Specific identification of three low molecular weight membrane-associated antigens of Helicobacter pylori

Identification of anti-Helicobacter pylori antibody signatures in gastric intestinal metaplasia

BACKGROUND

Chronic Helicobacter pylori infection may induce gastric intestinal metaplasia (IM). We compared anti-H. pylori antibody profiles between IM cases and non-atrophic gastritis (NAG) controls.

METHODS

We evaluated humoral responses to 1528 H. pylori proteins among a discovery set of 50 IM and 50 NAG using H. pylori protein arrays. Antibodies with ≥ 20% sensitivity at 90% specificity for either group were selected and further validated in an independent set of 100 IM and 100 NAG using odds ratios (OR). A validated multi-signature was evaluated using the area under the receiver operating characteristics curve (AUC) and net reclassification improvement (NRI).

RESULTS

Sixty-two immunoglobulin (Ig) G and 11 IgA antibodies were detected in > 10%. Among them, 22 IgG and 6 IgA antibodies were different between IM and NAG in the discovery set. Validated antibodies included 11 IgG (anti-HP1177/Omp27/HopQ [OR = 8.1, p < 0.001], anti-HP0547/CagA [4.6, p < 0.001], anti-HP0596/Tipα [4.0, p = 0.002], anti-HP0103/TlpB [3.8, p = 0.001], anti-HP1125/PalA/Omp18 [3.1, p = 0.001], anti-HP0153/RecA [0.48, p = 0.03], anti-HP0385 [0.41, p = 0.006], anti-HP0243/TlpB [0.39, p = 0.016], anti-HP0371/FabE [0.37, p = 0.017], anti-HP0900/HypB/AccB [0.35, p = 0.048], and anti-HP0709 [0.30, p = 0.003]), and 2 IgA (anti-HP1125/PalA/Omp18 [2.7, p = 0.03] and anti-HP0596/Tipα [2.5, p = 0.027]). A model including all 11 IgG antibodies (AUC = 0.81) had better discriminated IM and NAG compared with an anti-CagA only (AUC = 0.77) model (NRI = 0.44; p = 0.001).

CONCLUSIONS

Our study represents the most comprehensive assessment of anti-H. pylori antibody profiles in IM. The target antigens for these novel antibodies may act together with CagA in the progression to IM. Along with other biomarkers, specific H. pylori antibodies may identify IM patients, who would benefit from surveillance.

How bacteria utilize sialic acid during interactions with the host: snip, snatch, dispatch, match and attach

N -glycolylneuraminic acid (Neu5Gc), and its precursor N-acetylneuraminic acid (Neu5Ac), commonly referred to as sialic acids, are two of the most common glycans found in mammals. Humans carry a mutation in the enzyme that converts Neu5Ac into Neu5Gc, and as such, expression of Neu5Ac can be thought of as a 'human specific' trait. Bacteria can utilize sialic acids as a carbon and energy source and have evolved multiple ways to take up sialic acids. In order to generate free sialic acid, many bacteria produce sialidases that cleave sialic acid residues from complex glycan structures. In addition, sialidases allow escape from innate immune mechanisms, and can synergize with other virulence factors such as toxins. Human-adapted pathogens have evolved a preference for Neu5Ac, with many bacterial adhesins, and major classes of toxin, specifically recognizing Neu5Ac containing glycans as receptors. The preference of human-adapted pathogens for Neu5Ac also occurs during biosynthesis of surface structures such as lipo-oligosaccharide (LOS), lipo-polysaccharide (LPS) and polysaccharide capsules, subverting the human host immune system by mimicking the host. This review aims to provide an update on the advances made in understanding the role of sialic acid in bacteria-host interactions made in the last 5-10 years, and put these findings into context by highlighting key historical discoveries. We provide a particular focus on 'molecular mimicry' and incorporation of sialic acid onto the bacterial outer-surface, and the role of sialic acid as a receptor for bacterial adhesins and toxins.

