Gastric B-cell mucosa-associated lymphoid tissue (MALT) lymphoma in an animal model of 'Helicobacter heilmannii' infection

The causal relationship between gut microbiota and lymphoma: a two-sample Mendelian randomization study

Background

Previous studies have indicated a potential link between the gut microbiota and lymphoma. However, the exact causal interplay between the two remains an area of ambiguity.

Methods

We performed a two-sample Mendelian randomization (MR) analysis to elucidate the causal relationship between gut microbiota and five types of lymphoma. The research drew upon microbiome data from a research project of 14,306 participants and lymphoma data encompassing 324,650 cases. Single-nucleotide polymorphisms were meticulously chosen as instrumental variables according to multiple stringent criteria. Five MR methodologies, including the inverse variance weighted approach, were utilized to assess the direct causal impact between the microbial exposures and lymphoma outcomes. Moreover, sensitivity analyses were carried out to robustly scrutinize and validate the potential presence of heterogeneity and pleiotropy, thereby ensuring the reliability and accuracy.

Results

We discerned 38 potential causal associations linking genetic predispositions within the gut microbiome to the development of lymphoma. A few of the more significant results are as follows: Genus Coprobacter (OR = 0.619, 95% CI 0.438-0.873, P = 0.006) demonstrated a potentially protective effect against Hodgkin's lymphoma (HL). Genus Alistipes (OR = 0.473, 95% CI 0.278-0.807, P = 0.006) was a protective factor for diffuse large B-cell lymphoma. Genus Ruminococcaceae (OR = 0.541, 95% CI 0.341-0.857, P = 0.009) exhibited suggestive protective effects against follicular lymphoma. Genus LachnospiraceaeUCG001 (OR = 0.354, 95% CI 0.198-0.631, P = 0.0004) showed protective properties against T/NK cell lymphoma. The Q test indicated an absence of heterogeneity, and the MR-Egger test did not show significant horizontal polytropy. Furthermore, the leave-one-out analysis failed to identify any SNP that exerted a substantial influence on the overall results.

Conclusion

Our study elucidates a definitive causal link between gut microbiota and lymphoma development, pinpointing specific microbial taxa with potential causative roles in lymphomagenesis, as well as identifying probiotic candidates that may impact disease progression, which provide new ideas for possible therapeutic approaches to lymphoma and clues to the pathogenesis of lymphoma.

Role of non-Helicobacter pylori gastric Helicobacters in helicobacter pylori-negative gastric mucosa-associated lymphoid tissue lymphoma

Marginal zone lymphomas rank as the third most prevalent form of non-Hodgkin B-cell lymphoma, trailing behind diffuse large B-cell lymphoma and follicular lymphoma. Gastric mucosa-associated lymphoid tissue lymphoma (GML) is a low-grade B-cell neoplasia frequently correlated with Helicobacter pylori (H. pylori)-induced chronic gastritis. On the other hand, a specific subset of individuals diagnosed with GML does not exhibit H. pylori infection. In contrast to its H. pylori-positive counterpart, it was previously believed that H. pylori-negative GML was less likely to respond to antimicrobial therapy. Despite this, surprisingly, in-creasing evidence supports that a considerable proportion of patients with H. pylori-negative GML show complete histopathological remission after bacterial eradication therapy. Nonetheless, the precise mechanisms underlying this treatment responsiveness are not yet fully comprehended. In recent years, there has been growing interest in investigating the role of non-H. pylori gastric helicobacters (NHPHs) in the pathogenesis of H. pylori-negative GML. However, additional research is required to establish the causal relationship between NHPHs and GML. In this minireview, we examined the current understanding and proposed prospects on the involvement of NHPHs in H. pylori-negative GML, as well as their potential response to bacterial eradication therapy.

Management of Extranodal Marginal Zone Lymphoma: Present and Upcoming Perspectives

Simple Summary

Extranodal marginal zone lymphoma distinguishes itself from other indolent lymphomas due to its unique pathophysiology and natural history. This is reflected in its management, where next to traditional treatment strategies such as observation, radiotherapy or chemotherapy, eradication of the causal agent and even surgery represent important aspects of therapy. This review focuses on the particular aspects of this indolent lymphoma that affect management and summarizes the current evidence and different guidelines.

Abstract

Extranodal marginal zone lymphoma (EMZL) encompasses a subgroup of non-Hodgkin lymphomas that often present with localized involvement and may manifest in a diversity of organs and tissues. EMZL pathogenesis is in some cases linked to chronic inflammation/infection, which may impose additional diagnostic and clinical challenges. The most studied and established connection is the presence of Helicobacter pylori in gastric EMZL. Due to its heterogeneity of presentation and intricate pathological features, treatment can be complex, and staging systems are decisive for the choice of therapy. Nevertheless, there is no consensus regarding the most suitable staging system, and recommendations vary among different countries. As a rule of thumb, in limited stages, a local therapy with surgery or radiation is the preferred option, and it is potentially curative. Of note, eradicating the causal agent may be an important step of treatment, especially in gastric EMZL, in which Helicobacter pylori eradication remains the first-line therapy for the majority of patients. In patients with more advanced stages, watch-and-wait is a valuable option, especially amongst those without clear indications for systemic therapy, and it may be carried on for several years. If watch-and-wait is not an option, systemic therapy may be needed. Even though several agents have been tested as monotherapy or in combination in recent years, there is no consensus regarding the first-line therapy, and decisions can vary depending on individual factors, such as age, clinical performance and stage. This review aims to discuss the several aspects of EMZL, including genetic milieu, pathogenesis and staging systems, that may influence the choice of therapy. In addition, we present a summary of evidence of several systemic therapies, compare different recommendations worldwide and discuss future perspectives and novelties in its therapy.

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.

