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Biomedical subjects

A P Moran

Publications and source records attributed to A P Moran.

At least 19 recordsLinked to original sources
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↗
PubMed1998

Simultaneous expression of type 1 and type 2 Lewis blood group antigens by Helicobacter pylori lipopolysaccharides. Molecular mimicry between h. pylori lipopolysaccharides and human gastric epithelial cell surface glycoforms.

Previous structural investigations performed on the lipopolysaccharides (LPSs) from the human gastric pathogen Helicobacter pylori have revealed that these cell surface glycan molecules express type 2 partially fucosylated, glucosylated, or galactosylated N-acetyllactosamine O antigen chains (O-chains) of various lengths, which may or may not be terminated at the nonreducing end by Lewis X (Lex) and/or Ley blood group epitopes in mimicry of human cell surface glycoconjugates and glycolipids. Subsequently, serological experiments with commercially available Lewis-specific monoclonal antibodies also have recognized the presence of Lex and Ley blood group antigens in H. pylori but, in addition, have indicated the presence of type 1 chain Lea, Leb, and Led (H-type 1) blood group epitopes in some H. pylori strains. To confirm their presence, structural studies and additional serological experiments were undertaken on H. pylori strains suspected of carrying type 1 chain epitopes. These investigations revealed that the O-chain region of H. pylori strain UA948 carried both Lea (type 1) and Lex (type 2) blood group determinants. The O-chain from H. pylori UA955 LPS expressed the terminal Lewis disaccharide (type 1 chain) and Lex and Ley antigens (type 2). The O-chain of H. pylori J223 LPS carried the type 1 chain precursor Lec, the H-1 epitope (Led, type 1 chain) and an elongated nonfucosylated type 2 N-acetyllactosamine chain (i antigen). Thus, O-chains from H. pylori LPSs can also express fucosylated type 1 sequences, and the LPS from a single H. pylori strain may carry O-chains with type 1 and 2 Lewis blood groups simultaneously. That monoclonal antibodies putatively specific for the Leb determinant can detect glycan substructures (Le disaccharide, Lec, and Led) of Leb indicates their nonspecificity. The expression of both type 1 and 2 Lewis antigens by H. pylori LPSs mimics the cell surface glycomolecules present in both the gastric superficial (which expresses mainly type 1 determinants) and the superficial and glandular epithelium regions (both of which express predominantly type 2 determinants). Therefore, each H. pylori strain may have a different niche within the gastric mucosa, and each individual LPS blood group antigen may have a dissimilar role in H. pylori adaptation.

Carbohydrate Sequence↗
PubMed1998

C7 deficiency in an Irish family: a deletion defect which is predominant in the Irish.

Human deficiencies of terminal complement components are known to be associated with increased susceptibility to Neisseria meningitidis infection. Polymorphic DNA marker studies in complement deficient investigations allow identification of haplotypes associated with the deficiency and enable the possible identification of heterozygote carriers of the defect. We report studies of an Irish family in which the index case had suffered recurrent meningococcal disease and was found to be deficient in the seventh component of complement (C7). The availability of all family members enabled us to determine the segregating haplotypes. The defects in the family segregated with two very closely related C6 and C7 DNA haplotypes, one of which is known to be associated with the large Irish C7 DNA deletion defect. The index case and two C7 deficient siblings were found to be homozygous for this defect, a deletion that spans approx. 6.8 kbp and encompasses exons 7 and 8. The deletion defect of exons 7 and 8 of C7 has been found in homozygous form in another C7 deficient Irish individual, and is present in heterozygous form in C7 deficient members of a third Irish family. Therefore, this deletion defect occurs in five of the six deficient chromosomes of these three unrelated Irish families, raising the interesting question of how prevalent this defect may be within the Irish community.

Blotting, Southern↗
PubMed1998

Effect of host Lewis and ABO blood group antigen expression on Helicobacter pylori colonisation density and the consequent inflammatory response.

The Lewis(b) blood group antigen has been implicated as a putative receptor for Helicobacter pylori in the gastric mucosa. Furthermore, an increased prevalence of duodenal ulcer was found in non-secretors and it has been suggested that secretor status may influence bacterial colonisation density. Other investigators have hypothesised that severity of antral gastritis may be related to colonisation density of the bacterium alone, and that a critical bacterial load is necessary for the development of duodenal ulcer. Our objectives were to investigate whether a relationship existed between host Lewis and ABO blood group phenotype and prevalence of H. pylori infection. In addition we investigated whether bacterial colonisation density and the ensuing inflammatory response was influenced by secretor status and ABO blood group phenotype. The Lewis and ABO blood group phenotype of 207 patients undergoing upper endoscopy was determined. Of these, 136 were secretors and 62 were nonsecretors. Forty-five percent of patients were infected with H. pylori. No significant association was found between H. pylori infection and expression of Lewis(a) or Lewis(b) blood group antigen. The mean histological density of H. pylori was 1.8 +/- 0.2 among non-secretors and 1.51 +/- 0.13 among secretors (P = 0.209), with a mean grade of lymphocytic infiltration significantly greater in H. pylori-infected non-secretors (2.23 +/- 0.123 vs 1.8 +/- 0.074; P = 0.003). In addition, blood group O non-secretors had a significantly higher grade of lymphocyte infiltration of their gastric mucosa compared to non-O non-secretors (2.53 +/- 0.133 vs 1.93 +/- 0.181, P = 0.027). These results suggest that although no in vivo relationship exists between H. pylori and preferential adhesion to the putative Lewis(b) receptor, bacterial colonisation and the ensuing inflammatory response may be influenced at least in part by host expression of ABO and Lewisa blood group antigens.

