N-acetylneuraminyllactose-binding fibrillar hemagglutinin of Campylobacter pylori: a putative colonization factor antigen

Recent progress on health effects and biosynthesis of two key sialylated human milk oligosaccharides, 3'-sialyllactose and 6'-sialyllactose

Human milk oligosaccharides (HMOs), the third major solid component in breast milk, are recognized as the first prebiotics for health benefits in infants. Sialylated HMOs are an important type of HMOs, accounting for approximately 13% of total HMOs. 3'-Sialyllactose (3'-SL) and 6'-sialyllactose (6'-SL) are two simplest sialylated HMOs. Both SLs display promising prebiotic effects, especially in promoting the proliferation of bifidobacteria and shaping the gut microbiota. SLs exhibit several health effects, including antiadhesive antimicrobial ability, antiviral activity, prevention of necrotizing enterocolitis, immunomodulatory activity, regulation of intestinal epithelial cell response, promotion of brain development, and cognition improvement. Both SLs have been approved as "Generally Recognized as Safe" by the American Food and Drug Administration and are commercially added to infant formula. The biosynthesis of SLs using enzymatic or microbial approaches has been widely studied. The enzymatic synthesis of SLs can be realized by two types of enzymes, sialidases with trans-sialidase activity and sialyltransferases. Microbial synthesis can be achieved by the multiple recombinant bacteria in one-pot reaction, which express the enzymes involved in SL synthesis pathways separately or in combination, or by metabolically engineered strains in a fermentation process. In this article, the physiological properties of 3'-SL and 6'-SL are summarized in detail and the biosynthesis of these SLs via enzymatic and microbial synthesis is comprehensively reviewed.

Sialic Acids as Receptors for Pathogens

Carbohydrates have long been known to mediate intracellular interactions, whether within one organism or between different organisms. Sialic acids (Sias) are carbohydrates that usually occupy the terminal positions in longer carbohydrate chains, which makes them common recognition targets mediating these interactions. In this review, we summarize the knowledge about animal disease-causing agents such as viruses, bacteria and protozoa (including the malaria parasite Plasmodium falciparum) in which Sias play a role in infection biology. While Sias may promote binding of, e.g., influenza viruses and SV40, they act as decoys for betacoronaviruses. The presence of two common forms of Sias, Neu5Ac and Neu5Gc, is species-specific, and in humans, the enzyme converting Neu5Ac to Neu5Gc (CMAH, CMP-Neu5Ac hydroxylase) is lost, most likely due to adaptation to pathogen regimes; we discuss the research about the influence of malaria on this trait. In addition, we present data suggesting the CMAH gene was probably present in the ancestor of animals, shedding light on its glycobiology. We predict that a better understanding of the role of Sias in disease vectors would lead to more effective clinical interventions.

Helicobacter pylori adhesins: HpaA a potential antigen in experimental vaccines for H. pylori

BACKGROUND

Helicobacter pylori is a gram-negative bacterium involved in many gastric pathologies such as ulcers and cancers. Although the treatment for this infection has existed for several years, the development of a vaccine is nevertheless necessary to reduce the severe forms of the disease. For more than three decades, many advances have been made particularly in the understanding of virulence factors as well as the pathogenesis of gastric diseases caused by H. pylori. Among these key virulence factors, specific antigens have been identified: Urease, Vacuolating cytotoxin A (VacA), Cytotoxin-associated gene A (CagA), Blood group antigen-binding adhesin (BabA), H. pylori adhesin A (HpaA), and others.

OBJECTIVES

This review will focus on H. pylori adhesins, in particular, on HpaA and on the current knowledge of H. pylori vaccines.

METHODS

All of the information included in this review was retrieved from published studies on H. pylori adhesins in H. pylori infections.

RESULTS

These proteins, used in their native or recombinant forms, induce protection against H. pylori in experimental animal models.

CONCLUSION

H. pylori adhesins are known to be promising candidate vaccines against H. pylori. Future research should be carried out on adhesins, in particular, on HpaA.

Identification of Functional Interactome of Gastric Cancer Cells with Helicobacter pylori Outer Membrane Protein HpaA by HPLC-MS/MS

HpaA as an outer membrane protein of Helicobacter pylori (H. pylori) plays a significant role in the adhesion to the human stomach, but the functional relation between HpaA and gastric epithelial cells is still not clear. To screen the interaction between HpaA and cellular proteins in gastric epithelial cells, the HpaA protein from H. pylori 26695 fused with a tag (6× His) was expressed and purified successfully, the secondary structure was estimated by the Circular Dichroism (CD) spectrum, and the purified recombinant protein was used to perform the pull-down assays with gastric cancer cell lines (AGS and SGC-7901) lysates, respectively. The pull-down proteins were identified by high-performance liquid chromatography tandem mass spectrometry system (HPLC-MS/MS). A total of 9 and 13 proteins related were analyzed from AGS and SGC-7901 cell lysates, respectively. ANXA2 was considered as putative HpaA functional partner discovered from lysates of both cell lines with high score and coverage. It is hypothesized that HpaA may be involved in the biological process of regulation of transcription and nucleic acid metabolism during the adhesion of H. pylori to human gastric epithelial cells, and HpaA-binding proteins also be used as targets for the development of antiadhesion drugs against H. pylori.

Phylogenetic Distribution, Ultrastructure, and Function of Bacterial Flagellar Sheaths

A number of Gram-negative bacteria have a membrane surrounding their flagella, referred to as the flagellar sheath, which is continuous with the outer membrane. The flagellar sheath was initially described in Vibrio metschnikovii in the early 1950s as an extension of the outer cell wall layer that completely surrounded the flagellar filament. Subsequent studies identified other bacteria that possess flagellar sheaths, most of which are restricted to a few genera of the phylum Proteobacteria. Biochemical analysis of the flagellar sheaths from a few bacterial species revealed the presence of lipopolysaccharide, phospholipids, and outer membrane proteins in the sheath. Some proteins localize preferentially to the flagellar sheath, indicating mechanisms exist for protein partitioning to the sheath. Recent cryo-electron tomography studies have yielded high resolution images of the flagellar sheath and other structures closely associated with the sheath, which has generated insights and new hypotheses for how the flagellar sheath is synthesized. Various functions have been proposed for the flagellar sheath, including preventing disassociation of the flagellin subunits in the presence of gastric acid, avoiding activation of the host innate immune response by flagellin, activating the host immune response, adherence to host cells, and protecting the bacterium from bacteriophages.

Carbohydrate-Dependent and Antimicrobial Peptide Defence Mechanisms Against Helicobacter pylori Infections

The human stomach is a harsh and fluctuating environment for bacteria with hazards such as gastric acid and flow through of gastric contents into the intestine. H. pylori gains admission to a stable niche with nutrient access from exudates when attached to the epithelial cells under the mucus layer, whereof adherence to glycolipids and other factors provides stable and intimate attachment. To reach this niche, H. pylori must overcome mucosal defence mechanisms including the continuously secreted mucus layer, which provides several layers of defence: (1) mucins in the mucus layer can bind H. pylori and transport it away from the gastric niche with the gastric emptying, (2) mucins can inhibit H. pylori growth, both via glycans that can have antibiotic like function and via an aggregation-dependent mechanism, (3) antimicrobial peptides (AMPs) have antimicrobial activity and are retained in a strategic position in the mucus layer and (4) underneath the mucus layer, the membrane-bound mucins provide a second barrier, and can function as releasable decoys. Many of these functions are dependent on H. pylori interactions with host glycan structures, and both the host glycosylation and concentration of antimicrobial peptides change with infection and inflammation, making these interactions dynamic. Here, we review our current understanding of mucin glycan and antimicrobial peptide-dependent host defence mechanisms against H. pylori infection.

