The current status of Helicobacter pylori vaccines: a review

Adjuvants for Helicobacter pylori vaccines: Outer membrane vesicles provide an alternative strategy

Helicobacter pylori (H. pylori) is a gram-negative, spiral-shaped bacterium that colonizes the human stomach, leading to various gastric diseases. The efficacy of traditional treatments, such as bismuth-based triple and quadruple therapies, has been reduced due to increasing antibiotic resistance and drug toxicity. As a result, the development of effective vaccines was proposed to control H. pylori-induced infections; however, one of the primary challenges is the lack of potent adjuvants. Although various adjuvants, both toxic (e.g. cholera toxin and Escherichia coli heat-labile toxin) and non-toxic (e.g. aluminum and propolis), have been tested for vaccine development, no clinically favorable adjuvants have been identified due to high toxicity, weak immunostimulatory effects, inability to elicit specific immune responses, or latent side effects. Outer membrane vesicles (OMVs), mainly secreted by gram-negative bacteria, have emerged as promising candidates for H. pylori vaccine adjuvants due to their potential applications. OMVs enhance mucosal immunity and Th1 and Th17 cell responses, which have been recognized to have protective effects and guarantee safety and efficacy. The development of an effective vaccine against H. pylori infection is ongoing, with clinical trials expected in the future.

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.

Diagnosis of Helicobacter pylori infection using immunochromatography among patients attending Tamboul Hospital in Gezira State, Sudan: a cross-sectional study

Background: Helicobacter pylori causes a major health problem worldwide; more than half of the world’s population are infected with this pathogen. The diagnosis of the infection was initially made through invasive methods, but now non-invasive methods have been developed to make diagnosis easier. This study aimed to screen the presence of H.pylori antibodies and antigen among symptomatic and asymptomatic patients at Tamboul City in Gezira State. Methods: A cross-sectional study was conducted in Tamboul city, Gezira State, Sudan between March 2016 and December 2019 to compare between antigen and antibody tests results used for diagnosis of H. pylori infection among symptomatic and asymptomatic Sudanese patients. Stool and blood samples were collected and analyzed for presence of antigen and antibodies to H. pylori using immunochromatography (ICT) cards. Results: Serum and stool samples were collected from 100 patients; 50 were symptomatic and 50 were asymptomatic. In symptomatic patients, 18/50 (36%) were men (32; 64%, women) with mean age of 16.7±24.6 years. In this group, 35/50 (70%) showed positive results for stool antigen, while 30/50 (60%) were positive for serum antibodies. In asymptomatic patients, 19/50 (38%) were men (31; 62%, women) with mean age of 16.7±20.4 years. In this group, 18/50 (36%) were positive for stool antigen and 25/50 (50%) for serum antibodies. There was a significant association between antigen results and patient group (P=0.001), but there was an insignificant association between antibodies results and patient group (P=0.317). Age group, history of infected persons in the family, blood group, and previous treatment were all not associated with H. pylori infection (P≥0.05). Conclusion: The frequency of H. pylori antigen was higher than antibodies in symptomatic patients, while the frequency of H. pylori antibodies was higher than antigen in asymptomatic patients.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.

Antigenic and immunogenic evaluation of Helicobacter pylori FlaA epitopes

Objective(s):

Helicobacter pylori are among most common human pathogens affecting at least half of the world’s population. Mobility is one of the important primary factors in bacterial colonization and invasion. The purpose of this research is cloning, expression, and purification of FlaA protein specific epitopes in order to evaluate their antigenicity and immunogenicity.

Materials and Methods:

The antigenic region of the flaA gene was bioinformatically predicted using Epitope mapping software’s and the predicted epitopes were expressed in a prokaryotic expression vector. The antigen was injected into the animal model (mice BALB/c) and some indicators including IgG1, IgG2a, IgA, IFN-γ, and IL 5 were measured.

Results:

The immunogenicity studies in animal models by measuring serum antibodies (IgG1, IgG2a, and IgA) and cytokines (IFN-γ and IL5) revealed that the rFlaA induces a proper immune response in animal models.

Conclusion:

The recombinant FlaA protein is antigenic and immunogenic. Therefore, it might be used in order to design of specific diagnostic kits and recombinant vaccines against H. pylori.

The study of H. pylori putative candidate factors for single- and multi-component vaccine development

Helicobacter pylori has grown to colonize inside the stomach of nearly half of the world's population, turning into the most prevalent infections in the universe. Medical care failures noticeably confirm the need for a vaccine to hinder or deal with H. pylori. This review is planned to discuss the most known factors as a vaccine candidate, including single (AhpC, BG, CagA, KatA, Fla, Hsp, HWC, Lpp, LPS, NAP, OMP, OMV, SOD, Tpx, Urease, VacA) and multi-component vaccines. Many promising results in the field of single and multivalent vaccine can be seen, but there is no satisfactory outcome and neither a prophylactic nor a therapeutic vaccine to treat or eradicate the infection in human has been acquired. Hence, selecting suitable antigen is an important factor as an appropriate adjuvant. Taken all together, the development of efficient anti-H. pylori vaccines relies on the fully understanding of the interactions between H. pylori and its host immune system. Therefore, more work should be done on epitope mapping, analysis of molecular structure, and determination of the antigen determinant region as well due to design a vaccine, preferably a multi-component vaccine to elicit specific CD4 T-cell responses that are required for H. pylori vaccine efficacy.