The lipoprotein HP1454 of Helicobacter pylori regulates T-cell response by shaping T-cell receptor signalling

Helicobacter pylori (HP) is a Gram-negative bacterium that chronically infects the stomach of more than 50% of human population and represents a major cause of gastric cancer, gastric lymphoma, gastric autoimmunity, and peptic ulcer. It still remains to be elucidated, which HP virulence factors are important in the development of gastric disorders. Here, we analysed the role of the HP protein HP1454 in the host-pathogen interaction. We found that a significant proportion of T cells isolated from HP patients with chronic gastritis and gastric adenocarcinoma proliferated in response to HP1454. Moreover, we demonstrated in vivo that HP1454 protein drives Th1/Th17 inflammatory responses. We further analysed the in vitro response of human T cells exposed either to an HP wild-type strain or to a strain with a deletion of the hp1454 gene, and we revealed that HP1454 triggers the T-cell antigen receptor-dependent signalling and lymphocyte proliferation, as well as the CXCL12-dependent cell adhesion and migration. Our study findings prove that HP1454 is a crucial bacterial factor that exerts its proinflammatory activity by directly modulating the T-cell response. The relevance of these results can be appreciated by considering that compelling evidence suggest that chronic gastric inflammation, a condition that paves the way to HP-associated diseases, is dependent on T cells.

Helicobacter pylori Outer Membrane Protein 18 (Hp1125) Is Involved in Persistent Colonization by Evading Interferon- γ Signaling

Outer membrane proteins (OMPs) can induce an immune response. Omp18 (HP1125) of H. pylori is a powerful antigen that can induce significant interferon-γ (IFN-γ) levels. Previous studies have suggested that IFN-γ plays an important role in H. pylori clearance. However, H. pylori has multiple mechanisms to avoid host immune surveillance for persistent colonization. We generated an omp18 mutant (H. pylori 26695 and H. pylori SS1) strain to examine whether Omp18 interacts with IFN-γ and is involved in H. pylori colonization. qRT-PCR revealed that IFN-γ induced Omp18 expression. qRT-PCR and western blot analysis revealed reduced expressions of virulence factors CagA and NapA in H. pylori 26695 with IFN-γ treatment, but they were induced in the Δomp18 strain. In C57BL/6 mice infected with H. pylori SS1 and the Δomp18 strain, the Δomp18 strain conferred defective colonization and activated a stronger inflammatory response. Signal transducer phosphorylation and transcription 1 (STAT1) activator was downregulated by the wild-type strain but not the Δomp18 strain in IFN-γ-treated macrophages. Furthermore, Δomp18 strain survival rates were poor in macrophages compared to the wild-type strain. We concluded that H. pylori Omp18 has an important function influencing IFN-γ-mediated immune response to participate in persistent colonization.

Antigenic proteins of Helicobacter pylori of potential diagnostic value

Helicobacter pylori antigen was prepared from an isolate from a patient with a duodenal ulcer. Serum samples were obtained from culture-positive H. pylori infected patients with duodenal ulcers, gastric ulcers and gastritis (n=30). As controls, three kinds of sera without detectable H. pylori IgG antibodies were used: 30 from healthy individuals without history of gastric disorders, 30 from patients who were seen in the endoscopy clinic but were H. pylori culture negative and 30 from people with other diseases. OFF-GEL electrophoresis, SDS-PAGE and Western blots of individual serum samples were used to identify protein bands with good sensitivity and specificity when probed with the above sera and HRP-conjugated anti-human IgG. Four H. pylori protein bands showed good (≥ 70%) sensitivity and high specificity (98-100%) towards anti-Helicobacter IgG antibody in culture- positive patients sera and control sera, respectively. The identities of the antigenic proteins were elucidated by mass spectrometry. The relative molecular weights and the identities of the proteins, based on MALDI TOF/ TOF, were as follows: CagI (25 kDa), urease G accessory protein (25 kDa), UreB (63 kDa) and proline/pyrroline- 5-carboxylate dehydrogenase (118 KDa). These identified proteins, singly and/or in combinations, may be useful for diagnosis of H. pylori infection in patients.

