Bacterial chemotaxis modulates host cell apoptosis to establish a T-helper cell, type 17 (Th17)-dominant immune response in Helicobacter pylori infection. Proc Natl Acad Sci U S A. 2011;108:19749-19754. [PMID: 22106256 DOI: 10.1073/pnas.1104598108]

Discovery of Type IV filament membrane alignment complex homologs in H. pylori that promote soft-agar migration

The stomach pathogen Helicobacter pylori utilizes two scaffold proteins, CheW and CheV1, to build critical chemotaxis arrays. Chemotaxis helps bacteria establish and maintain infection. Mutants lacking either of these chemotaxis proteins have different soft agar phenotypes: deletion of cheW creates non-chemotactic strains, while deletion of cheV1 results in 50% loss of chemotaxis. In this work, we characterized the cheV1 deletion mutant phenotype in detail. cheV1 deletion mutants had poor soft-agar migration initially, but regained migration ability over time. This improved bacterial migration was stable, suggesting a genetic suppressor phenotype, termed Che+. Whole-genome sequencing analysis of four distinct cheV1 Che+ strains revealed single nucleotide polymorphisms (SNPs) in a common gene, HPG27_252 (HP0273). These SNPs were predicted to truncate the encoded protein. To confirm the role of HPG27_252 in the cheV1 phenotype, we created a targeted deletion of HPG27_252 and found that loss of HPG27_252 enhanced soft-agar migration. HPG27_252 and CheV1 appear to interact directly, based on bacterial two-hybrid analysis. HPG27_252 is predicted to encode a 179 amino acid, 21 kDa protein annotated as a hypothetical protein. Computational analysis revealed this protein to be a remote homolog of the PilO Type IV filament membrane alignment complex protein. Although H. pylori is not known to possess Type IV filaments, our analysis showed it retains an operon of genes for homologs of PilO, PilN, and PilM, but does not possess other Type IV pili genes. Our data suggest the PilO homolog plays a role in regulating H. pylori chemotaxis and motility, suggesting new ideas about evolutionary steps for controlling migration through semi-solid media.

Helicobacter pylori initiates successful gastric colonization by utilizing L-lactate to promote complement resistance

The complement system has long been appreciated for its role in bloodborne infections, but its activities in other places, including the gastrointestinal tract, remain elusive. Here, we report that complement restricts gastric infection by the pathogen Helicobacter pylori. This bacterium colonized complement-deficient mice to higher levels than wild-type counterparts, particularly in the gastric corpus region. H. pylori uses uptake of the host molecule L-lactate to create a complement-resistant state that relies on blocking the deposition of the active complement C4b component on H. pylori's surface. H. pylori mutants unable to achieve this complement-resistant state have a significant mouse colonization defect that is largely corrected by mutational removal of complement. This work highlights a previously unknown role for complement in the stomach, and has revealed an unrecognized mechanism for microbial-derived complement resistance.

Helicobacter pylori Chronic-Stage Inflammation Undergoes Fluctuations That Are Altered in tlpA Mutants

Helicobacter pylori colonizes half of the world's population and is responsible for a significant disease burden by causing gastritis, peptic ulcers, and gastric cancer. The development of host inflammation drives these diseases, but there are still open questions in the field about how H. pylori controls this process. We characterized H. pylori inflammation using an 8-month mouse infection time course and comparison of the wild type (WT) and a previously identified mutant lacking the TlpA chemoreceptor that causes elevated inflammation. Our work shows that H. pylori chronic-stage corpus inflammation undergoes surprising fluctuations, with changes in Th17 and eosinophil numbers. The H. pylori tlpA mutant changed the inflammation temporal characteristics, resulting in different inflammation from the wild type at some time points. tlpA mutants have equivalent total and gland colonization in late-stage infections. During early infection, in contrast, they show elevated gland and total colonization compared to those by WT. Our results suggest the chronic inflammation setting is dynamic and may be influenced by colonization properties of early infection.

Interdomain Linkers Regulate Histidine Kinase Activity by Controlling Subunit Interactions

Bacterial chemoreceptors regulate the cytosolic multidomain histidine kinase CheA through largely unknown mechanisms. Residue substitutions in the peptide linkers that connect the P4 kinase domain to the P3 dimerization and P5 regulatory domain affect CheA basal activity and activation. To understand the role that these linkers play in CheA activity, the P3-to-P4 linker (L3) and P4-to-P5 linker (L4) were extended and altered in variants of Thermotoga maritima (Tm) CheA. Flexible extensions of the L3 and L4 linkers in CheA-LV1 (linker variant 1) allowed for a well-folded kinase domain that retained wild-type (WT)-like binding affinities for nucleotide and normal interactions with the receptor-coupling protein CheW. However, CheA-LV1 autophosphorylation activity registered ∼50-fold lower compared to WT. Neither a WT nor LV1 dimer containing a single P4 domain could autophosphorylate the P1 substrate domain. Autophosphorylation activity was rescued in variants with extended L3 and L4 linkers that favor helical structure and heptad spacing. Autophosphorylation depended on linker spacing and flexibility and not on sequence. Pulse-dipolar electron-spin resonance (ESR) measurements with spin-labeled adenosine 5'-triphosphate (ATP) analogues indicated that CheA autophosphorylation activity inversely correlated with the proximity of the P4 domains within the dimers of the variants. Despite their separation in primary sequence and space, the L3 and L4 linkers also influence the mobility of the P1 substrate domains. In all, interactions of the P4 domains, as modulated by the L3 and L4 linkers, affect domain dynamics and autophosphorylation of CheA, thereby providing potential mechanisms for receptors to regulate the kinase.

