HpaA is essential for Helicobacter pylori colonization in mice

Helicobacter pylori γ-glutamyltransferase is linked to proteomic adaptions important for colonization

Helicobacter pylori γ-glutamyltransferase (gGT) is a virulence factor that promotes bacterial colonization and immune tolerance. Although some studies addressed potential functional mechanisms, the supportive role of gGT for in vivo colonization remains unclear. Additionally, it is unknown how different gGT expression levels may lead to compensatory mechanisms ensuring infection and persistence. Hence, it is crucial to unravel the in vivo function of gGT. We assessed acid survival under conditions mimicking the human gastric fluid and elevated the pH in the murine stomach prior to H. pylori infection to link gGT-mediated acid resistance to colonization. By comparing proteomes of gGT-proficient and -deficient isolates before and after infecting mice, we investigated proteomic adaptations of gGT-deficient bacteria during infection. Our data indicate that gGT is crucial to sustain urease activity in acidic environments, thereby supporting survival and successful colonization. Absence of gGT triggers expression of proteins involved in the nitrogen and iron metabolism and boosts the expression of adhesins and flagellar proteins during infection, resulting in increased motility and adhesion capacity. In summary, gGT-dependent mechanisms confer a growth advantage to the bacterium in the gastric environment, which renders gGT a valuable target for the development of new treatments against H. pylori infection.

The urease E subunit vaccine stimulate the immune response versus Helicobacter pylori in animal model

There is a strong association between Helicobacter pylori (H. pylori) and the occurrence of gastritis and gastric mucosal lymphoma in the human population. Vaccination is a viable preventive measure in light of the escalating issue of antibiotic resistance. The use of DNA vaccines presents a potentially effective approach. This study used the utilization of antigenic H. pylori urease E subunit (UreE) for the development of a DNA vaccine. The UreE gene was chemically cloned into pIRES2-DsRed-Express (pDNA), and PCR and restriction enzyme digestion verified the cloning. The immunogenicity and immune-protective efficacy of the vaccination were assessed in BALB/c mice. In contrast, blood samples from BALB/c mice inoculated with pDNA-UreE showed higher levels of IgG, IFN-γ, IL- 4, and IL- 17. Furthermore, stomach damage and bacterial loads were reduced, and BALB/c mice inoculated with pDNA-UreE exhibited a significant protection rate (87.5%) against the H. pylori challenge. pDNA-UreE generated a combination of Th1-Th2-Th17 immune responses, perhaps contributing to adequate protection. Based on our findings, using this DNA immunization as a preventive measure against H. pylori infection is a viable approach.

Modeling and optimization of culture media for recombinant Helicobacter pylori vaccine antigen HpaA

Introduction

H. pylori (Helicobacter pylori) infection represents a significant global health concern, exacerbated by the emergence of drug-resistant strains resulting from conventional antibiotic treatments. Consequently, the development of vaccines with both preventive and therapeutic properties has become crucial in addressing H. pylori infections. The H. pylori adhesin protein HpaA has demonstrated strong immunogenicity across various adjuvants and dosage forms, positioning it as a key candidate antigen for recombinant subunit vaccines against H. pylori. Optimizing fermentation culture conditions is an effective strategy to enhance product yield and lower production costs. However, to date, there has been no systematic investigation into methods for improving the fermentation yield of HpaA. Enhancing the fermentation medium to increase HpaA yield holds significant potential for application and economic benefits in the prevention and detection of H. pylori infection.

Methods

To achieve a stable and high-yielding H. pylori vaccine antigen HpaA, this study constructed recombinant Escherichia coli expressing HpaA. The impact of fermentation medium components on the rHpaA yield was assessed using a one-factor-at-a-time approach alongside Plackett-Burman factorial experiments. Optimal conditions were effectively identified through response surface methodology (RSM) and artificial neural network (ANN) statistical computational models. The antigenicity and immunogenicity of the purified rHpaA were validated through immunization of mice, followed by Western Blot analysis and serum IgG ELISA quantification.

Results

Glucose, yeast extract, yeast peptone, NH4Cl and CaCl2 all contributed to the production of rHpaA, with glucose, yeast extract, and NH4Cl demonstrating particularly significant effects. The artificial neural network linked genetic algorithm (ANN-GA) model exhibited superior predictive accuracy, achieving a rHpaA yield of 0.61 g/L, which represents a 93.2% increase compared to the initial medium. Animal immunization experiments confirmed that rHpaA possesses good antigenicity and immunogenicity.

Discussion

This study pioneers the statistical optimization of culture media to enhance rHpaA production, thereby supporting its large-scale application in H. pylori vaccines. Additionally, it highlights the advantages of the ANN-GA approach in bioprocess optimization.

It's not all about flagella - sticky invasion by pathogenic spirochetes

Pathogenic spirochetes cause a range of serious human diseases such as Lyme disease (LD), syphilis, leptospirosis, relapsing fever (RF), and periodontal disease. Motility is a critical virulence factor for spirochetes. From the mechanical perspective of the infection, it has been widely believed that flagella are the sole key players governing the migration and dissemination of these pathogens in the host. Here, we highlight the important contribution of spirochetal surface-exposed adhesive molecules and their dynamic interactions with host molecules in the process of infection, specifically in spirochetal swimming and crawling migration. We believe that these recent findings overturn the prevailing view depicting the spirochetal body to be just an inert elastic bag, which does not affect spirochetal cell locomotion.

Unraveling the crystal structure of the HpaA adhesin: insights into cell adhesion function and epitope localization of a Helicobacter pylori vaccine candidate

Helicobacter pylori is a bacterium that exhibits strict host restriction to humans and non-human primates, and the bacterium is widely acknowledged as a significant etiological factor in the development of chronic gastritis, peptic ulcers, and gastric cancers. The pathogenic potential of this organism lies in its adeptness at colonizing the gastric mucosa, which is facilitated by a diverse repertoire of virulence factors, including adhesins that promote the attachment of the bacteria to the gastric epithelium. Among these adhesins, HpaA stands out due to its conserved nature and pivotal role in establishing H. pylori colonization. Moreover, this lipoprotein holds promise as an antigen for the development of effective H. pylori vaccines, thus attracting considerable attention for in-depth investigations into its molecular function and identification of binding determinants. Here, we present the elucidation of the crystallographic structure of HpaA at 2.9 Å resolution. The folding adopts an elongated protein shape, which is distinctive to the Helicobacteraceae family, and features an apical domain extension that plays a critical role in the cell-adhesion activity on gastric epithelial cells. Our study also demonstrates the ability of HpaA to induce TNF-α expression in macrophages, highlighting a novel role as an immunoregulatory effector promoting the pro-inflammatory response in vitro. These findings not only contribute to a deeper comprehension of the multifaceted role of HpaA in H. pylori pathogenesis but also establish a fundamental basis for the design and development of structure-based derivatives, aimed at enhancing the efficacy of H. pylori vaccines.

IMPORTANCE

Helicobacter pylori is a bacterium that can cause chronic gastritis, peptic ulcers, and gastric cancers. The bacterium adheres to the lining of the stomach using proteins called adhesins. One of these proteins, HpaA, is particularly important for H. pylori colonization and is considered a promising vaccine candidate against H. pylori infections. In this work, we determined the atomic structure of HpaA, identifying a characteristic protein fold to the Helicobacter family and delineating specific amino acids that are crucial to support the attachment to the gastric cells. Additionally, we discovered that HpaA can trigger the production of TNF-α, a proinflammatory molecule, in macrophages. These findings provide valuable insights into how H. pylori causes disease and suggest that HpaA has a dual role in both attachment and immune activation. This knowledge could contribute to the development of improved vaccine strategies for preventing H. pylori infections.

