Malaysia has given several important insights into the epidemiology of the infection and pathogenesis of disease. Malaysia has a multiracial Asian population with three major Asian races living together-Malay, Chinese, and Indian. Races remain fairly distinct because of a paucity of interracial marriages. The "Racial Cohort Hypothesis" proposes that the infection occurs within racial groups rather than between. As such, the high prevalence among Indians (> 50%) and Chinese (40-50%) reflects the high prevalence in their countries of origin even though migration had taken place more than two generations before. The Malays have a comparatively low prevalence of about 10-20%. Despite the high prevalence of H. pylori, the Indians have a low gastric cancer incidence of less than 10 per 100 000 per year. This is in contrast to the Chinese who has an incidence in excess of 20 per 100 000 per year. We have called this the "Indian Enigma." The reason for this enigma is unclear and is the result of interaction between bacterial virulence factors, host susceptibility, and environmental factors. Phylogenetically, Chinese bacterial strains are distinct from Indians and Malays and are predominantly hpEastAsia/hsp EAsia. CagA EPIYA motifs among Chinese belong predominantly to the more virulent ABD motif. There is no clear distinguishing profile among host genetic factors. Environmental factors particularly diet may play an important role. Indians consume chilies and curries, which may be gastro protective, whereas Chinese consume more preserved and salted foods, which are thought to be carcinogenic.

Association of CagA EPIYA-D or EPIYA-C phosphorylation sites with peptic ulcer and gastric cancer risks: A meta-analysis

BACKGROUND

Increasingly, studies have focused on the relationship between Helicobacter pylori (H pylori) cytotoxin associated gene A protein (CagA) Glu-Pro-Ile-Tyr-Ala (EPIYA)-D motifs or multiple EPIYA-C phosphorylation sites and peptic ulcer disease (PUD) or gastric cancer (GC) risk. However, the conclusions have been inconsistent. The aim of this meta-analysis was to evaluate whether 1 CagA EPIYA-D motif or multiple EPIYA-C phosphorylation sites were associated with PUD or GC risk.

MATERIALS AND METHODS

A literature search was performed in PubMed, Web of Science, Wanfang Data, Excerpt Medica Database, and the Chinese National Knowledge Infrastructure database to identify eligible research. We analyzed the odds ratios (OR) and 95% confidence intervals (CI) to assess the strength of association.

RESULTS

Compared with 1 EPIYA-C motif in Asian populations, 1 EPIYA-D site was associated with an increased GC risk (OR=1.91, 95% CI=1.19-3.07, P = .008). However, 1 EPIYA-D motif was not significantly associated with PUD (OR = 0.90, 95% CI = 0.46-1.76, P = .764), gastric ulcer (GU) (OR = 0.85, 95% CI = 0.27-2.63, P = .771), or duodenal ulcer (DU) (OR = 0.89, 95% CI = 0.25-3.16, P = .859) risk. Compared with no more than 1 EPIYA-C motif, multiple motifs were associated with increased PUD (OR = 2.33, 95% CI = 1.29-4.20, P = .005) and DU (OR = 2.32, 95% CI = 1.08-5.00, P = .031) risk in Asia and GC risk in the United States and Europe (OR = 3.28, 95% CI = 2.32-4.64, P < .001). Multiple EPIYA-C sites were not associated with GU risk (OR = 4.54, 95% CI = 0.95-21.83, P = .059). There was no publication bias identified in these comparisons.

CONCLUSIONS

In Asia, 1 EPIYA-D motif was significantly associated with increased GC risk. Multiple EPIYA-C motifs were associated with increased PUD and DU risk, particularly in Asia. In the United States and Europe, multiple EPIYA-C motifs were associated with increased GC risk. Therefore, detection of polymorphic CagA EPIYA motifs may improve clinical prediction of disease risk.

Systematic analysis of phosphotyrosine antibodies recognizing single phosphorylated EPIYA-motifs in CagA of East Asian-type Helicobacter pylori strains

BACKGROUND

Highly virulent strains of the gastric pathogen Helicobacter pylori encode a type IV secretion system (T4SS) that delivers the effector protein CagA into gastric epithelial cells. Translocated CagA undergoes tyrosine phosphorylation by members of the oncogenic c-Src and c-Abl host kinases at EPIYA-sequence motifs A, B and D in East Asian-type strains. These phosphorylated EPIYA-motifs serve as recognition sites for various SH2-domains containing human proteins, mediating interactions of CagA with host signaling factors to manipulate signal transduction pathways. Recognition of phospho-CagA is mainly based on the use of commercial pan-phosphotyrosine antibodies that were originally designed to detect phosphotyrosines in mammalian proteins. Specific anti-phospho-EPIYA antibodies for each of the three sites in CagA are not forthcoming.

