Adherence of Helicobacter pylori cells and their surface components to HeLa cell membranes

Blue light emitting diodes cripple Helicobacter pylori by targeting its virulence factors

BACKGROUND

The endogenous photosensitizing porphyrins in Helicobacter pylori (H. pylori), make blue light therapy an attractive addition to the armamentarium in the war against this very prevalent and difficult to treat infectious agent.

METHODS

In the current study we examined in vitro the effect of blue LED (Light Emitting Diode) irradiation for 1-6 minutes on the viability and virulence factors of H. pylori, which allow this microorganism to colonize and establish infection. Specifically, we examined the effects of blue LED on urease production, motility, adhesion and biofilm formation.

RESULTS

We found that exposure to blue LED for 1-6 minutes significantly decreased the viability of H. pylori and caused decreased urease activity, as well as, swarming motility. Furthermore, blue LED irradiation for 6 minutes caused greater than 50% disruption of preformed mature biofilms of H. pylori, relative to controls.

CONCLUSIONS

Collectively, the results of our in-vitro study indicate that therapy with blue LED may be an added weapon in the eradication of H. pylori by targeting the virulence factors of this very common pathogen. We envisage that phototherapy will have an adjuvant effect on conventional anti-H. pylori therapy, especially considering its efficacy in biofilm disruption and the fact that microorganisms are unlikely to develop resistance as a result of the multi-target effects.

Role of the Flagellar Hook-Length Control Protein FliK and σ28 in cagA Expression in Gastric Cell-Adhered Helicobacter pylori

Adherence of Helicobacter pylori to the gastric epithelial cell line AGS strongly induces expression of fliK encoding a flagellar hook-length control protein. FliK has a role in triggering dissociation of the alternate sigma factor, σ(28), from a nonfunctional σ(28)-FlgM complex, releasing free, functional σ(28). The σ(28)-RNA polymerase initiates transcription of cagA, the major virulence gene, from a promoter identified in this study. Consequently, significant up-regulation of cagA was observed in AGS-adhered H. pylori. Direct binding of σ(28) to the cagA promoter was demonstrated by chromatin immunoprecipitation and the transcription start site was identified by 5' RACE (rapid amplification of complementary DNA ends). The σ(28)-dependent cagA promoter was active specifically in AGS-adhered H. pylori, and this motif might be associated with high cagA expression and severity of disease. These results also indicate that H. pylori has evolved to integrate expression of the major virulence gene cagA with the flagellar regulatory circuit, essential for colonization of the human host.

Host cell contact induces fur-dependent expression of virulence factors CagA and VacA in Helicobacter pylori

BACKGROUND

Helicobacter pylori, a gram negative bacterium, colonizes the stomach in a majority of the world population. The two major virulence factors of H. pylori VacA and CagA, thought to be associated with chronic inflammation and disease, have been extensively studied, but the regulation of the expression of these virulence genes in H. pylori remains poorly understood.

METHODS

qRT-PCR was performed to quantify gene expression in unadhered and AGS-adhered H. pylori. Δfur mutant was constructed by splicing by overlap extension PCR and allelic exchange.

RESULTS

Adherence of H. pylori to the gastric epithelial cell line AGS strongly induces the expression of both cagA and vacA. Induction of cagA and vacA in the AGS cell-adhered H. pylori Δfur mutant strain was consistently lower than in the adhered parent strain. However, expression of the genes was similar between the wild-type and Δfur mutant strains in the unadhered state, suggesting that Fur has a role in the upregulation of cagA and vacA expression, especially in AGS-adhered H. pylori. Consistent with these results, microscopic observations revealed that infection of AGS cells with H. pylori Δfur mutant strain produced much less damage as compared to that produced by the wild-type H. pylori strain.

CONCLUSIONS

These results suggested that cagA and vacA gene expression is upregulated in H. pylori, especially by host cell contact, and Fur has a role in the upregulation.

In vitro anti-Helicobacter pylori activity of diallyl sulphides and protocatechuic acid

The in vitro inhibitory effects of diallyl disulphide (DADS), diallyl trisulphide (DAT), roselle calyx extract and protocatechuic acid (PA) on the growth of Helicobacter pylori (15 susceptible, 11 clarithromycin-resistant and 9 metronidazole-resistant strains) were studied. The inhibition zone was determined after each agent had been heated at 25, 60, 100 degrees C for 60 min. The minimal inhibitory concentration (MIC) of each agent was determined by the tube dilution assay. The results showed that heat treatment did not affect the anti-H. pylori activity of DADS, DAT, roselle calyx extract and PA, and the MIC values of these agents against test H. pylori strains were in the range 8-64 mg/L. The time-kill study assay for DAT and PA at 1x MIC was monitored in Muller Hinton broth supplemented with 10% horse blood or mice stomach homogenate. Both DAT and PA inhibited the growth of all test H. pylori in broth and mice stomach homogenate (p < 0.05); however, the inhibitory effects of these two agents were less in mice stomach homogenate than in broth (p < 0.05). DAT at 4, 6, 8, 10, 12, 14 mg/L and PA at 8, 16, 24, 32, 40, 48 mg/L were used for urease activity assay. These two agents significantly reduced urease activity of test H. pylori strains (p < 0.05), in which DAT and PA at 1x MIC reduced the urease activity of H. pylori to 70% and 40%, respectively. These agents, based on their lower MIC values and heat tolerance, might be useful in the prevention or therapy of H. pylori.

Production of anti-Helicobacter pylori urease-specific immunoglobulin in egg yolk using an antigenic epitope of H. pylori urease

The potential therapeutic effects of Helicobacter pylori-specific immunoglobulin (IgY-Hp) derived from egg yolk and identification of the immunodominant H. pylori proteins have previously been reported. In this study, the urease epitope that is recognized by IgY-Hp was identified and used as an immunogen to produce urease-specific IgY (IgY-HpU). Epitope regions were mapped and peptides of selected epitope regions were synthesized. The IgY-Hp titre against synthetic peptides was evaluated using ELISA analysis. Hens were immunized with synthetic peptides conjugated with BSA. Urease activity was quantified by measuring the optical density of an indicator dye. Of the five synthetic peptides assayed, a peptide representing 15 amino acid residues of UreB (UB-3; aa 396-410, DNDNFRIKRYLSKYT) was specifically recognized by the IgY-Hp. Immunization of hens with BSA-conjugated UB-3 resulted in the generation of IgY-HpU. IgY-HpU markedly reduced H. pylori urease activity by 80 % as compared to control IgY (IgY-BSA). The availability of the synthetic UreB-derived peptide enabled the production of highly specific anti-urease IgY, which had a significant inhibitory effect on H. pylori urease activity. Therefore, specific IgY-HpU produced using the synthetic peptide may be an effective tool against infection by H. pylori.

