Multiparameter selection of Helicobacter pylori antigens identifies two novel antigens with high protective efficacy

Immune evaluation of a Saccharomyces cerevisiae-based oral vaccine against Helicobacter pylori in mice

BACKGROUND

Helicobacter pylori (H. pylori) is a common human pathogenic bacterium that is associated with gastric diseases. The current leading clinical therapy is combination antibiotics, but this treatment has safety issues, especially the induction of drug resistance. Therefore, developing a safe and effective vaccine against H. pylori is one of the best alternatives.

OBJECTIVE

To develop Saccharomyces cerevisiae (S. cerevisiae)-based oral vaccines and then demonstrate the feasibility of this platform for preventing H. pylori infection in the absence of a mucosal adjuvant.

MATERIALS AND METHODS

Saccharomyces cerevisiae (S. cerevisiae)-based oral vaccines, including EBY100/pYD1-UreB and EBY100/pYD1-VacA, were generated and analyzed by Western blot, Immunofluorescence analysis, flow cytometric assay, and indirect enzyme-link immunosorbent assay (ELISA). Further, antibody responses induced by oral administration of EBY100/pYD1-UreB, EBY100/pYD1-VacA, or EBY100/pYD1-UreB + EBY100/pYD1-VacA were measured in a mouse model. Lastly, the vaccinated mice were infected with H. pylori SS1, and colonization in the stomach were evaluated.

RESULTS

Saccharomyces cerevisiae-based H. pylori oral vaccines were successfully constructed. Mice orally administered with EBY100/pYD1-UreB, EBY100/pYD1-VacA, or EBY100/pYD1-UreB + EBY100/pYD1-VacA exhibited a significant humoral immune response as well as a mucosal immune response. Importantly, S. cerevisiae-based oral vaccines could effectively reduce bacterial loads with statistical significance after H. pylori infection.

CONCLUSIONS

Our study shows that S. cerevisiae-based platforms can serve as an alternative approach for the future development of promising bacterial oral vaccine candidates.

Disulfide bond formation in prokaryotes

Interest in protein disulfide bond formation has recently increased because of the prominent role of disulfide bonds in bacterial virulence and survival. The first discovered pathway that introduces disulfide bonds into cell envelope proteins consists of Escherichia coli enzymes DsbA and DsbB. Since its discovery, variations on the DsbAB pathway have been found in bacteria and archaea, probably reflecting specific requirements for survival in their ecological niches. One variation found amongst Actinobacteria and Cyanobacteria is the replacement of DsbB by a homologue of human vitamin K epoxide reductase. Many Gram-positive bacteria express enzymes involved in disulfide bond formation that are similar, but non-homologous, to DsbAB. While bacterial pathways promote disulfide bond formation in the bacterial cell envelope, some archaeal extremophiles express proteins with disulfide bonds both in the cytoplasm and in the extra-cytoplasmic space, possibly to stabilize proteins in the face of extreme conditions, such as growth at high temperatures. Here, we summarize the diversity of disulfide-bond-catalysing systems across prokaryotic lineages, discuss examples for understanding the biological basis of such systems, and present perspectives on how such systems are enabling advances in biomedical engineering and drug development.

Growth phase-dependent composition of the Helicobacter pylori exoproteome

Helicobacter pylori colonizes the human stomach and is associated with an increased risk of gastric cancer and peptic ulcer disease. Analysis of H. pylori protein secretion is complicated by the occurrence of bacterial autolysis. In this study, we analyzed the exoproteome of H. pylori at multiple phases of bacterial growth and identified 74 proteins that are selectively released into the extracellular space. These include proteins known to cause alterations in host cells, antigenic proteins, and additional proteins that have not yet been studied in any detail. The composition of the H. pylori exoproteome is dependent on the phase of bacterial growth. For example, the proportional abundance of the vacuolating toxin VacA in culture supernatant is higher during late growth phases than early growth phases, whereas the proportional abundance of many other proteins is higher during early growth phases. We detected marked variation in the subcellular localization of putative secreted proteins within soluble and membrane fractions derived from intact bacteria. By providing a comprehensive view of the H. pylori exoproteome, these results provide new insights into the array of secreted H. pylori proteins that may cause alterations in the gastric environment.

