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A P Moran

Publications and source records attributed to A P Moran.

At least 19 recordsLinked to original sources
PubMed2000

Comparison of three serological methods for detection of Lewis antigens on the surface of Helicobacter pylori.

Chemical studies have shown that lipopolysaccharide (LPS) from certain strains of Helicobacter pylori expresses the Lewis (Le) blood group antigens, predominantly Le(x) and/or Le(y). Serological methods have been used in a number of studies to assess the level of Le expression by H. pylori. However, serological and chemical analyses of a strain's LPS do not always agree. The purpose of this study was to evaluate and compare serological methods used to detect the expression of these antigens by H. pylori. A set of 34 Irish clinical isolates and three culture collection strains had their Le antigen expression assessed using three serological methods, serodot, Western blotting and enzyme-linked immunosorbent assay. A combination of all three methods was used to estimate Le(x) (59%) and Le(y) (94%) expression and this may allow a more accurate assessment of Le expression by isolates for pathogenesis studies.

Blotting, Western↗
PubMed2000

Structure of an atypical O-antigen polysaccharide of Helicobacter pylori containing a novel monosaccharide 3-C-methyl-D-mannose.

Lipopolysaccharides (LPS) were isolated by hot phenol-water extraction from Danish Helicobacter pylori strains D1, D3, and D6, which were nontypeable using a variety of anti-Lewis and anti-blood-group monoclonal antibodies. An atypical O-chain polysaccharide (PS) was liberated from the LPS of the three strains by acid under mild conditions and found to contain D-rhamnose (D-Rha), L-rhamnose (L-Rha), and a branched sugar, 3-C-methyl-D-mannose (D-Man3CMe). The last sugar, which has not hitherto been found in Nature, was identified using GLC-MS of the derived alditol acetate and the partially methylated alditol acetate, and (1)H and (13)C NMR spectroscopy, including NOESY and (1)H,(13)C HMBC experiments. The following structure of the trisaccharide repeating unit of the PS was established: -->2)-alpha-D-Manp3CMe-(1-->3)-alpha-L-Rhap-(1-->3)-alpha-D- Rhap-(1-- >. In contrast to the pathogenic importance of the Lewis antigen mimicry exhibited by the PS of H. pylori strains previously investigated, the biological relevance of the atypical PS for H. pylori pathogenesis is unclear. The production of a differing surface PS may represent a form of antigenic variation by these particular H. pylori strains and/or may reflect the adaptation of these strains to a particular human population.

Acids↗
PubMed2000

Ganglioside-induced antiganglioside antibodies from a neuropathy patient cross-react with lipopolysaccharides of Campylobacter jejuni associated with Guillain-Barré syndrome.

Antiganglioside serum antibodies from a patient treated with gangliosides were examined for cross-reactivity with lipopolysaccharides (LPSs) of Campylobacter jejuni strains associated with Guillain-Barré syndrome (GBS). The patient had no preceding infection with C. jejuni and developed chronic progressive motor polyneuropathy following parenteral ganglioside treatment. Serum IgG antibodies recognised GM1 and GD1b gangliosides as well as asialo-GM1, and cross-reactivity was observed with LPSs from C. jejuni O:2, O:4, O:19 and O:41. The results give a clear indication that gangliosides and LPSs from C. jejuni serotypes associated with GBS share common epitopes.

Adult↗
PubMed2000

Cytotoxicity associated with induction of nitric oxide synthase in rat duodenal epithelial cells in vivo by lipopolysaccharide of Helicobacter pylori: inhibition by superoxide dismutase.