An M cell-targeting recombinant L. lactis vaccine against four H. pylori adhesins

The acidic environment and enzyme degradation lead to oral vaccines often having little immune effect. Therefore, it is an attractive strategy to study an effective and safe oral vaccine delivery system that can promote gastrointestinal mucosal immune responses and inhibit antigen degradation. Moreover, the antigens uptake by microfold cells (M cells) is the determining step in initiating efficient immune responses. Therefore, M cell-targeting is one promising approach for enhancing oral vaccine potency. In the present study, an M cell-targeting L. lactis surface display system (plSAM) was built to favor the multivalent epitope vaccine antigen (FAdE) to achieve effective gastrointestinal mucosal immunity against Helicobacter pylori. Therefore, a recombinant Lactococcus lactic acid vaccine (LL-plSAM-FAdE) was successfully prepared, and its immunological properties and protective efficacy were analyzed. The results showed that LL-plSAM-FAdE can secretively express the recombinant proteins SAM-FAdE and display the SAM-FAdE on the bacterial cell surface. More importantly, LL-plSAM-FAdE effectively promoted the phagocytosis and transport of vaccine antigen by M cells in the gastrointestinal tract of mice, and simulated high levels of cellular and humoral immune responses against four key H. pylori adhesins (Urease, CagL, HpaA, and Lpp20) in the gastrointestinal tract, thus enabling effective prevention of H. pylori infection and to some extent eliminating H. pylori already present in the gastrointestinal tract. KEY POINTS: • M-cell-targeting L. lactis surface display system LL- plSAM was designed • This system displays H. pylori vaccine-promoted phagocytosis and transport of M cell • A promising vaccine candidate for controlling H. pylori infection was verified.

A multiserological line assay to potentially discriminate current from past Helicobacter pylori infection

OBJECTIVES

Early diagnosis is important in controlling Helicobacter pylori-induced gastritis and progression to gastric malignancy. Serological testing is an efficient non-invasive diagnostic method, but currently does not allow differentiation between active and past infections. To fill this diagnostic gap we investigated the diagnostic value of a panel of ten H. pylori-specific antibodies in individuals with different H. pylori infection status within a German population.

METHODS

We used the recomLine Helicobacter IgG 2.0 immunoblotting assay to analyse ten H. pylori-specific antibodies in serum samples collected from 1108 volunteers. From these, 788 samples were used to build exposure and infection status models and 320 samples for model validation. H. pylori infection status was verified by histological examination. We applied logistic regression to select antibodies correlated to infection status and developed, with independent validation, discriminating models and risk scores. Receiving operating characteristic analysis was performed to assess the accuracy of the discriminating models.

RESULTS

Antibody reactivity against cytotoxin-associated gene A (CagA), H. pylori chaperone (GroEL), and hook-associated protein 2 homologue (FliD) was independently associated with the risk of H. pylori exposure with ORs and 95% CIs of 99.24 (46.50-211.80), 46.17 (17.45-122.17), and 22.16 (8.46-55.04), respectively. A risk score comprising these three selected antibodies differentiated currently H. pylori infected or eradicated participants from negatives with an area under the curve of 0.976 (95% CI: 0.965-0.987) (Model 1). Seropositivity for vacuolating cytotoxin A (VacA), GroEL, FliD, H. pylori adhesin A (HpaA), and γ-glutamyl transpeptidase (gGT) was associated with a current infection with an area under the curve of 0.870 (95% CI: 0.837-0.903), which may help discriminate currently infected patients from eradicated ones (Model 2).

DISCUSSION

The recomLine assay is sensitive and specific in determining H. pylori infection and eradication status and thus represents a valuable tool in the management of H. pylori infection.

Identification and characterization of shark VNARs targeting the Helicobacter pylori adhesin HpaA

Helicobacter pylori (H. pylori) is recognized as a pathogen associated with several gastrointestinal diseases. The current treatments exhibit numerous drawbacks, including antibiotic resistance. H. pylori can adhere to and colonize the gastric mucosa through H. pylori adhesin A (HpaA), and antibodies against HpaA may be an effective therapeutic approach. The variable domain of immunoglobulin new antigen receptor (VNAR) is a novel type of single-domain antibody with a small size, good stability, and easy manufacturability. This study isolated VNARs against HpaA from an immune shark VNAR phage display library. The VNARs can bind both recombinant and native HpaA proteins. The VNARs, 2A2 and 3D6, showed high binding affinities to HpaA with different epitopes. Furthermore, homodimeric bivalent VNARs, biNb-2A2 and biNb-3D6, were constructed to enhance the binding affinity. The biNb-2A2 and biNb-3D6 had excellent stability at gastrointestinal pH conditions. Finally, a sandwich ELISA assay was developed to quantify the HpaA protein using BiNb-2A2 as the capture antibody and BiNb-3D6 as the detection antibody. This study provides a potential foundation for novel alternative approaches to treatment or diagnostics applications of H. pylori infection.

Vaccination against Helicobacter pylori - An approach for cancer prevention?

The gram-negative bacterium Helicobacter pylori is the most common chronic bacterial infection and the main cause of gastric cancer. Due to the increasing antimicrobial resistance of H. pylori, the development of an efficacious vaccine is a valid option to protect from disease or infection and ultimately prevent gastric cancer. However, despite more than 30 years of research, no vaccine has entered the market yet. This review highlights the most relevant previous preclinical and clinical studies to allow conclusions to be drawn on which parameters need special attention in the future to develop an efficacious vaccine against H. pylori and thus prevent gastric cancer.

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.

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.

Prediction of gastric cancer risk by a polygenic risk score of Helicobacter pylori

BACKGROUND

Genetic variants of Helicobacter pylori (H. pylori) are involved in gastric cancer occurrence. Single nucleotide polymorphisms (SNPs) of H. pylori that are associated with gastric cancer have been reported. The combined effect of H. pylori SNPs on the risk of gastric cancer remains unclear.

AIM

To assess the performance of a polygenic risk score (PRS) based on H. pylori SNPs in predicting the risk of gastric cancer.

METHODS

A total of 15 gastric cancer-associated H. pylori SNPs were selected. The associations between these SNPs and gastric cancer were further validated in 1022 global strains with publicly available genome sequences. The PRS model was established based on the validated SNPs. The performance of the PRS for predicting the risk of gastric cancer was assessed in global strains using quintiles and random forest (RF) methods. The variation in the performance of the PRS among different populations of H. pylori was further examined.

RESULTS

Analyses of the association between selected SNPs and gastric cancer in the global dataset revealed that the risk allele frequencies of six SNPs were significantly higher in gastric cancer cases than non-gastric cancer cases. The PRS model constructed subsequently with these validated SNPs produced significantly higher scores in gastric cancer. The odds ratio (OR) value for gastric cancer gradually increased from the first to the fifth quintile of PRS, with the fifth quintile having an OR value as high as 9.76 (95% confidence interval: 5.84-16.29). The results of RF analyses indicated that the area under the curve (AUC) value for classifying gastric cancer and non-gastric cancer was 0.75, suggesting that the PRS based on H. pylori SNPs was capable of predicting the risk of gastric cancer. Assessing the performance of the PRS among different H. pylori populations demonstrated that it had good predictive power for cancer risk for hpEurope strains, with an AUC value of 0.78.

