Influence of Lewis antigen expression by Helicobacter pylori on bacterial internalization by gastric epithelial cells

A large cohort study of the effects of Lewis, ABO, 13 other blood groups, and secretor status on COVID-19 susceptibility, severity, and long COVID-19

BACKGROUND

Previous studies have reported Blood type O to confer a lower risk of SARS-CoV-2 infection, while secretor status and other blood groups have been suspected to have a similar effect as well.

STUDY DESIGN AND METHODS

To determine whether any other blood groups influence testing positive for SARS-CoV-2, COVID-19 severity, or prolonged COVID-19, we used a large cohort of 650,156 Danish blood donors with varying available data for secretor status and blood groups ABO, Rh, Colton, Duffy, Diego, Dombrock, Kell, Kidd, Knops, Lewis, Lutheran, MNS, P1PK, Vel, and Yt. Of these, 36,068 tested positive for SARS-CoV-2 whereas 614,088 tested negative between 2020-02-17 and 2021-08-04. Associations between infection and blood groups were assessed using logistic regression models with sex and age as covariates.

RESULTS

The Lewis blood group antigen Le^a displayed strongly reduced SARS-CoV-2 susceptibility OR 0.85 CI[0.79-0.93] p < .001. Compared to blood type O, the blood types B, A, and AB were found more susceptible toward infection with ORs 1.1 CI[1.06-1.14] p < .001, 1.17 CI[1.14-1.2] p < .001, and 1.2 CI[1.14-1.26] p < .001, respectively. No susceptibility associations were found for the other 13 blood groups investigated. There was no association between any blood groups and COVID-19 hospitalization or long COVID-19. No secretor status associations were found.

DISCUSSION

This study uncovers a new association to reduced SARS-CoV-2 susceptibility for Lewis type Le^a and confirms the previous link to blood group O. The new association to Le^a could be explained by a link between mucosal microbiome and SARS-CoV-2.

Helicobacter pylori and the Role of Lipopolysaccharide Variation in Innate Immune Evasion

Helicobacter pylori is an important human pathogen that infects half the human population and can lead to significant clinical outcomes such as acute and chronic gastritis, duodenal ulcer, and gastric adenocarcinoma. To establish infection, H. pylori employs several mechanisms to overcome the innate and adaptive immune systems. H. pylori can modulate interleukin (IL) secretion and innate immune cell function by the action of several virulence factors such as VacA, CagA and the type IV secretion system. Additionally, H. pylori can modulate local dendritic cells (DC) negatively impacting the function of these cells, reducing the secretion of immune signaling molecules, and influencing the differentiation of CD4⁺ T helper cells causing a bias to Th1 type cells. Furthermore, the lipopolysaccharide (LPS) of H. pylori displays a high degree of phase variation and contains human blood group carbohydrate determinants such as the Lewis system antigens, which are proposed to be involved in molecular mimicry of the host. Lastly, the H. pylori group of outer membrane proteins such as BabA play an important role in attachment and interaction with host Lewis and other carbohydrate antigens. This review examines the various mechanisms that H. pylori utilises to evade the innate immune system as well as discussing how the structure of the H. pylori LPS plays a role in immune evasion.

Lewis and ABO histo-blood types and the secretor status of patients hospitalized with COVID-19 implicate a role for ABO antibodies in susceptibility to infection with SARS-CoV-2

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) targets the respiratory and gastric epithelium, causing coronavirus disease 2019 (COVID-19). Tissue antigen expression variations influence host susceptibility to many infections. This study aimed to investigate the closely linked Lewis (FUT3) and ABO histo-blood types, including secretor (FUT2) status, to infections with SARS-CoV-2 and the corresponding severity of COVID-19.

STUDY DESIGN AND METHODS

Patients (Caucasians, n = 338) were genotyped for ABO, FUT3, and FUT2, and compared to a reference population of blood donors (n = 250,298). The association between blood types and severity of COVID-19 was addressed by dividing patients into four categories: hospitalized individuals in general wards, patients admitted to the intensive care unit with and without intubation, and deceased patients. Comorbidities were considered in subsequent analyses.