Proteomic biomarkers associated with Streptococcus agalactiae invasive genogroups

Group B streptococcus (GBS, Streptococcus agalactiae) is a leading cause of meningitis and sepsis in newborns and an etiological agent of meningitis, endocarditis, osteoarticular and soft tissue infections in adults. GBS isolates are routinely clustered in serotypes and in genotypes. At present one GBS sequence type (i.e. ST17) is considered to be closely associated with bacterial invasiveness and novel proteomic biomarkers could make a valuable contribution to currently available GBS typing data. For that purpose we analyzed the protein profiles of 170 genotyped GBS isolates by Surface-Enhanced Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (SELDI). Univariate statistical analysis of the SELDI profiles identified four protein biomarkers significantly discriminating ST17 isolates from those of the other sequence types. Two of these biomarkers (MW of 7878 Da and 12200 Da) were overexpressed and the other two (MW of 6258 Da and 10463 Da) were underexpressed in ST17. The four proteins were isolated by mass spectrometry-assisted purification and their tryptic peptides analyzed by LC-MS/MS. They were thereby identified as the small subunit of exodeoxyribonuclease VII, the 50S ribosomal protein L7/L12, a CsbD-like protein and thioredoxin, respectively. In conclusion, we identified four candidate biomarkers of ST17 by SELDI for high-throughput screening. These markers may serve as a basis for further studies on the pathophysiology of GBS infection, and for the development of novel vaccines.

Crystal structure of TNF-α-inducing protein from Helicobacter pylori in active form reveals the intrinsic molecular flexibility for unique DNA-binding

Tipα (TNF-α-inducing protein) from Helicobacter pylori is a carcinogenic effector. Studies on this protein revealed that a homodimer linked by a pair of intermolecular disulfide bridges (Cys25-Cys25 and Cys27-Cys27) was absolutely necessary for its biological functions. The activities of Tipα would be abolished when both disulfide bridges were disrupted. The crystal structures of Tipα reported to date, however, were based on inactive, monomeric mutants with their N-terminal, including residues Cys25 and Cys27, truncated. Here we report the crystal structure of H. pylori Tipα protein, TipαN²⁵, at 2.2Å resolution, in which Cys25 and Cys27 form a pair of inter-chain disulfide bridges linking an active dimer. The disulfide bridges exhibit structural flexibility in the present structure. A series of structure-based mutagenesis, biochemical assays and molecular dynamic simulations on DNA-Tipα interactions reveal that Tipα utilizes the dimeric interface as the DNA-binding site and that residues His60, Arg77 and Arg81 located at the interface are crucial for DNA binding. Tipα could bind to one ssDNA, two ssDNA or one dsDNA in experiments, respectively, in the native or mutant states. The unique DNA-binding activities of Tipα indicate that the intrinsic flexible nature of disulfide bridges could endow certain elasticity to the Tipα dimer for its unique bioactivities. The results shed light on the possible structural mechanism for the functional performances of Tipα.

Immunoreactive proteins of Campylobacter concisus, an emergent intestinal pathogen

Campylobacter concisus is an emerging pathogen of the human gastrointestinal tract. Recently, a significantly higher prevalence of C. concisus DNA and higher levels of antibodies specific to C. concisus was detected in children with Crohn's disease when compared with controls. The aim of this study was to identify C. concisus immunoreactive antigens. Proteins from C. concisus were separated using two-dimensional gel electrophoresis, and sera from 10 C. concisus-positive children with Crohn's disease were employed for immunoprobing. The patients' sera reacted with 69 spots, which corresponded to 31 proteins identified by mass spectrometry. The proteins were functionally classified as involved in chemotaxis, signal transduction, flagellar motility, surface binding and membrane protein assembly. Although the individual patients' sera reacted to different sets of proteins, common antigens that were recognized by all patients were flagellin B, ATP synthase F1 alpha subunit, and outer membrane protein 18. Cross-reactivity between proteins of the Campylobacter genus was tested using patients' sera absorbed with Campylobacter showae, Campylobacter jejuni and Campylobacter ureolyticus. Most of the C. concisus immunoreactive proteins identified in this study showed cross-reactivity with other species except for three antigens. In conclusion, this study has identified C. concisus proteins that are immunoreactive within patients with Crohn's disease.

