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

Helicobacter pylori Outer Membrane Proteins and Virulence Factors: Potential Targets for Novel Therapies and Vaccines

Helicobacter pylori is a gastric oncopathogen that infects over half of the world's human population. It is a Gram-negative, microaerophilic, helix-shaped bacterium that is equipped with flagella, which provide high motility. Colonization of the stomach is asymptomatic in up to 90% of people but is a recognized risk factor for developing various gastric disorders such as gastric ulcers, gastric cancer and gastritis. Invasion of the human stomach occurs via numerous virulence factors such as CagA and VacA. Similarly, outer membrane proteins (OMPs) play an important role in H. pylori pathogenicity as a means to adapt to the epithelial environment and thereby facilitate infection. While some OMPs are porins, others are adhesins. The epithelial cell receptors SabA, BabA, AlpA, OipA, HopQ and HopZ have been extensively researched to evaluate their epidemiology, structure, role and genes. Moreover, numerous studies have been performed to seek to understand the complex relationship between these factors and gastric diseases. Associations exist between different H. pylori virulence factors, the co-expression of which appears to boost the pathogenicity of the bacterium. Improved knowledge of OMPs is a major step towards combatting this global disease. Here, we provide a current overview of different H. pylori OMPs and discuss their pathogenicity, epidemiology and correlation with various gastric diseases.

Recombinant outer membrane vesicles delivering eukaryotic expression plasmid of cytokines act as enhanced adjuvants against Helicobacter pylori infection in mice

The widespread prevalence of Helicobacter pylori (H. pylori) infection remains a great challenge to human health. The existing vaccines are not ideal for preventing H. pylori infection; thus, exploring highly effective adjuvants may improve the immunoprotective efficacy of H. pylori vaccines. In a previous study, we found that the outer membrane vesicles (OMVs), a type of nanoscale particle spontaneously produced by Gram-negative bacteria, could act as adjuvants to boost the immune responses to vaccine antigens. In this study, we explored the potential application of OMVs as delivery vectors for adjuvant development. We constructed recombinant OMVs containing eukaryotic expression plasmid of cytokines, including interleukin 17A or interferon-γ, and evaluated their function as adjuvants in combination with inactivated whole-cell vaccine (WCV) or UreB as vaccine antigens. Our results showed that recombinant OMVs as adjuvants could induce stronger humoral and mucosal immune responses in mice than wild-type H. pylori OMVs and the cholera toxin (CT) adjuvant. Additionally, the recombinant OMVs significantly promoted Th1/Th2/Th17-type immune responses. Furthermore, the recombinant OMV adjuvant induced more potent clearance of H. pylori than CT and wild-type OMVs. Our findings suggest that the recombinant OMVs coupled with cytokines may become potent adjuvants for the development of novel and effective vaccines against H. pylori infection.

Advancement of Engineered Bacteria for Orally Delivered Therapeutics

The use of bacteria and their biotic components as therapeutics has shown great potential in the treatment of diseases. Orally delivered bacteria improve patient compliance compared with injection-administered bacteria and are considered the preferred mode. However, due to the harsh gastrointestinal environment, the viability and therapeutic efficacy of orally delivered bacteria are significantly reduced in vivo. In recent years, with the rapid development of synthetic biology and nanotechnology, bacteria and biotic components have been engineered to achieve directed genetic reprogramming for construction and precise spatiotemporal control in the gastrointestinal tract, which can improve viability and therapeutic efficiency. Herein, a state-of-the-art review on the current progress of engineered bacterial systems for oral delivery is provided. The different types of bacterial and biotic components for oral administration are first summarized. The engineering strategies of these bacteria and biotic components and their treatment of diseases are next systematically summarized. Finally, the current challenges and prospects of these bacterial therapeutics are highlighted that will contribute to the development of next-generation orally delivered bacteriotherapy.

Perspectives from recent advances of Helicobacter pylori vaccines research

BACKGROUND

Helicobacter pylori (H. pylori) infection is the main factor leading to some gastric diseases. Currently, H. pylori infection is primarily treated with antibiotics. However, with the widespread application of antibiotics, H. pylori resistance to antibiotics has also gradually increased year by year. Vaccines may be an alternative solution to clear H. pylori.

AIMS

By reviewing the recent progress on H. pylori vaccines, we expected it to lead to more research efforts to accelerate breakthroughs in this field.

MATERIALS & METHODS

We searched the research on H. pylori vaccine in recent years through PubMed®, and then classified and summarized these studies.