RESULTS

Patients with blood type Lewis (a-b-) or O were significantly less likely to be hospitalized (odds ratio [OR] 0.669, confidence interval [CI] 0.446-0.971, OR 0.710, CI 0.556-0.900, respectively), while type AB was significantly more prevalent in the patient cohort (OR 1.519, CI 1.014-2.203). The proportions of secretors/nonsecretors, and Lewis a+ or Lewis b+ types were consistent between patients and controls. The analyzed blood groups were not associated with the clinical outcome as defined.

DISCUSSION

Blood types Lewis (a-b-) and O were found to be protective factors, whereas the group AB is suggested to be a risk factor for COVID-19. The antigens investigated may not be prognostic for disease severity, but a role for ABO isoagglutinins in SARS-CoV-2 infections is strongly suggested.

Structural analysis of carbohydrate binding by the macrophage mannose receptor CD206

The human mannose receptor expressed on macrophages and hepatic endothelial cells scavenges released lysosomal enzymes, glycopeptide fragments of collagen, and pathogenic microorganisms and thus reduces damage following tissue injury. The receptor binds mannose, fucose, or N-acetylglucosamine (GlcNAc) residues on these targets. C-type carbohydrate-recognition domain 4 (CRD4) of the receptor contains the site for Ca2+-dependent interaction with sugars. To investigate the details of CRD4 binding, glycan array screening was used to identify oligosaccharide ligands. The strongest signals were for glycans that contain either Manα1-2Man constituents or fucose in various linkages. The mechanisms of binding to monosaccharides and oligosaccharide substructures present in many of these ligands were examined in multiple crystal structures of CRD4. Binding of mannose residues to CRD4 results primarily from interaction of the equatorial 3- and 4-OH groups with a conserved principal Ca2+ common to almost all sugar-binding C-type CRDs. In the Manα1-2Man complex, supplementary interactions with the reducing mannose residue explain the enhanced affinity for this disaccharide. Bound GlcNAc also interacts with the principal Ca2+ through equatorial 3- and 4-OH groups, whereas fucose residues can bind in several orientations, through either the 2- and 3-OH groups or the 3- and 4-OH groups. Secondary contacts with additional sugars in fucose-containing oligosaccharides, such as the Lewis-a trisaccharide, provide enhanced affinity for these glycans. These results explain many of the biologically important interactions of the mannose receptor with both mammalian glycoproteins and microbes such as yeast and suggest additional classes of ligands that have not been previously identified.

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

The Possible Role of Helicobacter pylori in Gastric Cancer and Its Management

Helicobacter pylori (HP) is a facultative anaerobic bacterium. HP is a normal flora having immuno-modulating properties. This bacterium is an example of a microorganism inducing gastric cancer. Its carcinogenicity depends on bacteria-host related factors. The proper understanding of the biology of HP inducing gastric cancer offers the potential strategy in the managing of HP rather than eradicating it. In this article, we try to summarize the biology of HP-induced gastric cancer and discuss the current pharmacological approach to treat and prevent its carcinogenicity.

The Biosynthesis of Lipooligosaccharide from Bacteroides thetaiotaomicron

Lipopolysaccharide (LPS), a cell-associated glycolipid that makes up the outer leaflet of the outer membrane of Gram-negative bacteria, is a canonical mediator of microbe-host interactions. The most prevalent Gram-negative gut bacterial taxon, Bacteroides, makes up around 50% of the cells in a typical Western gut; these cells harbor ~300 mg of LPS, making it one of the highest-abundance molecules in the intestine. As a starting point for understanding the biological function of Bacteroides LPS, we have identified genes in Bacteroides thetaiotaomicron VPI 5482 involved in the biosynthesis of its lipid A core and glycan, generated mutants that elaborate altered forms of LPS, and used matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry to interrogate the molecular features of these variants. We demonstrate, inter alia, that the glycan does not appear to have a repeating unit, and so this strain produces lipooligosaccharide (LOS) rather than LPS. This result contrasts with Bacteroides vulgatus ATCC 8482, which by SDS-PAGE analysis appears to produce LPS with a repeating unit. Additionally, our identification of the B. thetaiotaomicron LOS oligosaccharide gene cluster allowed us to identify similar clusters in other Bacteroides species. Our work lays the foundation for developing a structure-function relationship for Bacteroides LPS/LOS in the context of host colonization.

