The local immune response of mice after Helicobacter suis infection: strain differences and distinction with Helicobacter pylori

Detection, isolation and virulence characterization of Helicobacter suis from pork products aimed to human consumption

Helicobacter suis is the most common non-Helicobacter pylori gastric Helicobacter species found in humans. Infection is associated with gastritis, peptic ulcer, gastric MALT lymphoma and neurodegenerative disorders, particularly Parkinson's disease. However, the pathogenicity of this species is still a matter of research, and results of virulence studies and antibiotic susceptibility tests tend to vary between strains. Cholesterol α-glucosyltransferase (αCgT), a known H. pylori virulence factor, appears to be present in most clinical H. suis isolates. The ability to form biofilms also plays a crucial role in the pathogenesis of H. pylori. However, no reports have been published on this ability in H. suis. H. suis is considered an emerging zoonotic pathogen, with pigs being the main source of human infection. However, there is very little information on its presence in pork, mainly due to the difficulties of its culture. Therefore, our aim was to determine the prevalence of H. suis in pork products from our geographical area by PCR and Fluorescence in situ Hybridization (FISH), as well as to isolate the bacteria and determine the antibiotic susceptibility patterns, the presence of the αCgT gene and the ability of the isolates to form biofilms. Overall, H. suis was detected in 20 of the 70 (28.6 %) samples analyzed. In 3 of them, H. suis was isolated. The αCgT gene was detected in all isolates and two of them showed a multiresistance pattern. The H. suis reference strain and two of the isolates showed "strong" to "moderate" in vitro biofilm formation ability under optimal growth conditions. Our results seem to indicate that H. suis is significantly prevalent in pork products. The combination of culture with FISH and/or mPCR proved to be a rapid and specific method for the detection, identification and direct visualization of cultivable H. suis cells from pork food products.

Molecular detection of Helicobacter spp. and Fusobacterium gastrosuis in pigs and wild boars and its association with gastric histopathological alterations

Besides Helicobacter pylori, a Gram-negative bacterium that may cause gastric disorders in humans, non-Helicobacter pylori helicobacters (NHPH) may also colonize the stomach of humans and animals. In pigs, H. suis can induce gastritis and may play a role in gastric ulcer disease, possibly in association with Fusobacterium gastrosuis. In the present study, gastric samples from 71 slaughtered pigs and 14 hunted free range wild boars were tested for the presence of DNA of F. gastrosuis and gastric Helicobacter species associated with pigs, dogs cats and humans, using species-specific PCR assays, followed by sequencing of the amplicon. These gastric samples were also histopathologically evaluated. Almost all the pigs presented gastritis (95.8%). Helicobacter spp. were detected in 78.9% and F. gastrosuis in 35.2% of the animals. H. suis was the most frequently identified Helicobacter species (57.7% of the animals), followed by a H. pylori-like species (50.7%) and less often H. salomonis and H. felis (each in 2.8% of the animals). H. suis was most often detected in the glandular (distal) part of the stomach (pars oesophagea 9.9%, oxyntic mucosa 35.2%, antral mucosa 40.8%), while the H. pylori-like species was mainly found in the non-glandular (proximal) part of the stomach (pars oesophagea 39.4%, oxyntic mucosa 14.1%, antral mucosa 4.2%). The great majority of wild boars were also affected with gastritis (71.4%) and Helicobacter spp. and F. gastrosuis were detected in 64.3% and 42.9% of the animals, respectively. H. bizzozeronii and H. salomonis were the most frequently detected Helicobacter species, while a H. pylori-like species and H. suis were only occasionally identified. These findings suggest that these microorganisms can colonize the stomach of both porcine species and may be associated with gastric pathology. This should, however, be confirmed through bacterial isolation. This is the first description of the presence of F. gastrosuis DNA in the stomach of wild boars and a H. pylori-like species in the pars oesophagea of the porcine stomach.

Effect of inhibition of Toll-like receptor 3 signaling on pathogenesis of rabies virus in mouse model

Rabies is a zoonotic viral disease with inevitably fatal outcome. Toll-like receptor 3 (TLR3) could sense dsRNA viral infections, and implicated in pathogenesis of rabies and Negri bodies (NBs) formation. Present study was undertaken to elucidate the role of TLR3 in pathogenesis, NBs formation, and therapeutic potential of blocking TLR3/dsRNA interaction in rabies infection. Young Swiss albino mice were infected with 100 LD₅₀ of street rabies virus (SRABV) intracerebrally (i/c) on day 0 and treated with 30 μg of CU CPT 4a (selective TLR3 inhibitor) i/c on 0, 3 and 5 days post-infection (DPI). Three mice each were sacrificed at 1, 3, 5, 7, 9, 11, and 13 DPI to study sequential pathological consequences through histopathology, Seller's staining, immunofluorescence, immunohistochemistry, TUNEL assay, flow cytometry, and viral and cytokine genes quantification by real-time PCR. CU CPT 4a inhibited TLR3 expression resulted in delayed development and decreased intensity of clinical signs and pathological lesions, low viral load, significantly reduced NBs formation, and increased survival time in SRABV-infected mice. These parameters suggested that TLR3 did influence the SRABV replication and NBs formation. Inhibition of TLR3 led to decreased expression of pro-inflammatory cytokines and interferons indicated an anti-inflammatory effect of CU CPT 4a during SRABV infection. Further, TLR3-inhibited group revealed normal CD4⁺/CD8⁺ T-cells ratio with less TUNEL-positive apoptotic cells indicated that immune cell kinetics are not affected during TLR3-inhibition. SRABV-infected and mock-treated mice were developed severe clinical signs and histopathological lesions, more NBs formation, high viral load, increased pro-inflammatory cytokines expression in brain, which were correlated with higher expression levels of TLR3. In conclusion, these data suggested that TLR3/dsRNA signaling pathway could play critical role in pathogenesis of SRABV infection in vivo and opens up new avenues of therapeutics.

Gastric Helicobacter species associated with dogs, cats and pigs: significance for public and animal health

This article focuses on the pathogenic significance of Helicobacter species naturally colonizing the stomach of dogs, cats and pigs. These gastric "non-Helicobacter (H.) pylori Helicobacter species" (NHPH) are less well-known than the human adapted H. pylori. Helicobacter suis has been associated with gastritis and decreased daily weight gain in pigs. Several studies also attribute a role to this pathogen in the development of hyperkeratosis and ulceration of the non-glandular stratified squamous epithelium of the pars oesophagea of the porcine stomach. The stomach of dogs and cats can be colonized by several Helicobacter species but their pathogenic significance for these animals is probably low. Helicobacter suis as well as several canine and feline gastric Helicobacter species may also infect humans, resulting in gastritis, peptic and duodenal ulcers, and low-grade mucosa-associated lymphoid tissue lymphoma. These agents may be transmitted to humans most likely through direct or indirect contact with dogs, cats and pigs. Additional possible transmission routes include consumption of water and, for H. suis, also consumption of contaminated pork. It has been described that standard H. pylori eradication therapy is usually also effective to eradicate the NHPH in human patients, although acquired antimicrobial resistance may occasionally occur and porcine H. suis strains are intrinsically less susceptible to aminopenicillins than non-human primate H. suis strains and other gastric Helicobacter species. Virulence factors of H. suis and the canine and feline gastric Helicobacter species include urease activity, motility, chemotaxis, adhesins and gamma-glutamyl transpeptidase. These NHPH, however, lack orthologs of cytotoxin-associated gene pathogenicity island and vacuolating cytotoxin A, which are major virulence factors in H. pylori. It can be concluded that besides H. pylori, gastric Helicobacter species associated with dogs, cats and pigs are also clinically relevant in humans. Although recent research has provided better insights regarding pathogenic mechanisms and treatment strategies, a lot remains to be investigated, including true prevalence rates, exact modes of transmission and molecular pathways underlying disease development and progression.

