Why can't we make an effective vaccine against Helicobacter pylori?

Biomaterials for Helicobacter pylori therapy: therapeutic potential and future perspectives

Helicobacter pylori (H. pylori) is the main cause of gastric adenocarcinoma. However, the traditional antibiotic treatment of H. pylori is limited due to increased antibiotic resistance and low efficacy; low drug delivery efficiency and difficulties in eradicating H. pylori that is present intracellularly or in biofilms cause further setbacks. Biomaterials that can protect drugs against stomach acid, target lesions, control drug release, destroy biofilms, and exhibit unique antibacterial mechanisms and excellent biocompatibility have emerged as attractive tools for H. pylori eradication, particularly for drug-resistant strains. Herein, we review the virulence mechanisms, current drug treatments, and antibiotic resistance of H. pylori strains. Furthermore, recent advances in the development of biomaterials, including nanoparticles (such as lipid-based nanoparticles, polymeric nanoparticles, and inorganic nanoparticles), microspheres, and hydrogels, for effective and precise therapy of H. pylori and different types of therapeutic mechanisms, as well as future perspectives, have also been summarized.

Consumption of a Gelatin Supplemented with the Probiotic Strain Limosilactobacillus fermentum UCO-979C Prevents Helicobacter pylori Infection in a Young Adult Population Achieved

Helicobacter pylori is a bacterium associated with various gastrointestinal diseases of high worldwide prevalence. Since probiotics are an emerging alternative to managing infection by this pathogenic bacterium, the present work evaluated, in a randomized double-blind study controlled by a placebo, if consuming Limosilactobacillus fermentum UCO-979C prevents H. pylori infection in humans. Participants consumed either L. fermentum UCO-979C-supplemented gelatin (67 participants) or placebo-supplemented gelatin (64 participants) once a day, five days per week for 12 weeks. H. pylori infection in the participants was controlled before and after the intervention detecting H. pylori antigens in stools. Regarding H. pylori-infected participants before the study, 100% remained infected at the end of the study in the placebo group, while 96.7% of those receiving the probiotic remained infected after the intervention. Most importantly, of the non-infected participants, 34.2% became infected and 65.8% remained non-infected in the placebo group, while 2.7% became infected and 97.3% remained as non-infected individuals in the intervened group. Therefore, consuming the L. fermentum UCO-979C strain significantly reduced H. pylori infection, demonstrating a 92.6% efficacy in avoiding infection by this pathogen in non-infected individuals; thus, this probiotic is an excellent candidate to prevent H. pylori infections in non-infected individuals.

Vaccine development against Helicobacter pylori: from ideal antigens to the current landscape

Introduction: The interest of the world scientific community for an effective vaccine against Helicobacter pylori infection arises from its high prevalence and association with many diseases. Moreover, with an immunological response that is not always effective for the eradication of the bacteria and an increasing antibiotic resistance in the treatment of this infection, the search for a vaccine and new therapeutic modalities to control this infection is urgent.Areas covered: We bring an overview of the infection worldwide, discussing its prevalence, increasing resistance to antibiotics used in its therapy, in addition to the response of the immune system to the infection registered so far. Moreover, we address the most used antigens and their respective immunological responses expected or registered up to now. Finally, we address the trials and their partial results in development for such vaccines.Expert opinion: Although several studies for the development of an effective vaccine against this pathogen are taking place, many are still in the preclinical phase or even without updated information. In this sense, taking into account the high prevalence and association with important comorbidities, the interest of the pharmaceutical industry in developing an effective vaccine against this pathogen is questioned.

Recent chemical syntheses of bacteria related oligosaccharides using modern expeditious approaches

Apart from some essential and crucial roles in life processes carbohydrates also are involved in a few detrimental courses of action related to human health, like infections by pathogenic microbes, cancer metastasis, transplanted tissue rejection, etc. Regarding management of pathogenesis by microbes, keeping in mind of multi drug-resistant bacteria and epidemic or endemic incidents, preventive measure by vaccination is the best pathway as also recommended by the WHO; by vaccination, eradication of bacterial diseases is also possible. Although some valid vaccines based on attenuated bacterial cells or isolated pure polysaccharide-antigens or the corresponding conjugates thereof are available in the market for prevention of several bacterial diseases, but these are not devoid of some disadvantages also. In order to develop improved conjugate T-cell dependent vaccines oligosaccharides related to bacterial antigens are synthesized and converted to the corresponding carrier protein conjugates. Marketed Cuban Quimi-Hib is such a vaccine being used since 2004 to resist Haemophilus influenza b infections. During nearly the past two decades research is going on worldwide for improved synthesis of bacteria related oligosaccharides or polysaccharides towards development of such semisynthetic or synthetic glycoconjugate vaccines. The present dissertation is an endeavour to encompass the recent syntheses of several pathogenic bacterial oligosaccharides or polysaccharides, made during the past ten-eleven years with special reference to modern expeditious syntheses.