The First Evidence of Bacterial Foci in the Hair Part and Dermal Papilla of Scalp Hair Follicles: A Pilot Comparative Study in Alopecia Areata

The role of the microbiome in hair follicle (HF) growth represents a growing field of research. Here, we studied the bacterial population in the scalp hair follicles of subjects with alopecia areata (AA). Two Healthy and two AA subjects, respectively (20−60 years old), were enrolled and studied regarding the microbial community in the subepidermal scalp compartments by means of a 4-mm biopsy punch. Samples were examined by 16S sequencing, histochemical staining (Gram’s method), and transmission electron microscopy (TEM). Bacterial foci were observed in the AA subjects’ follicles with both the two adopted complementary approaches (electron microscopy and Gram staining). Significant (p < 0.05) differences were also found in the three-layer biopsy samples (p < 0.05) regarding the bacterial population. In particular, in the deep epidermis and dermis levels, a significant (p < 0.05) lower abundance of Firmicutes and a higher abundance of Proteobacteria were found in AA samples compared to the healthy control. Firmicutes also showed a significant (p < 0.05) lower abundance in hypodermis in AA subjects. In addition, Enterobacteriaceae and the genera Streptococcus, Gemella, Porphyromonas, and Granulicatella were relatively more abundant in AA groups at the deep epidermis level. The Staphylococcus and Flavobacterium genera were significantly less abundant in AA samples than in controls in all three-layer biopsy samples (p < 0.05). In contrast, Veillonella and Neisseriaceae were relatively more abundant in the healthy control group compared to the AA sample. Therefore, higher alpha diversity was observed in all three-layer biopsy samples of AA patients compared to the control. In conclusion, our data suggest that tAA could be defined as a “hair disease associated with dysregulated microbiome-immunity axis of hair follicles”.

Lichen Planopilaris: The first biopsy layer microbiota inspection

Lichen Planopilaris (LPP) is a lymphatic disease affecting the scalp that is characterized by a chronic and destructive inflammation process, named as ‘cicatricial alopecia’ in which the hair follicles are targeted and may involve predominantly lymphocytes or neutrophils. Scalp and biopsy layers have never been used to investigate microbial community composition and its relative taxa abundances in LPP. We sought to examine the significant taxa of this chronic relapsing inflammatory skin disease, together with inspect the existing connections with metabolic pathways featuring this microbial community. We used a multilevel analysis based on 16S rRNA marker sequencing in order to detect OTU abundances in pathologic/healthy samples, real time PCR for measuring the levels of IL-23 interleukin expression and urinary metabolomics to find out volatile organic metabolites (VOMs). By using a linear regression model, we described peculiar taxa that significantly differentiated LPP and healthy samples. We inspected taxa abundances and interleukin mRNA levels and the Microbacteriaceae family resulted negatively correlated with the IL-23 expression. Moreover, starting from 16S taxa abundances, we predicted the metabolic pathways featuring this microbial community. By inspecting microbial composition, sample richness, metabolomics profiles and the relative metabolic pathways in a cohort of LPP and healthy samples we deepened the contribution of significant taxa that are connected to inflammation maintenance and microbiota plasticity in LPP pathology.

Designing and development of epitope-based vaccines against Helicobacter pylori

Helicobacter pylori infection is the principal cause of serious diseases (e.g. gastric cancer and peptic ulcers). Antibiotic therapy is an inadequate strategy in H. pylori eradication because of which vaccination is an inevitable approach. Despite the presence of countless vaccine candidates, current vaccines in clinical trials have performed with poor efficacy which makes vaccination extremely challenging. Remarkable advancements in immunology and pathogenic biology have provided an appropriate opportunity to develop various epitope-based vaccines. The fusion of proper antigens involved in different aspects of H. pylori colonization and pathogenesis as well as peptide linkers and built-in adjuvants results in producing epitope-based vaccines with excellent therapeutic efficacy and negligible adverse effects. Difficulties of the in vitro culture of H. pylori, high genetic variation, and unfavourable immune responses against feeble epitopes in the complete antigen are major drawbacks of current vaccine strategies that epitope-based vaccines may overcome. Besides decreasing the biohazard risk, designing precise formulations, saving time and cost, and induction of maximum immunity with minimum adverse effects are the advantages of epitope-based vaccines. The present article is a comprehensive review of strategies for designing and developing epitope-based vaccines to provide insights into the innovative vaccination against H. pylori.

The dCache Chemoreceptor TlpA of Helicobacter pylori Binds Multiple Attractant and Antagonistic Ligands via Distinct Sites

The Helicobacter pylori chemoreceptor TlpA plays a role in dampening host inflammation during chronic stomach colonization. TlpA has a periplasmic dCache_1 domain, a structure that is capable of sensing many ligands; however, the only characterized TlpA signals are arginine, bicarbonate, and acid. To increase our understanding of TlpA’s sensing profile, we screened for diverse TlpA ligands using ligand binding arrays. TlpA bound seven ligands with affinities in the low- to middle-micromolar ranges. Three of these ligands, arginine, fumarate, and cysteine, were TlpA-dependent chemoattractants, while the others elicited no response. Molecular docking experiments, site-directed point mutants, and competition surface plasmon resonance binding assays suggested that TlpA binds ligands via both the membrane-distal and -proximal dCache_1 binding pockets. Surprisingly, one of the nonactive ligands, glucosamine, acted as a chemotaxis antagonist, preventing the chemotaxis response to chemoattractant ligands, and acted to block the binding of ligands irrespective of whether they bound the membrane-distal or -proximal dCache_1 subdomains. In total, these results suggest that TlpA senses multiple attractant ligands as well as antagonist ones, an emerging theme in chemotaxis systems.

Blue light emitting diodes enhance the antivirulence effects of Curcumin against Helicobacter pylori

Introduction. Growing concern about the increasing frequency of resistance of Helicobacter pylori to the available antimicrobial agents worldwide has encouraged the search for new strategies in treating and eradicating H. pylori infections. Endoscopic blue-light therapy has been used in patients with H. pylori gastritis with limited success due to subsequent repopulation with H. pylori. Clinical trials using Curcumin could not eradicate infection either.Aim. We studied the effect of blue light emitting diodes (LEDs) in conjunction with Curcumin on H. pylori, since this has not been previously reported.Methodology. We examined the effect of Curcumin with and without irradiation with blue LEDs on the viability of H. pylori and four key factors important for colonization and establishment of H. pylori infection, namely urease production, motility, adhesion and biofilm formation.Results. We found that a combination of Curcumin and blue LEDs caused significant reductions in viability, urease production, motility, haemagglutination activity, as well as increased disruption of mature preformed biofilms of H. pylori, in comparison to Curcumin alone (P<0.0001), at sublethal concentrations of Curcumin.Conclusion. Targeting the virulence factors of H. pylori with blue LED photoactivated Curcumin would theoretically cripple this pathogen from colonizing and causing tissue damage and perhaps overcome the problem of repopulation with H. pylori that often occurs following endoscopic blue-light therapy.