The products released by Helicobacter pylori (H. pylori) in the gastric antral and duodenal mucosa may be involved in mucosal ulceration by stimulating the local formation of cytotoxic factors such as nitric oxide (NO), superoxide or peroxynitrite. The present study investigates the ability of purified H. pylori lipopolysaccharide (LPS) to induce nitric oxide synthase (iNOS) in rat duodenal epithelial cells following in vivo challenge and its interaction with superoxide in promoting cellular damage and apoptosis. H. pylori LPS (0.75-3 mg kg(-1) i.v. or 3-12 mg kg(-1) p.o.) induced a dose - dependent expression of iNOS activity after 5 h in the duodenal epithelial cells, determined by [(14)C] arginine conversion to citrulline. The epithelial cell viability, as assessed by Trypan Blue exclusion and MTT conversion, was reduced 5 h after challenge with H. pylori LPS, while the incidence of apoptosis was increased. The iNOS activity and reduction in cell viability following H. pylori LPS challenge i.v. was inhibited by the selective iNOS inhibitor, 1400 W (0.2-5 mg kg(-1) i.v.). Concurrent administration of superoxide dismutase conjugated with polyethylene glycol (250 - 500 i.u. kg(-1), i.v.), which did not modify the cellular iNOS activity, reduced the epithelial cell damage provoked by i.v. H. pylori LPS, and abolished the increased incidence of apoptosis. These results suggest that expression of iNOS following challenge with H. pylori LPS provokes duodenal epithelial cell injury and apoptosis by a process involving superoxide, implicating peroxynitrite involvement. These events may contribute to the pathogenic mechanisms of H. pylori in promoting peptic ulcer disease.

Amidines↗
PubMed2000

Lewis X structures in the O antigen side-chain promote adhesion of Helicobacter pylori to the gastric epithelium.

Helicobacter pylori NCTC11637 expresses a lipopolysaccharide (LPS) that comprises an O antigen side-chain with structural homology to the human blood group antigen Lewis X (Le(x)). The role of this molecule in adhesion of H. pylori to gastric epithelial cells was investigated. Mutants expressing truncated LPS structures were generated through insertional mutagenesis of rfbM and galE; genes encode GDP mannose pyrophosphorylase and galactose epimerase respectively. Compositional and structural analysis revealed that the galE mutant expressed a rough LPS that lacked an O antigen side-chain. In contrast, an O antigen side-chain was still synthesized by the rfbM mutant, but it lacked fucose and no longer reacted with anti-Le(x) monoclonal antibodies (Mabs). The ability of these mutants to bind to paraffin-embedded sections from the antrum region of a human stomach was assessed. Adhesion of the wild type was characterized by tropic binding to the apical surface of mucosal epithelial cells and cells lining gastric pits. In contrast, both the rfbM and galE mutants failed to demonstrate tropic binding and adhered to the tissue surface in a haphazard manner. These results indicate that LPS and, more specifically, Le(x) structures in the O antigen side-chain play an important role in targeting H. pylori to specific cell lineages within the gastric mucosa. The role of Le(x) in this interaction was confirmed by the tropic binding of synthetic Le(x), conjugated to latex beads, to gastric tissue. The observed pattern of adhesion was indistinguishable from that of wild-type H. pylori.

Bacterial Adhesion↗
PubMed2000

Lipopolysaccharide structures of Helicobacter pylori genomic strains 26695 and J99, mouse model H. pylori Sydney strain, H. pylori P466 carrying sialyl Lewis X, and H. pylori UA915 expressing Lewis B classification of H. pylori lipopolysaccharides into glycotype families.

