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

Differential H. pylori-Induced MAPK Responses Regulate Lewis Antigen Expression and Colonization Density on Gastric Epithelial Cells Between Children and Adults

Helicobacter pylori causes gastrointestinal diseases, the manifestations of diseases are more serious in adults than in children. Lewis antigen expressions on the gastric epithelium serves as receptors targeted by H. pylori. Moreover, the MAPK signaling pathway involves glycoprotein synthesis of Lewis antigens. We aimed to investigate whether differences in H. pylori-induced MAPK responses mediate gastric Lewis antigens expression and colonization density differently in children and adults. We used human stomach fetal epithelium (HSFE) and SV40-immortalized human normal gastric epithelial (GES-1) cell lines to mimic primary gastric epithelium of children and adults, respectively. H. pylori colonization intensity and Lewis antigens were significantly higher in GES-1 than in HSFE cells, whereas IL-8 and IL-6 levels were significantly higher in HSFE than in GES-1 cells after infection. c-Jun N-terminal kinase (JNK) siRNA and inhibitor (SP600125) experiments showed that Lewis antigen expression and H. pylori colonization were reduced in GES-1 cells but increased in HSFE cells. Furthermore, p-p38 intensity was significantly higher in the superficial epithelium of the children than in the adults with/without H. pylori infection. The overexpression of p38 in GES-1 cells downregulated H. pylori-induced JNK activity mimicking H. pylori infection in children. In conclusion, a higher p38 expression in gastric epithelium counteracting JNK activity in children may contribute to lower Lewis antigen expression and colonization density than in adults after H. pylori infection.

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

DNA Transfer and Toll-like Receptor Modulation by Helicobacter pylori

Helicobacter pylori is the most common bacterial infection worldwide, and virtually all infected persons develop co-existing gastritis. H. pylori is able to send and receive signals from the gastric mucosa, which enables both host and microbe to engage in a dynamic equilibrium. In order to persist within the human host, H. pylori has adopted dichotomous strategies to both induce inflammation as a means of liberating nutrients while simultaneously tempering the immune response to augment its survival. Toll-like receptors (TLRs) and Nod proteins are innate immune receptors that are present in epithelial cells and represent the first line of defense against pathogens. To ensure persistence, H. pylori manipulates TLR-mediated defenses using strategies that include rendering its LPS and flagellin to be non-stimulatory to TLR4 and TLR5, respectively; translocating peptidoglycan into host cells to induce NOD1-mediated anti-inflammatory responses; and translocating DNA into host cells to induce TLR9 activation.

The redefinition of Helicobacter pylori lipopolysaccharide O-antigen and core-oligosaccharide domains

Helicobacter pylori lipopolysaccharide promotes chronic gastric colonisation through O-antigen host mimicry and resistance to mucosal antimicrobial peptides mediated primarily by modifications of the lipid A. The structural organisation of the core and O-antigen domains of H. pylori lipopolysaccharide remains unclear, as the O-antigen attachment site has still to be identified experimentally. Here, structural investigations of lipopolysaccharides purified from two wild-type strains and the O-antigen ligase mutant revealed that the H. pylori core-oligosaccharide domain is a short conserved hexasaccharide (Glc-Gal-DD-Hep-LD-Hep-LD-Hep-KDO) decorated with the O-antigen domain encompassing a conserved trisaccharide (-DD-Hep-Fuc-GlcNAc-) and variable glucan, heptan and Lewis antigens. Furthermore, the putative heptosyltransferase HP1284 was found to be required for the transfer of the third heptose residue to the core-oligosaccharide. Interestingly, mutation of HP1284 did not affect the ligation of the O-antigen and resulted in the attachment of the O-antigen onto an incomplete core-oligosaccharide missing the third heptose and the adjoining Glc-Gal residues. Mutants deficient in either HP1284 or O-antigen ligase displayed a moderate increase in susceptibility to polymyxin B but were unable to colonise the mouse gastric mucosa. Finally, mapping mutagenesis and colonisation data of previous studies onto the redefined organisation of H. pylori lipopolysaccharide revealed that only the conserved motifs were essential for colonisation. In conclusion, H. pylori lipopolysaccharide is missing the canonical inner and outer core organisation. Instead it displays a short core and a longer O-antigen encompassing residues previously assigned as the outer core domain. The redefinition of H. pylori lipopolysaccharide domains warrants future studies to dissect the role of each domain in host-pathogen interactions. Also enzymes involved in the assembly of the conserved core structure, such as HP1284, could be attractive targets for the design of new therapeutic agents for managing persistent H. pylori infection causing peptic ulcers and gastric cancer.