A Novel Design of Multi-epitope Vaccine Against Helicobacter pylori by Immunoinformatics Approach

Helicobacter pylori (H. pylori) is a gram-negative spiral bacterium that caused infections in half of the world’s population and had been identified as type I carcinogen by the World Health Organization. Compared with antibiotic treatment which could result in drug resistance, the vaccine therapy is becoming a promising immunotherapy option against H. pylori. Further, the multi-epitope vaccine could provoke a wider immune protection to control H. pylori infection. In this study, the in-silico immunogenicity calculations on 381 protein sequences of H. pylori were performed, and the immunogenicity of selected proteins with top-ranked score were tested. The B cell epitopes and T cell epitopes from three well performed proteins UreB, PLA1, and Omp6 were assembled into six constructs of multi-epitope vaccines with random orders. In order to select the optimal constructs, the stability of the vaccine structure and the exposure of B cell epitopes on the vaccine surface were evaluated based on structure prediction and solvent accessible surface area analysis. Finally Construct S1 was selected and molecular docking showed that it had the potential of binding TLR2, TLR4, and TLR9 to stimulate strong immune response. In particular, this study provides good suggestions for epitope assembly in the construction of multi-epitope vaccines and it may be helpful to control H. pylori infection in the future.

A Polypeptide of Tumor-Associated Antigen L6 with Intrinsic Adjuvant Activity Enhances Antitumor Immunity

Peptide vaccines are safe, and aim to elicit and expand tumor-specific immunity so as to eradicate tumors. However, achieving strong and long-lasting anti-tumor immunity with peptide vaccines for the antigen-specific treatment of cancer is challenging, in part because their efficacy depends on strong adjuvants or immunomodulators. We approached this problem by conjugating an epitope-based cancer vaccine with a lipidated sequence (an immunomodulator) to elicit a strong immune response. Lipidated and non-lipidated polyepitope proteins were generated that contained the universal T helper cell epitope (pan-DR), B cell epitopes, and the extended loop sequence of extracellular domain 2 of tumor-associated antigen L6 (TAL6). We show that the lipidated polyepitope cancer vaccine can activate bone marrow-derived dendritic cells, and trigger effective antigen-specific antibody and T helper cell responses, more effectively than the non-lipidated vaccine. Moreover, potent T cell immune responses were elicited in mice inoculated with the lipidated polyepitope cancer vaccine, providing protective antitumor immunity in mice bearing TAL6 tumors. Our study demonstrates that a lipidated polyepitope cancer vaccine could be employed to generate potent anti-tumor immune responses, including humoral and cellular immunity, which could be beneficial in the treatment of TAL6⁺ cancer.

Outer Membrane Vesicles of Helicobacter pylori 7.13 as Adjuvants Promote Protective Efficacy Against Helicobacter pylori Infection

Helicobacter pylori(H. pylori), a gram-negative bacterium in the human stomach with global prevalence, is relevant to chronic gastrointestinal diseases. Due to its increasing drug resistance and the low protective efficacy of some anti-H. pylori vaccines, it is necessary to find a suitable adjuvant to improve antigen efficiency. In our previous study, we determined that outer membrane vesicles (OMVs), a multicomponent secretion generated by gram-negative bacteria, of H. pylori were safe and could induce long-term and robust immune responses against H. pylori in mice. In this study, we employed two common vaccines, outer membrane proteins (OMPs) and whole cell vaccine (WCV) to assess the adjuvanticity of OMVs in mice. A standard adjuvant, cholera toxin (CT), was used as a control. Purified H. pylori OMVs used as adjuvants generated lasting anti-H. pylori resistance for 12 weeks. Additionally, both systematic and gastric mucosal immunity, as well as humoral immunity, of mice immunized with vaccine and OMVs combinations were significantly enhanced. Moreover, OMVs efficiently promoted Th1 immune response, but the response was skewed toward Th2 and Th17 immunity when compared with that induced by the CT adjuvant. Most importantly, OMVs as adjuvants enhanced the eradication of H. pylori. Thus, OMVs have potential applications as adjuvants in the development of a new generation of vaccines to treat H. pylori infection.