Helicobacter pylori outer inflammatory protein DNA vaccine-loaded bacterial ghost enhances immune protective efficacy in C57BL/6 mice

Helicobacter pylori (H. pylori) infection is associated with incidents of gastrointestinal diseases in half of the human population. However, management of its infection remains a challenge. Hence, it is necessary to develop an efficient vaccine to fight against this pathogen. In the present study, a novel vaccine based on the production of attenuated Salmonella typhimurium bacterial ghost (SL7207-BG), delivering H. pylori outer inflammatory protein gene (oipA) encoded DNA vaccine was developed, and the efficiency was evaluated in C57BL/6 mice. Significant higher levels of IgG2a/IgG1 antibodies and IFN-γ/IL-4 cytokines were detected after mice were oral administered with oipA DNA vaccine loaded SL7207-BG, indicating that a mixed Th1/Th2 immune response was elicited. When challenged with infective doses H. pylori strain SS1, the ghost based vaccine was capable of reducing bacterium colonization in the vaccinated mice. In addition, codon-optimized oipA plasmid loaded SL7207-BG significantly eliminates H. pylori colonization density in mice model. Thus, it has been demonstrated that this novel bacterial ghost based DNA vaccine could be used as a promising vaccine candidate for the control of H. pylori infection.

Structures and metal-binding properties of Helicobacter pylori neutrophil-activating protein with a di-nuclear ferroxidase center

Helicobacter pylori causes severe diseases, such as chronic gastritis, peptic ulcers, and stomach cancers. H. pylori neutrophil-activating protein (HP-NAP) is an iron storage protein that forms a dodecameric shell, promotes the adhesion of neutrophils to endothelial cells, and induces the production of reactive oxygen radicals. HP-NAP belongs to the DNA-protecting proteins under starved conditions (Dps) family, which has significant structural similarities to the dodecameric ferritin family. The crystal structures of the apo form and metal-ion bound forms, such as iron, zinc, and cadmium, of HP-NAP have been determined. This review focused on the structures and metal-binding properties of HP-NAP. These metal ions bind at the di-nuclear ferroxidase center (FOC) by different coordinating patterns. In comparison with the apo structure, metal loading causes a series of conformational changes in conserved residues among HP-NAP and Dps proteins (Trp26, Asp52, and Glu56) at the FOC. HP-NAP forms a spherical dodecamer with 23 symmetry including two kinds of pores. Metal ions have been identified around one of the pores; therefore, the negatively-charged pore is suitable for the passage of metal ions.

Exploring alternative treatments for Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a successful pathogen that can persist in the stomach of an infected person for their entire life. It provokes chronic gastric inflammation that leads to the development of serious gastric diseases such as peptic ulcers, gastric cancer and Mucosa associated lymphoid tissue lymphoma. It is known that these ailments can be avoided if the infection by the bacteria can be prevented or eradicated. Currently, numerous antibiotic-based therapies are available. However, these therapies have several inherent problems, including the appearance of resistance to the antibiotics used and associated adverse effects, the risk of re-infection and the high cost of antibiotic therapy. The delay in developing a vaccine to prevent or eradicate the infection has furthered research into new therapeutic approaches. This review summarises the most relevant recent studies on vaccine development and new treatments using natural resources such as plants, probiotics and nutraceuticals. In addition, novel alternatives based on microorganisms, peptides, polysaccharides, and intragastric violet light irradiation are presented. Alternative therapies have not been effective in eradicating the bacteria but have been shown to maintain low bacterial levels. Nevertheless, some of them are useful in preventing the adverse effects of antibiotics, modulating the immune response, gastroprotection, and the general promotion of health. Therefore, those agents can be used as adjuvants of allopathic anti-H. pylori eradication therapy.

Helicobacter pylori research: historical insights and future directions

Helicobacter pylori leads to chronic gastritis, peptic ulcer disease and gastric cancer. With increasing issues of antibiotic resistance and changing epidemiology of this pathogen, new approaches are needed for effective management. In 1984, Dr Barry Marshall and Dr Robin Warren reported the association of Helicobacter pylori with peptic ulcers in The Lancet--a discovery that earned them the Nobel prize in Physiology or Medicine in 2005--but what progress have we made since then? Here, we have invited three international experts to give their insights into the advances in H. pylori research over the past 30 years and where research should be focused in the future.

Gastroprotective and anti-Helicobacter pylori potential of herbal formula HZJW: safety and efficacy assessment

Background

A traditional Chinese Medicine (TCM) formula, HZJW, has been applied in clinics in China for gastrointestinal disorders. However, the therapeutic mechanism underlying its efficacy and safety remained to be defined. The present investigation was undertaken to evaluate the formula HZJW for its gastroprotective potential, possible effect on Helicobacter pylori along with safety to justify its anti-ulcer action and safe clinical application.