This study describes the molecular makeup of the cell-wall lipopolysaccharides (LPSs) (O-chain polysaccharide-->core oligosaccharide-->lipid A) from five Helicobacter pylori strains: H. pylori 26695 and J99, the complete genome sequences of which have been published, the established mouse model Sydney strain (SS1), and the symptomatic strains P466 and UA915. All chemical and serological experiments were performed on the intact LPSs. H. pylori 26695 and SS1 possessed either a low-Mr semi-rough-form LPS carrying mostly a single Ley type-2 blood-group determinant in the O-chain region covalently attached to the core oligosaccharide or a high-Mr smooth-form LPS, as did strain J99, with an elongated partially fucosylated type-2 N-acetyllactosamine (polyLacNAc) O-chain polymer, terminated mainly by a Lex blood-group determinant, connected to the core oligosaccharide. In the midst of semi-rough-form LPS glycoforms, H. pylori 26695 and SS1 also expressed in the O-chain region a difucosylated antigen, alpha-L-Fucp(1-3)-alpha-L-Fucp(1-4)-beta-D-GlcpNAc, and the cancer-cell-related type-1 or type-2 linear B-blood-group antigen, alpha-D-Galp(1-3)-beta-D-Galp(1-3 or 4)-beta-D-GlcpNAc. The LPS of H. pylori strain P466 carried the cancer-associated type-2 sialyl Lex blood-group antigen, and the LPS from strain UA915 expressed a type-1 Leb blood-group unit. These findings should aid investigations that focus on identifying and characterizing genes responsible for LPS biosynthesis in genomic strains 26695 and J99, and in understanding the role of H. pylori LPS in animal model studies. The LPSs from the H. pylori strains studied to date were grouped into specific glycotype families.

Animals↗
PubMed2000

Biological activities of lipopolysaccharides are determined by the shape of their lipid A portion.

Lipopolysaccharide (LPS) represents a major virulence factor of Gram-negative bacteria ('endotoxin') that can cause septic shock in mammals including man. The lipid anchor of LPS to the outer membrane, lipid A, has a peculiar chemical structure, harbours the 'endotoxic principle' of LPS and is responsible for the expression of pathophysiological effects. Chemically modified lipid A can be endotoxically inactive, but may express strong antagonistic activity against LPS, a property that can be utilized in antisepsis treatment. We show here that these different biological activities are directly correlated with the molecular shape of lipid A. Only (hexaacyl) lipid A with a conical/concave shape, the cross-section of the hydrophobic region being larger than that of the hydrophilic region, exhibited strong interleukin-6 (IL-6)-inducing capacity. Most strikingly, a correlation between a cylindrical molecular shape of lipid A and antagonistic activity was established: IL-6 induction by enterobacterial LPS was inhibited by cylindrically shaped lipid A except for compounds with reduced headgroup charge. The antagonistic action is interpreted by assuming that lipid A molecules intercalate into the cytoplasmic membrane of mononuclear cells, and subsequently blocking of the putative signaling protein by the lipid A with cylindrical shape.

Carbohydrate Sequence↗
PubMed2000

Genotyping of cagA and vacA, Lewis antigen status, and analysis of the poly-(C) tract in the alpha(1,3)-fucosyltransferase gene of Irish Helicobacter pylori isolates.

Much work has focused on trying to identify markers in Helicobacter pylori that might allow the eventual disease outcome of an infection to be predicted. In this study we examined the cagA and vacA genotype, and Lewis status in a panel of 43 Irish H. pylori clinical isolates, and investigated a possible correlation with disease pathology. In addition, differences in the poly-(C) tract of the alpha(1,3)-fucosyltransferase gene were examined to identify a possible correlation with gene expression. Only three of 43 isolates were cagA-negative, whereas the remaining 40 isolates, independent of pathology, were cagA-positive. In all the strains we examined, the vacA signal-sequence was type s1a. For the vacA mid-region 12/43 isolates were type m1 and 31/43 isolates were type m2. These data, and examination of isolates from different pathology groups, suggests that there is no correlation between virulence and vacA genotype in the Irish population of H. pylori isolates. Western blotting of whole cell lysates from 32 H. pylori isolates showed 3/32 displayed only the Le(x) epitope, 12/32 only the Le(y), 13/32 both epitopes and 4/32 neither epitope. No apparent association between Lewis phenotype and disease pathology was evident. A range of lengths of poly-(C) tract were observed in the alpha(1, 3)-fucosyltransferase gene, however the length of the tract in an isolate did not correlate with the Lewis structures present. We conclude that future studies on H. pylori pathogenesis should not alone focus on the importance of molecular markers, but also on the host response, including genetic background and immune responsiveness.