A lack of role for antibodies in regulating Helicobacter pylori colonization and associated gastritis

BACKGROUND

Helicobacter pylori occupy a unique niche, located within the mucus layer lining the stomach, and attached to the apical surface of the gastric epithelium. As such, antibodies would be expected to play a major role in regulating infection and/or pathogenesis. However, experiments using antibody-deficient mice to study gastric helicobacter infection have yielded inconsistent results, although some pointed toward antibodies increasing colonization levels and decreasing gastritis severity. The variability in these studies is possibly due to their use of nonmatched wild-type controls. This current study presents the first evaluation of the role of antibodies in H pylori infection by comparing antibody-deficient mice with matched wild-type siblings.

METHODS

Matched wild-type and antibody-deficient μMT mice were generated by heterozygous crossings. In two separate experiments, appropriately genotyped sibling littermates were infected with H pylori for 4 months and then sera and stomachs were collected.

RESULTS

There was no difference in H pylori colonization levels between infected μMT mice and sibling wild-type controls. Similarly, there was no significant difference in the severity of gastritis between these groups of mice, although there was a trend toward less severe gastritis in μMT mice which was supported by a significantly lower IFNγ (Th1) gastric cytokine response.

CONCLUSIONS

Comparing matched antibody-deficient and antibody-competent mice indicates that an antibody response does not influence H pylori colonization levels. Contrary to previous studies, these results suggest antibodies might have a minor pro-inflammatory effect by promoting gastric Th1 cytokines, although this did not translate to a significant effect on gastritis severity.

Oral immunization of mice with a multivalent therapeutic subunit vaccine protects against Helicobacter pylori infection

Helicobacter pylori is a human class I carcinogen and no effective prophylactic or therapeutic H. pylori vaccine has yet been marketed. H. pylori can escape the host immune response, but the precise immune protection mechanisms in humans remain unknown. In this study, we developed a multivalent, subunit H. pylori vaccine candidate by formulating three commonly used H. pylori antigens, neutrophil-activating protein (NAP), urease subunit A (UreA) and subunit B (UreB) with the mucosal adjuvant, a double-mutant heat-labile toxin (dmLT) from Escherichia coli, and evaluated its immunogenicity and therapeutic efficacy in a mouse model of H. pylori infection. We found that oral immunization of H. pylori-infected mice significantly reduced gastric bacterial colonization at both 2 and 8 weeks after immunization. The reduction in bacterial burdens was accompanied with significantly increased serum antigen-specific IgG responses and mucosal IgA responses. Moreover, oral immunization also induced Th1/Th17 immune responses, which may play a synergistic role with the specific antibodies in the elimination of H. pylori. Thus, our vaccine candidate appears able to overcome the immune evasion mechanism of H. pylori, restore the suppression of Th2 immune responses with the induction of a strong humoral immune response. These results lay the foundation for the development of an optimized oral therapeutic H. pylori vaccine with increased immunogenicity of UreA and UreB, as well as providing long-term immunity.

Eradication of Helicobacter pylori: the power of nanosized formulations

Helicobacter pylori is a pathogen that is considered to cause several gastric disorders such as chronic gastritis, peptic ulcer and even gastric carcinoma. The current therapeutic regimens mainly constitute of a combination of several antimicrobial agents and proton pump inhibitors. However, the prevalence of antibiotic resistance has been significantly lowering the cure rates over the years. Nanocarriers possess unique strengths in this regard owing to the fact that they can protect the drugs (such as antibiotics) from the harsh environment in the stomach, penetrate the mucosal barrier and deliver drugs to the desired site. In this review we summarized recent studies of different antibacterial agents orally delivered by nanosized carriers for the eradication of H. pylori.

Gastric Subserous Vaccination With Helicobacter pylori Vaccine: An Attempt to Establish Tissue-Resident CD4+ Memory T Cells and Induce Prolonged Protection

Tissue-resident memory T (Trm) cells are enriched at the sites of previous infection and required for enhanced protective immunity. However, the emergence of Trm cells and their roles in providing protection are unclear in the field of Helicobacter pylori (H. pylori) vaccinology. Here, our results suggest that conventional vaccine strategies are unable to establish a measurable antigen (Ag)-specific memory cell pool in stomach; in comparison, gastric subserous injection of mice with micro-dose of Alum-based H. pylori vaccine can induce a pool of local CD4+ Trm cells. Regional recruitment of Ag-specific CD4+ T cells depends on the engagement of Ag and adjuvant-induced inflammation. Prior subcutaneous vaccination enhanced this recruitment. A stable pool of Ag-specific CD4+ T cells can be detected for 240 days. Two weeks of FTY720 administration in immune mice suggests that these cells do not experience the recirculation. Immunohistochemistry results show that close to the vaccination site, abundant CD4+T cells locate on epithelial niches, independent of lymphocyte cluster. Paradigmatically, Ag-specific CD4+ T cells with a phenotype of CD69+CD103- are preferential on lymphocytes isolated from epithelium. Upon Helicobacter infection, CD4+ Trm cells orchestrate a swift recall response with the recruitment of circulating antigen-specific Th1/Th17 cells to trigger a tissue-wide pathogen clearance. This study investigates the vaccine-induced gastric CD4+ Trm cells in a mice model, and highlights the need for designing a vaccine strategy against H. pylori by establishing the protective CD4+ Trm cells.

