Occurrence of a nontypable Helicobacter pylori strain lacking Lewis blood group O antigens and DD-heptoglycan: evidence for the role of the core alpha1,6-glucan chain in colonization

The cell envelope of Helicobacter pylori contains a lipopolysaccharide (LPS) essential for the physical integrity and functioning of the bacterial cell membrane. The O-chain of this LPS frequently expresses type 2 Lewis x (Lex) and Lewis y (Ley) blood group antigens that mimic human gastric mucosal cell-surface glycoconjugates. This article describes the isolation and structural analysis of the LPS from a clinical isolate of H. pylori strain PJ2 that lacks Le antigens but is still capable of colonization. Subsequent composition, methylation, and CE-ESMS analyses of LPS revealed its core oligosaccharide structure to be consistent with the previously proposed structural model for H. pylori LPS. In addition, it carries an unusually long side branch alpha1,6-glucan and was devoid of Le O-chain polysaccharide. Its ability to colonize the mouse stomach was essentially identical to that of DD-heptoglycan- and Le antigen- producing H. pylori strains.     

Helicobacter pylori from asymptomatic hosts expressing heptoglycan but lacking Lewis O-chains: Lewis blood-group O-chains may play a role in Helicobacter pylori induced pathology.

Helicobacter pylori is a widespread Gram-negative bacterium responsible for the onset of various gastric pathologies and cancers in humans. A familiar trait of H. pylori is the production of cell-surface lipopolysaccharides (LPSs; O-chain --> core --> lipid A) with O-chain structures analogous to some mammalian histo-blood-group antigens, those being the Lewis determinants (Lea, Leb, Lex, sialyl Lex, Ley) and blood groups A and linear B. Some of these LPS antigens have been implicated as autoimmune, adhesion, and colonization components of H. pylori pathogenic mechanisms. This article describes the chemical structures of LPSs from H. pylori isolated from subjects with no overt signs of disease. Experimental data from chemical- and spectroscopic-based studies unanimously showed that these H. pylori manufactured extended heptoglycans composed of 2- and 3-linked D-glycero-alpha-D-manno-heptopyranose units and did not express any blood-group O-antigen chains. The fact that another H. pylori isolate with a similar LPS structure was shown to be capable of colonizing mice indicates that H. pylori histo-blood-group structures are not an absolute prerequisite for colonization in the murine model also. The absence of O-chains with histo-blood groups may cause H. pylori to become inept in exciting an immune response. Additionally, the presence of elongated heptoglycans may impede exposure of disease-causing outer-membrane antigens. These factors may render such H. pylori incapable of creating exogenous contacts essential for pathogenesis of severe gastroduodenal diseases and suggest that histo-blood groups in the LPS may indeed play a role in inducing a more severe H. pylori pathology.     

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.     

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.     

Histochemical localization and analysis of blood group-related antigens in human pancreas using immunostaining with monoclonal antibodies and exoglycosidase digestion

We examined the distribution of blood group-related antigens using an indirect immunoperoxidase method with monoclonal antibodies (MAb) directed to A, B, H, Lewis a (Lea), Lewis b (Leb), Lewis x (Lex), and Lewis y (Ley) antigens and Type 1 precursor chain in human pancreas. Effects of prior digestion with exoglycosidases on MAb stainings were simultaneously investigated. A, B, H, Leb, and Ley antigens were detected in acinar cells and interlobular duct cells but not in centroacinar cells, intercalated duct cells, and islet of Langerhans cells. The expression of these antigens in acinar cells was not dependent on Lewis type and secretor status of the tissue donors, whereas that in interlobular duct cells was strictly dependent on secretor status. The distribution pattern of these antigens in acinar cells was not homogeneous, i.e., cells producing H antigens expressed both Leb and Ley antigens but not A or B antigens, whereas those producing A or B antigens did not secrete Leb and Ley as well as H antigens. Digestion with alpha-N-acetylgalactosaminidase or alpha-galactosidase resulted in the appearance of Leb and Ley antigens as well as H antigen in acinar cells producing A and/or B antigens. Type 1 precursor chain was not detected in pancreatic tissues from secretors but appeared in acinar cells producing H antigen after alpha-L-fucosidase digestion, which also disclosed Lex but not Lea antigen in acinar cells expressing both Leb and Ley. In some non-secretors, MAb against Type 1 precursor chain reacted with acinar cells without enzyme digestion. Although Lea antigen was not detected in acinar cells, it was found in centroacinar cells, intercalated duct cells, and interlobular duct cells from all individuals examined except two Le(a-b-) secretors. After sialidase digestion, Lex antigen appeared in centroacinar and intercalated duct cells from some individuals. Sialidase digestion also elicited reactivity with MAb against Type 1 precursor chain in islet of Langerhans cells from some individuals. These results demonstrate the complexity in the pattern of expression and regulation of blood group-related antigens in different cell types of human pancreas. Such complexity may largely be ascribed to differences in individual genotypes and in gene expression patterns of different cell types.     

