Immunization with attenuated Salmonella typhimurium producing catalase in protection against gastric Helicobacter pylori infection in mice

Protective immunity enhanced Salmonella vaccine vectors delivering Helicobacter pylori antigens reduce H. pylori stomach colonization in mice

Helicobacter pylori is a major cause of gastric mucosal inflammation, peptic ulcers, and gastric cancer. Emerging antimicrobial-resistant H. pylori has hampered the effective eradication of frequent chronic infections. Moreover, a safe vaccine is highly demanded due to the absence of effective vaccines against H. pylori. In this study, we employed a new innovative Protective Immunity Enhanced Salmonella Vaccine (PIESV) vector strain to deliver and express multiple H. pylori antigen genes. Immunization of mice with our vaccine delivering the HpaA, Hp-NAP, UreA and UreB antigens, provided sterile protection against H. pylori SS1 infection in 7 out of 10 tested mice. In comparison to the control groups that had received PBS or a PIESV carrying an empty vector, immunized mice exhibited specific and significant cellular recall responses and antigen-specific serum IgG1, IgG2c, total IgG and gastric IgA antibody titers. In conclusion, an improved S. Typhimurium-based live vaccine delivering four antigens shows promise as a safe and effective vaccine against H. pylori 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.

Serological response to Helicobacter pylori infection among Latin American populations with contrasting risks of gastric cancer

Gastric cancer is a rare outcome of chronic Helicobacter pylori infection. Serologic profiles may reveal bacterial, environmental and/or host factors associated with cancer risk. We therefore compared specific anti-H. pylori antibodies among populations with at least twofold differences in gastric cancer mortality from Mexico, Colombia and Chile. Our study included 1,776 adults (mean age 42 years) from three nationally representative surveys, equally divided between residents of high- and low-risk areas. Antibodies to 15 immunogenic H. pylori antigens were measured by fluorescent bead-based multiplex assays; results were summarized to identify overall H. pylori seropositivity. We used logistic regression to model associations between antibody seroreactivity and regional cancer risk (high vs. low), adjusting for country, age and sex. Both risk areas had similar H. pylori seroprevalence. Residents in high- and low-risk areas were seroreactive to a similar number of antigens (means 8.2 vs. 7.9, respectively; adjusted odds ratio, OR: 1.02, p = 0.05). Seroreactivities to Catalase and the known virulence proteins CagA and VacA were each significantly (p < 0.05) associated with residence in high-risk areas, but ORs were moderate (1.26, 1.42 and 1.41, respectively) and their discriminatory power was low (area under the curve < 0.6). The association of Catalase was independent from effects of either CagA or VacA. Sensitivity analyses for antibody associations restricted to H. pylori-seropositive individuals generally replicated significant associations. Our findings suggest that humoral responses to H. pylori are insufficient to distinguish high and low gastric cancer risk in Latin America. Factors determining population variation of gastric cancer burden remain to be identified.

Production of IFN-γ and IL-4 Against Intact Catalase and Constructed Catalase Epitopes of Helicobacter pylori From T-Cells

Background:

Helicobacter pylori infection is highly prevalent in the developing countries. It causes gastritis, peptic ulcer disease, and gastrocarcinoma. Treatment with drugs and antibiotics is problematic due to the following reasons: cost, resistance to antibiotics, prolonged treatment and using multiple drugs. Catalase is highly conserved among the Helicobacter species and is important to the survival of the organism. It is expressed in high amounts and is exposed to the surface of this bacterium; therefore it represents a suitable candidate vaccine antigen.

Objectives:

A suitable approach in H. pylori vaccinology is the administration of epitope based vaccines. Therefore the responses of T-cells (IFN-γ and IL-4 production) against the catalase of H. pylori were determined. Then the quality of the immune responses against intact catalase and three epitopes of catalase were compared.

Materials and Methods:

In this study, a composition of three epitopes of the H. pylori catalase was selected based on Propred software. The effect of catalase epitopes on T-cells were assayed and immune responses identified.

Results:

The results of IFN-γ, IL-4 production against antigens, epitopes, and recombinant catalase by T-cells were compared for better understanding of epitope efficiency.