Helicobacter spp. in the Stomach of Cats: Successful Colonization and Absence of Relevant Histopathological Alterations Reveals High Adaptation to the Host Gastric Niche

In addition to Helicobacter pylori, many non-Helicobacter pylori Helicobacters (NHPH) are able to cause gastric disease in humans. Cats are a natural reservoir for many of these species. Accordingly, living in close and intimate contact with animals has been identified as a risk factor, and an important zoonotic significance has therefore been attributed to NHPH. To determine the prevalence and associated gastric histopathological changes of Helicobacter species, the gastric mucosa of 71 cats were evaluated. Only four presented normal histopathological mucosa with the absence of spiral-shaped organisms. Normal gastric mucosa and the presence of spiral-shaped bacteria were observed in 13 cats. The remaining animals presented histopathological changes representative of gastritis. Helicobacter species were detected in 53 cats (74.6%) by at least one detection method. None of the animals were positive for H. pylori or for H. ailurogastricus. Helicobacter heilmannii organisms were identified in 20 animals, predominantly in the body gastric region. Helicobacter salomonis was the second most prevalent species (57.1%), although it was mainly found in association with other NHPH. Helicobacter felis and H. bizzozeronii were less frequently detected. The great majority of the Helicobacter spp. PCR-positive animals presented normal features regarding fibrosis/mucosal atrophy, neutrophils, eosinophils, or other inflammatory cells and lymphofollicular hyperplasia. Given the controversy and the strong evidence of absence of significant histopathological alterations associated with the presence of Helicobacter spp. in cats, it is possible to hypothesize that these bacteria may be able to adapt to the feline gastric microenvironment or even to comprise part of the gastric microbiome of this animal species. Thus, prudency must be taken when prescribing an antibiotic therapy based solely on the presence of these bacteria in the feline stomach.

The Use of Disinfectant in Barn Cleaning Alters Microbial Composition and Increases Carriage of Campylobacter jejuni in Broiler Chickens

To maintain food safety and flock health in broiler chicken production, biosecurity approaches to keep chicken barns free of pathogens are important. Canadian broiler chicken producers must deep clean their barns with chemical disinfectants at least once annually (full disinfection [FD]) and may wash with water (water wash [WW]) throughout the year. However, many producers use FD after each flock, assuming a greater efficacy of more stringent cleaning protocols, although little information is known regarding how these two cleaning practices affect pathogen population and gut microbiota. In the present study, a crossover experiment over four production cycles was conducted in seven commercial chicken barns to compare WW and FD. We evaluated the effects of barn cleaning methods on commercial broiler performance, cecal microbiota composition, Campylobacter and Salmonella occurrence, and Campylobacter jejuni and Clostridium perfringens abundance, as well as on short-chain fatty acid (SCFA) concentrations in the month-old broiler gut. The 30-day body weight and mortality rate were not affected by the barn cleaning methods. The WW resulted in a modest but significant effect on the structure of broiler cecal microbiota (weighted-UniFrac; adonis P = 0.05, and unweighted-UniFrac; adonis P = 0.01), with notable reductions in C. jejuni occurrence and abundance. In addition, the WW group had increased cecal acetate, butyrate, and total SCFA concentrations, which were negatively correlated with C. jejuni abundance. Our results suggest that WW may result in enhanced activity of the gut microbiota and reduced zoonotic transmission of C. jejuni in broiler production relative to FD in the absence of a disease challenge. IMPORTANCE We compared the effects of barn FD and WW methods on gut microbial community structures and pathogen prevalence of broiler chickens in a nonchallenging commercial production setting. The results revealed that barn cleaning methods had little impact on the 30-day body weight and mortality rate of broiler chickens. In addition, the FD treatment had a subtle but significant effect on the broiler cecal microbiota with increased abundances of Campylobacter and decreased SCFA concentrations, which would support the adoption of WW as a standard practice. Thus, compared to FD, WW can be beneficial to broiler chicken production by inhibiting zoonotic pathogen colonization in the chicken gut with reduced cost and labor of cleaning.

Gastric Helicobacter suis Infection Partially Protects against Neurotoxicity in A 6-OHDA Parkinson's Disease Mouse Model

The exact etiology of Parkinson’s disease (PD) remains largely unknown, but more and more research suggests the involvement of the gut microbiota. Interestingly, idiopathic PD patients were shown to have at least a 10 times higher prevalence of Helicobacter suis (H. suis) DNA in gastric biopsies compared to control patients. H. suis is a zoonotic Helicobacter species that naturally colonizes the stomach of pigs and non-human primates but can be transmitted to humans. Here, we investigated the influence of a gastric H. suis infection on PD disease progression through a 6-hydroxydopamine (6-OHDA) mouse model. Therefore, mice with either a short- or long-term H. suis infection were stereotactically injected with 6-OHDA in the left striatum and sampled one week later. Remarkably, a reduced loss of dopaminergic neurons was seen in the H. suis/6-OHDA groups compared to the control/6-OHDA groups. Correspondingly, motor function of the H. suis-infected 6-OHDA mice was superior to that in the non-infected 6-OHDA mice. Interestingly, we also observed higher expression levels of antioxidant genes in brain tissue from H. suis-infected 6-OHDA mice, as a potential explanation for the reduced 6-OHDA-induced cell loss. Our data support an unexpected neuroprotective effect of gastric H. suis on PD pathology, mediated through changes in oxidative stress.

Anisakis pegreffii Extract Induces Airway Inflammation with Airway Remodeling in a Murine Model System

Exposure of the respiratory system to the Anisakis pegreffii L3 crude extract (AE) induces airway inflammation; however, the mechanism underlying this inflammatory response remains unknown. AE contains allergens that promote allergic inflammation; exposure to AE may potentially lead to asthma. In this study, we aimed to establish a murine model to assess the effects of AE on characteristic features of chronic asthma, including airway hypersensitivity (AHR), airway inflammation, and airway remodeling. Mice were sensitized for five consecutive days each week for 4 weeks. AHR, lung inflammation, and airway remodeling were evaluated 24 h after the last exposure. Lung inflammation and airway remodeling were assessed from the bronchoalveolar lavage fluid (BALF). To confirm the immune response in the lungs, changes in gene expression in the lung tissue were assessed with reverse transcription-quantitative PCR. The levels of IgE, IgG1, and IgG2a in blood and cytokine levels in the BALF, splenocyte, and lung lymph node (LLN) culture supernatant were measured with ELISA. An increase in AHR was prominently observed in AE-exposed mice. Epithelial proliferation and infiltration of inflammatory cells were observed in the BALF and lung tissue sections. Collagen deposition was detected in lung tissues. AE exposure increased IL-4, IL-5, and IL-13 expression in the lung, as well as the levels of antibodies specific to AE. IL-4, IL-5, and IL-13 were upregulated only in LLN. These findings indicate that an increase in IL-4+ CD4+ T cells in the LLN and splenocyte resulted in increased Th2 response to AE exposure. Exposure of the respiratory system to AE resulted in an increased allergen-induced Th2 inflammatory response and AHR through accumulation of inflammatory and IL-4+ CD4+ T cells and collagen deposition. It was confirmed that A. pegreffii plays an essential role in causing asthma in mouse models and has the potential to cause similar effects in humans.