Use of egg yolk-derived immunoglobulin as an alternative to antibiotic treatment for control of Helicobacter pylori infection

The present study evaluated the potential use of immunoglobulin prepared from the egg yolk of hens immunized with Helicobacter pylori (immunoglobulin Y [IgY]-Hp) in the treatment of H. pylori infections. The purity of our purified IgY-Hp was 91.3%, with a yield of 9.4 mg of IgY per ml of egg yolk. The titer for IgY-Hp was 16 times higher than that for IgY in egg yolk from nonimmunized hens, and IgY-Hp significantly inhibited the growth and urease activity of H. pylori in vitro. Bacterial adhesion on AGS cells was definitely reduced by preincubation of both H. pylori (10(8) CFU/ml) and 10 mg of IgY-Hp/ml. In Mongolian gerbil models, IgY-Hp decreased H. pylori-induced gastric mucosal injury as determined by the degree of lymphocyte and neutrophil infiltration. Therefore, in this experimental model, H. pylori-associated gastritis could be successfully treated by orally administered IgY-Hp. The immunological activity of IgY-Hp stayed active at 60 degrees C for 10 min, suggesting that pasteurization can be applied to sterilize the product. Fortification of food products with this immunoglobulin would significantly decrease the H. pylori infection. In conclusion, the IgY-Hp obtained from hens immunized by H. pylori could provide a novel alternative approach to treatment of H. pylori infection.

Expression of mucosal cyto-chemokine mRNAs in patients with Helicobacter pylori infection

BACKGROUND

Helicobacter pylori-induced destruction of the gastroduodenal mucosal barrier is initiated with mucosal infiltration of inflammatory cells. Cytokines and chemokines have been suggested to play important roles in the migration and activation of these inflammatory cells into the mucosa. The present study aimed to investigate expression rates of cyto-chemokine mRNAs using gastric mucosal biopsy specimens.

METHODS

In 98 patients infected with Helicobacter pylori, mucosal mRNA expression rates of cytokines (IL-1 beta, IL-6, and IL-10), C-C chemokines (macrophage inflammatory protein 1 alpha (MIP-1 alpha), and macrophage inflammatory protein 1 beta (MIP-1 beta), monocyte chemotactic and activating factor (MCAF), regulated on activation, normal T cell expressed and presumably secreted (RANTES)) and C-X-C chemokines (IL-8 and growth regulated a (GRO-alpha)) were examined using reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The expression rates of mRNA for IL-8, GRO-alpha, MIP-1 alpha and RANTES were significantly more increased in H. pylori-positive patients than in H. pylori-negative patients. However, the expressions of IL-1 beta, IL-6 and IL-10 mRNA were statistically not different between two groups. After eradication of H. pylori, expressions of mRNA for three cytokines (IL-1 beta, IL-6 and IL-10), four C-C chemokines (MIP-1 alpha, MIP-1 beta, MCAF and RANTES) and two C-X-C chemokines (IL-8 and GRO-alpha) were significantly decreased.

CONCLUSION

These results suggest that C-X-C chemokines and some C-C chemokines play important roles in H. pylori-associated peptic ulcer diseases.

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.

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.

Antibiotic susceptibility of attached and free-floating Helicobacter pylori

Helicobacter pylori are found attached to mucous cells of the human stomach or under the mucous layer. Models mimicking the in vivo situation may be more suitable for H. pylori MIC determinations than traditional agar dilution methods. Megraud et al. (Antimicrobial Agents and Chemotherapy 1991, 35, 869-72) developed a model for measuring the susceptibility of attached and free-floating H. pylori. We have modified this model so that free-floating and attached H. pylori are treated in a more similar manner, before and after incubation with antibiotic, and performed additional controls to ensure H. pylori and tissue culture cells are not detrimentally affected and maintain their viability during the course of the experiment. We found only 10% of plate-grown H. pylori were competent for attachment to HEp-2 cells; however, all progeny of attached bacteria remained adherent. Killing curves were performed using 0, 0.001, 0.01, 0.1 and 1 mg/L amoxycillin, and 0, 0.0025, 0.0075 and 0.01 mg/L clarithromycin. H. pylori divided at concentrations <or= 0.01 mg/L amoxycillin and <or= 0.0025 mg/L clarithromycin. Contrary to the previous study, using our modified method we found that HEp-2 adherent and freefloating H. pylori are equally susceptible to amoxycillin (strains 26695, CCUG18943, CCUG19104 and CCUG19110) and clarithromycin (strain 26695). Therefore, we find no evidence that attachment of H. pylori to eukaryotic cells increases their resistance to antibiotics compared with non-attached bacteria. Nonetheless, these results confirm confidence in traditional MIC studies when a comparison is made between susceptible and resistant strains.

Analysis of Helicobacter pylori binding site on HEp-2 cells and three cell lines from human gastric carcinoma

Helicobacter pylori (H. pylori) is a pathogen responsible for chronic gastritis and peptic ulcer diseases. It colonises the gastric mucus layer and adheres to the gastric epithelial cell surface. As this adherence is the first step of infection, it is important to study the adherence mechanism. The aim of this study was to analyse the specific binding assay of H. pylori to HEp-2 cells and three gastric phenotype cell lines, AGS, MKN-45 and AZ-521. H. pylori NCTC 11637 grown on agar plates was harvested and used in experiments. H. pylori was inoculated to pre-cultured cell monolayers. Adhered bacteria were labelled with an anti-H. pylori antibody and an FITC-conjugated secondary antibody and quantified by using a fluorescent plate reader. Microbial adherence to HEp-2 cells increased with incubation time and incubated concentration of H. pylori. No further increase was obtained with four or more hours of incubation or with a concentration of 4 x 10(7) bacteria/well or more. Scatchard analysis revealed a linear plot and the Bmax value was 88.3. Similar adherence patterns were obtained when AGS, AZ-521 and MKN-45 cells were used for adherence assays, but they had a lower binding affinity than HEp-2 cells and AZ-521. MKN-45 cells had less receptors than HEp-2 and AGS cells. In conclusion, H. pylori adhered to the cell surface could be quantified by this assay method. H. pylori adhesion to cell surfaces has a single population of binding site and one type of binding site on HEp-2, AGS, AZ-521 and MKN-45 cells.