Oral immunization with recombinant Lactobacillus acidophilus expressing the adhesin Hp0410 of Helicobacter pylori induces mucosal and systemic immune responses

Helicobacter pylori infection is relatively common worldwide and is closely related to gastric mucosa-associated lymphoid tissue (MALT) lymphoma, chronic gastritis, and stomach ulcers. Therefore, a safe and effective method for preventing H. pylori infection is urgently needed. Given that developing an effective vaccine against H. pylori is one of the best alternatives, H. pylori adhesin Hp0410 was expressed in the food-grade bacterium Lactobacillus acidophilus. The recombinant live bacterial vaccine was then used to orally vaccinate mice, and the immunoprotective effects of Hp0410-producing strains were investigated. H. pylori colonization in the stomach of mice immunized with the recombinant L. acidophilus was significantly reduced, in comparison with that in control groups. Furthermore, mucosal secretory IgA antibodies were elicited in the mucosal tissue of mice immunized with the recombinant bacteria, and specific anti-Hp0410 IgG responses were also detected in mouse serum. There was a significant increase in the level of protection against gastric Helicobacter infection following a challenge with H. pylori Sydney strain 1 (SS1). Our results collectively indicate that adhesin Hp0410 is a promising candidate vaccine antigen, and recombinant L. acidophilus expressing Hp0410 is likely to constitute an effective, low-cost, live bacterial vaccine against H. pylori.

A novel insight into the oxidoreductase activity of Helicobacter pylori HP0231 protein

Background

The formation of a disulfide bond between two cysteine residues stabilizes protein structure. Although we now have a good understanding of the Escherichia coli disulfide formation system, the machineries at work in other bacteria, including pathogens, are poorly characterized. Thus, the objective of this work was to improve our understanding of the disulfide formation machinery of Helicobacter pylori, a leading cause of ulcers and a risk factor for stomach cancer worldwide.

Methods and Results

The protein HP0231 from H. pylori, a structural counterpart of E. coli DsbG, is the focus of this research. Its function was clarified by using a combination of biochemical, microbiological and genetic approaches. In particular, we determined the biochemical properties of HP0231 as well as its redox state in H. pylori cells.

Conclusion

Altogether our results show that HP0231 is an oxidoreductase that catalyzes disulfide bond formation in the periplasm. We propose to call it HpDsbA.

Two-dimensional gel electrophoresis in bacterial proteomics

Two-dimensional gel electrophoresis (2-DE) is a gel-based technique widely used for analyzing the protein composition of biological samples. It is capable of resolving complex mixtures containing more than a thousand protein components into individual protein spots through the coupling of two orthogonal biophysical separation techniques: isoelectric focusing (first dimension) and polyacrylamide gel electrophoresis (second dimension). 2-DE is ideally suited for analyzing the entire expressed protein complement of a bacterial cell: its proteome. Its relative simplicity and good reproducibility have led to 2-DE being widely used for exploring proteomics within a wide range of environmental and medically-relevant bacteria. Here we give a broad overview of the basic principles and historical development of gel-based proteomics, and how this powerful approach can be applied for studying bacterial biology and physiology. We highlight specific 2-DE applications that can be used to analyze when, where and how much proteins are expressed. The links between proteomics, genomics and mass spectrometry are discussed. We explore how proteomics involving tandem mass spectrometry can be used to analyze (post-translational) protein modifications or to identify proteins of unknown origin by de novo peptide sequencing. The use of proteome fractionation techniques and non-gel-based proteomic approaches are also discussed. We highlight how the analysis of proteins secreted by bacterial cells (secretomes or exoproteomes) can be used to study infection processes or the immune response. This review is aimed at non-specialists who wish to gain a concise, comprehensive and contemporary overview of the nature and applications of bacterial proteomics.