Identification of S-nitrosylation of proteins of Helicobacter pylori in response to nitric oxide stress

Innate and adaptive immune responses are activated in humans when Helicobacter pylori invades the gastric mucosa. Nitric oxide (NO) and reactive nitrogen species are important immune effectors, which can exert their functions through oxidation and S-nitrosylation of proteins. S-nitrosoglutathione and sodium nitroprus-side were used as NO donors and H. pylori cells were incubated with these compounds to analyze the inhibitory effect of NO. The suppressing effect of NO on H. pylori has been shown in vitro. Furthermore, the proteins modified by S-nitrosylation in H. pylori were identified through the biotin switch method in association with matrix-assisted laser desorption ionization/time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS). Five S-nitrosylated proteins identified were a chaperone and heat-shock protein (GroEL), alkyl hydroperoxide reductase (TsaA), urease alpha subunit (UreA), HP0721, and HP0129. Importantly, S-nitrosylation of TsaA and UreA were confirmed using purified recombinant proteins. Considering the importance of these enzymes in antioxidant defenses, adherence, and colonization, NO may exert its antibacterial actions by targeting enzymes through S-nitrosylation. Identification of protein S-nitrosylation may contribute to an understanding of the antibacterial actions of NO. Our findings provide an insight into potential targets for the development of novel therapeutic agents against H. pylori infection.

Identification of surface proteins in Enterococcus faecalis V583

BACKGROUND

Surface proteins are a key to a deeper understanding of the behaviour of Gram-positive bacteria interacting with the human gastro-intestinal tract. Such proteins contribute to cell wall synthesis and maintenance and are important for interactions between the bacterial cell and the human host. Since they are exposed and may play roles in pathogenicity, surface proteins are interesting targets for drug design.

RESULTS

Using methods based on proteolytic "shaving" of bacterial cells and subsequent mass spectrometry-based protein identification, we have identified surface-located proteins in Enterococcus faecalis V583. In total 69 unique proteins were identified, few of which have been identified and characterized previously. 33 of these proteins are predicted to be cytoplasmic, whereas the other 36 are predicted to have surface locations (31) or to be secreted (5). Lipid-anchored proteins were the most dominant among the identified surface proteins. The seemingly most abundant surface proteins included a membrane protein with a potentially shedded extracellular sulfatase domain that could act on the sulfate groups in mucin and a lipid-anchored fumarate reductase that could contribute to generation of reactive oxygen species.

CONCLUSIONS

The present proteome analysis gives an experimental impression of the protein landscape on the cell surface of the pathogenic bacterium E. faecalis. The 36 identified secreted (5) and surface (31) proteins included several proteins involved in cell wall synthesis, pheromone-regulated processes, and transport of solutes, as well as proteins with unknown function. These proteins stand out as interesting targets for further investigation of the interaction between E. faecalis and its environment.

Complexomics study of two Helicobacter pylori strains of two pathological origins: potential targets for vaccine development and new insight in bacteria metabolism