Much is known about the bacterial species and genes that make up the human microbiome, but remarkably little is known about the molecular mechanisms through which the microbiota influences host biology. A well-known mechanism by which bacteria influence the host centers around lipopolysaccharide (LPS), a component of the Gram-negative bacterial outer membrane. Pathogen-derived LPS is a potent ligand for host receptor Toll-like receptor 4, which plays an important role in sensing bacteria as part of the innate immune response. Puzzlingly, the most common genus of human gut bacteria, Bacteroides, produces LPS but does not elicit a potent proinflammatory response. Previous work showing that Bacteroides LPS differs structurally from pathogen-derived LPS suggested the outlines of an explanation. Here, we take the next step, elucidating the biosynthetic pathway for Bacteroides LPS and generating mutants in the process that will be of great use in understanding how this molecule modulates the host immune response.

Adhesion and Invasion of Gastric Mucosa Epithelial Cells by Helicobacter pylori

Helicobacter pylori is the main pathogenic bacterium involved in chronic gastritis and peptic ulcer and a class 1 carcinogen in gastric cancer. Current research focuses on the pathogenicity of H. pylori and the mechanism by which it colonizes the gastric mucosa. An increasing number of in vivo and in vitro studies demonstrate that H. pylori can invade and proliferate in epithelial cells, suggesting that this process might play an important role in disease induction, immune escape and chronic infection. Therefore, to explore the process and mechanism of adhesion and invasion of gastric mucosa epithelial cells by H. pylori is particularly important. This review examines the relevant studies and describes evidence regarding the adhesion to and invasion of gastric mucosa epithelial cells by H. pylori.

Synthesis and analysis of potential α1,3-fucosyltransferase inhibitors

Fucosyltransferases catalyze the transfer of l-fucose from an activated GDP-β-l-fucose to various acceptor molecules such as N-acetyllactosamine. Frequently fucosylation is the final step within the glycosylation machinery, and the resulting glycans are involved in various cellular processes such as cell-cell recognition, adhesion and inflammation or tumor metastasis. The selective blocking of these interactions would thus be a potential promising therapeutic strategy. The syntheses and analyses of various potential α1,3-fucosyltransferase inhibitors derived from GDP-β-l-fucose containing a triazole linker unit is summarized and the observed inhibitory effect was compared with that of small molecules such as GDP or fucose. To examine their specificity and selectivity, all inhibitors were tested with human α1,3-fucosyltransferase IX and Helicobacter pylori α1,3-fucosyltransferase, which is to date the only α1,3-fucosyltransferase with a known high resolution structure. Specific inhibitors which inhibit either H. pylori α1,3-fucosyltransferase or human fucosyltransferase IX with Ki values in the micromolar range were identified. In that regard, acetylated GDP-galactose derivative Ac-3 turned out to inhibit H. pylori α1,3-fucosyltransferase but not human fucosyltransferase IX, whereas GDP-6-amino-β-l-fucose 17 showed an appreciably better inhibitory effect on fucosyltransferase IX activity than on that of H. pylori fucosyltransferase.

Human lactoferrin increases Helicobacter pylori internalisation into AGS cells

Helicobacter pylori has high global infection rates and can cause other undesirable clinical manifestations such as duodenal ulcer (DU) and gastric cancer (GC). Frequencies of re-infection after therapeutic clearance and rates of DU versus GC vary geographically and differ markedly between developed and developing countries, which suggests additional factors may be involved. The possibility that, in vivo, lactoferrin (Lf) may play a subtle role in modulating micronutrient availability or bacterial internalisation with implications for disease etiology is considered. Lf is an iron binding protein produced in mammals that has antimicrobial and immunomodulatory properties. Some bacteria that regularly colonise mammalian hosts have adapted to living in high Lf environments and we investigated if this included the gastric pathogen H. pylori. We found that H. pylori was able to use iron from fully iron-saturated human Lf (hLf) whereas partially iron-saturated hLf (apo) did not increase H. pylori growth. Instead, apo-hLf increased adherence to and internalisation of bacteria into cultured epithelial cells. By increasing internalisation, we speculate that apo-human lactoferrin may contribute to H. pylori's ability to persistence in the human stomach, an observation that potentially has implications for the risk of H. pylori-associated disease.