Predictive Metagenomic Profiling, Urine Metabolomics, and Human Marker Gene Expression as an Integrated Approach to Study Alopecia Areata

Involvement of the microbiome in many different scalp conditions has been investigated over the years. Studies on the role of the scalp microbiome in specific diseases, such as those involving hair growth alterations like non-cicatricial [androgenetic alopecia (AGA), alopecia areata (AA)] and cicatricial alopecia lichen planopilaris, are of major importance. In the present work, we highlighted the differences in microbial populations inhabiting the scalp of AA subjects and a healthy sample cohort by using an integrated approach relying on metagenomic targeted 16S sequencing analysis, urine metabolomics, and human marker gene expression. Significant differences in genera abundances (p < 0.05) were found in the hypodermis and especially the dermis layer. Based on 16S sequencing data, we explored the differences in predicted KEGG pathways and identified some significant differences in predicted pathways related to the AA pathologic condition such as flagellar, assembly, bacterial chemotaxis, mineral absorption, ABC transporters, cellular antigens, glycosaminoglycan degradation, lysosome, sphingolipid metabolism, cell division, protein digestion and absorption, and energy metabolism. All predicted pathways were significantly enhanced in AA samples compared to expression in healthy samples, with the exceptions of mineral absorption, and ABC transporters. We also determined the expression of TNF-α, FAS, KCNA3, NOD-2, and SOD-2 genes and explored the relationships between human gene expression levels and microbiome composition by Pearson's correlation analysis; here, significant correlations both positive (SOD vs. Staphylococcus, Candidatus Aquiluna) and negative (FAS and SOD2 vs. Anaerococcus, Neisseria, and Acinetobacter) were highlighted. Finally, we inspected volatile organic metabolite profiles in urinary samples and detected statistically significant differences (menthol, methanethiol, dihydrodehydro-beta-ionone, 2,5-dimethylfuran, 1,2,3,4, tetrahydro-1,5,7-trimethylnapthalene) when comparing AA and healthy subject groups. This multiple comparison approach highlighted potential traits associated with AA and their relationship with the microbiota inhabiting the scalp, opening up novel therapeutic interventions in such kind of hair growth disorders mainly by means of prebiotics, probiotics, and postbiotics.

Inflammation, Immunity, and Vaccine Development for the Gastric Pathogen Helicobacter pylori

It has been over 30 years since a link was established between H. pylori infection of the gastric mucosa and the development of chronic gastric diseases. Research in rodent models supported by data from human tissue demonstrated that the host immune response to H. pylori is limited by host regulatory T cells. Immunization has been shown to induce a potent Th1- and Th17-mediated immune response capable of eradicating or at least significantly reducing the bacterial load of H. pylori in the stomach in small animal models. These results have not translated well to humans. Clinical trials employing many of the strategies used in rodents for oral immunization including the use of a mucosal adjuvant such as Escherichia coli LT or delivery by attenuated enteric bacteria have failed to limit H. pylori infection and have highlighted the potential toxicity of exotoxin-based mucosal adjuvants. A recent study, however, utilizing a recombinant fusion protein of H. pylori urease and the subunit B of E. coli LT, was performed on over 4000 children. Efficacy of over 70% was demonstrated against naturally acquired infection compared to control volunteers one year post-immunization. Efficacy was reduced, but still above 50% at three years. This study provided new insight into the strategies for developing an improved vaccine for widespread use in countries with high infection rates and where gastric cancer (GC) remains one of the most common causes of death due to cancer.

Stromal C-type lectin receptor COLEC12 integrates H. pylori, PGE2-EP2/4 axis and innate immunity in gastric diseases

Tissue stroma is known to be important in regulating Hp-mediated inflammation, but its interaction with Hp and dendritic cells (DCs) remains to be determined. To this end, the potential crosstalk between H. pylori (Hp) infected gastric stromal cells (Hp-GSCs) and DCs was investigated. Primary GSCs from cancerous and adjacent normal tissues were generated from gastric cancer patients, and monocyte-derived DCs were obtained from healthy individuals. Levels of cytokines and prostaglandin E₂ (PGE₂) were measured by ELISA, and C-type lectin expression in GSCs was assessed by flow cytometry and immunohistochemistry. In a trans-well co-culture system, significantly upregulated DC-derived IL-23 expression was found when DCs were co-cultured with Hp-infected GSCs (Hp-GSCs). Further, PGE₂ from Hp-GSCs was discovered to possess the priming effect, which could be inhibited by anti-COLEC12 (Collectin subfamily member 12) Abs, COLEC12 knockdown or when alpha3-fucosyltransferase-null (futB; HP0651) strain of Hp was used. Also, the expression of COLEC12 was co-localized with CD90⁺ stromal cells in cancerous tissues. Hp-GSCs-conditioned DCs were able to induce the expression of IL-17 from CD4⁺ T cells, which could be inhibited by IL-23-neutralizing Abs. These results suggested the importance of COLEC12 as a receptor involved in Hp-stromal cell interaction and its subsequent conditioning effect on DCs.