The Role of Microbiota in the Development of Cancer Tumour Cells and Lymphoma of B and T Cells

Human body harbours enormous numbers of microbial organisms, including bacteria, viruses, and fungi which have a momentous role in well-being and illness in humans. Immune system shelters us from pathogenic bacteria, microorganisms found in human tissues have many benefits related to the functional movement of the host by regulating important procedures such as immunity, signalling, and breakdown. Lymphocytes assume a significant part in the reaction to bacterial colonization, primarily by prompting a safe reaction to obstruction or initiation. Most immunologically occupant cells have a place with the mucosal invulnerable framework and are continually motioned by dendritic cells or other Antigen introducing cells that gather intestinal samples. Thus, Microbiome is a key contributor to developing lymphoma and specific alterations to microbiome composition could attenuate the risk. There is an indication that microbial morphology can affect and control humanoids. The difference in the composition of these microorganisms is associated with tumour development. With the increased knowledge of the connection among the human microbiome and carcinogenesis, the use of these findings to prevent, predict or diagnose of lymphomas has attracted a great attention. In this article, we explored current knowledge of various microbial ecosystems, their connection with carcinogens and the potential for useful microorganisms to control and prevent B and T cell lymphoma.

Involvement of non-Helicobacter pylori helicobacter infections in Helicobacter pylori-negative gastric MALT lymphoma pathogenesis and efficacy of eradication therapy

BACKGROUND

Eradication therapy is known to be effective against Helicobacter pylori-positive gastric MALT lymphoma but predicting the efficacy of eradication therapy against Helicobacter pylori-negative gastric MALT lymphoma is difficult. Recent reports have shown that non-Helicobacter pylori helicobacter infections induce gastric MALT lymphoma, and we aimed to clarify whether non-Helicobacter pylori helicobacter infections are associated with the efficacy of eradication therapy.

METHODS

We analyzed eradication therapy as a first-line treatment for 182 cases of gastric MALT lymphoma, classified according to Helicobacter pylori infection and API2-MALT1 mutation status. We also evaluated the non-Helicobacter pylori helicobacter infection status in 29 Helicobacter pylori-negative cases via PCR with DNA extracted from paraffin-embedded biopsy tissues. Finally, we analyzed the relationship between non-Helicobacter pylori helicobacter infection status and eradication therapy outcome.

RESULTS

The API2-MALT1 mutation was observed in 13/182 patients (7.1%), none of whom were cured by eradication therapy. Helicobacter pylori-negative cases had a significantly higher non-Helicobacter pylori helicobacter infection rate than Helicobacter pylori-positive cases (16/29, 55% vs. 3/29, 10%; P < 0.05). Among the Helicobacter pylori-negative cases, non-Helicobacter pylori helicobacter-positive cases had a significantly higher complete response rate than non-Helicobacter pylori helicobacter-negative cases (12/16, 75% vs. 3/13, 23%; P < 0.05).

CONCLUSION

Helicobacter pylori-negative and API2-MALT1-negative gastric MALT lymphoma cases exhibited a high rate of non-Helicobacter pylori helicobacter infections, which may have contributed to the success of eradication therapy. Therefore, we recommend eradication therapy as a first-line treatment for non-Helicobacter pylori helicobacter-positive gastric MALT lymphoma.

Helicobacter suis Infection in Mouse Induced not Only Gastric, but Hepatic and Pulmonary MALT Lymphoma: Relation to Substance P

BACKGROUND

The hepatic and pulmonary MALT lymphoma (mucosa-associated lymphoid tissue lymphoma) is clinically occasionally observed but its pathogenesis is unknown and thought to be important to establish the treatment strategy.

OBJECTIVES

The present study was designed to clarify the characteristics of these lymphomas and the effect of the Helicobacter eradication regimen and substance P antagonist.

METHODS

After the long term infection of Helicobacter suis to the C57BL/6 mice stomach, the whole organ was surveyed pathologically. Histochemical characteristics of the lesion and the localization of bacteria were observed. In addition, the effect of the administration of antibiotics and a proton pump inhibitor or the substance P antagonist was investigated.

RESULTS

We have detected the hepatic and pulmonary MALT lymphoma after the long term infection. In situ hybridization study revealed the positive reaction of Helicobacter suis in the hepatic and pulmonary MALT lymphoma. After the administration of antibiotics and a proton pump inhibitor, the bacterial number has significantly decreased and the tumor size in the fundus, liver and lung markedly reduced. Substance P immunoreactivity was clearly shown in the lymphoma cells in the liver and lung, and the spantide II administration induced the marked decrease in the size of tumors.

CONCLUSION

By our experiments using the long term infection of Helicobacter suis to the C57BL/6 mice, we have detected the liver and pulmonary MALT lymphoma. In situ hybridization study suggested the direct interaction of this bacterium to the etiology of these lesions. Substance P within the lymphoma cells was suggested to work on the maintenance of the extragastric MALT lymphoma.

Clinical efficacy of the modified Helicobacter pylori eradication therapy for Helicobacter pylori-negative gastric mucosa-associated lymphoid tissue lymphoma: a meta analysis

Background

Helicobacter pylori (HP) has been considered to be one of the primary causes of gastric mucosa-associated lymphoid tissue (MALT) lymphoma since 1993. Low-grade gastric MALT lymphoma with HP is widely treated with HP eradication therapy, according to each specific clinical situation. However, several studies and guidelines indicate that the modified HP eradication therapy is also valid for HP-negative gastric MALT lymphoma. The aim of this study was to perform a meta-analysis of the clinical efficacy of the modified HP eradication therapy for gastric MALT lymphoma without HP.

Methods

We searched studies that reported the response rate of the modified HP eradication therapy regimen for gastric MALT lymphoma without HP by using PubMed, Medline, and Ebsco from January 1971 until February 2019. All statistical analyses were carried out using R 3.5.3 (Mathsoft Company, Cambridge, MA, USA). The pooled response rate was expressed as a decimal. The heterogeneity test was performed using the I-squared (I²) statistic.