RESULTS

This study was designed to systematically analyze the detection preferences of each phosphorylated East Asian CagA EPIYA-motif by pan-phosphotyrosine antibodies and to determine a minimal recognition sequence. We synthesized phospho- and non-phosphopeptides derived from each predominant EPIYA-site, and determined the recognition patterns by seven different pan-phosphotyrosine antibodies using Western blotting, and also investigated representative East Asian H. pylori isolates during infection. The results indicate that a total of only 9-11 amino acids containing the phosphorylated East Asian EPIYA-types are required and sufficient to detect the phosphopeptides with high specificity. However, the sequence recognition by the different antibodies was found to bear high variability. From the seven antibodies used, only four recognized all three phosphorylated EPIYA-motifs A, B and D similarly well. Two of the phosphotyrosine antibodies preferentially bound primarily to the phosphorylated motif A and D, while the seventh antibody failed to react with any of the phosphorylated EPIYA-motifs. Control experiments confirmed that none of the antibodies reacted with non-phospho-CagA peptides and in accordance were able to recognize phosphotyrosine proteins in human cells.

CONCLUSIONS

The results of this study disclose the various binding preferences of commercial anti-phosphotyrosine antibodies for phospho-EPIYA-motifs, and are valuable in the application for further characterization of CagA phosphorylation events during infection with H. pylori and risk prediction for gastric disease development.

The EPIYA-ABCC motif pattern in CagA of Helicobacter pylori is associated with peptic ulcer and gastric cancer in Mexican population

BACKGROUND

Helicobacter pylori chronic infection is associated with chronic gastritis, peptic ulcer, and gastric cancer. Cytotoxin-associated gene A (cagA)-positive H. pylori strains increase the risk of gastric pathology. The carcinogenic potential of CagA is linked to its polymorphic EPIYA motif variants. The goals of this study were to investigate the frequency of cagA-positive Helicobacter pylori in Mexican patients with gastric pathologies and to assess the association of cagA EPIYA motif patterns with peptic ulcer and gastric cancer.

METHODS

A total of 499 patients were studied; of these, 402 had chronic gastritis, 77 had peptic ulcer, and 20 had gastric cancer. H. pylori DNA, cagA, and the EPIYA motifs were detected in total DNA from gastric biopsies by PCR. The type and number of EPIYA segments were determined by the electrophoretic patterns. To confirm the PCR results, 20 amplicons of the cagA 3' variable region were sequenced, and analyzed in silico, and the amino acid sequence was predicted with MEGA software, version 5. The odds ratio (OR) was calculated to determine the associations between the EPIYA motif type and gastric pathology and between the number of EPIYA-C segments and peptic ulcers and gastric cancer.

RESULTS

H. pylori DNA was found in 287 (57.5%) of the 499 patients, and 214 (74%) of these patients were cagA-positive. The frequency of cagA-positive H. pylori was 74.6% (164/220) in chronic gastritis patients, 73.6% (39/53) in peptic ulcer patients, and 78.6% (11/14) in gastric cancer patients. The EPIYA-ABC pattern was more frequently observed in chronic gastritis patients (79.3%, 130/164), while the EPIYA-ABCC sequence was more frequently observed in peptic ulcer (64.1%, 25/39) and gastric cancer patients (54.5%, 6/11). However, the risks of peptic ulcer (OR = 7.0, 95% CI = 3.3-15.1; p < 0.001) and gastric cancer (OR = 5.9, 95% CI = 1.5-22.1) were significantly increased in individuals who harbored the EPIYA-ABCC cagA gene pattern.

CONCLUSIONS

cagA-positive H. pylori is highly prevalent in southern Mexico, and all CagA variants were of the western type. The cagA alleles that code for EPIYA-ABCC motif patterns are associated with peptic ulcers and gastric cancer.

Systematic analysis of phosphotyrosine antibodies recognizing single phosphorylated EPIYA-motifs in CagA of Western-type Helicobacter pylori strains

The clinical outcome of Helicobacter pylori infections is determined by multiple host-pathogen interactions that may develop to chronic gastritis, and sometimes peptic ulcers or gastric cancer. Highly virulent strains encode a type IV secretion system (T4SS) that delivers the effector protein CagA into gastric epithelial cells. Translocated CagA undergoes tyrosine phosphorylation at EPIYA-sequence motifs, called A, B and C in Western-type strains, by members of the oncogenic Src and Abl host kinases. Phosphorylated EPIYA-motifs mediate interactions of CagA with host signaling factors--in particular various SH2-domain containing human proteins--thereby hijacking multiple downstream signaling cascades. Observations of tyrosine-phosphorylated CagA are mainly based on the use of commercial phosphotyrosine antibodies, which originally were selected to detect phosphotyrosines in mammalian proteins. Systematic studies of phosphorylated EPIYA-motif detection by the different antibodies would be very useful, but are not yet available. To address this issue, we synthesized phospho- and non-phosphopeptides representing each predominant Western CagA EPIYA-motif, and determined the recognition patterns of seven different phosphotyrosine antibodies in Western blots, and also performed infection studies with diverse representative Western H. pylori strains. Our results show that a total of 9-11 amino acids containing the phosphorylated EPIYA-motifs are necessary and sufficient for specific detection by these antibodies, but revealed great variability in sequence recognition. Three of the antibodies recognized phosphorylated EPIYA-motifs A, B and C similarly well; whereas preferential binding to phosphorylated motif A and motifs A and C was found with two and one antibodies, respectively, and the seventh anti-phosphotyrosine antibody did not recognize any phosphorylated EPIYA-motif. Controls showed that none of the antibodies recognized the corresponding non-phospho CagA peptides, and that all of them recognized phosphotyrosines in mammalian proteins. These data are valuable in judicious application of commercial anti-phosphotyrosine antibodies and in characterization of CagA phosphorylation during infection and disease development.