Single dose novel Salmonella vaccine enhances resistance against visceralizing L. major and L. donovani infection in susceptible BALB/c mice

Visceral leishmaniasis is a major neglected tropical disease, with an estimated 500,000 new cases and more than 50,000 deaths attributable to this disease every year. Drug therapy is available but costly and resistance against several drug classes has evolved. Despite all efforts, no commercial, let alone affordable, vaccine is available to date. Thus, the development of cost effective, needle-independent vaccines is a high priority. Here, we have continued efforts to develop live vaccine carriers based on recombinant Salmonella. We used an in silico approach to select novel Leishmania parasite antigens from proteomic data sets, with selection criteria based on protein abundance, conservation across Leishmania species and low homology to host species. Five chosen antigens were differentially expressed on the surface or in the cytosol of Salmonella typhimurium SL3261. A two-step procedure was developed to select optimal Salmonella vaccine strains for each antigen, based on bacterial fitness and antigen expression levels. We show that vaccine strains of Salmonella expressing the novel Leishmania antigens LinJ08.1190 and LinJ23.0410 significantly reduced visceralisation of L. major and enhanced systemic resistance against L. donovani in susceptible BALB/c mice. The results show that Salmonella are valid vaccine carriers for inducing resistance against visceral leishmaniasis but that their use may not be suitable for all antigens.

Structural and functional characterization of Helicobacter pylori DsbG

Dsb proteins play important roles in bacterial pathogenicity. To better understand the role of Dsb proteins in Helicobacter pylori, we have structurally and functionally characterized H. pylori DsbG (HP0231). The monomer consists of two domains connected by a helical linker. Two monomers associate to form a V-shaped dimer. The monomeric and dimeric structures of H. pylori DsbG show significant differences compared to Escherichia coli DsbG. Two polyethylene glycol molecules are bound in the cleft of the V-shaped dimer, suggesting a possible role as a chaperone. Furthermore, we show that H. pylori DsbG functions as a reductase against HP0518, a putative L,D-transpeptidase with a catalytic cysteine residue.

Development of vaccines against Helicobacter pylori

Helicobacter pylori is a Gram-negative, microaerophilic bacterium adapted to survive in the stomach of humans where it can cause peptide ulcers and gastric cancer. Although effective antibiotic treatment exists, there is a consensus that vaccines are necessary to limit the severity of this infection. Great progress has been made since its discovery 25 years ago in understanding the virulence factors and several aspects of the pathogenesis of the H. pylori gastric diseases. Several key bacterial factors have been identified: urease, vacuolating cytotoxin, cytotoxin-associated antigen, the pathogenicity island, neutrophil-activating protein, and among others. These proteins, in their native or recombinant forms, have been shown to confer protection against infectious challenge with H. pylori in experimental animal models. It is not known, however, through which effector mechanisms this protection is achieved. Nevertheless, a number of clinical trials in healthy volunteers have been conducted using urease given orally as a soluble protein or expressed in bacterial vectors with limited results. Recently, a mixture of H. pylori antigens was reported to be highly immunogenic in H. pylori-negative volunteers following intramuscular administration of the vaccine with aluminium hydroxide as an adjuvant. These data show that vaccination against this pathogen is feasible. More research is required to understand the immunological mechanisms underlying immune-mediate protection.

Detection and evaluation of antibodies against neutrophil-activating protein of Helicobacter pylori in patients with gastric cancer

AIM: To detect and evaluate the antibodies against Helicobacter pylori (H pylori) neutrophil-activating protein (HP-NAP) in patients with gastric cancer and other gastroduodenal diseases.

