Marguerite Clyne

Association of symptoms with Helicobacter pylori infection in children

The aim of this study was to determine prospectively whether Helicobacter pylori-associated gastritis is associated with specific symptoms by evaluating whether these symptoms are relieved by treatment of the infection. Symptoms resolved after the eradication of H. pylori in only three of eight children with H. pylori-associated gastritis alone, in comparison with all six children with duodenal ulcer disease.

Molecular mechanisms of gastric epithelial cell adhesion and injection of CagA by Helicobacter pylori

Helicobacter pylori is a highly successful pathogen uniquely adapted to colonize humans. Gastric infections with this bacterium can induce pathology ranging from chronic gastritis and peptic ulcers to gastric cancer. More virulent H. pylori isolates harbour numerous well-known adhesins (BabA/B, SabA, AlpA/B, OipA and HopZ) and the cag (cytotoxin-associated genes) pathogenicity island encoding a type IV secretion system (T4SS). The adhesins establish tight bacterial contact with host target cells and the T4SS represents a needle-like pilus device for the delivery of effector proteins into host target cells such as CagA. BabA and SabA bind to blood group antigen and sialylated proteins respectively, and a series of T4SS components including CagI, CagL, CagY and CagA have been shown to target the integrin β1 receptor followed by injection of CagA across the host cell membrane. The interaction of CagA with membrane-anchored phosphatidylserine may also play a role in the delivery process. While substantial progress has been made in our current understanding of many of the above factors, the host cell receptors for OipA, HopZ and AlpA/B during infection are still unknown. Here we review the recent progress in characterizing the interactions of the various adhesins and structural T4SS proteins with host cell factors. The contribution of these interactions to H. pylori colonization and pathogenesis is discussed.

Absence of effect of Lewis A and Lewis B expression on adherence of Helicobacter pylori to human gastric cells

BACKGROUND & AIMS Lewis b blood group antigen and antibodies to Lewis b inhibit the binding of stationary-phase Helicobacter pylori organisms to fixed sections of gastric tissue. The aim of this study was to determine the effect of expression of Lewis a and Lewis b on binding of H. pylori to primary gastric cells. METHODS ABO and Lewis blood types were determined for 13 individuals. Cells were isolated from gastric biopsy specimens by collagenase digestion. Lewis antigen expression and adherence of H. pylori to the cells were quantitated using flow cytometry. RESULTS Two of the three nonsecretors were found to express Lewis b on their cells. Nineteen of 19 individuals expressed Lewis a on their cells and 18 of 19 expressed Lewis b. The percentage of cells expressing Lewis antigens varied from individual to individual. H. pylori binding was independent of expression of Lewis antigens. Preincubation of cells with antibodies to Lewis antigens did not inhibit the adherence. CONCLUSIONS H. pylori adheres to isolated human gastric cells in a manner that is not dependent on Lewis antigen expression on these cells, and expression of Lewis antigens on the surface of gastric cells is not dependent on Lewis antigen expression on erythrocytes.

Interaction of Cryptosporidium hominis and Cryptosporidium parvum with Primary Human and Bovine Intestinal Cells

ABSTRACT Cryptosporidiosis in humans is caused by the zoonotic pathogen Cryptosporidium parvum and the anthroponotic pathogen Cryptosporidium hominis. To what extent the recently recognized C. hominis species differs from C. parvum is unknown. In this study we compared the mechanisms of C. parvum and C. hominis invasion using a primary cell model of infection. Cultured primary bovine and human epithelial intestinal cells were infected with C. parvum or C. hominis. The effects of the carbohydrate lectin galactose-N-acetylgalactosamine (Gal/GalNAc) and inhibitors of cytoskeletal function and signal transduction mechanisms on entry of the parasites into host cells were tested. HCT-8 cells (human ileocecal adenocarcinoma cells) were used for the purpose of comparison. Pretreatment of parasites with Gal/GalNAc inhibited entry of C. parvum into HCT-8 cells and primary bovine cells but had no effect on entry of either C. parvum or C. hominis into primary human cells or on entry of C. hominis into HCT-8 cells. Both Cryptosporidium species entered primary cells by a protein kinase C (PKC)- and actin-dependent mechanism. Staurosporine, in particular, attenuated infection, likely through a combination of PKC inhibition and induction of apoptosis. Diversity in the mechanisms used by Cryptosporidium species to infect cells of different origins has important implications for understanding the relevance of in vitro studies of Cryptosporidium pathogenesis.