Five-year monitoring of considerable changes in tyrosine phosphorylation motifs of the Helicobacter pylori cagA gene in Iran

CagA is a major virulence factor of Helicobacter pylori involved in host cell modulation. The C-terminal part of CagA containing the EPIYA motifs is highly variable and is important for the biological activity of the protein. The aim of this study was consideration of the changes in cagA tyrosine phosphorylation motifs (TPMs) of H. pylori. A set of 302 H. pylori DNA samples from the Iranian population from 2006 to 2011 was selected for the proposed study. The cagA gene and its TPMs were assessed by using polymerase chain reaction (PCR) and specific primers. The prevalence of the cagA gene in our study ranged from 91.43% to 97.06% (with an average of 95.03%). Out of the cagA-positive samples, the prevalence of TPMs A and B increased from 12.5% and 23.44% to 71.2% and 63.63%, respectively. Also, the prevalence of samples infected with Western and East Asian types of H. pylori ranged from 64.06% to 5.73% for the Western type and 17.19% to 51.59% for the East Asian type. Overall, our results showed a high prevalence of the cagA gene. Also, it seems that cagA TPMs of H. pylori is undergoing a change from the Western type to the East Asian type in Iran.

Helicobacter pylori infection--a boon or a bane: lessons from studies in a low-prevalence population

Helicobacter pylori (H. pylori) infection is etiologically associated with gastric cancer and peptic ulcer diseases which are both important public health burdens which could be largely eliminated by H. pylori eradication. However, some investigators urge caution based on the hypothesis that eradication of H. pylori may result in an increase in the incidence of gastroesophageal reflux disease, esophageal adenocarcinoma, and childhood asthma. The ethnic Malays of northeastern Peninsular Malaysia have long had a low prevalence of H. pylori infection and, as expected, the incidence of gastric cancer and its precursor lesions is exceptionally low. The availability of a population with a low H. pylori prevalence and generally poor sanitation allows separation of H. pylori from the hygiene hypothesis and direct testing of whether absence of H. pylori is associated with untoward consequence. Contrary to predictions, in Malays, erosive esophagitis, Barrett's esophagus, distal esophageal cancers, and childhood asthma are all of low incidence. This suggests that H. pylori is not protective rather the presence of H. pylori infection is likely a surrogate for poor hygiene and not an important source of antigens involved in the hygiene hypothesis. Helicobacter pylori in Malays is related to transmission from H. pylori-infected non-Malay immigrants. The factors responsible for low H. pylori acquisition, transmission, and burden of H. pylori infection in Malays remain unclear and likely involves a combination of environmental, host (gene polymorphisms), and strain virulence factors. Based on evidence from this population, absence of H. pylori infection is more likely to be boon than a bane.

Determination of Helicobacter pylori CagA EPIYA types in Iranian isolates with different gastroduodenal disorders

Helicobacter pylori (H. pylori) cytotoxin-associated gene A protein (CagA) is the first bacterial oncoprotein identified in human gastric cancer. The carboxy terminus (C-terminus) of CagA may undergo polymorphisms to give different types of EPIYA motifs, which may exist in single or combination form within the infected host. Sequence variations in the 3' region of the cagA impose a functional impact to the translated CagA protein. In this study, we characterize the diversity of the H. pylori CagA EPIYA types, their associations with their hosts' clinical status, and the potential of using the whole 3' region of cagA as a genetic marker for the identification of Iranian isolates from different geographic locations. H. pylori was detected in 71 out of 177 examined Iranian patients with different gastroduodenal disorders. Genotyping of the cagA variable EPIYA motif was screened by polymerase chain reaction and gene sequencing was performed for all the detected cagA positive isolates. Out of 44 cagA-positive isolates, there were EPIYA motifs of ABC (30 isolates), ABCC (4 isolates), ABCCC (1 isolate), mixed types (6 isolates) and new types (3 isolates). We termed the newly identified EPIYA segment as EPIYA- A-B/C. Sequence analysis also showed the presence of uncommon EPIYA-like motifs (EPIYT and QPIYP) in some isolates. It is postulated that EPIYA type conversion through the presence of different repetitive sequences give rise to these new strains. We also identified 3 sequence motifs which may be applied as genetic markers for Iranian strains. Furthermore, EPIYA types ABCC and EPIYA- A-B/C showed association with duodenitis and gastric cancer, respectively. Further study with a larger number of strains is necessary to confirm the proposed associations and the identified sequence motifs as genetic markers. In conclusion, our study demonstrates the dominancy of Western type cagA gene and the diversity of the CagA C-terminal region in the tested Iranian strains.

