Vaccination as a method of preventing Helicobacter pylori-associated gastric cancer

DNA vaccine containing Flagellin A gene induces significant immune responses against Helicobacter pylori infection: An in vivo study

Objective(s):

Helicobacter pylori is one of the most prevalent human infectious agents that is directly involved in various upper digestive tract diseases. Although antibiotics-based therapy and proton pump inhibitors eradicate the bacteria mostly, their effectiveness has been declined recently due to emergence of antibiotic-resistant strains. Development of a DNA vaccine is a promising approach against bacterial pathogens. Genes encoding motility factors are promising immunogens to develop a DNA vaccine against H. pylori infection due to critical role of these genes in bacterial attachment and colonization within the gastric lumen. The present study aimed to synthesize a DNA vaccine construct based on the Flagellin A gene (flaA), the predominant flagellin subunit in H. pylori flagella.

Materials and Methods:

The coding sequence of flaA was amplified through PCR and sub-cloned in the pBudCE4.1 vector. The recombinant vector was introduced into the human dermal fibroblast cells, and its potency to express the flaA protein was analyzed using SDS-PAGE. The recombinant construct was intramuscularly (IM) injected into the mice, and the profiles of cytokines and immunoglobulins were measured using ELISA.

Results:

It has been found that flaA was successfully expressed in cells. Recombinant-vector also increased the serum levels of evaluated cytokines and immunoglobulins in mice.

Conclusion:

These findings showed that the pBudCE4.1-flaA construct was able to activate the immune responses. This study is the first step towards synthesis of recombinant-construct based on the flaA gene. Immunization with such construct may inhibit the H. pylori-associated infection; however, further experiments are urgent.

Dietary amelioration of Helicobacter infection

We review herein the basis for using dietary components to treat and/or prevent Helicobacter pylori infection, with emphasis on (a) work reported in the last decade, (b) dietary components for which there is mechanism-based plausibility, and (c) components for which clinical results on H pylori amelioration are available. There is evidence that a diet-based treatment may reduce the levels and/or the virulence of H pylori colonization without completely eradicating the organism in treated individuals. This concept was endorsed a decade ago by the participants in a small international consensus conference held in Honolulu, Hawaii, USA, and interest in such a diet-based approach has increased dramatically since then. This approach is attractive in terms of cost, treatment, tolerability, and cultural acceptability. This review, therefore, highlights specific foods, food components, and food products, grouped as follows: bee products (eg, honey and propolis); probiotics; dairy products; vegetables; fruits; oils; essential oils; and herbs, spices, and other plants. A discussion of the small number of clinical studies that are available is supplemented by supportive in vitro and animal studies. This very large body of in vitro and preclinical evidence must now be followed up with rationally designed, unambiguous human trials.

Immunogenicity characterization of the multi-epitope vaccine CTB-UE with chitosan-CpG as combination adjuvants against Helicobacter pylori

Urease is considered as an excellent vaccine candidate antigen against Helicobacter pylori (H. pylori) infection. Our previous study reported a novel multi-epitope vaccine CTB-UE which was composed of the mucosal adjuvant cholera toxin B subunit (CTB) and five cell epitopes from urease subunits. Murine experiments indicated that it could induce cellular and humoral immune responses intensively and attenuate H. pylori infection effectively in mice model. However, the body expression and lack of suitable adjuvant of this epitope vaccine restricted its application. In this study, new recombinant Escherichia coli strains was established to increase the solubility by fusing thioredoxin (Trx) and the combination adjuvants which composed of the chitosan and CpG were adopted to enhance the immunogenicity of CTB-UE for oral immunization. The experimental results indicated that the levels of IgG2a, IgG1 and IgA in the serum and the levels of sIgA in stomach, intestine and feces were significantly higher in the vaccinated group compared with the model control group. Additionally, chitosan-CpG combination adjuvants changed the ratio of IgG2a/IgG1 and conferred Th1/Th17-mediated protective immune responses. These results demonstrate that the oral vaccine with chitosan-CpG as combination adjuvants may be a promising vaccine candidate against H. pylori infection.