Human Milk Oligosaccharides (HMOS): Structure, Function, and Enzyme-Catalyzed Synthesis

The important roles played by human milk oligosaccharides (HMOS), the third major component of human milk, in the health of breast-fed infants have been increasingly recognized, as the structures of more than 100 different HMOS have now been elucidated. Despite the recognition of the various functions of HMOS as prebiotics, antiadhesive antimicrobials, and immunomodulators, the roles and the applications of individual HMOS species are less clear. This is mainly due to the limited accessibility to large amounts of individual HMOS in their pure forms. Current advances in the development of enzymatic, chemoenzymatic, whole-cell, and living-cell systems allow for the production of a growing number of HMOS in increasing amounts. This effort will greatly facilitate the elucidation of the important roles of HMOS and allow exploration into the applications of HMOS both as individual compounds and as mixtures of defined structures with desired functions. The structures, functions, and enzyme-catalyzed synthesis of HMOS are briefly surveyed to provide a general picture about the current progress on these aspects. Future efforts should be devoted to elucidating the structures of more complex HMOS, synthesizing more complex HMOS including those with branched structures, and developing HMOS-based or HMOS-inspired prebiotics, additives, and therapeutics.

LptE binds to and alters the physical state of LPS to catalyze its assembly at the cell surface

The assembly of lipopolysaccharide (LPS) on the surface of Gram-negative bacterial cells is essential for their viability and is achieved by the seven-protein LPS transport (Lpt) pathway. The outer membrane (OM) lipoprotein LptE and the β-barrel membrane protein LptD form a complex that assembles LPS into the outer leaflet of the OM. We report a crystal structure of the Escherichia coli OM lipoprotein LptE at 2.34 Å. The structure reveals homology to eukaryotic LPS-binding proteins and allowed for the prediction of an LPS-binding site, which was confirmed by genetic and biophysical experiments. Specific point mutations at this site lead to defects in OM biogenesis. We show that wild-type LptE disrupts LPS-LPS interactions in vitro and that these mutations decrease the ability of LptE to disaggregate LPS. Transmission electron microscopic imaging shows that LptE can disrupt LPS aggregates even at substoichiometric concentrations. We propose a model in which LptE functions as an LPS transfer protein in the OM translocon by disaggregating LPS during transport to allow for its insertion into the OM.

Functional role and mechanisms of sialyllactose and other sialylated milk oligosaccharides

Human milk is a rich source of oligosaccharides. Acidic oligosaccharides, such as sialyllactose (SL), contain sialic acid (SA) residues. In human milk, approximately 73% of SA is bound to oligosaccharides, whereas only 3% is present in free form. Oligosaccharides are highly resistant to hydrolysis in the gastrointestinal tract. Only a small portion of the available oligosaccharides in breast milk is absorbed in the neonatal small intestine. SL and sialylated oligosaccharides are thought to have significant health benefits for the neonate, because of their roles in supporting resistance to pathogens, gut maturation, immune function, and cognitive development. The need for SA to allow proper development during the neonatal period is thought to exceed the endogenous synthesis. Therefore, these structures are important nutrients for the neonate. Based on the potential benefits, SL and sialylated oligosaccharides may be interesting components for application in infant nutrition. Once the hurdle of limited availability of these oligosaccharides has been overcome, their functionality can be explored in more detail, and supplementation of infant formula may become feasible.

Saccharomyces boulardii expresses neuraminidase activity selective for α2,3-linked sialic acid that decreases Helicobacter pylori adhesion to host cells

Helicobacter pylori is a major causative agent of gastritis and peptic ulcer disease and is an established risk factor for gastric malignancy. Antibiotic combination therapy can eradicate H. pylori. As these same regimens can evoke adverse effects and resistance, new alternative therapies or adjunctive treatments are needed. A probiotic approach may provide a novel strategy for H. pylori treatment. In the current study, two probiotic bacteria, Lactobacillus acidophilus and Lactobacillus reuteri, and a probiotic yeast, Saccharomyces boulardii, were evaluated for their ability to influence H. pylori viability, adherence to gastric and duodenal cells, as well as the effect of S. boulardii on cell surface expression of sialic acid. Our results indicate that S. boulardii contains neuraminidase activity selective for α(2-3)-linked sialic acid. This neuraminidase activity removes surface α(2-3)-linked sialic acid, the ligand for the sialic acid-binding H. pylori adhesin, which in turn, inhibits H. pylori adherence to duodenal epithelial cells.

Outer membrane biogenesis in Escherichia coli, Neisseria meningitidis, and Helicobacter pylori: paradigm deviations in H. pylori

The bacterial pathogen Helicobacter pylori is capable of colonizing the gastric mucosa of the human stomach using a variety of factors associated with or secreted from its outer membrane (OM). Lipopolysaccharide (LPS) and numerous OM proteins have been shown to be involved in adhesion and immune stimulation/evasion. Many of these factors are essential for colonization and/or pathogenesis in a variety of animal models. Despite this wide array of potential targets present on the bacterial surface, the ability of H. pylori to vary its OM profile limits the effectiveness of vaccines or therapeutics that target any single one of these components. However, it has become evident that the proteins comprising the complexes that transport the majority of these molecules to the OM are highly conserved and often essential. The field of membrane biogenesis has progressed remarkably in the last few years, and the possibility now exists for targeting the mechanisms by which β-barrel proteins, lipoproteins, and LPS are transported to the OM, resulting in loss of bacterial fitness and significant altering of membrane permeability. In this review, the OM transport machinery for LPS, lipoproteins, and outer membrane proteins (OMPs) are discussed. While the principal investigations of these transport mechanisms have been conducted in Escherichia coli and Neisseria meningitidis, here these systems will be presented in the genetic context of ε proteobacteria. Bioinformatic analysis reveals that minimalist genomes, such as that of Helicobacter pylori, offer insight into the smallest number of components required for these essential pathways to function. Interestingly, in the majority of ε proteobacteria, while the inner and OM associated apparatus of LPS, lipoprotein, and OMP transport pathways appear to all be intact, most of the components associated with the periplasmic compartment are either missing or are almost unrecognizable when compared to their E. coli counterparts. Eventual targeting of these pathways would have the net effect of severely limiting the delivery/transport of components to the OM and preventing the bacterium's ability to infect its human host.

Antiadhesion as a functional concept for prevention of pathogens: N-Phenylpropenoyl-L-amino acid amides as inhibitors of the Helicobacter pylori BabA outer membrane protein

SCOPE

Besides flavan-3-ols, a family of N-phenylpropenoyl-L-amino acids (NPAs) has been recently identified as polyphenol/amino acid conjugates in the seeds of Theobroma cacao as well as in a variety of herbal drugs. NPAs were shown to exhibit antiadhesive activities against Helicobacter pylori.

METHODS AND RESULTS

For structure/activity relationship 24 homologous NPAs (2 mM) were investigated in a flow cytometric assay on potential antiadhesive effects against H. pylori adhesion to human gastric AGS cells. Dihydroxylation of the aromatic molecule part was shown to be necessary for activity; methoxylation decreases activity. High polarity of the amino acid is a prerequisite for activity. The model compound N-(E)-caffeoyl-L-glutamic acid 11 exerted a concentration-dependent inhibition of bacterial adhesion with saturation at 30% inhibition level. The antiadhesive effect was additionally confirmed by in situ adhesion assay on intact human gastric tissue. NPAs exhibited no cytotoxicity. Using immobilized ligands interaction 11 with bacterial adhesin BabA was demonstrated. RT-PCR indicated that the inhibition of BabA is not correlated with subsequent feed back regulations to express more adhesins or virulence factors (vacA, cagA, cagL, cagα, fucT, ureI, ureA, OMPs). The interaction of bacterial adhesins with the respective ligands does not automatically lead to a subsequent signal transduction towards induction of virulence processes.

