Institute of Medical Biochemistry, Göteborg University, P.O. Box 440, S-405 30 Göteborg, Sweden
; Accepted on April 14, 2000.
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: Helicobacter pylori/microbial adhesion/lipopolysaccharide/adhesin/disease
![]() |
Recent discovery with important implications |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Global occurrence and life-long persistence
More than half of the global human population is colonized in the stomach by H.pylori, the human-specific spiral-shaped Gram-negative bacterium that escaped detection so long. In developing countries, 7090% of the population carry the bacterium, which is acquired before the age of 10 and persists through life (Dunn et al., 1997). In developed countries the prevalence of colonization ranges from 2550%. However, microbiological and epidemiological evidence indicates that H.pylori perhaps once was universal, but has gradually disappeared as industrialization has proceeded. In fact, in developed countries, less than 10% of the children are becoming infected today (Dunn et al., 1997
). There is an interesting global distribution of bacterium and human with an overlap of geographically isolated human and H.pylori populations (Covacci et al., 1999
). This supports the hypothesis that H.pylori was established in human stomach before the migrations of anatomically modern humans and followed humans thereafter. The mode of transmission is not clear, but the organism is probably transmitted directly from person to person and the family is therefore the core reservoir. Children chronically maintain the same strain, and subsequent colonization with other strains is rare.
Colonization is mostly nonsymptomatic but may induce serious disease
All colonized individuals develop chronic gastric inflammation, but this condition is usually asymptomatic (Dunn et al., 1997). Apparently, a sophisticated adaptation of the persistent microbehost interaction exists (Blaser and Kirschner, 1999
), where the major nutrient source for the bacterium may result from the inflammation, which is kept by the host at a limiting level to reduce bacterial growth and avoid disease. In 1020% of infected individuals the end result of colonization can be life-threatening. However, the factors behind this are still unclear, and the relation between bacterial and host parameters and clinical outcome is probably the most dynamic area in current H.pylori studies. In any population, H.pylori causes the majority of both gastric and duodenal ulcers. Carriage is also strongly associated with the risk to develop atrophic gastritis, which is a precursor lesion to gastric cancer, the second leading cause of cancer death in the world. In 1994 the WHO International Agency for Cancer Research declared H.pylori a human carcinogen of the highest class. Also, gastric mucosa-associated lymphoid tissue lymphoma, MALT lymphoma, is strongly associated with carriage of H.pylori. There are current investigations on the relation of other potential nongastric conditions and colonization with H.pylori, including atherosclerosis, allergic and autoimmune diseases, anemia and growth retardation (Covacci et al., 1999
; Gasbarrini and Franceschi, 1999
).
As the bacterium has been reduced in developed countries, peptic ulcer disease and noncardia gastric cancers have been decreasing. However, diseases such as gastroesophageal reflux, Barret esophagus, and adenocarcinomas of the lower esophagus and gastric cardia have been progressively increasing, raising the question if this is related to the reduction of H.pylori infections (Blaser, 1999a,b). Therefore, H.pylori colonization may have positive effects, and the microbe may be considered more as a normal gastric probiotic as long as disease does not develop. This has a parallel to other microbes, which may be "amphibiotic" organisms that may be either beneficial or disease-causing, depending on the conditions (Blaser, 1997
). A sophisticated supplementation after eradication (see Current therapy is not suitable for a large-scale prevention) may be a re-colonization with selected H.pylori strains to patients to reduce this risk (Blaser, 1999a
). Interestingly, a growing number of novel variants of Helicobacter are being described in human and animal gastrointestinal tracts (Wadström and Hänninen, 1999
; Westblom et al., 1999
). One may note the exciting recent discovery that H.pylori produces antibacterial peptides to which H.pylori is resistant (Putsep et al., 1999a
,b).
Genome sequences with essential information
Complete genome sequences have been determined for two unrelated H.pylori strains (Tomb et al., 1997; Alm et al., 1999
), and interesting functional consequences have recently been discussed in detail on a comparative basis (Alm and Trust, 1999
; Doig et al., 1999
; Ge and Taylor, 1999
; Marais et al., 1999
). The genome size is about one third that of E.coli and similar to H.influenzae, probably reflecting an adaptation to a restricted ecological niche. The two sequenced strains show relatively conserved genomic organizations; 1406 open readings frames are in common, and only 89 and 117, respectively, are strain-specific. A comparison with complete genome sequences of E.coli and H.influenzae indicated that as much as 63% of the H.pylori-specific gene products are potentially involved in H.pylorihost interaction. One provoking feature is that about 1% of the genome encodes a unique family of 32 outer membrane proteins, OMPs, to which three identified adhesins belong (see The glycobiology of bacterial-host interplay is sophisticated and complex). The significantly higher percentage of its coding capacity for OMPs compared to other bacteria may correspond to the unique complexity of carbohydrate-binding specificities that has been detected for H.pylori (see Sialic acid binding specificity and Other binding specificities). Other virulence factors of interest for colonization and survival in the human stomach are urease for buffering the gastric acid, flagella to swim through the mucus, vacuolating cytotoxin (VacA), neutrophil-activating protein (Hp-NAP, see Bacterial contact with neutrophils is not suicidal), and cag-PAI pathogenicity island encoding for the immunodominant CagA protein and for several other important proteins. VacA is a secreted protein that is responsible for the vacuolar degeneration of epithelial cells seen in colonized hosts. The protein is able to form hexameric anion-selective channels in planar lipid bilayers, following a disassembly of water-soluble dodecameric VacA at low pH, and this has been suggested to produce the osmotic imbalance necessary for the target cell vacuolation (Reyrat et al., 1999
). VacA specifically interacts with a novel filament-associated protein (de Bernard et al., 2000
).
![]() |
The glycobiology of bacterialhost interplay is sophisticated and complex |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Bacterial surface and molecular mimicry of host glycosylation
One distinct feature of several Gram-negative mucosal pathogens is that oligosaccharides of their LPS are identical or show strong structural similarity to human glyco-epitopes, including glycolipid-specific sequences (Preston et al., 1996). This molecular mimicry may have relevance for pathogenicity in several ways. Interestingly, different microbes may develop a separate mimicry apparently depending on the locale of colonization. As a constructive example of this, H.pylori will be compared with Haemophilus influenzae. H.influenzae was the first organism for which a complete genome sequence was obtained (Fleishmann et al., 1995
) and since then advanced information has been gained about host mimicry, LPS diversity and phase variation (see Hood et al., 1999
; Risberg et al., 1999
). This important Gram-negative bacterium exclusively colonizes the human nasopharynx, where it is able to persist for extended periods without causing disease. It is potentially pathogenic, however, and may cause respiratory tract infections and invade to cause systemic disease, such as meningitis. LPS has been shown to carry lactose, globotriaose or pk antigen, globotetraose or P antigen, and sialyllactose (sequences discussed in the present paper are listed in Table I). Interestingly, these epitopes on human cells are membrane-bound and glycolipid-specific and do not appear on glycoproteins or in secretions (see Karlsson, 1998
). A high-frequency phase variation found for the expression of saccharide epitopes is thought to provide an adaptive mechanism for survival in different microenvironments. For example, phosphorylcholine is linked to a hexose on the outer core region and located on the cell surface and it mimics host membrane phospholipid. Bacteria containing this modification appear to favor colonization of respiratory epithelia in a rat model, whereas its absence, probably after invasion, may confer resistance to host factors such as C-reactive protein for serum clearance (Weiser et al., 1998
). Although there is growing information on various glycoforms and genetic loci involved in phase variations (Hood et al., 1999
; Risberg et al., 1999
), and basic mechanisms of molecular switches are known (Henderson et al., 1999
), the potential local signals for this variation have not yet been identified. The precise meaning of mimicking host blood group P antigens for the nasopharynx colonization by this pathogen remains to be understood.
|
There are probably several more subtle differences in H.pylori LPS to be found. In a recent structural study (Aspinall et al., 1999), two strains were compared, of which one did and the other did not stimulate pepsinogen. LPS has been implicated in this activity, which is elevated in about half of the patients with doudenal ulcers, and H.pylori colonizes 90% of patients with this disease. The inactive strain was found to carry Gal
6GlcNAc residues on the LacNAc-glycan, which the active strain did not, and it was proposed that this substituent could cause a distortion of conformation to make this LPS inactive. This study further strengthens the importance of detailed structural studies to find out the roles of LPS in H.pylori pathogenesis.
