CagA C-terminal variations in Helicobacter pylori strains from Colombian patients with gastric precancerous lesions

The C-terminus of the Helicobacter pylori CagA protein is polymorphic, bearing different EPIYA sequences (EPIYA-A, B, C or D), and one or more CagA multimerization (CM) motifs. The number of EPIYA-C motifs is associated with precancerous lesions and gastric cancer (GC). The relationship between EPIYA, CM motifs and gastric lesions was examined in H. pylori-infected Colombian patients from areas of high and low risk for GC. Genomic DNA was extracted from H. pylori strains cultured from gastric biopsies from 80 adults with dyspeptic symptoms. Sixty-seven (83.8%) of 80 strains were cagA positive. The 3’ region of cagA was sequenced, and EPIYA and CM motifs were identified. CagA proteins contained one (64.2%), two (34.3%) or three EPIYA-C motifs (1.5%), all with Western type CagA-specific sequences. Strains with one EPIYA-C motif were associated with less severe gastric lesions (non-atrophic and multifocal atrophic gastritis), whereas strains with multiple EPIYA-C motifs were associated with more severe lesions (intestinal metaplasia and dysplasia) (p <0.001). In 54 strains, the CM motifs were identical to those common in Western strains. Thirteen strains from the low-risk area contained two different CM motifs: one of Western type located within the EPIYA-C segment and another following the EPIYA-C segment and resembling the CM motif found in East Asian strains. These strains induced significantly shorter projections in AGS cells and an attenuated reduction in levels of CagA upon immunodepletion of SHP-2 than strains possessing Western/Western motifs. This novel finding may partially explain the difference in GC incidence in these populations.     

Analysis of Clarithromycin Resistance and CagA Status in Helicobacter pylori by Use of Feces from Children in Thailand