Probiotic therapy in Helicobacter pylori infection: a potential strategy against a serious pathogen?

Helicobacter pylori is a highly prevalent human pathogen responsible for chronic inflammation of the gastric tissues, gastroduodenal ulcers, and cancer. The treatment includes a pair of antibiotics with a proton pump inhibitor PPI. Despite the presence of different treatments, the infection rate is still increasing both in developed and developing states. The challenge of treatment failure is greatly due to the resistance of H. pylori to antibiotics and its side effects. Probiotics potential to cure H. pylori infection is well-documented. Probiotics combined with conventional treatment regime appear to have great potential in eradicating H. pylori infection, therefore, provide an excellent alternative approach to manage H. pylori load and its threatening disease outcome. Notably, anti-H. pylori activity of probiotics is strain specific,therefore establishing standard guidelines regarding the dose and formulation of individual strain is inevitable. This review is focused on probiotic's antagonism against H. pylori summarizing their three main potential aspects: their efficiency (i) as an alternative to H. pylori eradication treatment, (ii) as an adjunct to H. pylori eradication treatment and (iii) as a vaccine delivery vehicle.

How far are we from vaccination against Helicobacter pylori infection?

INTRODUCTION

Helicobacter pylori infection results in chronic gastritis, peptic ulcer, or gastric cancer; therefore, eradication of this bacterium is essential. The strategy for developing effective vaccines against H. pylori entails immunization of mice with a combination of classical and recombinant H. pylori antigens, but this has proven to be onerous in all cases.

AREAS COVERED

We have reviewed literature databases in PubMed and Scopus using the key words H. pylori, vaccine, and vaccination and have conducted a systematic review of published clinical trials and animal model studies on vaccines against H. pylori and have tried to summarize why the vaccines are not effective or only partially effective.

EXPERT COMMENTARY

This is the perfect time to review vaccine development against H. pylori as, after several failed attempts, promising results were reported by Zeng et al. in 2015. Successful vaccine development requires knowledge of both the immune mechanisms active during natural infection by H. pylori, owing to the complicated host response against the pathogen, and the factors that allow the persistence of bacteria, such as genetic diversity of H. pylori. Moreover, various clinical trials are needed to prove vaccine efficacy.

Protection Against Helicobacter pylori Infection in BALB/c Mouse Model by Oral Administration of Multivalent Epitope-Based Vaccine of Cholera Toxin B Subunit-HUUC

Vaccination is an increasingly important alternative approach to control Helicobacter pylori infection, since H. pylori resistance to previously efficacious antibiotic regimens is increased, and H. pylori eradication treatment for upper gastrointestinal diseases is becoming less successful. Fortunately, an efficient oral monovalent H. pylori vaccine has been developed. However, compared with monovalent vaccines, multivalent vaccines have the potential to induce more effective and comprehensive protection against H. pylori infection. In this study, we designed and produced a multivalent epitope-based vaccine cholera toxin B subunit (CTB)-HUUC with the intramucosal adjuvant CTB and tandem copies of B-cell epitopes (HpaA132-141, UreA183-203, and UreB321-339) and T-cell epitopes (HpaA88-100, UreA27-53, UreB229-251, UreB317-329, UreB373-385, UreB438-452, UreB546-561, CagA149-164, and CagA196-217) from H. pylori adhesion A subunit (HpaA), urease A subunit (UreA), urease B subunit (UreB), and cytotoxin-associated antigen (CagA). Serum IgG, stomach, and intestine mucosal sIgA from mice after CTB-HUUC vaccination neutralized H. pylori urease activity in vitro. CTB-HUUC vaccination promoted H. pylori-specific lymphocyte responses and a mixed CD4⁺ T cell immune response as indicated by IFN-γ, interleukin-4, and interleukin-17 production in mice. Both oral prophylactic and therapeutic CTB-HUUC vaccinations reduced gastric urease activity and H. pylori infection and protected stomachs in mice. Taken together, CTB-HUUC is a promising potent and safe multivalent vaccine in controlling H. pylori infection in BALB/c mouse model.