Immunodominant antigens that induce Th1 and Th17 responses protect mice against Helicobacter pylori infection

Helicobacter pylori has infected more than half of the world's population, causing gastritis, gastric ulcers, gastric mucosa-associated lymphoid tissue lymphoma and gastric cancer. The oral recombinant Helicobacter pylori vaccine currently used has made great progress in addressing this problem, however, its efficacy and longevity still need to be improved. Th1 and Th17 cells play essential roles in local protection against Helicobacter pylori in the stomach mucosa. Additionally, protective immunodominant antigens are the preferred for a vaccine. In this work, Helicobacter pylori whole cell lysate was separated into 30 groups based on molecular weight by molecular sieve chromatography. The group best promoting CD4 T cells proliferation was selected and evaluated by immunization. The detail proteins were then analyzed by LC-MS/MS and expressed in Escherichia coli. Eleven proteins were selected and the dominant ones were demonstrated. As a result, three protective immunodominant antigens, inosine 5'-monophosphate dehydrogenase, type II citrate synthase, and urease subunit beta, were selected from Helicobacter pylori whole cell. Two of them (inosine 5'-monophosphate dehydrogenase and type II citrate synthase) were newly identified, and one (urease subunit beta) was confirmed as previously reported. The mixture of the three antigens showed satisfactory protective efficiency, with significant lower H. pylori colonization level (P < 0.001) and stronger Th1 (P < 0.001) and Th17 (P < 0.001) responses than PBS control group. Thus, inosine 5'-monophosphate dehydrogenase, type II citrate synthase, and urease subunit beta are three protective antigens inducing dominant Th1 and Th17 responses to defend against Helicobacter pylori infection.

Colonization, localization, and inflammation: the roles of H. pylori chemotaxis in vivo

Helicobacter pylori is a Gram-negative bacterium that infects half of the world's population, causing gastritis, peptic ulcers, and gastric cancer. To establish chronic stomach infection, H. pylori utilizes chemotaxis, driven by a conserved signal transduction system. Chemotaxis allows H. pylori to sense an array of environmental and bacterial signals within the stomach, guiding its motility towards its preferred niche within the gastric mucosa and glands. Fine-tuned localization, regulated by the chemotaxis system, enables robust colonization during the acute stage of infection. During chronic infection, chemotaxis helps maintain bacterial populations and modulates the host immune response. Given its importance in host colonization and disease, chemotaxis is an attractive target for future treatments against H. pylori infections.

SalmoNet, an integrated network of ten Salmonella enterica strains reveals common and distinct pathways to host adaptation

Salmonella enterica is a prominent bacterial pathogen with implications on human and animal health. Salmonella serovars could be classified as gastro-intestinal or extra-intestinal. Genome-wide comparisons revealed that extra-intestinal strains are closer relatives of gastro-intestinal strains than to each other indicating a parallel evolution of this trait. Given the complexity of the differences, a systems-level comparison could reveal key mechanisms enabling extra-intestinal serovars to cause systemic infections. Accordingly, in this work, we introduce a unique resource, SalmoNet, which combines manual curation, high-throughput data and computational predictions to provide an integrated network for Salmonella at the metabolic, transcriptional regulatory and protein-protein interaction levels. SalmoNet provides the networks separately for five gastro-intestinal and five extra-intestinal strains. As a multi-layered, multi-strain database containing experimental data, SalmoNet is the first dedicated network resource for Salmonella. It comprehensively contains interactions between proteins encoded in Salmonella pathogenicity islands, as well as regulatory mechanisms of metabolic processes with the option to zoom-in and analyze the interactions at specific loci in more detail. Application of SalmoNet is not limited to strain comparisons as it also provides a Salmonella resource for biochemical network modeling, host-pathogen interaction studies, drug discovery, experimental validation of novel interactions, uncovering new pathological mechanisms from emergent properties and epidemiological studies. SalmoNet is available at http://salmonet.org.

Candidate genes on murine chromosome 8 are associated with susceptibility to Staphylococcus aureus infection in mice and are involved with Staphylococcus aureus septicemia in humans

We previously showed that chromosome 8 of A/J mice was associated with susceptibility to S. aureus infection. However, the specific genes responsible for this susceptibility are unknown. Chromosome substitution strain 8 (CSS8) mice, which have chromosome 8 from A/J but an otherwise C57BL/6J genome, were used to identify the genetic determinants of susceptibility to S. aureus on chromosome 8. Quantitative trait loci (QTL) mapping of S. aureus-infected N2 backcross mice (F1 [C8A] × C57BL/6J) identified a locus 83180780–88103009 (GRCm38/mm10) on A/J chromosome 8 that was linked to S. aureus susceptibility. All genes on the QTL (n~ 102) were further analyzed by three different strategies: 1) different expression in susceptible (A/J) and resistant (C57BL/6J) mice only in response to S. aureus, 2) consistently different expression in both uninfected and infected states between the two strains, and 3) damaging non-synonymous SNPs in either strain. Eleven candidate genes from the QTL region were significantly differently expressed in patients with S. aureus infection vs healthy human subjects. Four of these 11 genes also exhibited significantly different expression in S. aureus-challenged human neutrophils: Ier2, Crif1, Cd97 and Lyl1. CD97 ligand binding was evaluated within peritoneal neutrophils from A/J and C57BL/6J. CD97 from A/J had stronger CD55 but weaker integrin α5β1 ligand binding as compared with C57BL/6J. Because CD55/CD97 binding regulates immune cell activation and cytokine production, and integrin α5β1 is a membrane receptor for fibronectin, which is also bound by S. aureus, strain-specific differences could contribute to susceptibility to S. aureus. Down-regulation of Crif1 with siRNA was associated with increased host cell apoptosis among both naïve and S. aureus-infected bone marrow-derived macrophages. Specific genes in A/J chromosome 8, including Cd97 and Crif1, may play important roles in host defense against S. aureus.