The clarithromycin resistance and CagA status of Helicobacter pylori in Thai children were investigated using fecal samples. Of the 284 samples, H. pylori was detected in 120 samples, and the clarithromycin resistance rate was 29.2%. The cagA gene was detected in 59 samples, and only 6.8% of these samples contained the East Asian CagA type.Helicobacter pylori is a pathogenic bacterium that colonizes the human stomach. The prevalence of antibiotic-resistant H. pylori, especially clarithromycin-resistant H. pylori, has been increasing worldwide and makes it difficult to successfully eradicate H. pylori. Clarithromycin resistance in H. pylori has been shown to be due to mutations at positions 2142 and 2143 of the 23S rRNA gene (7, 9).Although H. pylori is closely associated with gastric cancer, the rate of mortality due to gastric cancer is relatively low in Thailand, even though the rate of H. pylori infection in Thailand has been reported to be over 80% (6, 8). A difference in pathogenicity between H. pylori strains may explain the lack of the expected correlation between the rate of mortality due to gastric cancer and the rate of H. pylori infection. The CagA protein, which is one of the most important pathogenicity factors of H. pylori, has been classified into two types: the East Asian CagA type, found in H. pylori isolates from Japan, South Korea, and China, and the Western CagA type, found in H. pylori isolates from Europe, North America, and Australia. Each CagA type has tyrosine phosphorylation segments characterized by a Glu-Pro-Ile-Tyr-Ala (EPIYA) motif in the C-terminal region (3). However, the Western CagA type contains the EPIYA-A and EPIYA-B segments, followed by a variable number of EPIYA-C segments, while the East Asian CagA type contains the EPIYA-A, EPIYA-B, and EPIYA-D segments. Furthermore, the East Asian CagA type has been reported to induce more-severe cellular changes than the Western CagA type (2).Recently, we identified a noninvasive method for detecting clarithromycin-resistant H. pylori isolates from feces with high sensitivity and specificity (5). In this study, we used this previously developed method to investigate the clarithromycin resistance and CagA status of H. pylori in feces of Thai children.Fecal samples were obtained from 284 children (116 males/116 females; mean age, 6.60 years [range, 1 to 12 years]) from three schools in Chiang Mai in August 2006. The ages and genders of 52 children of ethnic minorities could not be obtained. The study protocol and the informed-consent document were reviewed and approved by Research Ethics Committee, Faculty of Medicine, Chiang Mai University.DNA was extracted from the feces, and the 23S rRNA gene of H. pylori was amplified as previously described (5). Samples were considered to contain clarithromycin-resistant H. pylori if mutations at positions 2142 and 2143 of the 23S rRNA gene were detected.For the amplification of the cagA gene, we designed new primers targeting the region containing the EPIYA-A and EPIYA-B segments by comparing 81 of the cagA genes registered in the DNA Data Bank of Japan (data not shown). Amplification was performed using primer pairs comprising primers 2553F (5′-AACCCTAGTCGGTAATGGGTTRTCT-3′) and 3222R (5′-ATTGCTATTAATGCGTGTGTGGC-3′) for the first-round PCR and 2612F (5′-CGGACATCAGGAAAGAATTGAA-3′), 2609F (5′-TTTCGGATATCAAGAAGAATTGAA-3′), and 2998R (5′-TTGAAAGCCCTACTTTACTGAGATCA-3′) for the second-round PCR.Samples were designated cagA positive when a PCR product of 180 bp was detected after the third-round PCR, which was performed using Go Taq Green master mix (Promega, Madison, WI) and the 2609F, 2612F, 2779R (5′-CACTCACCTTTTTTAGCAACTTGAG-3′), and 2780R (5′-GCTTTTACCTTTTTAGCAACTTGAG-3′) primers. The cagA-typing PCR was performed using an East Asian CagA-specific primer pair (East-Asian-F [5′-AAAGGAGTGGGCGGTTTCA-3′] and East-Asian-R [5′-CCTGCTTGATTTGCCTCATCA-3′]) and a Western CagA-specific primer pair (Western-F [5′-GGCATGATAAAGTTGATGATCTCAGT-3′] and Western-R [5′-AAAGGTCCGCCGAGATCAT-3′]), which targeted the EPIYA-D and EPIYA-C segments, respectively. Each typing PCR was performed using 1.5 μl of the second PCR product. For each PCR amplification, a PCR mixture that contained ultrapure water as the template was included to rule out false-positive results.Of the 284 fecal samples obtained from Thai children, H. pylori was detected in 120 (42.3%). Of the 120 H. pylori-positive samples, clarithromycin-resistant H. pylori was detected in 35 (29.2%) samples, and both clarithromycin-susceptible and -resistant H. pylori isolates were detected simultaneously in 5 samples. The incidence of clarithromycin-resistant H. pylori in this study was slightly higher than the rate reported for Thai adults in other studies (23.2%) (4). Because there have been few studies that focused on the rate of clarithromycin-resistant H. pylori in Thai children, the results of this study will be useful for estimating the rate of clarithromycin-resistant H. pylori infection in adults in Thailand in the future.The cagA gene was present in 59 (49.2%) of the H. pylori-positive samples. Of these samples, 20 (33.9%) samples contained the Western CagA type (containing the EPIYA-C segments) and 4 (6.8%) contained the East Asian CagA type (containing the EPIYA-D segments). The remaining 35 samples, which lacked any EPIYA-C or EPIYA-D motifs, were considered to contain the Western CagA type (1). To confirm the absence of the EPIYA-C and EPIYA-D segments in these 35 samples, DNA sequencing was performed on 14 cagA genes by using the second PCR product, and none of the cagA genes analyzed had an EPIYA-C or EPIYA-D segment. In summary, H. pylori isolates containing the East Asian CagA type (6.8%) were significantly less prevalent than H. pylori isolates containing the Western CagA type (93.2%). Most of the H. pylori strains isolated in Asian countries with high incidences of deaths from gastric cancer, such as Japan and China, have been reported to contain the East Asian CagA type (10). Since differences in the prevalences of the East Asian CagA type in Asian countries have been suggested to be one of the reasons underlying the differential mortality rates associated with gastric cancer (2), further investigation is needed to confirm this possibility.In this study, we detected a high proportion (59.3%) of CagA that contained neither the EPIYA-C nor the EPIYA-D segment. The low incidence of Western CagA containing the EPIYA-C segment in Thailand may be one of the reasons for the low mortality rate associated with gastric cancer in Thailand.In conclusion, we show that the prevalence of the CagA types of H. pylori in Thai children differs from that reported for other Asian countries. Furthermore, our study demonstrates the usefulness of this approach for detecting and typing CagA in H. pylori by using feces. This method may prove useful in further investigations of the prevalences of the CagA types in H. pylori isolates from infected individuals.     

Host Cell Responses to Genotypically Similar Helicobacter pylori Isolates from United States and Japan

Associations of Helicobacter pylori genotypes with disease differ between Western countries and Asia. Therefore, we directly compared histopathological and in vitro responses to clinical isolates with similar genotypes. Sixty-three cagA⁺ vacAs1/m1 H. pylori isolates (United States, n = 24; Japan, n = 39) and eight cagA-negative vacAs2/m2 strains were incubated with AGS cells, and supernatants were assayed for interleukin-8 (IL-8) and for DNA fragmentation. CagA tyrosine phosphorylation in AGS cells and the sequence of the putative HP0638 (oipA) signal sequence region were determined for 22 representative strains. HP0638 and/or cag island mutant strains were created and examined in IL-8 and CagA tyrosine phosphorylation assays. Levels of IL-8 induction and DNA fragmentation were similar in the U.S. and Japanese cagA⁺ vacAs1/m1 isolates. All 10 of the isolates with the highest IL-8 induction and 8 of the 10 isolates with the lowest IL-8 induction had an in-frame oipA open reading frame, and all 10 of the isolates with the highest IL-8 induction and 7 of the 10 isolates with the lowest IL-8 induction induced CagA tyrosine phosphorylation in AGS cells. Eight isolates from gastric ulcer patients induced significantly more apoptosis in vitro, and more severe gastritis and atrophy in vivo, than other Japanese isolates. Disruption of HP0638 did not affect IL-8 induction or CagA tyrosine phosphorylation. Thus, H. pylori cagA⁺ vacAs1/m1 isolates from the United States and Japan induce similar IL-8 and apoptosis levels. Inactivation of HP0638 does not alter epithelial responses mediated by the cag island in vitro. Assessment of apoptosis in vitro identified a group of H. pylori isolates that induce more severe gastric inflammation and atrophy.     