A rapid phase variation of the expression of Lewis antigens in H.pylori has been documented in colonies derived from biopsies of single patients (Wirth et al., 1997), and one bacterial cell population showed a frequency of such a phase variation in the range of 0.20.5% (Appelmelk et al., 1998
). There is apparently a variation in Lewis antigen expression during the course of colonization in single individuals, as documented from gastric biopsies (Rasko et al., 2000b
). The role of the fucosyltransferase level on the mechanism of this phase variation is growing (Appelmelk et al., 1999
; Wang et al., 1999a
,b). Regulation apparently occurs at multiple levels, including replication, transcription, and translation. The potential signals for this are not known. It has been proposed that the phenotypic diversity in Lewis expression may provide a pool in human subjects for continuous selection of host-adapted populations suitable for persistence (Wirth et al., 1999
; Heneghan et al., 2000
). Dependence of both host and bacterial strain has been shown for colonization and inflammation in model animals, including nonhuman primates (Dubois et al., 1999
) and mice (van Doorn et al., 1999
). Of interest in this respect is the finding in ferrets, which are naturally colonized in the stomach by Helicobacter mustelae, of a parallel expression of blood group A type 1 antigen on the bacteria and on gastric cells (Monteiro et al., 1997
; Croinin et al., 1998
).
Potential autoimmunity mediated by Lewis antigens has not been possible to document as a basis for disease (Faller et al., 1998; Kamiya et al., 1999
). This may mean that the mimicry of host glycosylation is optimally balanced to normally avoid pathological immune response. What does it mean that H.pylori and H.influenzae, which both may colonize persistently in their respective niches, develop distinctly different LPS structures? Maybe this is a sophisticated reflection of host mucosa structure and ecology. On the host side, there may also develop a potential adaptation to the almost inherited bacterial colonization. According to a recent exciting hypothesis glycan diversification in complex multicellular organisms is driven by evolutionary selection pressures mainly from exogenous microbes that recognize glycans (Gagneux and Varki, 1999
). Whether H.pylori has exerted any selective pressure through the years on stomach glycosylation is practically impossible to investigate. During the long coevolution of H.pylori and humans (Blaser, 1999b
; Covacci et al., 1999
) it is not unlikely that signals in both directions have contributed to a "normal" optimized glycosylation of both microbe and stomach. Such glycosylation of stomach microniches may then be essential for the balanced non-disease state, and any change in glycosylation may disturb this balance to induce disease (see Modulation of host glycosylation).
Bacterial contact with neutrophils is not suicidal
H.pylori-induced gastritis is typically associated with a strong infiltration of the colonized stomach mucosa by neutrophils and mononuclear inflammatory cells, and there is a correlation between mucosal damage and neutrophil infiltration (Marshall and Warren and Marshall, 1983; Westblom et al., 1999
). However, LPS from H.pylori is known to have 1000-fold less ability to stimulate IL-8 production than LPS from E.coli (Kirkland et al., 1997
). In epithelial cell culture, adherent H.pylori are apparently able to stimulate IL-8 production through the ceramide-mediated pathway (Masamune et al., 1999
). A detailed mapping is being done of proinflammatory factors, including activator proteins and stress-response kinases, that potentially mediate epithelial cell degeneration following contact with H.pylori containing the cag pathogenicity island (Naumann et al., 1999
). The bacterial protein CagA may be translocated into gastric epithelial cells and phosphorylated on tyrosine (Segal et al., 1999
; Odenbreit et al., 2000
; Stein et al., 2000
). However, proinflammatory activation of neutrophils is not associated with cagA genotypes (Hansen et al., 1999
). Water-soluble bacterial surface proteins activate neutrophils and upregulate expression of chemokines (Kim et al., 2000
). A protein capable of promoting neutrophil adhesion to endothelial cells was identified in H.pylori extracts and shown to mediate induction of neutrophil CD11b/CD18 adhesion molecules, which interact with ICAM-1 (Yoshida et al., 1993
). This neutrophil-activating protein, Hp-NAP, has recently been characterized in detail including molecular modeling (Tonello et al., 1999
). The 17 kDa subunit forms a dodecameric structure with a hollow central core and may bind up to 500 iron atoms per oligomer; it is resistant to thermal and chemical denaturation, which is similar to the case for the related ferritin family of proteins.
Hp-NAP is a carbohydrate-binding protein (Teneberg et al., 1997; Namavar et al., 1998
). A recombinant Hp-NAP was shown to bind to distinct gangliosides of human neutrophils having as a common feature repeated non-substituted LacNAc (Teneberg et al., 1997
). There was also binding to sulfatide, but this glycolipid was absent from neutrophils. An extracted bacterial surface-located protein, identified as Hp-NAP, was claimed to bind sulfated oligosaccharide structures of human high-molecular-weight salivary mucin, such as sulfated Lewis a, SO3-3Gal, and SO3-6GlcNAc (Namavar et al., 1998
). In a recent study various glycoconjugates were isolated from neutrophils and tested for bacterial cell binding by overlay assays (Miller-Podraza et al., 1999
). An apparently high-affinity sialic aciddependent binding was detected for gangliosides, polyglycosylceramides and glycoproteins, and this was the only binding specificity found. It has been shown that H.pylori cells, upon direct contact with neutrophils, induce a rapid oxidative burst followed by a slower phagocytosis (Mooney et al., 1991
; Rautelin et al., 1993
). However, the bacteria are not necessarily killed, in contrast to other microbes. Instead, as discussed above, H.pylori may satisfy part of its nutritional requirements from degradation products of the inflammatory reaction (Blaser, 1996
, 1997; Blaser and Kirschner, 1999
). Therefore, H.pylori not only resists inflammation, but actively recruits neutrophils to induce the inflammation, which may be beneficial for the microbe. It remains to be shown if the sialic aciddependent H.pylorineutrophil interactions mediate the biological responses.
Direct microbehost attachment mediated by carbohydrate
In addition to the sialic aciddependent recognition of neutrophil glycoconjugates, there are several binding specificities detected for bacterial cells. The majority of H.pylori cells reside in the stomach mucus where they divide, and only a small fraction is found adhered to gastric epithelial cells. The tropism in human gastric epithelium is distinct. By use of an in situ adherence assay and H.pylori strains labeled with fluorescein isothiocyanate (FITC), four out of five strains, including gastric-ulcer and acute-gastritis isolates, attached exclusively to surface mucous cells present in the pit region of gastric units, but not to mucous neck, parietal, or chief cell lineages present in the glandular domains of the units (Falk et al., 1993). Naturally, H.pylori colonizes only primates. Only in one case has a carbohydrate-binding protein been convincingly identified on H.pylori cells, the Lewis b adhesin (Ilver et al., 1998
) (see also Hp-NAP discussed in Bacterial contact with neutrophils is not suicidal).
Adhesin-mediated adherence
Only three adhesins of H.pylori have been convincingly identified, AlpA and AlpB adhesins necessary for adherence to gastric tissue (Odenbreit et al., 1999) and the BabA adhesin (Ilver et al., 1998
). No host receptors are yet known for the AlpA and AlpB adhesins, but the BabA adhesin recognizes the Lewis b blood group antigen (Borén et al., 1993
). BabA is encoded by babA2 in strain CCGU 17875 and is composed of 721 aa residues. A second gene, babA1, is identical to babA2 except for lack of an insertion of 10 bp present in babA2. The truncated BabA product of babA1 was unable to bind Lewis b. AlpA, AlpB and BabA all belong to the family of 32 OMPs (Tomb et al., 1997
). Six out of six wild-type strains expressed AlpA and AlpB but only 34% of tested strains expressed Lewis b binding. Members of the remaining OMPs may prove to be adhesins recognizing some of the other carbohydrate-binding specificities listed below. The OMPs share extensive sequence homology in the N- and C-terminal domains. The C-terminal portion of AlpA and AlpB was predicted to form a porin-like ß-barrel in the outer membrane of H.pylori, consisting of 14 transmembrane amphipathic ß-strands (Odenbreit et al., 1999
).
The fine specificity of BabA binding has been studied using various assays and substances (Borén et al., 1993; Borén et al., 1994
). Of a panel of fucosylated neoglycoproteins the Lewis b derivative gave 93% reduction of binding in the in situ biopsy assay, while the H type 1 derivative reduced binding to 52%. However, in the form of glycoproteins, Lewis a, Lewis x, Lewis y, and H type 2 determinants were inactive as receptors. Similar results were obtained in solid-phase binding on western blots. However, for free oligosaccharides in solution Lewis b, H type 1, and Lewis y inhibited binding equally well, indicating that Fuc
2Gal is the minimal requirement, rather than Lewis b, and that a Fuc branch on GlcNAc may stabilize the epitope presentation for better binding. These data were confirmed by inhibition with synthetic saccharides linked up to polymer (Eklind et al., 1996
). The babA2 gene is of clinical relevance, and its presence is significantly associated with duodenal ulcer and adenocarcinoma, and it may therefore be a useful marker to identify those individuals at higher risks for disease (Gerhard et al., 1999
).