Methods

The gastroduodenal cytoprotective potential was evaluated in rodent experimental models (HCl/Ethanol and NSAID-induced ulcer protocols). The anti-H. pylori property was assessed by agar dilution assay in vitro and analysis in vivo including rapid urease test, immunogold test and histopathology. For toxicity assessment, acute toxicity study was performed according to fixed dose procedure with a single oral administration of HZJW to mice. In the oral chronic toxicity, rats (80 males, 80 females) were administrated HZJW orally in 0, 1000, 2500, or 5000 mg/kg/day doses for 26 weeks (n = 40/group of each sex). Clinical signs, mortality, body weights, feed consumption, ophthalmology, hematology, serum biochemistry, gross findings, organ weights and histopathology were examined at the end of the 13- and 26-week dosing period, as well as after the 4-week recovery period.

Results

In the HCl/Ethanol-induced ulcer model, it was observed that oral administration with HZJW (260, 520 and 1040 mg/kg) and ranitidine (250 mg/kg) significantly reduced the ulcerative lesion index (116.70 ± 36.4, 102.20 ± 18.20, 84.10 ± 12.1 and 73.70 ± 16.70) in a dose-dependent manner, respectively, with respect to control group (134.10 ± 31.69). Significant inhibition was also observed in ulcerative index from aspirin-induced ulcer model, with decreases of 35.40 ± 5.93, 31.30 ± 8.08, 26.80 ± 8.27and 20.40 ± 6.93 for the groups treated with HZJW and ranitidine, in parallel to controls (41.60 ± 10.80). On the other hand, treatment with HZJW efficaciously eradicated H. pylori in infected mice in rapid urease test (RUT) and immunogold antibody assay, as further confirmed by reduction of H. pylori presence in histopathological analysis. In the in vitro assay, MICs for HZJW and amoxicillin (positive control) were 125 and 0.12 μg/mL respectively. The LD₅₀ of HZJW was over 18.0 g/kg for mice. No drug-induced abnormalities were found as clinical signs, body weight, food consumption, hematology, blood biochemistry, ophthalmology and histopathology results across three doses. No target organ was identified. The No Observed Adverse Effect Level (NOAEL) of HZJW was determined to be 5,000 mg/kg/day for both sexes, a dose that was equivalent to 50 times of human dose.

Conclusions

These results suggested the efficacy and safety of HZJW in healing peptic ulcer and combating H. pylori, which corroborated their conventional indications and contributed to their antiulcer pharmacological validation, lending more credence to its clinical application for the traditional treatment of stomach complaints symptomatic of peptic ulcer disease (PUD). HZJW might have the potential for further development as a safe and effective alternative/complementary to conventional medication in treating gastrointestinal (GI) disorders.

A role for altered phagosome maturation in the long-term persistence of Helicobacter pylori infection

The vigorous host immune response that is mounted against Helicobacter pylori is unable to eliminate this pathogenic bacterium from its niche in the human gastric mucosa. This results in chronic inflammation, which can develop into gastric or duodenal ulcers in 10% of infected individuals and gastric cancer in 1% of infections. The determinants for these more severe pathologies include host (e.g., high IL-1β expression polymorphisms), bacterial [e.g., cytotoxicity-associated gene (cag) pathogenicity island], and environmental (e.g., dietary nitrites) factors. However, it is the failure of host immune effector cells to eliminate H. pylori that underlies its persistence and the subsequent H. pylori-associated disease. Here we discuss the mechanisms used by H. pylori to survive the host immune response and, in particular, the role played by altered phagosome maturation.

Inhibition of H. pylori colonization and prevention of gastritis in murine model

Helicobacter pylori is a Gram-negative spiral bacterium that colonizes human gastric mucosa causing infection. In this study aiming at inhibition of H. pylori infection we made an attempt to evaluate immunogenicity of the total (UreC) and C-terminal (UreCc) fragments of H. pylori urease. Total UreC and its C-terminal fragment were expressed in E. coli. Recombinant proteins were analyzed by SDS-PAGE and western blot and then purified by Ni-NTA affinity chromatography. Female C57BL6/j mice were immunized with the purified proteins (UreC and UreCc). Antibody titers from isolated sera were measured by ELISA. Immunized mice were then challenged by oral gavage with live H. pylori Sydney strain SS1. Total of 109 CFU were inoculated into stomach of immunized and unimmunized healthy mice three times each at one day interval. Eight weeks after the last inoculation, the blood sample was collected and the serum antibody titer was estimated by ELISA. Stomach tissues from control and experimental animal groups were studied histopathologically. UreC and UreCc yielded recombinant proteins of 61 and 31 kDa respectively. ELIZA confirmed establishment of immunity and the antibodies produced thereby efficiently recognized H. pylori and inhibited its colonization in vivo. Pathological analysis did not reveal established infection in immunized mice challenged with H. pylori. The results support the idea that UreC and UreCc specific antibodies contribute to protection against H. pylori infections.

Crystal structure of Helicobacter pylori neutrophil-activating protein with a di-nuclear ferroxidase center in a zinc or cadmium-bound form

Helicobacter pylori neutrophil-activating protein (HP-NAP) is a Dps-like iron storage protein forming a dodecameric shell, and promotes adhesion of neutrophils to endothelial cells. The crystal structure of HP-NAP in a Zn(2+)- or Cd(2+)-bound form reveals the binding of two zinc or two cadmium ions and their bridged water molecule at the ferroxidase center (FOC). The two zinc ions are coordinated in a tetrahedral manner to the conserved residues among HP-NAP and Dps proteins. The two cadmium ions are coordinated in a trigonal-bipyramidal and distorted octahedral manner. In both structures, the second ion is more weakly coordinated than the first. Another zinc ion is found inside of the negatively-charged threefold-related pore, which is suitable for metal ions to pass through.