Host-dependent Lewis (Le) antigen expression in Helicobacter pylori cells recovered from Leb-transgenic mice

Variation of surface antigen expression is a mechanism used by microbes to adapt to and persist within their host habitats. Helicobacter pylori, a persistent bacterial colonizer of the human stomach, can alter its surface Lewis (Le) antigen expression. We examined H. pylori colonization in mice to test the hypothesis that host phenotype selects for H. pylori (Le) phenotypes. When wild-type and Le^b-expressing transgenic FVB/N mice were challenged with H. pylori strain HP1, expressing Le^x and Le^y, we found that bacterial populations recovered after 8 mo from Le^b-transgenic, but not wild-type, mice expressed Le^b. Changes in Le phenotype were linked to variation of a putative galactosyltransferase gene (β-(1,3)galT); mutagenesis and complementation revealed its essential role in type I antigen expression. These studies indicate that H. pylori evolves to resemble the host's gastric Le phenotype, and reveal a bacterial genetic locus that is subject to host-driven selection pressure.

Genomic diversity in Helicobacter and related organisms

The human gastric pathogen Helicobacter pylori possesses an enormous genomic plasticity and diversity that facilitates host adaptation. Despite the ancient association with its human host, this epsilon-proteobacterium can cause gastritis, ulcers and gastric cancer. Here we focus on multiple aspects of the genome level biology, from population genomics to re-evaluating the genus definition.

Helicobacter pylori cagA and iceA genotypes status and risk of peptic ulcer in Saudi patients

OBJECTIVE

To determine the prevalence of cagA+ and iceA genotypes among Helicobacter pylori (H. pylori) isolates from a group of Saudi patients with gastric complaints, and to find out any significant correlation between these strains and severe gastric clinical outcomes such as peptic ulcer and gastric cancer in Saudi population.

METHODS

A total of 1104 gastric biopsies from 368 patients who presented with symptoms suggestive of chronic gastritis, peptic ulcer disease, or gastric carcinoma were taken from the main hospitals in the Western region of Saudi Arabia from July 2004 to July 2005. We cultured the samples for H. pylori and a polymerase chain reaction was carried out to check for the presence or absence of cagA gene and the status of iceA genotypes.

RESULTS

Among the 368 suspected patients to be infected with H. pylori by means of clinical features and endoscopic findings; 103 (28%) were positive using culture technique. The relation of the presence of cagA and the development of cases to gastritis and ulcer was statistically significant (p=0.0001). Furthermore, this study revealed that 100% of ulcer cases were infected with iceA1 with a statistically significant correlation (p=0.0001), while 94.6% of gastritis and 90.9% of normal were infected with iceA2 (p=0.0001). Moreover cagA+/iceA1 combined genotypes was statistically correlated with peptic ulcer (100%) but not cagA-/iceA1 (0%; p=0.0001).

CONCLUSION

Certain H. pylori genotypes were more virulent than others. Multiple clinical implications based on these finding might be studied further.

Structure and mechanism of Helicobacter pylori fucosyltransferase. A basis for lipopolysaccharide variation and inhibitor design

Helicobacter pylori alpha1,3-fucosyltransferase (FucT) is involved in catalysis to produce the Lewis x trisaccharide, the major component of the bacteria's lipopolysaccharides, which has been suggested to mimic the surface sugars in gastric epithelium to escape host immune surveillance. We report here three x-ray crystal structures of FucT, including the FucT.GDP-fucose and FucT.GDP complexes. The protein structure is typical of the glycosyltransferase-B family despite little sequence homology. We identified a number of catalytically important residues, including Glu-95, which serves as the general base, and Glu-249, which stabilizes the developing oxonium ion during catalysis. The residues Arg-195, Tyr-246, Glu-249, and Lys-250 serve to interact with the donor substrate, GDP-fucose. Variations in the protein and ligand conformations, as well as a possible FucT dimer, were also observed. We propose a catalytic mechanism and a model of polysaccharide binding not only to explain the observed variations in H. pylori lipopolysaccharides, but also to facilitate the development of potent inhibitors.

Pathogenesis of Helicobacter pylori Infection

SUMMARY

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori .

Pathogenesis of Helicobacter pylori Infection

SUMMARY

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori .

Pathogenesis of Helicobacter pylori Infection

SUMMARY

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori .

Pathogenesis of Helicobacter pylori infection

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori.