Sialic acid binding specificity
The first binding specificity detected for H.pylori was sialic acid-dependent, as shown by hemagglutination studies (Evans et al., 1988). The gene encoding the adhesin protein on H.pylori was reportedly identified in 1993, and an antibody to the protein was raised that bound to bacterial cell bodies (Evans et al., 1993
). Later, however, the cytoplasmic localization and lipoprotein nature of this protein was shown, but knock-out of the gene did not change adhesion properties (O'Toole et al., 1995
). The lipoprotein character was confirmed by a separate investigation which repeated the cloning and expression, and a carefully defined antibody and immunogold labeling was used to localize the protein to the flagellar sheath, rather than intracellularly or to the cell body. Adhesion characteristics were unaffected by gene inactivation (Jones et al., 1997
). Therefore, an adhesin recognizing sialic acid still awaits identification.
The initial conclusion of a NeuAc3Gal-based specificity (Evans et al., 1988
) was later confirmed (Hirmo et al., 1996
; Johansson and Karlsson, 1998
). Apparently, there is a strict requirement for an intact NeuAc, since various chemical modifications eliminate binding (Miller-Podraza et al., 1998
). A type 2 core is essential (H.Miller-Podraza et al., unpublished observations). This binding is expressed only when bacterial cells are grown on agar and is lost after growth in broth. However, a second sialic aciddependent binding specificity remained after growth in broth and strict selectivity was proposed (Miller-Podraza et al., 1996
, 1997). Only polyglycosylceramides were positive, but traditional gangliosides or sialylated glycoproteins were inactive. These complex glycolipids with about 15 to 45 monosaccharides linked to ceramide are highly heterogeneous with incompletely branched, N-acetyllactosamine-based chains terminating with 12 NeuAc per molecule (Karlsson et al., 1999
). The binding is completely lost after mild periodate oxidation, but further details of the binding epitope are still lacking, except that NeuAc is probably 3-linked (Johansson et al., 1999
). These two specificities differ in detailed binding pattern from the binding of Hp-NAP to sialyl conjugates (see Bacterial contact with neutrophils is not suicidal). The extracellular matrix protein laminin has been shown to bind H.pylori in a sialic-dependent way, and a bacterial 25 kDa outer membrane protein was proposed to mediate this binding (Valkonen et al., 1997
).
Other binding specificities
On thin-layer plates, several glycolipids have been shown to bind H.pylori, including sulfatide, which is abundant in human gastric epithelium (Saitoh et al., 1991; Kamisago et al., 1996
), gangliotria- and gangliotetraosylceramide (Gold et al., 1993
), lactosylceramide (Ångström et al., 1998
), and some other glycolipids (S.Teneberg et al., unpublished observations). Heparan sulfate shows a strong binding by H.pylori (Ascencio et al., 1993
), and heparin-binding bacterial proteins have been detected (Utt and Wadström, 1997
). Evidence has been presented that blood group sequences H type 2, Lewis a and Lewis b mediate binding to cultured epithelial cells, based on blocking of binding by monoclonal antibodies, and by binding biotinylated blood group antigens (Alkout et al., 1997
). Affinity adsorption of bacterial extracts on blood group particles resulted in a major protein of 61 kDa. Binding to phosphatidylethanolamine has also been reported (Lingwood et al., 1992
). The relevance for colonization or pathogenicity has not been shown for any of these specificities.
LPShost cell and potential carbohydratecarbohydrate interactions
In view of the growing evidence for selective carbohydratecarbohydrate interactions of biological importance (for a recent review, see Spillman and Burger, 2000), it may be appropriate to include some comments concerning a potential relevance of this type of interaction for H.pylori in human stomach. There is one paper reporting H.pylori cell binding to laminin, apparently mediated by LPS (Valkonen et al., 1994
). Laminin is a basement membrane glycoprotein that may become exposed after disruption of the epithelial cell layer, potentially caused by damage or rapid cell turnover. The conclusion after using various parts of modified LPS as inhibitors was that a phosphorylated structure in the core oligosaccharide mediated interaction with a hemagglutinating strain, and a nonphosporylated structure mediated interaction with a poorly hemagglutinating strain. No further details are available, and the binding site on laminin, whether peptide or saccharide, remains to be identified. Thus, there are two separate interactions of H.pylori with laminin, one mediated by LPS and the other by a protein recognizing sialic acid (see The sialic acid binding specificity). Recently, convincing evidence was provided that LPS Lewis x is involved in targeting H.pylori to human gastric mucosal epithelial cells and cells lining gastric pits, probably a saccharideprotein interaction (Edwards et al., 2000
). Targeting with Lewis xconjugated beads was indistinguishable from that of bacterial cells. For other bacteria there is evidence for LPS involvement in adherence (Jacques, 1996
) and direct binding to glycolipids. Pseudomonas aeruginosa cells and extracted LPS bound gangliotetraosylceramide on thin-layer chromatograms, but not other glycolipids (Gupta et al., 1994
). For Actinobacillus pleuropneumoniae, which causes pleuropneumonia of pigs, evidence suggests that LPS has a role in adherence to pig tracheal tissue (Bélanger et al., 1990
). Recently this was studied in detail by use of defined glycolipids separated on thin-layer plates (Abul-Milh et al., 1999
). Extracted LPS and intact cells showed similar binding to glycolipids, and among many tested glycolipids, GlcßCer, GalßCer, sulfatide, lactosylceramide, gangliotriaosylceramide, and gangliotetraosylceramide were positive. Binding to the former four glycolipids, but not to the latter two, was inhibited by preincubation of bacteria with monoclonal antibodies to the O antigen part of LPS, indicating that different parts of LPS may be involved in interaction with glycolipids.
Therefore, H.pylori LPS should be carefully tested for a potential binding to sulfatide, lactosylceramide, gangliotriaosylceramide, and gangliotetraosylceramide. The latter two glycolipids have, however, not been detected in human stomach (S.Teneberg et al., unpublished observations). Also a potential Lewis xLewis x interaction should be tested (Spillman and Burger, 2000). In the case of H.influenzae (see Bacterial surface and mimicry of host glycosylation), both lactose and blood group P sequences should be tested for potential carbohydrate-carbohydrate binding (Spillman and Burger, 2000
).
![]() |
Dynamic microniche ecology with effects on interplay |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Variable expression of carbohydrate-binding specificities
Individual type-collection strains do not exhibit all specificities summarized above. Usually a majority are expressed, although with an apparent phase variation of expression during standard cultivation (see Karlsson, 1998). However, individual specificity, such as the sialic acid binding after cultivation on agar, has been shown to be more consistently expressed in fresh clinical isolates, in contrast to strains with large passage numbers (Simon et al., 1997
). Two different sialic aciddependent specificities were obtained from separate cultivation conditions. Of the two types of strains, CCUG 17874 and CCUG 17875, the first recognizes sialic acid but not Lewis b, and the second recognizes Lewis b but not sialic acid. However, a surprising result from CCUG 17875 was recently obtained indicating a sophisticated phase variation and interdependence in expression (T.Borén et al., unpublished observations). After inactivation of the babA genes the Lewis b binding was lost as expected (Ilver et al., 1998
). However, the lost Lewis b binding was apparently replaced by the two sialic acid-dependent binding mechanisms, with a binding pattern identical to that of strain CCUG 17874 when tested against various glycoconjugates. In the case of sulfatide binding, this was shown to depend on stress conditions to be expressed (Huesca et al., 1996
). An overlay assay on thin-layer plates showed that this binding appeared first after brief treatment of bacteria at low pH. The effect could be linked to surface-located heat shock proteins and was prevented by inhibitors of protein synthesis.
These scattered data may indicate a capacity of H.pylori for regulated phase variation in carbohydrate-binding specificities, possibly as a reaction to specific as yet unidentified signals in the different microniches that H.pylori cells are known to occupy.
Modulation of host glycosylation
For potential interaction sites, including mucus, gastric epithelial cells, neutrophils, and basement membrane, it is important to study not only the nonsymptomatic chronic gastritis state, but also conditions which may result from disturbances or disease. Concerning mucus, it is not known if there are mucus epitopes of importance being recognized by H.pylori in normal or diseased stomach. The glycosylation pattern of human gastric mucins varies in different gastric compartments and are reversibly changed by H.pylori colonization (Ota et al., 1998). Regarding epithelial cells, the in situ adherence assay based on biopsy material from human stomach is highly informative (Falk et al., 1993
). The distinct binding to surface mucous cells of the pit region of gastric units was inhibited by Lewis b conjugates, but no evidence was obtained for interaction with sialyl conjugates. Instead sialic acidbinding plant lectins were shown to recognize sites in the submucosal compartment. Although the FITC labeling may modify the bacterial properties, and the extraction step of biopsy treatment may remove glycolipids (see discussion by Simon et al., 1997
), the results show that Fuc-epitopes mediate H.pylori attachment to normal mucosa and that sialic acid may not be essential. Our group has indirectly confirmed this by chemical analyses of mucosa scrapings, which practically lack a sialic acid-dependent binding to glycolipids or glycoproteins (S.Teneberg et al., unpublished observations). In contrast, neutrophils, which are numerous in inflamed mucosa, are rich in sialylated glycoconjugates (Miller-Podraza et al., 1999
), which might indicate that neutrophils are the major potential targets for the sialic aciddependent binding, at least in the nonsymptomatic situation.
