Enhancement of Helicobacter pylori outer inflammatory protein DNA vaccine efficacy by co-delivery of interleukin-2 and B subunit heat-labile toxin gene encoded plasmids

Infiltration to infection: key virulence players of Helicobacter pylori pathogenicity

PURPOSE

This study aims to comprehensively review the multifaceted factors underlying the successful colonization and infection process of Helicobacter pylori (H. pylori), a prominent Gram-negative pathogen in humans. The focus is on elucidating the functions, mechanisms, genetic regulation, and potential cross-interactions of these elements.

METHODS

Employing a literature review approach, this study examines the intricate interactions between H. pylori and its host. It delves into virulence factors like VacA, CagA, DupA, Urease, along with phase variable genes, such as babA, babC, hopZ, etc., giving insights about the bacterial perspective of the infection The association of these factors with the infection has also been added in the form of statistical data via Funnel and Forest plots, citing the potential of the virulence and also adding an aspect of geographical biasness to the virulence factors. The biochemical characteristics and clinical relevance of these factors and their effects on host cells are individually examined, both comprehensively and statistically.

RESULTS

H. pylori is a Gram-negative, spiral bacterium that successfully colonises the stomach of more than half of the world's population, causing peptic ulcers, gastric cancer, MALT lymphoma, and other gastro-duodenal disorders. The clinical outcomes of H. pylori infection are influenced by a complex interplay between virulence factors and phase variable genes produced by the infecting strain and the host genetic background. A meta-analysis of the prevalence of all the major virulence factors has also been appended.

CONCLUSION

This study illuminates the diverse elements contributing to H. pylori's colonization and infection. The interplay between virulence factors, phase variable genes, and host genetics determines the outcome of the infection. Despite biochemical insights into many factors, their comprehensive regulation remains an understudied area. By offering a panoramic view of these factors and their functions, this study enhances understanding of the bacterium's perspective, i.e. H. pylori's journey from infiltration to successful establishment within the host's stomach.

Advances in Helicobacter pylori vaccine research: From candidate antigens to adjuvants-A review

BACKGROUND

Helicobacter pylori is a Gram-negative, spiral-shaped bacterium that infects approximately 50% of the world's population and has been strongly associated with chronic gastritis, peptic ulcers, gastric mucosa-associated lymphoma, and gastric cancer. The elimination of H. pylori is currently considered one of the most effective strategies for the treatment of gastric-related diseases, so antibiotic therapy is the most commonly used regimen for the treatment of H. pylori infection. Although this therapy has some positive effects, antibiotic resistance has become another clinically prominent problem. Therefore, the development of a safe and efficient vaccine has become an important measure to prevent H. pylori infection.

METHODS

PubMed and ClinicalTrials.gov were systematically searched from January 1980 to March 2023 with search terms-H. pylori vaccine, adjuvants, immunization, pathogenesis, and H. pylori eradication in the title and/or abstract of literature. A total of 5182 documents were obtained. Based on the principles of academic reliability, authority, nearly publicated, and excluded the similar documents, finally, 75 documents were selected, organized, and analyzed.

RESULTS

Most of the candidate antigens used as H. pylori vaccines in these literatures are whole-cell antigens and virulence antigens such as UreB, VacA, CagA, and HspA, and the main types of vaccines for H. pylori are whole bacteria vaccines, vector vaccines, subunit vaccines, nucleic acid vaccines, epitope vaccines, etc. Some vaccines have shown good immune protection in animal trials; however, few vaccines show good in clinical trials. The only H. pylori vaccine passed phase 3 clinical trial is a recombinant subunit vaccine using Urease subunit B (UreB) as the vaccine antigen, and it shows good prophylactic effects. Meanwhile, the adjuvant system for vaccines against this bacterium has been developed considerably. In addition to the traditional mucosal adjuvants such as cholera toxin (CT) and E. coli heat labile enterotoxin (LT), there are also promising safer and more effective mucosal adjuvants. All these advances made safe and effective H. pylori vaccines come into service as early as possible.

CONCLUSIONS

This review briefly summarized the advances of H. pylori vaccines from two aspects, candidates of antigens and adjuvants, to provide references for the development of vaccine against this bacterium. We also present our prospects of exosomal vaccines in H. pylori vaccine research, in the hope of inspiring future researchers.