Antigens, Bacterial↗
PubMed2000

Relationship of blood group determinants on Helicobacter pylori lipopolysaccharide with host lewis phenotype and inflammatory response.

As Lewis a (Le(a)) and Lewis b (Le(b)) blood group antigens are isoforms of Lewis x (Le(x)) and Lewis y (Le(y)) and are expressed in the gastric mucosa, we evaluated whether the patterns of expression of Le(x) and Le(y) on Helicobacter pylori lipopolysaccharides reflected those of host expression of Le(a) and Le(b). When 79 patients (secretors and nonsecretors) were examined for concordance between bacterial and host Le expression, no association was found (chi(2) = 5.734, 3 df, P = 0.125), nor was there a significant difference between the amount of Le(x) or Le(y) expressed on isolates from ulcer and chronic gastritis patients (P > 0.05). Also, the effect of host and bacterial expression of Le antigens on bacterial colonization and the observed inflammatory response was assessed. In ulcer patients, Le(x) expression was significantly related to neutrophil infiltration (r(s) = 0.481, P = 0.024), whereas in chronic gastritis patients significant relationships were found between Le(x) expression and H. pylori colonization density (r(s) = 0.296, P = 0.03), neutrophil infiltrate (r(s) = 0.409, P = 0. 001), and lymphocyte infiltrate (r(s) = 0.389, P = 0.002). Furthermore, bacterial Le(y) expression was related to neutrophil (r(s) = 0.271, P = 0.033) and lymphocyte (r(s) = 0.277, P = 0.029) infiltrates. Thus, although no evidence of concordance was found between bacterial and host expression of Le determinants, these antigens may be crucial for bacterial colonization, and the ensuing inflammatory response appears, at least in part, to be influenced by Le antigens.

Adolescent↗
PubMed1999

Chemical structure of a polysaccharide from Campylobacter jejuni 176.83 (serotype O:41) containing only furanose sugars.

A neutral polysaccharide was obtained by hot phenol-water extraction of biomass from Campylobacter jejuni 176.83 and subsequently separated from acid-liberated core oligosaccharide of lipopolysaccharide by sequential GPC on Bio-Gel P6 and TSK-40 columns. All sugar components of the trisaccharide repeating unit of the polysaccharide were found to be of the furanose ring form. The major trisaccharide contained beta-L-arabinose, 6-deoxy-beta-D-altro-heptose (beta-D-6d-altHep) and 6-deoxy-beta-L-altrose (beta-L-6d-Alt), whereas in the minor trisaccharide the beta-L-6d-Alt is replaced by its C-5 epimer alpha-D-Fuc. On the basis of 1H and 13C NMR spectroscopic studies, including 2D ROESY, HMQC and HMQC-TOCSY experiments, the following structures of the repeating units were established: [formula: see text]

Campylobacter jejuni↗
PubMed1999

Structural studies on lipopolysaccharides of serologically non-typable strains of Helicobacter pylori, AF1 and 007, expressing Lewis antigenic determinants.

In contrast to other Helicobacter pylori strains, which have serologically detectable Lewis(x)+ (Le(x)) and Lewis(y)++ (++Le(y)) antigenic determinants in the O-specific polysaccharide chains of the lipopolysaccharides, H. pylori AF1 and 007 were non-typable with anti-Le(x) and anti-Le(y) antibodies. The carbohydrate portions of the lipopolysaccharides were liberated by mild acid hydrolysis and subsequently studied by sugar and methylation analyses, 1H-NMR spectroscopy and electrospray ionization-mass spectrometry. Compared with each other, and with lipopolysaccharides of strains studied previously, the lipopolysaccharides of both AF1 and 007 showed similarities, but also differences, in the structures of the core region and O-specific polysaccharide chains. The O-specific polysaccharide chains of both strains consisted of a short or long polyfucosylated poly-N-acetyl-beta-lactosamine chains, which were distinguished from those of other strains by a high degree of fucosylation producing a polymeric Le(x)chain terminating with Le(x) or Le(y) units:[sequence: see text] where n = 0 or 1 in strain AF1 and 0 in strain 007, m = 0-2, 6-7 in strain AF1 and m = 0-2, 6-7 or approximately 40 in strain 007, the medium-size species being predominant. Therefore, compared with other strains, the lack of reactivity of lipopolysaccharide of H. pylori AF1 and 007 with anti-Le(x) and anti-Le(y) may reflect the presence of a polymeric Le(x) chain and has important implications for serological and pathogenesis studies. As the substitution pattern of a D-glycero-D-manno-heptose residue in the outer core varied in the two strains, and an extended DD-heptan chain was present in some lipopolysaccharide species but not in others, this region was less conservative than the inner core region. The inner core L-glycero-D-manno-heptose region of both strains carried a 2-aminoethyl phosphate group, rather than a phosphate group, as reported previously for other H. pylori strains.