Results

A total of 14 studies were selected with a total of 148 patients with HP-negative gastric MALT lymphoma. The overall pooled response rate was 0.38 (95% confidence interval [CI]: 0.29–0.47). The combined estimate is I² = 57% (P < 0.01). The study subjects were categorized by factors (area of patients). The pooled response rate of the sub-groups (Korea, Japan, China, and Western countries) was 0.63 (95% CI: 0.50–0.76), 0.16 (95% CI: 0.05–0.30), 0.38 (95% CI: 0.20–0.55), and 0.57 (95% CI: 0.08–1.00). The response rate showed that the modified HP eradication therapy was effective for patients with HP-negative gastric MALT lymphoma, especially in Korea and Western countries.

Conclusion

Therefore, the modified HP eradication therapy can be considered an optional therapy for patients with low-grade HP-negative gastric MALT lymphoma. However, several limitations were revealed in the meta-analysis. Further systematic reviews and research are required.

The draft genome of mandrill (Mandrillus sphinx): An Old World monkey

Mandrill (Mandrillus sphinx) is a primate species, which belongs to the Old World monkey (Cercopithecidae) family. It is closely related to human, serving as a model for human health related research. However, the genetic studies on and genomic resources of mandrill are limited, especially in comparison to other primate species. Here we produced 284 Gb data, providing 96-fold coverage (considering the estimated genome size of 2.9 Gb), to construct a reference genome for the mandrill. The assembled draft genome was 2.79 Gb with contig N50 of 20.48 Kb and scaffold N50 of 3.56 Mb. We annotated the mandrill genome to find 43.83% repeat elements, as well as 21,906 protein-coding genes. The draft genome was of good quality with 98% gene annotation coverage by Benchmarking Universal Single-Copy Orthologs (BUSCO). Based on comparative genomic analyses of  the Major Histocompatibility Complex (MHC) of the immune system in mandrill and human, we found that 17 genes in the mandrill that have been associated with disease phenotypes in human such as Lung cancer, cranial volume and asthma, barbored amino acids changing mutations. Gene family analyses revealed expansion of several genes, and several genes associated with stress environmental adaptation and innate immunity responses exhibited signatures of positive selection. In summary, we established the first draft genome of  the mandrill of value for studies on evolution and human health.

Helicobacter suis infection alters glycosylation and decreases the pathogen growth inhibiting effect and binding avidity of gastric mucins

Helicobacter suis is the most prevalent non-Helicobacter pylori Helicobacter species in the human stomach and is associated with chronic gastritis, peptic ulcer disease, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. H. suis colonizes the gastric mucosa of 60-95% of pigs at slaughter age, and is associated with chronic gastritis, decreased weight gain, and ulcers. Here, we show that experimental H. suis infection changes the mucin composition and glycosylation, decreasing the amount of H. suis-binding glycan structures in the pig gastric mucus niche. Similarly, the H. suis-binding ability of mucins from H. pylori-infected humans is lower than that of noninfected individuals. Furthermore, the H. suis growth-inhibiting effect of mucins from both noninfected humans and pigs is replaced by a growth-enhancing effect by mucins from infected individuals/pigs. Thus, Helicobacter spp. infections impair the mucus barrier by decreasing the H. suis-binding ability of the mucins and by decreasing the antiprolific activity that mucins can have on H. suis. Inhibition of these mucus-based defenses creates a more stable and inhabitable niche for H. suis. This is likely of importance for long-term colonization and outcome of infection, and reversing these impairments may have therapeutic benefits.

Novel Insights of Lymphomagenesis of Helicobacter pylori-Dependent Gastric Mucosa-Associated Lymphoid Tissue Lymphoma

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is the most common subtype of gastric lymphoma. Most gastric MALT lymphomas are characterized by their association with the Helicobacter pylori (HP) infection and are cured by first-line HP eradication therapy (HPE). Several studies have been conducted to investigate why most gastric MALT lymphomas remain localized, are dependent on HP infection, and show HP-specific intratumoral T-cells (e.g., CD40-mediated signaling, T-helper-2 (Th2)-type cytokines, chemokines, costimulatory molecules, and FOXP3+ regulatory T-cells) and their communication with B-cells. Furthermore, the reason why the antigen stimuli of these intratumoral T-cells with tonic B-cell receptor signaling promote lymphomagenesis of gastric MALT lymphoma has also been investigated. In addition to the aforementioned mechanisms, it has been demonstrated that the translocated HP cytotoxin-associated gene A (CagA) can promote B-cell proliferation through the activation of Src homology-2 domain-containing phosphatase (SHP-2) phosphorylation-dependent signaling, extracellular-signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), B-cell lymphoma (Bcl)-2, and Bcl-xL. Furthermore, the expression of CagA and these CagA-signaling molecules is closely associated with the HP-dependence of gastric MALT lymphomas (completely respond to first-line HPE). In this article, we summarize evidence of the classical theory of HP-reactive T-cells and the new paradigm of direct interaction between HP and B-cells that contributes to the HP-dependent lymphomagenesis of gastric MALT lymphomas. Although the role of first-line HPE in the treatment of HP-negative gastric MALT lymphoma remains uncertain, several case series suggest that a proportion of HP-negative gastric MALT lymphomas remains antibiotic-responsive and is cured by HPE. Considering the complicated interaction between microbiomes and the genome/epigenome, further studies on the precise mechanisms of HP- and other bacteria-directed lymphomagenesis in antibiotic-responsive gastric MALT lymphomas are warranted.

Helicobacter pylori-induced gastric pathology: insights from in vivo and ex vivo models

Gastric colonization with Helicobacter pylori induces diverse human pathological conditions, including superficial gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric adenocarcinoma and its precursors. The treatment of these conditions often relies on the eradication of H. pylori, an intervention that is increasingly difficult to achieve and that does not prevent disease progression in some contexts. There is, therefore, a pressing need to develop new experimental models of H. pylori-associated gastric pathology to support novel drug development in this field. Here, we review the current status of in vivo and ex vivo models of gastric H. pylori colonization, and of Helicobacter-induced gastric pathology, focusing on models of gastric pathology induced by H. pylori, Helicobacter felis and Helicobacter suis in rodents and large animals. We also discuss the more recent development of gastric organoid cultures from murine and human gastric tissue, as well as from human pluripotent stem cells, and the outcomes of H. pylori infection in these systems.