Microneedle-Mediated Transdermal Delivery of Genetic Materials, Stem Cells, and Secretome: An Update and Progression

Medical practitioners commonly use oral and parenteral dosage forms to administer drugs to patients. However, these forms have certain drawbacks, particularly concerning patients' comfort and compliance. Transdermal drug delivery presents a promising solution to address these issues. Nevertheless, the stratum corneum, as the outermost skin layer, can impede drug permeation, especially for macromolecules, genetic materials, stem cells, and secretome. Microneedles, a dosage form for transdermal delivery, offer an alternative approach, particularly for biopharmaceutical products. In this review, the authors will examine the latest research on microneedle formulations designed to deliver genetic materials, stem cells, and their derivatives. Numerous studies have explored different types of microneedles and evaluated their ability to deliver these products using preclinical models. Some of these investigations have compared microneedles with conventional dosage forms, demonstrating their significant potential for advancing the development of biotherapeutics in the future.

Combatting Helicobacter pylori with oral nanomedicines

Helicobacter pylori (H. pylori) infection is considered to be the main cause of most digestive diseases,such as chronic active gastritis, gastroduodenal ulcers, or even gastric cancer. Oral medication is a transformative approach to treat H. pylori-induced infections. However, unlike intravenous administration, orally administrated drugs have to overcome various barriers before reaching the infected sites, which significantly limits the therapeutic efficacy. These challenges may be addressed by emerging nanomedicine that is equipped with nanotechnology approaches to enable efficient and effective targeted delivery of drugs. Herein, in this review, we first discuss the conventional therapy for the eradication of H. pylori. Through the introduction of the critical barriers of oral administration, the benefits of nanomedicine are highlighted. Recently-published examples of nanocarriers for combating H. pylori in terms of design, preparation, and antimicrobial mechanisms are then presented, followed by our perspective on potential future research directions of oral nanomedicines.

Designing and development of epitope-based vaccines against Helicobacter pylori

Helicobacter pylori infection is the principal cause of serious diseases (e.g. gastric cancer and peptic ulcers). Antibiotic therapy is an inadequate strategy in H. pylori eradication because of which vaccination is an inevitable approach. Despite the presence of countless vaccine candidates, current vaccines in clinical trials have performed with poor efficacy which makes vaccination extremely challenging. Remarkable advancements in immunology and pathogenic biology have provided an appropriate opportunity to develop various epitope-based vaccines. The fusion of proper antigens involved in different aspects of H. pylori colonization and pathogenesis as well as peptide linkers and built-in adjuvants results in producing epitope-based vaccines with excellent therapeutic efficacy and negligible adverse effects. Difficulties of the in vitro culture of H. pylori, high genetic variation, and unfavourable immune responses against feeble epitopes in the complete antigen are major drawbacks of current vaccine strategies that epitope-based vaccines may overcome. Besides decreasing the biohazard risk, designing precise formulations, saving time and cost, and induction of maximum immunity with minimum adverse effects are the advantages of epitope-based vaccines. The present article is a comprehensive review of strategies for designing and developing epitope-based vaccines to provide insights into the innovative vaccination against H. pylori.

The Role of Helicobacter pylori Proinflammatory Outer Membrane Protein and Propolis in Immunomodulation on U937 Macrophage Cell Model

Background

Regarding the important role of proinflammatory outer membrane protein (OipA) in the pathogenesis of Helicobacter pylori infection and immunomodulatory activity of propolis, we aimed to evaluate the immunogenicity effect of a purified recombinant OipA protein and propolis in the induction of two cytokines, interferon-gamma (IFN-γ) and interleukin-4 (IL-4), in a macrophage cell model.

Materials and Methods

The recombinant protein used in the present study corresponding to the oipA expressing a 34-35 kDa protein. OipA protein was purified by Ni-NTA affinity chromatography. The purified OipA protein (2.5- 40 μg /mL) and the propolis ethanolic extract (5-40 μg/mL) were incubated with phorbol 12-myristate 13-acetate-treated human myelomonocytic cell line U937 cells. IL-4 and IFN-γ levels were measured after 48 hours of incubation using enzyme-linked immunosorbent assay.