Immunological response to parenteral vaccination with recombinant hepatitis B virus surface antigen virus-like particles expressing Helicobacter pylori KatA epitopes in a murine H. pylori challenge model

Virus-like particles (VLPs) based on the small envelope protein of hepatitis B virus (HBsAg-S) are immunogenic at the B- and T-cell level. In this study, we inserted overlapping sequences encoding the carboxy terminus of the Helicobacter pylori katA gene product into HBsAg-S. The HBsAg-S-KatA fusion proteins were able to assemble into secretion-competent VLPs (VLP-KatA). The VLP-KatA proteins were able to induce KatA-specific antibodies in immunized mice. The mean total IgG antibody titers 41 days post-primary immunization with VLP-KatA (2.3 × 10(3)) were significantly greater (P < 0.05) than those observed for vaccination with VLP alone (5.2 × 10(2)). Measurement of IgG isotypes revealed responses to both IgG1 and IgG2a (mean titers, 9.0 × 10(4) and 2.6 × 10(4), respectively), with the IgG2a response to vaccination with VLP-KatA being significantly higher than that for mice immunized with KatA alone (P < 0.05). Following challenge of mice with H. pylori, a significantly reduced bacterial load in the gastric mucosa was observed (P < 0.05). This is the first report describing the use of VLPs as a delivery vehicle for H. pylori antigens.

HelicoVax: epitope-based therapeutic Helicobacter pylori vaccination in a mouse model

Helicobacter pylori is the leading cause of gastritis, peptic ulcer disease and gastric adenocarcinoma and lymphoma in humans. Due to the decreasing efficacy of anti-H. pylori antibiotic therapy in clinical practice, there is renewed interest in the development of anti-H. pylori vaccines. In this study an in silico-based approach was utilized to develop a multi-epitope DNA-prime/peptide-boost immunization strategy using informatics tools. The efficacy of this construct was then assessed as a therapeutic vaccine in a mouse model of gastric cancer induced by chronic H. pylori infection. The multi-epitope vaccine administered intranasally induced a broad immune response as determined by interferon-gamma production in ELISpot assays. This was associated with a significant reduction in H. pylori colonization compared with mice immunized with the same vaccine intramuscularly, given an empty plasmid, or given a whole H. pylori lysate intranasally as the immunogen. Total scores of gastric histological changes were not significantly different among the 4 experimental groups. These results suggest that further development of an epitope-based mucosal vaccine may be beneficial in eradicating H. pylori and reducing the burden of the associated gastric diseases in humans.

Treatment of Helicobacter pylori infection

Antibiotic resistance has resulted in unsatisfactory eradication results with dual and now triple therapy in many countries. Newer antibiotics and changes in dosing and duration of therapy may overcome resistant strains but may only provide limited improvement in eradication rates. Sequential therapy with amoxicillin (1 g twice a day) and a proton pump inhibitor (PPI) (twice a day) given for 5 days followed by a PPI plus clarithromycin (500 mg twice a day) and tinidazole (500 mg twice a day) for 5 days is now a first-line therapy for Helicobacter pylori in some countries. Standard triple therapy is effective in regions where clarithromycin resistance is low. Levofloxacin based triple therapy is an effective alternative to quadruple therapy in second-line treatment. Adjuvant therapy may reduce side-effects and improve compliance. Molecular and genomic research on H. pylori may result in the development of targeted antibiotic therapy; however, more research is required in this field. Further research in vaccination is also necessary before this can become an option in clinical practice.