Helicobacter pylori infection plays a causal role in the development of gastric mucosa-associated lymphoid tissue (MALT) lymphoma (LG-MALT) and duodenal ulcer (DU). Although many virulence factors have been associated with DU, many questions remain unanswered regarding the evolution of the infection toward this exceptional event, LG-MALT. The present study describes and compares the complexome of two H. pylori strains, strain J99 associated with DU and strain B38 associated with LG-MALT, using the two-dimensional blue native/SDS-PAGE method. It was possible to identify 90 different complexes (49 and 41 in the B38 and J99 strains, respectively); 12 of these complexes were common to both strains (seven and five in the membrane and cytoplasm, respectively), reflecting the variability of H. pylori strains. The 44 membrane complexes included numerous outer membrane proteins, such as the major adhesins BabA and SabA retrieved from a complex in the B38 strain, and also proteins from the hor family rarely studied. BabA and BabB adhesins were found to interact independently with HopM/N in the B38 and J99 strains, respectively. The 46 cytosolic complexes essentially comprised proteins involved in H. pylori physiology. Some orphan proteins were retrieved from heterooligomeric complexes, and a function could be proposed for a number of them via the identification of their partners, such as JHP0119, which may be involved in the flagellar function. Overall, this study gave new insights into the membrane and cytoplasm structure, and those which could help in the design of molecules for vaccine and/or antimicrobial agent development are highlighted.

Helicobacter pylori Omp18 and its application in serologic screening of infection

Helicobacter pylori (Hp) is a major risk factor for gastrointestinal disorders including gastric cancer. We evaluated host serum antibody responses toward outer membrane protein18 in comparison with Urease A and B subunits. omp18 and ureA-ureB gene fragments were PCR amplified, cloned, and expressed in E. coli expression system. The expressed proteins were visualized on SDS-PAGE and confirmed by immuno-blotting. Purified proteins were applied in western blotting assays in comparison with local and foreign ELISA kits. ROC curve analysis identified the optimum cut-off points for each protein. rOmp18 represented the highest rates of sensitivity (94%), specificity (89%), PPV (97.4%), NPV (77.4%), and accuracy (93.2%) in comparison with urease A and B subunits. These immunologic indices were in "substantial" agreement (Κ = 0.7) with the gold standard tests for Hp detection. This study recommends Hp conserved Omp18 as a reliable serologic marker for accurate detection of Hp infection particularly for application in population screening approaches.

The role of heparan sulfate on adhesion of 47 and 51 kDa outer membrane proteins ofHelicobacter pylorito gastric cancer cellsThis study was done in memory of the late Dr. Roberto Carlos Vazquez-Juarez

Helicobacter pylori is a common gastrointestinal pathogenic bacterium in humans and the usual preference for the stomach’s outer membrane proteins (OMPs) are antigens involved in the adhesion process. Through SDS–PAGE and blotting analyses, using horseradish peroxidase-labeled heparan sulfate (HRP-HS) as a probe, we identified H. pylori OMPs with affinity for heparan sulfate (OMP-HS). Biotin–streptavidin bacterial-adhesion assay was used to evaluate participation of OMP-HS in the adhesion of H. pylori to semi-confluent HeLa S3 and Kato III cell monolayers. The results provide evidence that induction of antibodies against 2 OMP-HSs (HSBP-47 and HSBP-51) could reduce binding of H. pylori to both cell lines and induce detachment of cell-bound bacteria from infected cultured cells.

Candidate antigens for Q fever serodiagnosis revealed by immunoscreening of a Coxiella burnetii protein microarray

Q fever is a widespread zoonosis caused by Coxiella burnetii. Diagnosis of Q fever is usually based on serological testing of patient serum. The diagnostic antigen of test kits is formalin-fixed phase I and phase II organisms of the Nine Mile reference strain. Deficiencies of this antigen include (i) potential for cross-reactivity with other pathogens; (ii) an inability to distinguish between C. burnetii strains; and (iii) a need to propagate and purify C. burnetii, a difficult and potentially hazardous process. Consequently, there is a need for sensitive and specific serodiagnostic tests utilizing defined antigens, such as recombinant C. burnetii protein(s). Here we describe the use of a C. burnetii protein microarray to comprehensively identify immunodominant antigens recognized by antibody in the context of human C. burnetii infection or vaccination. Transcriptionally active PCR products corresponding to 1,988 C. burnetii open reading frames (ORFs) were generated. Full-length proteins were successfully synthesized from 75% of the ORFs by using an Escherichia coli-based in vitro transcription and translation system (IVTT). Nitrocellulose microarrays were spotted with crude IVTT lysates and probed with sera from acute Q fever patients and individuals vaccinated with Q-Vax. Immune sera strongly reacted with approximately 50 C. burnetii proteins, including previously identified immunogens, an ankyrin repeat-domain containing protein, and multiple hypothetical proteins. Recombinant protein corresponding to selected array-reactive antigens was generated, and the immunoreactivity was confirmed by enzyme-linked immunosorbent assay. This sensitive and high-throughput method for identifying immunoreactive C. burnetii proteins will aid in the development of Q fever serodiagnostic tests based on recombinant antigen.