Alternative therapies for Helicobacter pylori: probiotics and phytomedicine

Helicobacter pylori is a common human pathogen infecting about 30% of children and 60% of adults worldwide and is responsible for diseases such as gastritis, peptic ulcer and gastric cancer. Treatment against H. pylori is based on the use of antibiotics, but therapy failure can be higher than 20% and is essentially due to an increase in the prevalence of antibiotic-resistant bacteria, which has led to the search for alternative therapies. In this review, we discuss alternative therapies for H. pylori, mainly phytotherapy and probiotics. Probiotics are live organisms or produced substances that are orally administrated, usually in addition to conventional antibiotic therapy. They may modulate the human microbiota and promote health, prevent antibiotic side effects, stimulate the immune response and directly compete with pathogenic bacteria. Phytomedicine consists of the use of plant extracts as medicines or health-promoting agents, but in most cases the molecular mode of action of the active ingredients of these herbal extracts is unknown. Possible mechanisms include inhibition of H. pylori urease enzyme, disruption of bacterial cell membrane, and modulation of the host immune system. Other alternative therapies are also reviewed.

Treatment of Helicobacter pylori infection in mice with oral administration of egg yolk-driven anti-UreC immunoglobulin

BACKGROUND

Helicobacter pylori, the causative agent of gastritis and gastric ulcer, plays a crucial role in development of gastric carcinomas. Antibiotic therapy fails in almost 20% of cases due to development of antibiotic resistance. Development of antibodies against specific H. pylori targets could have significant therapeutic effect. In the present research attempts have been made to study the effect of IgY purified from egg yolk of hens immunized with recombinant UreC in treatment of mice infected with H. pylori.

MATERIALS AND METHODS

Purified IgY-HpUc was used in two forms: powdered and PBS dissolved. 10(9) bacteria in BHI were orally administered to C57BL6/j mice three times on alternate day intervals. Eight weeks after the last inoculation, the serum was assayed for infection rate by ELISA. The severity of gastritis was analyzed histopathologically. Infected mice were randomly divided into three groups. Groups one and two were treated with dietary IgY-HpUc and IgY-HpUc dissolved in PBS respectively for 28 days. The untreated group served as control.

RESULTS

Serology and histopathology confirmed the establishment of the infection. Indirect ELISA results in the treated animals showed considerable reduction of H. pylori specific antibodies in their sera. Pathological examination of gastric mucosa of infected mice treated with IgY-HpUc showed considerable reduction of inflammation in the stomach tissues. The bacterial presence on mucosal layer of the stomach was considerably reduced.

CONCLUSIONS

UreC-induced IgY is specifically successful in inhibition of H. pylori infection and could be an alternative to antibiotic treatment.

The role of interleukin-17 in the Helicobacter pylori induced infection and immunity

BACKGROUND

Helicobacter pylori infection is regarded as the major cause of various gastric diseases and induces the production of several cytokines including interleukin-17 (IL-17) recently recognized as an important player in the mammalian immune system.

OBJECTIVE

This review deals with the role of IL-17 on the H. pylori-induced infection and immunity in humans and experimental animals.

RESULTS

H. pylori infection increases IL-17 in the gastric mucosa of humans and experimental animals. In humans, IL-17 induces the secretion of IL-8 by activating the ERK 1/2 MAP kinase pathway and the released IL-8 attracts neutrophils promoting inflammation. IL-23 is increased in patients with H. pylori-related gastritis and regulates IL-17 secretion via STAT3 pathway. Studies in H. pylori-infected mice indicate that IL-17 is primarily associated with gastric inflammation. The early events in the immune response of immunized and challenged mice include the recruitment of T cells and the production of IL-17. Neutrophil attracting chemokines are released, and the bacterial load is considerably reduced. IL-17 plays a dual role in infection and vaccination. In infection, T regulatory cells (Tregs) suppress the inflammatory reaction driven by IL-17 thereby favoring bacterial persistence. Immunization produces Helicobacter-specific memory T-helper cells that can possibly alter the ratio between T-helper 17 and Treg responses so that the IL-17-driven inflammatory reaction can overcome the Treg response leading to bacterial clearance.

CONCLUSION

IL-17 plays an important role in H. pylori-related gastritis and in the reduction of Helicobacter infection in mice following immunization.

Immunogenicity of attenuated measles virus engineered to express Helicobacter pylori neutrophil-activating protein