Association of antibiotic resistance and higher internalization activity in resistant Helicobacter pylori isolates

OBJECTIVES

Helicobacter pylori resistance to antibiotics is the main factor for therapy failure, while other features remain largely unknown. The aims of this study are to investigate the relationship of antibiotic resistance and in vitro internalization activity between cure and failure isolates and to determine whether failures are associated with persistence of the same predominant strain.

METHODS

Fifty-three isolates from forty-seven patients (cure group, n = 31; failure group, n = 16) receiving one of two lansoprazole-based therapies before and/or after therapy were investigated. Antibiotic susceptibility was determined by Etest. Genotyping was determined by cagA, babA, vacA and RAPD analyses. Target cells of internalization assay were AGS cells.

RESULTS

Five of six paired pre- and post-treatment isolates had the same predominant genetic profiles and exhibited similarly high internalization activities. The A2143G point mutation of the 23S rRNA gene conferred clarithromycin resistance. Moreover, increased antibiotic resistance after therapy was found for these five cases. Pre-treatment isolates from the failure group (n = 11) had higher level of internalization activity than those from the cure group (n = 31) (P = 0.00005). Antibiotic-resistant strains were significantly associated with higher internalization activity than were susceptible strains (metronidazole, P < 0.005; clarithromycin, P < 0.005).

CONCLUSIONS

Our results suggest that resistant H. pylori strains are associated with antibiotic resistance and superior internalization activity, protecting them against antibiotic treatment.

A single aromatic amino acid at the carboxyl terminus of Helicobacter pylori {alpha}1,3/4 fucosyltransferase determines substrate specificity

Fucosyltransferases (FucT) from different Helicobacter pylori strains display distinct Type I (Galbeta1,3GlcNAc) or Type II (Galbeta1,4GlcNAc) substrate specificity. FucT from strain UA948 can transfer fucose to the OH-3 of Type II acceptors as well as to the OH-4 of Type I acceptors on the GlcNAc moiety, so it has both alpha1,3 and alpha1,4 activities. In contrast, FucT from strain NCTC11639 has exclusive alpha1,3 activity. Our domain swapping study (Ma, B., Wang, G., Palcic, M. M., Hazes, B., and Taylor, D. E. (2003) J. Biol. Chem. 278, 21893-21900) demonstrated that exchange of the hypervariable loops, (347)DNPFIFC(353) in 11639FucT and (345)CNDAHYSALH(354) in UA948FucT, were sufficient to either confer or abolish alpha1,4 activity. Here we performed alanine scanning site-directed mutagenesis to identify which amino acids within (345)CNDAHYSALH(354) of UA948FucT confer Type I substrate specificity. The Tyr(350) --> Ala mutation dramatically reduced alpha1,4 activity without lowering alpha1,3 activity. None of the other alanine substitutions selectively eliminated alpha1,4 activity. To elucidate how Tyr(350) determines alpha1,4 specificity, mutants Tyr(350) --> Phe, Tyr(350) --> Trp, and Tyr(350) --> Gly were constructed in UA948FucT. These mutations did not decrease alpha1,3 activity but reduced the alpha1,4 activity to 66.9, 55.6, and 3.1% [corrected] of wild type level, respectively. Apparently the aromatic nature, but not the hydroxyl group of Tyr(350), is essential for alpha1,4 activity. Our data demonstrate that a single amino acid (Tyr(350)) in the C-terminal hypervariable region of UA948FucT determines Type I acceptor specificity. Notably, a single aromatic residue (Trp) has also been implicated in controlling Type I acceptor preference for human FucT III, but it is located in an N-terminal hypervariable stem domain.

Comparative analysis of four Campylobacterales

Comparative genome analysis can be used to identify species-specific genes and gene clusters, and analysis of these genes can give an insight into the mechanisms involved in a specific bacteria-host interaction. Comparative analysis can also provide important information on the genome dynamics and degree of recombination in a particular species. This article describes the comparative genome analysis of representatives of four different Campylobacterales species - two pathogens of humans, Helicobacter pylori and Campylobacter jejuni, as well as Helicobacter hepaticus, which is associated with liver cancer in rodents, and the non-pathogenic commensal species, Wolinella succinogenes.