Towards understanding the low prevalence of Helicobacter pylori in Malays: genetic variants among Helicobacter pylori-negative ethnic Malays in the north-eastern region of Peninsular Malaysia and Han Chinese and South Indians

OBJECTIVES

To identify gene polymorphisms that differ between Malays, Han Chinese and South Indians, and to identify candidate genes for the investigation of their role in protecting Malays from Helicobacter pylori (H. pylori) infection.

METHODS

Malay participants born and residing in Kelantan with a documented absence of H. pylori infection were studied. Venous blood was used for genotyping using the Affymetrix 50K Xba I kit. CEL files from 141 Han Chinese and 76 South Indians were analyzed to compare their allele frequency with that of the Malays using fixation index (FST ) calculation. The single nucleotide polymorphisms (SNPs) with the highest allele frequency (outliers) were then examined for their functional characteristics using F-SNP software and the Entrez Gene database.

RESULTS

In all, 37 Malays were enrolled in the study; of whom 7 were excluded for low genotyping call rates. The average FST estimated from the genome-wide data were 0.038 (Malays in Kelantan vs the South Indians), 0.015 (Malays in Kelantan vs Han Chinese) and 0.066 (Han Chinese vs South Indians), respectively. The outlier gene variants present in Malays with functional characteristics were C7orf10 (FST  0.29988), TSTD2 (FST  0.43278), SMG7 (FST  0.29877) and XPA (FST  0.43393 and 0.43644).

CONCLUSION

Genetic variants possibly related to protection against H. pylori infection in ethnic Malays from the north-eastern region of Peninsular Malaysia were identified for testing in subsequent trials among infected and uninfected Malays.

Is Helicobacter pylori good or bad?

Helicobacter pylori remains a controversial organism with regards to humans, with its epidemiology still being unclear nearly two decades after its discovery. The association between H. pylori infection and subsequent development of chronic active gastritis, peptic ulcer disease, gastric cell carcinoma, and B cell mucosa-associated lymphoid tissue (MALT) lymphoma has been well established. Current studies, however, suggest that fewer than 20 % of all infected patients will develop any consequences from their infection. Hence, should the infection be considered a disease not at all or, on the contrary, is the microorganism harmful in only some circumstances? This article attempts to weigh the currently available evidence supporting that H. pylori may be good and not always bad.

Molecular analysis of Helicobacter pylori virulent-associated genes in hepatobiliary patients

OBJECTIVES

The Helicobacter pylori virulence-associated genes in hepatobiliary patients, including vacA, iceA, babA2, cagA and cagE, have not been reported. The aim of this study was to investigate these genes and the association of those and the clinical outcomes in hepatobiliary diseases.

METHODS

Eighty H. pylori-PCR-positive cases were obtained from hepatobiliary patients, representing both cholangiocarcinoma (CCA) (n= 58) and cholelithiasis (n= 22). The diversity of virulence genes was examined by polymerase chain reaction and DNA sequencing. Phylogenetic analysis of cagA was determined using the maximum parsimony method.

RESULTS

The vacAs1a + c/m1, iceA1 and babA2 genes were the most predominant genotypes in both CCA and cholelithiasis patients. The cagA and cagE genes were found significantly more frequently in patients with CCA than those with cholelithiasis (P < 0.05). The cagA positive samples were the Western-type cagA and showed that almost all of the detected sequences in Thai hepatobiliary and Thai gastric cancer patients were classified in the same cluster but separated from the cluster of Japan and other countries.

CONCLUSIONS

The cagA and cagE genes may be associated in the pathogenesis of hepatobiliary diseases, especially of CCA. Besides the bacterial variation, other host factors may be involved in the pathogenesis of hepatobiliary cancer.

Role of Helicobacter pylori cagA EPIYA motif and vacA genotypes for the development of gastrointestinal diseases in Southeast Asian countries: a meta-analysis

Background

Infection with cagA-positive, cagA EPIYA motif ABD type, and vacA s1, m1, and i1 genotype strains of Helicobacter pylori is associated with an exacerbated inflammatory response and increased risk of gastroduodenal diseases. However, it is unclear whether the prevalence and virulence factor genotypes found in Southeast Asia are similar to those in Western countries. Here, we examined the cagA status and prevalence of cagA EPIYA motifs and vacA genotypes among H. pylori strains found in Southeast Asia and examined their association with gastroduodenal disease.