RESULTS

The study of the pathogenic mechanism of H. pylori has led to the development of vaccines using some antigens, such as urease, catalase, and heat shock protein (Hsp). Based on these antigens, whole-cell, subunit, nucleic acid, vector, and H. pylori exosome vaccines have been tested.

DISCUSSION

At present, researchers have developed many types of vaccines, such as whole cell vaccines, subunit vaccines, vector vaccines, etc. However, although some of these vaccines induced protective immunity in mouse models, only a few were able to move into human trials. We propose that mRNA vaccine may play an important role in preventing or treating H. pylori infection. The current study shows that we have developed various types of vaccines based on the virulence factors of H. pylori. However, only a few vaccines have entered human clinical trials. In order to improve the efficacy of vaccines, it is necessary to enhance T-cell immunity.

CONCLUSION

We should fully understand the pathogenic mechanism of H. pylori and find its core antigen as a vaccine target.

Vaccination against Bacterial Infections: Challenges, Progress, and New Approaches with a Focus on Intracellular Bacteria

Many bacterial infections are major health problems worldwide, and treatment of many of these infectious diseases is becoming increasingly difficult due to the development of antibiotic resistance, which is a major threat. Prophylactic vaccines against these bacterial pathogens are urgently needed. This is also true for bacterial infections that are still neglected, even though they affect a large part of the world’s population, especially under poor hygienic conditions. One example is typhus, a life-threatening disease also known as “war plague” caused by Rickettsia prowazekii, which could potentially come back in a war situation such as the one in Ukraine. However, vaccination against bacterial infections is a challenge. In general, bacteria are much more complex organisms than viruses and as such are more difficult targets. Unlike comparatively simple viruses, bacteria possess a variety of antigens whose immunogenic potential is often unknown, and it is unclear which antigen can elicit a protective and long-lasting immune response. Several vaccines against extracellular bacteria have been developed in the past and are still used successfully today, e.g., vaccines against tetanus, pertussis, and diphtheria. However, while induction of antibody production is usually sufficient for protection against extracellular bacteria, vaccination against intracellular bacteria is much more difficult because effective defense against these pathogens requires T cell-mediated responses, particularly the activation of cytotoxic CD8+ T cells. These responses are usually not efficiently elicited by immunization with non-living whole cell antigens or subunit vaccines, so that other antigen delivery strategies are required. This review provides an overview of existing antibacterial vaccines and novel approaches to vaccination with a focus on immunization against intracellular bacteria.

Proteomic and Antibody Profiles Reveal Antigenic Composition and Signatures of Bacterial Ghost Vaccine of Brucella abortus A19

Brucellosis is an important zoonotic disease that causes great economic losses. Vaccine immunisation is the main strategy for the prevention and control of brucellosis. Although live attenuated vaccines play important roles in the prevention of this disease, they also have several limitations, such as residual virulence and difficulty in the differentiation of immunisation and infection. We developed and evaluated a new bacterial ghost vaccine of Brucella abortus A19 by a new double inactivation method. The results showed that the bacterial ghost vaccine of Brucella represents a more safe and efficient vaccine for brucellosis. We further characterised the antigenic components and signatures of the vaccine candidate A19BG. Here, we utilised a mass spectrometry-based label-free relative quantitative proteomics approach to investigate the global proteomics changes in A19BGs compared to its parental A19. The proteomic analysis identified 2014 proteins, 1116 of which were differentially expressed compared with those in A19. The common immunological proteins of OMPs (Bcsp31, Omp25, Omp10, Omp19, Omp28, and Omp2a), HSPs (DnaK, GroS, and GroL), and SodC were enriched in the proteome of A19BG. By protein micro array-based antibody profiling, significant differences were observed between A19BG and A19 immune response, and a number of signature immunogenic proteins were identified. Two of these proteins, the BMEII0032 and BMEI0892 proteins were significantly different (P < 0.01) in distinguishing between A19 and A19BG immune sera and were identified as differential diagnostic antigens for the A19BG vaccine candidate. In conclusion, using comparative proteomics and antibody profiling, protein components and signature antigens were identified for the ghost vaccine candidate A19BG, which are valuable for further developing the vaccine and its monitoring assays.

Bacterial Ghosts-Based Vaccine and Drug Delivery Systems

Bacterial ghosts (BGs) are empty bacterial envelopes of Gram-negative bacteria produced by controlled expressions of cloned gene E, forming a lysis tunnel structure within the envelope of the living bacteria. Globally, BGs have been used as vaccine delivery systems and vaccine adjuvants. There is an increasing interest in the development of novel delivery systems that are based on BGs for biomedical applications. Due to intact reservation of bacterial cell membranes, BGs have an inherent immunogenicity, which enables targeted drug delivery and controlled release. As carrier vehicles, BGs protect drugs from interference by external factors. In recent years, there has been an increasing interest in BG-based delivery systems against tumors, inflammation, and infection, among others. Herein, we reviewed the preparation methods for BGs, interactions between BGs and the host, and further highlighted research progress in BG development.