CONCLUSION

The PRS model based on H. pylori SNPs had a good performance for assessment of gastric cancer risk. It would be useful in the prediction of final consequences of the H. pylori infection and beneficial for the management of the infection in clinical settings.

Transcriptional and functional characterizations of multiple flagellin genes in spirochetes

The flagellar filament is a helical propeller for bacterial locomotion. In external flagellates, the filaments are mostly homopolymers of a single flagellin protein. By contrast, the flagellar filaments of spirochetes are mostly heteropolymers of multiple flagellin proteins. This report seeks to investigate the role of multiple flagellin proteins using the oral spirochete Treponema denticola as a model. First, biochemical and genetic studies uncover that the flagellar filaments of T. denticola mainly comprise four proteins, FlaA, FlaB1, FlaB2, and FlaB3, in a defined stoichiometry. Second, transcriptional analyses reveal that the genes encoding these four proteins are regulated by two different transcriptional factors, sigma28 and sigma70 . Third, loss-of-function studies demonstrate that each individual flagellin protein contributes to spirochete motility, but none of them is absolutely required. Last, we provide genetic and structural evidence that FlaA forms a "seam"-like structure around the core and that deletion of individual flagellin protein alters the flagellar homeostasis. Collectively, these results demonstrate that T. denticola has evolved a unique mechanism to finely regulate its flagellar filament gene expression and assembly which renders the organelle with the right number, shape, strength, and structure for its distinct motility.

Hesperetin Inhibits Expression of Virulence Factors and Growth of Helicobacter pylori

Helicobacter pylori (H. pylori) is a bacterium known to infect the human stomach. It can cause various gastrointestinal diseases including gastritis and gastric cancer. Hesperetin is a major flavanone component contained in citrus fruits. It has been reported to possess antibacterial, antioxidant, and anticancer effects. However, the antibacterial mechanism of hesperetin against H. pylori has not been reported yet. Therefore, the objective of this study was to determine the inhibitory effects of hesperetin on H. pylori growth and its inhibitory mechanisms. The results of this study showed that hesperetin inhibits the growth of H. pylori reference strains and clinical isolates. Hesperetin inhibits the expression of genes in replication (dnaE, dnaN, dnaQ, and holB) and transcription (rpoA, rpoB, rpoD, and rpoN) machineries of H. pylori. Hesperetin also inhibits the expression of genes related to H. pylori motility (flhA, flaA, and flgE) and adhesion (sabA, alpA, alpB, hpaA, and hopZ). It also inhibits the expression of urease. Hespereti n downregulates major virulence factors such as cytotoxin-associated antigen A (CagA) and vacuolating cytotoxin A (VacA) and decreases the translocation of CagA and VacA proteins into gastric adenocarcinoma (AGS) cells. These results might be due to decreased expression of the type IV secretion system (T4SS) and type V secretion system (T5SS) involved in translocation of CagA and VacA, respectively. The results of this study indicate that hesperetin has antibacterial effects against H. pylori. Thus, hesperetin might be an effective natural product for the eradication of H. pylori.

Sialic Acids as Receptors for Pathogens

Carbohydrates have long been known to mediate intracellular interactions, whether within one organism or between different organisms. Sialic acids (Sias) are carbohydrates that usually occupy the terminal positions in longer carbohydrate chains, which makes them common recognition targets mediating these interactions. In this review, we summarize the knowledge about animal disease-causing agents such as viruses, bacteria and protozoa (including the malaria parasite Plasmodium falciparum) in which Sias play a role in infection biology. While Sias may promote binding of, e.g., influenza viruses and SV40, they act as decoys for betacoronaviruses. The presence of two common forms of Sias, Neu5Ac and Neu5Gc, is species-specific, and in humans, the enzyme converting Neu5Ac to Neu5Gc (CMAH, CMP-Neu5Ac hydroxylase) is lost, most likely due to adaptation to pathogen regimes; we discuss the research about the influence of malaria on this trait. In addition, we present data suggesting the CMAH gene was probably present in the ancestor of animals, shedding light on its glycobiology. We predict that a better understanding of the role of Sias in disease vectors would lead to more effective clinical interventions.

Oral multivalent epitope vaccine, based on UreB, HpaA, CAT, and LTB, for prevention and treatment of Helicobacter pylori infection in C57BL / 6 mice

BACKGROUND

As the resistance of Helicobacter pylori to traditional triple therapy is gradually revealed, an increasing number of people are focusing on vaccine treatments for H. pylori infection. Epitope vaccines are a promising strategy for the treatment of H. pylori infection, and multivalent vaccines will be more effective than monovalent vaccines.

MATERIALS AND METHODS

In this study, we designed a multivalent vaccine named LHUC, which consists of the adjuvant LTB as well as three Th cell epitopes (HpaA_154-171 , UreB_237-251, and UreB_546-561 ) and five B-cell epitopes (UreB_349-363 , UreB_327-334 , CAT_394-405 , CAT_387-397, and HpaA_132-141 ) from UreB, HpaA, and catalase. In BALB/c mice, the specificity and immunogenicity of the fusion peptide LHUC and the neutralization of H. pylori urease and catalase by the specific IgG elicited by LHUC were evaluated. The preventive and therapeutic effects of LHUC were evaluated in C57BL/6 mice infected with H. pylori.

RESULTS

The results showed that compared with LTB and PBS, LHUC induced specific IgG and IgA antibody production in mice, and IgG antibodies significantly inhibited the H. pylori urease and catalase activities in vitro. Additionally, by detecting the levels of IFN-γ, IL-4, and IL-17 in lymphocyte supernatants, we proved that LHUC could activate Th1, Th2, and Th17 mixed T-cell immune responses in vivo. Finally, a C57BL/6 mouse model of gastric infection with H. pylori was established. The results showed that compared with the effects of LTB and PBS, the prevention and treatment effects of oral inoculation with LHUC significantly inhibited bacterial colonization.

CONCLUSIONS

In conclusion, LHUC, a multivalent vaccine based on multiple H. pylori antigens, is a promising and safe vaccine that can effectively reduce the colonization of H. pylori in the stomach.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

A Novel Multi-Epitopic Peptide Vaccine Candidate Against Helicobacter pylori: In-Silico Identification, Design, Cloning and Validation Through Molecular Dynamics

Helicobacter pylori is a highly potential pathogen to colonize in the human stomach. This bacterial strain is now alarming serious health concern all over the world. Combating through available drugs is a difficult task due to lack of appropriate common targets against genetically diverse strains. Therefore, the developments of effective targets vaccines require alternative strategies to eliminate the H. pylori infection. In this study, we developed a novel vaccine construct using B-cell derived T-cell epitopes from four target antigenic proteins (HpaA, FlaA, FlaB and Omp18), and found the induction of possible immune response using advanced immunoinformatics approaches. In order to boost immune system, we tagged adjuvant (50S ribosomal protein L7/L12) with a suitable linker at the N-terminus side of vaccine sequence. Protein–protein docking between human Toll like receptor 5 (TLR5) and vaccine construct help to predict the way of inductive signaling that leads to immune-response. The calculated negative score (− 151.4, + / − 8.7) of molecular docking complex signify the best binding interface. Molecular dynamics simulation studies confirmed the proper docking between TLR5 and vaccine candidate. Moreover, Normal mode analysis (NMA) calculates the molecular motion of the docking complex. The low eigenvalue (2.935e⁻⁰⁵) indicates the stable and flexible molecular motion in the binding interaction side. Finally, in-silico cloning of vaccine candidate was performed using expression vector pET28b (+) with the optimized restriction sites.