Methods

To determine the cagA status, cagA EPIYA motifs, and vacA genotypes of H. pylori, we conducted meta-analyses of 13 previous reports for 1,281 H. pylori strains detected from several Southeast Asian countries.

Results

The respective frequencies of cagA-positive and vacA s1, m1, and i1 genotypes among examined subjects were 93% (1,056/1,133), 98% (1,010/1,033), 58% (581/1,009), and 96% (248/259), respectively. Stratification showed significant variation in the frequencies of cagA status and vacA genotypes among countries and the individual races residing within each respective country. The frequency of the vacA m-region genotype in patients infected with East Asian-type strains differed significantly between the northern and southern areas of Vietnam (p < 0.001). Infection with vacA m1 type or cagA-positive strains was associated with an increased risk of peptic ulcer disease (odds ratio: 1.46, 95%CI: 1.01-2.12, p = 0.046 and 2.83, 1.50-5.34, p = 0.001, respectively) in the examined Southeast Asian populations.

Conclusions

Both Western- and East Asian-type strains of H. pylori are found in Southeast Asia and are predominantly cagA-positive and vacA s1 type. In Southeast Asia, patients infected with vacA m1 type or cagA-positive strains have an increased risk of peptic ulcer disease. Thus, testing for this genotype and the presence of cagA may have clinical usefulness.

The number of Helicobacter pylori CagA EPIYA C tyrosine phosphorylation motifs influences the pattern of gastritis and the development of gastric carcinoma

AIMS

To characterize the variation in virulence of Helicobacter pylori associated with CagA Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs, and to explore its relationship with the histopathological features of chronic gastritis and with the development of gastric carcinoma.

METHODS AND RESULTS

A total of 169 H. pylori-infected patients with chronic gastritis and gastric carcinoma were studied. The presence of cagA and the number and type of EPIYA motifs were determined by polymerase chain reaction. Infection with strains harbouring two or more CagA EPIYA C motifs was associated with the presence of surface epithelial damage, and with atrophic gastritis and gastric carcinoma. The magnitude of risk for atrophic gastritis and gastric carcinoma increased with increasing number of EPIYA C motifs: strains with one EPIYA C motif conferred a risk (odds ratio [OR]) of 7.3 [95% confidence interval (CI) 2.1-25] for atrophic gastritis, whereas strains with two or more EPIYA C motifs conferred a risk (OR) of 12 (95% CI 2.5-58); strains with one EPIYA C motif conferred a risk (OR) of 17 (95% CI 5.4-55) for gastric carcinoma, whereas strains with two or more EPIYA C motifs conferred a risk (OR) of 51 (95% CI 13-198).

CONCLUSIONS

Characterization of the number of H. pylori EPIYA C motifs is important in better defining gastric carcinoma risk.

Sociocultural and dietary practices among Malay subjects in the north-eastern region of Peninsular Malaysia: a region of low prevalence of Helicobacter pylori infection

BACKGROUND AND AIM

The prevalence of Helicobacter pylori infection is exceptionally low among the Malays in the north-eastern region of Peninsular Malaysia. The reasons are unknown. Our aim was to compare environmental factors that differed in relation to H. pylori prevalence among Malays born and residing in Kelantan.

METHODS

A case-control study was conducted among Malays in Kelantan who underwent upper endoscopy between 2000 and 2008. Helicobacter pylori status was determined by gastric histology. Sociocultural and dietary factors were assessed using a validated investigator-directed questionnaire administered after 2008, and the data were analyzed using logistic regression analysis.

RESULTS

The study group consisted of 161 subjects (79 H. pylori positive and 82 controls). Univariable analysis identified five poor sanitary practices associated with an increased prevalence of H. pylori infection: use of well water, use of pit latrine, less frequent boiling of drinking water, and infrequent hand wash practice after toilet use and before meals. Multivariable logistic regression analysis identified three variables inversely associated with H. pylori infection: frequent consumption of tea (OR: 0.023, 95% CI: 0.01-0.07), frequent use of "budu" or local anchovy sauce (OR: 0.09, 95% CI: 0.1-0.7), and frequent use of "pegaga" or centenella asiatica (OR: 0.25, 95% CI: 0.1-0.65).

CONCLUSIONS

Under the assumption that sanitary, sociocultural, and dietary habits have not changed over the years, we can conclude that an increased risk of H. pylori was associated with unsanitary practices whereas protection was associated with consumption of tea and locally produced foods, "pegaga" and "budu." These dietary factors are candidates for future study on the effects on H. pylori transmission.