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.

Immune response and protective efficacy of two new adjuvants, Montanide™ ISA 763B VG and Montanide™ GEL02, administered with a Streptococcus agalactiae ghost vaccine in Nile tilapia (Oreochromis niloticus)

Streptococcus agalactiae is one of the most important pathogens infecting tilapia worldwide and causes meningoencephalitis, septicemia and high mortalities with considerable losses. Various types of vaccines have been developed against S. agalactiae infection, such as inactivated vaccines, live attenuated vaccines and subunit vaccines. Bacterial ghosts (BGs) are nonliving, empty cell envelopes and have been reported as novel vaccine candidates. Therefore, the main aims of this study were to develop an S. agalactiae ghost vaccine (SAGV) and to evaluate the immune response and protective effect of SAGV against S. agalactiae with two novel adjuvants, Montanide™ ISA 763B VG and Montanide™ GEL02. Nile tilapia, mean weight 50 g, were divided into four groups as follows; 1) fish injected with PBS as control, 2) fish injected with the SAGV alone; 3) fish injected with the SAGV+Montanide™ ISA 763B VG; and 4) fish injected with SAGV+Montanide™ GEL02. Following vaccination, innate immunity parameters including serum lysozyme, myeloperoxidase, catalase, and bactericidal activity were all significantly enhanced. Moreover, specific serum IgM antibodies were induced and reached their highest level 2-8 weeks post vaccination. Importantly, the relative percent survival of tilapia vaccinated against the SAGV formulated with both adjuvants was 80-93%. Furthermore, the transcription of immune-related genes (IgM, TCRβ, IL-1β, IL-8 and TNFα) were up-regulated in tilapia after vaccination, indicating that both cellular and humoral immune responses were induced by these adjuvanted vaccines. In summary, Montanide™ ISA 763B VG and Montanide™ GEL02 can enhance immunoprotection induced by the SAGV vaccine against streptococcosis, demonstrating that both have value as potential adjuvants of fish vaccines.

Controlled expression of lysis gene E by a mutant of the promoter pL of the thermo-inducible λcI857-pL system

AIMS

To identify a lambda promoter pL mutant that could extend the thermal stability of the thermo-inducible λcI857-pR/pL system and to evaluate the effects of the modified system for the controlled expression of lysis gene E during the production of bacterial ghosts (BGs).

METHODS AND RESULTS

The promoter pL mutant was identified by random mutagenesis and site-directed mutagenesis. The results showed that a T → 35C mutation in the pL promoter was responsible for the phenotype alteration. Under the same induction conditions, the lysis rates of the modified lytic system on Escherichia coli and Salmonella enteritidis were significantly lower than that of the control, while the lysis rates of Escherichia coli with the thermo-inducible lytic system were significantly higher than that of S. enteritidis with the corresponding plasmid (P < 0·05).

CONCLUSIONS

Increasing the heat stability of the thermo-inducible lytic systems decreased lysis efficiency during the production of BGs. There exist differences in the lysis efficiency of thermo-inducible lytic systems between different bacterial strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings enrich current knowledge about modifications to thermo-inducible systems and provide a reference for the application of these modified systems for the production of BGs and controlled gene expression in bacteria.

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.

Virulence of Helicobacter pylori outer membrane proteins: an updated review

Helicobacter pylori (H. pylori) infection is associated with some gastric diseases, such as gastritis, peptic ulcer, and gastric cancer. CagA and VacA are known virulence factors of H. pylori, which play a vital role in severe clinical outcomes. Additionally, the expression of outer membrane proteins (OMPs) helps H. pylori attach to gastric epithelial cells at the primary stage and increases the virulence of H. pylori. In this review, we have summarized the paralogs of H. pylori OMPs, their genomic loci, and the different receptors of OMPs identified so far. We focused on five OMPs, BabA (HopS), SabA (HopP), OipA (HopH), HopQ, and HopZ, and one family of OMPs: Hom. We highlight the coexpression of OMPs with other virulence factors and their relationship with clinical outcomes. In conclusion, OMPs are closely related to the pathogenic processes of adhesion, colonization, persistent infection, and severe clinical consequences. They are potential targets for the prevention and treatment of H. pylori–related diseases.