Presence of Helicobacter pylori and H. suis DNA in Free-Range Wild Boars

Simple Summary

Helicobacter pylori and H. suis are associated with gastric pathologies in humans. To obtain better insights into the potential role of wild boars as reservoirs of these pathogens, gastric samples of 14 animals were tested for the presence of H. pylori and H. suis DNA. Two wild boars were found PCR-positive for H. pylori and one for H. suis. This indicates that these microorganisms may colonize the stomach of wild boars.

Abstract

Helicobacter pylori (H. pylori) is a Gram-negative bacterium that infects half of the human population worldwide, causing gastric disorders, such as chronic gastritis, gastric or duodenal ulcers, and gastric malignancies. Helicobacter suis (H. suis) is mainly associated with pigs, but can also colonize the stomach of humans, resulting in gastric pathologies. In pigs, H. suis can induce gastritis and seems to play a role in gastric ulcer disease, seriously affecting animal production and welfare. Since close interactions between domestic animals, wildlife, and humans can increase bacterial transmission risk between species, samples of gastric tissue of 14 free range wild boars (Sus scrofa) were evaluated for the presence of H. pylori and H. suis using PCR. Samples from the antral gastric mucosa from two animals were PCR-positive for H. pylori and another one for H. suis. These findings indicate that these microorganisms were able to colonize the stomach of wild boars and raise awareness for their putative intervention in Helicobacter spp. transmission cycle.

Effects of Flaxseed and Multi-Carbohydrase Enzymes on the Cecal Microbiota and Liver Inflammation of Laying Hens

Simple Summary

Wheat and flaxseed are used worldwide to produce omega-3 (ω-3) enriched poultry meat and eggs, however, wheat and flaxseed contain some anti-nutritional factors (ANFs). In addition, the supplementation of feed additive including enzymes usually alleviate the deleterious influence of ANFs. Therefore, we conducted the current study of laying hens fed with two diets (corn/flaxseed and wheat/flaxseed, supplemented with three enzymes), for a period of 10 weeks. Here, we found a clear increase in the fat weight of birds fed with corn diet as compared with wheat diet. Moreover, a high level of secretory IL-1β, IL-6, and IL-10 and comparatively higher inflammatory changes in the liver tissue were found in birds fed with corn diet as compared with wheat diet. The gut microbial composition of hens fed with corn diet was clearly different than that of birds fed a wheat diet. In conclusion, our findings suggest that inflammatory changes in laying birds were mediated by a corn diet with flaxseed and enzymes instead of a wheat diet. Additionally, in the wheat-fed group, enzyme-b and -c showed more encouraging results as compared to enzyme-a indicating that wheat diet might be a preferable diet for commercial layers poultry farms.

Abstract

Background: The use of wheat and flaxseed to produce omega-3 (ω-3) enriched poultry meat and eggs is very popular in the world. However, wheat and flaxseed contain some anti-nutritional factors (ANFs), and enzymes are usually used to alleviate the deleterious influence of ANFs. Method: A 2 × 3 two factors design was used in the experiment. A total of 540 twenty-week-old Nongda-3 laying hens were randomly allocated to six dietary treatments, two diets (corn/flaxseed and wheat/flaxseed), and three enzymes (enzyme-a contains neutral protease 10,000, xylanase 35,000, β-mannanase 1500, β-glucanase 2000, cellulose 500, amylase 100, and pectinase 10,000 (U g⁻¹); enzyme-b contains alkaline protease 40,000 and neutral protease 10,000 (U g⁻¹); enzyme-c contains alkaline protease 40,000, neutral protease 10,000, and cellulase 4000 (U g⁻¹). Results: There was an interaction between dietary treatment and supplemental enzymes for liver weight and liver inflammatory cytokines of broilers. A significant increase was observed in the fat weight of birds fed a corn diet as compared with a wheat diet. A corn diet and wheat diet with the addition of enzyme-a (p < 0.001) showed the highest level of liver fat followed by enzyme-c (p < 0.01) and enzyme-b. Moreover, a high level of secretory IL-1β, IL-6, and IL-10 and comparatively higher inflammatory changes in the liver tissue were found in birds fed a corn diet as compared with a wheat diet, and enzyme-b showed more beneficial effects as compared with enzyme-a and -c. The gut microbial composition of hens fed a corn diet was significantly different than that of birds fed a wheat diet. Bacteroides were significantly (p < 0.05) abundant in the corn-fed birds as compared with wheat-fed birds. However, Firmicutes were less abundant in the wheat-fed birds than the corn-fed birds (16.99 vs. 31.80%, respectively). The microbial community at the genus level differed significantly in the dietary groups and we observed that Bacteroides are the predominant cecal microbiota. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of co-factors, carbohydrates, vitamins, protein, and energy were expressed at slightly higher levels in the microbiota of the wheat-fed birds, whereas, metabolic pathways for nucleotides, lipids, and glycine were expressed at higher levels in the wheat-fed birds. Furthermore, expression of the growth and cellular processes pathway and endocrine system pathway levels were predicted to be higher for the wheat-fed group as compared with the corn-fed group. Conclusions: In conclusion, our findings suggest that inflammatory changes in laying birds were mediated by a corn diet with flaxseed and enzymes instead of a wheat diet. Additionally, in the wheat-fed group, enzyme-b and -c showed more encouraging results as compared to enzyme-a.

Helicobacter and the Potential Role in Neurological Disorders: There Is More Than Helicobacter pylori

Trillions of symbiotic microbial cells colonize our body, of which the larger part is present in the human gut. These microbes play an essential role in our health and a shift in the microbiome is linked to several diseases. Recent studies also suggest a link between changes in gut microbiota and neurological disorders. Gut microbiota can communicate with the brain via several routes, together called the microbiome–gut–brain axis: the neuronal route, the endocrine route, the metabolic route and the immunological route. Helicobacter is a genus of Gram-negative bacteria colonizing the stomach, intestine and liver. Several papers show the role of H. pylori in the development and progression of neurological disorders, while hardly anything is known about other Helicobacter species and the brain. We recently reported a high prevalence of H. suis in patients with Parkinson’s disease and showed an effect of a gastric H. suis infection on the mouse brain homeostasis. Here, we discuss the potential role of H. suis in neurological disorders and how it may affect the brain via the microbiome–gut–brain axis.