Helicobacter pylori is a Gram-negative, spiral-shaped microorganism associated with acute and chronic gastritis, peptic ulcer, gastric cancer and gastric lymphomas in humans. H. pylori neutrophil-activating protein (NAP) is a major virulence factor playing a central role in pathogenesis of mucosal inflammation by immune cell attraction and Th1 cytokine response polarization. NAP is protective antigen and promising vaccine candidate against H. pylori infection. Here we present the development of measles virus (MV) vaccine strain encoding the NAP antigen. In order to facilitate the extracellular transport and detection, NAP was inserted in the human lambda immunoglobulin chain replacing a major part of the variable domain. We generated two MV vectors expressing secretory NAP forms: MV-lambda-NAP encoding the full-length constant lambda light chain domain and MV-s-NAP encoding only the N-terminus of the lambda light chain with the leader peptide. Immunization of MV permissive Ifnarko-CD46Ge transgenic mice by a single intraperitoneal injection of the NAP-expressing strains induced a robust, long-term humoral and cellular immune response against MV. Nine months post vaccination measles-neutralizing antibody titers were above the serum level considered protective for humans. Furthermore, all animals immunized with MV strains expressing the secretory NAP antigen developed strong humoral immunity against NAP, reaching titers >1:10,000 within 2-4 weeks. IFN-γ ELISpot assay confirmed that NAP-encoding MV vectors can also stimulate NAP-specific cell-mediated immunity. Our data demonstrate that MV is an excellent vector platform for expression of bacterial antigens and development of vaccines for H. pylori immunoprophylaxis in humans.

DNA vaccines for targeting bacterial infections

DNA vaccination has been of great interest since its discovery in the 1990s due to its ability to elicit both humoral and cellular immune responses. DNA vaccines consist of a DNA plasmid containing a transgene that encodes the sequence of a target protein from a pathogen under the control of a eukaryotic promoter. This revolutionary technology has proven to be effective in animal models and four DNA vaccine products have recently been approved for veterinary use. Although few DNA vaccines against bacterial infections have been tested, the results are encouraging. Because of their versatility, safety and simplicity a wider range of organisms can be targeted by these vaccines, which shows their potential advantages to public health. This article describes the mechanism of action of DNA vaccines and their potential use for targeting bacterial infections. In addition, it provides an updated summary of the methods used to enhance immunogenicity from codon optimization and adjuvants to delivery techniques including electroporation and use of nanoparticles.

Role of immune serum in the killing of Helicobacter pylori by macrophages

BACKGROUND

Helicobacter pylori infection can lead to the development of gastritis, peptic ulcers and gastric cancer, which makes this bacterium an important concern for human health. Despite evoking a strong immune response in the host, H. pylori persists, requiring complex antibiotic therapy for eradication. Here we have studied the impact of a patient's immune serum on H. pylori in relation to macrophage uptake, phagosome maturation, and bacterial killing.

MATERIALS AND METHODS

Primary human macrophages were infected in vitro with both immune serum-treated and control H. pylori. The ability of primary human macrophages to kill H. pylori was characterized at various time points after infection. H. pylori phagosome maturation was analyzed by confocal immune fluorescence microscopy using markers specific for H. pylori, early endosomes (EEA1), late endosomes (CD63) and lysosomes (LAMP-1).

RESULTS

Immune serum enhanced H. pylori uptake into macrophages when compared to control bacteria. However, a sufficient inoculum remained for recovery of viable H. pylori from macrophages, at 8 hours after infection, for both the serum-treated and control groups. Both serum-treated and control H. pylori phagosomes acquired EEA1 (15 minutes), CD63 and LAMP-1 (30 minutes). These markers were then retained for the rest of an 8 hour time course.

CONCLUSIONS

While immune sera appeared to have a slight positive effect on bacterial uptake, both serum-treated and control H. pylori were not eliminated by macrophages. Furthermore, the same disruptions to phagosome maturation were observed for both serum-treated and control H. pylori. We conclude that to eliminate H. pylori, a strategy is required to restore the normal process of phagosome maturation and enable effective macrophage killing of H. pylori, following a host immune response.

Protection against Helicobacter pylori infection by a trivalent fusion vaccine based on a fragment of urease B-UreB414

A multivalent fusion vaccine is a promising option for protection against Helicobacter pylori infection. In this study, UreB414 was identified as an antigenic fragment of urease B subunit (UreB) and it induced an antibody inhibiting urease activity. Immunization with UreB414 partially protected mice from H. pylori infection. Furthermore, a trivalent fusion vaccine was constructed by genetically linking heat shock protein A (HspA), H. pylori adhesin A (HpaA), and UreB414, resulting in recombinant HspA-HpaA-UreB414 (rHHU). Its protective effect against H. pylori infection was tested in BALB/c mice. Oral administration of rHHU significantly protected mice from H. pylori infection, which was associated with H. pylori-specific antibody production and Th1/Th2-type immune responses. The results show that a trivalent fusion vaccine efficiently combats H. pylori infection, and that an antigenic fragment of the protein can be used instead of the whole protein to construct a multivalent vaccine.

Helicobacter pylori immunoproteomics in gastric cancer and gastritis of the carcinoma phenotype

Helicobacter pylori infection is linked to the development of gastric cancer. Atrophic body gastritis is considered the first important step in the histogenesis of such neoplasia. H. pylori infection 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. Host-pathogen interactions may be investigated by means of immunoproteomics, which provides global information regarding the host humoral response to H. pylori infection and allows the identification of relevant specific and nonspecific antigens, and can be used for diagnostic or prognostic purposes. In the present review, we describe how several research groups used H. pylori immunoproteomics to investigate highly immunoreactive bacterial antigens related to the development of gastric cancer.

