Virulence and colonization-associated properties of Helicobacter pylori isolated from children and adolescents

Helicobacter pylori infection can change the intensity of gastric Lewis antigen expressions differently between adults and children

This study tested whether there were different expressions of gastric Lewis antigens between children and adults with Helicobacter pylori infection, and whether the difference was related to the infection outcome. About 68 dyspeptic children and 110 dyspeptic adults were enrolled to check H. pylori infection, its colonization density, and the related histology. Gastric Lewis antigens b (Le(b)), x (Le(x)), and sialyl-Lewis x (sialyl-Le(x)) were immunohistochemically stained and scored for the intensity. The H. pylori-infected adults, but not the children, had a lower Le(b) intensity over the antrum (p=0.019) but higher Le(b) intensity over the corpus (p=0.001) than the non-infected ones. Over the antrum, both the H. pylori-infected children and adults had a lower Le(x) and higher sialyl-Le(x) intensity than those non-infected ones (p<0.05). The H. pylori-infected adults had a higher bacterial density (p=0.004) and Le(b) intensity (p=0.016) over the corpus than the H. pylori-infected children. For the H. pylori-infected adults, but not children, the corpus had a higher Le(b) (p=0.038) and lower Le(x) (p=0.005) intensity than the antrum. Furthermore, the H. pylori-infected adults expressed a higher Le(b) and had a higher bacterial density than those with weak Le(b) (antrum, p<0.001; corpus, p=0.001). In conclusion, H. pylori infection is associated with the intensity change of Lewis antigen expressions in the stomach. The changes of gastric Lewis antigen expressions are different between adults and children with H. pylori infection, which may exert different H. pylori colonization over the corpus between adults and children.

Specific serum immunoglobulin G to H pylori and CagA in healthy children and adults (south-east of Iran)

AIM: To evaluate the serologic IgG response to H pylori and CagA across age groups and in healthy children and adults.

METHODS: Totally, 386 children aged 1-15 years and 200 adults aged 20-60 years, were enrolled to study. The serum samples of participant were tested for presence of anti-H pylori and anti-CagA IgG by using ELISA method.

RESULTS: The seroprevalence of H pylori in adults was significantly higher than that observed in children (67.5% vs 46.6%; P < 0.000003). In children, the seropositivity rate in males (51.9%) was significantly (P < 0.05) higher than that observed in females (41.7%). The prevalence of serum anti-CagA antibody was 72.8% and 67.4% in infected children and adults, respectively. The mean titer of serum anti-CagA antibodies was significantly higher among children in comparison to adults (64.1 Uarb/mL vs 30.7; P < 0.03). In infected children and adults the prevalence of serum anti-CagA antibody was higher in males compared to females (78.4% vs 66.3%; P = 0.07 and 75.6% vs 54.71%; P < 0.04, respectively). The age-specific prevalence of anti-H pylori and anti-CagA antibody (in infected subjects) was 37.6% and 59.57% at age 1-5 years, 46.9% and 75% at age 6-10 years, 54.9% and 79.45% at age 11-15, 59.01% and 83.33% at age 20-30 years, 66.6% and 60.52% at age 31-40 years, 73.46% and 63.88% at age 41-50 years and 75.75% and 60% at age 51-60 years with mean titer of anti-CagA antibody of 75.94, 63.32, 57.11, 52.06, 23.62, 21.52 and 21.80 Uarb/mL, respectively. There was significant difference between mean serum anti-CagA antibody in age subgroups (P < 0.001).

CONCLUSION: These results showed that anti-H pylori and anti-CagA antibodies were common in the children and adults. The H pylori-specific antibodies influenced by age and sex of subjects. Moreover, it seems that males are more susceptible to infection with CagA⁺ strains compared to females. The seroprevalence of anti-CagA antibody was increased with age, up to 30 years and then decreased. It was also found that the magnitude of the IgG response to CagA decreased with advanced age.