Conclusions:

The current research demonstrated that epitope sequence stimulates cellular immune responses effectively. In addition, increased safety and potency as well as a reduction in time and cost were advantages of this method. Authors are going to use this sequence as a suitable vaccine candidate for further research on animal models and humans in future.

Identification and characterization of H-2d restricted CD4+ T cell epitopes on Lpp20 of Helicobacter pylori

Background

Previous investigation has demonstrated that CD4⁺ T cells play a crucial role in effective immunity against Helicobacter pylori (H.pylori) infection. It has been well proved that Lpp20 is one of major protective antigens that induce immune responses after H.pylori invades host. Therefore it is valuable to identify CD4⁺ T cell epitopes on Lpp20, which is uncharacterized.

Methods

Putative epitopes of H-2^d restricted CD4⁺ T cell on Lpp20 of H.pylori were predicted by the SYFPEITHI algorithm and then eight hypothetical epitope peptides were synthesized. After BALB/c mice were primed with recombinant Lpp20, splenic CD4⁺ T cells were isolated and stimulated with synthesized peptides to measure T cell proliferation and MHC restriction. Cytokine profile was determined by ELISA and real-time PCR. Two identified epitopes were used to immunize mice to investigate CD4⁺ T cell response by flow cytometry.

Results

Two of eight peptides were able to stimulate CD4⁺ T cell proliferation and were mapped to residues 83-97aa and 58-72aa on Lpp20 respectively. These two peptides additively stimulated Th1 cells to secrete IFN-γ. The percentage of CD4⁺ T cell from mice immunized with two identified epitopes respectively was higher than the control group.

Conclusion

The identification and characterization of two CD4⁺ T cell epitopes of Lpp20 helps understand the protective immunity of Lpp20 in H.pylori infection and design effective epitope vaccines against H.pylori.

What have we learned from brucellosis in the mouse model?

Brucellosis is a zoonosis caused by Brucella species. Brucellosis research in natural hosts is often precluded by practical, economical and ethical reasons and mice are widely used. However, mice are not natural Brucella hosts and the course of murine brucellosis depends on bacterial strain virulence, dose and inoculation route as well as breed, genetic background, age, sex and physiological statu of mice. Therefore, meaningful experiments require a definition of these variables. Brucella spleen replication profiles are highly reproducible and course in four phases: i), onset or spleen colonization (first 48 h); ii), acute phase, from the third day to the time when bacteria reach maximal numbers; iii), chronic steady phase, where bacterial numbers plateaus; and iv), chronic declining phase, during which brucellae are eliminated. This pattern displays clear physiopathological signs and is sensitive to small virulence variations, making possible to assess attenuation when fully virulent bacteria are used as controls. Similarly, immunity studies using mice with known defects are possible. Mutations affecting INF-γ, TLR9, Myd88, Tγδ and TNF-β favor Brucella replication; whereas IL-1β, IL-18, TLR4, TLR5, TLR2, NOD1, NOD2, GM-CSF, IL/17r, Rip2, TRIF, NK or Nramp1 deficiencies have no noticeable effects. Splenomegaly development is also useful: it correlates with IFN-γ and IL-12 levels and with Brucella strain virulence. The genetic background is also important: Brucella-resistant mice (C57BL) yield lower splenic bacterial replication and less splenomegaly than susceptible breeds. When inoculum is increased, a saturating dose above which bacterial numbers per organ do not augment, is reached. Unlike many gram-negative bacteria, lethal doses are large (≥ 108 bacteria/mouse) and normally higher than the saturating dose. Persistence is a useful virulence/attenuation index and is used in vaccine (Residual Virulence) quality control. Vaccine candidates are also often tested in mice by determining splenic Brucella numbers after challenging with appropriate virulent brucellae doses at precise post-vaccination times. Since most live or killed Brucella vaccines provide some protection in mice, controls immunized with reference vaccines (S19 or Rev1) are critical. Finally, mice have been successfully used to evaluate brucellosis therapies. It is concluded that, when used properly, the mouse is a valuable brucellosis model.

Construction and characterization of recombinant attenuated Salmonella typhimurium expressing the babA2/ureI fusion gene of Helicobacter pylori

AIM

This study aimed to construct a live attenuated Salmonella typhimurium strain harbouring the Helicobacter pylori babA2 and ureI fusion gene, and to evaluate its immunogenicity.