HpaA is essential for Helicobacter pylori colonization in mice

Infection with the human gastric pathogen Helicobacter pylori can give rise to chronic gastritis, peptic ulcer, and gastric cancer. All H. pylori strains express the surface-localized protein HpaA, a promising candidate for a vaccine against H. pylori infection. To study the physiological importance of HpaA, a mutation of the hpaA gene was introduced into a mouse-adapted H. pylori strain. To justify that the interruption of the hpaA gene did not cause any polar effects of downstream genes or was associated with a second site mutation, the protein expression patterns of the mutant and wild-type strains were characterized by two different proteomic approaches. Two-dimensional differential in-gel electrophoresis analysis of whole-cell extracts and subcellular fractionation combined with nano-liquid chromatography-Fourier transform ion cyclotron resonance mass spectrometry for outer membrane protein profiling revealed only minor differences in the protein profile between the mutant and the wild-type strains. Therefore, the mutant strain was tested for its colonizing ability in a well-established mouse model. While inoculation with the wild-type strain resulted in heavily H. pylori-infected mice, the HpaA mutant strain was not able to establish colonization. Thus, by combining proteomic analysis and in vivo studies, we conclude that HpaA is essential for the colonization of H. pylori in mice.

Western blotting of total lysate of Helicobacter pylori in cases of atrophic body gastritis

BACKGROUND

Atrophic body gastritis is considered the first important step in the histogenesis of gastric carcinoma, a multistep process starting from chronic gastritis and progressing through chronic atrophic gastritis, intestinal metaplasia, and dysplasia. Helicobacter pylori is involved in the induction of atrophic body gastritis, but documentation of H. pylori infection is difficult because of the progressive disappearance of the bacterium. Our study aimed to detect past H. pylori infection in patients with atrophic body gastritis.

METHODS

We used Western blot analyses of whole bacterial protein lysate of 2 different strains to probe sera from 143 patients. All sera were analyzed by ELISA (Bio-Rad), and results of gastric histology were available for all patients.

RESULTS

Among 111 patient sera previously classified as negative for H. pylori infection by ELISA, 106 (95.5%) were positive when assayed by immunoblotting.

CONCLUSIONS

Commercial diagnostic reagent sets may fail to detect H. pylori infection. Western blotting of whole bacterial protein extracts could provide the basis of a noninvasive serology tool able to assess previous infection with H. pylori in patients with atrophic body gastritis.

Approaches for the identification of potential excreted/secreted proteins of Leishmania major parasites

Leishmania parasites are able to survive in host macrophages despite the harsh phagolysosomal vacuoles conditions. This could reflect, in part, their capacity to secrete proteins that may play an essential role in the establishment of infection and serve as targets for cellular immune responses. To characterize Leishmania major proteins excreted/secreted early after promastigote entry into the host macrophage, we have generated antibodies against culture supernatants of stationary-phase promastigotes collected 6 h after incubation in conditions that partially reproduce those prevailing in the parasitophorous vacuole. The screening of an L. major cDNA library with these antibodies led us to isolate 33 different cDNA clones that we report here. Sequence analysis revealed that the corresponding proteins could be classified in 3 groups: 9 proteins have been previously described as excreted/secreted in Leishmania and/or other species; 11 correspond to known proteins already characterized in Leishmania and/or other species although it is unknown whether they are excreted/secreted and 13 code for unknown proteins. Interestingly, the latter are transcribed as shown by RT-PCR and some of them are stage regulated. The L. major excreted/secreted proteins may constitute putative virulence factors, vaccine candidates and/or new drug targets.