Heterogeneity among Helicobacter pylori strains in expression of the outer membrane protein BabA

The BabA adhesin of Helicobacter pylori is an outer membrane protein that binds to the fucosylated Lewis b histo-blood group antigen on the surface of gastric epithelial cells. We screened a phage-displayed ScFv (single-chain fragment variable) recombinant antibody library for antibodies reactive with a recombinant BabA fragment and identified two such antibodies. Each antibody recognized an approximately 75-kDa protein present in wild-type H. pylori strain J99 but absent from an isogenic babA mutant strain. An immunoreactive BabA protein was detected by at least one of the antibodies in 18 (46%) of 39 different wild-type H. pylori strains and was detected more commonly in cagA-positive strains than in cagA-negative strains. Numerous amino acid polymorphisms were detected among BabA proteins expressed by different strains, with the greatest diversity occurring in the middle region of the proteins. Among the 18 strains that expressed a detectable BabA protein, there was considerable variation in the level of binding to Lewis b in vitro. Heterogeneity among H. pylori strains in expression of the BabA protein may be a factor that contributes to differing clinical outcomes among H. pylori-infected humans.

Lewis antigen expression in gastric mucosa of children: relationship with Helicobacter pylori infection

OBJECTIVE

Lewis epithelial antigen expression has a role in Helicobacter pylori adherence, presumably mainly in cagA-positive strains. The authors investigated whether Lewis antigen expression in children's gastric mucosa was associated with H. pylori infection, cagA status, patient age, or presence of duodenal ulcer (DU).

METHODS

The expression of Lewis A (Le(a)), B (Le(b)), X (Le(x)), and Y (Le(y)) was detected by immunohistochemistry in the antral and oxyntic mucosae of 70 children. Children were divided in four age groups (<4 years; 4-8 years; 9-12 years; and 13-18 years).

RESULTS

Forty-seven of the 70 children had H. pylori and 17 had DU. The cagA status was determined by polymerase chain reaction in 34 patients. Le(a) and Le(b) were expressed in 64% and 44% of the patients, respectively; Le(x) and Le(y) were expressed in the glands in all of the patients and in the superficial epithelium. Le(b) expression was more common among patients without H. pylori (15/23, 65%) than in those with H. pylori (16/47, 34%) (P = 0.03). In noninfected patients, Le(b) and superficial Le(y) expression were associated with increased age. Le(b) expression was more common in patients with chronic gastritis than in those with DU. Le(x) superficial expression was significantly associated with DU in patients with H. pylori.

CONCLUSION

In children, the expression of Le(b) and Le(y) in the superficial gastric epithelium depends on age. Other receptors, such as Le(x), may have a role in H. pylori colonization, especially in patients with DU. Studies assessing the expression of Lewis antigens in children may contribute to an understanding of the mechanisms of acquisition of H. pylori infection.

Helicobacter pylori 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.

Helicobacter pylori-induced activation of human endothelial cells

Helicobacter pylori infection causes active chronic inflammation with a continuous recruitment of neutrophils to the inflamed gastric mucosa. To evaluate the role of endothelial cells in this process, we have examined adhesion molecule expression and chemokine and cytokine production from human umbilical vein endothelial cells stimulated with well-characterized H. pylori strains as well as purified proteins. Our results indicate that endothelial cells actively contribute to neutrophil recruitment, since stimulation with H. pylori bacteria induced upregulation of the adhesion molecules VCAM-1, ICAM-1, and E-selectin as well as the chemokines interleukin 8 (IL-8) and growth-related oncogene alpha (GRO-alpha) and the cytokine IL-6. However, there were large variations in the ability of the different H. pylori strains to stimulate endothelial cells. These interstrain variations were seen irrespective of whether the strains had been isolated from patients with duodenal ulcer disease or asymptomatic carriers and were not solely related to the expression of known virulence factors, such as the cytotoxin-associated gene pathogenicity island, vacuolating toxin A, and Lewis blood group antigens. In addition, one or several unidentified proteins which act via NF-kappaB activation seem to induce endothelial cell activation. In conclusion, human endothelial cells produce neutrophil-recruiting factors and show increased adhesion molecule expression after stimulation with certain H. pylori strains. These effects probably contribute to the continuous recruitment of neutrophils to H. pylori-infected gastric mucosa and may also contribute to tissue damage and ulcer formation.

iceA genotypes of Helicobacter pylori strains isolated from Brazilian children and adults