Interestingly, the pathological state may show a pattern of glycosylation of potential importance for colonization of H.pylori and disease progression. A transgenic mouse model was developed where the Lewis fucosyltransferase was transfected. This resulted in expression of Lewis b in the surface mucous cells of the gastric pit, similar to the human situation (Falk et al., 1995). In vitro, clinical isolates bound to these cells of the transgenic mouse but not of their normal littermates. In a more recent study, the same group used a transgenic mouse model deficient in parietal cells (Syder et al., 1999
). This situation amplifies presumptive gastric epithelial stem cells and their immediate committed daughters, which were shown to express sialylated conjugates, including sialyl-Lewis x. These sites mediated attachment of H.pylori which resulted in enhanced cellular and humoral immune responses. The authors proposed that similar cellular modulations may be the basis of tumorigenesis in patients with chronic atrophic gastritis. A high salt diet in a mouse model induced gastric hyperplasia and parietal cell loss and enhanced H.pylori colonization (Fox et al., 1999
). In a separate study the H.pylori mutant with inactivated Lewis b binding and induced sialic acid binding (see Variable expression of carbohydrate-binding specificities) was used to detect sialyl-Lewis x binding in inflamed human and Rhesus monkey gastric mucosa (T.Borén et al., unpublished observations). In this way a Lewis bindependent and sialyl/Lewis xdependent binding was found in the gastric pit region, the same location as found in the original study using the wild-type strain expressing Lewis b binding (Falk et al., 1993
). There was a positive correlation between adherence and the level of an inflammatory response, and in the monkey a challenge with H.pylori established a chronic inflammation that promoted sialylLewis x binding. However, such a relation was not found for the Lewis b binding. Of 91 tested clinical isolates of H.pylori, 40 were positive binders of sialylLewis x. Interestingly, also the transgenic mouse expressing Lewis b in the gastric pit cells, but not the normal mouse, expressed sialyl-Lewis x binding, indicating that the increased fucosylation from transfection also affected sialyl conjugates. These two studies therefore document a modulation of host glycosylation after genetic manipulation and bacterial colonization, respectively, with distinct consequences for bacterial interaction. Of interest is that dimeric sialylLewis x expression in human gastric carcinoma correlates with a poor outcome (Amado et al., 1998
), and it is known that human gastric tumors show aberrant glycosylation and may be highly sialylated (Hakomori, 1996
).
Therefore, when the persistent and nonsymptomatic H.pylori colonization may come out of balance for still unknown reasons, distinct changes in host glycosylation may appear, which may affect adhesin expression to strengthen an association or switch target cell. One may note that intimate adhesion has clear effects on the outcome. For the transgenic mouse model expressing Lewis b in gastric pit cells, it was shown that a persistent colonization with H.pylori did not differ in bacterial density from the normal mouse (Guruge et al., 1998). However, only the transgenic mouse produced autoantibodies to Lewis x antigens, chronic gastritis, and parietal cell loss, probably a result of close attachment to epithelial cells.
![]() |
Current therapy is not suitable for a large-scale prevention |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Naturally acquired human immune responses against H.pylori are currently being mapped as a basis for developing therapeutic and prophylactic vaccines (Zevering et al., 1999). Current vaccination approaches (Blanchard et al., 1999
) use various models including transgenic and knock-out animals (Nedrud, 1999
). A recent study on infected humans (Michetti et al., 1999
) used H.pylori urease mixed with E.coli heat-labile enterotoxin for immunization. This composition was well tolerated and immunogenic and a decrease in the density of bacteria was observed. In a commentary (Czinn and Nedrud, 1999
), however, the evaluation was that a useful vaccine is probably far away due to still very weak effects. An expression library of H.pylori genes was screened with sera from infected humans and from immunized rabbits and a number of immunogenic proteins were detected (Lazowska et al., 2000
).
Low-abundance adhesins and knowledge of adhesinhost interactions may be used both for vaccination against the adhesin and for design of receptor saccharide analogues based on structural chemistry. Vaccination with mannose-binding FimH adhesin of uropathogenic E.coli protects against bladder infection in mice (Langermann et al., 1997) and cynomolgus monkeys (Langermann et al., 2000
). Blocking of influenza virus neuraminidase with sialic acid analogues is currently subject to clinical trials (Wade, 1997
; Laver et al., 1999
), and new promising approaches of receptor analogue design are being optimized (Davis and Wareham, 1999
; Sears and Wong, 1999
). Natural glycoconjugates are of interest especially if resorption is not necessary (Zopf and Roth, 1996
; McAuliffe and Hindsgaul, 1997
). Sialyllactose efficiently inhibited H.pylori adhesion to human gastrointestinal epithelial cell lines (Simon et al., 1997
). Sialyllactose coupled up multivalently to albumin was about 1000 times more effective than free saccharide. An addendum in proof of this paper noted that free saccharide administered orally for 28 days to infected humans caused a significant reduction of H.pylori as assayed by the urea breath test. In a separate study on 12 Rhesus monkeys the same trisaccharide was used either alone or in combination with established chemotherapy (Mysore et al., 1999
). The conclusion was that antiadhesive treatment is safe and may cure or decrease colonization, but that addition of a proton pump inhibitor or bismuth subsalicylate did not improve cure rate. Although the H.pylori case reveals a diversity of interactions, and there is dynamics in host glycosylation, an optimally designed multivalent glycoconjugate based on only one expressed binding specificity may agglutinate the bacterial cells and therefore prevent them from host cell interaction. Thus, it may not be necessary to use a more expensive broad spectrum of saccharide analogues to inhibit colonization.
![]() |
Outlook |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Most provocative is the family of 32 OMPs that include the three identified adhesins. It is essential to identify the potential recognition by OMPs of host glycoconjugates. A new promising general method was recently developed for the functional expression of genes encoding adherence-associated OMPs (Fischer et al., 1999). This technique makes it possible to manipulate genes to define amino acid sequences critical for adhesinreceptor interaction. This requires improved assays to read-off the potential effects. New aspects of bacterial invasion of gastric epithelium as a way to establish persistent colonization have to be considered (Su et al., 1999
). Starting from the other side, the long list of carbohydrate-binding specificities that have been detected may be used to identify corresponding adhesins by new highly sensitive proteomics approaches. This was documented for BabA, which exists in only about 500 copies per bacterial cell (Larsson et al., 2000
). A receptor-active glycoconjugate probe is tagged with a photoreactive crosslinker to allow coupling to the adhesin, and with biotin for affinity isolation of the product. This tagging technique was earlier applied for the cloning of BabA (Ilver et al., 1998
). Such low-abundant and conserved proteins may prove to be suitable components of vaccine formulas (see example for E.coli above); a reason why they normally escape immune detection on the microbe may be their low surface density (Wizemann et al., 1999
). Purified adhesins will also be helpful as specific reagents in the mapping of potential binding sites in normal and pathological biopsy samples of host tissues. The unique list of carbohydrate-binding specificities has to be critically evaluated and supplemented with detailed analyses of target glycoconjugates. Determining binding sites in complex mucins may be simplified by coupling of released saccharides to generate neoglycolipids, which are easier to detect as molecular species and simpler to identify by chemical analysis than the intact glycoproteins (Chai et al., 1999
).
Recently, the first crystal structure was obtained for a bacterial adhesin, the mannose-binding FimH adhesin of uropathogenic E.coli (Choudhury et al., 1999), which has also been used for vaccination (see Current therapy is not suitable for a large-scale prevention). Such information is a prerequisite for structural drug design of saccharide analogues to potentially interfere with colonization. Therefore, it is important to express defined adhesins of H.pylori in sufficient amounts for crystallization. This may be assisted by computational genomics for the prediction of both structure and function of coded proteins, which recently was applied on H.pylori for the first time (Pawlowski et al., 1999
).
On the clinical side a major question remains as to why disease develops in a minority of individuals with persistent H.pylori colonization. To answer this will require additional epidemiological and other studies. Transgenic mouse infection models have already been helpful (Falk et al., 1995; Guruge et al., 1998
; Syder et al., 1999
). However, animal models will remain imperfect as long as they are not completely humanized, including glycosylation; therefore, they may provide information only on selected, though essential, aspects.