Quantitative proteomics approach to investigate the antibacterial response of Helicobacter pylori to daphnetin, a traditional Chinese medicine monomer

Helicobacter pylori is a Gram-negative bacterium related to the development of peptic ulcers and stomach cancer. An increasing number of infected individuals are found to harbor antibiotic-resistant H. pylori, which results in treatment failure. Daphnetin, a traditional Chinese medicine, has a broad spectrum of antibacterial activity without the development of bacterial resistance. However, the antibacterial mechanisms of daphnetin have not been elucidated entirely. To better understand the mechanisms of daphnetin's effect on H. pylori, a label-free quantitative proteomics approach based on an EASY-nLC 1200 system coupled with an Orbitrap Fusion Lumos mass spectrometer was established to investigate the key protein differences between daphnetin- and non-daphnetin-treated H. pylori. Using the criteria of greater than 1.5-fold changes and adjusted p value <0.05, proteins related to metabolism, membrane structure, nucleic acid and protein synthesis, ion binding, H. pylori colonization and infection, stress reaction, flagellar assembly and so on were found to be changed under daphnetin pressure. And the changes of selected proteins in expression level were confirmed by targeted proteomics. These new data provide us a more comprehensive horizon of the proteome changes in H. pylori that occur in response to daphnetin.

Identification of Functional Interactome of Gastric Cancer Cells with Helicobacter pylori Outer Membrane Protein HpaA by HPLC-MS/MS

HpaA as an outer membrane protein of Helicobacter pylori (H. pylori) plays a significant role in the adhesion to the human stomach, but the functional relation between HpaA and gastric epithelial cells is still not clear. To screen the interaction between HpaA and cellular proteins in gastric epithelial cells, the HpaA protein from H. pylori 26695 fused with a tag (6× His) was expressed and purified successfully, the secondary structure was estimated by the Circular Dichroism (CD) spectrum, and the purified recombinant protein was used to perform the pull-down assays with gastric cancer cell lines (AGS and SGC-7901) lysates, respectively. The pull-down proteins were identified by high-performance liquid chromatography tandem mass spectrometry system (HPLC-MS/MS). A total of 9 and 13 proteins related were analyzed from AGS and SGC-7901 cell lysates, respectively. ANXA2 was considered as putative HpaA functional partner discovered from lysates of both cell lines with high score and coverage. It is hypothesized that HpaA may be involved in the biological process of regulation of transcription and nucleic acid metabolism during the adhesion of H. pylori to human gastric epithelial cells, and HpaA-binding proteins also be used as targets for the development of antiadhesion drugs against H. pylori.

Phylogenetic Distribution, Ultrastructure, and Function of Bacterial Flagellar Sheaths

A number of Gram-negative bacteria have a membrane surrounding their flagella, referred to as the flagellar sheath, which is continuous with the outer membrane. The flagellar sheath was initially described in Vibrio metschnikovii in the early 1950s as an extension of the outer cell wall layer that completely surrounded the flagellar filament. Subsequent studies identified other bacteria that possess flagellar sheaths, most of which are restricted to a few genera of the phylum Proteobacteria. Biochemical analysis of the flagellar sheaths from a few bacterial species revealed the presence of lipopolysaccharide, phospholipids, and outer membrane proteins in the sheath. Some proteins localize preferentially to the flagellar sheath, indicating mechanisms exist for protein partitioning to the sheath. Recent cryo-electron tomography studies have yielded high resolution images of the flagellar sheath and other structures closely associated with the sheath, which has generated insights and new hypotheses for how the flagellar sheath is synthesized. Various functions have been proposed for the flagellar sheath, including preventing disassociation of the flagellin subunits in the presence of gastric acid, avoiding activation of the host innate immune response by flagellin, activating the host immune response, adherence to host cells, and protecting the bacterium from bacteriophages.

Unraveling the factors and mechanism involved in persistence: Host-pathogen interactions in Helicobacter pylori

Helicobacter pylori and humans have one of the most complex relationships in nature. How a bacterium manages to live in one of the harshest and hostile environments is a topic of unraveling mysteries. H. pylori is a prevalent species and it colonizes the human gut of more than 50% of the world population. It infects the epithelial region of antrum and persists there for a long period. Over the time of evolution, H. pylori has developed complex strategies to extend the degree of inflammation in gastric mucosa. H. pylori needs specific adaptations for initial colonization into the host environment like helical shape, flagellar movement, chemotaxis, and the production of urease enzyme that neutralizes acidic environment of the stomach. There are several factors from the bacterium as well as from the host that participate in these complex interactions. On the other hand, to establish the persistent infection, H. pylori escapes the immune system by mimicking the host antigens. This pathogen has the ability to dodge the immune system and then persist there in the form of host cell, which leads to immune tolerance. H. pylori has an ability to manipulate its own pathogen-associated molecular patterns, which leads to an inhibition in the binding with specific pattern recognition receptors of the host to avoid immune cell detection. Also, it manipulates the host metabolic homeostasis in the gastric epithelium. Besides, it has several genes, which may get involved in the acquisition of nutrition from the host to survive longer in the host. Due to the persistence of H. pylori, it causes chronic inflammation and raises the chances of gastric cancer. This review highlights the important elements, which are certainly responsible for the persistence of H. pylori in the human host.

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.

Epitope-loaded nanoemulsion delivery system with ability of extending antigen release elicits potent Th1 response for intranasal vaccine against Helicobacter pylori

BACKGROUND

Helicobacter pylori (H. pylori) infection remains a global public health issue, especially in Asia. Due to the emergence of antibiotic-resistant strains and the complexity of H. pylori infection, conventional vaccination is the best way to control the disease. Our previous study found that the N-acetyl-neuroaminyllactose-binding hemagglutinin protein (HpaA) is an effective protective antigen for vaccination against H. pylori infection, and intranasal immunization with the immunodominant HpaA epitope peptide (HpaA 154-171, P22, MEGVLIPAGFIKVTILEP) in conjunction with a CpG adjuvant decreased bacterial colonization in H. pylori-infected mice. However, to confer more robust and effective protection against H. pylori infection, an optimized delivery system is needed to enhance the P22-specific memory T cell response.

RESULTS

In this study, an intranasal nanoemulsion (NE) delivery system offering high vaccine efficacy without obvious cytotoxicity was designed and produced. We found that this highly stable system significantly prolonged the nasal residence time and enhanced the cellular uptake of the epitope peptide, which powerfully boosted the specific Th1 responses of the NE-P22 vaccine, thus reducing bacterial colonization without CpG. Furthermore, the protection efficacy was further enhanced by combining the NE-P22 vaccine with CpG.

CONCLUSION

This epitope-loaded nanoemulsion delivery system was shown to extend antigen release and elicit potent Th1 response, it is an applicable delivery system for intranasal vaccine against H. pylori.