Diversity of Helicobacter pylori vacA and cagA Genes and Relationship to VacA and CagA Protein Expression, Cytotoxin Production, and Associated Diseases

The vacuolating cytotoxin and the cytotoxin-associated protein, encoded by vacA and cagA, respectively, are important virulence determinants of Helicobacter pylori. Sixty-five H. pylori strains were isolated from dyspeptic patients (19 with peptic ulcer disease, 43 with chronic gastritis, and 3 with gastric cancer) and studied for differences in the vacA and cagA genes and their relationship to VacA and CagA expression, cytotoxin activity, and the clinical outcome of infection. By PCR, fifty-four (83.1%) of 65 strains had the vacA signal sequence genotype s1 and only 10 (15.4%) had the type s2. After primer modification, the vacA middle-region types m1 and m2 were detected in 24 (36.9%) and 41 (63.1%) strains, respectively. The combinations s1-m2 (31 [47.7%]) and s1-m1 (23 [35.4%]) occurred more frequently than s2-m2 (10 [15.4%]) (P = 0.01). No strain with the combination s2-m1 was found. All 19 patients with peptic ulcers harbored type s1 strains, in contrast to 32 (74.4%) of 43 patients with gastritis (P = 0.02). The vacA genotype s1 was associated with the presence of cagA (P < 0.0001), VacA expression (P < 0.0001), and cytotoxin activity (P = 0.003). The cagA gene was detectable in 48 (73.8%) of 65 isolates and present in 16 (84.2%) of 19 ulcer patients and 29 (67.4%) of 43 patients with gastritis (P = 0.17). The vacA genotypes of German H. pylori isolates are identical to those previously reported. H. pylori strains of vacA type s1 are associated with the occurrence of peptic ulceration and the presence of cagA, cytotoxin activity, and VacA expression.     

Analysis of the 3′-variable region of the cagA gene from Helicobacter pylori strains infecting patients at New York City hospitals

Helicobacter pylori infects the gastric mucosa in humans and is a causative agent for peptic ulcer disease (PUD) and gastric cancer (GC). CagA is produced by H. pylori and is associated with more severe outcomes. cagA genes vary at the 3′-region with respect to phosphorylation motifs (EPIYA-A, -B, -C, or -D) and CagA multimerization motifs (CM). This variability may be associated with the clinical outcomes. We examined the variable region of cagA genes expressed in H. pylori-infected patients treated at three NYC Hospitals. DNA was isolated from gastric biopsies of patients undergoing upper endoscopy. Most H. pylori-infected patients were Black or Hispanic. The cagA 3′-region of CagA-positive samples was amplified by PCR, purified and sequenced. The patterns of EPIYA and CM motifs were examined and related to clinical outcomes. We obtained 42 CagA sequences from our sample collection. The EPIYA phosphorylation motif pattern was ABC in 81.0% of our samples. Western (W) and Eastern (E) CM motifs have also been defined. CagA proteins lacking an Eastern CM motif and possessing one or two Western CM motifs were observed more frequently in patients with PUD and GC when compared with non-ulcer gastritis (50.0% vs 11.8%, respectively), suggesting that these CM motif patterns are more virulent than those containing at least one Eastern CM motif. We conclude that In H. pylori-infected patients treated at NYC Hospitals, CM motif patterns in the CagA 30-variable region may be more significant than EPIYA motif patterns with respect to clinical outcomes.     