Efficacy of passive immunization with IgY antibodies to a 58-kDa H. pylori antigen on severe gastritis in BALB/c mouse model

Consecutive triple doses of 1 x 10(8) CFU/mL of a pathogenic H. pylori strain isolated from stomach of Egyptian patients with severe gastritis were used to establish infection in BALB/c mice model. White Leghorn hens were immunized with H. pylori whole cell lysate (HpLysate) antigen and with a highly reactive 58-kDa H. pylori (Hp58) antigen. Two months later, IgY antibodies (IgY-HpLysate & IgY-Hp58) were purified from egg yolk and its efficacy was evaluated in the adopted model. Microbiological culture and immunohistochemical staining revealed that H. pylori infection was inhibited 1 week after oral passive immunization in 70% of infected BALB/c mice with a significant decrease (p < 0.05) in the degrees of gastritis. In conclusion, we have adapted BALB/c mice model for human H. pylori pathogenic strain and oral passive immunization with specific IgY antibodies to the 58-kDa antigen inhibited active H. pylori infection and decreased gastritis.

Helicobacter pylori infection in developing countries: the burden for how long?

Approximately 50% (over 3 billion) of the world populations are known to be infected with Helicobacter pylori , mainly in the developing countries . Among those, hundreds of millions of people develop peptic ulceration during their lifetime and still tens of millions might progress to gastric cancer. Possible modes of H. pylori transmission generally described are through direct contact between family members and also through contaminated water and food. Because the high prevalence of infection occurs mainly in developing countries and because the test-and-treat strategy puts a huge economic burden on many of these countries, it is time to take an immediate action toward this bacterial infection and adopt a strategy to prevent it. To address this issue, an updated prevalence of infection, modes of transmission, economics of infection and preventative measures to block the infection process have been discussed.

Gastroenterology in developing countries: issues and advances

Developing countries shoulder a considerable burden of gastroenterological disease. Infectious diseases in particular cause enormous morbidity and mortality. Diseases which afflict both western and developing countries are often seen in more florid forms in poorer countries. Innovative techniques continuously improve and update gastroenterological practice. However, advances in diagnosis and treatment which are commonplace in the West, have yet to reach many developing countries. Clinical guidelines, based on these advances and collated in resource-rich environments, lose their relevance outside these settings. In this two-part review, we first highlight the global burden of gastroenterological disease in three major areas: diarrhoeal diseases, hepatitis B, and Helicobacter pylori. Recent progress in their management is explored, with consideration of future solutions. The second part of the review focuses on the delivery of clinical services in developing countries. Inadequate numbers of healthcare workers hamper efforts to combat gastroenterological disease. Reasons for this shortage are examined, along with possibilities for increased specialist training. Endoscopy services, the mainstay of gastroenterology in the West, are in their infancy in many developing countries. The challenges faced by those setting up a service are illustrated by the example of a Nigerian endoscopy unit. Finally, we highlight the limited scope of many clinical guidelines produced in western countries. Guidelines which take account of resource limitations in the form of "cascades" are advocated in order to make these guidelines truly global. Recognition of the different working conditions facing practitioners worldwide is an important step towards narrowing the gap between gastroenterology in rich and poor countries.

Refractory peptic ulcer disease

Refractory PUD is a diagnostic and therapeutic challenge. Optimal management of severe or refractory PUD requires a multidisciplinary team approach, using primary care providers, gastroenterologists, and general surgeons. Medical management has become the cornerstone of therapy. Identification and eradication of H pylori infection combined with acid reduction regimens can heal ulceration and also prevent recurrence. Severe, intractable or recurrent PUD and associated complications mandates a careful and methodical evaluation and management strategy to determine the potential etiologies and necessary treatment (medical or surgical) required.

Effect of Helicobacter pylori eradication on incidence of gastric cancer in human and animal models: underlying biochemical and molecular events

BACKGROUND

Gastric cancer remains one of the most common cancers worldwide. A strong association exists between Helicobacter pylori infection and the risk of developing noncardia gastric cancer. H. pylori eradication by antibiotic treatment is regarded as a primary chemoprevention strategy to reduce gastric cancer incidence.

AIM

To analyze the efficacy of H. pylori eradication in preventing gastric cancer in human and animal models, and to discuss whether biochemical, genetic, and epigenetic changes associated with H. pylori infection are reversible after curing the infection.

RESULTS

Several intervention trials have indicated that in some patients, H. pylori eradication leads to regression and prevents the progression of precancerous lesions. The eradication therapy reduces gastric cancer incidence in patients without any precancerous lesions at the baseline and is most effective before the development of atrophic gastritis. A few recent intervention studies in Japan have demonstrated significant prophylactic effects of eradication therapy on the development of gastric cancer, suggesting the use of eradication therapy in high-risk populations as a gastric cancer reduction strategy. However, gastric cancer may still develop despite successful eradication therapy. Studies in animal models have confirmed the use of eradication therapy at an early point of infection to prevent gastric cancer development.

CONCLUSION

H. pylori eradication may not completely abolish the risk of gastric cancer. However, eradication therapy may be used in high-risk populations to reduce gastric cancer incidence. It can reverse many biochemical, genetic, and epigenetic changes that H. pylori infection induces in the stomach.

Review article: 'true' re-infection of Helicobacter pylori after successful eradication--worldwide annual rates, risk factors and clinical implications

BACKGROUND

The incidence of 'true' re-infection with Helicobacter pylori after successful eradication remains uncertain.

AIM

To determine the worldwide rates, risk factors and clinical implications of 'true' re-infection of Helicobacter pylori. 'True' re-infection of H. pylori is defined as the situation where tests for H. pylori infection, which were negative for 12 months after eradication, become positive again at a later stage.