Status of vaccine research and development for Helicobacter pylori

Gastric adenocarcinoma is globally the third leading cause of death due to malignancy, with the bulk of this disease burden being suffered by low and middle income countries (LMIC), especially in Asia. The majority of these cancers develop as a result of a chronic gastritis that arises in response to infection with the stomach-dwelling bacterium, Helicobacter pylori. A vaccine against this pathogen would therefore be a powerful tool for preventing gastric adenocarcinoma. However, notwithstanding a proof-of-concept that vaccination can protect children from acquisition of H. pylori infection, there are currently no advanced vaccine candidates with only a single vaccine in Phase I clinical trial. Further, the development of a vaccine against H. pylori is not a current strategic priority of major pharmaceutical companies despite the large global disease burden. Given the involvement of such companies is likely to be critical for late stage development, there is therefore a need for an increased appreciation of the burden of this disease in LMIC and more investment to reinvigorate research in H. pylori vaccine Research and Development.

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.

Helicobacter pylori overcomes natural immunity in repeated infections

Repeated experimental reinfection of two subjects indicates that Helicobacter pylori infection does not promote an immune response protective against future reinfection. Our results highlight the importance of preventing reinfection after eradication, through public health initiatives, and possibly treatment of family members. They indicate difficulties for vaccine development, especially therapeutic vaccines.

Immunization with Heat Shock Protein A and γ-Glutamyl Transpeptidase Induces Reduction on the Helicobacter pylori Colonization in Mice

The human gastric pathogen Helicobacter pylori (H. pylori) is a successful colonizer of the stomach. H. pylori infection strongly correlates with the development and progression of chronic gastritis, peptic ulcer disease, and gastric malignances. Vaccination is a promising strategy for preventing H. pylori infection. In this study, we evaluated the candidate antigens heat shock protein A (HspA) and H. pylori γ-glutamyl transpeptidase (GGT) for their effectiveness in development of subunit vaccines against H. pylori infection. rHspA, rGGT, and rHspA-GGT, a fusion protein based on HspA and GGT, were constructed and separately expressed in Escherichia coli and purified. Mice were then immunized intranasally with these proteins, with or without adjuvant. Immunized mice exhibited reduced bacterial colonization in stomach. The highest reduction in bacterial colonization was seen in mice immunized with the fusion protein rHspA-GGT when paired with the mucosal adjuvant LTB. Protection against H. pylori colonization was mediated by a strong systemic and localized humoral immune response, as well as a balanced Th1/Th2 cytokine response. In addition, immunofluorescence microscopy confirmed that rHspA-GGT specific rabbit antibodies were able to directly bind H. pylori in vitro. These results suggest antibodies are essential to the protective immunity associated with rHspA-GGT immunization. In summary, our results suggest HspA and GGT are promising vaccine candidates for protection against H. pylori infection.

Host Nonresponsiveness Does not Interfere With Vaccine-Mediated Protection Against Gastric Helicobacter Infection

BACKGROUND

Helicobacter pylori pathogenesis results from the inflammation induced by chronic infection. CBA mice are nonresponsive to gastric Helicobacter infection, providing a useful model for examining host regulation of Helicobacter-induced gastritis. We examined whether gastric Helicobacter nonresponsiveness impacts upon vaccine efficacy and whether immune-mediated protection could occur in the absence of inflammation.

METHODS

Mice were vaccinated prior to challenge with Helicobacter felis or H. pylori. Gastritis and H. felis colonization was evaluated histologically. H. pylori colonization was quantified by colony-forming assay.

RESULTS

Immunizations protected CBA mice against challenge with either H. felis or H. pylori. Protection against H. felis was marked by a loss of nonresponsiveness and development of an atrophic gastritis with mucus metaplasia. However, vaccine-induced protection against H. pylori was only associated with cell infiltration into the gastric mucosa.

CONCLUSIONS

Nonresponsiveness to gastric Helicobacter infection did not interfere with vaccination-induced protection. Vaccine-induced protective immunity against H. pylori was linked with the induction of cellular infiltration, but importantly not atrophic gastritis.