CONCLUSION

The nutritional use of NPA-containing food may justify a positive antiadhesive effect against the recurrence of H. pylori infections.

Peptides from Pisum sativum L. enzymatic protein digest with anti-adhesive activity against Helicobacter pylori: structure-activity and inhibitory activity against BabA, SabA, HpaA and a fibronectin-binding adhesin

SCOPE

Identification of anti-adhesive peptides against Helicobacter pylori obtained by enzymatic hydrolysis of seed proteins from Pisum sativum L. (Fabaceae).

METHODS AND RESULTS

Bioassay-guided fractionation of protein tryptic digest by ultrafiltration, size exclusion chromatography (SEC) and reversed phase chromatography (RPC) were used. Identification of bioactive peptides was achieved by MALDI-TOF-MS. Adhesion of H. pylori was monitored by two different assays, using a quantitative in vitro assay on human AGS cells with evaluation of bacterial binding by flow cytometry, beside a semi-quantitative in situ adhesion assay using FITC-labelled H. pylori on human stomach tissue sections. From two highly active fractions (F3, F3.3) two anti-adhesive peptides (S3, S5) were identified. Neither F3 nor S3 or S5 had any cytotoxic effect against H. pylori. By hemagglutination assay and semiquantitative dot blot overlay assay with immobilized ligands it was shown that F3 interacts specifically with H. pylori adhesins BabA, SabA, HpaA and a fibronectin-binding adhesin, while S3 and S5 inhibit only BabA. It was demonstrated that BabA, usually interacting with carbohydrate motifs such as fucosylated blood group antigens, interacts with the peptide moieties.

CONCLUSION

Bioactive peptides from pea protein could be applied as functional ingredients for protecting infants and children against infections such as H. pylori.

The antibody titers to Helicobacter pylori in 7 - 12 year old iron deficiency anemic children, in Ilam

BACKGROUND

It has recently been revealed that H. pylori infection is one the most important causes of anemia inhibiting iron uptake. The current study was designed to evaluate the correlation between the iron deficiency anemia and IgG to H. pylori in anemic children.

METHODS

In this analytical study, 100 anemic children were analyzed using total Iron, Ferritin, TIBC and H. pylori IgG assay. Data were collected using a questionnaire including parameters of age, blood group, infancy nutrition, iron consumption, fatigue, weakness, height, weight, gastrointestinal infectious, parasitic and blood diseases, parent literacy, income, inhabitation, etc. Data were analyzed using Multivariate Regression Analysis Models, Pearson Correlation- test and Kolmogrov Smirnov.

RESULTS

The most prevalent blood group detected in the study sample was group O (62%); 79% were breastfed, 9% were bottle- fed, 12% were both breastfed and bottle- fed. The history of gastrointestinal disorders was mentioned amongst 91% of the patients' family members. A significant relationship was observed between the iron level with serum, ferritin, level of TIBC and elevated level of IgG titer to H. pylori (p < 0.001). There was a significant association between the shared dishes, GI disorders, fatigue and weakness and level of TIBC, ferritin, Iron and IgG (p < 0.001).

CONCLUSIONS

The significant relationship between the iron level, IgG titer and H. pylori infection rate can be referred to as important factors influencing the anemia rate. Therefore, H. pylori IgG test can be checked for anemia together with the other routine tests.

Helicobacter pylori binding to new glycans based on N-acetyllactosamine

Previously we reported binding of Helicobacter pylori to various nonacid and sialylated neolacto carbohydrate structures using a wide range of natural and chemically modified sequences. A novel nonsialylated neolacto-based binding epitope, GlcNAc beta 3Gal beta 4GlcNAc, and analogous structures carrying terminal GalNAc beta 3, GalNAc alpha 3, or Gal alpha 3 showed the binding activity (Miller-Podraza H, Lanne B, Angström J, Teneberg S, Abul-Milh M, Jovall P-A, Karlsson H, Karlsson K-A. 2005. Novel binding epitope for Helicobacter pylori found in neolacto carbohydrate chains. J Biol Chem. 280:19695-19703). The present work reports two other H. pylori-binding nonsialylated neolacto-based structures, GlcA beta 3Gal beta 4GlcNAc beta 3-R and Glc beta 3Gal beta 4GlcNAc beta 3-R, and two amide derivatives (N-methyl and N-ethyl) of GlcA beta 3Gal beta 4GlcNAc beta 3-R which were bound by H. pylori. The latter structures turned out to be more effective as H. pylori binders than the parent saccharide. New reducing-end variants of the neolacto epitope including species containing N-acetyllactosamine linked beta 6 to GlcNAc or Gal with similarity to branched polylactosamines and mucins were prepared and tested. The results extend our previous findings on binding specificities of H. pylori and show that this pathogen is able to interact with an array of N-acetyllactosamine/neolacto structures, which may be of importance for the in vivo interaction of the bacterium with human cells. The information gained in this work may also be of value for rational design of anti-H. pylori drugs.

Increasing evidence of the role of Helicobacter pylori SabA in the pathogenesis of gastroduodenal disease

Although infection with Helicobacter pylori always results in chronic active gastritis, only a fraction of those infected develop severe clinical disease. In addition, certain populations with high incidences of H. pylori infection, such as those in East Asian countries, have high incidences of gastric cancer, while other highly infected populations, such as those in Africa and South Asia, do not. This phenomenon might be partially explained by differences in the genotypes of H. pylori; however, currently no definite H. pylori factors can clearly explain it. Recently, the importance of sialic acid binding adhesin (SabA), a novel outer membrane protein in gastroduodenal pathogenesis, has become increasingly apparent. Binding of blood group antigen binding adhesin (BabA) to Lewis b antigen and related fucosylated ABO blood group antigens is probably important in the initial stage of infection. However, when host inflammation increases, expression of sialyl-Lewis x increases, and H. pylori is likely to adhere to the gastric mucosa with SabA. Many of the genes encoding outer membrane proteins undergo phase variation such that not all strains will produce functional proteins, and SabA expression is frequently switched "on" or "off", suggesting that SabA expression can rapidly respond to changing conditions in the stomach or in different regions of the stomach. SabA production is indeed reported to be associated with severe intestinal metaplasia, gastric atrophy, and the development of gastric cancer in both developed and developing countries, confirming the importance of investigating SabA in developing countries.

The Multiple Carbohydrate Binding Specificities of Helicobacter pylori

Persistent colonization of the human stomach by Helicobacter pylori is a risk factor for the development of peptic ulcer disease and gastric cancer. Adhesion of microbes to the target tissue is an important determinant for successful initiation, establishment and maintenance of infection, and a variety of different candidate carbohydrate receptors for H. pylori have been identified. Here the different the binding specifities, and their potential role in adhesion to human gastric epithelium are described. Finally, recent findings on the roles of sialic acid binding SabA adhesin in interactions with human neutrophils and erythrocytes are discussed.