Profile of Helicobacter pylori cagA & vacA genotypes and its association with the spectrum of gastroduodenal disease

PurposeGlobally, H. pylori virulence factors cagA and vacA genotypes and its variation is leading to the austere form of the gastroduodenal disease. Our objectives were to detect H. pylori in dyspeptic patients from biopsy samples with the validation of the various existing diagnostic tools and to screen the cagA, vacA genotypes profile from biopsy specimens and how it impacts in progression of gastroduodenal disease in southern India.Methods374 patients who attended endoscopy unit at Kasturba Hospital, Manipal with their consent obtained their biopsies. H. pylori were detected by HPE, Culture, RUT and PCR and its virulence gene were patterned with PCR.ResultsThe positive rate of H. pylori by HPE, RUT, Culture and PCR were 51.33%, 47.1%, 32.4% and 50.3% respectively and comparison by Bayesian LCMs analysis showed PCR is superior among them. The frequency of H. pylori virulence gene viz cagPAI (cagA) were 80.9%, and vacA alleles-s1m1 (42%), s1m2 (33%) and s2m2 (25%) genotypes by PCR respectively. Four combinations of cagA/vacA genotypes were noted, majority of strains harboured cagA⁺/vacA s1m1 genotypes (42.6%), interestingly this hyper-virulent strain more frequently seen in severe gastroduodenal disease whereas cagPAI negative strains as well as cagA⁻/vacA s2m2 combinations (19.1%) are seen most commonly in functional dyspepsia cases and depicted significant association by Chi-square test.ConclusionsThis study validates and compares the existing diagnostic methods for detecting H. pylori in biopsies. Also, it reveals some pattern of virulence gene combination will play a vital role in disease progression.     

Vacuolating Cytotoxin Genotypes Are Strong Markers of Gastric Cancer and Duodenal Ulcer-Associated Helicobacter pylori Strains: a Matched Case-Control Study

The Helicobacter pylori virulence gene, cagA, and active forms of the vacuolating cytotoxin gene, vacA, are major determinants of pathogenesis. However, previous studies linking these factors to disease risk have often included patients using aspirin/nonsteroidal anti-inflammatory agents (NSAIDs) or acid-suppressing drugs, both of which may confound results. Also, particularly for gastric cancer (GC), controls have often been of quite different ages. Here, we performed a careful study in a “clean” Belgian population with gastric cancer cases age and sex matched to 4 controls and with a parallel duodenal ulcer (DU) group. As in other populations, there was a close association between the presence of cagA and the vacA s1 genotype. For GC, associations were found for vacA s1-positive (P = 0.01, odds ratio [OR], 9.37; 95% confidence interval [CI], 1.16 to 201.89), i1-positive (P = 0.003; OR, 12.08; 95% CI, 1.50 to 259.64), and cagA-positive status (P < 0.05; OR, infinity; 95% CI, 0.76 to infinity). For DU, associations were found with vacA s1 (P = 0.002; OR, 6.04; 95% CI, 1.52 to 27.87) and i1 (P = 0.004; OR, 4.35; 95% CI, 1.36 to 14.78) status but not with cagA status. Neither condition showed independent associations with the vacA m1 allele or with more biologically active forms of cagA with longer 3′ variable regions. In this Belgian population, the best markers of gastric cancer- and duodenal ulcer-associated strains are the vacA s1 and i1 genotypes. This fits with experimental data showing that the s and i regions are the key determinants of vacuolating cytotoxin activity.     

Characterization of the cagA-gene in Helicobacter pylori in Mongolia and detection of two EPIYA-A enriched CagA types

Helicobacter pylori infection is strongly associated with gastritis, gastroduodenal ulcer disease and gastric carcinoma. The virulence of H. pylori strains increases with the presence of the pathogenicity island PAI, which encodes a Type 4 Secretion System and the oncoprotein CagA. Two major CagA types can be distinguished by differences in the repetitive EPIYA region in the C-terminal sequence; the more virulent East Asian CagA type with EPIYA-A, -B, and -D motifs and the Western CagA type with EPIYA-A, -B, and C motifs, the virulence of which is associated with the multitude of EPIYA-C motifs.In this study, the cagA gene was characterized in H. pylori strains isolated from Mongolians suffering from gastritis (80%) or ulcer (20%). The EPIYA region of 53 isolates was determined by PCR-amplification of overlapping cagA regions and subsequent Sanger sequencing. Only one H. pylori isolate carried the East Asian type (ABD) and 52 isolates the Western type of CagA, thereof 30 the EPIYA type ABC, 19 the ABCC type and one each of type ABCCCC, AAABC and AAAAB. An amino acid exchange from EPIYA-B to EPIYT-B was predominantly found in CagA proteins in strains with < 2 EPIYA-C copies (n = 25/32; p = 0.015) including the two EPIYA-A enriched CagA proteins, which have not been described to date. Due to the amino acid triplet preceding the EPIYA motif and strength of predicted phosphorylation, the multiple EPIYA-A motifs A2, A3 and A4 were shown to cluster with EPIYA-B and EPIYT-B with the unique feature of amino acid E in position ? 4 to Y of EPIYA. It has been described that tyrosine-phosphorylated EPIYA-A and -B motifs counteract the EPIYA-C-driven signaling towards host cell transformation and malignancy. Thus, Mongolian H. pylori strains carrying CagA proteins not only with a few EPIYA-C segments but also with multiplied EPIYA-A segments are probably less virulent; a thesis that needs further investigation at the protein level.     