Spatial and Temporal Shifts in Bacterial Biogeography and Gland Occupation during the Development of a Chronic Infection

Gland colonization may be one crucial route for bacteria to maintain chronic gastrointestinal infection. We developed a quantitative gland isolation method to allow robust bacterial population analysis and applied it to the gastric pathobiont Helicobacter pylori. After infections in the murine model system, H. pylori populations multiply both inside and outside glands in a manner that requires the bacteria to be motile and chemotactic. H. pylori is able to achieve gland densities averaging 25 to 40 bacteria/gland after 2 to 4 weeks of infection. After 2 to 4 weeks of infection, a primary infection leads to colonization resistance for a secondary infection. Nonetheless, about ~50% of the glands remained unoccupied, suggesting there are as-yet unappreciated parameters that prevent gastric gland colonization. During chronic infections, H. pylori populations collapsed to nearly exclusive gland localization, to an average of <8 bacteria/gland, and only 10% of glands occupied. We analyzed an H. pylori chemotaxis mutant (Che⁻) to gain mechanistic insight into gland colonization. Che⁻ strains had a severe inability to spread to new glands and did not protect from a secondary infection but nonetheless achieved a chronic gland colonization state numerically similar to that of the wild type. Overall, our analysis shows that bacteria undergo substantial population dynamics on the route to chronic colonization, that bacterial gland populations are maintained at a low level during chronic infection, and that established gland populations inhibit subsequent colonization. Understanding the parameters that promote chronic colonization will allow the future successful design of beneficial microbial therapeutics that are able to maintain long-term mammalian colonization.

Many bacteria have an impressive ability to stay in the gastrointestinal tract for decades despite ongoing flow and antimicrobial attacks. How this staying power is achieved is not fully understood, but it is important to understand as scientists plan so-called designer microbiomes. The gastrointestinal tract is lined with repeated invaginations called glands, which may provide one niche for chronic colonization. We developed a quantitative gland isolation method to allow robust and efficient bacterial population analysis and applied it to the gastric pathogen Helicobacter pylori. Bacterial populations increased inside and outside glands at early time points but were found exclusively within glands during late time points in the chronic state. H. pylori required the ability to swim to move to new glands. Last, a fit gland bacterial population leads to colonization resistance of a second one. Our approach identified previously unappreciated aspects of gland occupation, supporting the idea that glands are the desired niche for stable, chronic colonization.

Localisation and protein-protein interactions of the Helicobacter pylori taxis sensor TlpD and their connection to metabolic functions

The Helicobacter pylori energy sensor TlpD determines tactic behaviour under low energy conditions and is important in vivo. We explored protein-protein interactions of TlpD and their impact on TlpD localisation and function. Pull-down of tagged TlpD identified protein interaction partners of TlpD, which included the chemotaxis histidine kinase CheAY2, the central metabolic enzyme aconitase (AcnB) and the detoxifying enzyme catalase (KatA). We confirmed that KatA and AcnB physically interact with TlpD. While the TlpD-dependent behavioural response appeared not influenced in the interactor mutants katA and acnB in steady-state behavioural assays, acetone carboxylase subunit (acxC) mutant behaviour was altered. TlpD was localised in a bipolar subcellular pattern in media of high energy. We observed a significant change in TlpD localisation towards the cell body in cheAY2-, catalase- or aconitase-deficient bacteria or in bacteria incubated under low energy conditions, including oxidative stress or respiratory inhibition. Inactivation of tlpD resulted in an increased sensitivity to iron limitation and oxidative stress and influenced the H. pylori transcriptome. Oxidative stress, iron limitation and overexpressing the iron-sulfur repair system nifSU altered TlpD-dependent behaviour. We propose that TlpD localisation is instructed by metabolic activity and protein interactions, and its sensory activity is linked to iron-sulfur cluster integrity.

Association of Pneumococcal Carriage and Expression of Foxp3+ Regulatory T Cells and Th17 Cells in the Adenoids of Children

BACKGROUND

Pneumococcal carriage in the nasopharynx is a primary means of transmission and a necessary prerequisite for pneumococcal disease.

OBJECTIVES

We analyzed the relationship between expressions of Foxp3+ regulatory T (Treg) cells and Th17 cells, and pneumococcal carriage in the adenoids of children who were either positive or negative for pneumococci.

METHODS

We collected adenoidal tissue and nasopharyngeal swab samples from children undergoing an adenoidectomy. Adenoidal mononuclear cells were isolated, cultured and then stimulated with culture concentrated supernatant (CCS) obtained from a D39 bacterial strain.

RESULTS

Foxp3+ Treg cells were upregulated and Th17 cells were downregulated in populations of adenoidal mononuclear cells obtained from the pneumococcus-positive group. Following CCS stimulation, the increment in Foxp3+ Treg cells in the pneumococcus-positive group was significantly greater than that in the pneumococcus-negative group, while the increment in Th17 cells was less as compared to that in the pneumococcus-negative group. These results were consistent with variations in levels of Foxp3 mRNA and retinoic acid receptor-related orphan receptor-γt mRNA in adenoidal mononuclear cells. Levels of IL-17A and IL-6 in adenoid tissue were higher in the pneumococcus-negative group, and the levels of TGF-β in adenoid tissue were lower in the pneumococcus-negative group compared to the pneumococcus-positive group. Pneumococcal carriage in children was closely associated with the expressions of Foxp3+ Treg and Th17 cells in the adenoid.

CONCLUSION

Upregulation of Foxp3+ Treg cells might downregulate the production of Th17 cells in the adenoid, resulting in decreased scavenging of Streptococcus pneumoniae and chronic pneumococcal carriage.

In vitro expansion of human gastric epithelial stem cells and their responses to bacterial infection

BACKGROUND & AIMS

We previously established long-term, 3-dimensional culture of organoids from mouse tissues (intestine, stomach, pancreas, and liver) and human intestine and pancreas. Here we describe conditions required for long-term 3-dimensional culture of human gastric stem cells. The technology can be applied to study the epithelial response to infection with Helicobacter pylori.

METHODS

We generated organoids from surgical samples of human gastric corpus. Culture conditions were developed based on those for the mouse gastric and human intestinal systems. We used microinjection to infect the organoids with H pylori. Epithelial responses were measured using microarray and quantitative polymerase chain reaction analyses.