SabA is the H. pylori hemagglutinin and is polymorphic in binding to sialylated glycans

Adherence of Helicobacter pylori to inflamed gastric mucosa is dependent on the sialic acid–binding adhesin (SabA) and cognate sialylated/fucosylated glycans on the host cell surface. By in situ hybridization, H. pylori bacteria were observed in close association with erythrocytes in capillaries and post-capillary venules of the lamina propria of gastric mucosa in both infected humans and Rhesus monkeys. In vivo adherence of H. pylori to erythrocytes may require molecular mechanisms similar to the sialic acid–dependent in vitro agglutination of erythrocytes (i.e., sialic acid–dependent hemagglutination). In this context, the SabA adhesin was identified as the sialic acid–dependent hemagglutinin based on sialidase-sensitive hemagglutination, binding assays with sialylated glycoconjugates, and analysis of a series of isogenic sabA deletion mutants. The topographic presentation of binding sites for SabA on the erythrocyte membrane was mapped to gangliosides with extended core chains. However, receptor mapping revealed that the NeuAcα2–3Gal-disaccharide constitutes the minimal sialylated binding epitope required for SabA binding. Furthermore, clinical isolates demonstrated polymorphism in sialyl binding and complementation analysis of sabA mutants demonstrated that polymorphism in sialyl binding is an inherent property of the SabA protein itself. Gastric inflammation is associated with periodic changes in the composition of mucosal sialylation patterns. We suggest that dynamic adaptation in sialyl-binding properties during persistent infection specializes H. pylori both for individual variation in mucosal glycosylation and tropism for local areas of inflamed and/or dysplastic tissue.

Helicobacter pylori infections are very common worldwide and cause chronic inflammation in the stomach (gastritis), which may progress to peptic ulcer disease and stomach cancer. In the gastric epithelium, H. pylori infections induce expression of inflammation-associated “sialylated” carbohydrates. The ability to bind to the glycosylated epithelial cells is considered to be essential for H. pylori to cause persistent infection and disease. Here the authors show that during established infection, H. pylori also binds to red blood cells in gastric mucosal blood vessels in both infected humans and Rhesus monkeys. The authors found that “sialic acid–binding adhesin” (SabA), is the bacterial surface protein that mediates binding of H. pylori to red blood cells. Furthermore, they show that clinical H. pylori isolates demonstrate “polymorphism” in their abilities to bind various sialylated carbohydrates, and that the variation in binding properties depends on the sialic acid–binding adhesin protein itself. This variability may adapt the binding properties of H. pylori both to individual hosts and the changing epithelial glycosylation patterns during chronic inflammation. Continuous adaptation to inflamed tissue during persistent infections is probably a general feature of microbial pathogens, although their binding properties have not yet been explored in detail.

Oral immunization with HpaA affords therapeutic protective immunity against H. pylori that is reflected by specific mucosal immune responses

In the present study, we evaluated the capacity of Helicobacter pylori adhesin A (HpaA), a H. pylori specific colonization factor, to induce therapeutic protection against H. pylori infection in mice. We found that oral immunization of H. pylori infected mice with HpaA induced protection, i.e. significant reduction in bacterial load in the stomach. This was even more pronounced when a combination of HpaA and urease was used. The protection was strongly related to specific mucosal CD4+ T cell responses with a Th1 profile as well as to mucosal IgA responses locally in the stomach. These findings suggest that HpaA is a promising vaccine candidate antigen for use in a therapeutic vaccine against H. pylori.

HpaA is essential for Helicobacter pylori colonization in mice

Infection with the human gastric pathogen Helicobacter pylori can give rise to chronic gastritis, peptic ulcer, and gastric cancer. All H. pylori strains express the surface-localized protein HpaA, a promising candidate for a vaccine against H. pylori infection. To study the physiological importance of HpaA, a mutation of the hpaA gene was introduced into a mouse-adapted H. pylori strain. To justify that the interruption of the hpaA gene did not cause any polar effects of downstream genes or was associated with a second site mutation, the protein expression patterns of the mutant and wild-type strains were characterized by two different proteomic approaches. Two-dimensional differential in-gel electrophoresis analysis of whole-cell extracts and subcellular fractionation combined with nano-liquid chromatography-Fourier transform ion cyclotron resonance mass spectrometry for outer membrane protein profiling revealed only minor differences in the protein profile between the mutant and the wild-type strains. Therefore, the mutant strain was tested for its colonizing ability in a well-established mouse model. While inoculation with the wild-type strain resulted in heavily H. pylori-infected mice, the HpaA mutant strain was not able to establish colonization. Thus, by combining proteomic analysis and in vivo studies, we conclude that HpaA is essential for the colonization of H. pylori in mice.

Characterization of a sialidase (neuraminidase) isolated fromClostridium chauvoei (Jakari strain)

A sialidase from Clostridium chauvoei (Jakari strain), an indigenous bacterial strain that causes blackleg in Nigerian cattle and other ruminants was isolated and partially purified by chromatography on DEAE cellulose, hydroxyapatite and phenyl agarose columns. The enzyme migrated as a 65-kDa protein after electrophoresis on sodium dodecyl sulphate polyacrylamide gels. It was optimally active at pH 4.5 and 40 degrees C with an activation energy (Ea) of 13.40 kJ mol(-1). It had Km and Vmax values of 170 microM and 200 micromole h(-1) mg(-1) respectively with fetuin as substrate. When sialyllactose (Neu5Ac2,3 lactose) was used as substrate the Km and Vmax values were 8 microM and 5 micromoles min(-1) mg(-1) respectively. The Clostridium chauvoei sialidase cleaved sialic acids from RBC ghosts of sheep, horse, goat, cattle, pig and mice as well as mouse brain cells, albeit at different rates. The enzyme was activated by Ca2+ and Mg2+ and inhibited by the group-specific reagents diethylpyrocarbonate (DEP) and N-ethylmalemide (NEM). The sialidase inhibitors, 2,3 didehydroneuraminic acid (Neu5Ac2,3en) and paranitrophenyl oxamic acid (pNPO) inhibited the enzyme competitively with Ki values of 40 and 30 microM respectively.

Lectin histochemistry of the gastric mucosa in normal and Helicobacter pylori infected guinea-pigs

Helicobacter pylori attaches via lectins, carbohydrate binding proteins, to the carbohydrate residues of gastric mucins. Guinea-pigs are a suitable model for a H. pylori infection and thus the carbohydrate composition of normal and H. pylori infected gastric mucosa was investigated by lectin histochemistry. The stomach of all infected animals showed signs of an active chronic gastritis in their mucosa, whereas no inflammation was present in the control animals. The corpus-fundus regions of the controls showed heterogeneous WGA, SNA-I, UEA-I and HPA binding in almost all parts of the gastric glands. While these lectins labelled the superficial mucous cells and chief cells heterogeneously, the staining of the parietal cells was limited to WGA and PHA-L. Mucous neck cells reacted heterogeneously with UEA-I, HPA, WGA and PHA-L. In the antrum, the superficial mucous cells and glands were stained by WGA, UEA-I, HPA, SNA-I or PHA-L. WGA, UEA-I, SNA-I and HPA labelled the surface lining cells strongly. The mucoid glands reacted heterogeneously with WGA, UEA-I, HPA, SNA-I and PHA-L. In both regions, the H. pylori infected animals showed similar lectin binding pattern as the controls. No significant differences in the lectin binding pattern and thus in the carbohydrate composition between normal and H. pylori infected mucosa could be detected, hence H. pylori does not induce any changes in the glycosylation of the mucosa of the guinea-pig. This unaltered glycosylation is of particular relevance for the sialic acid binding lectin SNA-I as H. pylori uses sialic acid binding adhesin for its attachment to the mucosa. As sialic acid binding sites are already expressed in the normal mucosa H. pylori can immediately attach via its sialic acid binding adhesin to the mucosa making the guinea-pig particularly useful as a model organism.

Restriction fragment length polymorphism of adhesin gene hpaA from different Helicobacter pylori strains of Chongqing, China

AIM: To assess the variability of adhesin gene hpaA between different Helicobacter pylori (H pylori) strains with PCR-restriction fragment length polymorphism (RFLP).