The development of ghost vaccines trials

INTRODUCTION

Bacterial ghosts are intact bacterial cell envelopes that are emptied of their content by gentle biological or chemical poring methods. Ghost techniques increase the safety of the killed vaccines, while maintaining their antigenicity due to mild preparation procedures. Moreover, ghost-platforms may express and/or carry several antigens or plasmid-DNA encoding for protein epitopes.

AREAS COVERED

In this review, the development in ghost-vaccine production over the last 30 years is classified and discussed. The different applications of ghost-vaccines, how they trigger the immune system, their advantages and limitations are displayed. The phage-mediated lysis, molecular manipulation of the lysis-genes, and the biotechnological production of ghosts are described. The trials are classified according to the pattern of lysis and to the type of bacteria. Further subdivision includes chronological ordered application of the ghost as alternative-killed vaccine, recombinant antigen platform, plasmid DNA carrier, adjuvants, and dendritic cell inducer. Particular trials for specific pathogens or from distinct research schools are gathered.

EXPERT OPINION

Ghosts are highly qualified to act as immune-presenting platforms that express and/or carry several recombinant and DNA vaccines, as well as, being efficient alternative-killed vaccines. The coming years will show more molecular advances to develop ghost-production and to express more antigens.

Bacteriosomes as a Promising Tool in Biomedical Applications: Immunotherapy and Drug Delivery

Bacteriosomes are a member of cell-derived vesicles that are proposed as promising tools in diagnosis, therapy, and drug delivery. These vesicles could be derived from a virus, bacterial cells, and animal cells. Biotechnology techniques were used in bioengineering of cell-derived vesicles in vitro, and in vivo. Bacterial vesicles such as bacterial cells, bacterial ghost, or bacteriosomes are vesicular structures derived from bacteria produced by manipulation of bacterial cells by chemical agents or gene-mediated lysis. Subsequently, bacterial vesicles (bacteriosomes) are non-living, non-denatured bacterial cell envelopes free of the cytoplasm and genetic materials. Gram-negative and Gram-positive bacteria are exploited in the production of bacteriosomes. Bacteriosomes have instinct organs, tissues, cells, as well as subcellular tropism. Moreover, bacteriosomes might be used as immunotherapy and/or drug delivery shuttles. They could act as cargoes for the delivery of small drugs, large therapeutics, and nanoparticles to the specific location. Furthermore, bacteriosomes have nature endosomal escaping ability, hence they could traffic different bio-membranes by endocytosis mechanisms. Therefore, bacterial-derived vesicles could be used in therapy and development of an innovative drug delivery systems. Consequently, utilizing bacteriosomes as drug cargoes enhances the delivery and efficacy of administered therapeutic agents. This review highlighted bacteriosomes in terms of source, engineering, characterization, applications, and limitations.

Construction of Lactobacillus casei ghosts by Holin-mediated inactivation and the potential as a safe and effective vehicle for the delivery of DNA vaccines

BACKGROUND

Bacterial ghosts (BGs) are empty bacterial cell envelopes generated by releasing the cellular contents. In this study, a phage infecting Lactobacillus casei ATCC 393 (L. casei 393) was isolated and designated Lcb. We aimed at using L. casei 393 as an antigen delivery system to express phage-derived holin for development of BGs.

RESULTS

A gene fragment encoding holin of Lcb (hocb) was amplified by polymerase chain reaction (PCR). We used L. casei 393 as an antigen delivery system to construct the recombinant strain pPG-2-hocb/L. casei 393. Then the recombinants were induced to express hocb. The immunoreactive band corresponding to hocb was observed by western-blotting, demonstrating the efficiency and specificity of hocb expression in recombinants. The measurements of optical density at 600 nm (OD₆₀₀₎ after induction showed that expression of hocb can be used to convert L. casei cells into BGs. TEM showed that the cytomembrane and cell walls of hocb expressing cells were partially disrupted, accompanied by the loss of cellular contents, whereas control cells did not show any morphological changes. SEM showed that lysis pores were distributed in the middle or at the poles of the cells. To examine where the plasmid DNA was associated, we analyzed the L. casei ghosts loading SYBR Green I labeled pCI-EGFP by confocal microscopy. The result demonstrated that the DNA interacted with the inside rather than with the outside surface of the BGs. To further analyze where the DNA were loaded, we stained BGs with MitoTracker Green FM and the loaded plasmids were detected using EGFP-specific Cy-3-labeled probes. Z-scan sections through the BGs revealed that pCI-EGFP (red) was located within the BGs (green), but not on the outside. Flow cytometry and qPCR showed that the DNA was loaded onto BGs effectively and stably.