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.

The Helicobacter heilmannii hofE and hofF Genes are Essential for Colonization of the Gastric Mucosa and Play a Role in IL-1β-Induced Gastric MUC13 Expression

BACKGROUND

Helicobacter heilmannii is a zoonotic bacterium associated with gastric disease in humans. We recently showed that H. heilmannii binds to human gastric mucins and epithelial cells and highlighted a potential role for the murine Muc13 mucin in gastric Helicobacter colonization. The aims of this study were to investigate the role of the H. heilmannii hof gene locus encoding HofH/F/E/G/C/D in adhesion to the gastric mucosa and induction of increased gastric Muc13 expression.

METHODS

Bacterial hof gene and host gene expression experiments, Helicobacter binding assays and experimental infection studies in mice were performed. H. pylori and its ΔhofF mutant were included for comparison.

RESULTS

Helicobacter heilmannii strains lacking HofE or HofF showed a clear decrease in binding to gastric mucins and epithelial cells as well as a lower gastric colonization level in the stomach of Balb/c mice at 4 and 9 weeks post-infection compared to the H. heilmannii wildtype strain. Interestingly, H. heilmannii ΔhofE and ΔhofF and H. pylori ΔhofF did not induce an increased expression of MUC13 in human gastric epithelial cells and of Muc13 in the stomach of mice. Finally, we demonstrated that IL-1β is induced in the stomach as a response to Helicobacter colonization which on its turn is involved in the expression of MUC13/Muc13 in the gastric epithelium.

CONCLUSION

These novel results in Helicobacter research identified H. heilmannii HofE and HofF as adhesins and suggest an important role of H. heilmannii HofE and HofF and H. pylori HofF in IL-1β-induced gastric MUC13/Muc13 expression.

Interferon-γ promotes gastric lymphoid follicle formation but not gastritis in Helicobacter-infected BALB/c mice

Background

Mouse infection studies have shown that interferon-γ (IFN-γ), a T helper 1 (Th1) cytokine, is required for the development of severe pathology induced by chronic Helicobacter infection. This finding is largely based on studies performed using mice that have polarised Th1 responses i.e. C57BL/6 animals. The current work aims to investigate the role of IFN-γ in Helicobacter-induced inflammation in BALB/c mice which have Th2-polarised immune responses.

Results

At 7 months post-infection with Helicobacter felis, IFN-γ deficiency in BALB/c mice had no significant effect on H. felis colonisation levels in the gastric mucosa, nor on humoral responses, or gastritis severity. Ifng^−/− animals with chronic H. felis infection did, however, develop significantly fewer lymphoid follicle lesions, as well as increased IL-4 splenocyte responses, when compared with infected Ifng^+/+ mice (P = 0.015 and P = 0.0004, respectively).

Conclusions

The work shows that in mice on a BALB/c background, IFN-γ is not required for bacterial clearance, antibody responses, nor gastric inflammation. Conversely, IFN-γ appears to play a role in the development of gastric lymphoid follicles, which are precursor lesions to mucosa-associated lymphoid tissue (MALT) lymphoma. This study highlights the importance of mouse host background on the susceptibility to Helicobacter-induced pathologies.

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.

Helicobacter Species Identified in Captive Sooty Mangabeys (Cercocebus atys) with Metastatic Gastric Adenocarcinoma

BACKGROUND

Of all human cancers, gastric carcinoma is the one of the leading causes of death. Helicobacter pylori is considered a major etiologic agent of this disease. Spontaneously occurring gastric carcinoma is a rare diagnosis in nonhuman primates. A 2011 case report documented a high incidence of gastric adenocarcinoma in a closed colony of captive sooty mangabeys (Cercebus atys). However, H. pylori infection was not detected in these animals.

MATERIALS AND METHODS

In this study, using archived formalin-fixed, paraffin-embedded stomach sections of these animals alternative methodologies were used to identify H. pylori and other non-H. pylori Helicobacter species. In addition, two additional cases of sooty mangabeys with metastatic gastric carcinoma are characterized.

RESULTS

Using fluorescent in situ hybridization, we identified gastric H. suis in 75% of archived and new gastric carcinoma cases. In the two newly reported cases, H. suis and a novel Helicobacter species were detected via PCR and sequence analysis of the 16S rRNA gene. H. pylori was not identified in any of the gastric carcinoma cases via FISH and/or PCR and sequence analysis of Helicobacter spp. in DNA from of available tissues.

CONCLUSIONS

This report is the first to characterize Helicobacter species infection in spontaneous gastric carcinoma with metastatic potential in nonhuman primates.

Male Syrian Hamsters Experimentally Infected with Helicobacter spp. of the H. bilis Cluster Develop MALT-Associated Gastrointestinal Lymphomas

BACKGROUND

Aged hamsters naturally infected with novel Helicobacter spp. classified in the H. bilis cluster develop hepatobiliary lesions and typhlocolitis.

METHODS

To determine whether enterohepatic H. spp. contribute to disease, Helicobacter-free hamsters were experimentally infected with H. spp. after suppression of intestinal bacteria by tetracycline treatment of dams and pups. After antibiotic withdrawal, weanlings were gavaged with four H. bilis-like Helicobacter spp. isolated from hamsters or H. bilis ATCC 43879 isolated from human feces and compared to controls (n = 7 per group).

RESULTS

Helicobacter bilis 43879-dosed hamsters were necropsied at 33 weeks postinfection (WPI) due to the lack of detectable infection by fecal PCR; at necropsy, 5 of 7 were weakly PCR positive but lacked intestinal lesions. The remaining hamsters were maintained for ~95 WPI; chronic H. spp. infection in hamsters (6/7) was confirmed by PCR, bacterial culture, fluorescent in situ hybridization, and ELISA. Hamsters had mild-to-moderate typhlitis, and three of the male H. spp.-infected hamsters developed small intestinal lymphoma, in contrast to one control. Of the three lymphomas in H. spp.-infected hamsters, one was a focal ileal mucosa-associated lymphoid tissue (MALT) B-cell lymphoma, while the other two were multicentric small intestinal large B-cell lymphomas involving both the MALT and extra-MALT mucosal sites with lymphoepithelial lesions. The lymphoma in the control hamster was a diffuse small intestinal lymphoma with a mixed population of T and B cells.