RESULTS

Human gastric cells were expanded indefinitely in 3-dimensional cultures. We cultured cells from healthy gastric tissues, single-sorted stem cells, or tumor tissues. Organoids maintained many characteristics of their respective tissues based on their histology, expression of markers, and euploidy. Organoids from healthy tissue expressed markers of 4 lineages of the stomach and self-organized into gland and pit domains. They could be directed to specifically express either lineages of the gastric gland, or the gastric pit, by addition of nicotinamide and withdrawal of WNT. Although gastric pit lineages had only marginal reactions to bacterial infection, gastric gland lineages mounted a strong inflammatory response.

CONCLUSIONS

We developed a system to culture human gastric organoids. This system can be used to study H pylori infection and other gastric pathologies.

CsrA regulates Helicobacter pylori J99 motility and adhesion by controlling flagella formation

BACKGROUND

Motility mediated by the flagella of Helicobacter pylori has been shown to be required for normal colonization and is thought to be important for the bacteria to move toward the gastric mucus in niches adjacent to the epithelium. Barnard et al. showed that CsrA appears to be necessary for full motility and the ability to infect mice, but its mechanism of regulation is still unclear.

METHODS

Motility and cell adhesion ability were determined in wild-type, csrA mutant, and revertant J99 strains. The bacterial shape and flagellar structure were evaluated by transmission electron microscopy. The expression of two major flagellins, flaA/flaB, and the alternative sigma factor rpoN (σ(54)) were determined by real-time quantitative RT-PCR and Western blot.

RESULTS

The csrA mutant showed loss of motility and lower adhesion ability compared with the wild-type and revertant J99 strains. The csrA mutant was not flagellated. Transcription of flaA and flaB mRNA decreased to only 40% and 16%, respectively, in the csrA mutant compared with the wild-type J99 (p = .006 and <.0001, respectively), and Western blot analysis showed dramatically reduced FlaA/FlaB proteins in a csrA mutant. The disruption of csrA also decreased expression of rpoN to 48% in the csrA mutant, but the degradation rate of rpoN mRNA was not changed.

CONCLUSION

These results suggest that CsrA regulates H. pylori J99 flagella formation and thereby affects bacterial motility.

Expression, refolding, purification and crystallization of the sensory domain of the TlpC chemoreceptor from Helicobacter pylori for structural studies

Helicobacter pylori infections are associated with gastritis, duodenal and gastric ulcers and gastric adenocarcinoma. Bacterial chemotaxis, mediated by four different chemoreceptors (also termed transducer-like proteins (Tlp)), plays an important role in initial colonization and development of disease. Chemoreceptor sensory domains of H. pylori share no significant sequence similarity with those of Escherichia coli or any other non-Epsilonproteobacteria. The structural basis of how chemical signals are recognized by chemoreceptors of H. pylori is poorly understood mainly due to the lack of a robust procedure to purify their sensory domains in a soluble form. This study reports a method for extraction of the periplasmic sensory domain of transducer-like protein C (TlpC) from inclusion bodies and refolding to yield 5mg pure crystallizable protein per 1l of bacterial culture. Purified protein was monomeric in solution by size-exclusion chromatography and folded according to the circular dichroism spectrum. Crystals have been grown by the hanging-drop vapor-diffusion method using PEG 4000 as a precipitating agent. The crystals belonged to space group C2, with unit-cell parameters a=189.3, b=103.2, c=61.8Å, β=98.3. A complete X-ray diffraction data set has been collected to 2.2 Å resolution using cryocooling conditions and synchrotron radiation. Self-rotation function and Matthews coefficient calculations suggest that the asymmetric unit contains three monomers.

Motility and chemotaxis mediate the preferential colonization of gastric injury sites by Helicobacter pylori

Helicobacter pylori (H. pylori) is a pathogen contributing to peptic inflammation, ulceration, and cancer. A crucial step in the pathogenic sequence is when the bacterium first interacts with gastric tissue, an event that is poorly understood in vivo. We have shown that the luminal space adjacent to gastric epithelial damage is a microenvironment, and we hypothesized that this microenvironment might enhance H. pylori colonization. Inoculation with 10⁶H. pylori (wild-type Sydney Strain 1, SS1) significantly delayed healing of acetic-acid induced ulcers at Day 1, 7 and 30 post-inoculation, and wild-type SS1 preferentially colonized the ulcerated area compared to uninjured gastric tissue in the same animal at all time points. Gastric resident Lactobacillus spp. did not preferentially colonize ulcerated tissue. To determine whether bacterial motility and chemotaxis are important to ulcer healing and colonization, we analyzed isogenic H. pylori mutants defective in motility (ΔmotB) or chemotaxis (ΔcheY). ΔmotB (10⁶) failed to colonize ulcerated or healthy stomach tissue. ΔcheY (10⁶) colonized both tissues, but without preferential colonization of ulcerated tissue. However, ΔcheY did modestly delay ulcer healing, suggesting that chemotaxis is not required for this process. We used two-photon microscopy to induce microscopic epithelial lesions in vivo, and evaluated accumulation of fluorescently labeled H. pylori at gastric damage sites in the time frame of minutes instead of days. By 5 min after inducing damage, H. pylori SS1 preferentially accumulated at the site of damage and inhibited gastric epithelial restitution. H. pylori ΔcheY modestly accumulated at the gastric surface and inhibited restitution, but did not preferentially accumulate at the injury site. H. pylori ΔmotB neither accumulated at the surface nor inhibited restitution. We conclude that bacterial chemosensing and motility rapidly promote H. pylori colonization of injury sites, and thereby biases the injured tissue towards sustained gastric damage.

H. pylori is a disease-causing bacterium that commonly infects the human stomach in both developed and underdeveloped countries. Infected individuals can develop digestive diseases, including stomach inflammation, peptic ulcer, and cancer. There has been only limited investigation into the events when H. pylori first interacts with stomach tissue. Using anesthetized mice in which we have induced microscopic damage to the stomach surface, we find that H. pylori is able to rapidly detect and navigate towards this damage site. Within minutes, bacterial accumulation slows repair of the damage. This is the earliest event of H. pylori pathogenesis that has been reported in vivo. We further define that this pathology is due to the bacterial accumulation at damage sites and that this also occurs in a model of larger stomach damage (ulceration). The broader implications of our work are that even sub-clinical insults to the stomach that occur in daily life (damage from grinding of food, ingestion of alcohol, taking an aspirin) can potentially attract H. pylori and not only slow repair of any existing damage, but maybe also provide an initiation site that can start the pathogenic sequence of stomach disease caused by H. pylori.