METHODS

The babA2 and ureI fusion gene were cloned on an asd+ vector pYA3342 and expressed in attenuated S. typhimurium strain x8501 (Δasd). The level of babA2 and ureI fusion protein expression in S. typhimurium x8501 was examined by RT-PCR and Western blot tests. Stability of the recombinant x8501 (pYA3342/babA2/ureI) was determined after incubation for five days in vitro.

RESULTS

The fusion gene, composed of 2860 base pairs, was inserted into the recombinant vector, as indicated by PCR amplification, endonuclease digestion and sequencing. Compared with the GenBank database, homologies of amino-acid sequences of the cloned babA2 and ureI were 100% and 97%, respectively. Recombinant fusion protein was recognized by commercial antibodies for whole-cell lysate of H. pylori. Furthermore, plasmids were able to stably reside in host bacteria.

CONCLUSION

A prokaryotic expression system, recombinant live attenuated S. typhimurium expressing the H. pylori babA2 and ureI fusion gene, was successfully constructed, and the expressed fusion protein showed satisfactory immunoreactivity, thus offering a new candidate for prophylactic and therapeutic vaccines against H. pylori.

Cell mediated immune responses through TLR4 prevents DMBA-induced mammary carcinogenesis in mice

Toll-like receptors (TLRs) activate signals that are critically involved in the initiation of adaptive immune responses and many tumorigenic chemicals have been associated with activation of those pathways. To determine the role of TLR-4 (TLR4) in mammary carcinogenesis, we subjected TLR4 deficient and wild type (WT) mice to oral gavage with carcinogenic polyaromatic hydrocarbon 7,12-dimethylbenz(a)anthracene (DMBA). TLR4 deficient mice developed more tumors relative to the WT mice. T cells of TLR4 deficient mice produced elevated levels of IL-17 and lower levels of IFN-γ relative to WT mice. IL-12 secreted by CD11c(+) cells was higher in WT mice, whereas greater amounts of IL-23 were produced by CD11c(+) cells from TLR4 deficient mice. Moreover, there was higher incidence of regulatory T cells in TLR4 deficient mice than WT mice. Similarly, various markers of angiogenesis [matrix metalloproteinases (MMP)-2 and MMP-9, CD31 and vascular endothelial growth factor] were highly expressed in tumors from TLR4 deficient mice than WT mice. The results of this study indicate that TLR4 plays an important role in the prevention of DMBA induced mouse mammary tumorigenesis and efforts to divert the cell-mediated immune response may, therefore, prove to be beneficial in the prevention of mammary tumors.

Local recall responses in the stomach involving reduced regulation and expanded help mediate vaccine-induced protection against Helicobacter pylori in mice

Helicobacter pylori is recognised as the chief cause of chronic gastritis, ulcers and gastric cancer in humans. With increased incidence of treatment failure and antibiotic resistance, development of prophylactic or therapeutic vaccination is a desirable alternative. Although the results of vaccination studies in animal models have been promising, studies in human volunteers have revealed problems such as 'post-immunisation gastritis' and comparatively poor responses to vaccine antigens. The focus of this study was to compare the gastric and systemic cellular immune responses induced by recombinant attenuated Salmonella Typhimurium-based vaccination in the C57BL/6 model of H. pylori infection. Analysis of lymphocyte populations in the gastric mucosa, blood, spleen, paragastric LN and MLN revealed that the effects of vaccination were largely confined to the parenchymal stomach rather than lymphoid organs. Vaccine-induced protection was correlated with an augmented local recall response in the gastric mucosa, with increased proportions of CD4(+) T cells, neutrophils and reduced proportions of CD4(+) Treg. CD4(+) T cells isolated from the stomachs of vaccinated mice proliferated ex vivo in response to H. pylori antigen, and secreted Th1 cytokines, particularly IFN-γ. This detailed analysis of local gastric immune responses provides insight into the mechanism of vaccine-induced protection.