Use of 16S rRNA gene sequencing for prediction of new opportunistic pathogens in chicken ileal and cecal microbiota

In this study, we addressed differences in the development of gut microbiota in 4 successive batches of commercially hatched broiler parent chickens. When planning this study, we expected to find a batch with compromised performance which would allow identification of microbiota of suboptimal composition. Microbiota composition was determined only by sequencing the V3/V4 region of 16S rRNA genes in samples collected from chickens 5 to 18 wk of age. In a total, 100 and 160 samples originating from the ileum or cecum were processed, respectively. In one of the flocks with suboptimal performance we identified an increased abundance of Helicobacter brantae forming over 80% of ileal microbiota in individual chickens. Moreover, we also tested samples of 53-wk-old hens from the same genetic line in which egg production decreased. In this case, cecal microbiota was enriched for Fusobacterium mortiferum forming over 30% of total cecal microbiota. Although none of the identified unusual microbiota members have been well recognized as pathogenic, they may represent new opportunistic pathogens of chickens worth of further investigation. Analysis of gut microbiota composition by next generation sequencing thus proved as a useful and unbiased alternative to bacterial culture, especially in the cases of unspecific symptoms like decrease in flock performance.

Disruption of Intestinal Homeostasis and Intestinal Microbiota During Experimental Autoimmune Uveitis

Purpose

We determine the changes in intestinal microbiota and/or disruptions in intestinal homeostasis during uveitis.

Methods

Experimental autoimmune uveitis (EAU) was induced in B10.RIII mice with coadministration of interphotoreceptor retinoid-binding protein peptide (IRBP) and killed mycobacterial antigen (MTB) as an adjuvant. Using 16S rRNA gene sequencing, we looked at intestinal microbial differences during the course of uveitis, as well as intestinal morphologic changes, changes in intestinal permeability by FITC-dextran leakage, antimicrobial peptide expression in the gastrointstinal tract, and T lymphocyte prevalence before and at peak intraocular inflammation.

Results

We demonstrate that increased intestinal permeability and antimicrobial peptide expression in the intestinal tract coincide in timing with increased effector T cells in the mesenteric lymph nodes, during the early stages of uveitis, before peak inflammation. Morphologic changes in the intestine were most prominent during this phase, but also occurred with adjuvant MTB alone, whereas increased intestinal permeability was found only in IRBP-immunized mice that develop uveitis. We also demonstrate that the intestinal microbiota were altered during the course of uveitis, and that some of these changes are specific to uveitic animals, whereas others are influenced by adjuvant MTB alone. Intestinal permeability peaked at 2 weeks, coincident with an increase in intestinal bacterial strain differences, peak lipocalin production, and peak uveitis.

Conclusions

An intestinal dysbiosis accompanies a disruption in intestinal homeostasis in autoimmune uveitis, although adjuvant MTB alone promotes intestinal disruption as well. This may indicate a novel axis for future therapeutic targeting experimentally or clinically.

Characterization of the non-glandular gastric region microbiota in Helicobacter suis-infected versus non-infected pigs identifies a potential role for Fusobacterium gastrosuis in gastric ulceration

Helicobacter suis has been associated with development of gastric ulcers in the non-glandular part of the porcine stomach, possibly by affecting gastric acid secretion and altering the gastric microbiota. Fusobacterium gastrosuis is highly abundant in the gastric microbiota of H. suis-infected pigs and it was hypothesized that this micro-organism could play a role in the development of gastric ulceration. The aim of this study was to obtain further insights in the influence of a naturally acquired H. suis infection on the microbiota of the non-glandular part of the porcine stomach and in the pathogenic potential of F. gastrosuis. Infection with H. suis influenced the relative abundance of several taxa at phylum, family, genus and species level. H. suis-infected pigs showed a significantly higher colonization rate of F. gastrosuis in the non-glandular gastric region compared to non-infected pigs. In vitro, viable F. gastrosuis strains as well as their lysate induced death of both gastric and oesophageal epithelial cell lines. These gastric cell death inducing bacterial components were heat-labile. Genomic analysis revealed that genes are present in the F. gastrosuis genome with sequence similarity to genes described in other Fusobacterium spp. that encode factors involved in adhesion, invasion and induction of cell death as well as in immune evasion. We hypothesize that, in a gastric environment altered by H. suis, colonization and invasion of the non-glandular porcine stomach region and production of epithelial cell death inducing metabolites by F. gastrosuis, play a role in gastric ulceration.

In-feed bambermycin medication induces anti-inflammatory effects and prevents parietal cell loss without influencing Helicobacter suis colonization in the stomach of mice

The minimum inhibitory concentration of bambermycin on three porcine Helicobacter suis strains was shown to be 8 μg/mL. The effect of in-feed medication with this antibiotic on the course of a gastric infection with one of these strains, the host response and the gastric microbiota was determined in mice, as all of these parameters may be involved in gastric pathology. In H. suis infected mice which were not treated with bambermycin, an increased number of infiltrating B-cells, T-cells and macrophages in combination with a Th2 response was demonstrated, as well as a decreased parietal cell mass. Compared to this non-treated, infected group, in H. suis infected mice medicated with bambermycin, gastric H. suis colonization was not altered, but a decreased number of infiltrating T-cells, B-cells and macrophages as well as downregulated expressions of IL-1β, IL-8M, IL-10 and IFN-γ were demonstrated and the parietal cell mass was not affected. In bambermycin treated mice that were not infected with H. suis, the number of infiltrating T-cells and expression of IL-1β were lower than in non-infected mice that did not receive bambermycin. Gastric microbiota analysis indicated that the relative abundance of bacteria that might exert unfavorable effects on the host was decreased during bambermycin supplementation. In conclusion, bambermycin did not affect H. suis colonization, but decreased gastric inflammation and inhibited the effects of a H. suis infection on parietal cell loss. Not only direct interaction of H. suis with parietal cells, but also inflammation may play a role in death of these gastric acid producing cells.

The choroid plexus epithelium as a novel player in the stomach-brain axis during Helicobacter infection

Several studies suggest a link between shifts in gut microbiota and neurological disorders. Recently, we reported a high prevalence of Helicobacter suis (H. suis) in patients with Parkinson's disease. Here, we evaluated the effect of gastric H. suis infection on the brain in mice. One month of infection with H. suis resulted in increased brain inflammation, reflected in activation of microglia and cognitive decline. Additionally, we detected choroid plexus inflammation and disruption of the epithelial blood-cerebrospinal fluid (CSF) barrier upon H. suis infection, while the endothelial blood-brain barrier (BBB) remained functional. These changes were accompanied by leakage of the gastrointestinal barrier and low-grade systemic inflammation, suggesting that H. suis-evoked gastrointestinal permeability and subsequent peripheral inflammation induces changes in brain homeostasis via changes in blood-CSF barrier integrity. In conclusion, this study shows for the first time that H. suis infection induces inflammation in the brain associated with cognitive decline and that the choroid plexus is a novel player in the stomach-brain axis.