Does bacterial infection cause genome instability and cancer in the host cell?

Research of the past several decades suggests that bacterial infection can lead to genome instability of the host cell often resulting in cancer development. However, there is still a substantial lack of knowledge regarding possible mechanisms involved in the development of genomic instability. Several questions remain unanswered, namely: Why has the causative relationship between the bacterial infection and cancer been established only for a small number of cancers? What is the mechanism responsible for the induction of genome instability and cancer? Is the infection process required to cause genome instability and cancer? In this review, we present a hypothesis that the bacterial infection, exposure to heat-killed bacteria or even some bacterial determinants may trigger genome instability of exposed and distal cells, and thus may cause cancer. We will discuss the mechanisms of host responses to the bacterial infection and present the possible pathways leading to genome instability and cancer through exposure to bacteria.

Role of energy sensor TlpD of Helicobacter pylori in gerbil colonization and genome analyses after adaptation in the gerbil

Helicobacter pylori maintains colonization in its human host using a limited set of taxis sensors. TlpD is a proposed energy taxis sensor of H. pylori and dominant under environmental conditions of low bacterial energy yield. We studied the impact of H. pylori TlpD on colonization in vivo using a gerbil infection model which closely mimics the gastric physiology of humans. A gerbil-adapted H. pylori strain, HP87 P7, showed energy-dependent behavior, while its isogenic tlpD mutant lost it. A TlpD-complemented strain regained the wild-type phenotype. Infection of gerbils with the complemented strain demonstrated that TlpD is important for persistent infection in the antrum and corpus and suggested a role of TlpD in horizontal navigation and persistent corpus colonization. As a part of the full characterization of the model and to gain insight into the genetic basis of H. pylori adaptation to the gerbil, we determined the complete genome sequences of the gerbil-adapted strain HP87 P7, two HP87 P7 tlpD mutants before and after gerbil passage, and the original human isolate, HP87. The integrity of the genome, including that of a functional cag pathogenicity island, was maintained after gerbil adaptation. Genetic and phenotypic differences between the strains were observed. Major differences between the gerbil-adapted strain and the human isolate emerged, including evidence of recent recombination. Passage of the tlpD mutant through the gerbil selected for gain-of-function variation in a fucosyltransferase gene, futC (HP0093). In conclusion, a gerbil-adapted H. pylori strain with a stable genome has helped to establish that TlpD has important functions for persistent colonization in the stomach.

The 3.2 Å resolution structure of a receptor: CheA:CheW signaling complex defines overlapping binding sites and key residue interactions within bacterial chemosensory arrays

Bacterial chemosensory arrays are composed of extended networks of chemoreceptors (also known as methyl-accepting chemotaxis proteins, MCPs), the histidine kinase CheA, and the adaptor protein CheW. Models of these arrays have been developed from cryoelectron microscopy, crystal structures of binary and ternary complexes, NMR spectroscopy, mutational, data and biochemical studies. A new 3.2 Å resolution crystal structure of a Thermotoga maritima MCP protein interaction region in complex with the CheA kinase-regulatory module (P4-P5) and adaptor protein CheW provides sufficient detail to define residue contacts at the interfaces formed among the three proteins. As in a previous 4.5 Å resolution structure, CheA-P5 and CheW interact through conserved hydrophobic surfaces at the ends of their β-barrels to form pseudo 6-fold symmetric rings in which the two proteins alternate around the circumference. The interface between P5 subdomain 1 and CheW subdomain 2 was anticipated from previous studies, whereas the related interface between CheW subdomain 1 and P5 subdomain 2 has only been observed in these ring assemblies. The receptor forms an unexpected structure in that the helical hairpin tip of each subunit has "unzipped" into a continuous α-helix; four such helices associate into a bundle, and the tetramers bridge adjacent P5-CheW rings in the lattice through interactions with both P5 and CheW. P5 and CheW each bind a receptor helix with a groove of conserved hydrophobic residues between subdomains 1 and 2. P5 binds the receptor helix N-terminal to the tip region (lower site), whereas CheW binds the same helix with inverted polarity near the bundle end (upper site). Sequence comparisons among different evolutionary classes of chemotaxis proteins show that the binding partners undergo correlated changes at key residue positions that involve the lower site. Such evolutionary analyses argue that both CheW and P5 bind to the receptor tip at overlapping positions. Computational genomics further reveal that two distinct CheW proteins in Thermotogae utilize the analogous recognition motifs to couple different receptor classes to the same CheA kinase. Important residues for function previously identified by mutagenesis, chemical modification and biophysical approaches also map to these same interfaces. Thus, although the native CheW-receptor interaction is not observed in the present crystal structure, the bioinformatics and previous data predict key features of this interface. The companion study of the P5-receptor interface in native arrays (accompanying paper Piasta et al. (2013) Biochemistry, DOI: 10.1021/bi400385c) shows that, despite the non-native receptor fold in the present crystal structure, the local helix-in-groove contacts of the crystallographic P5-receptor interaction are present in native arrays and are essential for receptor regulation of kinase activity.

Life in the human stomach: persistence strategies of the bacterial pathogen Helicobacter pylori

The bacterial pathogen Helicobacter pylori has co-evolved with humans and colonizes approximately 50% of the human population, but only causes overt gastric disease in a subset of infected hosts. In this Review, we discuss the pathogenesis of H. pylori and the mechanisms it uses to promote persistent colonization of the gastric mucosa, with a focus on recent insights into the role of the virulence factors vacuolating cytotoxin (VacA), cytotoxin-associated gene A (CagA) and CagL. We also describe the immunobiology of H. pylori infection and highlight how this bacterium manipulates the innate and adaptive immune systems of the host to promote its own persistence.