METHODS: Twelve different H pylori strains were chosen to amplify the 710-bp segments of gene hpaA. These strains were NCTC11637, SS1; Chongqing clinical isolates CCS9801, CCS9802, CCS9803, CCS9806, CCS9809, CCS9810, CCS9813, which were gained from patients of gastritis; Mongolia gerbil adapted H pylori strains (abbreviation MG), which were gained from the following steps: gastric mucosal specimens of Mongolia gerbils infected by clinical isolate CCS9803 were cultured and detected, the positive H pylori strains were named as the first generation of Mongolia gerbil adapted H pylori strains (abbreviation MG1) and then were subcultured with healthy Mongolia gerbil to generate MG₂, in turn to gain the ninth generation (abbreviation MG9). All hpaA segments, obtained from 12 different H pylori strains, were digested by HhaI and HaeIII individually and analyzed by agarose gel electrophoresis.

RESULTS: In all 12 strains, the 710-bp PCR products were successfully amplified and products were cloned to pMD18-T vector respectively, then the recombinant plasmids were digested simultaneously with NcoI and XhoI to recover the small fragments. The objective fragments from 12 different H pylori strains digested with Hae III could be seen as 4 types of bands and 5 types with Hha I. According to the hpaA RFLP patterns, the 12 H pylori strains could be divided into 5 groups: group I, NCTC11637 and SS1; group II, CCS9809, which RFLP type digested with HaeIII was the same as strains of group I, but HhaI RFLP showed difference compared with the other groups; group III, CCS9810; group IV, CCS9803; group V: CCS9801, CCS9802, CCS9806, CCS9813, MG1, MG3 and MG9. The sequence data of 12 hpaA segments were analyzed by DNAsis software and it was observed that: (1) The homologies of base pair and amino acid sequence between strains NCTC11637, SS1, CCS9809 were 99.6% and 98.9%, respectively; (2) The homology of base pair and amino acid sequence between CCS9803 and CCS9810 was 97.7% and 99.1%; (3) That of the rest strains, CCS9801, CCS9802, CCS9806, CCS9813, MG1, MG3, MG9 reached 99.4% and 98.4%; (4) The base pair homologies between all hpaA fragments of different sources were higher than 94.6%, therefore the correspondence of deduced amino acid sequence was higher than 96.8% between each other.

CONCLUSION: The gene hpaA from different H pylori strains revealed variation, and this might provide an effective method for molecular epidemiological survey of H pylori.

Novel Binding Epitope for Helicobacter pylori Found in Neolacto Carbohydrate Chains

Helicobacter pylori is a bacterium that colonizes the stomach of a majority of the global human population causing common gastric diseases like ulcers and cancer. It has an unusually complex pattern of binding to various host glycoconjugates including interaction with sialylated, sulfated, and fucosylated sequences. The present study describes an additional binding epitope comprising the neolacto internal sequence of GlcNAcbeta3-Galbeta4GlcNAcbeta. The binding was detected on TLC plates as an interaction with a seven-sugar ganglioside of rabbit thymus. The glycolipid was purified and characterized as Neu5Gcalpha3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3-Galbeta4Glcbeta1Cer with less than 10% of the fraction carrying a repeated lacto (type-1) core chain, Galbeta3Glc-NAcbeta3Galbeta3GlcNAcbeta. After stepwise chemical and enzymatic degradation and structural analysis of products the strongest binder was found to be the pentaglycosylceramide GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1-Cer, whereas the hexa- and tetraglycosylceramides were less active, and the trihexosylceramide was inactive. Further studies revealed that the terminal GlcNAcbeta of the pentaglycosylceramide may be exchanged for either GalNAcbeta3, GalNAcalpha3, or Galalpha3 without loss of the activity. Calculated minimum energy conformers of these four isoreceptors show a substantial topographical similarity suggesting that this binding is a result of a molecular mimicry. Although the glycoconjugate composition of human gastric epithelial cells is not known in detail it is proposed that repeating N-acetyllactosamine units of glycoconjugates may serve as bacterial attachment sites in the stomach.

Characteristics of a clinical isolate of urease-negative Helicobacter pylori and its ability to induce gastric ulcers in Mongolian gerbils

BACKGROUND

We clinically obtained urease-negative mutant strains of Helicobacter pylori. The goal of this study was to investigate the ability of the urease-negative strain to colonize and subsequently damage the gastric mucosa in Mongolian gerbils. In addition, the genes encoding the urease production in the test strain were analyzed, and other genes encoding the virulence factors, cytotoxin-associated protein and vacuolating-cytotoxin were evaluated.

MATERIALS AND METHODS

The character of urease-negative isolates of H. pylori was defined. The identification of H. pylori was confirmed by polymerase chain reaction (PCR). The H. pylori isolate was transfected into Mongolian gerbils as previously described, which were followed up to 42 weeks, and the changes in their gastric mucosa were examined histologically.

RESULTS AND CONCLUSION

Fifteen Mongolian gerbils orally infected with 10(7) colony forming units of urease-negative H. pylori were killed at 4, 12, 24, 36 and 42 weeks (n = 3) after infection. Culture medium without urease-negative H. pylori was given to the Mongolian gerbils as control. H. pylori continued to exist in the subject's stomach and gastric ulceration was observed and compared with the control. Clinically obtained urease-negative H. pylori continued to exist for at least 42 weeks in the subject's stomach and it induced gastric ulcers. These data demonstrated that the urease in H. pylori was not a necessary factor in the formation of gastric ulcers in the Mongolian gerbil model.

In vivo expression of the 25-kDa laminin-binding protein ofHelicobacter pylori

The gastroduodenal pathogen Helicobacter pylori has been shown to inhibit the interaction between the extracellular matrix protein laminin and its receptor on gastric epithelial cells, potentially contributing to a loss of mucosal integrity. As a 25-kDa outer membrane protein of H. pylori in association with the bacterial lipopolysaccharides (LPS) mediates attachment to laminin, the aim of this study was to determine whether the 25-kDa protein is produced by H. pylori in infected hosts. We examined the immune response to the 25-kDa laminin binding protein in 12 paediatric patients; samples from a H. pylori-negative healthy adult were used as controls. In immunoblotting, antibodies to a 25-kDa protein were found in the serum and saliva of H. pylori-positive individuals only, and using the positive sera and saliva, laminin binding to the 25-kDa protein was inhibited. Thus, the 25-kDa laminin-binding protein is produced by H. pylori in infected hosts.

Identification and characterization of binding properties of Helicobacter pylori by glycoconjugate arrays

The microaerophilic bacterium Helicobacter pylori is well established for its role in development of different gastric diseases. Bacterial adhesins and corresponding binding sites on the epithelial surface allow H. pylori to colonize the gastric tissue. In this investigation, the adhesion of H. pylori to dot blot arrays of natural glycoproteins and neoglycoproteins was studied. Adhesion was detected by overlay with fluorescence-labeled bacteria on immobilized (neo)glycoproteins. The results confirmed the interaction between the adhesin BabA and the H-1-, Lewis b-, and related fucose-containing antigens. In addition, H. pylori bound to terminal alpha2-3-linked sialic acids as previously described. The use of a sabA mutant and sialidase treatment of glycoconjugate arrays showed that the adherence of H. pylori to laminin is mediated by the sialic acid-binding adhesin, SabA. The adhesion to salivary mucin MUC5B is mainly associated with the BabA adhesin and to a lesser extent with the SabA adhesin. This agrees with reports, that MUC5B carries both fucosylated blood group antigens and alpha2-3-linked sialic acids. The adhesion of H. pylori to fibronectin and lactoferrin persisted in the babA/sabA double mutant. Because binding to these molecules was abolished by denaturation rather than by deglycosylation, it was suggested to depend on the recognition of unknown receptor moieties by an additional unknown bacterial surface component. The results demonstrate that the bacterial overlay method on glycoconjugate arrays is a useful tool for exploration and the characterization of unknown adhesin specificities of H. pylori and other bacteria.