Results

The amounts of IL-4 and IFN-γ were significantly increased. The optimum concentration of OipA for the secretion of IL-4 was 5 μg/ml (P<0.0001). At higher concentrations, the amount of IL-4 diminished until suppression at 40 μg/mL. The optimum concentration of propolis, resulting in the most significant increased secretion of both IL-4 and IFN-γ was 40 μg/mL (P=0.0001 and P=0.0004).

Conclusion

We found that an OipA concentration of 10 μg/mL was more effective for IFN-γ production; however, it was not effective for the high production of IL-4. Therefore, it is postulated that the OipA could mainly induce a Th1 response through the production of IFN-γ. We also observed propolis's capability to induce IFN-γ production; however, the effective concentration for this was the same as for IL-4. Therefore, as an adjuvant, proper concentration of propolis is required for OipA to give the optimum response.

Helicobacter pylori adhesins: HpaA a potential antigen in experimental vaccines for H. pylori

BACKGROUND

Helicobacter pylori is a gram-negative bacterium involved in many gastric pathologies such as ulcers and cancers. Although the treatment for this infection has existed for several years, the development of a vaccine is nevertheless necessary to reduce the severe forms of the disease. For more than three decades, many advances have been made particularly in the understanding of virulence factors as well as the pathogenesis of gastric diseases caused by H. pylori. Among these key virulence factors, specific antigens have been identified: Urease, Vacuolating cytotoxin A (VacA), Cytotoxin-associated gene A (CagA), Blood group antigen-binding adhesin (BabA), H. pylori adhesin A (HpaA), and others.

OBJECTIVES

This review will focus on H. pylori adhesins, in particular, on HpaA and on the current knowledge of H. pylori vaccines.

METHODS

All of the information included in this review was retrieved from published studies on H. pylori adhesins in H. pylori infections.

RESULTS

These proteins, used in their native or recombinant forms, induce protection against H. pylori in experimental animal models.

CONCLUSION

H. pylori adhesins are known to be promising candidate vaccines against H. pylori. Future research should be carried out on adhesins, in particular, on HpaA.

Co-expression of Interleukin-17A molecular adjuvant and prophylactic Helicobacter pylori genetic vaccine could cause sterile immunity in Treg suppressed mice

The increasing clinical significance of Helicobacter pylori (H. pylori) in human stomach cancer has led to global efforts to eradicate this pathogen. Recent studies have confirmed the importance of some cytokines such as Interleukin-18 (IL-18), Interleukin-8 (IL-8), Interleukin-17A (IL-17A) and Interleukin-22 (IL-22) in the pathogenesis of the so-called bacterium. This study was designed to compare the effects of Type 1T helper (Th1), Type 2T helper (Th2) cells, Regulatory T cells (Treg) and T helper 17 (Th17) modulatory effects on the efficacy of designed H. pylori vaccine by incorporating some molecular adjuvants in Treg competent and Treg suppressed groups. A bicistronic vector was used for simultaneous expression of codon-optimized Outer inflammatory protein a (OipA) gene and modified mice IL-18, IL-17A, IL-22 and Foxp3 (forkhead box P3) cytokines from four cassettes. Immunization of mice groups was performed using produced plasmids intradermally. Specific IgG1 and IgG2 and IgA antibody titers produced in mice were confirmed by enzyme-linked immunosorbent assay (ELISA) in sera and intestine obtained four weeks after the last immunization. After being stimulated with a mixture of both anti-CD28 mAb and H. pylori lysate, frequencies of single Interferon-Gamma (IFN-γ), single IL-17 and dual IFN-γ/IL-17-secreting T-cells were documented using dual-color FluoroSpot. The kinetics of Th1, Th2 and Th17 in the immunized animals was determined by relative quantification of IL-17A, IL-22, IFN-γ, IL-8, IL-2 and IL-4 specific mRNAs. Four weeks after bacterial challenge, quantitative colony count in the isolated and homogenized stomachs was utilized to assess the level of protective immunity among all groups. The results of immunologic assays showed that the highest cell-mediated immunity cytokines were produced in IL-17 receiving group in which the Treg responses were suppressed previously by the administration of the Foxp3 as an immunogen. In addition, potent clearance of Helicobacter pylori infection was seen in this group as well.