CONCLUSIONS

Results suggest persistent H. spp. infection may augment risk for gastrointestinal MALT origin lymphomas. This model is consistent with H. pylori/heilmannii-associated MALT lymphoma in humans and could be further utilized to investigate the mechanisms of intestinal lymphoma development.

Comparison of in vivo confocal endomicroscopy with other diagnostic modalities to detect intracellular helicobacters

Intracellular colonisation may serve as a protected niche where Helicobacter spp. organisms evade effective treatment. In dogs, non-Helicobacter pylori-helicobacters are frequently intracellular. Confocal endomicroscopy allows in vivo gastrointestinal imaging and has aided real-time identification of Helicobacter pylori and other intracellular and mucosally associated bacteria. The objectives of this study were: (1) to determine the utility of confocal endomicroscopy to identify non-Helicobacter pylori-helicobacters compared with other diagnostic modalities, and (2) to assess its ability to identify intracellular organisms. Fourteen clinically healthy dogs underwent standard gastroduodenoscopy followed by confocal endomicroscopy using topical acriflavine. Confocal images were obtained from at least five gastric sites. Endoscopic biopsies were obtained for histopathology, PCR and fluorescence in situ hybridisation (FISH). Methodologies were compared for their ability to determine the presence and spatial distribution of gastric helicobacters in dogs. Confocal endomicroscopy provided high quality images allowing in vivo identification of non-Helicobacter pylori-helicobacters in 13 dogs. Histopathology identified helicobacters in 11 dogs. Organisms were identified within the superficial gastric mucus and within gastric pits, and distribution throughout the stomach was diffuse and multi-focal. Confocal endomicroscopy findings correlated with PCR and FISH post-procedure analysis. Only FISH identified intracellular organisms, which were present in 13/14 dogs. Confocal endomicroscopy provided in vivo histology images and was capable of identifying non-Helicobacter pylori-helicobacters during gastroscopy, but was unable to identify intracellular organisms using the current fluorophore protocol.

Divergence between the Highly Virulent Zoonotic Pathogen Helicobacter heilmannii and Its Closest Relative, the Low-Virulence "Helicobacter ailurogastricus" sp. nov

Helicobacter heilmannii naturally colonizes the stomachs of dogs and cats and has been associated with gastric disorders in humans. Nine feline Helicobacter strains, classified as H. heilmannii based on ureAB and 16S rRNA gene sequences, were divided into a highly virulent and a low-virulence group. The genomes of these strains were sequenced to investigate their phylogenetic relationships, to define their gene content and diversity, and to determine if the differences in pathogenicity were associated with the presence or absence of potential virulence genes. The capacities of these helicobacters to bind to the gastric mucosa were investigated as well. Our analyses revealed that the low-virulence strains do not belong to the species H. heilmannii but to a novel, closely related species for which we propose the name Helicobacter ailurogastricus. Several homologs of H. pylori virulence factors, such as IceA1, HrgA, and jhp0562-like glycosyltransferase, are present in H. heilmannii but absent in H. ailurogastricus. Both species contain a VacA-like autotransporter, for which the passenger domain is remarkably larger in H. ailurogastricus than in H. heilmannii. In addition, H. ailurogastricus shows clear differences in binding to the gastric mucosa compared to H. heilmannii. These findings highlight the low-virulence character of this novel Helicobacter species.

Helicobacter pylori-negative gastric mucosa-associated lymphoid tissue lymphomas: A review

Since Isaacson and Wright first reported on the extra-nodal marginal zone B-cell lymphoma of the stomach in 1983, following studies have clarified many aspects of this disease. We now know that the stomach is the most affected organ by this disease, and approximately 90% of gastric mucosa-associated lymphoid tissue (MALT) lymphomas are related to Helicobacter pylori (H. pylori) infection. This implies that approximately 10% of gastric MALT lymphomas occur independent of H. pylori infection. The pathogenesis of these H. pylori-negative gastric MALT lymphomas remains unclear. To date, there have been several speculations. One possibility is that genetic alterations result in nuclear factor-kappa B (NF-κB) activation. Among these alterations, t(11;18)(q21;q21) is more frequently observed in H. pylori-negative gastric MALT lymphomas, and such translocation results in the synthesis of fusion protein API2-MALT1, which causes canonical and noncanonical NF-κB activation. Another possibility is infection with bacteria other than H. pylori. This could explain why H. pylori eradication therapy can cure some proportions of H. pylori-negative gastric MALT lymphoma patients, although the bacteria responsible for MALT lymphomagenesis are yet to be defined. Recent advances in endoscopy suggest magnifying endoscopy with narrow band imaging as a useful tool for both detecting gastric MALT lymphoma lesions and judging the response to treatment. A certain proportion of H. pylori-negative gastric MALT lymphoma patients respond to eradication therapy; hence, H. pylori eradication therapy could be considered as a first-line treatment for gastric MALT lymphomas regardless of their H. pylori infection status.

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.

Intestinal microbiome and lymphoma development

The intestinal microbiota and gut immune system must communicate to maintain a balance between tolerance and activation. Our immune system protects us from pathogenic microbes at the same time that our bodies are host to trillions of microbes, symbionts, mutualists, and some that are essential to human health. Since there is such a close interaction between the immune system and the intestinal microbiota, it is not surprising that some lymphomas such as mucosal-associated lymphoid tissue lymphoma have been shown to be caused by the presence of certain bacteria. Animal models have played an important role in elucidating the causation and establishing the mechanism of bacteria-induced mucosal-associated lymphoid tissue lymphoma. In this review, we discuss different ways that animal models have been applied to investigate links between the gut microbiota and lymphoma and have helped to reveal the mechanisms of microbiota-induced lymphoma. Although there is a paucity of published studies demonstrating the interplay between the microbiota and lymphoma development, we believe that the connection is real and that it can be exploited in the future to enhance our understanding of causation and to improve the prognosis and treatment of lymphoma.