Helicobacter pylori lipopolysaccharide interacts with TFF1 in a pH-dependent manner.

BACKGROUND & AIMS Little is known about how bacteria establish chronic infections of mucosal surfaces. Helicobacter pylori (H. pylori), a chronic pathogen that lives in the gastric mucosa of humans, interacts with the trefoil factor family (TFF) protein TFF1, which is found in gastric mucus. We aimed to characterize the interaction of H. pylori with TFF1 and to assess the role of this interaction in mediating colonization. METHODS Subcellular fractions of H. pylori were immobilized and then probed with TFF1, TFF2, or TFF3. The effect of glycosidases and preincubation with monosaccharides on the interaction and binding of TFF1 to a H. pylori adhesin was assessed. The interaction between H. pylori adhesin and TFF1 was characterized using surface plasmon resonance, flow cytometry, nondenaturing polyacrylamide gel electrophoresis, coimmunofluoresence, and incubation with tissue sections. RESULTS The H. pylori core oligosaccharide portion (rough form) of lipopolysaccharide (RF-LPS) bound to TFF1 and to a lesser extent TFF3; this interaction was inhibited by incubation of RF-LPS with mannosidase, glucosidase, or mixed monosaccharides. TFF1 also bound to human serum albumin-conjugated mannose and glucose. The optimum pH for binding was 5.0-6.0 for TFF1 and 7.0 for TFF3. H. pylori bound TFF1 in gastric mucus ex vivo; binding of LPS-coated latex beads to human antral gastric tissue was inhibited by TFF1. CONCLUSIONS TFF1 interacts specifically with H. pylori RF-LPS. The pH dependence of this interaction indicates that binding of H. pylori to TFF1 in the stomach could promote colonization of the mucus layer adjacent to the gastric epithelial surface.

Effect of Helicobacter pylori eradication on the natural history of duodenal ulcer disease

BACKGROUND Duodenal ulcer disease is strongly associated with Helicobacter pylori infection of the gastric mucosa. Eradication of H pylori from the gastric mucosa in adults is associated with long term healing of ulcers. AIMS To follow a cohort of children with duodenal ulcer disease for a minimum of two years after the eradication ofH pylori. PATIENTS AND METHODS Over a three year period, all children diagnosed with duodenal ulcer disease had their symptoms documented and their H pylori status evaluated. The histories of these children were carefully screened to determine previous symptoms and to document previous treatment regimens. RESULTS Sixteen children were diagnosed with ulcers and 15 were available for treatment and long term follow up. The median age at which symptoms first occurred was 10.5 years (range, 6–14) and the median duration of symptoms was 24 months (range, 2–60). Ten of the children had been treated with H2receptor antagonists for a median of 3.5 months (range, 1–60). Duodenal ulcers healed in all children after eradication of H pylori and all children have remained asymptomatic for a median of 37 months (range, 26–62). No child has required subsequent admission to hospital. CONCLUSION Eradication of H pylori is very effective in the long term healing of duodenal ulcer disease.H pylori eradication should be the standard treatment for all infected children who present with duodenal ulcer disease.