Culture of Helicobacter pylori and purification of antigen protein

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

Genetic polymorphisms in mediators of inflammation and gastric precancerous lesions

Chronic inflammation induced by Helicobacter pylori is a key process in gastric carcinogenesis. We hypothesized that genetic polymorphisms in important mediators of H. pylori-induced inflammation may influence the risk of developing various grades of precancerous lesions. We studied the associations between single nucleotide polymorphisms (SNPs) in cyclooxygenase 1 and 2 (PTGS1 and PTGS2), inducible nitric oxide synthase (NOS2A), interferon gamma (IFNG) and its receptor (IFNGR1), and risk of gastric precancerous lesions in a Venezuelan population characterized by high rates of H. pylori infection. We found no association of precancerous lesions with SNPs in PTGS1 and in IFNG. A nonsynonymous SNP of NOS2A (Ser608Leu) and an SNP located in the promoter of IFNGR1 (C-56T) were associated with higher risk of atrophic gastritis [odds ratio (OR)=1.37, 95% confidence interval (CI)=1.01-1.86, and OR=1.49, 95% CI=1.01-2.19, respectively]. Two SNPs of PTGS2 were associated with risk of dysplasia (OR=1.60, 95% CI=1.01-2.54, and OR=0.66, 95% CI=0.43-0.99). We conclude that genetic variability in the genes we studied does not play a major role in the early stages of gastric carcinogenesis.

Mycoplasmal membrane protein p37 promotes malignant changes in mammalian cells

Evidence of Mycoplasma hyorhinis infection in human gastric cancer tissues has been found in previous work. In this study, we demonstrate that the expression of p37, a membrane lipoprotein of M. hyorhinis, in mammalian cells induces antisenescence, enhances clonogenicity in soft agar, and co-operates with human epidermal growth factor receptor-related 2 to inhibit cell adhesion. Conversely, truncated p37 protein, with the first 28 amino acids deleted from its N terminal, promotes cell senescence. Taken together, our findings suggest that p37 promotes malignant changes in mammalian cells. With the identification of this molecular component, which is responsible for mycoplasma malignancy-promoting activity, it is possible that a better understanding of the relationship between M. hyorhinis infection and human gastric cancers will lead to novel diagnostics and therapeutics.

Targeting Helicobacter pylori in gastric carcinogenesis

Gastric infection by Helicobacter pylori is an important risk factor for the development of gastric cancer. Recent research has identified both bacterial and host factors related to increased gastric cancer risk, including virulence-associated genes located in the cytotoxin-associated gene pathogenicity island and the vacuolating toxin A exotoxin, as well as polymorphisms in key cytokines and cytokine receptors that mediate the host's gastric inflammatory response. Early randomized trials indicate that eradicating H. pylori with antibiotics may prevent gastric cancer, although the effects so far have been modest, and are probably confined to individuals who had not developed preneoplastic lesions at the time of eradication. Targeting H. pylori to prevent gastric cancer may be best achieved through vaccination, better understanding of the molecular pathogenesis of H. pylori-associated carcinogenesis and additional chemopreventive strategies.

Genetic polymorphisms in anti-inflammatory cytokine signaling and the prevalence of gastric precancerous lesions in Venezuela

OBJECTIVES

The aim of the study was to assess the effects of genetic polymorphisms in anti-inflammatory mediators, i.e., IL10, IL4 and IL4R on the prevalence of gastric precancerous lesions and their interactions with other environmental factors.

METHODS

The study population consisted of 2,033 Venezuelan subjects known to have extremely high Helicobacter Pylori (HP) infection rates. The odds ratios (OR) and 95% confidence intervals (CI) associated with these polymorphisms were estimated by multinominal logistic regression models for gastric precursor lesions.

RESULTS

We found a 60% increase in risk of intestinal metaplasia (IM) and dysplasia combined (OR 1.62, 95% CI: 1.10-2.38) among the carriers of the IL10-1082 low activity allele. This increased risk was more pronounced for dysplasia than for IM. On the other hand, homozygotes with the low activity allele of the A398G polymorphism in the IL4R gene had a modest increase in risk of atrophic gastritis (OR = 1.52, 95% CI: 1.05-2.21), compared with homozygotes of the high activity allele. There were no statistically significant synergetic interactions between these polymorphisms and environmental risk factors (low fruit intake, high starchy vegetable intake and cigarette smoking) for these lesions.