Short chain fatty acids ameliorate immune-mediated uveitis partially by altering migration of lymphocytes from the intestine

Short chain fatty acids (SCFA) are metabolites of intestinal bacteria resulting from fermentation of dietary fiber. SCFA are protective in various animal models of inflammatory disease. We investigated the effects of exogenous administration of SFCAs, particularly propionate, on uveitis using an inducible model of experimental autoimmune uveitis (EAU). Oral SCFA administration attenuated uveitis severity in a mouse strain-dependent manner through regulatory T cell induction among lymphocytes in the intestinal lamina propria (LPL) and cervical lymph nodes (CLN). SCFA also suppressed effector T cell induction in the CLN and mesenteric lymph nodes (MLN). Alterations in intestinal morphology and gene expression demonstrated in the EAU model prior to the onset of uveitis were blunted by oral SCFA administration. Using a Kaede transgenic mouse, we demonstrated enhanced leukocyte trafficking between the intestine and the eye in EAU. Propionate suppressed T effector cell migration between the intestine and the spleen in EAU Kaede mice. In conclusion, our findings support exogenous administration of SCFAs as a potential treatment strategy for uveitis through the stabilization of subclinical intestinal alterations that occur in inflammatory diseases including uveitis, as well as prevention of trafficking of leukocytes between the gastrointestinal tract and extra-intestinal tissues.

From the animal house to the field: Are there consistent individual differences in immunological profile in wild populations of field voles (Microtus agrestis)?

Inbred mouse strains, living in simple laboratory environments far removed from nature, have been shown to vary consistently in their immune response. However, wildlife populations are typically outbreeding and face a multiplicity of challenges, parasitological and otherwise. In this study we seek evidence of consistent difference in immunological profile amongst individuals in the wild. We apply a novel method in this context, using longitudinal (repeated capture) data from natural populations of field voles, Microtus agrestis, on a range of life history and infection metrics, and on gene expression levels. We focus on three immune genes, IFN-γ, Gata3, and IL-10, representing respectively the Th1, Th2 and regulatory elements of the immune response. Our results show that there was clear evidence of consistent differences between individuals in their typical level of expression of at least one immune gene, and at most all three immune genes, after other measured sources of variation had been taken into account. Furthermore, individuals that responded to changing circumstances by increasing expression levels of Gata3 had a correlated increase in expression levels of IFN-γ. Our work stresses the importance of acknowledging immunological variation amongst individuals in studies of parasitological and infectious disease risk in wildlife populations.

Helicobacter suis induces changes in gastric inflammation and acid secretion markers in pigs of different ages

Gastric mRNA expression of markers for acid secretion and inflammation and presence of gastric ulceration was studied in naturally Helicobacter suis-infected and non-infected 2–3 months old, 6–8 months old and adult pigs. In H. suis-infected 2–3 months old pigs, IL-8 and IL-1β transcript levels were upregulated in the pyloric gland zone, indicating an innate immune response. A similar response was demonstrated in the fundic gland zone of adult pigs, potentially due to a shift of H. suis colonization from the pyloric to the fundic gland zone. A Treg response in combination with decreased expressions of IL-8, IL-17A and IFN-γ was indicated to be present in the H. suis-infected 6–8 months old pigs, which may have contributed to persistence of H. suis. In H. suis-infected adult pigs, a Treg response accompanied by a Th17 response was indicated, which may have played a role in the decreased number of H. suis bacteria in the stomach of this age group. The decreased G-cell mass and upregulated expression of somatostatin indicated decreased acid secretion in H. suis-infected 6–8 months old pigs. In H. suis-infected adult pigs, upregulation of most markers for gastric acid secretion and increased G-cell mass was detected. Presence of severe hyperkeratosis and erosions in the non-glandular part of the stomach were mainly seen in the H. suis-positive groups. These results show that H. suis infection affects the expression of markers for acid secretion and inflammation and indicate that these effects differ depending on the infection phase.

Species-specific immunity to Helicobacter suis

BACKGROUND

Helicobacter (H.) suis is mainly associated with pigs, but is also the most prevalent gastric non-H. pylori Helicobacter species found in humans. Both H. pylori and H. suis may cause persistent infection of the stomach. Several immune evasion mechanisms have been proposed for H. pylori, which focus to a great extent on its major virulence factors, which are absent in H. suis. The aim of this study was to gain more knowledge on immune evasion by H. suis.

MATERIALS AND METHODS

Cytokine expression kinetics were monitored in the stomach of BALB/c mice experimentally infected with H. suis. The cytokine expression profile in the stomach of naturally H. suis-infected pigs was also determined. Subsequently, the effect of H. suis on murine and porcine dendritic cell (DC) maturation and their ability to elicit T-cell effector responses was analyzed.

RESULTS

Despite a Th17/Th2 response in the murine stomach, the inflammatory cell influx was unable to clear H. suis infection. H. suis-stimulated murine bone marrow-derived dendritic cells induced IL-17 secretion by CD4⁺ cells in vitro. Natural H. suis infection in pigs evoked increased expression levels of IL-17 mRNA in the antrum and IL-10 mRNA in the fundus. In contrast to mice, H. suis-stimulated porcine monocyte-derived dendritic cells were unable to express MHCII molecules on their cell surface. These semimature DCs induced proliferation of T-cells, which showed an increased expression of TGF-β and FoxP3 mRNA levels.

CONCLUSIONS

Helicobacter suis might evade host immune responses by skewing toward a Treg-biased response.

Comparative virulence of in vitro-cultured primate- and pig-associated Helicobacter suis strains in a BALB/c mouse and a Mongolian gerbil model

BACKGROUND

Helicobacter suis (H. suis) is the most prevalent gastric non-H. pylori Helicobacter species in humans. This bacterium mainly colonizes the stomach of pigs, but it has also been detected in the stomach of nonhuman primates. The aim of this study was to obtain better insights into potential differences between pig- and primate-associated H. suis strains in virulence and pathogenesis.

MATERIALS AND METHODS

In vitro-isolated H. suis strains obtained from pigs, cynomolgus monkeys (Macaca fascicularis), and rhesus monkeys (Macaca mulatta) were used for intragastric inoculation of BALB/c mice and Mongolian gerbils. Nine weeks and six months later, samples of the stomach of inoculated and control animals were taken for PCR analysis and histopathological examination.

RESULTS

The cynomolgus monkey-associated H. suis strain only colonized the stomach of mice, but not of Mongolian gerbils. All other H. suis strains colonized the stomach in both rodent models. In all colonized animals, severe gastric inflammation was induced. Gastric lymphoid follicles and destruction of the antral epithelium were observed in infected gerbils, but not in mice. Infection with both pig- and primate-associated H. suis strains evoked a similar marked Th17 response in mice and gerbils, accompanied by increased CXCL-13 expression levels.

CONCLUSIONS

Apart from the cynomolgus monkey-associated strain which was unable of colonizing the stomach of Mongolian gerbils, no substantial differences in virulence were found in rodent models between in vitro-cultured pig-associated, cynomolgus monkey-associated and rhesus monkey-associated H. suis strains. The experimental host determines the outcome of the immune response against H. suis infection, rather than the original host.