Protection against Helicobacter pylori infection in BALB/c mice by oral administration of multi-epitope vaccine of CTB-UreI-UreB

Chronic gastric infection by the Gram-negative bacterium Helicobacter pylori (H. pylori) is strongly associated with gastritis, gastric ulcer and the development of distal gastric carcinoma and gastric mucosal lymphoma in humans. Antibiotic treatment of H. pylori is becoming less effective because of increasing antibiotic resistance; other treatment approaches such as specifically targeted methods, etc. to destroy this organism would be beneficial. An epitope vaccine is a promising option for protection against H. pylori infection. In this study, a multi-epitope vaccine was constructed by linking cholera toxin B subunit (CTB), two antigenic fragments of H. pylori urease I subunit (UreI20-29, UreI98-107) and four antigenic fragments of H. pylori urease B subunit (UreB12-23, UreB229-251, UreB327-400, UreB515-561), resulting in the recombinant CTB-UreI-UreB (BIB). Its protective effect against H. pylori infection was evaluated in BALB/c mice. Significant protection against H. pylori challenge was achieved in BALB/c mice immunized with BIB (15/18, 83.3%), rIB plus rCTB (6/18, 33.3%) and rIB (2/18, 11.1%) separately, while no protective effect was found in the mice immunized with either adjuvant rCTB alone or PBS. The induction of significant protection against H. pylori is possibly mediated by specific serum IgA and mucosal sIgA antibodies, and a mixed Th1/Th2/Th17 cells response. This multi-epitope vaccine might be a promising vaccine candidate that helps to control H. pylori infection.

Helicobacter pylori vaccination: Is there a path to protection?

Helicobacter pylori (H. pylori) is a pathogenic, extracellular bacterium that colonizes the stomach in approximately 50% of the world population. It strongly interacts with the gastric epithelium and mostly causes asymptomatic gastritis. The colonization of H. pylori leads to ulcer development in around 20% of infected patients and may progress to gastric cancer or mucosa-associated lymphoid tissue lymphoma in 1%. Thus, H. pylori is the major cause of gastric cancer worldwide. It has been classified as a class I carcinogen by the World Health Organization. Since its discovery in the early eighties by Warren and Marshall, research has been focused on the investigation of H. pylori biology, host-pathogen interaction, prevention and treatment. Although H. pylori induces a strong humoral and local cellular immune response, the pathogen is not cleared and establishes a chronic infection after encounters in childhood. The ability to colonize the stomach is mediated by several virulence factors that change the host environment, promote adhesion to the epithelium, influence the gastric inflammation and induce immune evasion. H. pylori can be eradicated by antibiotic treatment in combination with a proton-pump inhibitor, but efficacy is decreasing. Current therapies are expensive, have side effects and contribute to increasing antibiotic resistance, underlining the need for novel therapeutics.

Eradication of Helicobacter pylori: Past, present and future

Helicobacter pylori is the major cause of chronic gastritis and peptic ulcers. Since the classification as a group 1 carcinogenic by International Agency for Research on Cancer, the importance of the complete H. pylori eradication has obtained a novel meaning. Hence, several studies have been made in order to deepen the knowledge in therapy strategies. However, the current therapy presents unsatisfactory eradication rates due to the lack of therapeutic compliance, antibiotic resistance, the degradation of antibiotics at gastric pH and their insufficient residence time in the stomach. Novel approaches have been made in order to overcome these limitations. The purpose of this review is to provide an overview about the current therapy and its limitations, while highlighting the possibility of using micro- and nanotechnology to develop gastric drug delivery systems, overcoming these difficulties in the future.

Attempts to enhance the eradication rate of Helicobacter pylori infection

Increasing rates of antimicrobial resistance to clarithromycin and metronidazole present challenges in maintaining optimal eradication rates. Knowledge of local antibiotic resistance and consumption pattern is important in selecting a reliable regimen. In addition, adverse effect profiles of therapeutic regimens are important and must be addressed to enhance compliance rates. Various methods of enhancing the eradication rates of Helicobacter pylori (H. pylori) have been investigated, including changing combinations or durations of established drugs, adding adjuvant drugs, or development of new molecules or agents. Bismuth-containing quadruple, sequential, concomitant, and levofloxacin-based triple therapies are replacing the long-standing standard of the triple regimen. Despite the encouraging results of these regimens, individualized approaches like treatment after antibiotics resistance test or CYP2C19 genotyping would be the mainstream of future therapy. Because scientific, economic, and technical problems make these advance therapies unfit for widespread use, future development for H. pylori therapy should be directed to overcome individualized antibiotic resistance. Although various novel regimens and additive agents have indicated favorable outcomes, more studies or validations are needed to become a mainstream H. pylori therapy.

Heat shock protein complex vaccination induces protection against Helicobacter pylori without exogenous adjuvant

BACKGROUND

The development of a vaccine against the human gastric pathogen Helicobacter pylori, the main causative agent of gastric adenocarcinoma, has been hampered by a number of issues, including the lack of a mucosal adjuvant for use in humans. Heat shock proteins (Hsp), highly conserved molecules expressed by both bacteria and mammalian species, possess a range of functions, including acting as chaperones for cellular proteins and the ability to activate innate immune receptors. Hsp complex (HspC) vaccines, containing Hsp derived from pathogenic bacteria, are immunostimulatory without addition of an exogenous adjuvant and can induce immunity against their chaperoned proteins. In this study we explored in mice the potential utility of a H. pylori HspC vaccine.