Interaction of Helicobacter pylori with sialylated carbohydrates: the dependence on different parts of the binding trisaccharide Neu5Acα3Galβ4GlcNAc

We have recently shown that binding of Helicobacter pylori to sialylated carbohydrates is dependent on the presence of the carboxyl group and the glycerol chain of Neu5Ac. In this work we investigated the importance of GlcNAc in the binding trisaccharide Neu5Acalpha3Galbeta4GlcNAc and the role of the N-acetamido groups of both Neu5Ac and GlcNAc. An important part of the project was epitope dissection, that is chemical derivatizations of the active carbohydrate followed by binding studies. In addition we used a panel of various unmodified carbohydrate structures in the form of free oligosaccharides or glycolipids. These were tested for binding by hemagglutination inhibition assay, TLC overlay tests, and a new quantitative approach using radiolabeled neoglycoproteins. The studies showed that the N-acetamido group of Neu5Ac is important for binding by H. pylori, whereas the same group of GlcNAc is not. In addition, Fuc attached to GlcNAc, as tested with sialyl-Lewis x, did not affect the binding. Free Neu5Ac was inactive as inhibitor, and Neu5Acalpha3Gal turned out to be active. The binding preference for neolacto structures was confirmed, although one strain also was inhibited by lacto chains. The combined results revealed that an intact Neu5Ac is crucial for the interactions with H. pylori. Parts of Gal also seem to be necessary, whereas the role of the GlcNAc is secondary. GlcNAc does influence binding, however, primarily serving as a guiding carrier for the binding epitope rather than being a part of the binding structure.

Exfoliation of Helicobacter pylori from Gastric Mucin by Glycopolypeptides from Buttermilk

In the human stomach, Helicobacter pylori, an ulcer pathogenic bacterium, colonizes the gastric mucosal layer primarily. The ability of glycopolypeptides (GPP) prepared from buttermilk to exfoliate H. pylori bound to gastric mucin was investigated. The GPP were prepared from buttermilk by digestion with trypsin, papain, pancreatin, bromelain, or pepsin. Helicobacter pylori ATCC 43504T and 43579 adhered more strongly to all of the GPP tested than to whole buttermilk, the soluble fraction of buttermilk, gastric mucin prepared from mouse stomach, or commercial pig gastric mucin. The GPP digested with trypsin, papain, or pancreatin were significantly more adherent. When the GPP concentration was 10 mg/mL, bound H. pylori ATCC 43504T, 43579, and 5 clinical isolates were exfoliated markedly from immobilized porcine gastric mucin following treatment with GPP digested with trypsin or pancreatin. This ability of GPP did not correlate with sialic acid content, indicating that sialic acid content is not important in the exfoliation of this microorganism. Such an ability may depend on the structure or number of sugar chains, or the position of sialic acid. We conclude that GPP promote the exfoliation of H. pylori bound to gastric mucin and prevent the de novo adherence of this microorganism. As such, GPP are a promising food material for preventing H. pylori infection.

Identification of a 19.3-kDa protein in MRHA-positive Edwardsiella tarda: putative fimbrial major subunit

The hemagglutinating properties of Edwardsiella tarda isolated from fish were investigated. Hemagglutination of E. tarda was not inhibited by D-mannose but was strongly inhibited by fetuin and N-acetylneuraminic acid. Extraction of hemagglutinating activity from bacterial cells was achieved using n-octyl-beta-D-thioglucoside (NOTG), and the NOTG extracts were fractionated by sucrose density gradient ultracentrifugation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the fractions revealed that a 19.3-kDa protein band appeared in the fractions exhibiting highest hemagglutinating activity. In an immunoblot analysis of NOTG extracts from 18 strains of E. tarda, the 19.3-kDa protein was detected only in the extracts possessing hemagglutinating activity. The predicted amino acid sequence of a 534-bp gene encoding the 19.3-kDa protein was identical to fimbrial subunit (FimA) of E. tarda by FASTA homology search. These findings suggest that fimbriae are implicated in the hemagglutination of E. tarda.

Treatment of Helicobacter pylori infection using a novel antiadhesion compound (3'sialyllactose sodium salt). A double blind, placebo-controlled clinical study

BACKGROUND AND AIM

3' sialyllactose sodium salt (3'SL) is an oligosaccharide that occurs naturally in human and bovine milk. It can inhibit the adhesion of H. pylori to human epithelial cells in vitro. The aim of this study was to test whether this oligosaccharide can suppress or cure H. pylori colonization in vivo and to determine its safety in humans.

METHODS

Seventy-one consecutive dyspeptic patients with H. pylori infection documented by histology and 13C-Urea Breath Test (UBT) were initially recruited to this study. Patients with UBT values <15 were excluded, thus reducing the enrollment to 65 patients. They were given two different dosages of 3'SL (10 g or 20 g/day) in three daily administrations before meals or placebo for 4 weeks, according to a randomised double-blind protocol. A standardized 13C-UBT (using 100 mg of 13C labelled urea) was repeated in all patients at fixed intervals during treatment (at the end of weeks 1, 2 and 4) and 4 weeks after treatment withdrawal. Patients compliance and side-effects were evaluated at each weekly visit.

RESULTS

Five patients were excluded from the PP analysis due to violation of the protocol (noncompliance, lost to follow-up), whereas 61 patients completed correctly the study: 17 received 3'SL 10 g/day, 22 were treated with 3'SL 20 g/day and 21 were given placebo. The three treatment groups did not significantly differ in demographic or clinical patient characteristics. No serious adverse events were observed during therapy in any of the three groups. No patients became UBT negative (<4) during or after treatment but UBT values decreased significantly during the study period in both treatment groups and placebo.

CONCLUSIONS

Antiadhesive therapy was safe and well tolerated but did not suppress or cure H. pylori colonization in humans. The observed decrease in UBT values could be explained by a regression towards the mean effect.

Antigenic properties of HpaA and Omp18, two outer membrane proteins of Helicobacter pylori

Outer membrane proteins (OMPs) are incorporated into the outer plasma membrane of Helicobacter pylori and are important for, e.g., ion transport, adherence, structural and osmotic stability, and bacterial virulence but may also be antigenic due to their surface exposure. Previous proteome-based approaches with H. pylori lysates determined a strong serological reaction towards two H. pylori OMPs, HpaA (TIGR HP0797) and Omp18 (TIGR HP1125). PCR was used to detect DNA encoding the two proteins, and a positive signal was found in all H. pylori strains tested. Proteins were cloned and expressed in the human kidney cell line HK293 with the QiaExpressionist system with a C-terminal His tag. Only sera from infected persons showed a positive reaction with the recombinant proteins. Recombinant HpaA (rHpaA) and rOmp18 were incubated with human peripheral blood mononuclear cells and induced secretion of interleukin-12 (IL-12) and IL-10 from these cells. To determine the effect on antigen-presenting cells, human blood monocytic and dendritic cells (DCs) were isolated by magnetic cell separation. rOmp18 and rHpaA strongly stimulated major histocompatibility class II and CD83 expression 7- to 10-fold on isolated DCs. rHpaA and rOmp18 failed to stimulate IL-8 secretion from monocytes but increased secretion of IL-12 and IL-10 from DCs significantly. In summary, HpaA and Omp18 are recognized by human dendritic cells and induce their maturation as well as antigen presentation. HpaA and Omp18 of H. pylori thereby appear to have a specific antigenic potential in humans.