Association of systemic oxidative stress with suppressed serum IgG to commensal oral biofilm and modulation by periodontal infection

To assess the impact of systemic oxidative stress on humoral immune responses, we examined the relation between levels of serum 8-isoprostane and serum IgG antibodies against 17 microorganisms in the commensal oral biofilm among the ARIC population of community-dwelling adults (n = 4,717). Bivariately, serum 8-isoprostane was associated with age, race/center, education, smoking, serum triglycerides, and the extent of periodontal disease severity. Total IgG antibody directed to the oral biofilm was significantly associated with race/center, hypertension, triglycerides, periodontal disease severity, plaque, and serum 8-isoprostane. In multivariate models, the highest quartile of increased 8-isoprostane displayed marked reductions (44%) in biofilm IgG antibody in contrast to small increases in total IgG antibody level for the highest quartiles of oral bacterial burden or periodontal disease severity (19 and 12%, respectively; p < 0.0001). Increased 8-isoprostane was associated with decreased total IgG antibody (p < 0.0001) in subjects with or without extensive periodontal disease and/or biofilm and with suppression of IgG responses across the entire biofilm composition. Increased systemic oxidative stress is associated with a generalized decrease of serum IgG antibody responses to the oral biofilm. Levels of oral microbial burden, periodontitis severity, and smoking are, by comparison, minor modifiers of serum IgG responses to the commensal oral biofilm.

Antibody-mediated protection against infection with Helicobacter pylori in a suckling mouse model of passive immunity

Studies of active immunization against Helicobacter pylori indicate that antibodies play a minor role in immunity. There is also evidence, however, that the translocation of antibodies in the stomach may be insufficient to achieve functional antibody levels in the gastric lumen. We have used a suckling mouse model of passive immunity to determine if perorally delivered antibodies can protect against infection with H. pylori. Female C57BL/6 mice were immunized parenterally with formalin-fixed cells of three clinical isolates of H. pylori (3HP) or the mouse-adapted H. pylori strain SS1 before mating. Their pups were challenged with the SS1 strain at 4 days of age and left to suckle before determination of bacterial loads 14 days later. Compared to age-matched controls, pups suckled by 3HP-vaccinated dams were significantly protected against infection (>95% reduction in median bacterial load; P<0.0001). Pups suckled by SS1-vaccinated dams were also significantly protected in terms of both median bacterial load (>99.5% reduction; P<0.0001) and the number of culture-negative pups (28% versus 2% for immune and nonimmune cohorts, respectively; P<0.0001). Similar results were obtained with pups suckled by dams immunized with a urease-deficient mutant of SS1. Fostering experiments demonstrated that protection was entirely attributable to suckling from an immunized dam, and antibody isotype analysis suggested that protection was mediated by the immunoglobulin G fraction of immune milk. Analysis of the bacterial loads in pups sampled before and after weaning confirmed that infection had been prevented in culture-negative animals. These data indicate that antibodies can prevent colonization by H. pylori and suppress the bacterial loads in animals that are colonized.

Oral administration of Lactococcus lactis expressing Helicobacter pylori Cag7-ct383 protein induces systemic anti-Cag7 immune response in mice

To express the 3′‐region (1152 bp) of the cag7 gene of Helicobacter pylori 51 strain, encoding the C‐terminal 383 amino acid (ct383 aa) region of Cag7 protein that is known to cover the needle region of T4SS, in a live delivery vehicle Lactococcus lactis, the cag7‐ct383 gene was amplified by PCR. DNA sequence analysis revealed that the amino acid sequence of Cag7‐ct383 of H. pylori 51 shared 98.4% and 97.4% identity with H. pylori 26695 and J99, respectively. Intramuscular injection of the GST‐Cag7‐ct383 fusion protein into a rat could raise the anti‐Cag7 antibody, indicating the immunogenicity of the Cag7‐ct383 protein. When the cag7‐ct383 gene was cloned in Escherichia coli–L. lactis shuttle vector (pMG36e) and transformed into L. lactis, the transformant could produce the Cag7‐ct383 protein, as evidenced by Western blot analysis. The Cag7‐ct383 protein level in the L. lactis transformant reached a maximum at the early stationary phase without extracellular secretion. The oral administration of the L. lactis transformant into mice generated anti‐Cag7 antibody in serum in five of five mice. These results suggest that L. lactis transformant expressing Cag7‐ct383 protein may be applicable as an oral vaccine to induce mucosal and systemic immunity to H. pylori.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Helicobacter hepaticus catalase shares surface-predicted epitopes with mammalian catalases