Potentiation of Helicobacter pylori CagA protein virulence through homodimerization

Chronic infection with Helicobacter pylori cagA-positive strains is associated with atrophic gastritis, peptic ulceration, and gastric carcinoma. The cagA gene product, CagA, is delivered into gastric epithelial cells via type IV secretion, where it undergoes tyrosine phosphorylation at the EPIYA motifs. Tyrosine-phosphorylated CagA binds and aberrantly activates the oncogenic tyrosine phosphatase SHP2, which mediates induction of elongated cell morphology (hummingbird phenotype) that reflects CagA virulence. CagA also binds and inhibits the polarity-regulating kinase partitioning-defective 1 (PAR1)/microtubule affinity-regulating kinase (MARK) via the CagA multimerization (CM) sequence independently of tyrosine phosphorylation. Because PAR1 exists as a homodimer, two CagA proteins appear to be passively dimerized through complex formation with a PAR1 dimer in cells. Interestingly, a CagA mutant that lacks the CM sequence displays a reduced SHP2 binding activity and exhibits an attenuated ability to induce the hummingbird phenotype, indicating that the CagA-PAR1 interaction also influences the morphological transformation. Here we investigated the role of CagA dimerization in induction of the hummingbird phenotype with the use of a chemical dimerizer, coumermycin. We found that CagA dimerization markedly stabilizes the CagA-SHP2 complex and thereby potentiates SHP2 deregulation, causing an increase in the number of hummingbird cells. Protrusions of hummingbird cells induced by chemical dimerization of CagA are further elongated by simultaneous inhibition of PAR1. This study revealed a role of the CM sequence in amplifying the magnitude of SHP2 deregulation by CagA, which, in conjunction with the CM sequence-mediated inhibition of PAR1, evokes morphological transformation that reflects in vivo CagA virulence.

Anthropological and clinical implications for the structural diversity of the Helicobacter pylori CagA oncoprotein

Helicobacter pylori CagA is the first bacterial oncoprotein to be identified in relation to human cancer. CagA is delivered into gastric epithelial cells through a bacterial type IV secretion system and localizes to the plasma membrane, where it undergoes tyrosine phosphorylation by host cell kinases. Membrane-localized CagA then mimics mammalian scaffold proteins and perturbs a number of host signaling pathways in both tyrosine phosphorylation-dependent and -independent manners, thereby promoting transformation of gastric epithelial cells. Helicobacter pylori CagA is noted for structural diversity in its C-terminal region, with which CagA interacts with numerous host cell proteins. This CagA polymorphism is primarily due to differential combination and alignment of the four distinct EPIYA segments and the two different CagA-multimerization sequences in making the C-terminal region. The structural diversity substantially influences the pathophysiological action of CagA. This review focuses on the molecular basis for the structural polymorphism that determines the degrees of virulence and oncogenic potential of individual CagA. The pylogeographic distribution of differential CagA isoforms is also discussed in the context of human migration history, which may underlie large geographical variations in the incidence of gastric cancer in different parts of the world.

Diagnosis of Helicobacter pylori infection

If we had to give a general view of the articles published in the year 2010, we should conclude that the evidence in the year 2010 suggests that, also in Helicobacter pylori diagnosis, "the devil is in the details". In this sense, different studies suggested that skipping citric acid pretreatment or local validation or reducing the (13) C-urea dose markedly decreases the accuracy of the urea breath test. The studies also implied that, even between monoclonal stool tests, there are large differences between the marketed tests. Finally, even histology does not work adequately in patients with gastric cancer or extensive areas of intestinal metaplasia. In these cases, specific gastric sites should be biopsied to improve the reliability of histology.

The versatility of Helicobacter pylori CagA effector protein functions: The master key hypothesis

Several bacterial pathogens inject virulence proteins into host target cells that are substrates of eukaryotic tyrosine kinases. One of the key examples is the Helicobacter pylori CagA effector protein which is translocated by a type-IV secretion system. Injected CagA becomes tyrosine-phosphorylated on EPIYA sequence motifs by Src and Abl family kinases. CagA then binds to and activates/inactivates multiple signaling proteins in a phosphorylation-dependent and phosphorylation-independent manner. A recent proteomic screen systematically identified eukaryotic binding partners of the EPIYA phosphorylation sites of CagA and similar sites in other bacterial effectors by high-resolution mass spectrometry. Individual phosphorylation sites recruited a surprisingly high number of interaction partners suggesting that each phosphorylation site can interfere with many downstream pathways. We now count 20 reported cellular binding partners of CagA, which represents the highest quantitiy among all yet known virulence-associated effector proteins in the microbial world. This complexity generates a highly remarkable and puzzling scenario. In addition, the first crystal structure of CagA provided us with new information on the function of this important virulence determinant. Here we review the recent advances in characterizing the multiple binding signaling activities of CagA. Injected CagA can act as a 'master key' that evolved the ability to highjack multiple host cell signalling cascades, which include the induction of membrane dynamics, actin-cytoskeletal rearrangements and the disruption of cell-to-cell junctions as well as proliferative, pro-inflammatory and anti-apoptotic nuclear responses. The discovery that different pathogens use this common strategy to subvert host cell functions suggests that more examples will emerge soon.

