Different patterns of Helicobacter pylori adherence to gastric mucosa cells in children and adults. An ultrastructural study

Prevalence of Helicobacter pylori virulence genotypes among children in Eastern Turkey

AIM: To identify the virulence genotypes of Helicobacter pylori (H. pylori) if present in children in Eastern Turkey and if those genotypes are mostly associated with severe clinical presentations.

METHODS: A total of 49 H. pylori positive Turkish children (42 with antral nodularity and 7 with peptic ulcer) who underwent upper gastrointestinal endoscopy with abdominal symptoms during the period from March 2011 to September 2012 were enrolled in this study. Antral nodularity was diagnosed endoscopically by two of the authors. We determined for the presence of cagA, vacA, cagE, iceA and babA2 genotypes of H. pylori isolates in DNA obtained directly from frozen gastric biopsy samples by polymerase chain reaction test using specific primers.

RESULTS: Of the 49 H. pylori isolates studied, 61.2%, 91.8%, 22.4%, 28.6%, 57.1% and 40.8% were positive for the cagA, vacA s1, cagE, iceA1, iceA2 and babA2 genes, respectively. We showed that the most common vacA subtype was s1a (79.6%). However, the s2 gene was found less frequently with an isolation rate of 8.2% of the H. pylori isolates. The genotypes iceA2 and vacA s1m2 were the most frequently found types in children with antral nodularity. In addition, the genotypes iceA1, babA2 and vacA s1m1 were found in similar ratios in all the H. pylori isolates obtained from children with peptic ulcer. The genotypes vacA s2m1 and s1c were not observed in any of isolates studied.

CONCLUSION: This study showed that vacA s1m2, cagA and iceA2 were the most common genotypes, and no association between antral nodularity and genotypes was observed.

Association of Malaysian Helicobacter pylori virulence polymorphisms with severity of gastritis and patients' ethnicity

BACKGROUND AND AIM

Polymorphisms of Helicobacter pylori cagA and vacA genes do exist and may contribute to differences in H. pylori infection and gastroduodenal diseases among races in the Malaysian population. This study was conducted to characterize the polymorphisms in H. pylori cagA and vacA in Malaysian population.

METHODS

A total of 110 H. pylori isolates were genotyped by PCR and sequenced for cagA and PCR-RFLP for vacA.

RESULTS

East Asian cagA was predominantly detected (64.5%), whereas vacA s1m1 and s1m2 alleles were detected in 60.9 and 37.3% of strains, respectively. A statistical association between cagA type with patients' ethnicity (p < .0001) and age group >50 years old (p = .027) was identified. vacA alleles showed significant association with age group >50 years old (p = .017) and increased neutrophil activity in gastric mucosa (p = .028 and p = .016 for moderate and marked activity, respectively). Further identification of vacA polymorphism revealed that 84% of strains from Malays and Indians showed one RFLP pattern (RFLP-1), whereas more than one RFLP patterns (RFLP-2, 3, 4, 5, 6, and 8) were predominantly observed in strains from Chinese (82%) (p < .0001). Increasing severity of gastric inflammation was observed in gastric mucosa infected with strains carrying RFLP-2, 3, 4, 5, and 6 (p = .037). About 86.6% of H. pylori strains with East Asian cagA were vacA RFLP-2, 3, 4, 5, 6, and 8, and 88% of Western cagA strains were vacA RFLP-1 (p < .0001). Chinese and Indians are susceptible to different virulence genotypes of H. pylori, whereas Malays showed a mixed virulence genotypes.

CONCLUSION

Marked differences in the polymorphisms of cagA and vacA were observed among strains in Malaysian population. This provides a new insight into the pathogenicity of H. pylori in multiracial population.

Role of mucin Lewis status in resistance to Helicobacter pylori infection in pediatric patients

BACKGROUND

Helicobacter pylori causes gastritis, peptic ulcer and is a risk factor for adenocarcinoma and lymphoma of the stomach. Gastric mucins, carrying highly diverse carbohydrate structures, present functional binding sites for H. pylori and may play a role in pathogenesis. However, little information is available regarding gastric mucin in children with and without stomach diseases.

MATERIALS AND METHODS

Expression of mucins and glycosylation was studied by immunohistochemistry on gastric biopsies from 51 children with and without H. pylori infection and/or peptic ulcer disease.