Carbohydrate-Dependent and Antimicrobial Peptide Defence Mechanisms Against Helicobacter pylori Infections

The human stomach is a harsh and fluctuating environment for bacteria with hazards such as gastric acid and flow through of gastric contents into the intestine. H. pylori gains admission to a stable niche with nutrient access from exudates when attached to the epithelial cells under the mucus layer, whereof adherence to glycolipids and other factors provides stable and intimate attachment. To reach this niche, H. pylori must overcome mucosal defence mechanisms including the continuously secreted mucus layer, which provides several layers of defence: (1) mucins in the mucus layer can bind H. pylori and transport it away from the gastric niche with the gastric emptying, (2) mucins can inhibit H. pylori growth, both via glycans that can have antibiotic like function and via an aggregation-dependent mechanism, (3) antimicrobial peptides (AMPs) have antimicrobial activity and are retained in a strategic position in the mucus layer and (4) underneath the mucus layer, the membrane-bound mucins provide a second barrier, and can function as releasable decoys. Many of these functions are dependent on H. pylori interactions with host glycan structures, and both the host glycosylation and concentration of antimicrobial peptides change with infection and inflammation, making these interactions dynamic. Here, we review our current understanding of mucin glycan and antimicrobial peptide-dependent host defence mechanisms against H. pylori infection.

MECHANISMS OF INTERRACTION OF HELICOBACTER PYLORI WITH EPITHELIUM OF GASTRIC MUCOSA. I. PATHOGENIC FACTORS PROMOTING SUCCESSFUL COLONIZATION

H. pylori is a Gram-negative, crimp and motile bacterium that colonizes the hostile microniche of the human stomach roughly one half of the human population. Then persists for the host’s entire life, but only causes overt gastric disease in a subset of infected hosts. To the reasons contributing to the development of diseases, usually include: concomitant infections of the gastrointestinal tract, improper sterilization of medical instruments, usually endoscopes, nonobservance of personal hygiene rules, prolonged contact with infected or carriers, including family members and a number of other factors. Clinically, H. pylori plays a causative role in the development of a wide spectrum of diseases including chronic active gastritis, peptic and duodenal ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Due to the global distribution of H. pylori, we are able to conclude that smart strategies are contributing to adaptation of the bacterium in an aggressive environment of a stomach and lifelong permanent circulation in its host. Thirty-four years after the discovery of this bacterium, there are still many unanswered questions. For example, which strategies help the bacterium to survive in this inhospitable conditions? Understanding the mechanisms governing H. pylori persistence will improve identification of the increased risk of different gastric diseases in persons infected with this bacterium. A well-defined and long-term equilibrium between the human host and H. pylori allows bacterial persistence in the gastric microniche; although this coexistence leads to a high risk of severe diseases the diseases which are listed above. In this review, we discuss the pathogenesis of this bacterium and the mechanisms it uses to promote persistent colonization of the gastric mucosa, with a focus on recent insights into the role of some virulence factors like urease, LPS, outer membrane proteins, cytotoxins, factors, promoting invasion. Information on the mechanisms related to H. pylori persistence can also provide the direction for future research concerning effective therapy and management of gastroduodenal disorders. The topics presented in the current review are important for elucidating the strategies used by H. pylori to help the bacterium persist in relation to the many unfavorable features of living in the gastric microniche.

A GWAS on Helicobacter pylori strains points to genetic variants associated with gastric cancer risk

BACKGROUND

Helicobacter pylori are stomach-dwelling bacteria that are present in about 50% of the global population. Infection is asymptomatic in most cases, but it has been associated with gastritis, gastric ulcers and gastric cancer. Epidemiological evidence shows that progression to cancer depends upon the host and pathogen factors, but questions remain about why cancer phenotypes develop in a minority of infected people. Here, we use comparative genomics approaches to understand how genetic variation amongst bacterial strains influences disease progression.

RESULTS

We performed a genome-wide association study (GWAS) on 173 H. pylori isolates from the European population (hpEurope) with known disease aetiology, including 49 from individuals with gastric cancer. We identified SNPs and genes that differed in frequency between isolates from patients with gastric cancer and those with gastritis. The gastric cancer phenotype was associated with the presence of babA and genes in the cag pathogenicity island, one of the major virulence determinants of H. pylori, as well as non-synonymous variations in several less well-studied genes. We devised a simple risk score based on the risk level of associated elements present, which has the potential to identify strains that are likely to cause cancer but will require refinement and validation.

CONCLUSION

There are a number of challenges to applying GWAS to bacterial infections, including the difficulty of obtaining matched controls, multiple strain colonization and the possibility that causative strains may not be present when disease is detected. Our results demonstrate that bacterial factors have a sufficiently strong influence on disease progression that even a small-scale GWAS can identify them. Therefore, H. pylori GWAS can elucidate mechanistic pathways to disease and guide clinical treatment options, including for asymptomatic carriers.

Protection Against Helicobacter pylori Infection in BALB/c Mouse Model by Oral Administration of Multivalent Epitope-Based Vaccine of Cholera Toxin B Subunit-HUUC

Vaccination is an increasingly important alternative approach to control Helicobacter pylori infection, since H. pylori resistance to previously efficacious antibiotic regimens is increased, and H. pylori eradication treatment for upper gastrointestinal diseases is becoming less successful. Fortunately, an efficient oral monovalent H. pylori vaccine has been developed. However, compared with monovalent vaccines, multivalent vaccines have the potential to induce more effective and comprehensive protection against H. pylori infection. In this study, we designed and produced a multivalent epitope-based vaccine cholera toxin B subunit (CTB)-HUUC with the intramucosal adjuvant CTB and tandem copies of B-cell epitopes (HpaA132-141, UreA183-203, and UreB321-339) and T-cell epitopes (HpaA88-100, UreA27-53, UreB229-251, UreB317-329, UreB373-385, UreB438-452, UreB546-561, CagA149-164, and CagA196-217) from H. pylori adhesion A subunit (HpaA), urease A subunit (UreA), urease B subunit (UreB), and cytotoxin-associated antigen (CagA). Serum IgG, stomach, and intestine mucosal sIgA from mice after CTB-HUUC vaccination neutralized H. pylori urease activity in vitro. CTB-HUUC vaccination promoted H. pylori-specific lymphocyte responses and a mixed CD4⁺ T cell immune response as indicated by IFN-γ, interleukin-4, and interleukin-17 production in mice. Both oral prophylactic and therapeutic CTB-HUUC vaccinations reduced gastric urease activity and H. pylori infection and protected stomachs in mice. Taken together, CTB-HUUC is a promising potent and safe multivalent vaccine in controlling H. pylori infection in BALB/c mouse model.

Systematic identification of immunodominant CD4+ T cell responses to HpaA in Helicobacter pylori infected individuals

In mice, antigen-specific CD4⁺ T cell response is indispensible for the protective immunity against Helicobacter pylori (H. pylori). It has been demonstrated that neuraminyllactose-binding hemagglutinin (HpaA) immunization protected mice from H. pylori infection in a CD4⁺ T cell dependent manner. However, much remains unclear concerning the human CD4⁺ T cell responses to HpaA. We conducted a systematic study here to explore the immunodominant, HpaA-specific CD4⁺ T cell responses in H. pylori infected individuals. We found that HpaA-specific CD4⁺ T cell responses varied remarkably in their magnitude and had broad epitope-specificity. Importantly, the main responses focused on two regions: HpaA76-105 and HpaA130-159. The HLA-DRB1*0901 restricted HpaA142-159 specific CD4⁺ T cell response was the most immunodominant response at a population level. The immunodominant epitope HpaA142-159 was naturally presented and highly conserved. We also demonstrated that it was not the broad peptide specificity, but the strength of HpaA specific CD4⁺ T cell responses associated with gastric diseases potentially caused by H. pylori infection. Such investigation will aid development of novel vaccines against H. pylori infection.