![]() |
Acknowledgments |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Alkout,A.M., Blackwell,C.C., Weir,D.M., Poxton,I.R., Elton,R.A., Luman,W. and Palmer,K. (1997) Isolation of a cell surface component of Helicobacter pylori that binds H type 2, Lewis a and Lewis b antigens. Gastroenterology, 112, 11791187.[ISI][Medline]
Alm,R.A. and Trust,T.J. (1999) Analysis of the genetic diversity of Helicobacter pylori: the tale of two genomes. J. Mol. Med., 77, 834846.[ISI][Medline]
Alm,R.A., Ling,L.S.-L., Moir,D.T., King,B.L., Brown,E.D., Doig,P.C., Smith,D.R., Noonan,B., Guild,B.C., deJonge,B.L., Carmel,G., Tummino,P.J., Caruso,A., Uria-Nickelsen,M., Mills,D.M., Ives,C., Gibson,R., Merberg,D., Mills,S.D., Jiang,Q., Taylor,D.E., Vovis,G.F. and Trust,T.J. (1999) Genomic-sequence comparison of two unrelated isolates of the human pathogen Helicobacter pylori., Nature, 397, 176180.[ISI][Medline]
Amado,M., Carniero,F., Seixas,M., Clausen,H. and Sobrinho-Simones,M. (1998) Dimeric sialyl/Le x expression in gastric carcinoma correlates with venous invasion and poor outcome. Gastroenterology, 114, 462470.[ISI][Medline]
Ångström,J., Teneberg,S., Abul Milh,M., Larsson,T., Leonardsson,I. Olsson,B.-M., Ölwegård Halvarsson,M., Danielsson,D., Näslund,I., Ljungh,Å. and others. (1998) The lactosylceramide binding specificity of Helicobacter pylori. Glycobiology, 8, 297309.
Appelmelk,B.J., Shiberu,B., Trinks,C., Tapsi,N., Zheng,P.Y., Verboom,T., Maaskant,J., Hokke,C.H., Schiphorst,W.E.C.M., Blanchard,D. and others. (1998) Phase variation in Helicobacter pylori lipopolysaccharide. Infect. Immun., 66, 7076.
Appelmelk,B.J., Martin,S.L., Monteiro,M.A., Clayton,C.A., McColm,A.A., Zheng,P., Verboom,T., Maaskant,J.J., van den Eijnden,D.H., Hokke,C.H. and others. (1999) Phase variation in Helicobacter pylori lipopolysaccharide due to changes in the lengths of poly (C) tracts in 3Fuc-transferase genes. Infect. Immun., 67, 53615366.
Ascencio,F., Fransson,L.-Å. and Wadström,T. (1993) Affinity of the gastric pathogen Helicobacter pylori for the N-sulphated glycosaminoglycan heparan sulphate. J. Med. Microbiol., 38, 240244.[Abstract]
Aspinall,G.O. and Monteiro,M.A. (1996) Lipopolysaccharides of Helicobacter pylori strains P466 and MO19: structures of the O antigen and core oligosaccharide regions. Biochemistry, 35, 24982504.[ISI][Medline]
Aspinall,G.O., Monteiro,M.A., Pang,H., Walsh,E.J. and Moran,A.P. (1996) Lipopolysaccharide of the Helicobacter pylori type strain NCTC 11637 (ATCC 43504): structure of the O antigen chain and core oligosaccharide regions. Biochemistry, 35, 24892497.[ISI][Medline]
Aspinall,G.O., Monteiro,M.A., Shaver,R.T., Kurjanczyk,L.A. and Penner,J.L. (1997) Lipopolysaccharides of Helicobacter pylori serogroups O:3 and O:6. Structures of a class of lipopolysaccharides with reference to the location of oligomeric units of D-glycero--D-manno-heptose residues. Eur. J. Biochem., 248, 592601.[Abstract]
Aspinall,G.O., Mainkar,A.S. and Moran,A.P. (1999) 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. Glycobiology, 9, 12351245.
Bélanger,M., Dubreuil,D., Harel,J., Girard,C. and Jacques,M. (1990) Role of lipopolysaccharides in adherence of Actinobacillus pleuropneumoniae to porcine tracheal rings. Infect. Immun., 58, 35233530.[ISI][Medline]
Blanchard,T.G., Czinn,S.J. and Nedrud,J.G. (1999) Host responses and vaccine development to Helicobacter pylori infection. In Westblom,T.U., Czinn,S.J. and Nedrud,J.G. (eds.), Gastroduodenal disease and Helicobacter pylori. Pathophysiology, diagnosis and treatment. Curr. Top. Microbiol. Immunol., 241, 181213. Springer-Verlag, Berlin.[ISI][Medline]
Blaser,M.J. (1996) The bacteria behind ulcers. Sci. Am., 274, 9297.[ISI][Medline]
Blaser,M.J. (1997) Ecology of Helicobacter pylori in the human stomach. J. Clin. Invest., 100, 759762.
Blaser,M.J. (1999a) In a world of black and white, Helicobacter pylori is grey. Ann. Intern. Med., 130, 695697.
Blaser,M.J. (1999b) Hypothesis: the changing relationships of Helicobacter pylori and humans: implications for health and disease. J. Infect. Dis., 179, 15231530.[ISI][Medline]
Blaser,M.J. and Kirschner,D. (1999) Dynamics of Helicobacter pylori colonization in relation to the host response. Proc. Natl. Acad. Sci. USA, 96, 83598364.
Borén,T., Falk,P., Roth,K.A., Larson,G. and Normark,S. (1993) Attachment of Helicobacter pylori to human gastric epithelium mediated by blood group antigens. Science, 262, 18921895.[ISI][Medline]
Borén,T., Normark,S. and Falk,P. (1994) Helicobacter pylori: molecular basis for host recognition and bacterial adherence. Trends Microbiol., 2, 221228.[Medline]
Chai,W., Yuen,C.T., Feizi,T. and Lawson,A.M. (1999) Core-branching pattern and sequence analysis of mannitol-terminating oligosaccharides by neoglycolipid technology. Anal. Biochem., 270, 314322.[ISI][Medline]
Choudhury,D., Thompson,A., Stojanoff,V., Langermann,S., Pinkner,J., Hultgren,S.J. and Knight,S.D. (1999) X-Ray structure of the FimC-FimH chaperone-adhesin complex from uropathogenic Escherichia coli. Science, 285, 10611066.
Covacci,A., Telford,J.L., Del Guidice,G., Parsonnet,J. and Rappuoli,R. (1999) Helicobacter pylori and genetic geography. Science, 284, 13281333.
Croinin,T.O., Clyne,M. and Drumm,B. (1998) Molecular mimicry of ferret gastric epithelial blood group A antigen by Helicobacter mustelae. Gastroenterology, 114, 690696.[ISI][Medline]
Czinn,S.J. and Nedrud,J.G. (1999) Working towards a Helicobacter pylori vaccine. Gastroenterology, 116, 990994.[ISI][Medline]
Davis,A.P. and Wareham,R.S. (1999) Carbohydrate recognition through noncovalent interactions: a challenge for biomimetic and supramolecular chemistry. Angew. Chem. Int. Ed., 38, 29782996.
de Bernard,M., Moschioni,M., Napolitani,G., Rappuoli,R. and Montecucco,C. (2000) The VacA toxin of Helicobacter pylori identifies a new intermediate filament-interacting protein. EMBO J., 19, 4856.
Doig,P., de Jonge,B.L., Alm,R.A., Brown,E.D., Uria-Nickelsen,M., Noonan,B., Mills,S.D., Tummino,P., Carmel,G., Guild,B.C. and others. (1999) Helicobacter pylori physiology predicted from genomic comparison of two strains. Microbiol. Rev., 63, 675707.
Doolitle,R.F. (1997) A bug with excess gastric avidity. Nature, 388, 515516.[ISI][Medline]
Dubois,A., Berg,D.E., Incecik,E.T., Fiala,N., Heman-Ackah,L.M., del Valle,J., Yang,M., Wirth,H.-P., Perez-Perez,G.I. and Blaser,M.J. (1999) Host specificity of Helicobacter pylori strains and host responses in experimentally challenged nonhuman primates. Gastroenterology, 116, 9096.[ISI][Medline]
Dunn,B.E., Cohen,H. and Blaser,M.J. (1997) Helicobacter pylori. Clin. Microbiol. Rev., 10, 720741.