Helicobacter hepaticus colonizes the murine intestine and has been associated with hepatic inflammation and neoplasia in susceptible mouse strains. In this study, the catalase of an enterohepatic Helicobacter was characterized for the first time. H. hepaticus catalase is a highly conserved enzyme that may be important for bacterial survival in the mammalian intestine. Recombinant H. hepaticus catalase was expressed in Escherichia coli in order to verify its enzymic activity in vitro. H. hepaticus catalase comprises 478 amino acids with a highly conserved haem-ligand domain. Three conserved motifs (R-F-Y-D, RERIPER and VVHAKG) in the haem-ligand domain and three surface-predicted motifs were identified in H. hepaticus catalase and are shared among bacterial and mammalian catalases. H. hepaticus catalase is present in the cytoplasmic and periplasmic compartments. Mice infected with H. hepaticus demonstrated immune responses to murine and H. hepaticus catalase, suggesting that Helicobacter catalase contains conserved structural motifs and may contribute to autoimmune responses. Antibodies to H. hepaticus catalase recognized murine hepatocyte catalase in hepatic tissue from infected mice. Antibodies from sera of H. hepaticus-infected mice reacted with peptides comprising two conserved surface-predicted motifs in H. hepaticus catalase. Catalases are highly conserved enzymes in bacteria and mammals that may contribute to autoimmune responses in animals infected with catalase-producing pathogens.

Immunology of Helicobacter pylori: insights into the failure of the immune response and perspectives on vaccine studies

Helicobacter pylori infects the stomach of half of the human population worldwide and causes chronic active gastritis, which can lead to peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. The host immune response to the infection is ineffective, because the bacterium persists and the inflammation continues for decades. Bacterial activation of epithelial cells, dendritic cells, monocytes, macrophages, and neutrophils leads to a T helper cell 1 type of adaptive response, but this remains inadequate. The host inflammatory response has a key functional role in disrupting acid homeostasis, which impacts directly on the colonization patterns of H pylori and thus the extent of gastritis. Many potential mechanisms for the failure of the host response have been postulated, and these include apoptosis of epithelial cells and macrophages, inadequate effector functions of macrophages and dendritic cells, VacA inhibition of T-cell function, and suppressive effects of regulatory T cells. Because of the extent of the disease burden, many strategies for prophylactic or therapeutic vaccines have been investigated. The goal of enhancing the host's ability to generate protective immunity has met with some success in animal models, but the efficacy of potential vaccines in humans remains to be demonstrated. Aspects of H pylori immunopathogenesis are reviewed and perspectives on the failure of the host immune response are discussed. Understanding the mechanisms of immune evasion could lead to new opportunities for enhancing eradication and prevention of infection and associated disease.

Effectiveness of vaccinationwith recombinant HpaA fromHelicobacter pyloriis influenced by host genetic background

Several studies have explored the production and immunogenicity of HpaA as a potential protective antigen against Helicobacter pylori but little is known regarding its protective capabilities. We therefore evaluated the protective efficacy of recombinant HpaA (rHpaA) as a candidate vaccine antigen against H. pylori. To explore the impact of genetic diversity, inbred and outbred mice were prophylactically and therapeutically immunized with rHpaA adjuvanted with cholera toxin (CT). Prophylactic immunization induced a reduction in bacterial colonization in BALB/c and QS mice, but was ineffective in C57BL/6 mice, despite induction of antigen-specific antibodies. By contrast, therapeutic immunization was effective in all three strains of mice. Prophylactic immunization with CT-adjuvanted rHpaA was more effective when delivered via the nasal route than following intragastric delivery in BALB/c mice. However, HpaA-mediated protection was inferior to that induced by bacterial lysate. Hence, protective efficacy is inducible with vaccines containing HpaA, most relevantly shown in an outbred population of mice. The effectiveness of protection induced by HpaA antigen was influenced by host genetics and was less effective than lysate. HpaA therefore has potential for the development of effective immunization against H. pylori but this would probably entail the antigen to be one component of a multiantigenic vaccine.