METHODS: Recombinant HP-NAP was prepared from a prokaryotic expression system in Escherichia coli. Serum positivity and level of HP-NAP-specific antibodies in sera from 43 patients with gastric cancer, 28 with chronic gastritis, 28 with peptic ulcer, and 89 healthy controls were measured by rHP-NAP-based ELISA. rHP-NAP-stimulated production of interleukin-8 (IL-8) and growth-related oncogene (GRO_α) cytokines in the culture supernatant of SGC7901 gastric epithelial cells was also detected.

RESULTS: The serum positivity and mean absorbance value of HP-NAP-specific antibodies in the gastric cancer group (97.7% and 1.01 ± 0.24) were significantly higher than those in the chronic gastritis group (85.7% and 0.89 ± 0.14, P < 0.005) and healthy control group (27.7% and 0.65 ± 0.18, P < 0.001). The sensitivity and specificity of ELISA for the detection of HP-NAP-specific antibodies were 95.5% and 91.5%, respectively. HP-NAP could slightly up-regulate IL-8 production in gastric epithelial cell lines but had no effect on GRO_α production.

CONCLUSION: Infection with virulent H pylori strains secreting HP-NAP is associated with severe gastroduodenal diseases, and HP-NAP may play a role in the development of gastric carcinoma. rHP-NAP-based ELISA can be used as a new method to detect H pylori infection. The direct effect of HP-NAP on gastric epithelial cells may be limited, but HP-NAP may contribute to inflammatory response or carcinogenesis by activating neutrophils.

Association between chronic atrophic gastritis and serum antibodies to 15 Helicobacter pylori proteins measured by multiplex serology

Infection with Helicobacter pylori is a major risk factor for chronic atrophic gastritis (CAG), a precursor lesion of intestinal gastric cancer. The pathogenicity of the bacterium is thought to play an important role in determining the extent and severity of clinical outcome. We aimed to assess the associations between CAG and the serostatus of antibodies to 15 H. pylori proteins. The analyses were based on 534 cases with serologically defined CAG and 1,068 age-matched and sex-matched controls participating in a population-based study conducted in Saarland, Germany among 9,953 men and women ages 50 to 74 years. A newly developed H. pylori multiplex serology method was used to detect antibodies specific to 15 H. pylori antigens. Significant associations were observed between seropositivity for all 15 specific antibodies and the presence of CAG. Exclusion of severe cases, who might have lost the infection in the course of CAG progression, substantially increased the observed associations. In H. pylori-seropositive subjects, cytotoxin-associated gene A (CagA), vacuolating toxin (VacA), helicobacter cysteine-rich protein C (HcpC), and the chaperonin GroEL were identified as independent virulence factors for CAG with adjusted odds ratios (95% confidence interval) of 3.52 (2.01-6.10), 3.19 (1.44-7.05), 4.03 (1.53-10.65), and 2.65 (1.06-6.62), respectively; the simultaneous presence of all four independent virulence factors was associated with an 18-fold risk of CAG. In conclusion, HcpC and GroEL were identified as new independent virulence factors, and in combination with the established virulence factors, CagA and VacA, were strongly associated with CAG.

Correlation of T cell response and bacterial clearance in human volunteers challenged with Helicobacter pylori revealed by randomised controlled vaccination with Ty21a-based Salmonella vaccines

BACKGROUND

Helicobacter pylori remains a global health hazard, and vaccination would be ideal for its control. Natural infection appears not to induce protective immunity. Thus, the feasibility of a vaccine for humans is doubtful.

METHODS

In two prospective, randomised, double-blind, controlled studies (Paul Ehrlich Institute application nos 0802/02 and 1097/01), live vaccines against H pylori were tested in human volunteers seronegative for, and without evidence of, active H pylori infection. Volunteers (n = 58) were immunised orally with Salmonella enterica serovar Typhi Ty21a expressing H pylori urease or HP0231, or solely with Ty21a, and then challenged with 2x10(5) cagPAI(-) H pylori. Adverse events, infection, humoral, cellular and mucosal immune response were monitored. Gastric biopsies were taken before and after vaccination, and postchallenge. Infection was terminated with antibiotics.