Metabolism and genetics of Helicobacter pylori: the genome era

The publication of the complete sequence of Helicobacter pylori 26695 in 1997 and more recently that of strain J99 has provided new insight into the biology of this organism. In this review, we attempt to analyze and interpret the information provided by sequence annotations and to compare these data with those provided by experimental analyses. After a brief description of the general features of the genomes of the two sequenced strains, the principal metabolic pathways are analyzed. In particular, the enzymes encoded by H. pylori involved in fermentative and oxidative metabolism, lipopolysaccharide biosynthesis, nucleotide biosynthesis, aerobic and anaerobic respiration, and iron and nitrogen assimilation are described, and the areas of controversy between the experimental data and those provided by the sequence annotation are discussed. The role of urease, particularly in pH homeostasis, and other specialized mechanisms developed by the bacterium to maintain its internal pH are also considered. The replicational, transcriptional, and translational apparatuses are reviewed, as is the regulatory network. The numerous findings on the metabolism of the bacteria and the paucity of gene expression regulation systems are indicative of the high level of adaptation to the human gastric environment. Arguments in favor of the diversity of H. pylori and molecular data reflecting possible mechanisms involved in this diversity are presented. Finally, we compare the numerous experimental data on the colonization factors and those provided from the genome sequence annotation, in particular for genes involved in motility and adherence of the bacterium to the gastric tissue.

Role of gamma interferon in Helicobacter pylori-induced gastric inflammatory responses in a mouse model

The immune responses to Helicobacter pylori infection play important roles in gastroduodenal diseases. The contribution of gamma interferon (IFN-gamma) to the immune responses, especially to the induction of gastric inflammation and to protection from H. pylori infection, was investigated with IFN-gamma gene knockout (IFN-gamma-/-) mice. We first examined the colonizing abilities of eight H. pylori strains with a short-term infection test in order to select H. pylori strains which could colonize the mouse stomach. Only three strains (ATCC 43504, CPY2052, and HPK127) colonized C57BL/6 wild-type mice, although all of the strains except for ATCC 51110 could colonize IFN-gamma-/- mice. The number of H. pylori organisms colonizing the stomach in wild-type mice was lower than that in IFN-gamma-/- mice. Oral immunization with the CPY2052 sonicate and cholera toxin protected against infection with strain CPY2052 in both types of mouse. These findings suggested that IFN-gamma may play a protective role in H. pylori infection, although the degree of its protective ability was estimated to be low. In contrast, in a long-term infection test done to examine the contribution of IFN-gamma to gastric inflammation, CPY2052-infected wild-type mice developed a severe infiltration of mononuclear cells in the lamina propria and erosions in the gastric epithelium 15 months after infection, whereas CPY2052-infected IFN-gamma-/- mice showed no inflammatory symptoms. This result clearly demonstrated that IFN-gamma plays an important role in the induction of gastric inflammation caused by H. pylori infection.

Use of immunoblot assay to define serum antibody patterns associated with Helicobacter pylori infection and with H. pylori-related ulcers

Serology has been used worldwide to detect Helicobacter pylori infection. Using an immunoblot assay with an antigen from strain ATCC 43579, we sought to determine the antibodies which were good markers of colonization and the antibody patterns associated with ulcers or atrophy. Out of 98 dyspeptic patients, 41 were colonized by H. pylori, based on a positive culture or on positive results of both a urease test and direct examination. These 41 patients were seropositive by an enzyme immunoassay, and 12 of them had ulcers and 29 had evidence of atrophy. Fifty-seven of the 98 patients were noncolonized. Twenty-five of the 57 had evidence of gastric atrophy, and 10 were seropositive; 5 of these 10 had ulcers. By Western blot analysis, 12 antibodies were significantly more frequent in sera from colonized patients, and they produced immunoreactive bands at 125, 87, 74, 66, 54, 48, 46, 42, 35, 30, 16 and 14 kDa. The presence of at least one band at 54, 35, or 42 kDa was the best marker of infection (sensitivity, 95%; specificity, 82%). In the group of colonized patients, none of the antibody patterns were correlated to gastric atrophy. Conversely, the presence of a band at 125, 87, or 35 kDa was statistically associated with the presence of an ulcer. The simultaneous presence of bands at 87 and 35 kDa predicted the risk of ulcers with 83% sensitivity and 69% specificity. By using CagA-positive and VacA-positive strains and CagA-negative and VacA-negative isogenic mutants, the antigens corresponding to the bands at 125 and 87 kDa were shown to be CagA and VacA, respectively. On the other hand, the 35-kDa antigen is a novel uncharacterized component of H. pylori. These results may help to optimize the composition of antigenic preparations for serologic detection of H. pylori colonization. Immunoblot assay would be useful for screening patients at high risk of ulcers.

A novel flow cytometric assay for quantitating adherence of Helicobacter pylori to gastric epithelial cells

Adherence may be an important virulence factor for Helicobacter pylori. Current methods available for quantitation of adherence are time consuming and liable to observer error. A new direct technique for fluorescent labelling of bacteria has been developed to quantitate adherence of H. pylori to epithelial cells by fluorescence activated cell sorting (FACS). Type strains of H. pylori, H. mustelae, H. cinaedi and H. fennelliae were grown microaerobically in broth culture for 24 h and fluorescently labelled by incubation with carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) at 37 degrees C. After washing to remove excess CFDA-SE, bacteria were co-incubated (ratio 10:1) with gastric epithelial cells at 37 degrees C for up to 24 h. After washing to remove non-adherent bacteria, epithelial cells were detached with EDTA (2 mM) and fixed with formaldehyde for flow cytometry. Adherence was quantitated both in terms of the proportion of cells with adherent H. pylori and as the mean number of adherent bacteria per cell. All H. pylori strains adhered to gastric-type epithelial cells. The proportion of cells with bound bacteria varied from 40-99% and the number of bacteria per cell from 1-50, both of which correlated with microscopy (r = 0.6, and r = 0.8 respectively, n = 35). Time course studies demonstrated saturation of binding by H. pylori within 90 min. For H. mustelae, H. cinaedi and H. fennelliae the proportion of cells with bound bacteria varied from 5-15% and the mean number of bacteria per cell was < 4. Binding of H. pylori to epithelial cells could be partly blocked by pre-incubation with polyclonal anti-sera or using oligosaccharides against potential binding epitopes of gastric mucus. Fluorescent labelling of H. pylori with CFDA-SE in combination with flow cytometry provides a quick, specific, and sensitive method to quantitate in vitro the adherence of H. pylori.

Neutrophil-activating protein mediates adhesion of Helicobacter pylori to sulfated carbohydrates on high-molecular-weight salivary mucin

The in vitro binding of surface-exposed material and outer membrane proteins of Helicobacter pylori to high-molecular-weight salivary mucin was studied. We identified a 16-kDa surface protein which adhered to high-molecular-weight salivary mucin. This protein binds specifically to sulfated oligosaccharide structures such as sulfo-Lewis a, sulfogalactose and sulfo-N-acetyl-glucosamine on mucin. Sequence analysis of the protein proved that it was identical to the N-terminal amino acid sequence of neutrophil-activating protein. Moreover, this adhesin was able to bind to Lewis x blood group antigen.