In Silico Adjuvant Design and Validation

Adjuvants are substances that boost the protective immune response to vaccine antigens. The majority of known adjuvants have been identified through the use of empirical approaches. Our aim was to identify novel adjuvants with well-defined cellular and molecular mechanisms by combining a knowledge of immunoregulatory mechanisms with an in silico approach. CD4⁺CD25⁺FoxP3⁺ regulatory T cells (Tregs) inhibit the protective immune responses to vaccines by suppressing the activation of antigen presenting cells such as dendritic cells (DCs). In this chapter, we describe the identification and functional validation of small molecule antagonists to CCR4, a chemokine receptor expressed on Tregs. The CCR4 binds the chemokines CCL22 and CCL17 that are produced in large amounts by activated innate cells including DCs. In silico identified small molecule CCR4 antagonists inhibited the migration of Tregs both in vitro and in vivo and when combined with vaccine antigens, significantly enhanced protective immune responses in experimental models.

Helicobacter suis affects the health and function of porcine gastric parietal cells

The stomach of pigs at slaughter age is often colonized by Helicobacter (H.) suis, which is also the most prevalent gastric non-H. pylori Helicobacter (NHPH) species in humans. It is associated with chronic gastritis, gastric ulceration and other gastric pathological changes in both hosts. Parietal cells are highly specialized, terminally differentiated epithelial cells responsible for gastric acid secretion and regulation. Dysfunction of these cells is closely associated with gastric pathology and disease. Here we describe a method for isolation and culture of viable and responsive parietal cells from slaughterhouse pigs. In addition, we investigated the interactions between H. suis and gastric parietal cells both in H. suis-infected six-month-old slaughter pigs, as well as in our in vitro parietal cell model. A close interaction of H. suis and parietal cells was observed in the fundic region of stomachs from H. suis positive pigs. The bacterium was shown to be able to directly interfere with cultured porcine parietal cells, causing a significant impairment of cell viability. Transcriptional levels of Atp4a, essential for gastric acid secretion, showed a trend towards an up-regulation in H. suis positive pigs compared to H. suis-negative pigs. In addition, sonic hedgehog, an important factor involved in gastric epithelial differentiation, gastric mucosal repair, and stomach homeostasis, was also significantly up-regulated in H. suis positive pigs. In conclusion, this study describes a successful approach for the isolation and culture of porcine gastric parietal cells. The results indicate that H. suis affects the viability and function of this cell type.

Characterisation of inflammatory processes in Helicobacter pylori-induced gastric lymphomagenesis in a mouse model

Gastric MALT lymphoma (GML) can be induced by Helicobacter pylori infection in BALB/c mice thymectomised at day 3 post-birth (d3Tx). This represented a unique opportunity to investigate the inflammatory process involved in the recruitment, proliferation and structuration of lymphoid infiltrates in the gastric mucosa of mice developing GML. Complementary molecular and proteomic approaches demonstrated that Th1 and Th2 cytokines were upregulated, along with activators/regulators of the lymphoid response and numerous chemokines. Interleukin-4, interferon γ, lymphotoxin-α and -β were significantly upregulated and correlated with the inflammatory scores for all the d3Tx mice. GML lesions in d3Tx mice infected with H. pylori were associated with the presence of the inflammatory response. The dysregulation of numerous members of the tumour necrosis factor superfamily was also evident and suggests that they could play an important role in GML pathology, especially in light of their ability to promote and control lymphocyte proliferation.

Oral glutathione supplementation drastically reduces Helicobacter-induced gastric pathologies

Helicobacter (H.) suis causes gastric pathologies in both pigs and humans. Very little is known on the metabolism of this bacterium and its impact on the host. In this study, we have revealed the importance of the glutamate-generating metabolism, as shown by a complete depletion of glutamine (Gln) in the medium during H. suis culture. Besides Gln, H. suis can also convert glutathione (GSH) to glutamate, and both reactions are catalyzed by the H. suis γ-glutamyltranspeptidase (GGT). Both for H. pylori and H. suis, it has been hypothesized that the degradation of Gln and GSH may lead to a deficiency for the host, possibly initiating or promoting several pathologies. Therefore the in vivo effect of oral supplementation with Gln and GSH was assessed. Oral supplementation with Gln was shown to temper H. suis induced gastritis and epithelial (hyper)proliferation in Mongolian gerbils. Astonishingly, supplementation of the feed with GSH, another GGT substrate, resulted in inflammation and epithelial proliferation levels returning to baseline levels of uninfected controls. This indicates that Gln and GSH supplementation may help reducing tissue damage caused by Helicobacter infection in both humans and pigs, highlighting their potential as a supportive therapy during and after Helicobacter eradication therapy.

Effect of Different Adjuvants on Protection and Side-Effects Induced by Helicobacter suis Whole-Cell Lysate Vaccination

Helicobacter suis (H. suis) is a widespread porcine gastric pathogen, which is also of zoonotic importance. The first goal of this study was to investigate the efficacy of several vaccine adjuvants (CpG-DNA, Curdlan, Freund's Complete and Incomplete, Cholera toxin), administered either subcutaneously or intranasally along with H. suis whole-cell lysate, to protect against subsequent H. suis challenge in a BALB/c infection model. Subcutaneous immunization with Freund's complete (FC)/lysate and intranasal immunization with Cholera toxin (CT)/lysate were shown to be the best options for vaccination against H. suis, as determined by the amount of colonizing H. suis bacteria in the stomach, although adverse effects such as post-immunization gastritis/pseudo-pyloric metaplasia and increased mortality were observed, respectively. Therefore, we decided to test alternative strategies, including sublingual vaccine administration, to reduce the unwanted side-effects. A CCR4 antagonist that transiently inhibits the migration of regulatory T cells was also included as a new adjuvant in this second study. Results confirmed that immunization with CT (intranasally or sublingually) is among the most effective vaccination protocols, but increased mortality was still observed. In the groups immunized subcutaneously with FC/lysate and CCR4 antagonist/lysate, a significant protection was observed. Compared to the FC/lysate immunized group, gastric pseudo-pyloric metaplasia was less severe or even absent in the CCR4 antagonist/lysate immunized group. In general, an inverse correlation was observed between IFN-γ, IL-4, IL-17, KC, MIP-2 and LIX mRNA expression and H. suis colonization density, whereas lower IL-10 expression levels were observed in partially protected animals.

Purification of Helicobacter suis Strains From Biphasic Cultures by Single Colony Isolation: Influence on Strain Characteristics

BACKGROUND

Helicobacter (H.) suis causes gastritis and decreased weight gain in pigs. It is also the most prevalent non-Helicobacter pylori Helicobacter species in humans with gastric disease. H. suis is extremely fastidious, and so far, biphasic culture conditions were essential for isolation and culture, making it impossible to obtain single colonies. Hence, cultures obtained from an individual animal may contain multiple H. suis strains, which is undesirable for experiments aiming for instance at investigating H. suis strain differences.

MATERIALS AND METHODS

Pure cultures of H. suis were established by growing bacteria as colonies on 1% brucella agar plates, followed by purification and enrichment by biphasic subculture. Characteristics of these single colony-derived strains were compared with those of their parent strains using multilocus sequence typing (MLST) and by studying bacterium-host interactions using a gastric epithelial cell line and Mongolian gerbil model.