Data concerning the geographic distribution of iceA alleles are scarce, and information on the association of the gene with the disease is rare and still controversial. Furthermore, no such study has been developed in Brazil, where duodenal ulcer and gastric adenocarcinoma are very common. We investigated, by PCR, the frequency of iceA alleles and cagA status in Helicobacter pylori strains isolated from 142 patients (62 children and 80 adults; 66 female; mean age, 30.0 years; age range, 3 to 78 years) with gastritis, duodenal ulcer, or gastric adenocarcinoma. iceA was identified in bacterium samples obtained from all patients. Eleven (7.7%) of them were infected with multiple strains. Among the patients with nonmixed infection, iceA2 allele was detected in 118 (90.1%). iceA2 allele was associated with ulcer (P = 0.02) and with carcinoma (P = 0.001). iceA2 amplicons of 229, 334, or 549 bp were detected, but none of them was associated with the patient's disorder. iceA2 strains were more frequent in patients older than 7 years (P = 0.001). The gene was also more frequent in strains obtained from males (P = 0.02). cagA was more common in strains obtained from carcinoma (P = 0.0008) and ulcer patients (P < 0.006). cagA-positive strains were more frequent in children older than 7 years (P < 0.003). No association between cagA status and sex was found (P = 0.28). In conclusion, we think iceA should not be used as a reliable marker for predicting the clinical outcome of H. pylori infection.

Helicobacter pylori infection in children: update

Despite its worldwide distribution, the pathogenesis of Helicobacter pylori associated gastroduodenal disease remains poorly understood. What is clear is that H. pylori infection rarely resolves spontaneously and that the chronic gastritis that accompanies infection is typically maintained for the duration of infection. Ultimately, if untreated, this chronic inflammation predisposes a subset of individuals to develop gastric or duodenal ulcers and even gastric cancer. Chronic long-lasting H. pylori infection, particularly when acquired early in childhood, can predispose an individual to a significantly increased risk of developing gastric cancer. These studies were so compelling that the World Health Organization has recently classified H. pylori as a type 1 human carcinogen. Since the discovery of H. pylori less than 20 years ago, this infection has continued to generate considerable interest in the medical and scientific community. As we enter the new millenium, there are now a number of effective treatments for children in whom H. pylori-associated peptic ulcer disease is diagnosed. Although there is now overwhelming evidence to confirm that H. pylori plays an etiologic role in the development of peptic ulcer disease, only a small number of these children develop H. pylori disease. In this review, we highlight some of the recently published pediatric studies addressing the role H. pylori plays in the development of gastroduodenal disease in children.

Differences in surface-exposed antigen expression between Helicobacter pylori strains isolated from duodenal ulcer patients and from asymptomatic subjects

We have analyzed possible qualitative and quantitative differences in antigen expression between Helicobacter pylori strains isolated from the antrum and different locations in the duodenum of 21 duodenal ulcer (DU) patients and 20 asymptomatic subjects (AS) by enzyme-linked immunosorbent assay (ELISA) and inhibition ELISA. Almost all antral and duodenal strains grown in vitro expressed the N-acetyl-neuroaminyllactose-binding hemagglutinin, flagellins (subunits FlaA and FlaB), urease, a 26-kDa protein, and a neutrophil-activating protein. In 75% of both the DU patients and the AS, antral H. pylori strains expressed either the blood group antigen Lewis y (Le(y)) alone or together with the Le(x) antigen. However, duodenal H. pylori strains of DU patients expressed Le(y) antigen more frequently than corresponding strains of AS (P < 0.05). Presence of Le(y) on H. pylori was related to the degree of active duodenitis (P < 0.05). Duodenal H. pylori strains isolated from AS were significantly more often Lewis nontypeable than duodenal strains of DU patients (P < 0.01). Presence of H. pylori blood group antigen-binding adhesin (BabA) was significantly higher on both antral and duodenal strains isolated from DU patients than on corresponding strains isolated from AS (P < 0.05). BabA-positive duodenal H. pylori strains isolated from DU patients were associated with active duodenitis more frequently than corresponding strains isolated from AS (P < 0.01). Infection with H. pylori strains positive for Le(y) and BabA in the duodenum is associated with development of duodenal ulcer formation.