Performance of a Multiplex Serological Helicobacter pylori Assay on a Novel Microfluidic Assay Platform

Infection with Helicobacter pylori (H. pylori) occurs in 50% of the world population, and is associated with the development of ulcer and gastric cancer. Serological diagnostic tests indicate an H. pylori infection by detecting antibodies directed against H. pylori proteins. In addition to line blots, multiplex assay platforms provide smart solutions for the simultaneous analysis of antibody responses towards several H. pylori proteins. We used seven H. pylori proteins (FliD, gGT, GroEL, HpaA, CagA, VacA, and HP0231) and an H. pylori lysate for the development of a multiplex serological assay on a novel microfluidic platform. The reaction limited binding regime in the microfluidic channels allows for a short incubation time of 35 min. The developed assay showed very high sensitivity (99%) and specificity (100%). Besides sensitivity and specificity, the technical validation (intra-assay CV = 3.7 ± 1.2% and inter-assay CV = 5.5 ± 1.2%) demonstrates that our assay is also a robust tool for the analysis of the H. pylori-specific antibody response. The integration of the virulence factors CagA and VacA allow for the assessment of the risk for gastric cancer development. The short assay time and the performance of the platform shows the potential for implementation of such assays in a clinical setting.

Role of Flagella in the Pathogenesis of Helicobacter pylori

This review aimed to investigate the role of Helicobacter pylori flagella on the pathogenicity of this bacterium in humans. Helicobacter pylori is a flagellated pathogen that colonizes the human gastroduodenal mucosa and produces inflammation, and is responsible for gastrointestinal disease. Its pathogenesis is attributed to colonization and virulence factors. The primary function of H. pylori flagella is to provide motility. We believe that H. pylori flagella play an important role in the colonization of the gastrointestinal mucosa. Therefore, we reviewed previous studies on flagellar morphology and motility in order to explore the relationship between H. pylori flagella and pathogenicity. Further investigation is required to confirm the association between flagella and pathogenicity in H. pylori.

Crystallization and X-ray analysis of the extracellular adhesion domain of Helicobacter pylori adhesin A: the significance of the cation composition in the crystallization precipitant

Adherence to host cells is a crucial step in the process of bacterial infection, which is usually mediated by a number of outer membrane proteins identified as adhesins. Helicobacter pylori adhesin A (HpaA) is a member of the adhesin family that mediates the adherence of Helicobacter pylori to gastric epithelial cells, and consequently assists the bacteria in becoming a life-long colonizer of the human stomach. In this study, two constructs were made for the production of truncated HpaA proteins comprising residues 31-260 and 53-260, respectively. The products of both constructs were crystallized, but only the protein from the shorter construct (residues 53-260) formed crystals that were capable of diffraction. In the subsequent optimization trials, crystals in different forms were unexpectedly obtained by using lithium sulfate and ammonium sulfate as the precipitant. An X-ray data set was collected to 1.95 Å resolution on beamline BL18U1 at SSRF using a crystal grown with 1.92 M lithium sulfate, which belonged to space group P65 with unit-cell parameters a = b = 95.42, c = 54.72 Å, γ = 120°, while another crystal grown with 1.9 M ammonium sulfate diffracted to 2.60 Å resolution and the collected data set was indexed in space group P21212, with unit-cell parameters a = 121.01, b = 190.56, c = 106.31 Å. The collection of diffraction data has established a solid basis for structure determination.

Fallacy of the Unique Genome: Sequence Diversity within Single Helicobacter pylori Strains

Many bacterial genomes are highly variable but nonetheless are typically published as a single assembled genome. Experiments tracking bacterial genome evolution have not looked at the variation present at a given point in time. Here, we analyzed the mouse-passaged Helicobacter pylori strain SS1 and its parent PMSS1 to assess intra- and intergenomic variability. Using high sequence coverage depth and experimental validation, we detected extensive genome plasticity within these H. pylori isolates, including movement of the transposable element IS607, large and small inversions, multiple single nucleotide polymorphisms, and variation in cagA copy number. The cagA gene was found as 1 to 4 tandem copies located off the cag island in both SS1 and PMSS1; this copy number variation correlated with protein expression. To gain insight into the changes that occurred during mouse adaptation, we also compared SS1 and PMSS1 and observed 46 differences that were distinct from the within-genome variation. The most substantial was an insertion in cagY, which encodes a protein required for a type IV secretion system function. We detected modifications in genes coding for two proteins known to affect mouse colonization, the HpaA neuraminyllactose-binding protein and the FutB α-1,3 lipopolysaccharide (LPS) fucosyltransferase, as well as genes predicted to modulate diverse properties. In sum, our work suggests that data from consensus genome assemblies from single colonies may be misleading by failing to represent the variability present. Furthermore, we show that high-depth genomic sequencing data of a population can be analyzed to gain insight into the normal variation within bacterial strains.IMPORTANCE Although it is well known that many bacterial genomes are highly variable, it is nonetheless traditional to refer to, analyze, and publish "the genome" of a bacterial strain. Variability is usually reduced ("only sequence from a single colony"), ignored ("just publish the consensus"), or placed in the "too-hard" basket ("analysis of raw read data is more robust"). Now that whole-genome sequences are regularly used to assess virulence and track outbreaks, a better understanding of the baseline genomic variation present within single strains is needed. Here, we describe the variability seen in typical working stocks and colonies of pathogen Helicobacter pylori model strains SS1 and PMSS1 as revealed by use of high-coverage mate pair next-generation sequencing (NGS) and confirmed by traditional laboratory techniques. This work demonstrates that reliance on a consensus assembly as "the genome" of a bacterial strain may be misleading.

Surface expression of Helicobacter pylori HpaA adhesion antigen on Vibrio cholerae, enhanced by co-expressed enterotoxigenic Escherichia coli fimbrial antigens

Helicobacter pylori infection can cause peptic ulceration and is associated with gastric adenocarcinoma. This study aimed to construct and characterize a non-virulent Vibrio cholerae O1 strain, which grows more rapidly than H. pylori, as vector for H. pylori antigens for possible use as a vaccine strain against H. pylori. This was done by recombinant expression of the H. pylori adhesion antigen HpaA alone or, as a proof of principle, together with different colonization factor (CF) antigens of enterotoxigenic Escherichia coli (ETEC) which may enhance immune responses against HpaA. A recombinant V. cholerae strain co-expressing HpaA and a fimbrial CF antigens CFA/I or CS5, but not the non-fimbrial CF protein CS6, was shown to express larger amounts of HpaA on the surface when compared with the same V. cholerae strain expressing HpaA alone. Mutations in the CFA/I operon showed that the chaperon, possibly together with the usher, was involved in enhancing the surface expression of HpaA. Oral immunization of mice with formaldehyde-inactivated recombinant V. cholerae expressing HpaA alone or together with CFA/I induced significantly higher serum antibody responses against HpaA than mice similarly immunized with inactivated HpaA-expressing H. pylori bacteria. Our results demonstrate that a non-virulent V. cholerae strain can be engineered to allow strong surface expression of HpaA, and that the expression can be further increased by co-expressing it with ETEC fimbrial antigens. Such recombinant V. cholerae strains expressing HpaA, and possibly also other H. pylori antigens, may have the potential as oral inactivated vaccine candidates against H. pylori.