RESULTS

In all children, MUC5AC was present in the surface epithelium and MUC6 in the glands. No MUC6 in the surface epithelium or MUC2 was detected in any section. The Le(b) and Le(a) blood group antigens were present in the surface epithelium of 80% and 29% of children, respectively. H. pylori load was higher in Le(b) negative children than in Le(b) positive individuals (mean +/- SEM 17.8 +/- 3.5 vs 10.8 +/- 1.5; p < 0.05), but there was no correlation between Le(a) or Le(b) status and gastritis, nodularity, and gastric or duodenal ulcer (DU). Expression of sialyl-Le(x) was associated with H. pylori infection, and DU.

CONCLUSIONS

Mucin expression and glycosylation is similar in children and adults. However, in contrast to adults, pediatric H. pylori infection is not accompanied by aberrant expression of MUC6 or MUC2. Furthermore, the lower H. pylori density in Le(b) positive children indicates that H. pylori is suppressed in the presence of gastric mucins decorated with Le(b), the binding site of the H. pylori BabA adhesin.

Influence of type IV pilus retraction on the architecture of the Neisseria gonorrhoeae-infected cell cortex

Early in infection, Neisseria gonorrhoeae can be observed to attach to the epithelial cell surface as microcolonies and induce dramatic changes to the host cell cortex. We tested the hypothesis that type IV pili (Tfp) retraction plays a role in the ultrastructure of both the host cell cortex and the bacterial microcolony. Using serial ultrathin sectioning, transmission electron microscopy and 3D reconstruction of serial 2D images, we have obtained what we believe to be the first 3D reconstructions of the N. gonorrhoeae-host cell interface, and determined the architecture of infected cell microvilli as well as the attached microcolony. Tfp connect both wild-type (wt) and Tfp retraction-deficient bacteria with each other, and with the host cell membrane. Tfp fibres and microvilli form a lattice in the wt microcolony and at its periphery. Wt microcolonies induce microvilli formation and increases of surface area, leading to an approximately ninefold increase in the surface area of the host cell membrane at the site of attachment. In contrast, Tfp retraction-deficient microcolonies do not affect these parameters. Wt microcolonies had a symmetrical, dome-shaped structure with a circular 'footprint', while Tfp retraction-deficient microcolonies were notably less symmetrical. These findings support a major role for Tfp retraction in microvilli and microcolony architecture. They are consistent with the biophysical attributes of Tfp and the effects of Tfp retraction on epithelial cell signalling.

Helicobacter pylori-coccoid forms and biofilm formation

Electron microscopic studies have shown that Helicobacter pylori occurs in three stages: spiral forms, coccoid forms and degenerative forms. The spiral forms are viable, culturable, virulent and can colonize experimental animals and induce inflammation. The coccoid forms may also be viable but are nonculturable, less virulent and are less likely to colonize and induce inflammation in experimental animals than the spiral forms. The degenerative forms are pyknotic, nonculturable, coccoid forms of dead H. pylori. These forms cannot be cultured and the cell membrane has disintegrated but gene material can be detected by PCR in water supplies. There is no substantial evidence for viable H. pylori persisting in water supplies. Epidemiological studies suggest that environmental water is a risk factor for H. pylori infection when compared with tap water, and formation of H. pylori biofilm cannot be excluded. Helicobacter pylori does not seem to take part in biofilm formation in the oral cavity even though the bacterium may be detected.

Colonization and infection by Helicobacter pylori in humans

When Helicobacter pylori arrives in the human stomach, it may penetrate the mucin layer and adhere to the gastric epithelial cells or it may pass through the stomach without colonizing the mucosa. In this paper, the colonization process and the ensuing immunological response will be briefly described. Urease production is necessary for H. pylori to establish a pH-neutral microenvironment around the bacteria. The flagella enable the bacteria to move and the shape of H. pylori makes it possible to penetrate the mucin layer where it comes into contact with the gastric epithelial cells. H. pylori contains several adhesins that enable it to adhere to the epithelial cells. This adherence activates IL-8 which, together with bacterial antigens, attracts polymorphs and monocytes and causes acute gastritis. Antigen-presenting cells activate lymphocytes and other mononuclear cells that are attracted to the inflamed mucosa, causing chronic superficial gastritis and initiating a cytotoxic or an antigen-producing Th response. The infection is established within a few weeks after the primary exposure to H. pylori. After this initial colonization, many chemical, biochemical, and immunologic reactions take place that are of importance in the progress of the infection and the development of disease.