Identification of H-2d restricted Th epitopes in Urease B subunit of Helicobacter pylori

CD4+ T cells play important roles in protection against Helicobacter pylori (H. pylori) infection. In order to better understand the immune responses of H. pylori infection and improve immune interventions against this pathogen, we identified the Th epitopes in UreB of H. pylori, an excellent vaccine candidate antigen. By using the RANKPEP prediction algorithm, we have identified and characterized three Th epitopes within the UreB antigen, which can be recognized by CD4+ T cells from BALB/c (H-2d) mice. They were U(546-561), U(229-244), and U(237-251). These epitopes have important value for studying the immune response of H. pylori infection and for designing effective vaccine against H. pylori.

Expression of Helicobacter pylori cag12 gene in Lactococcus lactis MG1363 and its oral administration to induce systemic anti-Cag12 immune response in mice

To develop an oral vaccine against Helicobacter pylori infection, we have expressed the H. pyloricag12 (HP0532) gene, encoding the outer membrane protein Cag12 (31 kDa), in a live delivery vehicle Lactococcus lactis. The cag12 gene was amplified by polymerase chain reaction (PCR) using the genomic DNA of H. pylori K51 isolated from Korean patients. DNA sequence analysis revealed that the cag12 gene of H. pylori K51 has 98.1 and 97.4% identity with individual cag12 genes of the H. pylori 26695 and J99, respectively. The GST–Cag12 fusion protein, produced using the Escherichia coli expression system, was used to raise a rat polyclonal anti-Cag12 antibody. The PCR-amplified cag12 gene of H. pylori K51 was cloned in the E. coli–L. lactis shuttle vector (pMG36e) and transformed into L. lactis. Western blot analysis demonstrated that the Cag12 protein was expressed in the L. lactis transformant, with a maximum level at the log phase without extracelluar secretion. The oral administration of the transformant into mice resulted in the generation of the anti-Cag12 antibody in serum in two out of five cases. These results suggest that the recombinant L. lactis, which expresses Cag12, may be applicable as an oral vaccine to induce protective immunity against H. pylori.

The role of type-specific antibodies in colonization and infection by Helicobacter pylori

PURPOSE OF REVIEW

Helicobacter pylori is a Gram-negative spiral bacterium that colonizes the stomach of humans, causing gastritis, peptic ulcer disease, or gastric cancer. H. pylori infection accounts for a high percentage of mortality and morbidity rates in developing as well as developed countries. H. pylori bacteria reside in the mucus layer covering the gastric epithelium, and therefore the type of protective measures that could confer resistance appear to be limited. Although H. pylori infection stimulates strong local and systemic specific IgA and IgG antibody production, the influence of antibodies on bacterial colonization and gastric inflammation is still controversial.

RECENT FINDINGS

Recent studies in experimental animal models have indicated a non-essential role of specific antibodies for host resistance against H. pylori infection. Recent data show that protection is mediated by T cells, CD4 T helper type 1 cells, in particular. Antibodies are not only dispensable for protection, but they impair both the elimination of bacteria and the development of gastritis. This effect appears to be IgA-dependent and is not a function of specific IgM or IgG antibodies.

SUMMARY

This review highlights the recent advances in our understanding of how antibodies may influence the development of gastric inflammation and bacterial colonization. Such information can significantly increase our basic knowledge of immune regulation and protection against H. pylori infection, but can also indicate new strategies for vaccine development.

Oral vaccination of BALB/c mice with Salmonella enterica serovar Typhimurium expressing Pseudomonas aeruginosa O antigen promotes increased survival in an acute fatal pneumonia model