Ley/H: an endothelial-selective, cytokine-inducible, angiogenic mediator

Endothelial cells (ECs) are key participants in angiogenic processes that characterize tumor growth, wound repair, and inflammatory diseases, such as human rheumatoid arthritis (RA). We and others have shown that EC molecules, such as soluble E-selectin, mediate angiogenesis. Here we describe an EC molecule, Lewisy-6/H-5-2 glycoconjugate (Ley/H), that shares some structural features with the soluble E-selectin ligand, sialyl Lewisx (sialyl Lex). One of the main previously recognized functions of Lewisy is as a blood group glycoconjugate. Here we show that Ley/H is rapidly cytokine inducible, up-regulated in RA synovial tissue, where it is cell-bound, and up-regulated in the soluble form in angiogenic RA compared with nonangiogenic osteoarthritic joint fluid. Soluble Ley/H also has a novel function, for it is a potent angiogenic mediator in both in vitro and in vivo bioassays. These results suggest a novel paradigm of soluble blood group Ags as mediators of angiogenic responses and suggest new targets for therapy of diseases, such as RA, that are characterized by persistent neovascularization.     

Lewis antigens in Helicobacter pylori: biosynthesis and phase variation

The lipopolysaccharides (LPS) of most Helicobacter pylori strains contain complex carbohydrates known as Lewis antigens that are structurally related to the human blood group antigens. Investigations on the genetic determinants involved in the biosynthesis of Lewis antigens have led to the identification of the fucosyltransferases of H. pylori, which have substrate specificities distinct from the mammalian fucosyltransferases. Compared with its human host, H. pylori utilizes a different pathway to synthesize the difucosylated Lewis antigens, Lewis y. and Lewis b. Unique features in the H. pylori fucosyltransferase genes, including homopolymeric tracts mediating slipped-strand mispairing and the elements regulating translational frameshifting, enable H. pylori to produce variable LPS epitopes on its surface. These new findings have provided us with a basis to further examine the roles of molecular mimicry and phase variation of H. pylori Lewis antigen expression in both persistent infection and pathogenesis of this important human gastric pathogen.     

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

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

Helicobacter pylori lipopolysaccharide in the IL-2 milieu activates lymphocytes from dyspeptic children

In this study, we assessed the proliferative response of peripheral blood mononuclear leukocytes (PBML) from 33 children/young adolescents with chronic dyspepsia, to H. pylori LPS in the presence and absence of IL-2 as a T cell growth factor. A rapid urease test (RUT) and a presence of Helicobacter-like organisms (HLO) in the biopsy specimens allowed us to distinguish RUT/HLO-positive (17/33) and -negative (16/33) patients. H. pylori LPS alone induced a proliferation of PBML from 4 out of 33 dyspeptic patients. IL-2 increased the prevalence of the response to LPS to 59% and 74% of RUT/HLO-positive and -negative patients, respectively. PBML from RUT/HLO-positive patients responded significantly less intensively to H. pylori LPS in the presence of IL-2, to IL-2 alone and to H. pylori LPS+IL-2. However, there was no difference in PHA-driven proliferation of PBML from the patients of those two groups. A negative correlation between the responsiveness to H. pylori LPS of PBML and occurrence of type B inflammation in gastric mucosa was demonstrated. The results suggest a contribution of H. pylori LPS to an outcome of H. pylori infection. It is speculated that H. pylori LPS by an activation of immunocompetent cells may reduce gastric inflammation, decrease bacterial load and prolong H. pylori infection.     

Helicobacter pylori lipopolysaccharide-mediated gastric and extragastric pathology.