Ultrastructure of Helicobacter pylori in human gastric mucosa and H. pylori-infected human gastric mucosa using transmission electron microscopy and the high-pressure freezing-freeze substitution technique

BACKGROUND

Conventional ultrastructural analyses of Helicobacter pylori and H. pylori-infected gastric mucosa by transmission electron microscopy (TEM) have limitations because of structural artifacts introduced during fixation.

METHODS

We used high-pressure freezing (HPF) followed by freeze substitution for TEM to investigate the ultrastructure of H. pylori and H. pylori-infected gastric mucosa. For HPF-freeze substitution, human gastric biopsy specimens were placed in the HPF instrument at a pressure of approximately 2,000 atm at the temperature of liquid nitrogen. Specimens were then transferred to an instrument for freeze substitution. Specimens were first placed in acetone containing 2% OsO4 at -85 degrees C. The temperature was increased to -3 degrees C, followed by embedding in Quetol 812. Ultrathin sections were double-stained by uranium acetate/lead nitrate. HPF and conventionally prepared samples were examined by TEM.

RESULTS

The H. pylori envelope was clearly seen to consist of an outer membrane, periplasmic space, and plasma membrane. The periplasmic space was filled with electron-dense materials. A peptidoglycan layer was only occasionally visible. A thick, very fine filamentous or reticular fringe corresponding to the bacterial glycocalyx was seen surrounding the H. pylori cells. At the adhesion loci of H. pylori to gastric epithelial cells, H. pylori was connected to the epithelial cells by very fine, thickly arranged filaments or more closely, with a contact zone. The epithelial cells showed indentations or pedestals.

CONCLUSIONS

The well-developed, thick bacterial glycocalyx of H. pylori appears to strongly interact with external cellular components and may play an important role in the adhesion of H. pylori to epithelial cells.

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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.

Detection of H.pylori DNA in gastric epithelial cells by in situ hybridization

AIM

To investigate the presence of H.pylori DNA within gastric epithelial cells in patients with H.pylori infection and its possible carcinogenic mechanism.

METHODS

Total 112 patients, with pathologically confirmed chronic superficial gastritis, chronic atrophic gastritis, intestinal metaplasia, atypical hyperplasia or gastric cancer were studied. Among them, 28 were H.pylori negative and 84 H.pylori positive. H.pylori DNA in gastric epithelial cells was detected by GenPoint catalyzed signal amplification system for in situ hybridization.

RESULTS

In the H.pylori positive group, zero out of 24 chronic superficial gastritis (0.0%), four out of 25 precancerous changes (16.0%) and thirteen out of 35 gastric cancers (37.1%) showed H.pylori DNA in the nucleus of gastric epithelial cells, the positive rates of H.pylori DNA in the nucleus of gastric epithelial cells were progressively increased in chronic superficial gastritis, precancerous changes and gastric cancer groups (chi(2)=12.56, P=0.002); One out of 24 chronic superficial gastritis (4.2%), eleven out of 25 precancerous changes (44.0%) and thirteen out of 35 gastric cancers (37.1%) showed H.pylori DNA in the cytoplasm of gastric epithelial cells (chi(2)=10.86, P=0.004). In the H.pylori negative group, only one patient with gastric cancer was found H.pylori DNA in the nucleus of gastric epithelial cells; Only two patients, one patient with precancerous changes and another with gastric cancer, showed H.pylori DNA in the cytoplasm of gastric epithelial cells. Furthermore, H.pylori DNA must have been in the cytoplasm as long as it existed in the nucleus of gastric epithelial cells.

CONCLUSION

H.pylori DNA exists both in the nucleus and the cytoplasm of gastric epithelial cells in patients with H.pylori infections. The pathological progression from chronic superficial gastritis, precancerous changes to gastric cancer is associated with higher positive rates of H.pylori DNA presence in the nucleus of gastric epithelial cells.