CONCLUSIONS

Our study constructed L. casei BGs by a novel method, which may be a promising technology for promoting the further application of DNA vaccine, providing experimental data to aid the development of other Gram-positive BGs.

Immunization with a recombinant fusion protein protects mice against Helicobacter pylori infection

More than 50% of the world's population is infected with the bacterium Helicobacter pylori. If left untreated, infection with H. pylori can cause chronic gastritis and peptic ulcer disease, which may progress into gastric cancer. Owing to the limited efficacy of anti-H. pylori antibiotic therapy in clinical practice, the development of a protective vaccine to combat this pathogen has been a tempting goal for several years. In this study, a chimeric gene coding for the antigenic parts of H. pylori FliD, UreB, VacA, and CagL was generated and expressed in bacteria and the potential of the resulting fusion protein (rFUVL) to induce humoral and cellular immune responses and to provide protection against H. pylori infection was evaluated in mice. Three different immunization adjuvants were tested along with rFUVL: CpG oligodeoxynucleotides (CpG ODN), Addavax, and Cholera toxin subunit B. Compared to the control group that had received PBS, vaccinated mice showed significantly higher cellular recall responses and antigen-specific IgG2a, IgG1, and gastric IgA antibody titers. Importantly, rFUVL immunized mice exhibited a reduction of about three orders of magnitude in their stomach bacterial loads. Thus, adjuvanted rFUVL might be considered as a promising vaccine candidate for the control of H. pylori infection.

Bacterial components as naturally inspired nano-carriers for drug/gene delivery and immunization: Set the bugs to work?

Drug delivery is a rapidly growing area of research motivated by the nanotechnology revolution, the ideal of personalized medicine, and the desire to reduce the side effects of toxic anti-cancer drugs. Amongst a bewildering array of different nanostructures and nanocarriers, those examples that are fundamentally bio-inspired and derived from natural sources are particularly preferred. Delivery of vaccines is also an active area of research in this field. Bacterial cells and their components that have been used for drug delivery, include the crystalline cell-surface layer known as "S-layer", bacterial ghosts, bacterial outer membrane vesicles, and bacterial products or derivatives (e.g. spores, polymers, and magnetic nanoparticles). Considering the origin of these components from potentially pathogenic microorganisms, it is not surprising that they have been applied for vaccines and immunization. The present review critically summarizes their applications focusing on their advantages for delivery of drugs, genes, and vaccines.

A novel method to generate Salmonella Typhi Ty21a ghosts exploiting the λ phage holin-endolysin system

Human typhoid fever caused by Salmonella Typhi still poses a severe global disease burden in developing countries despite the availability of commercial vaccines. In this study, we constructed a non-living S. Typhi Ty21a vaccine candidate by employing a lambda (λ) phage-derived holin-endolysin system to efficiently construct bacterial ghosts. The lysis plasmid pJHL464 harbors an R lysis cassette that is stringently regulated by dual promoters containing cI857/λPR and ParaBAD/araC components. The plasmid was introduced into an asd gene-deleted S. Typhi Ty21a strain designated JOL1675. The in vitro expression of endolysin (~17.76 kDa) in the subsequent JOL1675 vaccine construct when grown under lysis inducible conditions was validated by immunoblotting. In scanning electron microscopy analysis, surface transmembrane tunnels and a collapsed body were visualized in the ghosts. Following 48 h of lysis, no viable JOL1675 cells remained, indicating that lysis of all cells was achieved. Subcutaneous immunizations of mice with the JOL1675 ghosts produced significantly increasing titers of serum IgG and vaginal wash secretory IgA antibodies against JOL1675 outer membrane proteins during the observational period. Further, serum collected at 6 weeks post-immunization of rabbits exhibited effective bactericidal activity against wild type S. Typhi in the presence of complement. These data showed that JOL1675 ghosts are highly immunogenic and elicit humoral and mucosal responses expected to correlate with protective immunity against S. typhi. Collectively, our findings support the conclusion that incorporating a λ phage holin-endolysin-mediated lysis construct into S. Typhi is an efficient strategy for developing a novel and safe non-living typhoid vaccine candidate.