Lipopolysaccharides (LPS) are a family of toxic phosphorylated glycolipids in the outer membrane of Gram-negative bacteria, including Helicobacter pylori, and are composed of a lipid moiety (termed lipid A), a core oligosaccharide, and a polymeric O-specific polysaccharide chain. Compared with LPS of other bacteria, H. pylori LPS and lipid A induce low immunological activities in a range of test systems. Nevertheless, these reduced levels of LPS-induced cytokines and toxic oxygen radicals can contribute, with those induced by bacterial proteins, to the H. pylori-associated inflammatory response. Whether the ability of H. pylori LPS to induce low production of both procoagulant activity and plasminogen activator inhibitor type 2 by human mononuclear cells contributes to localized inflammatory responses alone and, in addition, play a role in extragastric pathology remains an open question. The core oligosaccharide of H. pylori LPS, in part with a 25 kDa protein adhesin, mediates the binding of the bacterium to the host glycoprotein laminin, and hence interferes with gastric cell receptor-laminin interaction in the basement membrane. Also affecting mucosal integrity, the core sugars of certain H. pylori strains, particularly those associated with gastric ulceration, have been implicated in pepsinogen induction, but this is a strain-dependent phenomenon. Of particular interest, the O-chains of a large proportion of H. pylori strains mimic Lewis (Le) antigens. Although investigations have focussed on the role of these antigens in H. pylori-associated autoimmunity, which remains to be unequivocally established, other pathogenic consequences of Lewis mimicry are becoming apparent. Expression of Lewis antigens may be crucial for H. pylori colonization and adherence and, by aiding bacterial interaction with the gastric mucosa, thereby aid delivery of secreted products, and hence influence the inflammatory response.     

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

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

A novel Helicobacter pylori cell-surface polysaccharide

Helicobacter pylori bacteria colonize the gastric mucosa of more than half of the world's human population and its infection may instigate a wide spectrum of gastric diseases in the host. At the moment, there is no vaccine against H. pylori, a microorganism recognized as a category 1 human carcinogen, and treatment is limited to antibiotic management. Pioneering antigenic studies carried out by Penner and co-workers, which employed homologous H. pylori antisera specific for cell-surface lipopolysaccharide (LPS), revealed the presence of six distinct H. pylori serotypes (O1 to O6). Subsequent studies have shown that H. pylori serotype O1 expressed LPS with lengthy O-chain polysaccharide (PS) composed of Lewis blood-group structures ('Lewis O-chains'), serotype O3 LPS produced 'Lewis O-chains' attached to a heptoglycan domain, serotype O4 LPS possessed LPS with glucosylated 'Lewis O-chains' and serotype O6 LPS expressed the heptoglycan domain capped by a short 'Lewis O-chain'. These LPSs were terminated at the reducing-end by a core oligosaccharide and lipid A of conserved structures. With the intent of formulating a multivalent H. pylori LPS-based vaccine, we are studying the structural variability of H. pylori cell-surface glycans. Here, we describe the novel LPS structure produced by H. pylori serotype O2 that differed markedly from the typical H. pylori 'Lewis O-chain' structures, in that its main component was an elongated PS composed of alternating 2-, and 3-monosubstituted alpha-D-Glcp residues [-->2)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->]n. These findings revealed the bio-molecular basis for the observed serospecificity of H. pylori serotype O2, and that this unique bacterial PS must be included in the formulation of a multivalent LPS H. pylori vaccine.     

Interleukin-6 induction by Helicobacter pylori in human macrophages is dependent on phagocytosis

BACKGROUND: The colonization of the gastric mucosa with Helicobacter pylori is accompanied by elevated levels of proinflammatory cytokines, such as interleukin-1 (IL-1), IL-6, and IL-8. The aim of our study was to determine the mechanisms of IL-6 stimulation in phagocytes upon H. pylori infection. MATERIALS AND METHODS: We investigated the secretion of IL-6 by different professional phagocytes from murine and human origin, including granulocyte- and monocyte-like cells and macrophages derived from human peripheral blood monocytes (PBMCs). The influence of viability, phagocytosis, and the impact of different subcellular fractions of H. pylori bacteria were evaluated. RESULTS: IL-6 levels induced by H. pylori were low in cell lines derived from murine and human monocytes and in human granulocyte-like cells. By contrast, macrophages derived from human PBMCs were highly responsive to both H. pylori and Escherichia coli. IL-6 induction was blocked by inhibition of actin-dependent processes prior to infection with H. pylori, but not with E. coli or E. coli lipopolysaccharide (LPS). Using cell fractionation, the most activity was found in the H. pylori membrane. H. pylori LPS exhibited a 10(3)- to 10(4)-fold lower biologic activity than E. coli LPS, suggesting a minor role for toll-like receptor 4 (TLR4)-mediated signalling from the exterior. CONCLUSIONS: From these data, we conclude that macrophages may be a major source of IL-6 in the gastric mucosa upon H. pylori infection. The IL-6 induction by H. pylori in these cells is a multifactorial process, which requires the uptake and presumably degradation of H. pylori bacteria.     