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.

Anti-CXCL13 antibody can inhibit the formation of gastric lymphoid follicles induced by Helicobacter infection

Helicobacter suis infects the stomachs of both animals and humans, and can induce gastric mucosa-associated lymphoid tissue (MALT) lymphomas. It is known that CXC chemokine ligand 13 (CXCL13) is highly expressed in the Helicobacter-infected mice and gastric MALT lymphoma patients, but the pathway that links the activation of CXCL13 and the formation of gastric MALT lymphomas remains unclear. In this study, we examined whether CXCL13 neutralization would interfere with the formation of gastric lymphoid follicles including B cells, CD4+T cells, dendritic cells (DCs), and follicular DCs (FDCs) in germinal centers to determine the role of CXCL13 in the formation of B-cell aggregates after H. suis infection. Moreover, the expression of genes associated with the lymphoid follicle formation was also effectively suppressed by anti-CXCL13 antibody treatment. These results suggest that the upregulation of CXCL13 has an important role in the development of gastric MALT lymphomas and highlight the potential of anti-CXCL13 antibody for protection against Helicobacter-induced gastric diseases.

Lymphoma caused by intestinal microbiota

The intestinal microbiota and gut immune system must constantly communicate to maintain a balance between tolerance and activation: on the one hand, our immune system should protect us from pathogenic microbes and on the other hand, most of the millions of microbes in and on our body are innocuous symbionts and some can even be beneficial. Since there is such a close interaction between the immune system and the intestinal microbiota, it is not surprising that some lymphomas such as mucosal-associated lymphoid tissue (MALT) lymphoma have been shown to be caused by the presence of certain bacteria. Animal models played an important role in establishing causation and mechanism of bacteria-induced MALT lymphoma. In this review we discuss different ways that animal models have been applied to establish a link between the gut microbiota and lymphoma and how animal models have helped to elucidate mechanisms of microbiota-induced lymphoma. While there are not a plethora of studies demonstrating a connection between microbiota and lymphoma development, we believe that animal models are a system which can be exploited in the future to enhance our understanding of causation and improve prognosis and treatment of lymphoma.

Neonatal thymectomy favors Helicobacter pylori-promoted gastric mucosa-associated lymphoid tissue lymphoma lesions in BALB/c mice

Neonatal thymectomy in BALB/c mice has been described as a model of gastric mucosa-associated lymphoid tissue (MALT) lymphoma (GML). By using this experimental system, we screened, for the first time to our knowledge, Helicobacter pylori GML-associated strains for their capacity to promote disease. A cohort of BALB/c mice underwent thymectomy at day 3 after birth (d3Tx). Successful thymic ablation was evaluated by the degree of lymphopenia in blood samples collected at 4 weeks of age. d3Tx and non-thymectomized controls were infected with either GML strains (B38 or B47) or control strains (SS1 or TN2GF4). Gastric samples collected at 6, 12, and 18 months after infection were studied for bacteria content, and submitted to histological, immunochemical, molecular, and immunological analyses. Severe gastric inflammation was only observed in d3Tx mice. In these animals, the gastric lamina propria was infiltrated with lymphoid cells organized in follicles composed of B cells with few infiltrating T cells. PCR of D/J IgH gene segments proved the monoclonality of infiltrating B cells, which strongly correlated with the presence of lymphoepithelial lesions. B-cell infiltrates were particularly prominent in mice infected with the B47-GML strain. No pathological changes were detected in noninfected d3Tx mice. We identified new H. pylori isolates adapted to the mouse stomach with high potential of GML development, which is only revealed in hosts rendered lymphopenic by neonatal thymic ablation.

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.

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.

Verifying and quantifying Helicobacter pylori infection status of research mice

Mice used to model helicobacter gastritis should be screened by PCR prior to experimental dosing to confirm the absence of enterohepatic Helicobacter species (EHS) that colonize the cecum and colon of mice. Natural infections with EHS are common and impact of concurrent EHS infection on Helicobacter pylori-induced gastric pathology has been demonstrated.PCR of DNA isolated from gastric tissue is the most sensitive and efficient technique to confirm the H. pylori infection status of research mice after experimental dosing. To determine the level of colonization, quantitative PCR to estimate the equivalent colony-forming units of H. pylori per μg of mouse DNA is less labor-intensive than limiting dilution culture methods. Culture recovery of H. pylori is a less sensitive technique due to its fastidious in vitro culture requirements; however, recovery of viable organisms confirms persistent colonization and allows for further molecular characterization of wild-type or mutant H. pylori strains. ELISA is useful to confirm PCR and culture results and to correlate pro- and anti-inflammatory host immune responses with lesion severity and cytokine gene or protein expression. Histologic assessment with a silver stain has a role in identifying gastric bacteria with spiral morphology consistent with H. pylori but is a relatively insensitive technique and lacks specificity. A variety of spiral bacteria colonizing the lower bowel of mice can be observed in the stomach, particularly if gastric atrophy develops, and these species are not morphologically distinct at the level of light microscopy either in the stomach or lower bowel. Other less commonly used techniques to localize H. pylori in tissues include immunohistochemistry using labeled polyclonal antisera or in situ hybridization for H. pylori rRNA. In this chapter, we will summarize strategies to allow initiation of experiments with helicobacter-free mice and then focus on PCR and ELISA techniques to verify and quantify H. pylori infection of research mice.