ABO Blood-Group System↗
PubMed1998

Lipopolysaccharides from Campylobacter jejuni O:41 strains associated with Guillain-Barré syndrome exhibit mimicry of GM1 ganglioside.

Three Campylobacter jejuni, biotype 2, serotype O:41 strains that were isolated from patients who developed Guillain-Barré syndrome (GBS) and one C. jejuni isolate from a patient who developed enteritis only were examined. The aim of the study was to determine the structure of the core oligosaccharide (OS) of the lipopolysaccharide (LPS) of C. jejuni serotype O:41, a serotype rarely associated with the development of GBS, and to determine if the LPS shares similar epitopes with any of the major human gangliosides. Electrophoretic analysis with silver staining or immunoblotting demonstrated that the strains had LPS profiles characteristic of low-molecular-weight LPS. Colorimetric analysis detected N-acetylneuraminic (sialic) acid in the core OSs of all the strains. Thin-layer chromatography with immunostaining showed that antisera raised against the GBS strains reacted with the GM1 ganglioside, suggesting that C. jejuni serotype O:41 LPSs and the GM1 ganglioside have similar epitopes. Furthermore, polyclonal anti-GM1 and anti-asialoGM1 antibodies cross-reacted with each C. jejuni O:41 LPS tested, suggesting that the serotype O:41 core OS has a GM1- and asialoGM1-like structure. LPSs extracted from C. jejuni serostrains O:2, O:3, and O:19 were also used in the study. Cholera toxin (a GM1 ligand) and peanut agglutinin (a Galbeta1-3GalNAc ligand) recognized all serotype O:41 LPSs and the serostrain O:2 LPS. Immunoadsorption results confirmed GM1 relatedness. Moreover, the core OS was isolated from a GBS-associated C. jejuni O:41 LPS by gel permeation chromatography. An analysis by gas-liquid chromatography (GLC), GLC-mass spectrometry, and nuclear magnetic resonance showed the core OS of one of the C. jejuni O:41 GBS isolates to have a tetrasaccharide structure consistent with GM1 mimicry.

Adult↗
PubMed1997

The O-specific polysaccharide chain of Campylobacter fetus serotype A lipopolysaccharide is a partially O-acetylated 1,3-linked alpha-D-mannan.

A polysaccharide fraction liberated from Campylobacter fetus subsp. fetus serotype A lipopolysaccharide by mild acid hydrolysis followed by gel-permeation chromatography contained a partially O-acetylated D-mannan chain, as an O-specific polysaccharide, with a core oligosaccharide attached. The structure of the polysaccharide was studied by O-deacetylation, methylation, and 1H- and 13C-NMR spectroscopy, including computer-assisted analysis of the 13C-NMR spectrum. A structure of -->3)-alpha-D-Manp2Ac-(1--> was established as the structure of the O-specific polysaccharide, the degree of O-acetylation of the mannose residues at position 2 being estimated as 80-90%. As judged by the ratio of mannose to core constituents, the D-mannan chain consists on average of 10-12 monosaccharide units.

Acetylation↗
PubMed1997

Molecular mimicry between Helicobacter pylori and the host.

Helicobacter pylori lipopolysaccharide (LPS) expresses Lewis x and Lewis y blood group antigens that are identical to those occurring in the human gastric mucosa. During infection, antibodies against LPS, which bind to host Lewis antigens, may be induced. These consequently recognize gastric glycoprotein targets and cause autoimmune inflammation.

Animals↗
PubMed1997

Influence of medium composition on the growth and antigen expression of Helicobacter pylori.