Edwards,N.J., Monteiro,M.A., Faller,G., Walsh,E.J., Moran,A.P., Roberts,I.S. and High,N.J. (2000) Lewis x structures in the O antigen side-chain promote adhesion of Helicobacter pylori to the gastric epithelium. Mol. Microbiol., 35, 15301539.[ISI][Medline]
Eklind,K., Gustafsson,R., Tidén,A.-K., Norberg,T. and Åberg,P.-M. (1996) Large-scale synthesis of a Lewis b tetrasaccharide derivative, its acrylamide copolymer and related di- and trisaccharides for use in adhesion inhibition studies with Helicobacter pylori. J. Carb. Chem., 15, 11611178.[ISI]
Evans,D.G., Evans,D.J.,Jr., Molds,J.J. and Graham,D.Y. (1988) N-Acetylneuraminyllactose-binding fibrillar hemagglutinin of Campylobacter pylori: a putative colonization factor antigen. Infect. Immun., 56, 28962906.[ISI][Medline]
Evans,D.G., Karjalainen,T.K., Evans,D.J.,Jr Graham,D.Y. and Lee,C.H. (1993) Cloning, nucleotide sequence and expression of a gene encoding an adhesin subunit protein of Helicobacter pylori. J. Bacteriol., 175, 674683.[Abstract]
Falk,P., Roth,K.A., Borén,T., Westblom,T.U., Gordon,J.I. and Normark,S. (1993) An in vitro adherence assay reveals that Helicobacter pylori exhibits cell lineage-specific tropism in the human gastric epithelium. Proc. Natl. Acad. Sci. USA, 90, 20352039.[Abstract]
Falk,P.G., Bry,L., Holgersson,J. and Gordon,J. (1995) Expression of a human -1,3/4-fucosyltransferase in the pit cell lineage of FVB/N mouse stomach results in production of Le b-containing glycoconjugates: a potential transgenic mouse model for studying Helicobacter pylori infection. Proc. Natl. Acad. Sci. USA, 92, 15151519.[Abstract]
Faller,G., Steiniger,H., Appelmelk,B. and Kirchner,T. (1998) Evidence of novel pathogenic pathways for the formation of antigastric antibodies in Helicobacter pylori gastritis. J. Clin. Pathol., 51, 244245.[Abstract]
Fischer,W., Schwan,D., Gerland,E., Erlenfeld,G.E., Odenbreit,S. and Haas,R. (1999) A plasmid-based vector system for the cloning and expression of Helicobacter pylori genes encoding outer membrane proteins. Mol. Gen. Genet., 262, 501507.[ISI][Medline]
Fleishmann,R.D., Adams,M.D., White,O., Clayton,R.A., Kirkness,E.F., Kerlavage,A.R., Butt,C.J., Tomb,C.J., Doughtery,B.A., Merrick,J.M. and others. (1995) The genome of Haemophilus influenzae Rd. Science, 269, 496512.[ISI][Medline]
Fox,J.G., Dangler,C.A., Taylor,N.S., King,A., Koh,T.J. and Wang,T.C. (1999) High-salt diet induces gastric epithelial hyperplasia and parietal cell loss and enhances Helicobacter pylori colonization in C57BL/6 mice. Cancer Res., 59, 48234828.
Gagneux,P. and Varki,A. (1999) Evolutionary considerations in relating oligosaccharide diversity to biological function. Glycobiology, 9, 747755.
Gasbarrini,A. and Franceschi,F. (1999) Autoimmune diseases and Helicobacter pylori infection. Biomed. Pharmacother., 53, 223226.[ISI][Medline]
Ge,Z. and Taylor,D.E. (1999) Contributions of genome sequencing to understanding the biology of Helicobacter pylori. Annu. Rev. Microbiol., 53, 353387.[ISI][Medline]
Gerhard,M., Lehn,N., Neumayer,N., Borén,T., Rad,R., Schepp,W., Miehlke,S., Classen,M. and Prinz,C. (1999) Clinical relevance of the Helicobacter pylori gene for blood group antigen-binding adhesin. Proc. Natl. Acad. Sci. USA, 96, 1277812783.
Gold,B., Huesca,M., Sherman,P. and Lingwood,C.A. (1993) Helicobacter mustelae and Helicobacter pylori bind to common receptors in vitro. Infect. Immun., 61, 26322638.[Abstract]
Gupta,S.K., Berk,R.S., Masinick,S. and Hazlett,L.D. (1994) Pili and lipopolysaccharide of Pseudomonas aeruginosa bind to the glycolipid asialo GM1. Infect. Immun., 62, 45724579.[Abstract]
Guruge,J.L., Falk,P.G., Lorenz,R.G., Dans,M., Wirth,H.-P., Blaser,M.J., Berg,D.E. and Gordon,J.I. (1998) Epithelial attachment alters the outcome of Helicobacter pylori infection. Proc. Natl. Acad. Sci. USA, 95, 39253930.
Hakomori,S.-i. (1996) Tumor malignancy defined by aberrant glycosylation and sphingo (glyco)lipid metabolism. Cancer Res., 56, 53095318.[Abstract]
Hansen,P.S., Go,M.F., Varming,K., Andersen,L.P., Graham,D.Y. and Nielsen,H. (1999) Proinflammatory activation of neutrophils and monocytes by Helicobacter pylori is not associated with cagA, vacA or picB genotypes. APMIS, 107, 11171123.[ISI][Medline]
Henderson,I.R., Owen,P. and Nataro,J.P. (1999) Molecular switchesthe ON and OFF of bacterial phase variation. Mol. Microbiol., 33, 919932.[ISI][Medline]
Heneghan,M.A., McCarthy,C.F. and Moran,A.P. (2000) Relationship of blood group determinants on Helicobacter pylori lipopolysaccharide with host Lewis phenotype and inflammatory response. Infect. Immun., 68, 937941.
Hirmo,S., Kelm,S., Schauer,R., Nilsson,B. and Wadström,T. (1996) Adhesion of Helicobacter pylori strains to -2,3-linked sialic acids. Glycoconj. J., 13, 17.[ISI][Medline]
Hood,D.W., Makepeace,K., Deadman,M.E., Rest,R.F., Thiebault,P., Martin,A., Richards,J. and Moxon,E.R. (1999) Sialic acid in the lipopolysaccharide of Haemophilus influenzae: strain distribution, influence on serum resistance and structural characterization. Mol. Microbiol., 33, 679692.[ISI][Medline]
Huesca,M., Borgia,S., Hoffman,P. and Lingwood,C.A. (1996) Acidic pH changes receptor binding specificity of Helicobacter pylori: a binary adhesion model in which surface heat shock (stress) proteins mediate sulfatide recognition in gastric colonization. Infect. Immun., 64, 26432648.[Abstract]
Ilver,D., Arnqvist,A., Ögren,J., Frick,I.-M., Kersulyte,D., Incecik,E.T., Berg,D.E., Covacci,A., Engstrand,L. and Borén,T. (1998) Helicobacter pylori adhesin binding fucosylated histo-blood group antigens revealed by retagging. Science, 279, 373377.
Jacques,M. (1996) Role of lipo-oligosaccharides and lipopolysaccharides in bacterial adherence. Trends Microbiol., 4, 408410.[ISI][Medline]
Johansson,L. and Karlsson,K.-A. (1998) Selective binding by Helicobacter pylori of leukocyte gangliosides with 3-linked sialic acid, as identified by a new approach of linkage analysis. Glycoconj. J., 15, 713721.[ISI][Medline]
Johansson,L., Johansson,P. and Miller-Podraza,H. (1999) Neu5Ac3Gal is part of the Helicobacter pylori binding epitope in polyglycosylceramides of human erythrocytes. Eur. J. Biochem., 266, 559565.
Jones,A.C., Logan,R.P.H., Foynes,S., Cockayne,A., Wren,B.W. and Penn,C.W. (1997) A flagellar sheath protein of Helicobacter pylori is identical to HpaA, a putative N-acetylneuraminyllactose-binding hemagglutinin, but is not an adhesin for AGS cells. J. Bacteriol., 179, 56435647.[Abstract]
Kamisago,S., Iwamori,M., Tai,T., Mitamura,K., Yazaki,Y. and Sugano,K. (1996) Role of sulfatides in adhesion of Helicobacter pylori to gastric cancer cells. Infect. Immun., 64, 624628.[Abstract]
Kamiya,K., Arisawa,T., Goto,H., Shibayama,K., Horii,T., Hayakawa,T. and Ota,M. (1999) Are autoantibodies against Lewis antigens involved in the pathogenesis of Helicobacter pylori-induced peptic ulcers? Microbiol. Immunol., 43, 403408.[ISI][Medline]
Karlsson,K.-A. (1998) Meaning and therapeutic potential of microbial recognition of host glycoconjugates. Mol. Microbiol., 29, 111.[ISI][Medline]
Karlsson,H., Johansson,L., Miller-Podraza,H. and Karlsson,K.-A. (1999) Fingerprinting of large oligosaccharides linked to ceramide by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: highly heterogeneous polyglycosylceramides of human erythrocytes with receptor activity for Helicobacter pylori. Glycobiology, 9, 765778.
Kim,J.S., Jung,H.C., Kim,J.M., Song,I.S. and Kim,C.Y. (2000) Helicobacter pylori water-soluble surface proteins activate human neutrophils and up-regulate expression of CXC chemokines. Dig. Dis. Sci., 45, 8392.[ISI][Medline]
Kirkland,T., Viriyakosol,S., Perez-Perez,G.I. and Blaser,M.J. (1997) Helicobacter pylori lipopolysaccharide can activate 70Z/3 cells via CD14. Infect. Immun., 655, 604608.