Antigens, Bacterial↗
PubMed1999

Ganglioside GM1 mimicry in Campylobacter strains from sporadic infections in the United States.

To determine whether GM1-like epitopes in Campylobacter species are specific to O serotypes associated with Guillain-Barré syndrome (GBS) or whether they are frequent among random Campylobacter isolates causing enteritis, 275 random enteritis-associated isolates of Campylobacter jejuni were analyzed. To determine whether GM1-like epitopes in Campylobacter species are specific to O serotypes associated with Guillan-Barre syndrome (GBS) or whether they are frequent among random Campylobacter isolates causing enteritis, 275 enteritis-associated isolates, randomly collected in the United States, were analyzed using a cholera-toxin binding assay [corrected]. Overall, 26.2% of the isolates were positive for the GM1-like epitope. Of the 36 different O serotypes in the sample, 21 (58.3%) contained no strains positive for GM1, whereas in 6 serotypes (16.7%), >50% of isolates were positive for GM1. GBS-associated serotypes were more likely to contain strains positive for GM1 than were non-GBS-associated serotypes (37.8% vs. 15.1%, P=.0116). The results suggest that humans are frequently exposed to strains exhibiting GM1-like mimicry and, while certain serotypes may be more likely to possess GM1-like epitopes, the presence of GM1-like epitopes on Campylobacter strains does not itself trigger GBS.

Campylobacter Infections↗
PubMed1999

A structural comparison of lipopolysaccharides from two strains of Helicobacter pylori, of which one strain (442) does and the other strain (471) does not stimulate pepsinogen secretion.

Lipopolysaccharides (LPSs) from strains of Helicobacter pylori (442 and 471), which differed in stimulation of pepsinogen secretion, were isolated as water-soluble material of high-M(r), and as water-insoluble gels of low-M(r). Chemical and spectroscopic analyses of soluble LPS and oligosaccharides liberated from the gels led to proposed structures with Lewis (Le) antigen termini connected to N -acetyllacto-saminoglycans of alternating 3-linked beta-D-Gal and 4-linked beta-D-GlcNAc residues with various laterally attached glycosyl substituents. The LPS of H.pylori 442 was similar to previously examined strains (NCTC 11637 and P466) in having partially glycosylated chains with alpha-L-Fuc units attached to O-3 of the majority of GlcNAc residues in Le(x)units, and in chain termination with Le(x)or Le(y)determinants. In contrast, terminal Le(y)units occurred in LPS of H.pylori 471 and glycosaminoglycan chains carried a smaller proportion of alpha-L-Fuc units, but at O-6 of a majority of nonfucosylated GlcNAc residues, there was a novel type of branching with alpha-D-Gal substituents. Evidence for the branched regions was obtained from(1)H-NMR spectra and from characterization of oligosaccharides formed by the action of endo-beta-galactosidase. Examination of oligosaccharides liberated from water-insoluble LPS gels of H.pylori 442 and 471 provided evidence for similar core OS structures to those from other H.pylori strains but interesting differences were observed.