RESULTS

The purification/enrichment procedure required a nonstop culture of several weeks. For 4 of 17 H. suis strains, MLST revealed differences between parental and single colony-derived strains. For three of four single colony-derived strains tested, the cell death-inducing capacity was higher than for the parental strain. One single colony-derived strain lost its capacity to colonize Mongolian gerbils. For the four other strains tested, colonization capacity and histopathologic changes were similar to what has been described when using strains with only a history of limited biphasic culture.

CONCLUSIONS

A method was developed to obtain single colony-derived H. suis strains, but this procedure may affect the bacterial genotype and phenotype.

Role of γ-glutamyltranspeptidase in the pathogenesis of Helicobacter suis and Helicobacter pylori infections

Helicobacter (H.) suis can colonize the stomach of pigs as well as humans, causing chronic gastritis and other gastric pathological changes including gastric ulceration and mucosa-associated lymphoid tissue (MALT) lymphoma. Recently, a virulence factor of H. suis, γ-glutamyl transpeptidase (GGT), has been demonstrated to play an important role in the induction of human gastric epithelial cell death and modulation of lymphocyte proliferation depending on glutamine and glutathione catabolism. In the present study, the relevance of GGT in the pathogenesis of H. suis infection was studied in mouse and Mongolian gerbil models. In addition, the relative importance of H. suis GGT was compared with that of the H. pylori GGT. A significant and different contribution of the GGT of H. suis and H. pylori was seen in terms of bacterial colonization, inflammation and the evoked immune response. In contrast to H. pyloriΔggt strains, H. suisΔggt strains were capable of colonizing the stomach at levels comparable to WT strains, although they induced significantly less overall gastric inflammation in mice. This was characterized by lower numbers of T and B cells, and a lower level of epithelial cell proliferation. In general, compared to WT strain infection, ggt mutant strains of H. suis triggered lower levels of Th1 and Th17 signature cytokine expression. A pronounced upregulation of B-lymphocyte chemoattractant CXCL13 was observed, both in animals infected with WT and ggt mutant strains of H. suis. Interestingly, H. suis GGT was shown to affect the glutamine metabolism of gastric epithelium through downregulation of the glutamine transporter ASCT2.

Helicobacter heilmannii sensu lato: An overview of the infection in humans

Helicobacter heilmannii sensu lato (H. heilmannii s.l.) is a group of gastric non-Helicobacter pylori Helicobacter species that are morphologically indistinguishable from each other. H. heilmannii s.l. infect the stomach of several animals and may have zoonotic potential. Although the prevalence of these infections in humans is low, they are associated with gastric pathology, including mucosa-associated lymphoid tissue lymphoma, making them a significant health issue. Here, the taxonomy, epidemiology, microbiology, diagnosis, and treatment of these infections will be reviewed. The gastric pathology associated with H. heilmannii s.l. infections in humans will also be addressed. Finally, the features of the complete bacterial genomes available and studies on species-specific pathogenesis will be reviewed. The understanding of the mechanisms that underlie gastric disease development mediated by the different bacterial species that constitute H. heilmannii s.l. is essential for developing strategies for prevention and treatment of these infections.

Gastric de novo Muc13 expression and spasmolytic polypeptide-expressing metaplasia during Helicobacter heilmannii infection

Helicobacter heilmannii is a zoonotic bacterium that has been associated with gastric disease in humans. In this study, the mRNA expression of mucins in the stomach of BALB/c mice was analyzed at several time points during a 1-year infection with this bacterium, during which gastric disease progressed in severity. Markers for acid production by parietal cells and mucous metaplasia were also examined. In the first 9 weeks postinfection, the mRNA expression of Muc6 was clearly upregulated in both the antrum and fundus of the stomach of H. heilmannii-infected mice. Interestingly, Muc13 was upregulated already at 1 day postinfection in the fundus of the stomach. Its expression level remained high in the stomach over the course of the infection. This mucin is, however, not expressed in a healthy stomach, and high expression of this mucin has so far only been described in gastric cancer. In the later stages of infection, mRNA expression of H(+)/K(+)-ATPase α/β and KCNQ1 decreased, whereas the expression of Muc4, Tff2, Dmbt1, and polymeric immunoglobulin receptor (pIgR) increased starting at 16 weeks postinfection onwards, suggesting the existence of spasmolytic polypeptide-expressing metaplasia in the fundus of the stomach. Mucous metaplasia present in the mucosa surrounding low-grade mucosa-associated lymphoid tissue (MALT) lymphoma-like lesions was also histologically confirmed. Our findings indicate that H. heilmannii infection causes severe gastric pathologies and alterations in the expression pattern of gastric mucins, such as Muc6 and Muc13, as well as disrupting gastric homeostasis by inducing the loss of parietal cells, resulting in the development of mucous metaplasia.

Effects of Helicobacter suis γ-glutamyl transpeptidase on lymphocytes: modulation by glutamine and glutathione supplementation and outer membrane vesicles as a putative delivery route of the enzyme

Helicobacter (H.) suis colonizes the stomach of the majority of pigs as well as a minority of humans worldwide. Infection causes chronic inflammation in the stomach of the host, however without an effective clearance of the bacteria. Currently, no information is available about possible mechanisms H. suis utilizes to interfere with the host immune response. This study describes the effect on various lymphocytes of the γ-glutamyl transpeptidase (GGT) from H. suis. Compared to whole cell lysate from wild-type H. suis, lysate from a H. suis ggt mutant strain showed a decrease of the capacity to inhibit Jurkat T cell proliferation. Incubation of Jurkat T cells with recombinantly expressed H. suis GGT resulted in an impaired proliferation, and cell death was shown to be involved. A similar but more pronounced inhibitory effect was also seen on primary murine CD4(+) T cells, CD8(+) T cells, and CD19(+) B cells. Supplementation with known GGT substrates was able to modulate the observed effects. Glutamine restored normal proliferation of the cells, whereas supplementation with reduced glutathione strengthened the H. suis GGT-mediated inhibition of proliferation. H. suis GGT treatment abolished secretion of IL-4 and IL-17 by CD4(+) T cells, without affecting secretion of IFN-γ. Finally, H. suis outer membrane vesicles (OMV) were identified as a possible delivery route of H. suis GGT to lymphocytes residing in the deeper mucosal layers. Thus far, this study is the first to report that the effects on lymphocytes of this enzyme, not only important for H. suis metabolism but also for that of other Helicobacter species, depend on the degradation of two specific substrates: glutamine and reduced glutatione. This will provide new insights into the pathogenic mechanisms of H. suis infection in particular and infection with gastric helicobacters in general.