Knirel,Y.A., Kocharova,N.A., Hynes,S.O., Widmalm,G., Andersen,L.P., Jansson,P.-E. and Moran,A.P. (1999) Structural studies on lipopolysaccharides of serologically non-typable strains of Helicobacter pylori, AF1 and 007, expressing Lewis antigenic determinants. Eur. J. Biochem., 266, 123131.
Langermann,S., Palaszynski,S., Barnhart,M., Auguste,G., Pinkner,J.S., Burlein,J., Barren,P., Koenig,S., Leath,S., Jones,C.H. and Hultgren,S. (1997) Prevention of mucosal Escherichia coli infection by FimH-adhesin-based systemic vaccination. Science, 276, 607611.
Langermann,S., Möllby,R., Burlein,J.E., Palaszynski,S.R., Auguste,C.G., DeFusco,A., Strouse,R., Schenerman,M.A., Hultgren,S.J., Pinkner,J.S. and others. (2000) Vaccination with FimH adhesin protects cynomolgus monkeys from colonization and infection by uropathogenic Escherichia coli. J. Infect. Dis., 181, 774778.[ISI][Medline]
Larsson,T., Bergström,J., Nilsson,C. and Karlsson,K.-A. (2000) Use of an affinity proteomics approach for the identification of low-abundant bacterial adhesins as applied on the Lewis b-binding adhesin of Helicobacter pylori. FEBS Lett., 469, 155158.[ISI][Medline]
Laver,W.G., Bischofberger,N. and Webster,R.G. (1999) Disarming flu viruses. Sci. Am., 280, 5665.[Medline]
Lazowska,I., Trzeciak,L., Godlewska,R., Hennig,E., Jagusztyn-Krynicka,K., Popowski,J, Regula,J. and Ostrowski,J. (2000) In search of immunogenic Helicobacter pylori proteins by screening of expression library. Digestion, 61, 1421.[ISI][Medline]
Lingwood,C.A., Huesca,M. and Kuskis,A. (1992) The glycerolipid receptor for Helicobacter pylori (and exoenzyme S) is phosphatidylethanolamine. Infect. Immun., 60, 24702474.[Abstract]
Marais,A., Mendz,G.L., Hazell,S.L. and Mégraud,F. (1999) Metabolism and genetics of Helicobacter pylori: the genome era. Microbiol. Rev., 63, 642674.
Marshall,B.J. and Warren,J.R. (1984) Unidentified curved bacilli in the stomach of patients with gastritis and peptic ulceration. Lancet, 1, 13111315.[ISI][Medline]
Masamune,A., Shimosegawa,T., Masamune,O., Mukaida,N., Koizumi,M. and Toyota,T. (1999) Helicobacter pylori-dependent ceramide production may mediate increased interleukin 8 expression in human gastric cancer cell lines. Gastroenterology, 116, 13301341.[ISI][Medline]
McAuliffe,J.C. and Hindsgaul,O. (1997) Carbohydrate drugsan ongoing challenge. Chem. Industry, 1, 170174.
Michetti,P., Kreiss,C., Kotloff,K.L., Porta,N., Blanco,J.-L., Bachmann,D., Herranz,M., Saldinger,P.F., Corthésy-Theulaz,I., Losonsky,G. and others. (1999) Oral immunization with urease and Escherichia coli heat-labile enterotoxin is safe and immunogenic in Helicobacter pylori-infected adults. Gastroenterology, 116, 804812.[ISI][Medline]
Miller-Podraza,H., Abul Milh,M., Bergström,J. and Karlsson,K.-A. (1996) Recognition of glycoconjugates by Helicobacter pylori: an apparently high-affinity binding of human polyglycosylceramides, a second sialic acid-based specificity. Glycoconj. J., 13, 453460.[ISI][Medline]
Miller-Podraza,H., Bergström,J., Abul Milh,M. and Karlsson,K.-A. (1997) Recognition of glycoconjugates by Helicobacter pylori. Comparison of two sialic acid-dependent specificities based on hemagglutination and binding to human erythrocyte glycoconjugates. Glycoconj. J., 14, 467471.[ISI][Medline]
Miller-Podraza,H., Larsson,T., Nilsson,J., Teneberg,S., Matrosovich,M. and Johansson,L. (1998) Epitope dissection of receptor-active gangliosides with affinity for Helicobacter pylori and influenza virus. Acta Biochim. Polon., 45, 439449.[ISI][Medline]
Miller-Podraza,H., Bergström,J., Teneberg,S., Abul Milh,M., Longard,M., Olsson,B.-M., Uggla,L. and Karlsson,K.-A. (1999) Helicobacter pylori and neutrophils: sialic acid-dependent binding to various isolated glycoconjugates. Infect. Immun., 67, 63096313.
Monteiro,M.A., Zheng,P.Y., Appelmelk,B.J. and Perry,M.B. (1997) The lipopolysaccharide of H.mustelae type strain ATCC 43772 expresses the monofucosyl A type 1 histo-blood group epitope. FEMS Microbiol. Lett., 154, 103109.[ISI][Medline]
Monteiro,M.A., Chan,K.H.N., Rasko,D.A., Taylor,D.E., Zheng,P.Y., Appelmelk,B.J., Wirth,H.-P., Yang,M., Blaser,M.J., Hynes,S.O. and others. (1998) Simultaneous expression of type 1 and type 2 Lewis blood group antigens by Helicobacter pylori lipopolysaccharides. J. Biol. Chem., 273, 1153311543.
Monteiro,M.A., Appelmelk,B.J., Rasko,D.A., Moran,A.P., Hynes,S.O., MacLean,L.L., Chan,K.H., Michael,F.S., Logan,S.M., ORourke,J. and others. (2000) 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. Eur. J. Biochem., 267, 305320.
Mooney,C., Keenan,J., Munster,D., Wilson,I., Allardyce,R., Bagshaw,P., Chapman,B. and Chadwick,V. (1991) Neutrophil activation by Helicobacter pylori. Gut, 32, 853857.[Abstract]
Mysore,J.V., Wigginton,T., Simon,P.M., Zopf,D., Heman-Ackah,L.M. and Dubois,A. (1999) Treatment of Helicobacter pylori infection in Rhesus monkeys using a novel antiadhesion compound. Gastroenterology, 117, 13161325.[ISI][Medline]
Namavar,F., Sparrius,M., Veerman,E.C.I., Appelmelk,B.J. and Vandenbroucke-Grauls,C.M.J.E. (1998) Neutrophil-activating protein mediates adhesion of Helicobacter pylori to sulfated carbohydrates on high-molecular-weight salivary mucin. Infect. Immun., 66, 444447.
Naumann,M., Wessler,S., Bartsch,C., Wieland,B., Covacci,A., Haas,R. and Meyer,T.F. (1999) Activation of activator protein 1 and stress response kinases in epithelial cells colonized by Helicobacter pylori encoding the cag pathogenicity island. J. Biol. Chem., 274, 3165531662.
Nedrud,J.G. (1999) Animal models for gastric Helicobacter immunology and vaccine studies. FEMS Immunol. Med. Microbiol., 24, 243250.[ISI][Medline]
Odenbreit,S., Till,M., Hofreuter,D., Faller,G. and Haas,R. (1999) Genetic and functional characterization of the alpAB gene locus essential for the adhesion of Helicobacter pylori to human gastric tissue. Mol. Microbiol., 31, 15371548.[ISI][Medline]
Odenbreit,S., Püls,J., Sedlmaier,B., Gerland,E., Fischer,W. and Haas,R. (2000) Translocation of Helicobacter pylori CagA into gastric epithelial cells by type IV secretion. Science, 287, 14971500.
Ota,H., Nakayama,J., Momose,M., Hayama,M., Akamatsu,T., Katsuyama,T., Graham,D.Y. and Genta,R.M. (1998) Helicobacter pylori infection produces reversible glycosylation changes to gastric mucins. Virch. Arch., 433, 419426.[ISI]
OToole,P.W., Janzon,L., Doig,P., Huang,J., Kostrzynska,M. and Trust,T. (1995) The putative nauraminyllactose-binding hemagglutinin HpaA of Helicobacter pylori CCUG 17874 is a lipoprotein. J. Bacteriol., 177, 60496057.[Abstract]
Pawlowski,K., Zhang,B., Rychlewski,L. and Godzik,A. (1999) The Helicobacter pylori genome: from sequence analysis to structural and functional predictions. Proteins: Struct. Funct. Genetics, 36, 2030.
Preston,A., Mandrell,R.E., Gibson,B.W. and Apicella,M.A. (1996) The lipooligosaccharides of pathogenic Gram-negative bacteria. Crit. Rev. Microbiol., 22, 139180.[ISI][Medline]
Putsep,K., Branden,C.-I., Boman,H.G. and Normark,S. (1999a) Antibacterial peptide from H.pylori. Nature, 398, 671672.[ISI][Medline]
Putsep,K., Normark,S. and Boman,H.G. (1999b) The origin of cecropins; implications from synthetic peptides derived from ribosomal protein L1. FEBS Lett., 451, 249252.[ISI][Medline]
Rasko,D.A., Wang,G., Palcic,M. and Taylor,D.E. (2000a) Cloning and characterization of the (1,3/4) fucosyltransferase of Helicobacter pylori. J. Biol. Chem., 275, 49884994.