RESULTS

Thirty six studies were identified through a literature search to be able to produce annual rates of 'true' re-infection, and data from 33 original articles were considered reliable and adequate in the further review. Generally, the reported rates varied from 0% to 23.4% in adults and from 1.9% to 9.6% in children. Most studies from developed countries reported rates of less than 1%, whereas relatively higher rates were reported in most of the developing countries. Small sample sizes included in the studies appeared to be associated with increased re-infection rates. Interfamilial transmission is the major cause of re-infection, although iatrogenic re-infection through contaminated endoscopic equipment has been reported.

CONCLUSION

Helicobacter pylori re-infection is not a concern in a clinical setting, especially in the developed world; however, caution must be exercised in most developing countries.

Cost-effectiveness of a potential future Helicobacter pylori vaccine in the Netherlands: the impact of varying the discount rate for health

To estimate the cost-effectiveness of a potential Helicobacter pylori (HP) vaccine for the Dutch situation, we developed a Markov model. Several HP prevalence scenarios were assessed. Additionally, we assessed the impact of the discount rate for health on the outcomes, as this influence can be profound for vaccines. When applying the current discount rate of 1.5% for health, the expected cost-effectiveness of HP vaccination is estimated below the informal Dutch threshold of euro 20,000/LYG when the HP prevalence is assumed > or =20% in the Dutch population. In conclusion, we showed that HP vaccination could possibly be a cost-effective intervention. However, this depends to a large extend on the prevalence of HP in the population. Furthermore, we showed the large impact of the discount rate for health on the cost-effectiveness of a HP vaccination program, illustrative for other vaccination programs.

Antibodies as molecular mimics of biomolecules: roles in understanding physiological functions and mechanisms

Physiologists have routinely used understanding of the immune system to generate antibodies against regulatory molecules, growth factors, plasma membrane receptors, and other mammalian molecules in the development of analytical tools and assays. In taking this notion further, antibodies have been used in vivo to modulate physiological systems and to improve our understanding of their molecular interactions. To develop antibodies with physiological activity (efficacy), physiologists have worked with immunologists in developing interdisciplinary insights, requiring basic knowledge of immune system function in designing strategies to generate antibodies that interact with endogenous molecules of physiological interest, in vivo. Antibodies in different physiological systems have been shown to enhance or inhibit endogenous molecular functions. Two approaches have been used: passive and active immunization. Antibodies in these contexts have provided tools to develop further insights into molecular physiological mechanisms. Perhaps surprisingly, enhancing antibodies have been developed against a diverse set of target molecules including several members of the growth hormone/insulin-like growth factor-I axes and those of the beta(2)-adrenoceptor axis. Antibodies that inhibit the actions of somatostatin have also been developed. A further novel approach has been the development of antibodies that interact with adipose cells in vivo. These have the potential to be used in therapeutic antiobesity approaches. Antibodies with efficacy in vivo have provided new insights into molecular physiological mechanisms, enhancing our understanding of these complex processes.

Helicobacter hepaticus urease is not required for intestinal colonization but promotes hepatic inflammation in male A/JCr mice

Urease activity contributes to bacterial survival in the acidic environment of the stomach and is essential for persistent infection by known gastric helicobacters such as the human pathogen Helicobacter pylori. Several enterohepatic Helicobacter species (EHS) that primarily infect the less acidic intestine also have very active urease enzymes. The importance of urease and its contribution to pathogenesis for these EHS are poorly understood. In this study, we generated a urease-deficient, isogenic mutant (HhureNT9) of Helicobacter hepaticus 3B1 (Hh 3B1), an EHS that possesses a urease gene cluster similar to that of H. pylori. Lack of urease activity did not affect the level of cecal colonization by HhureNT9 compared to Hh 3B1 in male A/JCr mice (P=0.48) at 4 months post-inoculation (MPI). In contrast, there was no HhureNT9 detected in the livers of any infected mice, whereas all livers from the Hh 3B1-infected mice were PCR-positive for Hh 3B1. The mice infected with HhureNT9 developed significantly less severe hepatitis (P=0.017) and also produced significantly lower hepatic mRNA levels of proinflammatory cytokines IFN-gamma (P=0.0007) and TNF-alpha (P<0.0001) compared to the Hh 3B1-infected mice. The Hh 3B1-infected mice developed significantly higher total IgG, Th1-associated IgG2a and Th2-associated IgG1 responses to infection. These results indicate that H. hepaticus urease activity plays a crucial role in hepatic disease but is not required for cecal colonization by H. hepaticus.

Protection against Helicobacter pylori infection in mongolian gerbil by intragastric or intramuscular administration of H. pylori multicomponent vaccine

BACKGROUND

Development of Helicobacter pylori vaccine would be a new effective strategy for prevention and treatment of H. pylori infection. Recombinant H. pylori vaccine comprising a single subunit antigen can only induce immune response with limited protection efficiency. In this study, the protective effect of H. pylori multicomponent vaccines consisting of three recombinant subunit antigens was investigated using the Mongolian gerbil model.