Pseudomonas aeruginosa is a leading cause of nosocomial pneumonia. We compared the efficacies of oral and intraperitoneal (i.p.) vaccinations of BALB/c mice with attenuated Salmonella enterica serovar Typhimurium SL3261 expressing P. aeruginosa serogroup O11 O antigen to protect against P. aeruginosa infection in an acute fatal pneumonia model. Oral and i.p. vaccines elicited O11-specific serum immunoglobulin G (IgG) antibodies, but IgA was observed only after oral immunization. Challenge of orally vaccinated mice with an O11 strain (9882-80) at 6 and 12 times the 50% lethal dose showed increased survival in mice that received the vaccine compared to phosphate-buffered saline (PBS)- and vector-treated controls; no difference in survival was seen with a heterologous strain, 6294 (serogroup O6). In addition, significant protection against 9882-80 was not observed in i.p. vaccinated animals. Bronchoalveolar lavage fluid taken from immunized mice harbored O11-specific IgA and IgG in orally immunized mice but only modest levels of IgG in i.p. vaccinated mice. To correlate protection, opsonophagocytosis assays were performed with pooled sera from orally immunized animals. Efficient killing of five O11 clinical isolates was observed, while no killing was noted with 6294, indicating that the recombinant SL3261 oral vaccine induces an O11-specific reaction. We next determined the ability of orally vaccinated animals to clear bacteria from their lungs. Following P. aeruginosa challenge, the numbers of viable bacteria were significantly fewer in orally vaccinated animals than in PBS- and vector-treated controls. Our results suggest that oral immunization with recombinant SL3261 is efficacious in protection against pneumonia caused by P. aeruginosa.

Expression and immunocompetence of HspA-UreB fusion protein of Helicobacter pylori

AIM: To construct recombinant expression vector expressing HspA-UreB fusion protein of Helicobacter pylori (H. pylori), and to determine its immunoreactivity, in order to develop gene recombinant vaccine against H. pylori infection.

METHODS: The hspA and ureB genes were amplified by PCR from H. pylori MEL-HP27 isolated in Zhengzhou and cloned directionally into vector pNEB193. These two genes were restricted by using two corresponding restriction enzyme separately and cloned together into the fusion expression vector pET-30 (a), and the recombinant plasmid was then used to transform E.coli BL21 (DE3). The positive clones were identified by PCR and restriction enzyme digestion. The recombinant fusion protein HspA-UreB was induced to express from E.coli by IPTG and was analyzed by SDS-PAGE. The fusion protein was purified by use of Ni²⁺ affinity chromatography and then used to immunize mice. The immunogenecity and immunoreactivity of the fusion protein were analyzed by Western blot.

RESULTS: The hspA-ureB fusion gene was amplified from the recombinant fusion expression plasmid pET-HU27 (pET-HspA-UreB) by PCR, and also the hspA-ureB fusion gene fragment was produced from these plasmids after restriction enzyme digestion. SDS-PAGE and optical density scanning indicated that the fusion protein was expressed in the recombinant vaccine strain BL21 (pET-HU27) as a protein with 82.1 KDa of molecular weight that accounted for 21% of the total bacterial protein. The purity of fusion protein was 91%. Western blot analysis of the purified fusion protein confirmed that it could specifically be recognized by mouse serum.

CONCLUSION: A recombinant vaccine candidate strain expression fusion protein HspA-UreB of H. pylori is constructed and identified successfully, and purified fusion protein has strong immunoreactivity.

Helicobacter pylori outer membrane proteins in diagnosis of Helicobacter pylori infection

AIM: To examine the serological response of patient with various upper gastrointestinal diseases and Helicobacter pylori (H. pylori ) infection to H. pylori outer membrane proteins (OMP) with M_r18 000 and 26 000 acquired by gene recombinant technique, and to determine its diagnostic significance.

METHODS: The recombinant vectors encoding OMP of H. pylori with M_r18 000 and 26 000 identified by restriction enzyme or PCR were used to transform and express in BL21 (DE3) E. coli respectively. After purification with Ni²⁺-NTA agarose resin, the colloid gold kits were prepared with purified recombinant proteins to detect H. pylori infection and disease associated with H. pylori by immunity-marker technology. We selected 150 patients with H. pylori infection and digestive symptoms without previous treatment, including chronic superficial gastritis (n = 60), duodenal ulcer (n = 30), gastric ulcer (n = 30), and gastric cancer (n = 30) during one year. Simultaneously, 33 cases without digestive symptoms and H. pylori infection were used as controls. All sera were collected and the antibody responded to specific proteins of H. pylori was tested with the colloid gold test kit. Taking as reference a combination of standard diagnostic methods (¹³C urea breath test, cultivate) and the classic enzyme-linked immunosorbent assay (ELISA) serological tests was compared with the results of this technique, and the sensitivity, specificity and accuracy of the colloid gold test were evaluated.