Expression of histo-blood group antigens by lipopolysaccharides of Helicobacter pylori strains from asian hosts: the propensity to express type 1 blood-group antigens

Past studies have shown that the cell surface lipopolysaccharides (LPSs) of the ubiquitous human gastric pathogen Helicobacter pylori (a type 1 carcinogen) isolated from people residing in Europe and North America express predominantly type 2 Lewis x (Le(x)) and Le(y) epitopes and, infrequently, type 1 Le(a), Le(b), and Le(d) antigens. This production of Lewis blood-group structures by H. pylori LPSs, similar to those found in the surfaces of human gastric cells, allows the bacterium to mimic its human niche. In this study, LPSs of H.pylori strains extracted from patients living in China, Japan, and Singapore were chemically and serologically analyzed. When compared with Western H.pylori LPSs, these Asian strains showed a stronger tendency to produce type 1 blood groups. Of particular interest, and novel observations in H.pylori, the O-chain regions of strains F-58C and R-58A carried type 1 Le(a) without the presence of type 2 Le(x), strains R-7A and H607 were shown to have the capability of producing the type 1 blood group A antigen, and strains CA2, H507, and H428 expressed simultaneously the difucosyl isomeric antigens, type 1 Le(b) and type 2 Le(y). The apparent proclivity for the production of type 1 histo-blood group antigens in Asian H.pylori LPSs, as compared with Western strains, may be an adaptive evolutionary effect in that differences in the gastric cell surfaces of the respective hosts might be significantly dissimilar to select for the formation of different LPS structures on the resident H.pylori strain.     

Cell surface characteristics of Helicobacter pylori

Abstract 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.     

Lipopolysaccharides from Helicobacter pylori can act as antagonists for Toll-like receptor 4

Infection with Helicobacter pylori, a Gram-negative bacterium, is strongly associated with gastric ulcers and adenocarcinoma. The mechanisms by which the innate immune system recognizes H. pylori lipopolysaccharide (LPS) remain unclear. Contradictory reports exist that suggest that Toll-like receptors are involved. In this study we evaluated the interactions of Toll-like receptors with LPS from different strains of H. pylori. Using reporter cell lines, as well as HEK293 cells transfected with either CD14 and TLR4, or CD14 and TLR2, we show that H. pylori LPS-induced cell activation is mediated through TLR2. In addition, for the first time, we report that LPS from some H. pylori strains are able to antagonize TLR4. The antagonistic activity of H. pylori LPS from certain strains, as well as the activation via TLR2, might give H. pylori an advantage over the host that may be associated with the clinical outcome of H. pylori infection.     

The dendritic cell-specific C-type lectin DC-SIGN is a receptor for Schistosoma mansoni egg antigens and recognizes the glycan antigen Lewis x