CONCLUSION

While the results of the present study suggest roles of genetic variability in these anti-inflammatory mediators in different stages of gastric carcinogenesis, there is high likelihood that they were chance findings due to multiple comparisons.

Analysis of immune responses against H pylori in rabbits

AIM: To investigate the immunogenicity of H pylori proteins, to evaluate the production rate of anti H pylori IgG antibodies in relation to time and to demonstrate the fidelity of newly optimized in-house enzyme-linked immunosorbent assay (ELISA) technique as an alternative for H pylori infection assay.

METHODS: In the present study, 100 μg of formalin-fixed H pylori whole cell antigens was injected into an experimental animal (New Zealand white female rabbit) intramuscularly on d 0, 16, 27 and 36. The first two doses were injected with adjuvants. On d 0, a serum sample was collected from the rabbit before immunization and this pre-immunized serum was used as a negative control for the whole study. To evaluate the immunogenic responses of the injected antigen, serum samples were collected from the rabbit at regular intervals up to d 42. The sera were analyzed using in-house ELISA and Western blot techniques.

RESULTS: The production of anti H pylori IgG antibodies in the rabbit in response to the injected antigen increased almost exponentially up to d 14 and after that it was maintained at the same level until the last day (d 42). By analyzing the immune profiles of immunized sera, 11 proteins were identified to be immunogenic, among them 2 (approximately 100 kDa and 85 kDa) were most prominent.

CONCLUSION: Analysis of the immune responses against pathogenic microorganisms like H pylori is necessary for the development of various diagnostic and preventive approaches. The results of this experiment reveal that the formalin-fixed H pylori whole cell antigens injected into the rabbit are highly immunogenic. These prominent proteins (approximately 100 kDa and 85 kDa) might have higher immunogenic effects among humans infected with H pylori and some of these immunogenic proteins can be included in diagnostic approaches based on serology and also for vaccine formulation. The in-house ELISA is a promising alternative compared to invasive techniques.

Host-bacterial interaction in the development of gastric precancerous lesions in a high risk population for gastric cancer in Venezuela

Helicobacter pylori (HP) infection affects over 50% of the world's population. The prevalence is over 90% in populations at high risk for gastric cancer, but clinical outcomes of the infection are highly variable and thus host genetic factors have been suggested to play a role in its outcomes in addition to bacterial factors. In this study, we examined the effects of common functional genetic polymorphisms of several proinflammatory cytokines known to be overexpressed in HP-infected gastric mucosa on the risk of various stages of gastric premalignant lesions. The odds ratios (ORs) and 95% confidence intervals (CI) for atrophic gastritis, intestinal metaplasia and dysplasia were estimated by multinominal logistic regression analysis among 2,033 Venezuelan subjects. There was a significant effect of IL8 -251A allele on the prevalence of dysplasia (p = 0.021). The OR associated with the A-allele was 1.34 (95% CI: 0.82-2.18) for heterozygotes and 2.00 (95% CI: 1.13-3.56) for homozygotes, compared with the TT genotype. Furthermore, there was a statistically significant interaction between the number of A-alleles and HP cag A genotype (p = 0.009), suggesting that the A-allele increased the risk of dysplasia only when cag A was present. The OR for the AA compared with TT genotype was 3.22 (95% CI: 1.60-6.52) in this group. There were no associations with other proinflammatory cytokines studied, i.e., IL1 beta, IL6, monocyte chemoattractant protein 1 (MCP1) and TNF alpha, or with other stages of premalignant lesions. The present study provides important evidence suggesting host-bacterial interactions in the development of gastric precancerous lesions.