A comprehensive review of the natural history of Helicobacter pylori infection in children

Across populations of children, Helicobacter pylori prevalence ranges from under 10% to over 80%. Low prevalence occurs in the U.S., Canada, and northern and western Europe; high prevalence occurs in India, Africa, Latin America, and eastern Europe. Risk factors include socioeconomic status, household crowding, ethnicity, migration from high prevalence regions, and infection status of family members. H. pylori infection is not associated with specific symptoms in children; however, it is consistently associated with antral gastritis, although its clinical significance is unclear. Duodenal ulcers associated with H. pylori are seldom seen in children under 10 years of age. H. pylori-infected children demonstrate a chronic, macrophagic, and monocytic inflammatory cell infiltrate and a lack of neutrophils, as compared with the response observed in adults. The effect of H. pylori infection on acid secretion in children remains poorly defined. The events that occur during H. pylori colonization in children should be studied more thoroughly and should include urease activity, motility, chemotaxis, adherence, and downregulation of the host response. The importance of virulence determinants described as relevant for disease during H. pylori infection has not been extensively studied in children. Highly sensitive and specific methods for the detection of H. pylori in children are needed, especially in younger pediatric populations in which colonization is in its early phases. Criteria for the use of eradication treatment in H. pylori-infected children need to be established. Multicenter pediatric studies should focus on the identification of risk factors, which can be used as prognostic indicators for the development of gastroduodenal disease later in life.

vacA genotypes in Helicobacter pylori strains isolated from children with and without duodenal ulcer in Brazil

Data concerning the association between vacA genotypes and disease in children in both developed and developing countries are scarce, especially because of the small number of children with a duodenal ulcer studied. The vacA genotypes of Helicobacter pylori strains obtained from 65 children (24 with a duodenal ulcer and 41 without a duodenal ulcer; 33 girls; mean age, 10.2 years; age range, 1 to 17 years) were investigated as described by J. C. Atherton et al. (J. Clin. Microbiol. 37:2979-2982, 1999). Ten (15.4%) children were infected with more than one H. pylori strain. None of these patients were included in our analysis of the relationship between gastric disorders and specific vacA genotypes. The s1 allele was detected in all H. pylori strains isolated from patients with a duodenal ulcer and from 21 (58.3%) patients without a duodenal ulcer (P = 0.003). Strains with the s2 allele were found only in patients without ulcer (n = 15; 41.7%). Most s1 strains had the s1b allele (97.5%), a result similar to that reported for adults from the Iberian peninsula, which could reflect the Brazilian population origin. One untypeable s1 strain was isolated. The m1 allele was also more frequently found in strains obtained from duodenal ulcer patients (P = 0.028). The m2 allele was found in strains obtained from 20 (36. 4%) children, 3 (15.8%) with an ulcer and 17 (47.2%) without an ulcer. Only one m hybrid strain (m1 and m2 hybrid) was detected. It was demonstrated for the first time that the frequencies of colonization with strains with the s1 allele (14.3% in children up to 8 years of age and 85.7% in older patients; P = 0.012) and of strains with the m1 allele (11.1% in patients up to the age 8 years and 88.9% in older children; P = 0.013) increase with age.

CagA antibodies in Japanese children with nodular gastritis or peptic ulcer disease

cagA(+) Helicobacter pylori strains have been linked to more severe gastric inflammation, peptic ulcer disease, and gastric cancer in adults, but there have been few studies of cagA in children. We examined the relationship between H. pylori cagA status and clinical status in Japanese children. Forty H. pylori-positive children were studied: 15 with nodular gastritis, 5 with gastric ulcers, and 20 with duodenal ulcers. H. pylori status was confirmed by biopsy-based tests and serum anti-H. pylori immunoglobulin G (IgG) antibody. As controls, 77 asymptomatic children with sera positive for anti-H. pylori IgG were enrolled. Levels of IgG antibodies to CagA in serum were measured by an antigen-specific enzyme-linked immunosorbent assay. In 16 patients with successful H. pylori eradication, posttreatment levels of CagA and H. pylori IgG antibodies also were studied. The CagA antibody seropositivities of asymptomatic controls (81.8%) and patients with nodular gastritis, gastric ulcers, and duodenal ulcers (80.0 to 95.0%) were not significantly different. Compared with pretreatment levels of CagA antibodies, posttreatment levels decreased progressively and significantly. We conclude that, as in Japanese adults, a high prevalence of cagA(+) H. pylori strains was found in Japanese children, and that there was no association with nodular gastritis or peptic ulcer disease. In the assessment of eradicative therapies, monitoring of serum anti-CagA antibodies does not appear to offer any direct benefit over monitoring of anti-H. pylori antibodies.