Helicobacter pylori outer membrane protein 18 (Hp1125) induces dendritic cell maturation and function

BACKGROUND

Dendritic cells (DCs) are potent antigen-presenting cells that initiate T-cell responses. A robust adaptive Th1 immune response is crucial to an adaptive (Th2) immune response necessary for vaccine-induced protective immunity against Helicobacter pylori. It has been shown that several outer membrane proteins (Omps) induce a robust antibody response. However, it is also known that the antibodies generated are not protective. Moreover there is great variation in the recognition of high molecular weight H. pylori proteins by sera from infected patients. In contrast to the high molecular weight proteins, serologic responses to small molecular weight proteins provide assessment of current infection with H. pylori and also of its eradication.

AIM

The goal of the study was to analyze the activation of the immune response by a specific low molecular weight Omp that is universally expressed by all H. pylori strains. Therefore, we studied interaction of H. pylori Omp18 with DCs.

METHODS

Activation of murine bone marrow-derived DCs and production of cytokines by Omp18 was assessed by fluorescence-activated cell sorter (FACS) for costimulatory markers and ELISA, respectively. The ability of Omp18 stimulated DCs to induce lymphocyte proliferation was measured in a mixed leukocyte reaction.

RESULTS

Omp18 induced higher expression of the B7 (CD80 and CD86) costimulatory molecule after 18 hours indicating processing and presentation of the antigen on the surface by bone marrow-derived DCs. The maturing DCs also secreted significant levels of IL-12, but was 4-fold less than that stimulated by whole bacteria. Omp18-primed DCs induced proliferation and release of IFNgamma by syngeneic splenocytes.

CONCLUSION

We concluded that Omp18 is capable of activating DCs initiating a Th1 immune response.

The best method of detecting prior Helicobacter pylori infection

AIM

Prior Helicobacter pylori (H pylori) infection has often been underestimated. These underestimations have misled physicians attempting to determine the significance between H pylori and certain gastrointestinal lesions such as intestinal metaplasia, atrophic gastritis, and gastric cancer. Our study endeavored to detect past H pylori infections accurately, easily, and rapidly with the newly developed immunoblot kit, Helico Blot 2.1.

METHODS

Thirty-three patients, including 25 H pylori infected and 8 uninfected cases, were enrolled in our study. All patients received consecutive gastroendoscopic examinations and (13)C-urea breath test (UBT) tests at 6- or 12-mo intervals for up to 4 years. Serum samples were obtained from each patient at the same time. Intragastric H pylori infection was confirmed in accordance with the gold standard. Twenty-five H pylori-infected patients received triple therapies after initial bacterial confirmation, and were successful in eradicating their infections. Serially obtained sera were tested by means of Helico Blot 2.1.

RESULTS

Current infection marker detected by Helico Blot 2.1 was unreliable for representing ongoing H pylori infection. Only 35 and 37 ku antibodies of H pylori had significant seroconversion rates 1 year after having been cured. The seropositive rates of 116 ku (cytotoxin-associated antigen (CagA)) and Helico Blot 2.1 were nearly 100% during 4-year follow-up period. Both CagA antigen and Helico blot 2.1 could serve as indicators of long-term H pylori infection.

CONCLUSION

Helico Blot 2.1 can detect past H pylori infections for up to 4 years, and is the best method to date for detecting previous long-term H pylori infection.

Identification of a new sialic acid-binding protein in Helicobacter pylori

A novel sialic acid-specific lectin has been isolated from Helicobacter pylori lysate using fetuin-agarose affinity chromatography followed by cleavage of the alpha(2,3) and alpha(2,6) linkages of sialic acids using neuraminidase. The protein had a molecular weight of 17.5 kDa on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and was identified by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry to be protein of unknown function with gene number HP0721. Recombinant HP0721 was shown to bind to fetuin-agarose and sialic acid-containing glycosphingolipids on thin-layer plates suggesting this protein may represent another sialic acid-specific adhesin of H. pylori. A H. pylori mutant defective for HP0721 was generated and its ability to bind to human AGS cells assayed.