Neonatal Fc receptor for IgG (FcRn) expressed in the gastric epithelium regulates bacterial infection in mice

Neonatal Fc receptors for immunoglobulin (Ig)G (FcRn) assume a central role in regulating host IgG levels and IgG transport across polarized epithelial barriers. We have attempted to elucidate the contribution of FcRn in controlling Helicobacter infection in the stomach. C57BL/6J wild-type or FcRn(-/-) mice were infected with Helicobacter heilmannii, and gastric lesions, bacterial load and the levels of antigen-specific IgG in serum and gastric juice were analyzed. The elevated levels of anti-H. heimannii IgG in gastric juice were observed exclusively in wild-type mice but not in FcRn(-/-) mice. In contrast, an increase in lymphoid follicles and bacterial loads along with deeper gastric epithelium invasion were noted in FcRn(-/-) mice. C57BL/6J wild-type or FcRn(-/-) mice were also infected with Helicobacter pylori SS1, and the results of the bacterial load in stomachs of these mice and the anti-H. pylori IgG levels in serum and gastric juice were similar to those from H. heilmannii infection. Our data suggest that FcRn can be functionally expressed in the stomach, which is involved in transcytosis of IgG, and prevent colonization by H. heilmannii and the associated pathological consequences of infection.

IFN-γ plays an essential role in the pathogenesis of gastric lymphoid follicles formation caused by Helicobacter suis infection

In this study, we aimed to assess the role of helper T cells in the development of gastric lymphoid follicles induced by Helicobacter suis infection. C57BL/6J mice were orally inoculated with H. suis. Six weeks after infection, gastric lymphoid follicles were observed in the gastric mucosa by hematoxylin and eosin staining, and the number of follicles was increased throughout the infection period. An immunohistological examination showed that the lymphoid follicles were composed of B cells, CD4-positive helper T cells, and dendritic cells (DC). It was also revealed that the mRNA expression level of interferon-γ (IFN-γ) in the gastric mucosa was significantly increased at 12 weeks after infection. No gastric lymphoid follicles were detected in IFN-γ-deficient mice that had been infected with H. suis at 12 weeks after infection, although the development of lymphoid follicles in IL-4-deficient mice infected with H. suis was similar to that seen in the wild-type mice. In conclusion, IFN-γ, a Th1 cytokine, is deeply involved in the pathogenesis of gastric lymphoid follicles induced by H. suis infection, and it is suggested that CD4-positive T cells and DC aid in the expansion of gastric lymphoid follicles.

Helicobacter heilmannii sp. nov., isolated from feline gastric mucosa

Three gram-negative, microaerophilic bacteria, strains ASB1(T), ASB2 and ASB3, with a corkscrew-like morphology isolated from the gastric mucosa of cats were studied using a polyphasic taxonomic approach. The isolates grew on biphasic culture plates under microaerobic conditions at 37 °C and exhibited urease, oxidase and catalase activities. They were also able to grow in colonies on dry agar plates. Based on 16S rRNA gene sequence analysis, ASB1(T), ASB2 and ASB3 were identified as members of the genus Helicobacter and showed 98 to 99 % sequence similarity to strains of Helicobacter felis, Helicobacter bizzozeronii, 'Candidatus Helicobacter heilmannii', Helicobacter cynogastricus, Helicobacter baculiformis and Helicobacter salomonis, six related Helicobacter species previously detected in feline or canine gastric mucosa. Sequencing of the partial hsp60 gene demonstrated that ASB1(T), ASB2 and ASB3 constitute a separate taxon among the feline and canine Helicobacter species. The urease gene sequences of ASB1(T), ASB2 and ASB3 showed approximately 91 % similarity to those of 'Candidatus Helicobacter heilmannii'. Protein profiling, the absence of alkaline phosphatase activity and several other biochemical characteristics also allowed strains ASB1(T), ASB2 and ASB3 to be differentiated from other Helicobacter species of feline or canine gastric origin. The results of this polyphasic taxonomic study show that the cultured isolates constitute a new taxon corresponding to 'Candidatus Helicobacter heilmannii', which was previously demonstrated in the stomach of humans, wild felidae, cats and dogs. The name Helicobacter heilmannii sp. nov. is proposed for these isolates; the type strain is ASB1(T) (=DSM 24751 (T) =LMG 26292(T)) [corrected].

Induction of high endothelial venule-like vessels expressing GlcNAc6ST-1-mediated L-selectin ligand carbohydrate and mucosal addressin cell adhesion molecule 1 (MAdCAM-1) in a mouse model of "Candidatus Helicobacter heilmannii"-induced gastritis and gastric mucosa-associated lymphoid tissue (MALT) lymphoma

BACKGROUND

"Candidatus Helicobacter heilmannii" induce chronic gastritis, which eventually leads to gastric B-cell type mucosa-associated lymphoid tissue (MALT) lymphoma. This study was performed using an animal model of infection with "Candidatus Helicobacter heilmannii" to elucidate how this chronic inflammation is induced or maintained.

MATERIALS AND METHODS

BALB/c mice were infected with the "Candidatus Helicobacter heilmannii" isolate SH4. The animals were examined at 8, 26, 54, and 83 weeks after the infection. The stomach of the animals was resected and immunostained for peripheral lymph node addressin (PNAd) and mucosal addressin cell adhesion molecule 1 (MAdCAM-1), "Candidatus Helicobacter heilmannii," and CD45R/B220. An in vitro binding assay with L- and E-selectin·IgM chimeric proteins was performed. Real-time polymerase chain reaction was used to evaluate transcripts of N-acetylglucosamine-6-O-sulfotransferases (GlcNAc6STs), which direct the expression of the PNAd and MAdCAM-1.

RESULTS

Chronic gastritis developed in the infected animals, and its severity increased with the duration of the infection. B-cell type MALT lymphoma developed in some animals at 54 and 83 weeks after infection. PNAd- and MAdCAM-1-expressing high endothelial venule (HEV)-like vessels were induced in infected animals which developed chronic gastritis and MALT lymphoma. The number of HEV-like vessels increased as chronic inflammation progressed. The induced HEV-like vessels were bound by L- and E-selectin·IgM chimeric protein. mRNA expressions of GlcNAc6ST-1 and MAdCAM-1 increased in the infected animals.

CONCLUSIONS

HEV-like vessels expressing GlcNAc6ST-1-mediated L-selectin ligand carbohydrate and MAdCAM-1 may play a crucial role in the pathogenesis of "Candidatus Helicobacter heilmannii"-induced chronic gastritis and MALT lymphoma.