A Novel Method for Genotyping the Helicobacter pylori vacA Intermediate Region Directly in Gastric Biopsy Specimens

The present report describes a novel method for genotyping the virulence-associated vacA intermediate (i) region of Helicobacter pylori in archive material. vacA i-region genotypes as determined by the novel method were completely concordant with those of sequence analysis and with those of functional vacuolation activity. The method was further validated directly in gastric biopsy specimens of 386 H. pylori-positive cases, and effective characterization of the vacA i region was obtained in 191 of 192 (99.5%) frozen and in 186 of 194 (95.9%) formalin-fixed paraffin-embedded gastric biopsy specimens, respectively. The genotyping method was next used to address the relationship between the vacA genotypes and the cagA status. The vacA i1 genotype was associated with vacA s1 (where s indicates signal region), vacA m1 (where m indicates middle region), and cagA-positive genotypes (P < 0.0001), while the vacA i2 genotype was closely related with vacA s2, vacA m2, and cagA-negative genotypes (P < 0.0001). The relationship between H. pylori vacA i-region genotypes and gastric disease development was subsequently evaluated in the Portuguese population. Patients infected with vacA i1 strains showed an increased risk for gastric atrophy and for gastric carcinoma, with odds ratios of 8.0 (95% confidence interval [CI], 2.3 to 27) and of 22 (95% CI, 7.9 to 63), respectively. Taken together, the results show that this novel H. pylori vacA i-region genotyping method can be applied directly to archive material, providing a fast evaluation of strain virulence determinants without the need of culture. The results further emphasize that the characterization of the vacA i region may be useful to identify patients at higher risk of gastric carcinoma development.     

Typing of Helicobacter pylori vacA Gene and Detection of cagA Gene by PCR and Reverse Hybridization

The present report describes an analysis of two virulence genes of Helicobacter pylori. Parts of the cagA gene, as well as parts from the signal (s) and middle (m) regions of the mosaic vacA gene, were amplified with biotin-labelled PCR primers and the products were subsequently analyzed by a single-step reverse hybridization line probe assay (LiPA). This assay comprises a strip containing multiple specific probes for the vacA s region (s1a, s1b, and s2 alleles), the vacA m region (m1 and m2 alleles), and the cagA gene. A total of 103 H. pylori-positive materials, including cultured isolates, gastric biopsy specimens, and surgical specimens from patients living in Portugal (n = 55) and The Netherlands (n = 48) were tested by the PCR-LiPA. cagA was detected in 84 and 73% of the Portuguese and Dutch patients, respectively. vacA typing results, as determined by reverse hybridization, were completely concordant with those of sequence analysis. Most Portuguese patients (72%) contained type s1b, whereas most Dutch patients (61%) contained type s1a (P < 0.001). The method is also very effective at detecting the presence of multiple genotypes in a single biopsy specimen. The prevalence of multiple strains in Portuguese patient samples was significantly higher (29%) than that in Dutch patient samples (8%) (P = 0.001). There was a significant association between the presence of ulcers or gastric carcinoma and the presence of vacA type s1 (s1a or s1b; P = 0.008) and cagA (P = 0.003) genes.     

Variants of the 3′ Region of the cagA Gene in Helicobacter pylori Isolates from Patients with Different H. pylori-Associated Diseases

The CagA protein of Helicobacter pylori is an immunogenic antigen of variable size and unknown function that has been associated with increased virulence as well as two mutually exclusive diseases, duodenal ulcer and gastric carcinoma. The 3′ region of the cagA gene contains repeated sequences. To determine whether there are structural changes in the 3′ region of cagA that predict outcome of H. pylori infection, we examined 155 cagA gene-positive H. pylori isolates from Japanese patients including 50 patients with simple gastritis, 40 with gastric ulcer, 35 with duodenal ulcer, and 30 with gastric cancer. The 3′ region of the cagA gene was amplified by PCR followed by sequencing. CagA proteins were detected by immunoblotting using a polyclonal antibody against recombinant CagA. One hundred forty-five strains yielded PCR products of 642 to 651 bp; 10 strains had products of 756 to 813 bp. The sequence of the 3′ region of the cagA gene in Japan differs markedly from the primary sequence of cagA genes from Western isolates. Sequence analysis of the PCR products showed four types of primary gene structure (designated types A, B, C, and D) depending on the type and number of repeats. Six of the seven type C strains were found in patients with gastric cancer (P < 0.01 in comparison to noncancer patients). Comparison of type A and type C strains from patients with gastric cancer showed that type C was associated with higher levels of CagA antibody and more severe degrees of atrophy. Differences in cagA genotype may be useful for molecular epidemiology and may provide a marker for differences in virulence among cagA-positive H. pylori strains.     