RESULTS

Vaccines were well tolerated. Challenge infection induced transient, mild to moderate dyspeptic symptoms, and histological and transcriptional changes in the mucosa known from chronic infection. Vaccines did not show satisfactory protection. However, 13 of 58 volunteers, 8 vaccinees and 5 controls, became breath test negative and either cleared H pylori (5/13) completely or reduced the H pylori burden (8/13). H pylori-specific T helper cells were detected in 9 of these 13 (69%), but only in 6 of 45 (13%) breath test-positive volunteers (p = 0.0002; Fisher exact test). T cells were either vaccine induced or pre-existing, depending on the volunteer.

CONCLUSION

Challenge infection offers a controlled model for vaccine testing. Importantly, it revealed evidence for T cell-mediated immunity against H pylori infection in humans.

Transgenic, fluorescent Leishmania mexicana allow direct analysis of the proteome of intracellular amastigotes

Investigating the proteome of intracellular pathogens is often hampered by inadequate methodologies to purify the pathogen free of host cell material. This has also precluded direct proteome analysis of the intracellular, amastigote form of Leishmania spp., protozoan parasites that cause a spectrum of diseases that affect some 12 million patients worldwide. Here a method is presented that combines classic, isopycnic density centrifugation with fluorescent particle sorting for purification by exploiting transgenic, fluorescent parasites to allow direct proteome analysis of the purified organisms. By this approach the proteome of intracellular Leishmania mexicana amastigotes was compared with that of extracellular promastigotes that are transmitted by insect vectors. In total, 509 different proteins were identified by mass spectrometry and database search. This number corresponds to approximately 6% of gene products predicted from the reference genome of Leishmania major. Intracellular amastigotes synthesized significantly more proteins with basic pI and showed a greater abundance of enzymes of fatty acid catabolism, which may reflect their living in acidic habitats and metabolic adaptation to nutrient availability, respectively. Bioinformatics analyses of the genes corresponding to the protein data sets produced clear evidence for skewed codon usage and translational bias in these organisms. Moreover analysis of the subset of genes whose products were more abundant in amastigotes revealed characteristic sequence motifs in 3'-untranslated regions that have been linked to translational control elements. This suggests that proteome data sets may be used to identify regulatory elements in mRNAs. Last but not least, at 6% coverage the proteome identified all vaccine antigens tested to date. Thus, the present data set provides a valuable resource for selection of candidate vaccine antigens.

Tip-alpha (hp0596 gene product) is a highly immunogenic Helicobacter pylori protein involved in colonization of mouse gastric mucosa

A product of the Helicobacter pylori hp0596 gene (Tip-alpha) is a highly immunogenic homodimeric protein, unique for this bacterium. Cell fractionation experiments indicate that Tip-alpha is anchored to the inner membrane. In contrast, the three-dimensional model of the protein suggests that Tip-alpha is soluble or, at least, largely exposed to the solvent. hp0596 gene knockout resulted in a significant decrease in the level of H. pylori colonization as measured by real-time PCR assay. In addition, the Tip-alpha recombinant protein was determined to stimulate macrophage to produce IL-1alpha and TNF-alpha. Both results imply that Tip-alpha is rather loosely connected to the inner membrane and potentially released during infection.

[Production of Antibody against Helicobacter pylori HP0231.]

BACKGROUND

Stool antigen detection kits for diagnosis of infection of Helicobacter pylori have been widely used for their convenience, but are mostly imported. Since Helicobacter pylori strains show a distinctive genetic diversity, it is important to find a protein that is a common antigen among various strains and shows a strong immunogenicity for the development of a stool antigen detection kit. HP0231 protein strongly reacts with the sera of patients suffering from gastritis and peptic ulcer. Therefore, HP0231 is an excellent candidate as a target gene for this study.