Inhibition of Helicobacter pylori binding to gastrointestinal epithelial cells by sialic acid-containing oligosaccharides

Helicobacterpylori, the ulcer pathogen residing in the human stomach, binds to epithelial cells of the gastric antrum. We have examined binding of 13 bacterial isolates to epithelial cell lines by use of a sensitive microtiter plate method in which measurement of bacterial urease activity provides the means for quantitation of bound organisms. Several established human gastrointestinal carcinoma cell lines grown as monolayers were compared for suitability in these assays, and the duodenum-derived cell line HuTu-80 was selected for testing bacterial binding inhibitors. When bacteria are pretreated with oligosaccharides, glycoproteins, and glycolipids, a complex picture of bacterial-epithelial adherence specificities emerges. Among the monovalent inhibitors tested, 3'-sialyllactose (NeuAc alpha2-3Gal beta1-4Glc; 3'SL) was the most active oligosaccharide, inhibiting adherence for recent clinical isolates of H. pylori with a millimolar 50% inhibitory concentration (IC50). Its alpha2-6 isomer (6'SL) was less active. Most of the recent clinical isolates examined were inhibited by sialyllactose, whereas long-passaged isolates were insensitive. Among the long-passaged bacterial strains whose binding was not inhibited by 3'SL was the strain ATCC 43504, also known as NCTC 11637 and CCUG 17874, in which the proposed sialyllactose adhesin was recently reported to lack surface expression (P. G. O'Toole, L. Janzon, P. Doig, J. Huang, M. Kostrzynska, and T. H. Trust, J. Bacteriol. 177:6049-6057, 1995). Pretreatment of the epithelial monolayer with neuraminidase reduced the extent of binding by those bacteria that are sensitive to inhibition by 3'SL. Other potent inhibitors of bacterial binding are the glycoproteins alpha1-acid glycoprotein, fetuin, porcine gastric and bovine submaxillary mucins, and the glycolipid sulfatide, all of which present multivalent sialylated and/or sulfated galactosyl residues under the conditions of the binding assay. Consistent with this pattern, a multivalent neoglycoconjugate containing 20 mol of 3'SL per mol of human serum albumin inhibited bacterial binding with micromolar IC50. The H. pylori isolate most sensitive to inhibition by 3'SL was least sensitive to inhibition by sulfatide, gastric mucin, and other sulfated oligosaccharides. Bacteria that have been allowed to bind epithelial cells are also effectively detached by 3'SL. These results describe a heterogeneous adherence repertoire for these bacteria, but they also confirm the critical role of the 3'SL structure on human gastric epithelial cells as an adherence ligand for recent isolates of H. pylori.

Cell envelope characteristics of Helicobacter pylori: their role in adherence to mucosal surfaces and virulence

Helicobacter pylori colonises the gastric mucosa of humans and causes both antral gastritis and duodenal ulcer disease. Exactly how H. pylori causes disease is not known but several pathogenic determinants have been proposed for the organism. These include adhesins, cytotoxins and a range of different enzymes including urease, catalase and superoxide dismutase. Surface molecules of H. pylori such as flagella, lipopolysaccharide, the urease enzyme and outer membrane proteins are putative adhesin molecules. While phosphatidylethanolamine and the Lewis(b) blood group antigen have been proposed as receptor molecules for the organism the exact mechanism by which H. pylori adheres to the gastric mucosa has still to be identified. Characterisation of the adhesins of H. pylori could lead to the development of adhesin analogues for use in the inhibition of colonisation and improved therapy for ulcer disease. In vivo studies with isogenic mutants which are incapable of adhering to the gastric mucosa would greatly clarify the significance of adherence. Such mutants could possibly be useful as a vaccine against infection with wild-type organisms.

Adhesion of Helicobacter pylori strains to alpha-2,3-linked sialic acids

Helicobacter pylori is a human pathogen associated with gastritis and peptic ulcer. Adhesion properties of H. pylori to various structures have been described in the literature, including evidence for sialic acid-binding. To study the specificity and frequency of sialic acid-binding, fourteen H. pylori strains were investigated using haemagglutination with derivatized erythrocytes carrying sialic acids only on defined glycans and using haemagglutination inhibition assays. From these studies H. pylori strains can be grouped into sialic acid-dependent and sialic acid-independent classes. The sialic acid-dependent strains require alpha-2,3-linked sialic acid for haemagglutination. The potential roles of sialic acid-dependent adhesions for H. pylori-related infections are discussed.

Inhibitory and bactericidal activity of rokitamycin against Helicobacter pylori and morphological alterations

Rokitamycin is a macrolide antibiotic, recently entered into clinical use. Its in vitro activity and kill kinetics against Helicobater pylori have been evaluated at 1 x the minimum inhibitory concentration (MIC), 2 x MIC and 4 x MIC at 2, 4, 8, 24 hours and compared with those of clarithromycin, erythromycin and amoxicillin. Morphological changes in H. pylori induced by rokitamycin incubation at these MICs and times were also investigated by scanning electron microscopy. All the antibiotics tested had good inhibitory activity against H. pylori, a slow growing microorganism. The order of MIC activity was clarithromycin > amoxicillin > rokitamycin > erythromycin. Rokitamycin killed more rapidly than the other antibiotics, in fact H. pylori strains were totally killed at 8 h (2 x MIC) and 4 h (4 x MIC) and after only 2 h incubation all concentrations greatly decreased the CFU/ml. These effects were also confirmed by the rapid appearance of surface and morphological alterations (focal blebs, constrictions, rounded forms) in the normal structure of H. pylori observed by scanning electron microscopy. Clinical studies should be conducted to investigate the in vivo activity of rokitamycin, as an agent to be used in the combination therapies against H. pylori.

Cell surface glycosaminoglycans are not involved in the adherence of Helicobacter pylori to cultured Hs 198.St human gastric cells, Hs 746T human gastric adenocarcinoma cells, or HeLa cells

Hs 198.St cells (a line derived from normal human gastric tissue), Hs 746T cells (a line derived from human gastric adenocarcinoma), and HeLa cells were used together with 3H-labelled Helicobacter pylori, strain NCTC 11637 to determine if cell surface glycosaminoglycans could act as initial receptors for adherence of the bacteria. Although as much as 40% of the 3H-labelled bacteria adhered to monolayers of the cultured cells, removal of glycosaminoglycans by prior treatment of the cells with heparitinase, heparinase, or chondroitin ABC lyase had no effect in modifying the adherence. Prior addition of heparan sulfate, heparin, or chondroitin/dermatan sulfate to bacteria had no effect on adherence, nor were bacteria released when these same glycosaminoglycans or these same enzymes were added to cultures already containing adherent bacteria. These results indicated that neither heparan sulfate nor chondroitin/dermatan sulfate are involved as receptors in the initial adherence step of H. pylori to these cultured cells.