MATERIALS AND METHODS

Mongolian gerbils were immunized with different formulations of three recombinant H. pylori antigens (UreB, HspA, and HpaA) with two different adjuvants (Al(OH)3, LT(R72DITH)) by intragastric (i.g.) or intramuscular (i.m.) routes. The protective effects of multicomponent vaccines were assessed after H. pylori challenge in different studies. The specific IgG antibodies in serum were monitored by ELISA, and the mRNA expressions of IL-4 and IFN-gamma in spleen tissue were detected by reverse transcribed polymerase chain reaction (RT-PCR).

RESULTS

The protective effect against H. pylori challenge in gerbils immunized with three recombinant antigens and LT(R72DITH) or Al(OH)3 was significantly higher than that in single- or double-antigen vaccine-immunized and control gerbils. Furthermore, the protective effect of the triple-antigen vaccine combined with the LT(R72DITH) adjuvant (average 86.3%) was significantly greater than that of vaccine combined with the Al(OH)3 adjuvant (average 53.4%). After the first immunization, the anti-UreB/HspA/HpaA serum IgG level in gerbils immunized with triple-antigen vaccine combined with Al(OH)3 was higher than that in gerbils immunized with the vaccine combined with LT(R72DITH). Splenic interferon (IFN)-gamma and interleukin (IL)-4 transcript levels were significantly increased in LT(R72DITH) vaccine-immunized gerbils as compared to the Al(OH)3 vaccine group. Moreover, splenic IL-4 mRNA levels were higher than IFN-gamma in gerbils immunized with triple-antigen vaccine with either LT(R72DITH) or Al(OH)3.

CONCLUSIONS

This study indicated that the recombinant multicomponent vaccine provided effective protection against H. pylori infection as compared to the single-antigen vaccine. This protective immunity would be closely associated with a predominant Th2-type response.

Culture of Helicobacter pylori and purification of antigen protein

Helicobacter pylori (H. pylori) live in the stomach of human. It is a kind of curve bacteria which can lead to chronic gastritis, peptic ulcer and gastric cancer. Usually, antibiotics are used to treat the patients, but they have a lot of side effects. Milk of milch cow immunized with H. pylori vaccine can prevent and treat the infection of H. pylori without side effects. During the production of immune milk, the basic work is to prepare vaccine. During the preparation of sub-unit vaccine, key is to isolate and purify the antigen protein. In this article, we discuss the culture of H. pylori (solid and liquid culture), the recombinant expression and purification of its antigen protein (urease, VacA, CagA and lipopolysaccharide).

The seroepidemiology of Helicobacter pylori infection in Australia

BACKGROUND

Infection with Helicobacter pylori is common worldwide and a significant cause of upper gastrointestinal disease. Prevalence of this infection varies in different population groups internationally. Because of the invasiveness of specimen collection for bacteriologic diagnosis and the expense of tests such as labeled urea breath tests, serology is the most feasible means of determining the population epidemiology of H. pylori. The aim of this study was to describe the seroepidemiology of H. pylori infection in Australia.

METHODS

H. pylori-specific ELISA for the presence of IgG antibodies was performed on a representative sample of 2413 sera from Australia in 2002, using validated serosurveillance methods.

RESULTS

The overall seroprevalence of H. pylori infection in Australia was 15.1% in 2002, with no statistical difference between genders. Seropositivity rates increased progressively with age, ranging between 4.0% in the 1-4-year-olds and 23.3% in the 50-59-year-olds.

CONCLUSIONS

The prevalence of infection with H. pylori in Australia was lower than rates reported in other developed countries, at 15.4%. This study provides important baseline measurements for future preventive measures including vaccine research and development. Further studies to determine subgroups at higher risk of infection may help target the more susceptible populations.

Antibiotic resistance of Helicobacter pylori

Helicobacter pylori are spiral-shaped, Gram-negative bacteria that colonize the stomachs of more than half the world's population. H. pylori colonization is the most common cause of chronic active gastritis and peptic ulcer disease, which directly related to gastric carcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. However, the efficacies of eradication therapies are not satisfying mainly because of bacterial resistance to antibiotics. This article makes a brief summary on the recent research related to the antibiotic resistance of H. pylori.

Oral vaccination with liposome-encapsulated recombinant fusion peptide of urease B epitope and cholera toxin B subunit affords prophylactic and therapeutic effects against H. pylori infection in BALB/c mice

A new fusion peptide CtUBE of cholera toxin B subunit and Helicobacter pylori urease B subunit epitope was expressed in Escherichia coli. With this fusion peptide, an oral liposome vaccine against H. pylori infection was prepared and evaluated in BALB/c mice. Based on the results of urease tests, quantitation of culturable bacteria colonies in mice stomachs and histological identification of gastritis, the mice were protected significantly after intragastric vaccination with this CtUBE liposome vaccine, which increased the content levels of specific anti-urease serum IgG and mucosal IgA for both prophylactic and therapeutic vaccination protocols. These results showed that the fusion peptide CtUBE retained immunogenicity and could be used as antigen in the development of an oral vaccine against H. pylori infection.

A vaccine against Helicobacter pylori: towards understanding the mechanism of protection

Helicobacter pylori infection remains a significant global public health problem. Vaccine development against this infection appears to be feasible but has not yet delivered its promise in clinical trials. Efforts to improve current vaccination strategies would greatly benefit from a better molecular understanding of the mechanism of protection. Here, we review recent developments in this field.