Synthesis of the Trisaccharide Repeating Unit of the Atypical O-Antigen Polysaccharide from Danish Helicobacter pylori Strains Employing the 2‘-Carboxybenzyl Glycoside

[reaction: see text] Synthesis of the unique trisaccharide repeating unit of the O-polysaccharide of the lipopolysaccharide from Danish Helicobacter pylori strains has been accomplished. Key steps include the coupling of three monosaccharide moieties by glycosylations employing the 2'-carboxybenzyl glycoside method. Also presented is a method for the synthesis of the novel branched sugar, 3-C-methyl-D-mannose, which is one of three monosaccharide components.

Persistent infection with Helicobacter pylori and the development of gastric cancer

Gastric malignancies have been closely linked to infection of the gastric mucosa with Helicobacter pylori, but the individual factors involved in the multistage process of tumor development are still poorly understood. H. pylori evades the host defense system and causes persistent infection and chronic inflammation. Immune activation leads to DNA damage by the release of oxygen and nitrogen radicals. Ongoing tissue repair mechanisms and the secretion of cytokines and growth factors, as well as bacterial effector molecules, cause disturbances in the balance between epithelial cell proliferation and apoptosis, promote the accumulation of potential oncogenic mutations, and support neovascularization and tumor growth. In addition, H. pylori might hamper the development of an efficient antitumor immunity and provoke immune-mediated pathology. This review summarizes the recent progress in the understanding of the intimate bacteria-host relationship and the mechanisms by which H. pylori may promote the process of tumor development.

Efficacy of sulforaphane in eradicating Helicobacter pylori in human gastric xenografts implanted in nude mice

Sulforaphane, an isothiocyanate abundant in the form of its glucosinolate precursor in broccoli sprouts, has shown in vitro activity against Helicobacter pylori. We evaluated the effect of sulforaphane in vivo against this bacterium by using human gastric xenografts in nude mice. H. pylori was completely eradicated in 8 of the 11 sulforaphane-treated grafts. This result suggests that sulforaphane might be beneficial in the treatment of H. pylori-infected individuals.

Helicobacter infection: pathogenesis

PURPOSE OF REVIEW

Helicobacter pylori remains one of the world's most prevalent bacterial pathogens, often causing gastritis, peptic ulcer disease, gastric mucosa-associated lymphatic tissue lymphoma, or gastric adenocarcinoma. Elucidation of H. pylori virulence mechanisms and characteristics of the host that contribute to pathogenesis will facilitate the development of both pharmacologic and immunologic therapies.

RECENT FINDINGS

The functional status of the outer inflammatory protein A may have predictive value for duodenal ulcer, and host alleles for interleukin-1beta, interleukin-1R, tumor necrosis factor-alpha, and interleukin-10 correlate with increased risk for gastric cancer. H. pylori vacuolating cytotoxin A and cytotoxin-associated gene A protein interact with multiple host proteins, although downstream signaling events need further characterization. It does appear however, that CagA may participate in a negative feedback loop on Src family kinases to prevent further phosphorylation of CagA. Several models, including delayed type hypersensitivity in immune mice, and spontaneous clearance of H. pylori from interleukin-10 and phagocyte oxidase mice, provide evidence that severe inflammation may be sufficient to eradicate H. pylori. The strategies used by H. pylori to avoid the inflammatory response are also becoming clearer. H. pylori remains viable when internalized by epithelial cells, and it remains viable in macrophage phagosomes by inhibiting phagosome maturation. Additionally, H. pylori may regulate the host immune response through activation of dendritic cells and CD25 regulatory T cells, and it may direct immunosuppression of T cells.

SUMMARY

Helicobacter pylori virulence is accomplished through many mechanisms, including vacuolating cytotoxin A and CagA activities, and may be predicted based on bacterial and host genotypes. Ultimately, H. pylori persistence may depend on its success in downregulating the inflammatory response.

Breaking the species barrier: use of SCID mouse-human chimeras for the study of human infectious diseases

Mouse-human chimeras have become a novel way to model the interactions between microbial pathogens and human cells, tissues or organs. Diseases studied with human xenografts in severe combined immunodeficient (SCID) mice include Pseudomonas aeruginosa infection in cystic fibrosis, group A streptococci and impetigo, bacillary and amoebic dysentery, and AIDS. In many cases, disease in the human xenograft appears to accurately reproduce the disease in humans, providing a powerful model for identifying virulence factors, host responses to infection and the effects of specific interventions on disease. In this review, we summarize recent studies that have used mouse-human chimeras to understand the pathophysiology of specific bacterial and protozoan infections.

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.