Antigens, Bacterial↗
PubMed1999

Lack of a relationship between Lewis antigen expression and cagA, CagA, vacA and VacA status of Irish Helicobacter pylori isolates.

The cagA gene, vacA gene, CagA (cytotoxin-associated gene A product) and VacA (vacuolating cytotoxin) status of a collection of Helicobacter pylori isolates from the geographically distinct Irish population was determined, the potential association of these traits with Lewis (Le) antigen expression was assessed, and the relationship between these bacterial properties and the pathology associated with H. pylori infection was evaluated. Of the 57 isolates, a higher proportion from ulcer than from non-ulcer patients expressed VacA (71% vs. 53%). H. pylori isolates which were cagA-positive were no more significantly associated with peptic ulcers than non-ulcer disease (71% vs. 67%, P = 0.775), nor were CagA-positive isolates (57% vs. 50%, P = 0.783), but 80% of the isolates from duodenal ulcer patients were cagA-positive. Thirty-seven of the 57 isolates were tested for Le antigen expression. No statistically significant relationship (P > 0.05) was found between the occurrence and level of expression of Le(x) or Le(y) and cagA, vacA, or VacA status. This lack of an association in the Irish H. pylori isolates contrasts with that previously reported for predominantly North American isolates, and may be attributable to the adaptation of H. pylori strains with differing attributes to different human populations.

Antigens, Bacterial↗
PubMed1999

Human monoclonal immunoglobulin M antibodies to ganglioside GM1 show diverse cross-reactivities with lipopolysaccharides of Campylobacter jejuni strains associated with Guillain-Barré syndrome.

We examined the reactivity of a panel of anti-GM1 immunoglobulin M monoclonal antibodies (MAbs) cloned from multifocal motor neuropathy patients with lipopolysaccharides (LPSs) of Campylobacter jejuni strains, including serotype O:41 strains associated with Guillain-Barré syndrome. The MAbs reacted with ganglioside GM1 to different degrees, and these differences in fine specificities for GM1 were reflected in the different degrees of reactivity with each of the C. jejuni LPSs tested. Antibodies could also be discriminated by the varying patterns of inhibition by cholera toxin (a GM1 ligand) in LPS binding studies. These results indicate that there is a substantial heterogeneity among C. jejuni O:41 strains in their expression of GM1-like epitopes and among the fine specificities of different neuropathy-associated anti-GM1 antibodies.

Antibodies, Bacterial↗
PubMed1999

Differentiation of Helicobacter pylori isolates based on lectin binding of cell extracts in an agglutination assay.

Plant and animal lectins with various carbohydrate specificities were used to type 35 Irish clinical isolates of Helicobacter pylori and the type strain NCTC 11637 in a microtiter plate assay. Initially, a panel of eight lectins with the indicated primary specificities were used: Anguilla anguilla (AAA), Lotus tetragonolobus (Lotus A), and Ulex europaeus I (UEA I), specific for alpha-L-fucose; Solanum tuberosum (STA) and Triticum vulgaris (WGA), specific for beta-N-acetylglucosamine; Glycine max (SBA), specific for beta-N-acetylgalactosamine; Erythrina cristagali (ECA), specific for beta-galactose and beta-N-acetylgalactosamine; and Lens culinaris (LCA), specific for alpha-mannose and alpha-glucose. Three of the lectins (SBA, STA, and LCA) were not useful in aiding in strain discrimination. An optimized panel of five lectins (AAA, ECA, Lotus A, UEA I, and WGA) grouped all 36 strains tested into eight lectin reaction patterns. For optimal typing, pretreatment by washing bacteria with a low-pH buffer to allow protein release, followed by proteolytic degradation to eliminate autoagglutination, was used. Lectin types of treated samples were stable and reproducible. No strain proved to be untypeable by this system. Electrophoretic and immunoblotting analyses of lipopolysaccharides (LPSs) indicated that the lectins interact primarily, but not solely, with the O side chain of H. pylori LPS.

Agglutination Tests↗