RESULTS: After purification with Ni²⁺-NTA agarose resin, the purities of recombinant fusion proteins were all about 95%. The ELISA results showed that recombinant fusion proteins could be recognized by monoclonal antibody of anti-H. pylori with Mr18 000 and 26 000 respectively. The results detected using colloid gold kits were as follows: all patients sera infected with H. pylori showed response to recombinant protein with M_r 26 000 were 94.0%, while 95.0%, 96.7%, 96.7% and 90.0% of patients with H. pylori-infected chronic superficial gastritis, duodenal ulcer, gastric ulcer, and gastric cancer respectively, showed responses. Compared with the serum-based ELISA results in detecting H. pylori-infection, there was no significant difference with the colloid gold kits (P > 0.05). The sensitivity, specificity, and accuracy of the rapid test kit with Mr 26 000 protein were 94.0%, 97.0%, and 94.5%, respectively; To recombinant protein with M_r18 000, 52.0%, 40.0%, 40.0%, 53.3% and 86.7%, of patients with H. pylori-infected chronic superficial gastritis, duodenal ulcer, gastric ulcer, and gastric cancer respectively, showed responses. There were a significant difference (P < 0.05) in the detecting rates of H. pylori infection between gastric cancer (86.7%) and the other diseases (43.3%). The results showed the colloid gold kits with Mr26 000 proteins of H. pylori could be used as a conventional examination method, with similar sensitivity and specificity as other conventional examination method, and simultaneously a significant association was found between the serologic response to M_r 18 000 OMP antigen and malignant outcome of H. pylori infection.

CONCLUSION: The two colloid gold kits with M_r18 000 and 26 000 proteins of H. pylori, can be a useful tool for detecting H. pylori infection, as well as predicting H. pylori related gastrointestinal diseases, such as gastric malignancy and peptic ulcer.

Helicobacter pylori infection: anything new should we know?

Over the past year, 2003-4, there have been a number of studies consolidating previous work in relation to pathogenesis of disease, diagnosis and management of Helicobacter pylori. Studies into the pathogenesis of disease have identified the main adhesin of H. pylori as an important virulence marker and as a potential target for therapy. Molecular investigations of both the strain and host variations have identified the action of several of the virulence factors, e.g. cagA, vacA, on disrupting host cell signalling and the consequences in respect of the release of chemokines from the damaged gastric epithelium and the effect on apoptosis. Over the past year, there have been further diagnostic kits developed based on modifications of current technology. Two promising areas of research for diagnosis are the use of host/strain genome polymorphisms as a means of identifying high-risk patients who may develop severe disease and the use of proteomics to identify potential antigens of diagnostic (or therapeutic) use. The three main antibiotics that are used in first-line eradication regimens are clarithromycin, metronidazole and amoxycillin. Of these, metronidazole has the highest prevalence of resistance, followed by clarithromycin; amoxycillin resistance is only rarely reported. The decreasing success of current first-line therapy is the driving force for the development of new antibiotic combinations and a search for novel sources for chemotherapeutic agents and novel therapeutic targets.

Helicobacter pylori: current status and future prospects

Helicobacter pylori is a global pathogen that causes severe gastrointestinal diseases leading to a significant morbidity and mortality. There is an effective treatment for peptic ulcer disease, however, this is being compromised by an increase in the prevalence of antibiotic resistance. Although alternative rescue regimens have been advocated, the best strategy would be to prevent disease, especially in the case of gastric cancer for which there is still no treatment. One approach is to inhibit the first step in the pathogenic process - adhesion of the organism to the host tissue. Another and probably a better approach is vaccination, but clinical trials have so far been unsuccessful. There is still a large uncertainty in relation to how H. pylori causes disease. Knowledge from genomics, proteomics, and the relationship between polymorphism of the bacterium and the host, as well as the continuing investigation of the role played by important virulence factors in the outcome of the disease, will help both in understanding pathogenesis of disease and in the design of the best vaccine.