"Multivalent" saccharides: development of new approaches for inhibiting the effects of glycosphingolipid-binding pathogens

A number of diseases are initiated by the adherence of viruses, bacteria, or bacterial toxins to cell surface carbohydrates, a number of which are components of glycosphingolipids (GSLs). Studies of the binding of lectins indicated that many adhered weakly to monomeric carbohydrate ligands. The seminal observation that lectins adhered more strongly to a ligand with multiple carbohydrate binding sites initiated a plethora of studies designed to identify effective "multivalent" carbohydrate ligands for pathogens expressing multiple carbohydrate-binding sites. In addition to more completely defining ligand specificity of the carbohydrate-binding pathogen, identification of "multivalent" carbohydrate ligands has led to studies of their efficacy as pathogen inhibitors. This commentary focuses on pathogens that recognize the carbohydrate portion of GSLs. Because many GSL-binding pathogens have been shown to bind "multivalent" saccharides, approaches for identifying and preparing them as well as methods for characterizing their effectiveness as ligands are reviewed. Also discussed are areas of promise that should be investigated and pitfalls that might be encountered in the development of "multivalent" saccharides as pharmacologic agents.

Recombinant HpaA purified from Escherichia coli has biological properties similar to those of native Helicobacter pylori HpaA

The aim of this study was to recombinantly produce and purify Helicobacter pylori adhesin A (HpaA) from Escherichia coli and compare it to purified native H. pylori HpaA, for potential use as a vaccine antigen. The hpaA gene was cloned from H. pylori, transferred to two different expression vectors, and transformed into E. coli. Expression of rHpaA was analysed by immunoblot, inhibition ELISA, and semi-quantitative dot-blot. Using affinity chromatography, rHpaA was purified from E. coli and native HpaA from H. pylori. The binding of both purified proteins to sialic acid was analysed and antibody titres to native and rHpaA were compared after intraperitoneal immunisation of C57/Bl mice. The rHpaA protein was highly expressed in E. coli from both vectors. Purified recombinant and native HpaA bound similarly to fetuin but also to the non-sialylated asialofetuin. Both native HpaA and rHpaA induced comparable amounts of specific antibodies in serum after immunisation and they were identical in double immunodiffusion. In conclusion, rHpaA was successfully produced in E. coli. Purified rHpaA showed biological properties similar to those of native HpaA isolated from H. pylori and may therefore be further used as an antigen in the development of a vaccine against H. pylori infection.

Helicobacter pylori interactions with host serum and extracellular matrix proteins: potential role in the infectious process

Helicobacter pylori, a gram-negative spiral-shaped bacterium, specifically colonizes the stomachs of humans. Once established in this harsh ecological niche, it remains there virtually for the entire life of the host. To date, numerous virulence factors responsible for gastric colonization, survival, and tissue damage have been described for this bacterium. Nevertheless, a critical feature of H. pylori is its ability to establish a long-lasting infection. In fact, although good humoral (against many bacterial proteins) and cellular responses are observed, most infected persons are unable to eradicate the infection. A large body of evidence has shown that the interaction between H. pylori and the host is very complex. In addition to the effect of virulence factors on colonization and persistence, binding of specialized bacterial proteins, known as receptins, to certain host molecules (ligands) could explain the success of H. pylori as a chronically persisting pathogen. Some of the reported interactions are of high affinity, as revealed by their calculated dissociation constant. This review examines the binding of host proteins (serum and extracellular matrix proteins) to H. pylori and considers the significance of these interactions in the infectious process. A more thorough understanding of the kinetics of these receptin interactions could provide a new approach to preventing deeper tissue invasion in H. pylori infections and could represent an alternative to antibiotic treatment.

Role of the alpAB proteins and lipopolysaccharide in adhesion of Helicobacter pylori to human gastric tissue

The attachment of the bacterial pathogen Helicobacter pylori (H. pylori) to gastric epithelial cells is commonly believed to be required for an efficient and persistent colonization of the human stomach as well as for host cell trans-membrane signaling. In the past, several putative adhesins were postulated, including the outer membrane proteins AlpAB and the bacterial lipopolysaccharide (LPS) presenting oligomeric Lewis x (Le(x)) sugar components. We investigated the AlpAB-mediated and the Le(x)-dependent binding by knockout mutagenesis in one distinct strain, H. pylori P1. We show here that the mutagenesis of either alpA and/or alpB dramatically reduced the adherence of H. pylori P1 to a given gastric biopsy section. None of these mutations influenced the surface exposure of the Le(x) antigen, suggesting that the assembly and/or presentation of LPS is independent of the AlpAB outer membrane proteins. However, a truncation of the LPS O-side chain by a galE mutation abolished the presentation of the Le(x) epitope. This Le(x)-negative strain did not show any significant reduction in its binding capacity to the gastric tissue, when compared with the corresponding wild-type strain. From these data we conclude that the AlpAB-specific adherence is independent of the composition of the LPS and that the oligomeric Le(x) structure does not confer binding to the gastric biopsy material used in this study. As the adhesion properties of our H. pylori strain P1 vary in dependence on the respective biopsy donor it is assumed that the surface-exposed Le(x) epitope recognizes a different host cell receptor than AlpAB, which was probably not present in the tissue sections used in this study.

CagA tyrosine phosphorylation and interleukin-8 induction by Helicobacter pylori are independent from alpAB, HopZ and bab group outer membrane proteins

In several studies Helicobacter pylori type I strains (cag-positive strains) have been described to translocate their CagA protein into epithelial cells, where it is tyrosine-phosphorylated. The intimate contact allows a Cag-dependent bacteria-to-cell signaling inducing the secretion of the chemokine interleukin-8. Although a contact between the bacterial and the eukaryotic cell is known to be necessary for these signal transduction events the bacterial adhesin and the cellular receptor are unknown, so far. In this study, we investigated the influence of several outer membrane proteins associated with adherence on CagA translocation and IL-8 induction. The quantitative assessment of a cag deletion mutant strain binding to epithelial cells revealed that the Cag secretion apparatus is not primarily necessary for attachment. In contrast, the knockout mutation of the adherence-associated alpAB locus significantly reduced the binding capacity in two independent strains. Despite this partial adherence defect, the alpAB mutation did not affect CagA translocation and IL-8 induction. The mutagenesis of the bab group genes hp317, hp896 and hp1243 in H. pylori 26695 did not influence the Cag-dependent signaling either. No causative linkage could be found between the production of the outer membrane proteins HopZ, OipA or seven additional outer membrane proteins and CagA translocation or IL-8 induction.

Carbohydrate carriers affect adhesion of H. pylori to immobilized Leb-oligosaccharide

The present study involved comparison of adhesion of Helicobacter pylori KH202 to immobilized Le(b)-oligosaccharide carried on different carriers, i.e. Leb-oligosaccharide conjugated with polyacrylamide, bovine serum albumin, and dipalmitoylphosphatidylethanolamine (Le(b)-PAA, Le(b)-BSA, and Le(b)-DPPE). All of the Le(b)-oligosaccharide-carrying neoglycoconjugates served as ligands for H. pylori. However, H. pylori required 10-fold and 100-fold quantities of Le(b)-antigen to adhere to Le(b)-PAA and to Le(b)-DPPE in comparison to the quantity of Le(b)-antigen needed to adhere to Le(b)-BSA, respectively. H. pylori adhesion to Le(b)-PAA and Le(b)-DPPE was clearly inhibited by Le(b)-oligosaccharide, but adhesion to Le(b)-BSA was hardly inhibited by the oligosaccharide. Therefore, the carbohydrate carrier affects the affinity of H. pylori KH202 toward Le(b)-antigen, although the bacteria recognize Le(b)-antigen regardless of the carbohydrate carrier.