An oral alpha-galactosylceramide adjuvanted Helicobacter pylori vaccine induces protective IL-1R- and IL-17R-dependent Th1 responses

Helicobacter pylori causes chronic gastric infection that can lead to peptic ulcers and is an identified risk factor for gastric cancer development. Although much effort has been put into the development of a Helicobacter pylori vaccine over the last three decades, none has yet reached clinical application. Specific challenges pertaining to effective H. pylori vaccine development include the lack of proven vaccine-effective antigens and safe mucosal adjuvants to enhance local immune responses as well as the lack of accepted correlates of protection. Herein, we demonstrate that prophylactic intragastric immunisation with a whole-cell killed H. pylori antigen administered together with the non-toxic oral adjuvant α-galactosylceramide (α-GalCer) induced effective immune protection against H. pylori infection in mice, which was of similar magnitude as when using the “gold standard” cholera toxin as adjuvant. We further describe that this α-GalCer-adjuvanted vaccine formulation elicited strong intestinal and systemic Th1 responses as well as significant antigen-specific mucosal and systemic antibody responses. Finally, we report that the protective intestinal Th1 responses induced by α-GalCer are dependent on CD1d, IL-1R as well as IL-17R signalling. In summary, our results show that α-GalCer is a promising adjuvant for inclusion in an oral vaccine against H. pylori infection.

Infection by Helicobacter pylori is highly prevalent in humans and can lead to chronic inflammation and gastric cancer, but to date no effective vaccine has been approved for clinical use owing to the lack of appropriate antigens and of safe mucosal adjuvants that can produce protective and durable immunity to the bacterium. Sukanya Raghavan, Ed Lavelle and colleagues now show that prophylactic intragastric administration of an inactivated whole-cell H. pylori preparation, together with the oral adjuvant α-galactosylceramide, reduced H. pylori infection in mice by eliciting a protective mucosal and systemic T_H1 response. The immunisation triggered antigen-specific antibodies and interferon-γ that prevented effective colonisation of H. pylori after challenge in a process dependent on the CD1d, IL-1 receptor and IL-17 receptor pathways. The reported enhanced immune response to this orally adjuvanted vaccine formulation paves the way for further studies of its safety and efficacy.

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.

Designing an efficient multi-epitope oral vaccine against Helicobacter pylori using immunoinformatics and structural vaccinology approaches

Helicobacter pylori is the cunning bacterium that can live in the stomachs of many people without any symptoms, but gradually can lead to gastric cancer. Due to various obstacles, which are related to anti-H. pylori antibiotic therapy, recently developing an anti-H. pylori vaccine has attracted more attention. In this study, different immunoinformatics and computational vaccinology approaches were employed to design an efficient multi-epitope oral vaccine against H. pylori. Our multi-epitope vaccine is composed of heat labile enterotoxin IIc B (LT-IIc) that is used as a mucosal adjuvant to enhance vaccine immunogenicity for oral immunization, cartilage oligomeric matrix protein (COMP) to increase vaccine stability in acidic pH of gut, one experimentally protective antigen, OipA, and two hypothetical protective antigens, HP0487 and HP0906, and "CTGKSC" peptide motif that target epithelial microfold cells (M cells) to enhance vaccine uptake from the gut barrier. All the aforesaid segments were joined to each other by proper linkers. The vaccine construct was modeled, validated, and refined by different programs to achieve a high-quality 3D structure. The resulting high-quality model was applied for conformational B-cell epitopes selection and docking analyses with a toll-like receptor 2 (TLR2). Moreover, molecular dynamics studies demonstrated that the protein-TLR2 docked model was stable during simulation time. We believe that our vaccine candidate can induce mucosal sIgA and IgG antibodies, and Th1/Th2/Th17-mediated protective immunity that are crucial for eradicating H. pylori infection. In sum, the computational results suggest that our newly designed vaccine could serve as a promising anti-H. pylori vaccine candidate.

