The rOmp22-HpaA fusion protein confers protective immunity against helicobacter pylori in mice

Lipoprotein Processing and Sorting in Helicobacter pylori

Our current understanding of lipoprotein synthesis and localization in Gram-negative bacteria is based primarily on studies of Escherichia coli Newly synthesized E. coli prolipoproteins undergo posttranslational modifications catalyzed by three essential enzymes (Lgt, LspA, and Lnt). The mature lipoproteins are then sorted to the inner or outer membrane via the Lol system (LolABCDE). Recent studies suggested that this paradigm may not be universally applicable among different classes of proteobacteria. In this study, we conducted a systematic analysis of lipoprotein processing and sorting in Helicobacter pylori, a member of the Epsilonproteobacteria that colonizes the human stomach. We show that H. pylorilgt, lspA, and lnt homologs can complement conditionally lethal E. coli mutant strains in which expression of these genes is conditionally regulated. Mutagenesis studies and analyses of conditionally lethal H. pylori mutant strains indicate that lgt and lspA are essential for H. pylori growth but lnt is dispensable. H. pylorilolA and the single lolC (or lolE) homolog are also essential genes. We then explored the role of lipoproteins in H. pylori Cag type IV secretion system (Cag T4SS) activity. Comparative analysis of the putative VirB7 homolog CagT in wild-type and lnt mutant H. pylori strains indicates that CagT undergoes amino-terminal modifications consistent with lipidation, and we show that CagT lipidation is essential for CagT stability and Cag T4SS function. This work demonstrates that lipoprotein synthesis and localization in H. pylori diverge from the canonical pathways and that lipidation of a T4SS component is necessary for H. pylori Cag T4SS activity.IMPORTANCE Bacterial lipoproteins have diverse roles in multiple aspects of bacterial physiology, antimicrobial resistance, and pathogenesis. Dedicated pathways direct the posttranslational lipidation and localization of lipoproteins, but there is considerable variation in these pathways among the proteobacteria. In this study, we characterized the proteins responsible for lipoprotein synthesis and localization in Helicobacter pylori, a member of the Epsilonproteobacteria that contributes to stomach cancer pathogenesis. We also provide evidence suggesting that lipidation of CagT, a component of the H. pylori Cag T4SS, is required for delivery of the H. pylori CagA oncoprotein into human gastric cells. Overall, these results constitute the first systematic analysis of H. pylori lipoprotein production and localization pathways and reveal how these processes in H. pylori differ from corresponding pathways in model proteobacteria.

Oral immunization of BALB/c mice with recombinant Helicobacter pylori antigens and double mutant heat-labile toxin (dmLT) induces prophylactic protective immunity against H. pylori infection

Helicobacter pylori infection and associated diseases remain a major public health problem worldwide. Much effort has been made over the last several decades in vaccine development, but there is no licensed vaccine on the market. We have previously reported that oral immunization with H. pylori lysates and double mutant heat-labile toxin (dmLT) affords prophylactic protection against H. pylori infection in mice. In the present study, we investigated the effects of oral immunization with recombinant H. pylori protein antigens (NAP/UreA/UreB) and dmLT on H. pylori challenge in BALB/c mice. We found that oral immunization with candidate antigens and dmLT significantly reduced the gastric colonization of H. pylori 6 weeks after challenge, as compared to unimmunized mice. Moreover, the subunit vaccine appeared to provide a better protection than the bacterial lysate vaccine. The immunized mice showed enhanced antigen-specific lymphocyte proliferation, and serum IgG and mucosal IgA responses. Furthermore, the immunization increased the proportion of CD4⁺ IL-17+ lymphocytes in spleen and mesenteric lymph nodes, and enhanced the production of IL-17, IL-16, IL-6 and TNF-α in lymphocyte culture supernatants. Taken together, our results suggest that oral vaccination with recombinant H. pylori antigens (NAP/UreA/UreB) and dmLT confers more effective prophylactic protection against H. pylori infection than whole bacterial lysates in BALB/c mice. The reduction of H. pylori colonization was associated with the induction of antigen-specific Th17 and local mucosal IgA immune responses.