The degree of Helicobacter pylori-triggered inflammation is manipulated by preinfection host microbiota

Helicobacter pylori infects over 3 billion people worldwide and is the primary risk factor for gastric cancer. Most individuals infected with H. pylori develop only asymptomatic gastritis; however, some develop ulcers or gastric adenocarcinoma. We demonstrate that one previously unappreciated parameter influencing H. pylori disease outcome is variation in the preinfection host microbiota. Utilizing a mouse model, we altered the microbiota by antibiotic treatment and found that these alterations resulted in significantly lowered H. pylori-triggered inflammation. Specifically, antibiotic pretreatment reduced CD4(+) T-helper cells and Ifnγ transcript levels in gastric tissue after H. pylori infection. The bacterial communities in mice with a reduced response to H. pylori displayed many differences from those in untreated mice, including significantly more cluster IV and XIVa Clostridium spp., bacteria known to influence inflammation via regulatory T cell populations. Our findings suggest that microbiota composition, perhaps Clostridium spp., contributes to the variable disease outcome of H. pylori infection by altering the recruitment of CD4(+) T cells to the gastric compartment. Our results suggest that gastric microbiota could be used as a diagnostic tool to determine which patients are at risk for developing severe disease.

Stromal cells induce Th17 during Helicobacter pylori infection and in the gastric tumor microenvironment

Gastric cancer is associated with chronic inflammation and Helicobacter pylori infection. Th17 cells are CD4(+) T cells associated with infections and inflammation; but their role and mechanism of induction during carcinogenesis is not understood. Gastric myofibroblasts/fibroblasts (GMF) are abundant class II MHC expressing cells that act as novel antigen presenting cells. Here we have demonstrated the accumulation of Th17 in H. pylori-infected human tissues and in the gastric tumor microenvironment. GMF isolated from human gastric cancer and H. pylori infected tissues co-cultured with CD4(+) T cells induced substantially higher levels of Th17 than GMF from normal tissues in an IL-6, TGF-β, and IL-21 dependent manner. Th17 required interaction with class II MHC on GMF for activation and proliferation. These studies suggest that Th17 are induced during both H. pylori infection and gastric cancer in the inflammatory milieu of gastric stroma and may be an important link between inflammation and carcinogenesis.

Helicobacter pylori: clinical management

PURPOSE OF REVIEW

Progress continues in our understanding of the role of Helicobacter pylori infection in gastroduodenal as well as extragastric disorders. This review gives an overview on selected areas of the H. pylori infection and their clinical implications.

RECENT FINDINGS

Indications for therapy have been extended and now include idiopathic thrombocytopenic purpura, iron deficiency anemia, and vitamin B12 deficiency. New data are presented on the role of H. pylori in neurodegenerative disorders and in the metabolic syndrome. H. pylori is associated with a (small) increase in the risk for colorectal adenoma and colon cancer. The biggest challenge is the selection of new therapies and treatment strategies because of the increasing failure of standard triple therapies. The best option in high clarithromycin resistance areas is bismuth-based quadruple therapy. Probiotic bacteria and yeasts reduce adverse effects of standard H. pylori eradication regimens. In gastric cancer prevention, screening programs based on the serological detection of preneoplastic conditions may prove useful.

SUMMARY

New algorithms for preventing H. pylori-induced disease and eradicating the organism should be individualized.

Inflammation, immunity, and vaccines for Helicobacter pylori infection

The immune response to Helicobacter pylori is a multifaceted group of mechanisms involving responses that are both protective and damaging to the host. The innate and the adaptive immune responses lead to damaging inflammatory responses, but these responses may fail, allowing for persistence of many infections. Thus, developing new therapeutics and effective vaccines against H. pylori has proven to be arduous. In this manuscript, we will examine the advances in knowledge made in the past year in understanding the host immune response to H. pylori and the progress toward developing a vaccine.

Helicobacter pylori requires TlpD-driven chemotaxis to proliferate in the antrum

Different disease outcomes of Helicobacter pylori infection correlate with distinct inflammation patterns. These different inflammatory distributions may be initiated by differences in bacterial localization. One H. pylori property known to affect murine stomach localization is chemotaxis, the ability to move in response to chemical cues. In this report, we used nonchemotactic mutants (Che(-)) to analyze whether chemotaxis is required for initial colonization of particular stomach regions or for subsequent growth therein. We found that H. pylori behaves differently in the corpus, antrum, and corpus-antrum transition zone subregions of the stomach. This outcome suggests that these regions contain unique chemotactic signals. In the corpus, H. pylori utilizes chemotaxis for initial localization but not for subsequent growth. In contrast, in the antrum and the corpus-antrum transition zone, chemotaxis does not help initial colonization but does promote subsequent proliferation. To determine which chemoreceptor is responsible for the corpus-antrum phenotypes, we infected mice with strains lacking each chemoreceptor. Strains lacking TlpA, TlpB, or TlpC displayed only modest deviations from the wild-type phenotype, while strains lacking TlpD resembled the Che(-) mutant in their antral colonization defect and fared even worse than the Che(-) mutant in the corpus. Additional analysis showed that inflammation is worse in the antrum than in the corpus in both wild-type and Che(-) mutant infections. These results suggest that chemotaxis, specifically, that controlled by TlpD, is necessary for H. pylori to survive or grow in the environment of increased inflammation in the antrum.

Role of Th17 and IL-17 in Helicobacter pylori-related gastric carcinogenesis

T helper 17 (Th17) cells are a newly defined subset of CD4⁺ effecter T cells characterized by the secretion of interleukin 17 (IL-17) and transcription factor RORγ. They play significant roles in the pathogenesis of various tumors and bacterial infectious diseases. Gastric carcinoma is closely related to Helicobacter pylori (H. pylori) infection and has a very high mortality. Evidence shows that both Th17 and IL-17 play critical roles in the pathogenesis of H. pylori-associated gastric carcinoma and precancerous lesions. Elucidation of the roles of Th17 and IL-17 in H. pylori-related gastric carcinogenesis will provide new clues to the early diagnosis, personalized prevention and immunotherapy, vaccination and prognostic evaluation of gastric carcinoma.