Bacterial toxin's DNA vaccine serves as a strategy for the treatment of cancer, infectious and autoimmune diseases

DNA vaccination -a third generation vaccine-is a modern approach to stimulate humoral and cellular responses against different diseases such as infectious diseases, cancer and autoimmunity. These vaccines are composed of a gene that encodes sequences of a desired protein under control of a proper (eukaryotic or viral) promoter. Immune response following DNA vaccination is influenced by the route and the dose of injection. In addition, antigen presentation following DNA administration has three different mechanisms including antigen presentation by transfected myocytes, transfection of professional antigen presenting cells (APCs) and cross priming. Recently, it has been shown that bacterial toxins and their components can stimulate and enhance immune responses in experimental models. A study demonstrated that DNA fusion vaccine encoding the first domain (DOM) of the Fragment C (FrC) of tetanus neurotoxin (CTN) coupled with tumor antigen sequences is highly immunogenic against colon carcinoma. DNA toxin vaccines against infectious and autoimmune diseases are less studied until now. All in all, this novel approach has shown encouraging results in animal models, but it has to go through adequate clinical trials to ensure its effectiveness in human. However, it has been proven that these vaccines are safe, multifaceted and simple and can be used widely in organisms which may be of advantage to public health in the near future. This paper outlines the mechanism of the action of DNA vaccines and their possible application for targeting infectious diseases, cancer and autoimmunity.

Recombinant Bacillus subtilis Spores Elicit Th1/Th17-Polarized Immune Response in a Murine Model of Helicobacter pylori Vaccination

Current progress in research on vaccines against Helicobacter pylori emphasizes the significance of eliciting the Th1/Th17-polarized immune response. Such polarization can be achieved by selection of appropriate antigen and adjuvant. In this study, we wanted to check the polarization of the immune response elicited by UreB protein of Helicobacter acinonychis delivered by recombinant Bacillus subtilis spores upon oral immunization. B. subtilis spores presenting fragment of UreB protein and able to express entire UreB in vegetative cells after germination were orally administered to mice along with aluminum hydroxide or recombinant spores presenting IL-2 as an adjuvant. The pattern of cytokines secreted by sensitized splenocytes assessed by the cytometric bead array clearly indicated polarization of the immune response toward both Th1 and Th17 in mice immunized with the use of above-mentioned adjuvants. Obtained result is promising regarding the usage of recombinant spores in formulations of vaccines against H. pylori and line up with the current state of research emphasizing the key role of appropriate adjuvants.

Vaccine against Helicobacter pylori: Inevitable approach

Over three decades have passed since the discovery of Helicobacter pylori (H. pylori), and yet many questions about its treatment remain unanswered. For example, there is no certainty regarding continued use of current antibiotic therapy against H. pylori. The bad news is that even combined regimens are also unable to eradicate bacterial colonization. The worst problem with H. pylori chemotherapy is that even if we identify the most successful regimen, it cannot eliminate the risk of re-infection. This problem is further complicated by the fact that clinicians have no information as to whether probiotics are useful or not. Moreover, to date, we have no large scale produced vaccine effective against H. pylori. Due to the relatively rapid and abundant dissemination of guidelines globally reported concerning management of gastric cancer prevention and therapeutic regimens, clinicians may choose a vaccine as better effective weapon against H. pylori. Therefore, a radical shift in adopted strategies is needed to guide ultimate decisions regarding H. pylori management. In light of failures in vaccine projects, we should identify better vaccine design targeting conserved/essential genes. The unique character and persistence of H. pylori pose obstacles to making an effective vaccine. Preferably, in developing countries, the best reasonable and logical approach is to recommend prophylactic H. pylori vaccine among children as an obligatory national program to limit primary colonization. Trying to produce a therapeutic vaccine would be postponed until later. In reality, we should not forget to prescribe narrow spectrum antibiotics. In the current review, I draw a route to define the best adopted strategy against this rogue bacterium.

Application of recombinant Helicobacter pylori outer inflammatory protein A peptide for diagnosis of high virulent Helicobacter pylori infection

AIM: To evaluate the feasibility of recombinant Helicobacter pylori (H. pylori) outer inflammatory protein A (OipA) peptide as a clinical diagnostic agent for high virulent H. pylori infection.

METHODS: Serum and gastric mucosa biopsy specimens were obtained from 285 patients who underwent gastroscopy. H. pylori strains were isolated from urease positive samples and some urease negative samples. Isolated strains were identified by microscopy, urease test and 16S rRNA PCR. OipA and cytotoxin-associated gene A (cagA) of the isolates were obtained by PCR and the oipA signal region was analyed after sequencing. OipA antibody in serum specimen was detected using purified recombinant OipA6 peptide, and CagA antibody was detected by indirect ELISA using a commercial kit. The results of oipA gene and OipA antibody as well as OipA antibody and CagA antibody were compared. The feasibility of OipA6 as a diagnostic agent for high virulent H. pylori infection was evaluated.