Adhesion of Helicobacter pylori to polarized T84 human intestinal cell monolayers is pH dependent

Epithelial cells, which form tight polarized monolayers on porous substrates, constitute ideal model systems to study bacterial adhesion and invasion. The binding of Helicobacter pylori to the apical membrane of T84 cells, an epithelial cell line derived from a human colon carcinoma, was assessed biochemically and morphologically. Attachment was rapid, and binding remained constant over time, with a significant (P < 0.01, Mann-Whitney U test) ca. fourfold increase at pH 5.4 (76% +/- 22%) compared with pH 7.4 (18% +/- 7%). In contrast, adhesion of enteropathogenic Escherichia coli was not enhanced at pH 5.4. The transepithelial electrical resistance of the T84 cell monolayers was not affected by pH or by H. pylori. Following binding, H. pylori induced a reorganization of the brush border as reflected by actin condensation, facilitating the intimate association of the bacteria with the apical plasma membrane. H.pylori was not internalized, as shown by confocal microscopy. Some bacteria, found in deep invaginations of the apical membrane, were probably inaccessible to gentamicin, thus accounting for the observed tolerance to the antibiotic. These data provide the first evidence that an acidic environment favors Helicobacter adhesion and that binding is followed by survival of the survival of the bacteria in pockets of the apical membrane.

The urease enzyme of Helicobacter pylori does not function as an adhesin

Helicobacter pylori urease is essential for colonization of the gastric mucosa irrespective of whether the stomach is acidic or hypochlorhydric. It has therefore been speculated that the enzyme functions as an adhesin. The aim of this study was to compare the adherence of H. pylori N6 with the adherence of an isogenic urease-negative mutant, strain N6(ureB::TnKm), to gastric cells. Strain N6 originated from a patient with gastritis. Strain N6(ureB::TnKm) is specifically modified in the gene which encodes the large subunit of urease, UreB, and hence does not form a UreA-UreB enzyme complex. We have used flow cytometry to assess the adherence of H. pylori to the cells. We have also used phase-contrast microscopy to assess the adherence of the organism to Kato III cells. In the absence of urea both strains bound to Kato III cells and to primary gastric cells. Binding of both strains to the cells occurred rapidly. The presence of urea in the incubation medium decreased the binding of strain N6 to the cells. This was due to a rise in the pH of the incubation medium, which caused loss of viability of the organism. Urea had no effect on the adherence of strain N6(ureB::TnKm). We conclude that the urease of H. pylori does not play a role in the adherence of the organism to gastric cells.

Refinement of, and new applications for, Helicobacter pylori colonization in pig gastric biopsy specimens cultured in vitro

BACKGROUND

As we have previously reported, pig gastric biopsy specimens cultured in vitro are a highly useful model for studies of Helicobacter pylori growth and adhesion. The aim of this study was to further refine the model in terms of mucosal specificity, culture time, bacterial adhesion, and drug delivery.

METHODS

H. pylori-inoculated antral and corporeal pig gastric specimens were cultured for up to 96 h. Biopsy viability, bacterial growth, and adhesion were determined every 24 h. Bismuth subcitrate and omeprazole were added to the top of the specimens via a bio-adhesive gel.

RESULTS

Corporeal and antral specimens could be cultured for 72 h and 96 h, respectively, without affecting the viability. In parallel experiments from the same pig the percentage adhesion and total number of adhering H. pylori was higher in corporeal than in antral specimens at 72 h (28% and 4 x 10(5) versus 15% and 4 x 10(4), respectively). Removal of loosely attached H. pylori by rinsing at 24 h doubled the percentage H. pylori adhered during the subsequent 48 h. Bismuth subcitrate had a dose-dependent inhibitory effect on H. pylori; when added to the mucosal side, omeprazole had no effect.

CONCLUSION

The pig in vitro biopsy model can be used for detailed H. pylori adhesion studies and for the screening of drugs added to the mucosal or serosal side.

Helicobacter colonization of biopsy specimens cultured in vitro is dependent on both mucosal type and bacterial strain

BACKGROUND

Colonization by Helicobacter pylori is strictly tissue-specific. We have previously reported on an in vitro adhesion model for pig and human gastric mucosa, in which biopsy specimens were successfully infected and cultured for 72h. The aim of this study was to compare H. pylori colonization of different mucosae and by different Helicobacter strains.

METHODS

Specimens from pig, rabbit, and rat antrum, pig urinary bladder, and pig duodenum were inoculated with two H. pylori strains and one H. mustelae strain. Four additional strains, including one mutant lacking flagella, were compared on pig antral specimens.

RESULTS

The viability of all mucosae was comparable at 48h of culture. The percentage adhering bacteria increased with time in all mucosae, reaching 17%, 11%, and 2% in pig, rabbit and rat antral mucosa, 11% in pig bladder, and 3% in duodenum at 48h. The type of H. pylori strain was a strong determinant for adhesion in pig antrum. Strain SVA40 had the highest adhesion; the mutant lacking flagella colonized very poorly. H. mustelae adhered to all types of mucosae in a more unspecific manner.

CONCLUSIONS

On the basis of tissue viability, bacterial colonization, and adhesion, pig antral mucosa is clearly superior. H. pylori strains differ in their ability to adhere to and colonize cultured mucosa.

Profound increase of Helicobacter pylori urease activity in gastric antral mucosa at low pH

The effect of pH on H. pylori urease activity in its ecological niche was studied in gastric antral biopsy specimens. Specimens were incubated in 10 mmol/liter urea solutions at pH range 3.3-8.2. Activity of urease was studied by measuring production of ammonia and change in pH of the solutions. Urease activity was reduced at pH 8.2 (1424 +/- 218 mumol/liter) but decreasing initial pH to neutral and acidic values resulted in significant maximal 6.5-fold increase in ammonia production (9491 +/- 1073 mumol/liter, P < 0.0005), which considerably raised the pH of the test solutions. Peak urease activity was between pH 5.0 and 7.0. In contrast to specimens incubated initially at pH 8.0, reincubation of washed specimens from solutions with initial pH 7.0 showed eightfold decreased urease activity. It is concluded that urease activity is markedly pH dependent with pH optima below the physiological mucosal surface pH. Furthermore, availability of urease is limited. Thus, an impaired gastric mucosal integrity allowing back diffusion of hydrogen ions may release urease activity, which might further weaken the mucus barrier and damage the gastric epithelium.

Helicobacter pylori and peptic disease in the pediatric patient

The data accumulated on Helicobacter pylori infection in children suggests an important causative role of the organism in gastritis and peptic ulcer disease in this age group. The importance of eradication of H pylori in asymptomatic children in relation to its role in peptic disease and cancer in adults is debatable. This article describes the current data on bacteriologic features, pathologic spectrum, clinical significance, epidemiology, methods of diagnosis, and treatment of H pylori infection in children. Further studies will provide the information on the pathogenicity, mode of transfer, and optimal treatment of H pylori infection.