Identification of fish source Vibrio alginolyticus and evaluation of its bacterial ghosts vaccine immune effects

Vibrio alginolyticus (V. alginolyticus) is a common pathogen for humans and marine aquatic animals. Vibriosis of marine aquatic animals, caused by V. alginolyticus, has become more prevalent globally in recent years. Hence, a safe and effective vaccine is urgently needed for the control of this disease. Here, the strain 16‐3 isolated from the large yellow croaker (Larimichthys crocea) suffered from canker was identified as V. alginolyticus based on morphological, biochemical, and 16S rDNA sequencing analysis. Then, recombinant temperature‐controlled lysis plasmid pBV220‐lysisE was electroporated into the strain 16‐3 to generate V. alginolyticus bacterial ghosts (VaBGs) by inducing lysis gene E expression, and the safety and immune effects of VaBGs were further investigated in mice and large yellow croaker. The results showed that VaBGs were as safe as formalin‐killed V. alginolyticus cells (FKC) to mice and fish. Compared with FKC and PBS groups, significant elevations of the serum agglutinating antibody titer, serum bactericidal activity, lymphocyte proliferative responses, and levels of four different cytokines (Th1 type: IL‐2, TNF‐α; Th2 type: IL‐4 and IL‐6) in serum were detected in the VaBGs group, indicating that a Th1/Th2‐mediated mixed immune response was elicited by the VaBGs. More importantly, after challenged with the parent strain 16‐3, VaBGs‐vaccinated mice and fish showed higher protection than FKC‐vaccinated mice, the relative percent of survival (RPS) being 60%, 66.7% and 40%, respectively. Taken together, this is the first demonstration that the newly constructed V. alginolyticus ghosts may be developed as a safe and effective vaccine against V. alginolyticus infection in aquaculture.

Immunologic properties and therapeutic efficacy of a multivalent epitope-based vaccine against four Helicobacter pylori adhesins (urease, Lpp20, HpaA, and CagL) in Mongolian gerbils

BACKGROUND

Therapeutic vaccination is a desirable alternative for controlling Helicobacter pylori (H. pylori) infection. Attachment to the gastric mucosa is the first step in establishing bacterial colonization, and adhesins, which are on the surface of H. pylori, play a pivotal role in binding to human gastric mucosa.

MATERIALS AND METHODS

In the present study, we constructed a multivalent epitope-based vaccine named CFAdE with seven carefully selected antigenic fragments from four H. pylori adhesins (urease, Lpp20, HpaA and CagL). The specificity, immunogenicity and ability to produce neutralizing antibodies of CFAdE were evaluated in BALB/c mice. After that, its therapeutic efficacy and protective immune mechanisms were explored in H. pylori-infected Mongolian gerbils.

RESULTS

The results indicated that CFAdE could induce comparatively high levels of specific antibodies against urease, Lpp20, HpaA and CagL. Additionally, oral therapeutic immunization with CFAdE plus polysaccharide adjuvant (PA) significantly decreased H. pylori colonization compared with oral immunization with urease plus PA, and the protection was correlated with IgG and sIgA antibody and antigen-specific CD4⁺ T cells.

CONCLUSIONS

This study indicated that the multivalent epitope-based vaccine, which targeted multiple adhesins in adherence of H. pylori to the gastric mucosa, is more effective than the univalent vaccine targeting urease only. This multivalent epitope-based vaccine may be a promising therapeutic candidate vaccine against H. pylori infection.

Oral Immunization with a Multivalent Epitope-Based Vaccine, Based on NAP, Urease, HSP60, and HpaA, Provides Therapeutic Effect on H. pylori Infection in Mongolian gerbils

Epitope-based vaccine is a promising strategy for therapeutic vaccination against Helicobacter pylori (H. pylori) infection. A multivalent subunit vaccine containing various antigens from H. pylori is superior to a univalent subunit vaccine. However, whether a multivalent epitope-based vaccine is superior to a univalent epitope-based vaccine in therapeutic vaccination against H. pylori, remains unclear. In this study, a multivalent epitope-based vaccine named CWAE against H. pylori urease, neutrophil-activating protein (NAP), heat shock protein 60 (HSP60) and H. pylori adhesin A (HpaA) was constructed based on mucosal adjuvant cholera toxin B subunit (CTB), Th1-type adjuvant NAP, multiple copies of selected B and Th cell epitopes (UreA_27–53, UreA_183–203, HpaA_132–141, and HSP60_189–203), and also the epitope-rich regions of urease B subunit (UreB_158–251 and UreB_321–385) predicted by bioinformatics. Immunological properties of CWAE vaccine were characterized in BALB/c mice model. Its therapeutic effect was evaluated in H. pylori-infected Mongolian gerbil model by comparing with a univalent epitope-based vaccine CTB-UE against H. pylori urease that was constructed in our previous studies. Both CWAE and CTB-UE could induce similar levels of specific antibodies against H. pylori urease, and had similar inhibition effect of H. pylori urease activity. However, only CWAE could induce high levels of specific antibodies to NAP, HSP60, HpaA, and also the synthetic peptides epitopes (UreB_158–172, UreB_181–195, UreB_211–225, UreB_349–363, HpaA_132–141, and HSP60_189–203). In addition, oral therapeutic immunization with CWAE significantly reduced the number of H. pylori colonies in the stomach of Mongolian gerbils, compared with oral immunization using CTB-UE or H. pylori urease. The protection of CWAE was associated with higher levels of mixed CD4⁺ T cell (Th cell) response, IgG, and secretory IgA (sIgA) antibodies to H. pylori. These results indic ate that a multivalent epitope-based vaccine including Th and B cell epitopes from various H. pylori antigens could be a promising candidate against H. pylori infection.