Epidemiology of Helicobacter pylori infection and gastric cancer in Asia

In Asia, the prevalence of Helicobacter pylori (H. pylori) infection varies markedly in different countries. Higher prevalence rates are found in developing Asian countries while lower rates have been reported in more industrialized and developed countries. Within a country, the seroprevalence rates may vary between distinct geographic regions. H. pylori infection is an important etiological factor for the occurrence of non-cardia gastric adenocarcinoma. The incidence rate of gastric adenocarcinoma in Asia tends to mirror the seroprevalence rate of H. pylori infection; however, there are populations with high seroprevalence rates of H. pylori infection that paradoxically have low incidence rates of gastric adenocarcinoma. These diverse clinical outcomes are related to bacterial virulence factors, concomitant environmental factors, host susceptibility and immune response. This review summarizes the current epidemiology of H. pylori infection in Asia and analyzes these data in the context of gastric cancer epidemiology.

Different cagA and vacA Polymorphisms are Found in the Chinese versus the Malay and Indian Populations: An Analysis of Helicobacter Pylori Virulence Genes in Singapore

Aim:

Helicobacter pylori causes peptic ulcer disease and gastric cancer. Western studies suggest that polymorphisms in the virulence factors cagA and vacA may determine the ability of bacteria to cause gastroduodenal diseases. Differences in the cagA EPIYA motifs and polymorphisms of the signal (s), middle (m) and intermediate (i) regions of vacA are thought to be important. The aim of this study was to compare the polymorphisms of cagA and vacA of H. pylori isolated from the Chinese, Malay and Indian populations living in Singapore.

Method:

A total of 104 H. pylori isolates obtained from patients with dyspeptic symptoms were analysed. Of the 104 patients, 80 were Chinese, 9 Malays and 15 Indians. DNA was extracted from the isolates and the vacA allelic types and cagA EPIYA motifs were determined by polymerase chain reaction (PCR) and sequencing, respectively.

Results:

Differences in the vacA and cagA polymorphisms were found between the Chinese, Malays and Indians. Significantly more non-Chinese patients carried vacA s1/m1 strains versus Chinese patients ( p < 0.05). All 9 Malay patients, 11/15 (73.3%) Indians and 31/80 (38.8%) Chinese patients carried H. pylori strains with the vacA s1/m1/i1. Significantly more Chinese patients carried isolates with East Asian cagA EPIYA motifs versus non-Chinese patients ( p < 0.05). 79/80 (98.8%) of the Chinese isolates, 2/15 (13%) of Indian isolates, and 5/9(55.6%) of Malay isolates possessed CagA with the East Asian ABD type motif.

Conclusion:

Results from the current study demonstrated marked differences in the polymorphisms of vacA and CagA EPIYA motifs in strains isolated from Chinese versus non-Chinese patients. Epidemiologically, the Chinese are at the highest risk of developing gastric cancer. Work is ongoing to determine if differences found in the CagA EPIYA motifs of isolates from the Chinese patients can contribute to a subject's risk of developing gastric cancer.

The cag PAI is intact and functional but HP0521 varies significantly in Helicobacter pylori isolates from Malaysia and Singapore

Helicobacter pylori-related disease is at least partially attributable to the genotype of the infecting strain, particularly the presence of specific virulence factors. We investigated the prevalence of a novel combination of H. pylori virulence factors, including the cag pathogenicity island (PAI), and their association with severe disease in isolates from the three major ethnicities in Malaysia and Singapore, and evaluated whether the cag PAI was intact and functional in vitro. Polymerase chain reaction (PCR) was used to detect dupA, cagA, cagE, cagT, cagL and babA, and to type vacA, the EPIYA motifs, HP0521 alleles and oipA ON status in 159 H. pylori clinical isolates. Twenty-two strains were investigated for IL-8 induction and CagA translocation in vitro. The prevalence of cagA, cagE, cagL, cagT, babA, oipA ON and vacA s1 and i1 was >85%, irrespective of the disease state or ethnicity. The prevalence of dupA and the predominant HP0521 allele and EPIYA motif varied significantly with ethnicity (p < 0.05). A high prevalence of an intact cag PAI was found in all ethnic groups; however, no association was observed between any virulence factor and disease state. The novel association between the HP0521 alleles, EPIYA motifs and host ethnicity indicates that further studies to determine the function of this gene are important.