Lipopolysaccharide Structure and Biosynthesis in Helicobacter pylori

This review covers the current knowledge and gaps in Helicobacter pylori lipopolysaccharide (LPS) structure and biosynthesis. H. pylori is a Gram-negative bacterium which colonizes the luminal surface of the human gastric epithelium. Both a constitutive alteration of the lipid A preventing TLR4 elicitation and host mimicry of the Lewis antigen decorated O-antigen of H. pylori LPS promote immune escape and chronic infection. To date, the complete structure of H. pylori LPS is not available, and the proposed model is a linear arrangement composed of the inner core defined as the hexa-saccharide (Kdo-LD-Hep-LD-Hep-DD-Hep-Gal-Glc), the outer core composed of a conserved trisaccharide (-GlcNAc-Fuc-DD-Hep-) linked to the third heptose of the inner core, the glucan, the heptan and a variable O-antigen, generally consisting of a poly-LacNAc decorated with Lewis antigens. Although the glycosyltransferases (GTs) responsible for the biosynthesis of the H. pylori O-antigen chains have been identified and characterized, there are many gaps in regard to the biosynthesis of the core LPS. These limitations warrant additional mutagenesis and structural studies to obtain the complete LPS structure and corresponding biosynthetic pathway of this important gastric bacterium.

Is there any relationship between Le(b) antigen expression and Helicobacter pylori infection?

INTRODUCTION

Helicobacter pylori infection is one of the main causes of peptic ulcer. There are some blood groups acting as receptors for the pathogen. Based on this view and previous attempts, we tried to examine the relationship between Lewis blood group and H. pylori infection.

MATERIALS AND METHOD

Blood and saliva samples were collected from 60 patients with established peptic ulcer induced by H. pylori. Secretory status of each patient was determined by both direct agglutination and saliva tests.

RESULTS

Seventy-two percent of the patients were secretor and expressed Lewis B antigen. This rate in control group was 61%. Statistical analysis showed no significant difference between the two groups.

CONCLUSION

This study did not find any correlation between Le(b) antigen expression and presence of H. pylori-induced peptic ulcer. It is now recommended that other factors like Lewis(x) and sialyl Lewis(x) should be investigated in binding, colonization and virulence of H. pylori infection in the future.

Immune responses to Helicobacter pylori infection in children with intellectual disabilities

Infection with Helicobacter pylori was assessed through serum H. pylori IgG antibody in children with intellectual disabilities (ID). The sero-status of cytotoxin-associated gene A (CagA) was determined as a risk determinant for severe H. pylori-associated diseases. In total, 210 children with ID were included who were permanent resident of three institutes in Tehran. Medical history and demographic data were collected by reviewing the medical file records. The anti H. pylori IgG antibody was detected in serum of 74.8% of children using ELISA. Significant correlations were found between the rate of infection and age (P = 0.001) and duration of institutionalization (P = 0.018). The likelihood of H. pylori IgG positive response increased with age with the highest response in 15-18 years age group (OR = 6.66, 95% CI: 2.14-20.17; P = 0.001). Similarly, the average titers of H. pylori IgG antibody were increased with age. The institutionalization duration of more than 49 months affected the likelihood of H. pylori IgG positive response (OR = 2.437, 95% CI: 1.12-5.26; P = 0.023). Anti-CagA titers were higher than 5arbU/ml in 92 (58.6%) children, indicating a positive response against CagA protein. The titer of H. pylori IgG was significantly higher in CagA-positive (mean ± SE = 51.04 ± 3.41) than in CagA-negative children (38.07 ± 4.18; P = 0.017). In contrast to total H. pylori IgG titers, anti-CagA antibody had non-regular trend of alterations with age. The seropositivity rate of H. pylori infection in ID children was higher than other reports in healthy children from various regions of the country. The risk of H. pylori infection is increased with age and duration of institutionalization. The serostatus of CagA in children with IDs has not been reported so far. The regular monitoring of the CagA-positive carriers is recommended; since CagA positive cases carry the risk of progression of infection toward severe H. pylori associated sequels such as gastric cancer and duodenal ulcers.