Gastric and enterohepatic non-Helicobacter pylori Helicobacters

A substantial number of reports published in the last year have contributed to a better understanding of both human and animal infection with non-Helicobacter pylori Helicobacter species (NHPH). Gastric infection of humans with Helicobacter suis and Helicobacter felis as well as unidentified NHPH has been described to cause a chronic gastritis and a variety of clinical symptoms, whereas enterohepatic NHPH, including Helicobacter cinaedi, Helicobacter bilis, and Helicobacter canis, have been reported to be associated with human diseases such as bacteremia, cellulitis, cutaneous diseases, and fever of unknown origin in immunocompromised hosts. In various animal species, including dogs and laboratory mice, high rates of infection with NHPH were described. For gastric NHPH, mainly H. suis and H. felis infection was studied, revealing that differences in the immune response evoked in the host do exist when compared to Helicobacter pylori. Pathogenic mechanisms of infection with Helicobacter pullorum, H. bilis, and Helicobacter hepaticus were investigated, as well as immune responses involved in H. bilis-, Helicobacter typhlonius-, and H. hepaticus-induced intestinal inflammation. Complete genome sequences of Helicobacter heilmannii strain ASB1 and a H. cinaedi strain isolated in a case of human bacteremia were published, as well as comparative genomics of a human-derived Helicobacter bizzozeronii strain and proteome or secretome analyses for H. hepaticus and Helicobacter trogontum, respectively. Molecular analysis has revealed a function for type VI secretion systems of H. hepaticus and H. pullorum, the Helicobacter mustelae iron urease, and several other functional components of NHPH. In each section of this chapter, new findings on gastric NHPH will first be discussed, followed by those on enterohepatic Helicobacter species.

Diversity in bacterium-host interactions within the species Helicobacter heilmannii sensu stricto

Helicobacter (H.) heilmannii sensu stricto (s.s.) is a zoonotic bacterium that naturally colonizes the stomach of dogs and cats. In humans, this microorganism has been associated with gastritis, peptic ulcer disease and mucosa associated lymphoid tissue (MALT) lymphoma. Little information is available about the pathogenesis of H. heilmannii s.s. infections in humans and it is unknown whether differences in virulence exist within this species. Therefore, a Mongolian gerbil model was used to study bacterium-host interactions of 9 H. heilmannii s.s. strains. The colonization ability of the strains, the intensity of gastritis and gene expression of various inflammatory cytokines in the stomach were determined at 9 weeks after experimental infection. The induction of an antrum-dominant chronic active gastritis with formation of lymphocytic aggregates was shown for 7 strains. High-level antral colonization was seen for 4 strains, while colonization of 4 other strains was more restricted and one strain was not detected in the stomach at 9 weeks post infection. All strains inducing a chronic active gastritis caused an up-regulation of the pro-inflammatory cytokine IL-1β in the antrum. A reduced antral expression of H⁺/K⁺ ATPase was seen in the stomach after infection with 3 highly colonizing strains and 2 highly colonizing strains caused an increased gastrin expression in the fundus. In none of the H. heilmannii s.s.-infected groups, IFN-γ expression was up-regulated. This study demonstrates diversity in bacterium-host interactions within the species H. heilmannii s.s. and that the pathogenesis of gastric infections with this microorganism is not identical to that of an H. pylori infection.

Protective efficacy of vaccines based on the Helicobacter suis urease subunit B and γ-glutamyl transpeptidase

Helicobacter suis causes gastric lesions in pigs and humans. This study aimed to evaluate the protective efficacy of immunization with combinations of the H. suis urease subunit B (UreB) and γ-glutamyl transpeptidase (GGT), both recombinantly expressed in Escherichia coli (rUreB and rGGT, respectively). Mice were intranasally immunized with rUreB, rGGT or a combination of both proteins, administered simultaneously or sequentially. Control groups consisted of non-immunized and non-challenged mice (negative controls), sham-immunized and H. suis-challenged mice (sham-immunized controls), and finally, H. suis whole-cell lysate-immunized and H. suis challenged mice. Cholera toxin was used as mucosal adjuvant. All immunizations induced a significant reduction of gastric H. suis colonization, which was least pronounced in the groups immunized with rGGT and rUreB only. Consecutive immunization with rGGT followed by rUreB and immunization with the bivalent vaccine improved the protective efficacy compared to immunization with single proteins, with a complete clearance of infection observed in 50% of the animals. Immunization with whole-cell lysate induced a similar reduction of gastric bacterial colonization compared to rGGT and rUreB in combinations. Gastric lesions, however, were less pronounced in mice immunized with combinations of rUreB and rGGT compared to mice immunized with whole-cell lysate. In conclusion, vaccination with a combination of rGGT and rUreB protected mice against a subsequent H. suis infection and was not associated with severe post-vaccination gastric inflammation, indicating that it may be a promising method for control of H. suis infections.

Multilocus sequence typing of the porcine and human gastric pathogen Helicobacter suis

Helicobacter suis is a Gram-negative bacterium colonizing the majority of pigs, in which it causes gastritis and decreased daily weight gain. H. suis is also the most prevalent gastric non-Helicobacter pylori Helicobacter species in humans, capable of causing gastric disorders. To gain insight into the genetic diversity of porcine and human H. suis strains, a multilocus sequence typing (MLST) method was developed. In a preliminary study, 7 housekeeping genes (atpA, efp, mutY, ppa, trpC, ureI, and yphC) of 10 H. suis isolates cultured in vitro were investigated as MLST candidates. All genes, except the ureI gene, which was replaced by part of the ureAB gene cluster of H. suis, displayed several variable nucleotide sites. Subsequently, internal gene fragments, ranging from 379 to 732 bp and comprising several variable nucleotide sites, were selected. For validation of the developed MLST technique, gastric tissue from 17 H. suis-positive pigs from 4 different herds and from 1 H. suis-infected human patient was used for direct, culture-independent strain typing of H. suis. In addition to the 10 unique sequence types (STs) among the 10 isolates grown in vitro, 15 additional STs could be assigned. Individual animals were colonized by only 1 H. suis strain, whereas multiple H. suis strains were present in all herds tested, revealing that H. suis is a genetically diverse bacterial species. The human H. suis strain showed a very close relationship to porcine strains. In conclusion, the developed MLST scheme may prove useful for direct, culture-independent typing of porcine and human H. suis strains.

Immunization with the immunodominant Helicobacter suis urease subunit B induces partial protection against H. suis infection in a mouse model

Helicobacter (H.) suis is a porcine and human gastric pathogen. Previous studies in mice showed that an H. suis infection does not result in protective immunity, whereas immunization with H. suis whole-cell lysate (lysate) protects against a subsequent experimental infection. Therefore, two-dimensional gel electrophoresis of H. suis proteins was performed followed by immunoblotting with pooled sera from H. suis- infected mice or mice immunized with lysate. Weak reactivity against H. suis proteins was observed in post-infection sera. Sera from lysate-immunized mice, however, showed immunoreactivity against a total of 19 protein spots which were identified using LC-MS/MS. The H. suis urease subunit B (UreB) showed most pronounced reactivity against sera from lysate-immunized mice and was not detected with sera from infected mice. None of the pooled sera detected H. suis neutrophil-activating protein A (NapA). The protective efficacy of intranasal vaccination of BALB/c mice with H. suis UreB and NapA, both recombinantly expressed in Escherichia coli (rUreB and rNapA, respectively), was compared with that of H. suis lysate. All vaccines contained choleratoxin as adjuvant. Immunization of mice with rUreB and lysate induced a significant reduction of H. suis colonization compared to non-vaccinated H. suis-infected controls, whereas rNapA had no significant protective effect. Probably, a combination of local Th1 and Th17 responses, complemented by antibody responses play a role in the protective immunity against H. suis infections.