Antibody response to Prevotella spp. in patients with ventilator-associated pneumonia

Although anaerobic bacteria are frequently isolated from the oropharyngeal flora, their potential pathogenic role in ventilator-associated pneumonia (VAP) has been poorly investigated. In order to evaluate the pathogenic role of Prevotella spp. isolated from protected specimen brushes, we investigated the systemic humoral response with the enzyme-linked immunosorbent assay (ELISA) and Western blot (immunoblot) in 13 patients who developed a VAP associated with Prevotella species (group I). The antigen used was a mixture of whole-cell proteins taken from four reference Prevotella strains. We compared the antibody levels observed in these patients with those measured in 30 patients who developed a VAP unrelated to anaerobic bacteria (group II), in 27 patients with dental stumps (group III), and in 30 healthy patients (group IV) who had Prevotella species on dental plaque. The ELISA levels obtained in the four groups showed significant differences between group I and each of the three control groups (P < 0.05). The antibody profiles obtained by Western blot showed an intensity of response roughly superposable over levels obtained by ELISA and a species specificity. These findings suggested that colonization of these patients with Prevotella species may have been associated with an infectious process leading to a systemic humoral response and that these bacteria could play a role in VAP.

Cell surface characteristics of Helicobacter pylori

Helicobacter pylori is an important gastroduodenal pathogen of humans. Immunological and structural studies have been performed on the phospholipids, lipopolysaccharides (LPS) and some surface proteins of H. pylori strains. H. pylori LPS has, in general, low immunological activity and this property may aid the survival of this chronic infection. Nevertheless, H. pylori LPS has been found to influence the quality of gastric mucin and to stimulate pepsinogen secretion, thereby contributing to gastric disease. A number of putative adhesins of the bacterium have been described. This multiplicity of adhesins may reflect that H. pylori adherence is a multi-step process involving different interactions, and that different adhesins may mediate adherence to various sites in gastric tissue.

Adhesion to and invasion of HeLa cells by Helicobacter pylori

Eight clinical isolates and two reference strains of Helicobacter pylori were studied with regard to their interactions with HeLa cells. All the isolates adhered poorly to HeLa cells and the number of invasive bacteria was very low. No correlation was found between the adherence and invasiveness of the isolates on one hand, and the corresponding patients having ulcer or non-ulcer disease, or the ability of the strains to produce cytotoxin and to induce an oxidative burst of human polymorphonuclear leukocytes without opsonins, on the other. These results indicate that invasion of epithelial cells would play no important role in the pathogenesis of infections caused by H. pylori.

Spiral bacteria in the human stomach: the gastric helicobacters

During the past decade, Helicobacter pylori has become recognized as one of the most common human pathogens, colonizing the gastric mucosa of almost all persons exposed to poor hygienic conditions from childhood. It also is often found, albeit with a lower frequency, in groups of high socioeconomic status. H. pylori causes chronic active gastritis and is a major factor in the pathogenesis of duodenal ulcers and, to a lesser extent, gastric ulcers. In addition, the presence of this bacterium is now recognized as a risk factor for gastric adenocarcinoma and lymphoma. Nevertheless, most infections appear without clinical consequences. In this second decade of intensive research, it is important to understand why H. pylori is sometimes a dangerous pathogen, and to determine how it can be eradicated in those at highest risk for severe disease.

Helicobacter pylori

Helicobacter pylori is an important cause of chronic active gastritis and is strongly associated with peptic ulcer disease and gastric cancer. H. pylori colonizes the surface of the gastric epithelium with production of a number of factors, resulting in inflammation and an altered mucosa. H. pylori infection occurs world-wide and the mode of transmission most likely is from human to human via the fecal-oral and/or the oral-oral route. Treatment and, in the future, prevention of this infection may result in a marked diminution of upper gastrointestinal tract disease.

Interaction of lipopolysaccharides of Helicobacter pylori with basement membrane protein laminin

The ability of hemagglutinating and poorly hemagglutinating strains of the gastroduodenal pathogen Helicobacter pylori to bind 125I-radiolabelled laminin was quantitated in a liquid phase assay. Although all strains bound laminin, some hemagglutinating strains were good binders of laminin (maximum of 31% binding), whereas poorly hemagglutinating strains bound intermediate to small amounts of laminin (minimum of 6% binding). Since a hydrophobic component of the bacterium has been reported to be involved in binding of laminin (T. J. Trust, P. Doig, L. Emödy, Z. Kienle, T. Wadström, and P. O'Toole, Infect. Immun. 59:4398-4404, 1991), we investigated the role of lipopolysaccharide (LPS) in the interaction of both types of strains with laminin. Although the extent of inhibition varied among strains, laminin binding to hemagglutinating and poorly hemagglutinating strains was inhibited with homologous and heterologous smooth-form LPS. The ability of heterologous rough-form LPS to produce inhibition comparable to that shown by smooth-form LPS indicated that the O side chain of H. pylori LPS was not involved in the interaction. Further inhibition experiments with dephosphorylated LPS, isolated core oligosaccharide, and free lipid A suggested that a phosphorylated structure in the core oligosaccharide mediates the interaction of a hemagglutinating strain of H. pylori with laminin, whereas a conserved nonphosphorylated structure in the core oligosaccharide mediates the interaction of a poorly hemagglutinating strain. Furthermore, we showed that the interaction of H. pylori LPS with 125I-radiolabelled laminin in a solid phase assay was saturable, specific, and inhibitable with unlabelled laminin. It was postulated that the initial recognition and binding of laminin by H. pylori may occur through LPS and that subsequently a more specific interaction with a lectin-like adhesin on the bacterial surface occurs.

Interaction of cells of Helicobacter pylori with human polymorphonuclear leucocytes: possible role of haemagglutinins

The interaction of fluorescein isothiocyanate (FITC)-labelled cells of Helicobacter pylori with human polymorphonuclear leucocytes (PMNs) was studied. Two strains with surface haemagglutinins expressing different receptor specificity were used in order to decide if cell surface haemagglutinins of H. pylori may play a role in lectin-mediated binding to/uptake by phagocytes: (1) strain 17874 (NCTC 11637) which expresses sialic acid-specific haemagglutinin; and (2) strain 17875 (NCTC 11638) which expresses a sialic acid-independent haemagglutinin. Cells of strain 17874 were poorly attached to/ingested by PMNs compared to cells of strain 17875. Pre-treatment of bacteria with fetuin or rabbit antibodies against partly purified sialic acid-specific haemagglutinin enhanced interaction of cells of strain 17874 with PMNs. The enhancement did not occur in the case of strain 17875. Phagocytosis of H. pylori 17874 bacteria was slightly increased by fresh human sera positive for anti-H. pylori antibodies. The results suggest that the sialic acid-specific haemagglutinin complex of 17874 bacteria might disturb their uptake by human PMNs.