Synthetic Lipopeptide Enhances Protective Immunity Against Helicobacter pylori Infection

Over fifty percent of the people around the world is infected with Helicobacter pylori (H. pylori), which is the main cause of gastric diseases such as chronic gastritis and stomach cancer. H. pylori adhesin A (HpaA), which is a surface-located lipoprotein, is essential for bacterial colonization in the gastric mucosa. HpaA had been proposed to be a promising vaccine candidate against H. pylori infection. However, the effect of non-lipidated recombinant HpaA (rHpaA) to stimulate immune response was not very ideal, and the protective effect against H. pylori infection was also limited. Here, we hypothesized that low immunogenicity of rHpaA may attribute to lacking the immunostimulatory properties endowed by the lipid moiety. In this study, two novel lipopeptides, LP1 and LP2, which mimic the terminal structure of the native HpaA (nHpaA), were synthesized and TLR2 activation activity was confirmed in vitro. To investigate whether two novel lipopeptides could improve the protective effect of rHpaA against the infection of H. pylori, groups of mice were immunized either intramuscularly or intranasally with rHpaA together with LP1 or LP2. Compared with rHpaA alone, the bacterial colonization of the mice immunized with rHpaA plus LP2 via intranasal route was significantly decreased and the expression levels of serum IgG2a, IFN-γ, and IL-17 cytokines in spleen lymphocyte culture supernatant increased obviously, indicating that the enhanced protection of LP2 may be associated with elevated specific Th1 and Th17 responses. In conclusion, LP2 has been shown to improve the protective effect of rHpaA against H. pylori infection, which may be closely related to its ability in activating TLR2 by mimicking the terminal structure of nHpaA.

A survey on chimeric UreB229-561-HpaA protein targeting Helicobacter pylori: Computational and in vitro urease activity valuation

Helicobacter pylori (H. pylori) as microaerophilic, Gram-negative bacterium colonize the human gastric milieu, where it impetuses chronic disorders. Vaccination is a complementary plan, along with antibiotic therapy, for clearance of H. pylori. Today, Computer based tools are essential for the evaluation, design, and experiment for novel chimeric targets for immunological administration. The purpose of this experiment was immunoinformatic analysis of UreB and HpaA molecules in a fusion arrangement and also, construction and expression of recombinant protein containing chimeric sequences. The targets sequences were screened by using of standard in silico tools and immunoinformatic web servers. The high-resolution 3D models of the protein were created and were validated; indeed, the B-and T-cell restricted epitopes were mapped on the chimeric protein. The recombinant protein in frame of the expression vector pET28a were expressed and purified successfully. The urease activity and immunoblotting were performed in vitro condition. This study confirmed that the engineered protein as a highly conserved, hydrophilic, non-allergenic contained remarkable B-cell and T-cell epitopes. It was magnificently attained; chimeric UreB_229-561-HpaA could provoke both humoral and cellular immunity. The immunoblotting was shown that the chimeric protein could be detected by serum of immunized animal and H.pylori positive patients. In this study, several antigenic patches from UreB and HpaA were identified that could be an efficient immune system activator. The in vitro analysis of our chimeric molecule confirmed its urease activity. It also confirmed that the chimeric protein could be detected by serum of immunized animal and H.pylori positive patients.

Delivery of Helicobacter pylori HpaA to gastrointestinal mucosal immune sites using Lactococcus lactis and its immune efficacy in mice

OBJECTIVE

To develop a safe and effective oral vaccine against Helicobacter pylori using its HpaA protein expressed in Lactococcus lactis.

RESULTS

The gene encoding HpaA was obtained by PCR and ligated to pNZ8110-lysM following digestion with NaeI + SphI. The recombinant plasmid was transferred into E. coli for multiplication, and then into L. lactis. The recombinant L. lactis was induced to express HpaA, resulting in two products of 29 and 25 kDa, both of which yielded positive immunoreaction with mouse antisera against H. pylori, as confirmed by immunoblot assays. The 29 kDa product constituted 12% of the cell lysates. Oral inoculation with the engineered L. lactis evoked significantly elevated serum IgG level in mice (P < 0.05).