Clinical relevance of the Helicobacter pylori gene for blood-group antigen-binding adhesin

Infection with Helicobacter pylori is associated with different human gastric diseases. Biochemical studies, in vitro adherence assays, and in vivo animal models revealed that epithelial attachment of H. pylori can be mediated by the blood-group antigen-binding adhesin (BabA) targeting human Lewis(b) surface epitopes. Studies with transgenic mice expressing the Lewis(b) epitope have shown that such attachment can alter disease outcome. In the current study, the presence of the babA2 gene encoding the adhesin was investigated in clinical isolates from a German population by using PCR and reverse transcription-PCR. A positive genotype was correlated to allelic variations in the genes encoding VacA and CagA and also to the prevalence of duodenal ulcer, distal gastric adenocarcinoma, mucosa-associated lymphoid tissue lymphoma, and antral gastritis. The presence of babA2 was significantly associated with duodenal ulcer (P = 0.0002) and adenocarcinoma (P = 0.033). In contrast, type 1 strains (vacAs1- and cagA-positive) were associated with only duodenal ulcer (P = 0.004) but not adenocarcinoma (P = 0.235). Genotype presence of babA2, vacAs1, and cagA ("triple-positive" strains) showed a highly significant correlation to the prevalence of ulcer (P = 0.000002) and adenocarcinoma (P = 0.014) and discriminated significantly better between disease outcome than did the current type 1 classification. These results indicate that the babA2 gene is of high clinical relevance and would be a useful marker to identify patients who are at higher risk for specific H. pylori-related diseases.

Relationship of vacA genotypes of Helicobacter pylori to cagA status, cytotoxin production, and clinical outcome

BACKGROUND

Mosaicism in vacA alleles with three distinct families of vacA signal sequences (s1a, s1b and s2) and two distinct families of middle region alleles (m1 and m2) has been reported. It was suggested that the vacA s1a genotype was closely associated with duodenal ulcer disease and with high cytotoxin production. The aim of this study was to evaluate the role of vacA genotyping with respect to gastric inflammation and injury, cytotoxin activity, and clinical presentation.

METHODS

H. pylori from patients with gastritis, peptic ulcer disease, or gastric cancer were characterized by vacA typing by polymerase chain reaction (PCR) and DNA sequencing. In vitro cytotoxin activity was assessed by vacuolation assay using Vero cells as well as with Hela cells.

RESULTS

Four hundred ninety-one strains were tested. vacA genotype s1a/m1 was present in more than 95% of strains independent of presentation with gastritis, peptic ulcer, or gastric cancer. No vacA genotype was associated with high average cytotoxin activity. The s2/m2 isolates had low or absent cytotoxin activity. All cagA negative strains (n = 18) were s1a strains and both s2/m2 strains were cagA positive. One strain that was a recombinant of m1 and m2 strains was identified and had low cytotoxin activity. The nucleotide and amino acid sequences between original m1 strains and Japanese m1 strains (new m1 strains) were about 85% and 81%, respectively. Strains with the new m1 genotype had nucleotide and amino acid sequences similarity of more than 96%. There was no difference in cytotoxin activity between strains with the Western type m1 and the new type m1 genotype.

CONCLUSION

In this as in other reported studies ( approximately 1500 patients overall) vacA genotype was strongly but not exclusively associated with the presence of cagA. Overall, the studies did not support a role for vacA genotyping in relation to cytotoxin activity, virulence, histologic finding, or risk of a particular H. pylori disease. vacA genotype s1 is likely to be a surrogate marker for the presence of the cag pathogenicity island.