Expanding Allelic Diversity of Helicobacter pylori vacA

The diversity of the gene encoding the vacuolating cytotoxin (vacA) of Helicobacter pylori was analyzed in 98 isolates obtained from different geographic locations. The studies focused on variation in the previously defined s and m regions of vacA, as determined by PCR and direct sequencing. Phylogenetic analysis revealed the existence of four distinct types of s-region alleles: aside from the previously described s1a, s1b, and s2 allelic types, a novel subtype, designated s1c, was found. Subtype s1c was observed exclusively in isolates from East Asia and appears to be the major s1 allele in that part of the world. Three different allelic forms (m1, m2a, and m2b) were detected in the m region. On the basis of sequence alignments, universal PCR primers that allow effective amplification of the s and m regions from H. pylori isolates from all over the world were defined. Amplimers were subsequently analyzed by reverse hybridization onto a line probe assay (LiPA) that allows the simultaneous and highly specific hybridization of the different vacA s- and m-region alleles and tests for the presence of the cytotoxin-associated gene (cagA). This PCR-LiPA method permits rapid analysis of the vacA and cagA status of H. pylori strains for clinical and epidemiological studies and will facilitate identification of any further variations.     

Experimental Infection of Mongolian Gerbils with Wild-Type and Mutant Helicobacter pylori Strains

Experimental Helicobacter pylori infection was studied in Mongolian gerbils with fresh human isolates that carry or do not carry cagA (cagA-positive or cagA-negative, respectively), multiply passaged laboratory strains, wild-type strain G1.1, or isogenic ureA, cagA, or vacA mutants of G1.1. Animals were sacrificed 1 to 32 weeks after challenge, the stomach was removed from each animal for quantitative culture, urease test, and histologic testing, and blood was collected for antibody determinations. No colonization occurred after ≥20 in vitro passages of wild-type strain G1.1 or with the ureA mutant of G1.1. In contrast, infection occurred in animals challenged with wild-type G1.1 (99 of 101 animals) or the cagA (25 of 25) or vacA (25 of 29) mutant of G1.1. Infection with G1.1 persisted for at least 8 months. All 15 animals challenged with any of three fresh human cagA-positive isolates became infected, in contrast to only 6 (23%) of 26 animals challenged with one of four fresh human cagA-negative isolates (P < 0.001). Similar to infection in humans, H. pylori colonization of gerbils induced gastric inflammation and a systemic antibody response to H. pylori antigens. These data confirm the utility of gerbils as an animal model of H. pylori infection and indicate the importance of bacterial strain characteristics for successful infection.     

<Emphasis Type="Italic">Helicobacter pylori</Emphasis> Virulence Genotypes in Portuguese Children and Adults with Gastroduodenal Pathology

The aim of this study was to evaluate the prevalence of virulence genotypes, namely cagA, vacA and babA2, of Helicobacter pylori strains isolated from Portuguese adults and children presenting gastroduodenal pathology. One hundred thirty-six strains were studied, 82 isolated from adult patients (50 with nonulcerative gastritis and 32 with active peptic ulcer) and 58 isolated from children (54 with nonulcerative gastritis and 4 with duodenal ulcer). Genotyping of cagA, vacA and babA2 was assessed by polymerase chain reaction. Overall, Helicobacter pylori strains carrying more virulent genotypes were much more prevalent in adults than in children, particularly the type I (vacAs1- and cagA-positive) and the triple-positive (vacAs1-, cagA- and babA2-positive) strains (P<0.001). A subpopulation of adults and children with nonulcerative gastritis was also studied, and differences in the prevalence of virulent genotypes were observed, either for individual genotypes (P=0.017 for cagA, P=0.010 for vacAs1) or in combinations, i.e. the type I genotype (P=0.005) and the triple-positive strains (P=0.031). There was no difference between the two populations in the distribution of babA2 and m1/m2 genotypes. Considering the cohort effect in the epidemiology of Helicobacter pylori infection, these results suggest that different strains might circulate during different periods of time, or that, after infection in childhood, individual strains will undergo changes during the course of infection. Electronic Publication     

Local and Systemic Immune and Inflammatory Responses to Helicobacter pylori Strains

Colonization with Helicobacter pylori eventuates in varied clinical outcomes, which relate to both bacterial and host factors. Here we examine the relationships between cagA status, serum and gastric juice antibody responses, and gastric inflammation in dyspeptic patients. Serum, gastric juice, and gastric biopsy specimens were obtained from 89 patients undergoing endoscopy. H. pylori colonization and cagA status were determined by histology, culture, and PCR methods, and acute inflammation and chronic inflammation in the gastric mucosa were scored by a single pathologist. Serum and gastric juice antibodies to H. pylori whole-cell and CagA antigens were determined by enzyme-linked immunosorbent assay. Relationships between variables were sequentially analyzed using univariate and multivariate statistical methods. Of the 89 subjects, 62 were colonized by H. pylori. By univariate analyses, levels of serum immunoglobulin G (IgG) and IgA and gastric juice IgA antibodies against whole-cell and CagA antigens each were significantly higher in the H. pylori-positive group than in the H. pylori-negative group (P < 0.001). H. pylori and CagA seropositivities were both significantly associated with enhanced inflammation in gastric antrum and body (P < 0.02). The presence of gastric juice antibodies to H. pylori antigens was associated with more severe gastric inflammation. However, in multivariate analyses, only the presence of serum antibodies against CagA and, to a lesser extent, whole-cell antigens remained significantly associated with acute and chronic inflammation in antrum and body (P < 0.05). Thus, serum antibody response to CagA correlates with severity of gastric inflammation. Furthermore, given the relationships demonstrated by multivariate analysis, determination of gastric juice antibodies may provide a better representation of serum, rather than secretory, immune response.     