RESULTS

Vaccination with H. pylori HspC, by either the subcutaneous or respiratory mucosal route, induced a strong antibody response, elevated gastric cytokine levels and significant protection against subsequent live challenge with this pathogen. The level of protection induced by non-adjuvanted HspC vaccine was equivalent to that which resulted from vaccination with adjuvanted vaccines. While protection induced by immunisation with adjuvanted vaccines was associated with the development of a moderate to severe atrophic gastritis, that induced by H. pylori HspC only resulted in a mild inflammatory response, despite an increase in pro-inflammatory gastric cytokines. This reduced gastritis correlated with an increase in IL-10 and IL-13 levels in the gastric tissues of HspC vaccinated, H. pylori challenged mice.

CONCLUSIONS

H. pylori HspC vaccines have the potential to overcome some of the issues preventing the development of a human vaccine against this pathogen: HspC induced protective immunity against H. pylori without addition of an adjuvant and without the induction of a severe inflammatory response. However, complete protection was not obtained so further optimisation of this technology is needed if a human vaccine is to become a reality.

The role of glycans in immune evasion: the human fetoembryonic defence system hypothesis revisited

Emerging data suggest that mechanisms to evade the human immune system may be shared by the conceptus, tumour cells, persistent pathogens and viruses. It is therefore timely to revisit the human fetoembryonic defense system (Hu-FEDS) hypothesis that was proposed in two papers in the 1990s. The initial paper suggested that glycoconjugates expressed in the human reproductive system inhibited immune responses directed against gametes and the developing human by employing their carbohydrate sequences as functional groups. These glycoconjugates were proposed to block specific binding interactions and interact with lectins linked to signal transduction pathways that modulated immune cell functions. The second article suggested that aggressive tumour cells and persistent pathogens (HIV, H. pylori, schistosomes) either mimicked or acquired the same carbohydrate functional groups employed in this system to evade immune responses. This subterfuge enabled these pathogens and tumour cells to couple their survival to the human reproductive imperative. The Hu-FEDS model has been repeatedly tested since its inception. Data relevant to this model have also been obtained in other studies. Herein, the Hu-FEDS hypothesis is revisited in the context of these more recent findings. Far more supportive evidence for this model now exists than when it was first proposed, and many of the original predictions have been validated. This type of subterfuge by pathogens and tumour cells likely applies to all sexually reproducing metazoans that must protect their gametes from immune responses. Intervention in these pathological states will likely remain problematic until this system of immune evasion is fully understood and appreciated.

Serum antibody against Helicobacter pylori FlaA and risk of gastric cancer

BACKGROUND

Helicobacter pylori (H. pylori) infection is a major risk factor for gastric cancer (GC); however, only a minority of infected individuals develops GC. We aim to assess the association between serostatus of antibody against H. pylori flagellin A (FlaA) and risk of GC and to evaluate the value of serum FlaA antibody as a novel screening biomarker for GC risk.

METHODS

A hospital-based case-control study including 232 cases and 264 controls was conducted. Logistic regression was adopted to analyze the association between the serostatus of FlaA antibody and risk of GC. Serum FlaA antibody was measured by an enzyme-linked immunosorbent assay (ELISA). Receiver operating characteristic (ROC) curve was used to evaluate the screening efficacy and to identify a cutoff point of serum FlaA antibody level.

RESULTS

Helicobacter pylori infection was associated with an increased risk of GC (p = .007). A positive association between serum FlaA antibody and GC risk was observed in overall subjects and H. pylori-positive subjects (OR [95% CI]: 6.8 [4.3-10.7] and 6.9 [3.6-13.4], respectively; p < .001). The seropositivity of FlaA antibody was strongly related to GC risk in a dose-dependent manner (p for trend < .001). The optimal cutoff value (OD) was 0.1403, providing a sensitivity of 74.1% and a specificity of 64.4%. The area under the ROC curve (AUC) was 0.74 in overall subjects and 0.73 in H. pylori-positive subjects, respectively.

CONCLUSIONS

FlaA was an independent risk factor for H. pylori-related GC. Serum FlaA antibody may serve as a novel noninvasive biomarker for early detection of GC.