Pathogenesis of Helicobacter pylori Infection: H. pylori Pathogenesis

Helicobacter pylori infections and clinical outcome are dependent on sophisticated interactions between the bacteria and its host. Crucial bacterial factors associated with pathogenicity comprise a type IV secretion system encoded by the cag pathogenicity island, the effector protein CagA, the vacuolating cytotoxin (VacA), peptidoglycan, lipopolysaccharide (LPS), γ‐glutamyl transpeptidase (GGT), protease HtrA, and the adhesins BabA, SabA, and others. The high number of these factors and allelic variation of the involved genes generates a highly complex scenario and reveals the difficulties in testing the contribution of each individual factor. Much effort has been put into identifying the molecular mechanisms associated with H. pylori‐associated pathogenesis using human primary tissues, Mongolian gerbils, transgenic, knockout, and other mice as well as in vitro cell model systems. Interactions between bacterial factors and host signal transduction pathways seem to be critical for mediating the induction of pathogenic downstream processes and disease development. In this review article, we discuss the most recent progress in this research field.

Comparative chemical and biological characterization of the lipopolysaccharides of gastric and enterohepatic helicobacters

Background.  The lipopolysaccharide of Helicobacter pylori plays an important role in colonization and pathogenicity. The present study sought to compare structural and biological features of lipopolysaccharides from gastric and enterohepatic Helicobacter spp. not previously characterized.

Campylobacter upsaliensis exerts a cytolethal distending toxin effect on HeLa cells and T lymphocytes

Campylobacter upsaliensis is an emerging human enteropathogen. However, little is known about the pathogenesis of C. upsaliensis infection. In this study the authors demonstrate that C. upsaliensis whole-cell preparations and extracts produce a cytolethal distending toxin (CDT)-like effect on HeLa cells characterized by progressive distension and nuclear fragmentation culminating in cell death over 5 d. To further delineate the nature of this toxic effect in relation to CDT from other pathogens, the effect of C. upsaliensis on cellular events in epithelial cells and immunocytes was investigated. C. upsaliensis lysate-treated HeLa cells subjected to FACScan analysis using carboxyfluorescein diacetete succinimidyl ester (CFDA-SE) as a cell tracer demonstrated cell division arrest. Propidium iodide (PI) staining of HeLa cells revealed that cell cycle arrest occurred in G(2)/M. Human T lymphocytes exposed to C. upsaliensis lysates also showed cell cycle arrest in G(2)/M. Using a combination of Annexin V/PI staining and TUNEL assay, cytodistended HeLa cells were shown to undergo apoptotic cell death. These data provide the first insights into the virulence mechanisms of this novel enteropathogen.

Molecular mimicry of ferret gastric epithelial blood group antigen A by Helicobacter mustelae

BACKGROUND & AIMS Molecular mimicry of Lewis blood group antigens by Helicobacter pylori may be involved in immune evasion by the bacteria and in the pathogenesis of chronic atrophic gastritis. Helicobacter mustelae infects ferrets naturally, causing gastritis, and may be involved in ulcerogenesis. The aim of this study was to determine if H. mustelae shows a similar form of molecular mimicry. METHODS Antibodies raised against H. mustelae were used to stain ferret gastric tissue by immunoblotting, immunohistochemistry, and flow cytometry. Epitopes recognized by cross-reactivity were characterized by proteinase K and sodium metaperiodate treatment. RESULTS H. mustelae antiserum reacted with H. mustelae and with ferret gastric tissue. Absorption of the antiserum with H. mustelae or ferret and rabbit gastric tissue removed the cross-reactive antibodies. Antibodies reacted with a blood group antigen A-like structure on ferret gastric epithelial cells and H. mustelae lipopolysaccharide. CONCLUSIONS H. mustelae expresses a blood group-like antigen as part of its lipopolysaccharide that may be used as a method of immune evasion by mimicry of gastric epithelial cells. The cross-reactivity shown by H. mustelae-specific antibodies with gastric mucosa may suggest a role for autoantibodies in the pathogenesis of H. mustelae-induced gastritis in ferrets.