CONCLUSIONS

A novel engineered L. lactis strain was developed that efficiently produces whole HpaA protein with desired antigenicity and potent immunogenicity. It provides a basis for approaches to L. lactis-delivered anti-H. pylori vaccination.

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.

Construction of a recombinant Lactococcus lactis strain expressing a fusion protein of Omp22 and HpaA from Helicobacter pylori for oral vaccine development

OBJECTIVES

To develop orally administrated anti-Helicobacter pylori vaccination, a Lactococcus lactis strain was genetically constructed for fusion expression of H. pylori protective antigens HpaA and Omp22.

RESULTS

The fusion gene of omp22 and hpaA with an adapter encoding three glycines was cloned from a plasmid pMAL-c2x-omp22-hpaA into Escherichia coli MC1061 and L. lactis NZ3900 successively using a shutter vector pNZ8110. Expression of the fusion gene in L. lactis was induced with nisin resulting in production of proteins with molecular weights of 50 and 28 kDa. Both of them were immunoreactive with mouse anti-H. pylori sera as determined via western blotting. Oral vaccination of BALB/c mice using the L. lactis strain carrying pNZ8110-omp22-hpaA elicited significant systematic humoral immune response (P < 0.05).

CONCLUSIONS

This is the first report showing that a fusion protein of two H. pylori antigens was efficiently expressed in L. lactis with immunogenicity. This is a considerable step towards H. pylori vaccines.

Helicobacter pylori vaccination: Is there a path to protection?

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

Oral immunization with recombinant Lactococcus lactis delivering a multi-epitope antigen CTB-UE attenuates Helicobacter pylori infection in mice

Urease is an essential virulence factor and colonization factor for Helicobacter pylori (H. pylori) and is considered as an excellent vaccine candidate antigen. However, conventional technologies for preparing an injectable vaccine require purification of the antigenic protein and preparation of an adjuvant. Lactococcus lactis NZ9000 (L. lactis) could serve as an antigen-delivering vehicle for the development of edible vaccine. In previous study, we constructed a multi-epitope vaccine, designated CTB-UE, which is composed of the mucosal adjuvant cholera toxin B subunit (CTB), three Th cell epitopes and two B-cell epitopes from urease subunits. To develop a novel type of oral vaccine against H. pylori, genetically modified L. lactis strains were established to secrete this epitope vaccine extracellularly in this study. Oral prophylactic immunization with recombinant L. lactis significantly elicited humoral anti-urease antibody responses (P < 0.001) and reduced the gastric colonization of H. pylori from 7.14 ± 0.95 to 4.68 ± 0.98 log10 CFU g(-1) stomach. This L. lactis oral vaccine offers a promising vaccine candidate for the control of H. pylori infection.

Helicobacter pylori infection: selected aspects in clinical management

PURPOSE OF REVIEW

This review focuses on new aspects of recently published guidelines for the management of Helicobacter pylori infection as well as progress in diagnostic tests and treatment regimens. We also discuss new strategies for gastric cancer prevention.

RECENT FINDINGS

The general recommendation to treat H. pylori infection whenever diagnosed still faces resistance for reasons that are pertinent to the diversity of related clinical outcomes and to the complexity of eradication regimens. Thus, new updated guidelines for the management of H. pylori infection have been released in several continents. Progress has been made in molecular diagnostic tests for the detection of antibiotic resistance and serological tests for the detection of advanced gastric atrophic changes. Effective quadruple therapies in various combinations of 'traditional drugs' have been introduced with sequential or concomitant order of administration. Moreover, traditional drugs in a new galenic formulation have been introduced to overcome increasing H. pylori antibiotic resistance. Effective strategies for gastric cancer prevention have been adopted in some countries with high gastric cancer incidence, and have successfully contributed to lower the gastric cancer incidence. A screen-and-treat strategy for individuals at increased risk for gastric cancer needs to be further explored also in areas with low/moderate incidence of gastric cancer.

SUMMARY

New guidelines share many universal similarities across countries but respect and emphasize specific needs and requirements in individual communities. Various combinations of traditional drugs have been successfully introduced to overcome the increasing H. pylori antibiotic resistance. Gastric cancer prevention by a screen and treat strategy showed promising results.