Helicobacter pylori antibody responses in association with eradication outcome and recurrence: a population-based intervention trial with 7.3-year follow-up in China

OBJECTIVE

To identify serum biomarkers that may predict the short or long term outcomes of anti-Helicobacter pylori (H. pylori) treatment, a follow-up study was performed based on an intervention trial in Linqu County, China.

METHODS

A total of 529 subjects were selected randomly from 1,803 participants to evaluate total anti-H. pylori immunoglobulin G (IgG) and 10 specific antibody levels before and after treatment at 1-, 2- and 7.3-year. The outcomes of anti-H. pylori treatment were also parallelly assessed by¹³C-urea breath test at 45-d after treatment and 7.3-year at the end of follow-up.

RESULTS

We found the medians of anti-H. pylori IgG titers were consistently below cut-off value through 7.3 years in eradicated group, however, the medians declined in recurrence group to 1.2 at 1-year after treatment and slightly increased to 2.0 at 7.3-year. While the medians were significantly higher (>3.0 at 2- and 7.3-year) among subjects who failed the eradication or received placebo. For specific antibody responses, baseline seropositivities of FliD and HpaA were reversely associated with eradication failure [for FliD, odds ratio (OR)=0.44, 95% confidence interval (95% CI): 0.27-0.73; for HpaA, OR=0.32, 95% CI: 0.17-0.60]. The subjects with multiple positive specific antibodies at baseline were more likely to be successfully eradicated in a linear fashion (P_trend=0.006).

CONCLUSIONS

Our study suggested that total anti-H. pylori IgG level may serve as a potential monitor of long-term impact on anti-H. pylori treatment, and priority forH. pylori treatment may be endowed to the subjects with multiple seropositive antibodies at baseline, especially for FliD and HapA.

Cloning, expression and purification flagellar sheath adhesion of Helicobacter pylori in Escherichia coli host as a vaccination target

Purpose

Helicobacter pylori is a widely distributed gram-negative bacterium that infects the human stomach and duodenum. HpaA is a H. pylori–specific lipoprotein that has been shown to be an effective protective antigen against H. pylori infection. HpaA of H. pylori as a vaccine antigen is fully competent for stimulation of immune responses. The aim of this project is cloning, expression, and purification flagellar sheath adhesion of H. pylori in Escherichia coli host by fast protein liquid chromatography (FPLC) as a vaccination target.

Materials and Methods

The hpaA gene was inserted into pET28a (+) as cloning and expression vectors respectively. The recombinant plasmid (pET-hpaA) was subjected to sequencing other than polymerase chain reaction (PCR) and digestion analysis. Protein expression was induced by adding 1 mM isopropyl-β-D-thiogalactoside to cultures of E. coli strain BL21 transformed with pET-hpaA. Protein expression assessed with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Protein purification of flagellar sheath adhesion was by FPLC.

Results

The restriction endonuclease digestion, PCR amplification analysis showed that the hpaA gene of 730 bp was amplified from H. pylori DNA and sequencing analysis of the pET-hpaA confirmed the cloning accuracy and in frame insertion of hpaA fragment. SDS-PAGE analysis showed the expression of an approximately 29,000 Da protein.

Conclusion

Sequencing results along with SDS-PAGE analysis confirms the expression of recombinant hpaA in the heterologous E. coli BL21. Conclusion A prokaryotic expression system for hpaA gene was successfully constructed. These results indicate that production of a specific recombinant protein is an alternative and potentially more expeditious strategy for development of H. pylori vaccine.

Helicobacter pylori: bacterial strategy for incipient stage and persistent colonization in human gastric niches

Helicobacter pylori (H. pylori) undergoes decades long colonization of the gastric mucosa of half the population in the world to produce acute and chronic gastritis at the beginning of infection, progressing to more severe disorders, including peptic ulcer disease and gastric cancer. Prolonged carriage of H. pylori is the most crucial factor for the pathogenesis of gastric maladies. Bacterial persistence in the gastric mucosa depends on bacterial factors as well as host factors. Herein, the host and bacterial components responsible for the incipient stages of H. pylori infection are reviewed and discussed. Bacterial adhesion and adaptation is presented to explain the persistence of H. pylori colonization in the gastric mucosa, in which bacterial evasion of host defense systems and genomic diversity are included.

Oral immunization with recombinant Lactobacillus acidophilus expressing the adhesin Hp0410 of Helicobacter pylori induces mucosal and systemic immune responses

Helicobacter pylori infection is relatively common worldwide and is closely related to gastric mucosa-associated lymphoid tissue (MALT) lymphoma, chronic gastritis, and stomach ulcers. Therefore, a safe and effective method for preventing H. pylori infection is urgently needed. Given that developing an effective vaccine against H. pylori is one of the best alternatives, H. pylori adhesin Hp0410 was expressed in the food-grade bacterium Lactobacillus acidophilus. The recombinant live bacterial vaccine was then used to orally vaccinate mice, and the immunoprotective effects of Hp0410-producing strains were investigated. H. pylori colonization in the stomach of mice immunized with the recombinant L. acidophilus was significantly reduced, in comparison with that in control groups. Furthermore, mucosal secretory IgA antibodies were elicited in the mucosal tissue of mice immunized with the recombinant bacteria, and specific anti-Hp0410 IgG responses were also detected in mouse serum. There was a significant increase in the level of protection against gastric Helicobacter infection following a challenge with H. pylori Sydney strain 1 (SS1). Our results collectively indicate that adhesin Hp0410 is a promising candidate vaccine antigen, and recombinant L. acidophilus expressing Hp0410 is likely to constitute an effective, low-cost, live bacterial vaccine against H. pylori.

A dominant CD4(+) T-cell response to Helicobacter pylori reduces risk for gastric disease in humans

BACKGROUND & AIMS

Immunodominance is an important feature of antiviral, antitumor, and antibacterial cellular immune responses, but it is not well demonstrated in the immune responses against Helicobacter pylori. Antigen-specific CD4(+) T cells protect mice against infection with H pylori. We investigated the immunodominant CD4(+) T-cell response to neuraminyllactose-binding hemagglutinin (HpaA), which is a conserved, H pylori-specific colonization factor that is being investigated as an antigen for vaccination strategies.

METHODS

HpaA-specific CD4(+) T cells were expanded with autologous peripheral blood mononuclear cells that had been incubated with recombinant HpaA and characterized using overlapping synthetic peptides. We compared the percentage of CD4(+) T cells with specificity for HpaA(88-100), restricted to HLA-DRB1*1501, among 59 H pylori-infected subjects with different gastric diseases.

RESULTS

We identified and characterized several immunodominant CD4(+) T-cell epitopes derived from HpaA. The immunodominant CD4(+) T-cell responses specific to HpaA(88-100) were observed in most H pylori-infected individuals who expressed HLA-DRB1*1501 and were significantly more abundant in patients with less severe diseases (P < .05).

CONCLUSIONS

The HLA-DRB1*1501-restricted immunodominant CD4(+) T-cell response to HpaA(88-100) is associated with reduced risk of severe gastric diseases. Further study of these and other immunodominant CD4(+) T-cell responses to H pylori will provide insight into mechanisms of protective immunity and aid in vaccine design.

Evolution in an oncogenic bacterial species with extreme genome plasticity: Helicobacter pylori East Asian genomes

BACKGROUND

The genome of Helicobacter pylori, an oncogenic bacterium in the human stomach, rapidly evolves and shows wide geographical divergence. The high incidence of stomach cancer in East Asia might be related to bacterial genotype. We used newly developed comparative methods to follow the evolution of East Asian H. pylori genomes using 20 complete genome sequences from Japanese, Korean, Amerind, European, and West African strains.