An evaluation of the ability of various solid and liquid media to support both growth and antigen expression, particularly lipopolysaccharide (LPS) expression, by Helicobacter pylori culture collection strains and clinical isolates was performed. Liquid-based basal media (brain heart infusion, Brucella broth, Mueller-Hinton broth and tryptone soya broth) supported the growth of strains, whereas solid basal media of the same formulation did not support growth. Optimal growth of all strains was obtained on solid and in liquid media containing blood. Supplemented solid media containing supplements other than blood supported growth but only to a small extent. In liquid media excluding blood, serum supplements enhanced growth and horse serum was found to be superior to fetal calf serum. In general, beta-cyclodextrin did not increase growth. Mueller-Hinton broth or tryptone soya broth containing horse serum and a nitrogen source such as yeast extract or proteose peptone no. 3 were found to give optimal growth of H. pylori in a blood-free environment. Strains after cultivation in liquid media, irrespective of composition, maintained production of high-molecular weight (mol. wt) LPS with an O side chain independent of medium composition, whereas subculturing on solid media resulted in production of low-mol. wt LPS. Expression of proteins differed in liquid and on solid media, particularly proteins of 57 and 60 kDa, but qualitatively no differences were observed upon supplementation of basal media.

Antigens, Bacterial↗
PubMed1997

Structure and conserved characteristics of Campylobacter jejuni lipopolysaccharides.

The lipid A component of Campylobacter jejuni lipopolysaccharides (LPSs) contains the same architectural principle as that found in other bacterial species; however, unlike the case with other bacterial species, the lipid A backbone of C. jejuni strains is composed of a phosphorylated beta(1'-6)-linked disaccharide containing 2,3-diamino-2,3-dideoxy-D-glucose and D-glucosamine as the major molecular species. Despite a backbone that differs structurally from that of classic enterobacterial lipid A, C. jejuni lipid A is antigenically similar to enterobacterial lipid A, and the respective LPSs have comparable endotoxic activities. Structural variability is greater in the core oligosaccharide than in lipid A of C. jejuni LPS. Nevertheless, the inner core oligosaccharides of C. jejuni strains share a common unique tetrasaccharide and also possess a trisaccharide that occurs in the inner core of other bacterial species. Ganglioside mimicry in the outer core is a common feature shared by a number of C. jejuni serotypes, but this mimicry is not conserved in all serotypes.

Campylobacter jejuni↗
PubMed1997

Serum antibodies against gangliosides and Campylobacter jejuni lipopolysaccharides in Miller Fisher syndrome.

Seven patients with Miller Fisher syndrome (MFS), six in the acute phase and one in the recovery phase, were investigated for serum antibodies against gangliosides and purified lipopolysaccharides (LPS) from different strains of Campylobacter jejuni, including the MFS-associated serotypes O:2 and O:23. Immunoglobulin G antibodies against gangliosides GT1a and GQ1b were found in five of six patients in the acute phase of disease. Three of these patients also displayed antibodies to ganglioside GD2, a finding not previously reported for MFS. All anti-GT1a- and anti-GQ1b-seropositive patients showed antibody binding to C. jejuni LPS, predominantly to O:2 and O:23 LPS. Antibody cross-reactivity between gangliosides GT1a and GQ1b and O:2 and O:23 LPS was demonstrated by adsorption studies. This cross-reactivity between gangliosides and C.jejuni LPS, which is obviously due to oligosaccharide homologies, may be an important pathogenetic factor in the development of MFS after C. jejuni infection.

Adult↗
PubMed1997

Identification of the N-acetylneuraminyllactose-specific laminin-binding protein of Helicobacter pylori.

The interaction of the gastroduodenal pathogen Helicobacter pylori with the glycoprotein laminin was investigated. Binding of 125I-radiolabelled laminin in a liquid-phase assay by both hemagglutinating and poorly hemagglutinating strains was rapid, saturable, specific, partially reversible, of high affinity, and insensitive to pH. Inhibition of laminin binding by fetuin, but not asialofetuin, and reduced bacterial binding to periodate- or sialidase-treated laminin indicated that glycosylation, particularly sialylation, was important for laminin binding by H. pylori. Inhibition experiments with monosaccharides, disaccharides, and trisaccharides showed that the strains bound to a region spanning a trisaccharide. In particular, inhibition and displacement studies showed that binding to the trisaccharide N-acetylneuraminyl-alpha(2-3)-lactose [NeuAc(2-3)Lac] was preferential to that to the NeuAc(2-6)Lac isomer. Complete inhibition of laminin binding by both hemagglutinating and poorly hemagglutinating strains was achieved only when isolated lipopolysaccharide (LPS) was used as an inhibitor in combination with heat or protease treatment of H. pylori cells, thereby confirming the involvement of both LPS and a protein adhesin in laminin binding. Further inhibition experiments indicated that the protein receptor, rather than LPS, on H. pylori bound NeuAc(2-3)Lac. By using a Western blotting procedure, a 25-kDa outer membrane protein was identified as mediating laminin binding by both hemagglutinating and poorly hemagglutinating H. pylori strains. The specificity of binding was confirmed by complete inhibition of laminin binding by the 25-kDa protein with NeuAc(2-3)Lac. The data collectively suggest that a 25-kDa outer membrane protein acts in a lectin-like manner with LPS to mediate attachment of H. pylori to laminin.

Adhesins, Bacterial↗