Schistosoma mansoni soluble egg antigens (SEAs) are crucially involved in modulating the host immune response to infection by S. mansoni. We report that human dendritic cells bind SEAs through the C-type lectin dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN). Monoclonal antibodies against the carbohydrate antigens Lewisx (Lex) and GalNAcbeta1-4(Fucalpha1-3)GlcNAc (LDNF) inhibit binding of DC-SIGN to SEAs, suggesting that these glycan antigens may be critically involved in binding. In a solid-phase adhesion assay, DC-SIGN-Fc binds polyvalent neoglycoconjugates that contain the Lex antigen, whereas no binding was observed to Galbeta1-4GlcNAc, and binding to neoglycoconjugates containing only alpha-fucose or oligosaccharides with a terminal alpha1-2-linked fucose is low. These data indicate that binding of DC-SIGN to Lex antigen is fucose-dependent and that adjacent monosaccharides and/or the anomeric linkage of the fucose are important for binding activity. Previous studies have shown that DC-SIGN binds HIV gp120 that contains high-mannose-type N-glycans. Site-directed mutagenesis within the carbohydrate recognition domain (CRD) of DC-SIGN demonstrates that amino acids E324 and E347 are involved in binding to HIV gp120, Lex, and SEAs. By contrast, mutation of amino acid Val351 abrogates binding to SEAs and Lex but not HIV gp120. These data suggest that DC-SIGN recognizes these ligands through different (but overlapping) regions within its CRD. Our data imply that DC-SIGN not only is a pathogen receptor for HIV gp120 but may also function in pathogen recognition by interaction with the carbohydrate antigens Lex and possibly LDNF, which are found on important human pathogens, such as schistosomes and the bacterium Helicobacter pylori.     

A GDP-fucose:[Gal beta 1----4]GlcNAc alpha 1----3-fucosyltransferase activity is correlated with the presence of human chromosome 11 and the expression of the Lex, Ley, and sialyl-Lex antigens in human-mouse cell hybrids

By fusion of human leukocytes and cells of the murine myeloid cell line WEHI-TG, we produced human-mouse myeloid cell hybrids. Hybrids which contain human chromosome 11 have been demonstrated to express the myeloid-associated carbohydrate antigen Lex (Geurts van Kessel, A. H. M., Tetteroo, P. A. T., Von dem Borne, A. E. G. Kr., Hagemeijer, A., and Bootsma, D. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 3748-3752). In this paper, we report that the hybrids that contain chromosome 11 also expressed the Lex-related antigens Ley and sialyl-Lex. Glycosyltransferase activities were measured in a panel of six such hybrid cell lines, and the correlation to antigen expression and to the presence of human chromosomes was investigated. GDP-fucose:[Gal beta 1----4]GlcNAc alpha 1----3-fucosyltransferase activity in the hybrids tested correlated with the expression of Lex, Ley, and sialyl-Lex and with the occurrence of chromosome 11. No such correlation was found for several other glycosyltransferases involved in the synthesis of these antigens. These findings suggest that the gene for alpha 3-fucosyltransferase is located on chromosome 11 and that it is through the activity of this enzyme that the expression of Lex, Ley, and sialyl-Lex in human myeloid cells is regulated.     

Relevance of fucosylation and Lewis antigen expression in the bacterial gastroduodenal pathogen Helicobacter pylori

Helicobacter pylori is a prevalent bacterial, gastroduodenal pathogen of humans that can express Lewis (Le) and related antigens in the O-chains of its surface lipopolysaccharide. The O-chains of H. pylori are commonly composed of internal Le(x) units with terminal Le(x) or Le(y) units or, in some strains, with additional units of Le(a), Le(b), Le(c), sialyl-Le(x) and H-1 antigens, as well as blood groups A and B, thereby producing a mosaicism of antigenic units expressed. The genetic determination of the Le antigen biosynthetic pathways in H. pylori has been studied, and despite striking functional similarity, low sequence homology occurs between the bacterial and mammalian alpha(1,3/4)- and alpha(1,2)-fucosyltransferases. Factors affecting Le antigen expression in H. pylori, that can influence the biological impact of this molecular mimicry, include regulation of fucosyltransferase genes through slipped-strand mispairing, the activity and expression levels of the functional enzymes, the preferences of the expressed enzyme for distinctive acceptor molecules and the availability of activated sugar intermediates. Le mimicry was initially implicated in immune evasion and gastric adaptation by the bacterium, but more recent studies show a role in gastric colonization and bacterial adhesion with galectin-3 identified as the gastric receptor for polymeric Le(x) on the bacterium. From the host defence aspect, innate immune recognition of H. pylori by surfactant protein D is influenced by the extent of LPS fucosylation. Furthermore, Le antigen expression affects both the inflammatory response and T-cell polarization that develops after infection. Although controversial, evidence suggests that long-term H. pylori infection can induce autoreactive anti-Le antibodies cross-reacting with the gastric mucosa, in part leading to the development of gastric atrophy. Thus, Le antigen expression and fucosylation in H. pylori have multiple biological effects on pathogenesis and disease outcome.