RESULTS

A phylogenetic tree of concatenated well-defined core genes supported divergence of the East Asian lineage (hspEAsia; Japanese and Korean) from the European lineage ancestor, and then from the Amerind lineage ancestor. Phylogenetic profiling revealed a large difference in the repertoire of outer membrane proteins (including oipA, hopMN, babABC, sabAB and vacA-2) through gene loss, gain, and mutation. All known functions associated with molybdenum, a rare element essential to nearly all organisms that catalyzes two-electron-transfer oxidation-reduction reactions, appeared to be inactivated. Two pathways linking acetyl~CoA and acetate appeared intact in some Japanese strains. Phylogenetic analysis revealed greater divergence between the East Asian (hspEAsia) and the European (hpEurope) genomes in proteins in host interaction, specifically virulence factors (tipα), outer membrane proteins, and lipopolysaccharide synthesis (human Lewis antigen mimicry) enzymes. Divergence was also seen in proteins in electron transfer and translation fidelity (miaA, tilS), a DNA recombinase/exonuclease that recognizes genome identity (addA), and DNA/RNA hybrid nucleases (rnhAB). Positively selected amino acid changes between hspEAsia and hpEurope were mapped to products of cagA, vacA, homC (outer membrane protein), sotB (sugar transport), and a translation fidelity factor (miaA). Large divergence was seen in genes related to antibiotics: frxA (metronidazole resistance), def (peptide deformylase, drug target), and ftsA (actin-like, drug target).

CONCLUSIONS

These results demonstrate dramatic genome evolution within a species, especially in likely host interaction genes. The East Asian strains appear to differ greatly from the European strains in electron transfer and redox reactions. These findings also suggest a model of adaptive evolution through proteome diversification and selection through modulation of translational fidelity. The results define H. pylori East Asian lineages and provide essential information for understanding their pathogenesis and designing drugs and therapies that target them.

Helicobacter pylori AlpA and AlpB bind host laminin and influence gastric inflammation in gerbils

Helicobacter pylori persistently colonizes humans, causing gastritis, ulcers, and gastric cancer. Adherence to the gastric epithelium has been shown to enhance inflammation, yet only a few H. pylori adhesins have been paired with targets in host tissue. The alpAB locus has been reported to encode adhesins involved in adherence to human gastric tissue. We report that abrogation of H. pylori AlpA and AlpB reduces binding of H. pylori to laminin while expression of plasmid-borne alpA or alpB confers laminin-binding ability to Escherichia coli. An H. pylori strain lacking only AlpB is also deficient in laminin binding. Thus, we conclude that both AlpA and AlpB contribute to H. pylori laminin binding. Contrary to expectations, the H. pylori SS1 mutant deficient in AlpA and AlpB causes more severe inflammation than the isogenic wild-type strain in gerbils. Identification of laminin as the target of AlpA and AlpB will facilitate future investigations of host-pathogen interactions occurring during H. pylori infection.

Genome sequence of Helicobacter suis supports its role in gastric pathology

Helicobacter (H.) suis has been associated with chronic gastritis and ulcers of the pars oesophagea in pigs, and with gastritis, peptic ulcer disease and gastric mucosa-associated lymphoid tissue lymphoma in humans. In order to obtain better insight into the genes involved in pathogenicity and in the specific adaptation to the gastric environment of H. suis, a genome analysis was performed of two H. suis strains isolated from the gastric mucosa of swine. Homologs of the vast majority of genes shown to be important for gastric colonization of the human pathogen H. pylori were detected in the H. suis genome. H. suis encodes several putative outer membrane proteins, of which two similar to the H. pylori adhesins HpaA and HorB. H. suis harbours an almost complete comB type IV secretion system and members of the type IV secretion system 3, but lacks most of the genes present in the cag pathogenicity island of H. pylori. Homologs of genes encoding the H. pylori neutrophil-activating protein and γ-glutamyl transpeptidase were identified in H. suis. H. suis also possesses several other presumptive virulence-associated genes, including homologs for mviN, the H. pylori flavodoxin gene, and a homolog of the H. pylori vacuolating cytotoxin A gene. It was concluded that although genes coding for some important virulence factors in H. pylori, such as the cytotoxin-associated protein (CagA), are not detected in the H. suis genome, homologs of other genes associated with colonization and virulence of H. pylori and other bacteria are present.

Form equals function? Bacterial shape and its consequences for pathogenesis

Bacteria exhibit a wide variety of morphologies. This could simply be a consequence of an elaboration of bacterial cellular architecture akin to the famous decorative but not structurally essential Spandrels in the Basilica di San Marco in Venice that are a side-effect of an adaptation, rather than a direct product of natural selection. However, it is more likely that particular morphologies facilitate a specific function in cellular physiology. Two recent publications including one in this issue of Molecular Microbiology and another in Cell provide new insights into the molecular basis for the helical shape of the bacterium Helicobacter pylori and the role of this shape in pathogenesis. They identify a novel endopeptidase that is necessary to generate the helical shape by processing the peptidoglycan and report that catalytically inactive mutants lead to defects in colonization that appear to be independent of an effect on cellular motility. Here, we put these findings in the context of some of what is known about peptidoglycan and cell shape and suggest that the role of this endopeptidase in forming coccoid morphology may be critical for pathogenesis.

Protection against Helicobacter pylori infection by a trivalent fusion vaccine based on a fragment of urease B-UreB414

A multivalent fusion vaccine is a promising option for protection against Helicobacter pylori infection. In this study, UreB414 was identified as an antigenic fragment of urease B subunit (UreB) and it induced an antibody inhibiting urease activity. Immunization with UreB414 partially protected mice from H. pylori infection. Furthermore, a trivalent fusion vaccine was constructed by genetically linking heat shock protein A (HspA), H. pylori adhesin A (HpaA), and UreB414, resulting in recombinant HspA-HpaA-UreB414 (rHHU). Its protective effect against H. pylori infection was tested in BALB/c mice. Oral administration of rHHU significantly protected mice from H. pylori infection, which was associated with H. pylori-specific antibody production and Th1/Th2-type immune responses. The results show that a trivalent fusion vaccine efficiently combats H. pylori infection, and that an antigenic fragment of the protein can be used instead of the whole protein to construct a multivalent vaccine.

Interferon-gamma secretion is induced in IL-12 stimulated human NK cells by recognition of Helicobacter pylori or TLR2 ligands

Helicobacter pylori induce a chronic inflammation in the human gastric mucosa characterized by increased production of interferon-gamma (IFN-γ). The presence of natural killer (NK) cells in the human gastric mucosa and the ability of NK cells to produce IFN-γ suggest an important role of NK cells in the immune response directed towards H. pylori infection. Since NK cells previously have been shown to respond to bacterial components with IFN-γ production, we investigated the mechanisms for the recognition of H. pylori. We found that inhibition of MyD88 homodimerization resulted in decreased production of IFN-γ and that inhibition of the p38 MAPK decreased the production as well as the secretion of IFN-γ. Further studies indicated an involvement of Toll-like receptors (TLRs), in particular TLR2. Finally, we showed that the H. pylori specific membrane bound lipoprotein HpaA induced IFN-γ production from NK cells through recognition by TLR2. In conclusion, we suggest an involvement of TLR2 in the recognition of H. pylori by human NK cells and that HpaA is a TLR2 ligand important for recognition.