Human immune response towards recombinant Helicobacter pylori urease and cellular fractions

Vaccination against Helicobacter pylori is of particular clinical interest. Recombinant urease, the major protein in H. pylori, has been used for mucosal vaccination trials in different animal models, but was found to be ineffective in humans. The current study therefore investigated the human immune response towards recombinant H. pylori urease A and B (rUreA/B) expressed in E. coli compared to different cellular fractions of H. pylori (cytosol, total, inner and outer membrane). Monocyte-derived dendritic cells (Mo-DC) were generated from monocytes isolated by magnetic antigen cell separation (MACS) from healthy volunteers and cultured in the presence of hrIL-4 and hrGM-CSF. Mo-DC were stimulated for 48h with the recombinant proteins (1 microg/ml) or cellular fractions (1-10 microg/ml) and cytokine release was determined in the culture supernatant by ELISA. rUreA and rUreB were effective in inducing IL-12 secretion (6-10 fold) and, to a much lesser extent (2 fold), IL-10 secretion from Mo-DC. Total and outer membrane preparations from H. pylori stimulated IL-12 secretion significantly, and were even more potent than intact bacteria. Mo-DCs pulsed with rUreA activated allogenic CD56+ NK-cells, as determined by TNF-alpha and IFN-gamma secretion, but not allogenic CD4+/CD45RA+ naïve T-cells. In contrast, Mo-DCs pulsed with H. pylori total membrane or outer membrane preparations activated allogenic naive T-cells in co-culture systems, as determined by increased TNF-alpha secretion. It appears that outer membrane preparations of H. pylori, but not recombinant urease are more effective in inducing a Th1 polarized response in humans in vitro.

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

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

Antigenic properties of HpaA and Omp18, two outer membrane proteins of Helicobacter pylori

Outer membrane proteins (OMPs) are incorporated into the outer plasma membrane of Helicobacter pylori and are important for, e.g., ion transport, adherence, structural and osmotic stability, and bacterial virulence but may also be antigenic due to their surface exposure. Previous proteome-based approaches with H. pylori lysates determined a strong serological reaction towards two H. pylori OMPs, HpaA (TIGR HP0797) and Omp18 (TIGR HP1125). PCR was used to detect DNA encoding the two proteins, and a positive signal was found in all H. pylori strains tested. Proteins were cloned and expressed in the human kidney cell line HK293 with the QiaExpressionist system with a C-terminal His tag. Only sera from infected persons showed a positive reaction with the recombinant proteins. Recombinant HpaA (rHpaA) and rOmp18 were incubated with human peripheral blood mononuclear cells and induced secretion of interleukin-12 (IL-12) and IL-10 from these cells. To determine the effect on antigen-presenting cells, human blood monocytic and dendritic cells (DCs) were isolated by magnetic cell separation. rOmp18 and rHpaA strongly stimulated major histocompatibility class II and CD83 expression 7- to 10-fold on isolated DCs. rHpaA and rOmp18 failed to stimulate IL-8 secretion from monocytes but increased secretion of IL-12 and IL-10 from DCs significantly. In summary, HpaA and Omp18 are recognized by human dendritic cells and induce their maturation as well as antigen presentation. HpaA and Omp18 of H. pylori thereby appear to have a specific antigenic potential in humans.

Current trends in the treatment of upper gastrointestinal disease

The past 25 years have seen an amazing improvement in the treatment and understanding of acid-related disorders. In particular, the introduction of selective histamine receptor antagonists and proton pump inhibitors has made the medical control of acid secretion an effective means of therapy. The demonstration that infection with Helicobacter pylori is responsible for most cases of peptic ulcer disease resulted in another major improvement in therapy in these areas as a result of the eradication of the organism. Research continues in an attempt to find improved means of acid control and better methods for the eradication of H. pylori based on unique proteins expressed by the organism to resist gastric acidity.