CagA subtyping in Helicobacter pylori isolates from gastric cancer patients in an ethnic Kashmiri population

The association between gastric cancer and Helicobacter pylori has been well established. Among H. pylori virulence genes the most important determinant is the cytotoxin associated antigen gene (cagA) which is characterized by the presence of repeated EPIYA motifs at the C terminus of the protein. From the alignment and number of these EPIYA motifs, two major types of CagA protein have been identified.AimsThe aim of this study was to classify the CagA into eastern or western type and to determine the number and type of motifs present.MethodsThe CagA subtyping was done by PCR and multiplex PCR for eastern/western classification and determination of EPIYA motifs respectively.ResultsAll the isolates studied were of the western type, with 70% of the isolates having more than one EPIYA-C motifs. No statistically significant association was found between the presence of CagA and more than one EPIYA-C motifs with the clinical outcome (differentiation status of the tumour).     

Virulence factor genotypes of Helicobacter pylori affect cure rates of eradication therapy

The cure rates of Helicobacter pylori infection by using a combination of a proton pump inhibitor (PPI) and antimicrobial agents are mainly influenced by bacterial susceptibility to antimicrobial agents and the magnitude of acid inhibition during the treatment. Currently used empirical triple therapies do not reliably produce a ≥80% cure rate on an intention-to-treat basis. Therefore, tailored regimens based on relevant microbiological findings and pharmacogenomics are recommended for attaining an acceptable ≥95% cure rate. Recently, virulence factors of H. pylori, such as cagA and vacA, are reported to be major factors determining the cure rates. Individuals infected with strains with cagA-negative and vacA s2 genotypes have significantly increased risk of eradication failure of H. pylori infection. These virulence factors enhance gastric mucosal inflammation and are associated with the development of peptic ulcer and gastric cancer. H. pylori virulence factors induce proinflammatory cytokines, such as interleukin (IL)-1, IL-8, and tumor necrosis factor (TNF)-  which influence mucosal inflammation and/or gastric acid secretion. When physicians select an H. pylori eradication regimen with an acceptable cure rate, they might need to consider H. pylori virulence factors, especially cagA and vacA.     

CagA and VacA Polymorphisms Do Not Correlate with Severity of Histopathological Lesions in Helicobacter pylori-Infected Greek Children