Helicobacter pylori virulence factors as tools to study human migrations

Helicobacter pylori is one of the most common infections worldwide. In most individuals it consists in a lifelong host-pathogen relationship without consequences, but in some subjects it is associated with peptic ulcer disease and gastric cancer. Polymorphism in genes that code bacterial virulence factors, cagA and vacA, are independently associated with the infection severe outcomes and are geographically diverse. In the last decade, accumulated knowledge allowed to characterize typical H. pylori strain patterns for all the major human populations; patterns that can be used to study the origin of specific human groups. Thus, the presence or absence of cagA, cagA EPIYA genotypes, and vacA subtypes can be used as tools to study not only the geographic origin of specific human populations, but also to identify markers of historical contact between different ethnicities. We report here a study including a set of native Amazon Amerindians that had supposedly been some, but little, contact with European Brazilian colonizer and/or African slaves. They harbor H. pylori strains in a mixed pattern with Asian and Iberian Peninsula characteristics. It is possible that this finding represents H. pylori recombination upon short contact between human groups. Alternatively, it could be due to a founder effect from a small cluster of Asian origin native Americans.

Diversity in the cag pathogenicity island of Helicobacter pylori isolates in populations from North and South India

The cag pathogenicity island (cagPAI) has been reported to be the major virulence determinant in Helicobacter pylori-related diseases. In the present study, the diversity of the cagA gene and the integrity of the cagPAI in 158 H. pylori strains from Varanasi (North India) and Hyderabad (South India) were studied by amplifying the cagA gene (approximately 3.5 kb), followed by PCR-RFLP analysis. The results revealed significant differences in the cagA gene and the integrity of the cagPAI between North and South Indian isolates. Of 158 isolates, 40 (34.8 %) from Varanasi and 20 (46.5 %) from Hyderabad were found to carry an intact cagPAI. A partially deleted cagPAI was present in 75 (65.2 %) isolates from Varanasi and 23 (53.5 %) from Hyderabad. None of the isolates showed complete deletion of the cagPAI. Differences in the cagA 5' and 3' regions were also noted, and 11 isolates (8 from Varanasi and 3 from Hyderabad) that were cagA negative with primers for the 5' region turned out to be cagA positive with primers for the 3' variable region. It is tentatively concluded that the 3' variable region may be a better marker for cagA typing. The results also showed that the majority of the isolates harboured the Western-type EPIYA motif. PCR-RFLP analysis of the cagA gene showed 29 distinguishable digestion patterns, and cluster analysis of RFLP types from a random selection of 32 isolates placed all of the isolates into 5 groups. These results demonstrate that significant differences in the cagPAI occur among isolates from North and South India, and that RFLP of cagA could be employed for elucidating genetic variations among various isolates of H. pylori.

Evaluation of the anti-East Asian CagA-specific antibody for CagA phenotyping

The determination of the cagA genotype is generally based on sequencing the variable 3' region of the cagA gene. In a previous study, we successfully generated an anti-East Asian CagA-specific antibody (anti-EAS Ab) immunoreactive only with the East Asian CagA and not with the Western CagA. In a small number of Japanese patients, anti-EAS Ab appeared to be a useful tool for phenotyping CagA immunohistochemically. The present study was conducted to validate the anti-EAS Ab immunohistochemistry method in a larger number of patients from Vietnam and Thailand. A total of 385 Vietnamese and Thais were recruited. Helicobacter pylori status was determined by a combination of three methods, including culture, histology, and immunohistochemistry with anti-H. pylori antibody. The sensitivity, specificity, and accuracy of the anti-EAS Ab immunohistochemistry method for the diagnosis of CagA phenotype were calculated based on the results of the cagA sequencing as the gold standard. The sensitivity, specificity, and accuracy of our immunohistochemistry method were 96.7%, 97.9%, and 97.1%, respectively. Moreover, anti-EAS Ab was not cross-reactive with noninfected gastric mucosa. In conclusion, immunohistochemistry with anti-EAS Ab appears to be a good method for determination of CagA phenotype.

Population structure of Helicobacter pylori among ethnic groups in Malaysia: recent acquisition of the bacterium by the Malay population

BACKGROUND

Helicobacter pylori is a major gastric bacterial pathogen. This pathogen has been shown to follow the routes of human migration by their geographical origin and currently the global H. pylori population has been divided into six ancestral populations, three from Africa, two from Asia and one from Europe. Malaysia is made up of three major ethnic populations, Malay, Chinese and Indian, providing a good population for studying recent H. pylori migration and admixture.

RESULTS

Seventy eight H. pylori isolates, including 27 Chinese, 35 Indian and 16 Malay isolates from Malaysia were analysed by multilocus sequence typing (MLST) of seven housekeeping genes and compared with the global MLST data. STRUCTURE analysis assigned the isolates to previously identified H. pylori ancestral populations, hpEastAsia, hpAsia2 and hpEurope, and revealed a new subpopulation, hspIndia, within hpAsia2. Statistical analysis allowed us to identify population segregation sites that divide the H. pylori populations and the subpopulations. The majority of Malay isolates were found to be grouped together with Indian isolates.

CONCLUSION

The majority of the Malay and Indian H. pylori isolates share the same origin while the Malaysian Chinese H. pylori is distinctive. The Malay population, known to have a low infection rate of H. pylori, was likely to be initially H. pylori free and gained the pathogen only recently from cross infection from other populations.