Attachment of Helicobacter pylori to human gastric epithelium mediated by blood group antigens

Helicobacter pylori is associated with development of gastritis, gastric ulcers, and adenocarcinomas in humans. The Lewis(b) (Le(b)) blood group antigen mediates H. pylori attachment to human gastric mucosa. Soluble glycoproteins presenting the Leb antigen or antibodies to the Leb antigen inhibited bacterial binding. Gastric tissue lacking Leb expression did not bind H. pylori. Bacteria did not bind to Leb antigen substituted with a terminal GalNAc alpha 1-3 residue (blood group A determinant), suggesting that the availability of H. pylori receptors might be reduced in individuals of blood group A and B phenotypes, as compared with blood group O individuals.

Adherence of Helicobacter pylori to primary human gastrointestinal cells

Helicobacter pylori adheres only to gastric cells in vivo. However, the organism adheres to a wide variety of nongastric cells in vitro. In this study, we have used flow cytometry to assess the adherence of H. pylori to primary epithelial cells isolated from gastric, duodenal, and colonic biopsy specimens by collagenase digestion. After incubation of bacteria and cells together and subsequent staining with a two-stage fluorescein isothiocyanate-labelled H. pylori antibody method, cells with adherent bacteria could be easily distinguished from cells without bacteria. Binding to Kato III cells (a gastric adenocarcinoma cell line) was saturable when bacteria and cells were mixed at a ratio of 250:1. Adherence to cells isolated from gastric biopsy specimens was significantly better than adherence to cells isolated from duodenal or colonic biopsy specimens. Almost 70% of gastric cells had bacteria bound, in contrast to 30% of duodenal cells and 32% of colonic cells (P < 0.0001). There was no correlation between expression of hemagglutinins by the bacteria and ability to bind to either Kato III cells or primary epithelial cells isolated from gastric biopsy specimens. In view of the strict tropism that the organism exhibits in vivo for gastric cells, the results of this study indicate that primary cells are ideal for assessing the factors that might play a role in the pathogenesis of disease caused by the organism.

Helicobacter pylori: microbiology of a 'slow' bacterial infection

The bacterium Helicobacter pylori lives in the gastric mucus layer of humans and induces a chronic inflammatory response that can result in both peptic ulceration and gastric neoplasms. Helicobacter pylori infection can be considered as a 'slow', adaptive and autoregulating process. The mechanisms by which this slow bacterial pathogen survives and interacts with the host immune system may provide a model for other persistent mucosal pathogens.

Adhesion of Helicobacter pylori to gastric epithelial cells in primary cultures obtained from stomachs of various animals

Of 35 strains of Helicobacter pylori tested, 5 were found to adhere well to HEp-2 cells. We selected three of these adhesive strains and four from the remaining strains to examine their ability to adhere to gastric epithelial cells in primary cultures obtained by collagenase digestion of stomachs from mice, rats, Mongolian gerbils, guinea pigs, pigs, and cynomolgus monkeys. The three adhesive strains adhered well to epithelial cells from monkey and pig gastric antra. The adhesion was inhibited by incubating the bacterial cells with fetuin, and this inhibition was further confirmed by the binding of gold-labeled fetuin to the surface of the adhesive strains. However, these adhesive strains only weakly adhered to fundic epithelial cells from monkeys and pigs and to gastric epithelial cells from the other animals. As for the four strains poorly adhesive to HEp-2 cells, they adhered weakly to gastric epithelial cells from all of the animals tested. They had higher hemagglutination titers than the adhesive strains, showing that there was no correlation between hemagglutination titers and the ability to adhere to gastric cells. Taking the similarities of human and monkey or pig stomachs into consideration, these results suggest that the primary target cell of H. pylori in colonization in human stomachs is the antral epithelial cell and that the putative adhesin involved in adhesion has affinity for fetuin.

Therapeutics used to alleviate peptic ulcers inhibit H. pylori receptor binding in vitro

Treatment with bismuth-containing remedies has been long associated with the alleviation of minor gastric ailments. Bismuth salts have a potent antimicrobial activity, and are part of the current standard regime used to treat Helicobacter pylori infection. H. pylori is considered to be the major etiological factor in the development of peptic ulcer disease. Earlier efficacious treatments for peptic ulcer included the oral administration of Tween detergents. We have found that these agents have an inhibitory effect on H. pylori adhesion to the lipid species phosphatidylethanolamine (PE) and gangliotetraosylceramide (Gg4) shown previously to be receptors for H. pylori binding in vitro. H. pylori binding to PE and Gg4 was inhibited after a thirty minute preincubation with different bismuth compounds: bismuth subsalicylate > bismuth subgallate > bismuth carbonate > colloidal bismuth subcitrate > tripotassium dicitrato bismuthate. No inhibitory effect on H. pylori binding was observed when bismuth salts were added directly into the binding assay. No changes in bacterial morphology and motility were observed after the thirty minute incubation. Pretreatment with Tween detergents also inhibited H. pylori receptor binding by up to 80% at concentrations as low as 0.0001%. These results suggest that inhibition of H. pylori/host cell adhesion might play a role in efficacious treatment for this infection.

Isolation of a sialic acid-specific surface haemagglutinin of Helicobacter pylori strain NCTC 11637

A deionized water extract of Helicobacter pylori NCTC 11637 contained haemagglutinin activity that was (i) soluble (i.e., not associated with particulate material sedimented by centrifugation at 100,000 x g for 1 h), (ii) stable to lyophilization, (iii) heat-labile, (iv) chymotrypsin-sensitive, (v) inhibited by fetuin, orosomucoid, and NANLac, but not by asialofetuin and (vi) inactive against guinea pig erythrocytes incubated with Clostridium perfringens neuraminidase, but active against untreated guinea pig erythrocytes. The data support the idea that the haemagglutinin is a protein which recognizes the alpha-(2-3) structure of sialylated glycoconjugates. Fractionation of the extract by isoelectric focusing and by gel filtration with Sephacryl S-400 indicated that the haemagglutinin has a pI of 3.7 and consist of high molecular-weight-protein aggregates. SDS-PAGE analysis of the preparation purified by gel filtration showed 3 protein bands at ca. 64 kD, 56 kD and 20 kD. Electron microscopy of H. pylori incubated with gold-labelled fetuin indicated that the haemagglutinin was associated with loosely adherent material on the bacterial surface, and that the purified haemagglutinin did not reveal a fimbrial structure. The ability to bind to sialoglycoconjugates on the erythrocyte membrane suggests that the haemagglutinin may be an important colonization factor enabling H. pylori to bind to similar saccharide structures on epithelial cells.