The presence of various numbers of EPIYA tyrosine phosphorylation motifs in the CagA protein of Helicobacter pylori has been suggested to contribute to pathogenesis in adults. In this prospective study, we characterized H. pylori isolates from symptomatic children, with reference to the diversity of functional EPIYA motifs in the CagA protein and vacA isotypes, and assessed the potential correlation with the histopathological manifestations of the infection. We analyzed 105 H. pylori isolates from 98 children and determined the diversity of EPIYA motifs in CagA by amplification and sequencing of the 3′ variable region of the cagA gene as well as vacA isotypes for the signal, middle, and intermediate regions. CagA phosphorylation and levels of secreted IL-8 were determined following in vitro infection of AGS gastric epithelial cells. Histopathological evaluation of H. pylori colonization, activity, and severity of the associated gastritis was performed according to the updated Sydney criteria. EPIYA A (GLKN[ST]EPIYAKVNKKK), EPIYA B (Q[V/A]ASPEPIY[A/T]QVAKKVNAKI), and EPIYA C (RS[V/A]SPEPIYATIDDLG) motifs were detected in the ABC (46.6%) and ABCC (17.1%) combinations. No isolates harboring more than two EPIYA C motifs in CagA were found. The presence of isogenic strains with variable numbers of CagA EPIYA C motifs within the same patient was detected in seven cases. Occurrence of increasing numbers of EPIYA C motifs correlated strongly with presence of a high-vacuolation (s1 or s2/i1/m1) phenotype and age. A weak positive correlation was observed between vacuolating vacA genotypes and presence of nodular gastritis. However, CagA- and VacA-dependent pathogenicities were not found to contribute to severity of histopathology manifestations in H. pylori-infected children.Helicobacter pylori infects 50% of the world''s population, and wide differences in prevalence of infection appear to exist between countries with different levels of socioeconomic development. Infection usually occurs in childhood and in the majority of cases remains asymptomatic, although major reasons for endoscopy referral can include recurrent epigastric or abdominal pain, with or without vomiting, neither of which correlates with H. pylori infection (17). Antral nodularity is a well-described endoscopic feature of H. pylori-infected children, and histological observations usually include superficial chronic active gastritis with occasional infiltration of eosinophils; in far fewer cases, they include peptic ulcers; and very rarely, they include gastric atrophy and intestinal metaplasia (13, 27). If the infection is left untreated, it persists through adulthood, and although it can still remain asymptomatic in the vast majority of infected hosts, H. pylori infection is now regarded as the most important etiological risk factor for development of gastric cancer in developed countries (28). H. pylori pathogenesis is manifested through a combined effect of bacterial virulence factors, host genetics, and environmental factors, which orchestrate toward the development of distinct phenotypes in adults, namely, superficial asymptomatic gastritis, duodenal ulcer, and gastric cancer (3). The expression and translocation of cytotoxin-associated gene antigen (CagA), a putative H. pylori virulence factor, inside gastric epithelial cells by cagA-positive H. pylori strains harboring a functional type IV secretion system has been suggested to play an important role in H. pylori pathogenesis (22). Early epidemiological studies of adults associated the presence of the cagA gene with development of peptic ulcer disease (31); gastric cancer (14); and increased inflammation (35), cellular proliferation (36), and intestinal metaplasia (20) of the gastric mucosa. However, in infected children, neither cagA status nor any other putative H. pylori virulence factor has been found to correlate with clinical outcome or severity of histological manifestations. However, recent advances into the fascinating cellular biology of CagA inside the gastric epithelial cell have enhanced its reputation as a potential bacterial oncoprotein (22). Following its translocation inside the gastric epithelial cell via the type IV secretion system (32), CagA has been shown to become at least partly tyrosine phosphorylated (5, 11, 41) by Src family kinases (42, 44) on repeating 5-amino-acid glutamic-proline-isoleucine-tyrosine-alanine (EPIYA) motifs present at the C terminus of the protein. Analysis of EPIYA motifs in CagA has revealed considerable type variation, depending on the peptide sequence surrounding it, namely, EPIYA A (EPIYAKVNKKK), EPIYA B (EPIYAQVAKKV), or EPIYA C (EPIYATIDDLG) in isolates from Western populations or EPIYA D (EPIYATIDFD) in isolates of Asian origin. In addition, considerable variation in number of repeating EPIYA C or D motifs at the carboxyl terminus of the protein (10, 44) has been observed, and biological activity of CagA was suggested to be determined by variation in these motifs (25) in phosphorylation-dependent as well as -independent ways (23). Hence, the number and type of EPIYA phosphorylation motifs may be viewed as putative virulence determinants of CagA activity and therefore become useful clinical markers that may predict the degree of individual H. pylori strain virulence potential. In this context, we proposed a PCR amplification and sequencing-based strategy for accurate characterization of the number and type of EPIYA motifs of CagA in H. pylori clinical isolates (34).A multifactorial role has also been attributed to the secreted VacA virulence factor (16), a protein with multiple cellular activities, as it can disrupt endocytic trafficking of host cells, promote cell death through apoptosis, suppress the local immune system, and possibly potentiate the development of ulcers (6). Although the vacA gene is present in all H. pylori strains, it contains at least three variable parts, the s region, the i region, and the m region, which encode the signal, intermediate, and middle peptides, respectively, which have all been classified as allelic types 1 and 2. The s1-or-s2/i1/m1-or-m2 and s1-or-s2/i1-i2/m1-or-m2 VacA isotypes induce, in general, high and moderate levels of vacuolation, respectively, whereas the s1-or-s2/i2/m1-or-m2 strains induce very little or no vacuolation (39). Consequently, the vacA s/m genotype can also be regarded as a marker of pathogenicity of individual strains (8). Moreover, phylogenetic linkage analysis studies have indicated that there may be a functional basis for the selection of vacA and cagA isotypes (50), although there is substantial distance between vacA loci and cag genes on the bacterial genome. Furthermore, the intermediate region has been associated with development of gastric cancer (39).In the present study, we investigated the potential association of the CagA and VacA virulence factor polymorphisms with clinicopathological manifestations of the disease in symptomatic Greek children. More specifically, H. pylori clinical strains isolated from symptomatic children were characterized with regard to the number and type of repeating EPIYA phosphorylation motifs in CagA protein and the vacA signal, intermediate, and middle region genotypes. Furthermore, these clinical isolates were carefully assessed for their ability to express phosphorylated CagA as well as induce interleukin-8 (IL-8) secretion following infection of gastric epithelial cells. Finally, the potential association of such functional bacterial determinants with H. pylori-associated histopathology in these patients was assessed.