METHODS

Chromosomal DNA from H. pylori was isolated. HP0231 gene was amplified by PCR, cloned into pET28a(+) vector, and overexpressed using isopropyl-beta-D-thiogalactopyranoside in E. coli BL21 (DE3). HP0231 protein was purified by Ni-NTA affinity chromatography followed by electroelution after SDS-PAGE. Rabbits were immunized with the purified HP0231 protein for the production of antibodies. Rabbit anti-HP0231 antibody was partially purified and tested for the sensitivity and specificity using ELISA and Western Blot Analysis.

RESULTS

The sequence of the cloned HP0231 gene was identical with the gene sequence from Genbank (AA216016). HP0231 gene was overexpressed and HP0231 protein was purified. Rabbit anti-HP0231 antibody produced after immunization with the purified HP0231 protein reacted with the purified HP0231 protein, cell extracts from cultured H. pylori, and stomach biopsy tissue from patients, but not with cell extracts from cultured E. coli used as a negative control. After 1 million fold dilution, rabbit anti-HP0231 antibody still reacted with 1 microg of HP0231 protein.

CONCLUSIONS

Rabbit anti-HP0231 antibody was produced to detect HP0231 protein of H. pylori and will be tested for the development of a stool antigen detection kit for H. pylori.

Immunology of Helicobacter pylori: insights into the failure of the immune response and perspectives on vaccine studies

Helicobacter pylori infects the stomach of half of the human population worldwide and causes chronic active gastritis, which can lead to peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. The host immune response to the infection is ineffective, because the bacterium persists and the inflammation continues for decades. Bacterial activation of epithelial cells, dendritic cells, monocytes, macrophages, and neutrophils leads to a T helper cell 1 type of adaptive response, but this remains inadequate. The host inflammatory response has a key functional role in disrupting acid homeostasis, which impacts directly on the colonization patterns of H pylori and thus the extent of gastritis. Many potential mechanisms for the failure of the host response have been postulated, and these include apoptosis of epithelial cells and macrophages, inadequate effector functions of macrophages and dendritic cells, VacA inhibition of T-cell function, and suppressive effects of regulatory T cells. Because of the extent of the disease burden, many strategies for prophylactic or therapeutic vaccines have been investigated. The goal of enhancing the host's ability to generate protective immunity has met with some success in animal models, but the efficacy of potential vaccines in humans remains to be demonstrated. Aspects of H pylori immunopathogenesis are reviewed and perspectives on the failure of the host immune response are discussed. Understanding the mechanisms of immune evasion could lead to new opportunities for enhancing eradication and prevention of infection and associated disease.

Potential role of thiol:disulfide oxidoreductases in the pathogenesis ofHelicobacter pylori

Helicobacter pylori infections are responsible for a sequence of molecular events which ultimately result in the development of gastric diseases. The pathogenesis of H. pylori has been studied extensively with strong focus on the identification of virulence factors. In contrast, the involvement of thiol:disulfide oxidoreductases in bacterial pathogenesis is less well understood. This paper provides a review of the current knowledge of H. pylori putative thiol:disulfide oxidoreductases, and their potential role in promoting virulence and colonization. Several bioinformatic analyses served to complete the information on these oxidoreductases of H. pylori.

Antigen selection based on expression levels during infection facilitates vaccine development for an intracellular pathogen

Vaccines effective against intracellular pathogens could save the lives of millions of people every year, but vaccine development has been hampered by the slow largely empirical search for protective antigens. In vivo highly expressed antigens might represent a small attractive antigen subset that could be rapidly evaluated, but experimental evidence supporting this rationale, as well as practical strategies for its application, is largely lacking because of technical difficulties. Here, we used Salmonella strains expressing differential amounts of a fluorescent model antigen during infection to show that, in a mouse typhoid fever model, CD4 T cells preferentially recognize abundant Salmonella antigens. To identify a large number of natural Salmonella antigens with high expression levels during infection, we used a quantitative in vivo screening strategy. Immunization studies with five particularly attractive candidates revealed two highly protective antigens that might permit the development of an improved typhoid fever vaccine. In conclusion, we have established a rationale and an experimental strategy that will substantially facilitate vaccine development for Salmonella and possibly other intracellular pathogens.