Adherence of haemagglutinating Helicobacter pylori to five cell lines

Helicobacter pylori causes gastritis and is an important factor for the development of peptic ulcer disease in man. We used two different methods to examine the adhesion of nine H. pylori strains, with different haemagglutinating properties, to five cell lines, HeLa S3, HFI, Vero, SW1222 and WEHI cells. The adhesion studies were performed a) as bacterial adhesion to a monolayer of tissue culture cells, visualizing bacteria with fluorescein-isothiocyanate-labelled antibodies, b) as cell agglutination with bacteria and eucaryotic cells mixed in a suspension. The H. pylori strains were divided into three groups according to their cell adhesion properties. In general, H. pylori strains which showed the best adhesion to the five cell lines were strains which showed the best capability of agglutinating erythrocytes of several animal species. It is likely that the same adhesins are involved in cell adhesion and in haemagglutination. The two methods gave similar results.

Rapid detection and characterization of sialic acid-specific lectins of Helicobacter pylori

A particle agglutination assay (PAA) using fetuin (Ft) covalently coupled to carboxylate-modified latex (CML) particles was evaluated for rapid detection of sialic acid-specific haemagglutinins/lectins (SALs) of Helicobacter pylori isolates which bind sialoglycoconjugates. Sixty-three percent (20/32) of the isolates examined gave a positive PAA test. Cell-bound SALs were extracted by washing the bacteria with deionized water or isotonic saline, and their expression was influenced by pH and culture conditions. The Ft-CML reactivity of the PAA-positive isolates was inhibited by bovine submaxillary mucin, transferrin, fetuin, orosomucoid, vitronectin and lactoferrin in a manner which suggested that the isolates contain a lectin recognizing the alpha(2-6) linkage of terminal sialic acid. Western blots of strain NCTC 11637 SALs probed with horseradish peroxidase (HRP)-labelled Ft identified three bands (MW 64 kD, 62 kD, 56 kD) which also reacted with HRP-labelled mucin, transferrin, lactoferrin, orosomucoid, vitronectin and laminin. Sera from patients with a H. pylori infection and one polyclonal rabbit antiserum (strain NCTC 11637) also reacted with the SALs. Immunogold labelling of a polyclonal rabbit antiserum raised against the 64 kD protein of strain NCTC 11637 that reacted strongly with Ft-CML showed that abundant SALs were loosely cell-associated with the cell surface of both spiral and coccoidal forms of H. pylori. SALs were also present in low amounts on the surface of strain NCTC 11638 and 66, a clinical isolate that did not react with Ft-CML.

Isolation and characterization of two Campylobacter glycine-extracted proteins that bind to HeLa cell membranes

Two immunogenic proteins of 27 (CBF1) and 29 (CBF2) kDa from enteropathogenic Campylobacter species appear to bind to mammalian cells. We purified these two proteins from a pathogenic and adherent Campylobacter jejuni strain to homogeneity by using acid extraction, preparative gel electrophoresis, and electroelution. Polyclonal rabbit antisera to these proteins were prepared. Immunologic studies indicate that CBF1 corresponds to the PEB1 and CBF2 corresponds to the PEB4 described by Pei et al. (Z. Pei, R. T. Ellison, and M. Blaser, J. Biol. Chem. 226:16363-16369, 1991). Immunogold labeling of a C. jejuni adherent strain with anti-CBF1, anti-CBF2, and anti-PEB1 suggested that CBF1 (PEB1) is surface exposed while CBF2 (PEB4) is not. Analysis of whole-cell extracts from 14 strains by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis with 7 M urea and immunoblotting with antisera to CBF1 and CBF2 suggests that CBF proteins from adherent and nonadherent strains are different. Use of purified proteins in a microassay of adherence to cellular membranes indicated that CBF1 was much more adherent than CBF2. Adherence of C. jejuni to viable HeLa cells was markedly reduced with the antiserum to CBF1, whereas the CBF2 antiserum was a poor inhibitor. Purified CBF1 competitively inhibited adherence of whole bacteria to HeLa cells, whereas purified CBF2 was no better a competitor than bovine serum albumin. Adherence of CBF2 was markedly reduced in the presence of Tween 20 or SDS, whereas adherence of CBF1 was reduced only by SDS. We conclude that (i) CBF1 (PEB1) is surface exposed and may be the key protein for C. jejuni adhesion and (ii) CBF2 (PEB4) may be complexed with CBF1 and may passively coadhere with CBF1 under certain experimental conditions. Adherent and nonadherent strains contain different isotypes of these two proteins which could be useful markers of C. jejuni adhesion.

Helicobacter mustelae and Helicobacter pylori bind to common lipid receptors in vitro

Helicobacter pylori is a recently recognized human pathogen causing chronic-active gastritis in association with duodenal ulcers and gastric cancer. Helicobacter mustelae is a closely related bacterium with similar biochemical and morphologic characteristics. H. mustelae infection of antral and fundic mucosa in adult ferrets causes chronic gastritis. An essential virulence property of both Helicobacter species is bacterial adhesion to mucosal surfaces. The aim of this study was to determine whether H. mustelae binds to the same lipids shown previously to be receptors for H. pylori adhesion in vitro. By using thin-layer chromatography overlay and a receptor-based enzyme-linked immunosorbent assay, H. mustelae was found to bind the same receptor lipids as H. pylori, namely, phosphatidylethanolamine and gangliotetraosylceramide. In addition, both H. pylori and H. mustelae bound to a deacylplasmalogen phosphatidylethanolamine. In contrast to H. pylori, H. mustelae binding to receptors was unaffected by motility or viability. Murine monoclonal and bovine polyclonal antibodies against exoenzyme S, and exoenzyme S itself (from Pseudomonas aeruginosa), inhibited binding of H. mustelae to phosphatidylethanolamine and gangliotetraosylceramide. These findings show that H. mustelae binds in vitro to the same lipid receptors as H. pylori and suggest that the adhesion of H. mustelae to such species is mediated by preformed, surface-exposed adhesins which include an exoenzyme S-like protein.

Receptor affinity purification of a lipid-binding adhesin from Helicobacter pylori

Our previous work has shown that Helicobacter pylori specifically recognizes gangliotetraosylceramide, gangliotriaosylceramide, and phosphatidylethanolamine in vitro. This binding specificity is shared by exoenzyme S from Pseudomonas aeruginosa, and monoclonal antibodies against this adhesin prevent the attachment of H. pylori to its lipid receptors. We now report the use of a novel, versatile affinity matrix to purify a 63-kDa exoenzyme S-like adhesin from H. pylori which is responsible for the lipid-binding specificity of this organism.