Associations between Helicobacter pylori infection, co-morbid infections, gastrointestinal symptoms, and circulating cytokines in African children

BACKGROUND

Refugee children have complex medical needs and often have multiple infections. The relationship between infection, gastrointestinal symptoms, and systemic inflammation is poorly understood. We investigated these parameters in refugee children with a high prevalence of Helicobacter pylori, helminth, and malaria infection.

MATERIALS AND METHODS

African refugee children were recruited at resettlement health screening. Data were collected on demography, gastrointestinal symptoms, co-morbid infection, and serum for peripheral cytokine levels. Helicobacter pylori infection was diagnosed by a fecal-based immunoassay.

RESULTS

Data from 163 children were analyzed, of which 84.0% were positive for H. pylori. Infected children were significantly older (9.2 years +/- 3.7 vs 7.1 years +/- 3.9, p = .01). Half the cohort (84/163, 51.5%) described gastrointestinal symptoms but these were not strongly associated with co-morbid infections. Helicobacter pylori-infected children had significantly lower circulating log-interleukin-8 (IL-8) (odds ratio 0.61, 95% confidence interval (CI) 0.40, 0.94, p = .025). Helminth infections were common (75/163, 46%) and associated with elevated log-IL-5 (beta: 0.42, 95% CI 0.077, 0.76). Children with malaria (15/163, 9.2%) had elevated log-tumor necrosis factor-alpha (TNFalpha) and log-IL-10 (beta: 0.67, 95% CI 0.34, 1.0 and beta: 1.3, 95% CI 0.67, 1.9, respectively). IL-10 : IL-12 ratios were increased in H. pylori-infected children with malaria or helminth infections. Symptoms were generally not associated with levels of circulating peripheral cytokines irrespective of co-morbid infection diagnosis.

CONCLUSIONS

There is a high prevalence of asymptomatic H. pylori infection in recently resettled African refugee children. Gastrointestinal symptoms were not predictive of H. pylori nor of helminth infections. Serum cytokines, particularly IL-5, IL-10, and TNFalpha, were significantly elevated in children with malaria and helminth infections but not in those with H. pylori infection.

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.

Lewis blood genotypes of peptic ulcer and gastric cancer patients in Taiwan

AIM: The Lewis b (Leb) antigen has been implicated as a possible binding site for attachment of Helicobacter pylori (H pylori) to gastric mucosa. However, studies both supporting and denying this association have been reported in the literature. Differences in secretor (Se) genotype have been suggested as a possible reason for previous discrepancies. Therefore, we investigated the relationship between Le and Se genotypes and H pylori infection rates in people with peptic ulcer or gastric cancer.

METHODS: Peripheral blood samples were obtained from 347 patients with endoscopic evidence of peptic ulcer disease (235 cases of duodenal ulcer, 62 of gastric ulcer, and 50 of combined duodenal ulcer/ gastric ulcer) and 51 patients with gastric cancer on endoscopy. Peripheral blood specimens from 101 unrelated normal volunteers were used as controls. Lewis phenotype was determined using an antibody method, whereas Le and Se genotypes were determined by DNA amplification and restriction enzyme analysis. Gastric or duodenal biopsies taken from patients with endoscopic evidence of peptic ulcer or gastric cancer were cultured for H pylori. Isolates were identified as H pylori by morphology and production of urease and catalase. The H pylori infection status was also evaluated by rapid urease test (CLO test), and urea breath test (13C-UBT). Results of studies were analyzed by chi-square test (taken as significant).

RESULTS: H pylori was isolated from 83.7% (303/347) of patients with peptic ulcer disease. Statistical analysis did not show any significant difference in Lewis phenotype or genotype between patients with and without H pylori infection. No significant association was found between Lewis genotype and peptic ulcer or gastric cancer.

CONCLUSION: Lewis blood genotype or phenotype may not play a role in the pathogenesis of H pylori infection. However, bacterial strain differences and the presence of more than one attachment mechanism may limit the value of epidemiological studies in elucidating this matter.