Bacteroides forsythus hemagglutinin is inhibited by N-acetylneuraminyllactose

Bacteroides forsythus, which has been recognized as a pathogen associated with periodontitis, produces a hemagglutinin. The hemagglutinin was localized in the envelope of B. forsythus. The hemagglutinating activity was inhibited by lactose at concentrations as low as 1 mM, and by L-arginine and L-lysine at concentrations of 100 mM. N-Acetylneuraminyllactose (NeuAc-lactose) was at least 100 times more potent an inhibitor than lactose, as it completely inhibited the hemagglutination at concentrations below 10 microM. This is similar to the Helicobacter pylori hemagglutinin. The hemagglutinin was heat-labile, and resistant to treatment with proteases such as trypsin. A specific antibody raised against one of the S-layer proteins that are major species-specific proteins had no inhibitory effect on the hemmaglutination. These results suggest that the NeuAc-lactose-sensitive adhesin of B. forsythus may play an important role in colonization in the oral cavity.

Decreased adherence of cagG-deleted Helicobacter pylori to gastric epithelial cells in Japanese clinical isolates

BACKGROUND

The cag pathogenicity island (cag PAI) is a major virulence factor. The ability of Helicobacter pylori to adhere to gastric epithelial cells is an important initial step for virulence. The aim of this study was to evaluate the relationship between genetic variations of cag PAI in Japanese clinical isolates and the ability of H. pylori to adhere to gastric epithelial cells.

MATERIALS AND METHODS

The polymerase chain reaction and Southern blot analysis were used to verify the presence or absence of cagA, cagE, cagG, cagI and cagM in the cag PAI in 236 Japanese clinical isolates. The ability of H. pylori to adhere to KATOIII cells was examined by flow cytometry.

RESULTS

Seven (3.0%) cag PAI partial-deleted strains were found in 236 clinical isolates, and these strains showed three patterns in the deleted region within the cag PAI. All of the cagG-deleted strains showed decreased adherence to KATOIII cells, in comparison with cagG-positive strains. These strains had abolished IL-8 induction despite the presence of cagE, which is essential for IL-8 induction.

CONCLUSIONS

Our results suggest that cagG or surrounding genes in the cag PAI has a function related to adhesion to epithelial cells.

Inhibition of Helicobacter pylori adherence by a peptide derived from neuraminyl lactose binding adhesin

Helicobacterpylori, like many other gut colonizing bacteria, binds to sialic acid rich macromolecules present on the gastric epithelium. NLBH (neuraminyl lactose binding haemagglutinin) a 32 kDa adhesin located on the surface of H. pylori has been shown to have specific affinity towards NeuAcalpha2,3Galbeta1,4Gluc(3'SL). This sialic acid moiety is over-expressed in an atrophic stomach undergoing parietal cell depletion. Antibodies against a lysine rich peptide fragment of NLBH inhibit agglutination of human erythrocytes. This lysine rich sequence from NLBH was proposed to be the receptor-binding site. In order to elucidate the binding of NLBH to gastric epithelium, a peptide (D-P-K-R-T-I-Q-K-K-S) was synthesized. A series of experiments were performed involving adherence inhibition assays, 2D-NMR, molecular modelling and measurement of modulation in acid secretion. Results indicated that the peptide fragment could be involved in receptor recognition, which is important for the binding of H. pylori to gastric epithelium. The binding is possibly through hydrogen bonding. Two lysines and a threonine residue seem to be within the hydrogen bonding distance of NeuAcalpha2,3Galbeta1,4Gluc. Further, in vitro assays were performed to evaluate the role of the peptide on acid secretion by parietal cells isolated from human fundal biopsies. Interestingly, the peptide increases acid secretion only in H. pylori negative and in treated patients but not in H. pylori positive patients. This highlights the role of NLBH in acid secretion and could be of some consequence in the prognosis of the disease.

HpaA shows variable surface localization but the gene expression is similar in different Helicobacter pylori strains

Due to earlier contradictory results regarding the localization of the putative Helicobacter pylori adhesin A (HpaA), we aimed to compare the gene and protein expression and surface localization of HpaA in different H. pylori strains. Five H. pylori strains were cultivated for 11 days and analysed by Northern blot analysis, flow cytometry (FCM), semi-quantitative dot blot, colony blot, immuno-electron microscopy (IEM), and phase-contrast microscopy. The highest transcriptional activity of the hapA gene as observed after 3-4 days of cultivation and two mRNA transcripts of 1600 and 3100 nucleotides, respectively, were detected in all five strains with the hpaA probe. We also showed by reverse transcription-polymerase chain reaction (RT-PCR) that the hpaA gene is co-transcribed with the downstream omp18 gene. The highest total HpaA protein production in bacteria occurred between day 3 and 7, as determined by semi-quantitative dot blot, and was similar in the different strains. The maximal proportion of cells with HpaA on the bacterial surface, detected by FCM, was for strain SS1, 90%; Hel 344, 60%; CCUG 17875, 61%; CCUG 17874, 86% and for strain AH 244 only 35%. By IEM HpaA was detected in all strains both on the bacterial surface and on the flagellar sheath.

Helicobacter pylori-binding gangliosides of human gastric adenocarcinoma

Acidic and neutral glycosphingolipids were isolated from a human gastric adenocarcinoma, and binding of Helicobacter pylori to the isolated glycosphingolipids was assessed using the chromatogram binding assay. The isolated glycosphingolipids were characterized using fast atom bombardment mass spectrometry and by binding of antibodies and lectins. The predominating neutral glycosphingolipids were found to migrate in the di- to tetraglycosylceramide regions as revealed by anisaldehyde staining and detection with lectins. No binding of H. pylori to these compounds was obtained. The most abundant acidic glycosphingolipids, migrating as the GM3 ganglioside and sialyl-neolactotetraosylceramide, were not recognized by the bacteria. Instead, H. pylori selectively interacted with slow-migrating, low abundant gangliosides not detected by anisaldehyde staining. Binding-active gangliosides were isolated and characterized by mass spectrometry, proton nuclear magnetic resonance, and lectin binding as sialyl-neolactohexaosylceramide (NeuAcalpha3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer) and sialyl-neolactooctaosylceramide (NeuAcalpha3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1Cer).

pathogenesis of Helicobacter pylori-induced gastric inflammation

Helicobacter pylori causes persistent inflammation in the human stomach, yet only a minority of persons harbouring this organism develop peptic ulcer disease or gastric malignancy. An important question is why such variation exists among colonized individuals. Recent evidence has demonstrated that H. pylori isolates possess substantial phenotypic and genotypic diversity, which may engender differential host inflammatory responses that influence clinical outcome. For example, H. pylori strains that possess the cag pathogenicity island induce more severe gastritis and augment the risk for developing peptic ulcer disease and distal gastric cancer. An alternative, but not exclusive, hypothesis is that enhanced inflammation and injury is a consequence of an inappropriate host immune response to the chronic presence of H. pylori within the gastric niche. Investigations that precisely delineate the mechanisms responsible for induction of gastritis will ultimately help to define which H. pylori-colonized persons bear the highest risk for subsequent development of clinical disease, and thus, enable physicians to focus eradication therapy.

Requirement of ceramide for adhesion of Helicobacter pylori to glycosphingolipids

Direct adhesion of Helicobacter pylori to immobilized glycosphingolipids (GSLs) was compared to that of their corresponding oligosaccharide-conjugated neoglycoconjugates in order to clarify the roles of the carbohydrate and lipid portions of GSLs in H. pylori adhesion. These bacteria were found to adhere to sulfatide, GM3, GalCer and LacCer, but not to ceramide, sphingomyelin, or polyacrylamides conjugated with beta-galactose, lactose, 3'-sialyllactose or 3'-sulfo-beta-galactose. Furthermore, neoglycolipids or bovine serum albumin derivatives with corresponding oligosaccharides were unable to serve as the ligands. H. pylori adhesion to GalCer with alpha-hydroxyl fatty acid was much stronger than GalCer with the non-hydroxyl fatty acid. These results suggest that H. pylori recognize the conformation of GSL with alpha-hydroxyl fatty acid on solid phase.