Protective immunity of grass carp induced by DNA vaccine encoding capsid protein gene (vp7) of grass carp reovirus using bacterial ghost as delivery vehicles

Grass carp reovirus (GCRV) is one of the most pathogenic aquareovirus and can cause lethal hemorrhagic disease in grass carp (Ctenopharyngodon idella). However, management of GCRV infection remains a challenge. Therefore, it is necessary to find effective means for the control of its infection. The uses of bacterial ghost (BG, non-living bacteria) as carriers for DNA delivery have received considerable attentions in veterinary and human vaccines studies. Nevertheless, there is still no report about intramuscular administration of bacterial ghost-based DNA vaccines in fish. In the current study, a novel vaccine based on Escherichia coli DH5α bacterial ghost (DH5α-BG), delivering a major capsid protein gene (vp7) of grass carp reovirus encoded DNA vaccine was developed to enhance the efficacy of a vp7 DNA vaccine against GCRV in grass carp. The grass carp was injected intramuscularly by different treatments -i) naked pcDNA-vp7 (containing plasmid 1, 2.5 and 5 μg, respectively), ii) DH5α-BG/pcDNA-vp7 (containing plasmid 1, 2.5 and 5 μg, respectively) and iii) naked pcDNA, DH5α-BG or phosphate buffered saline. The immune responses and disease resistance of grass carp were assessed in different groups, and results indicated that the antibody levels, serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, acid phosphatase (ACP) activity and alkaline phosphatase (AKP) activity and immune-related genes were significantly enhanced in fish immunized with DH5α-BG/pcDNA-vp7 vaccine (DNA dose ranged from 2.5 to 5 μg). In addition, the relative percentage survival were significantly enhanced in fish immunized with DH5α-BG/pcDNA-vp7 vaccine and the relative percentage survival reached to 90% in DH5α-BG/pcDNA-vp7 group than that of naked pcDNA-vp7 (42.22%) at the highest DNA dose (5 μg) after 14 days of post infection. Moreover, the level of pcDNA-vp7 plasmid was higher in DH5α-BG/pcDNA-vp7 groups than naked pcDNA-vp7 groups in muscle and kidneys tissues after 21 days. Overall, those results suggested that DH5α bacterial ghost based DNA vaccine might be used as a promising vaccine for aquatic animals to fight against GCRV infection.

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.

Effectiveness of F18+ Fimbrial Antigens Released by a Novel Autolyzed Salmonella Expression System as a Vaccine Candidate against Lethal F18+ STEC Infection

Porcine edema disease (ED) caused by Shiga toxin 2e producing Escherichia coli expressing F18ab⁺ fimbriae (F18ab⁺STEC) frequently occurs in post-weaned piglets, resulting in a significant economic loss in swine industries worldwide. In the present study, we proposed an efficient prevention scheme against ED in which the attenuated Salmonella Typhimurium inactivated by the E-mediated cell lysis to deliver target antigens, FedF and FedA, which function in fimbrial-mediated adhesion and as a major subunit of F18ab+fimbriae, respectively. The co-expression of FedA and FedF protein with outer membrane protein A signal peptide was confirmed in the resultant strains JOL1460 and JOL1464 by immunoblot analysis. Immunization with the candidate strains in mice led to the significant generation of immunoglobulin (Ig) G, specific to both antigens and secretory IgA specific to FedF (P < 0.05). The titers of IgG isotypes, IgG1 and IgG2a, used as markers for T-helpers (Th)-2 and Th-1lymphocytes, respectively, also significantly increased in the immunized group (P < 0.05). The increase in CD3⁺CD4⁺ T lymphocyte subpopulation and in vitro proliferative activity was observed in in vivo stimulated splenocytes, which indicated the immunostimulatory effect of the candidate strains. Moreover, the immunized mice were completely protected from a lethal challenge against wild-type F18⁺STEC whereas 28% of mice died in the non-immunized group. This study demonstrated that the inactivated Salmonella system could efficiently release FedF and FedA and induce robust immune responses specific to the target antigens, which is sufficient to protect the mice from the lethal challenge.