Helicobacter pylori: current status and future prospects

Helicobacter pylori is a global pathogen that causes severe gastrointestinal diseases leading to a significant morbidity and mortality. There is an effective treatment for peptic ulcer disease, however, this is being compromised by an increase in the prevalence of antibiotic resistance. Although alternative rescue regimens have been advocated, the best strategy would be to prevent disease, especially in the case of gastric cancer for which there is still no treatment. One approach is to inhibit the first step in the pathogenic process - adhesion of the organism to the host tissue. Another and probably a better approach is vaccination, but clinical trials have so far been unsuccessful. There is still a large uncertainty in relation to how H. pylori causes disease. Knowledge from genomics, proteomics, and the relationship between polymorphism of the bacterium and the host, as well as the continuing investigation of the role played by important virulence factors in the outcome of the disease, will help both in understanding pathogenesis of disease and in the design of the best vaccine.

Analysis of Automatically Generated Peptide Mass Fingerprints of Cellular Proteins and Antigens from Helicobacter pylori 26695 Separated by Two-dimensional Electrophoresis

Helicobacter pylori is a causative agent of severe diseases of the gastric tract ranging from chronic gastritis to gastric cancer. Cellular proteins of H. pylori were separated by high resolution two-dimensional gel electrophoresis. A dataset of 384 spots was automatically picked, digested, spotted, and analyzed by matrix-assisted laser desorption ionization mass spectrometry peptide mass fingerprint in triple replicates. This procedure resulted in 960 evaluable mass spectra. Using a new version of our data analysis software MS-Screener we improved identification and tested reliability of automatically generated data by comparing with manually produced data. Antigenic proteins from H. pylori are candidates for vaccines and diagnostic tests. Previous immunoproteomics studies of our group revealed antigen candidates, and 24 of them were now closely analyzed using the MS-Screener software. Only in three spots minor components were found that may have influenced their antigenicities. These findings affirm the value of immunoproteomics as a hypothesis-free approach. Additionally, the protein species distribution of the known antigen GroEL was investigated, dimers of the protein alkyl hydroperoxide reductase were found, and the fragmentation of gamma-glutamyltranspeptidase was demonstrated.

Genomics of helicobacter 2003

Research on Helicobacter pylori has been driven by the field of genomics since the release of the first of two complete genome sequences in 1997. In this review we highlight progress made in the last year. New bioinformatics tools and methods promise better functional and strain comparative analyses of individual genes. Sequence-based methods of strain comparison documented the coevolution of H. pylori with human populations. Several comprehensive analyses of the bacterial transcriptome were undertaken as well as two sophisticated studies of the transcriptional response of specific host tissues in response to H. pylori infection using different mouse models of H. pylori diseases. Some progress was made in developing genetic tools for mutational analysis of the genes required for infection. Finally, proteomic approaches were refined to delineate surface exposed and secreted proteins that represent potential antigens. In summary, while we do not have the full story of H. pylori, significant progress in deciphering the genome into functional biology has been made.

The quest for a vaccine against Helicobacter pylori: how to move from mouse to man?

Several lines of evidence from experimental animal models of infection have clearly demonstrated the feasibility of a prophylactic and therapeutic vaccine against Helicobacter pylori. However, comparatively few clinical studies have been carried out to evaluate whether the positive results obtained in animals can be reproduced in humans. The preliminary results obtained with single component, mucosally delivered vaccines have shown very limited results thus far. Very good immunogenicity and safety profiles are now being obtained with parenterally delivered, aluminium hydroxide-adjuvanted multicomponent candidate vaccines. For sure, better vaccine formulations, better antigen preparation(s), better adjuvants, and better delivery systems have to be designed and tested for safety and immunogenicity. These studies are also needed for deciphering those aspects of the effector immune responses that correlate with protection against H. pylori infection and disease.