RESULTS: A total of 83 isolated H. pylori were obtained, of which 66 was positive for oipA signal region (signal region was on in 62, and undefined in 4), and 59 was positive for cagA. The sensitivity, specificity and consistency rate of recombination antigen OipA6 were 95.16%, 95.83% and 95.28%, respectively, which were all higher than those of CagA (77.97%, 87.50% and 80.72%).

CONCLUSION: Recombinant OipA peptide may be used as an antigen for detection of high virulent H. pylori infection.

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.

Immunology and vaccines and nanovaccines for Helicobacter pylori infection

Helicobacter pylori infection is very common worldwide and is an important cause of gastritis, peptic ulcer disease, gastric mucosa-associated lymphoid tissue lymphoma, and gastric adenocarcinoma. Since the eradication requires treatment with multidrug regimens, prevention of primary infection by a suitable vaccine is attractive. Developing vaccines on the spot when and where an infection is breaking out might be possible, thanks to engineered nanoparticles. In this review, the nature of the host immune response to H. pylori infection is considered. We explain recent candidate vaccines and prophylactic or therapeutic immunization strategies for use against H. pylori. We also describe identification of different types of immune responses that may be related to protection against H. pylori infection. Thus, it seems that there is still a strong need to clarify the main protective immune response against H. pylori.

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.

Outer membrane inflammatory protein A, a new virulence factor involved in the pathogenesis of Helicobacter pylori

Outer membrane proteins (OMPs) represent an important class of proteins that are observed in gram-negative bacteria, mitochondria and chloroplasts. These proteins play diverse biological roles in protein translocation, cell-cell communication and signal transduction. A variety of OMPs have been identified in the gastrointestinal pathogen Helicobacter pylori (H. pylori) since it was first isolated in 1983. Among these proteins, outer membrane inflammatory protein A (OipA), which is encoded by hopH and unique to this pathogen, is a differentially expressed outer membrane protein that has been confirmed to be directly linked to H. pylori colonization, as well as to the pathogenesis of H. pylori and disease outcome. In this review, we will describe the progress of recent studies on OipA, particularly those on the functions and biological significance of this unique protein.

Mucosal adjuvant activity of IL-2 presenting spores of bacillus subtilis in a murine model of Helicobacter pylori vaccination

The endospores of Bacillus subtilis are now widely used as a platform for presentation of heterologous proteins and due to their safety record and high resistance to harsh environmental conditions can be considered as potential vehicles for oral vaccination. In this research we show that recombinant B. subtilis spores presenting a fragment of the Helicobacter acinonychis UreB protein and expressing the ureB gene under vegetative promoter elicit a strong cellular immune response in orally immunized mice when co-administered with spores presenting IL-2. We show for the first time the successful application of two types of recombinant spores, one carrying an antigen and the other an adjuvant, in a single oral immunization.

Comparative genomics and immunoinformatics approach for the identification of vaccine candidates for enterohemorrhagic Escherichia coli O157:H7

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains are major human food-borne pathogens, responsible for bloody diarrhea and hemolytic-uremic syndrome worldwide. Thus far, there is no vaccine for humans against EHEC infections. In this study, a comparative genomics analysis was performed to identify EHEC-specific antigens useful as potential vaccines. The genes present in both EHEC EDL933 and Sakai strains but absent in nonpathogenic E. coli K-12 and HS strains were subjected to an in silico analysis to identify secreted or surface-expressed proteins. We obtained a total of 65 gene-encoding protein candidates, which were subjected to immunoinformatics analysis. Our criteria of selection aided in categorizing the candidates as high, medium, and low priority. Three members of each group were randomly selected and cloned into pVAX-1. Candidates were pooled accordingly to their priority group and tested for immunogenicity against EHEC O157:H7 using a murine model of gastrointestinal infection. The high-priority (HP) pool, containing genes encoding a Lom-like protein (pVAX-31), a putative pilin subunit (pVAX-12), and a fragment of the type III secretion structural protein EscC (pVAX-56.2), was able to induce the production of EHEC IgG and sIgA in sera and feces. HP candidate-immunized mice displayed elevated levels of Th2 cytokines and diminished cecum colonization after wild-type challenge. Individually tested HP vaccine candidates showed that pVAX-12 and pVAX-56.2 significantly induced Th2 cytokines and production of fecal EHEC sIgA, with pVAX-56.2 reducing EHEC cecum colonization. We describe here a bioinformatics approach able to identify novel vaccine candidates potentially useful for preventing EHEC O157:H7 infections.