The enhanced immune responses induced by Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porB against Salmonella in mice

Human health has been seriously endangered by highly prevalent salmonellosis and multidrug-resistant Salmonella strains. Current vaccines suffer from variable immune-protective effects, so more effective ones are needed to control Salmonella infection : Bacterial ghosts have been produced by the expression of lysis gene E from bacteriophage PhiX174 and can be filled with considerable exogenous substances such as DNA or drugs as a novel platform. In this study, Salmonella enteritidis (SE) ghosts were developed and loaded with Neisseria gonorrhoeae porin B (porB) to construct a novel inactive vaccine. Our new studies show that SE ghosts loaded with porB displayed increased production of pro-inflammatory cytokines (IL-1β, IL-6, IL-10 and IL-12p70) in bone marrow-derived dendritic cells (BMDCs), and elicited significantly higher specific systemic and mucosal immune responses to Salmonella than SE ghosts alone. In addition, the novel porB-loaded ghosts conferred higher protective effects on virulent Salmonella challenge. For the first time, we demonstrate that N. gonorrhoeae porB, as a novel adjuvant, can increase the immunogenicity of SE ghosts. Our studies suggested that Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porin B might be a useful mucosal Salmonella vaccine candidate for practical use in the future.

Update on prevention and treatment of Helicobacter pylori infection

From the first isolation of Helicobacter pylori (H. pylori) from the gastric mucosa by Marshall and Warren in 1983, 33 years have passed. H. pylori has been found to be closely associated not only with chronic gastric diseases but also with multiple system diseases. Advances in research of H. pylori infection has led to a better understanding of the pathogenicity of H. pylori and the prevention and treatment of related disease. In 2015, Professor Zou's team developed oral recombinant H. pylori vaccine, which is promising in the prevention of H. pylori infection. Japan aims to reduce the risk of H. pylori infection in the whole population in 2014 to reduce the incidence of gastric cancer, which has caused widespread concern. H. pylori infection is a kind of infectious disease, and the infection rate in China is about 56%.Therefore, it is of great clinical importance to strengthen the research on bacteriology and pathogenesis of H. pylori, improve the prevention and treatment related diseases, and seek antibacterial regimens with better efficacy and lower drug resistance.

In Silico Design of a Chimeric Protein Containing Antigenic Fragments of Helicobacter pylori; A Bioinformatic Approach

Helicobacter pylori is a global health problem which has encouraged scientists to find new ways to diagnose, immunize and eradicate the H. pylori infection. In silico studies are a promising approach to design new chimeric antigen having the immunogenic potential of several antigens. In order to obtain such benefit in H. pylori vaccine study, a chimeric gene containing four fragments of FliD sequence (1-600 bp), UreB (327-334 bp),VacA (744-805 bp) and CagL(51-100 bp) which have a high density of B- and T-cell epitopes was designed. The secondary and tertiary structures of the chimeric protein and other properties such as stability, solubility and antigenicity were analyzed. The in silico results showed that after optimizing for the purpose of expression in Escherichia coli BL21, the solubility and antigenicity of the construct fragments were highly retained. Most regions of the chimeric protein were found to have a high antigenic propensity and surface accessibility. These results would be useful in animal model application and accounted for the development of an epitope-based vaccine against the H. pylori.

Inflammation, Immunity, and Vaccines for Helicobacter pylori Infection

During the last year, a variety of studies have been published that increases our understanding of the basic mechanisms of immunity and inflammation in Helicobacter pylori infection and progression to gastric cancer. Innate immune regulation and epithelial cell response were covered by several studies that contribute with new insights in the host response to H. pylori infection. Also, the adaptive immune response to H. pylori and particularly the role of IL-22 have been addressed in some studies. These advances may improve vaccine development where new strategies have been published. Two major studies analyzed H. pylori genomes of 39 worldwide strains and looked at the protein profiles. In addition, multi-epitope vaccines for therapeutic use have been investigated. Studies on different adjuvants and delivery systems have also given us new insights. This review presents articles from the last year that reveal detailed insight into immunity and regulation of inflammation, the contribution of immune cells to the development of gastric cancer, and understanding mechanisms of vaccine-induced protection.

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.