Rasko,D.A., Wilson,T.J.M., Zopf,D. and Taylor,D.E. (2000b) Lewis antigen expression and stability in Helicobacter pylori isolated from serial gastric biopsies. J. Infect. Dis., 181, 10891095.
Rautelin,H., Blomberg,B., Fredlund,H., Järnerot,G. and Danielsson,D. (1993) Incidence of Helicobacter pylori strains activating neutrophils in patients with peptic ulcer disease. Gut, 34, 599603.[Abstract]
Reyrat,J.-M., Pelicic,V., Papini,E., Montecucco,C., Rappuoli,R. and Telford,J.L. (1999) Towards deciphering the Helicobacter pylori cytotoxin. Mol. Microbiol., 34, 197204.[ISI][Medline]
Risberg,A., Masoud,H., Martin,A., Richards,J., Moxon,E.R. and Schweda,E.K.H. (1999) Structural analysis of the lipopolysaccharide epitopes expressed by a capsule-deficient strain of Haemophilus influenzae Rd. Eur. J. Biochem., 261, 171180.
Saitoh,T., Natomi,H., Zhao,W., Okuzumi,K., Sugano,K., Iwamori,M. and Nagai,Y. (1991) Identification of glycolipid receptors for Helicobacter pylori by TLC immunostaining. FEBS Lett., 282, 385387.[ISI][Medline]
Sears,P. and Wong,C.-H. (1999) Carbohydrate mimetics: a new strategy for tackling the problem of carbohydrate-mediated biological recognition. Angew. Chem. Int. Ed., 38, 23002324.
Segal,E.D., Cha,J., Lo,J. Falkow,S. and Tompkins,L.S. (1999) Altered states: Involvement of phosphorylated CagA in the induction of host cellular growth changes by Helicobacter pylori. Proc. Natl. Acad. Sci. USA, 96, 1459914564.
Simon,P.M., Goode,P.L., Mobasseri,A. and Zopf,D. (1997) Inhibition of Helicobacter pylori binding to gastrointestinal epithelial cells by sialic acid-containing oligosaccharides. Infect. Immun., 65, 750757.[Abstract]
Spillman,D. and Burger,M.M. (2000) Carbohydrate/carbohydrate interactions. In Ernst,B., Hart,G. and Sinay,P. (eds.), Oligosaccharides in Chemistry and Biology: A Comprehensive Handbook. WILEY-VCH Verlag, forthcoming.
Stein,M., Rappuoli,R. and Covacci,A. (2000) Tyrosine phosphorylation of the Helicobacter pylori CagA antigen after cag-driven host cell translocation. Proc. Natl. Acad. Sci. USA, 97, 12631268.
Su,B., Johansson,S., Fällman,M., Patarroyo,M., Granström,M. and Normark,S. (1999) Signal transduction-mediated adherence and entry of Helicobacter pylori into cultured cells. Gastroenterology, 117, 595604.[ISI][Medline]
Syder,A.J., Guruge,J.L., Li,Q., Hu,Y., Oleksiewicz,C.M., Lorenz,R.G., Karam,S.M., Falk,P.G. and Gordon,J.I. (1999) Helicobacter pylori attaches to NeuAc2,3Galß1,4 glycoconjugates produced in the stomach of transgenic mice lacking parietal cells. Mol. Cell, 3, 263274.[ISI][Medline]
Teneberg,S., Miller-Podraza,H., Lampert,H.C., Evans,D.C., Jr, Evans,D.G., Danielsson,D. and Karlsson,K.-A. (1997) Carbohydrate binding specificity of the neutrophil-activating protein of Helicobacter pylori. J. Biol. Chem., 272, 1906719071.
Tomb,J.-F., White,O., Kerlavage,A.R., Clayton,R.A., Sutton,G.G., Fleishmann,R.D., Ketchum,K.A., Klenk,H.P., Gill,S., Dougherty,B.A. and others. (1997) The complete genome sequence of the gastric pathogen Helicobacter pylori. Nature, 388, 539547.[ISI][Medline]
Tonello,F., Dundon,W.G., Satin,B., Molinari,M., Tognon,G., Grandi,G., Del Giudice,G., Rappuoli,R. and Montecucco,C. (1999) The Helicobacter pylori neutrophil-activating protein is an iron-binding protein with dodecameric structure. Mol. Microbiol., 34, 238246.[ISI][Medline]
Utt,M. and Wadström,T. (1997) Identification of heparan sulphate binding proteins of Helicobacter pylori: inhibition of heparan sulphate with sulphated carbohydrate polymers. J. Med. Microbiol., 46, 541546.[Abstract]
Valkonen,K.H., Wadström,T. and Moran,A.P. (1994) Interaction of lipopolysaccharides of Helicobacter pylori with basement membrane protein laminin. Infect. Immun., 62, 36403648.[Abstract]
Valkonen,K.H., Wadström,T. and Moran,A.P. (1997) Identification of the N-acetylneuraminyllactose-specific laminin-binding protein of Helicobacter pylori. Infect. Immun., 65, 916923.[Abstract]
van Doorn,N.E.M., Namavar,F., Sparrius,M., Stoof,J., van Rees,E.P., van Doorn,L.-J. and Vandenbroucke-Grauls,C.M.J.E. (1999) Helicobacter pylori-associated gastritis in mice is host and strain specific. Infect. Immun., 67, 30403046.
Wade,R.C. (1997) Flu and structure-based drug design. Structure, 5, 11391145.[ISI][Medline]
Wadström,T. and Hänninen,M.-L. (1999) Other helicobacters in the digestive tract. Curr. Opin. Gastroenterol., 15, S53S56.[ISI]
Wang,G., Boulton,P.G., Chan,N.W.C., Palcic,M. and Taylor,D.E. (1999a) Novel Helicobacter pylori 1,2-fucosyltransferase, a key enzyme in the synthesis of of Lewis antigens. Microbiology, 145, 32453253.
Wang,G., Rasko,D.A., Sherburne,R. and Taylor,D.E. (1999b) Molecular genetic basis for the variable expression of the Lewis y antigen in Helicobacter pylori: analysis of the (1,2) fucosyltransferase gene. Mol. Microbiol., 31, 12651274.[ISI][Medline]
Warren,J.R. and Marshall,B.J. (1983) Unidentified curved bacilli on gastric epithelium in active chronic gastritis. Lancet, 1, 12731275.[ISI][Medline]
Weiser,J.N., Pan,N., McGowan,K.L., Musher,D., Martin,A. and Richards,J. (1998) Phosphorylcholine on the lipopolysaccharide of Haemophilus influenzae contributes to persistence in the respiratory tract and sensitivity to serum killing mediated by C-reactive protein. J. Exp. Med., 187, 631640.
Westblom,T.U., Czinn,S.J. and Nedrud,J.G. (eds.) (1999) Gastroduodenal Disease and Helicobacter pylori. Pathophysiology, Diagnosis and Treatment. Curr. Top. Microbiol. Immunol. 241. Springer-Verlag, Berlin.
Wirth,H.-P., Yang,M., Karita,M. and Blaser,M.J. (1996) Expression of the human cell surface glycoconjugates Lewis x and Lewis y by Helicobacter pylori isolates is related to cagA status. Infect. Immun., 64, 45984605.[Abstract]
Wirth,H.-P., Yang,M., Peek,R.M., Hook-Nikanne,J. and Blaser,M.J. (1997) Phenotypic diversity in Lewis expression of H.pylori colonies derived from the same biopsy. Gastroenterology, 112, A331.
Wirth,H.-P., Yang,M., Peek,R.M., Hook-Nikanne,J., Fried,M. and Blaser,M.J. (1999) Phenotype diversity in Lewis expression of Helicobacter pylori isolates from the same host. J. Lab. Clin. Med., 133, 488500.[ISI][Medline]
Wizemann,T.M., Adamou,J.E. and Langermann,S. (1999) Adhesins as targets for vaccine development. Emerg. Inf. Dis., 5, 395403.[ISI][Medline]
Yoshida,N., Granger,D.N., Evans,D.J.,Jr., Evans,D.G., Graham,D.Y., Anderson,D.C., Wolf,R.E. and Kvietys,P.R. (1993) Mechanisms involved in Helicobacter pylori-induced inflammation. Gastroenterology, 105, 14311440.[ISI][Medline]
Zevering,Y., Jacob,L. and Meyer,T.F. (1999) Naturally aquired human immune responses against Helicobacter pylori and implications for vaccine development. Gut, 45, 465474.
Zopf,D. and Roth,S. (1996) Oligosaccharide anti-infective agents. Lancet, 347, 10171021.[ISI][Medline]