Vaccine-mediated protection against Helicobacter pylori is not associated with increased salivary cytokine or mucin expression

BACKGROUND

The development of an effective vaccine against Helicobacter pylori is impeded by the inability to reliably produce sterilizing immunity and our lack of knowledge regarding mechanisms of protective immunity against this pathogen. It has previously been described that salivary glands are essential for vaccine-mediated protection against H. pylori, but the mechanism responsible for this effect has not been identified. In this study we tested the hypothesis that vaccines reduce H. pylori colonization by inducing an immune-mediated change in salivary gland mucin secretion.

MATERIALS AND METHODS

Sublingual and submandibular salivary glands were removed from untreated mice, from mice infected with H. pylori and from mice vaccinated against H. pylori then challenged with live bacteria. Cytokine levels in these salivary glands were quantified by ELISA, and salivary mucins were quantified by real-time PCR. Salivary antibody responses were determined by Western blot.

RESULTS

Vaccine-mediated protection against H. pylori did not produce any evidence of a positive increase in either salivary cytokine or mucin levels. In fact, many cytokines were significantly reduced in the vaccinated/challenged mice, including IL-17A, IL-10, IL-1ß, as well as the mucin Muc10. These decreases were associated with an increase in total protein content within the salivary glands of vaccinated mice which appeared to be the result of increased IgA production. While this study showed that vaccination increased salivary IgA levels, previous studies have demonstrated that antibodies do not play a critical role in protection against H. pylori that is induced by current vaccine formulations and regimes.

CONCLUSIONS

The effector mechanism of protective immunity induced by vaccination of mice did not involve immune changes within the salivary glands, nor increased production of salivary mucins.

Subcomponent vaccine based on CTA1-DD adjuvant with incorporated UreB class II peptides stimulates protective Helicobacter pylori immunity

A mucosal vaccine against Helicobacter pylori infection could help prevent gastric cancers and peptic ulcers. While previous attempts to develop such a vaccine have largely failed because of the requirement for safe and effective adjuvants or large amounts of well defined antigens, we have taken a unique approach to combining our strong mucosal CTA1-DD adjuvant with selected peptides from urease B (UreB). The protective efficacy of the selected peptides together with cholera toxin (CT) was first confirmed. However, CT is a strong adjuvant that unfortunately is precluded from clinical use because of its toxicity. To circumvent this problem we have developed a derivative of CT, the CTA1-DD adjuvant, that has been found safe in non-human primates and equally effective compared to CT when used intranasally. We genetically fused the selected peptides into the CTA1-DD plasmid and found after intranasal immunizations of Balb/c mice using purified CTA1-DD with 3 copies of an H. pylori urease T cell epitope (CTA1-UreB3T-DD) that significant protection was stimulated against a live challenge infection. Protection was, however, weaker than with the gold standard, bacterial lysate+CT, but considering that we only used a single epitope in nanomolar amounts the results convey optimism. Protection was associated with enhanced Th1 and Th17 immunity, but immunizations in IL-17A-deficient mice revealed that IL-17 may not be essential for protection. Taken together, we have provided evidence for the rational design of an effective mucosal subcomponent vaccine against H. pylori infection based on well selected protective epitopes from relevant antigens incorporated into the CTA1-DD adjuvant platform.

Helicobacter pylori CagA: From Pathogenic Mechanisms to Its Use as an Anti-Cancer Vaccine

Helicobacter pylori colonizes the gastric mucosa of more than 50% of the human population, causing chronic inflammation, which however is largely asymptomatic. Nevertheless, H. pylori-infected subjects can develop chronic gastritis, peptic ulcer, gastric mucosa-associated lymphoid tissue lymphoma, and gastric cancer. Chronic exposure to the pathogen and its ability to induce epithelial to mesenchymal transition (EMT) through the injection of cytotoxin-associated gene A into gastric epithelial cells may be key triggers of carcinogenesis. By deregulating cell-cell and cell-matrix interactions as well as DNA methylation, histone modifications, expression of micro RNAs, and resistance to apoptosis, EMT can actively contribute to early stages of the cancer formation. Host response to the infection significantly contributes to disease development and the concomitance of particular genotypes of both pathogen and host may turn into the most severe outcomes. T regulatory cells (Treg) have been recently demonstrated to play an important role in H. pylori-related disease development and at the same time the Treg-induced tolerance has been proposed as a possible mechanism that leads to less severe disease. Efficacy of antibiotic therapies of H. pylori infection has significantly dropped. Unfortunately, no vaccine against H. pylori is currently licensed, and protective immunity mechanisms against H. pylori are only partially understood. In spite of promising results obtained in animal models of infection with a number of vaccine candidates, few clinical trials have been conducted so far and with no satisfactory outcomes. However, prophylactic vaccination may be the only means to efficiently prevent H. pylori-associated cancers.