The Role of Helicobacter pylori Outer Membrane Proteins in Adherence and Pathogenesis

Helicobacter pylori is one of the most successful human pathogens, which colonizes the mucus layer of the gastric epithelium of more than 50% of the world’s population. This curved, microaerophilic, Gram-negative bacterium induces a chronic active gastritis, often asymptomatic, in all infected individuals. In some cases, this gastritis evolves to more severe diseases such as peptic ulcer disease, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. H. pylori has developed a unique set of factors, actively supporting its successful survival and persistence in its natural hostile ecological niche, the human stomach, throughout the individual’s life, unless treated. In the human stomach, the vast majority of H. pylori cells are motile in the mucus layer lining, but a small percentage adheres to the epithelial cell surfaces. Adherence to the gastric epithelium is important for the ability of H. pylori to cause disease because this intimate attachment facilitates: (1) colonization and persistence, by preventing the bacteria from being eliminated from the stomach, by mucus turnover and gastric peristalsis; (2) evasion from the human immune system and (3) efficient delivery of proteins into the gastric cell, such as the CagA oncoprotein. Therefore, bacteria with better adherence properties colonize the host at higher densities. H. pylori is one of the most genetically diverse bacterial species known and is equipped with an extraordinarily large set of outer membrane proteins, whose role in the infection and persistence process will be discussed in this review, as well as the different receptor structures that have been so far described for mucosal adherence.

Developing mRNA-vaccine technologies

mRNA vaccines combine desirable immunological properties with an outstanding safety profile and the unmet flexibility of genetic vaccines. Based on in situ protein expression, mRNA vaccines are capable of inducing a balanced immune response comprising both cellular and humoral immunity while not subject to MHC haplotype restriction. In addition, mRNA is an intrinsically safe vector as it is a minimal and only transient carrier of information that does not interact with the genome. Because any protein can be expressed from mRNA without the need to adjust the production process, mRNA vaccines also offer maximum flexibility with respect to development. Taken together, mRNA presents a promising vector that may well become the basis of a game-changing vaccine technology platform. Here, we outline the current knowledge regarding different aspects that should be considered when developing an mRNA-based vaccine technology.

Inflammation, immunity, and vaccines for Helicobacter pylori infection

The immune response to Helicobacter pylori is a multifaceted group of mechanisms involving responses that are both protective and damaging to the host. The innate and the adaptive immune responses lead to damaging inflammatory responses, but these responses may fail, allowing for persistence of many infections. Thus, developing new therapeutics and effective vaccines against H. pylori has proven to be arduous. In this manuscript, we will examine the advances in knowledge made in the past year in understanding the host immune response to H. pylori and the progress toward developing a vaccine.

Therapeutic vaccination with Salmonella-delivered codon-optimized outer inflammatory protein DNA vaccine enhances protection in Helicobacter pylori infected mice

Vaccination had demonstrated as an alternative way to combat Helicobacter pylori challenge. In the present study, codon-optimized outer inflammatory protein gene (oipA) for Mus species codon usage, the inclusion of optimal Kozak sequence, and modified of GC content was applied to construct a novel DNA construct. The Salmonella-delivered wild type oipA construct (SL7207/poipA) and the Salmonella-delivered codon-optimized oipA construct (SL7207/poipA-opt) were prepared and their therapeutic efficacy was evaluated in H. pylori-infected mice. The codon-optimized oipA construct (poipA-opt) expressed almost six-fold higher protein than that of wild type construct (poipA) as normalized to the β-actin expression in AGS cells. Oral therapeutic immunization with SL7207/poipA-opt significantly eliminated H. pylori colonization in the stomach; and protection was related to a robust Th1/Th2 immune response. Therefore, our results suggested that fine therapeutic efficacy was related to sufficient expression of the antigen. It is supposed that codon-optimized oipA gene improves protein expression and consequently enhances the immunogenicity of DNA vaccine, which resulted in a significant reduction of bacterial loads in H. pylori infected mice. The Salmonella-delivered codon-optimized DNA construct could be a candidate vaccine against H. pylori for the clinical application.