Helicobacter suis causes severe gastric pathology in mouse and mongolian gerbil models of human gastric disease

BACKGROUND

"Helicobacter (H.) heilmannii" type 1 is the most prevalent gastric non-H. pylori Helicobacter species in humans suffering from gastric disease. It has been shown to be identical to H. suis, a bacterium which is mainly associated with pigs. To obtain better insights into the long-term pathogenesis of infections with this micro-organism, experimental infections were carried out in different rodent models.

METHODOLOGY/PRINCIPAL FINDINGS

Mongolian gerbils and mice of two strains (BALB/c and C57BL/6) were infected with H. suis and sacrificed at 3 weeks, 9 weeks and 8 months after infection. Gastric tissue samples were collected for PCR analysis, histological and ultrastructural examination. In gerbils, bacteria mainly colonized the antrum and a narrow zone in the fundus near the forestomach/stomach transition zone. In both mice strains, bacteria colonized the entire glandular stomach. Colonization with H. suis was associated with necrosis of parietal cells in all three animal strains. From 9 weeks after infection onwards, an increased proliferation rate of mucosal epithelial cells was detected in the stomach regions colonized with H. suis. Most gerbils showed a marked lymphocytic infiltration in the antrum and in the forestomach/stomach transition zone, becoming more pronounced in the course of time. At 8 months post infection, severe destruction of the normal antral architecture at the inflamed sites and development of mucosa-associated lymphoid tissue (MALT) lymphoma-like lesions were observed in some gerbils. In mice, the inflammatory response was less pronounced than in gerbils, consisting mainly of mononuclear cell infiltration and being most severe in the fundus.

CONCLUSIONS/SIGNIFICANCE

H. suis causes death of parietal cells, epithelial cell hyperproliferation and severe inflammation in mice and Mongolian gerbil models of human gastric disease. Moreover, MALT lymphoma-like lesions were induced in H. suis-infected Mongolian gerbils. Therefore, the possible involvement of this micro-organism in human gastric disease should not be neglected.

Gastric helicobacters in domestic animals and nonhuman primates and their significance for human health

Helicobacters other than Helicobacter pylori have been associated with gastritis, gastric ulcers, and gastric mucosa-associated lymphoid tissue lymphoma in humans. These very fastidious microorganisms with a typical large spiral-shaped morphology were provisionally designated "H. heilmannii," but in fact they comprise at least five different Helicobacter species, all of which are known to colonize the gastric mucosa of animals. H. suis, which has been isolated from the stomachs of pigs, is the most prevalent gastric non-H. pylori Helicobacter species in humans. Other gastric non-H. pylori helicobacters colonizing the human stomach are H. felis, H. salomonis, H. bizzozeronii, and the still-uncultivable "Candidatus Helicobacter heilmannii." These microorganisms are often detected in the stomachs of dogs and cats. "Candidatus Helicobacter bovis" is highly prevalent in the abomasums of cattle but has only occasionally been detected in the stomachs of humans. There are clear indications that gastric non-H. pylori Helicobacter infections in humans originate from animals, and it is likely that transmission to humans occurs through direct contact. Little is known about the virulence factors of these microorganisms. The recent successes with in vitro isolation of non-H. pylori helicobacters from domestic animals open new perspectives for studying these microorganisms and their interactions with the host.

Chronic inflammatory disease, lymphoid tissue neogenesis and extranodal marginal zone B-cell lymphomas

Chronic autoimmune or pathogen-induced immune reactions resulting in lymphoid neogenesis are associated with development of malignant lymphomas, mostly extranodal marginal zone B-cell lymphomas (MZBCLs). In this review we address (i) chemokines and adhesion molecules involved in lymphoid neogenesis; (ii) the autoimmune diseases and pathogens which are associated with development of B-cell lymphomas; (iii) the molecular mechanisms involved in the initiation and progression of MZBCL; and (iv) 'potential' mouse models for MZBCL.

Non-Helicobacter pylori helicobacters detected in the stomach of humans comprise several naturally occurring Helicobacter species in animals

Besides the well-known gastric pathogen Helicobacter pylori, other Helicobacter species with a spiral morphology have been detected in a minority of human patients who have undergone gastroscopy. The very fastidious nature of these non-Helicobacter pylori helicobacters (NHPH) makes their in vitro isolation difficult. These organisms have been designated 'Helicobacter heilmannii'. However, sequencing of several genes detected in NHPH-infected tissues has shown that the 'H. heilmannii' group comprises at least five different Helicobacter species, all of them known to colonize the stomach of animals. Recent investigations have indicated that Helicobacter suis is the most prevalent NHPH species in human. This species has only recently been isolated in vitro from porcine stomach mucosa. Other NHPH that colonize the human stomach are Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis and 'Candidatus Helicobacter heilmannii'. In numerous case reports of human gastric NHPH infections, no substantial information is available about the species status of the infecting strain, making it difficult to link the species with certain pathologies. This review aims to clarify the complex nomenclature of NHPH species associated with human gastric disease and their possible animal origin. It is proposed to use the term 'gastric NHPH' to designate gastric spirals that are morphologically different from H. pylori when no identification is available at the species level. Species designations should be reserved for those situations in which the species is defined.

Gene expression profiling in Helicobacter-induced MALT lymphoma with reference to antigen drive and protective immunization

We have previously shown that long-term infection of BALB/c mice with gastric Helicobacter species results in the development of histopathological lesions that resemble those seen in patients diagnosed with gastric mucosa associated lymphoid tissue (MALT) lymphoma. This paper describes analysis of this disease at the molecular level through the use of microarray technology and immunohistochemical staining. We were able to monitor the genetic changes in the gastric mucosa characterized by distinct transcriptional signatures and correlate these with histological changes as the infection progressed from a chronic inflammatory infiltrate through to MALT lymphoma. This model system also enabled us to further dissect the role of antigen presentation and prophylactic immunization in the disease process. Antimicrobial therapy to eradicate the antigen correlated with significant reduction in pathology and major changes in the gene expression profile. Subsequent reintroduction of the antigen resulted in rapid tumor development which correlated with an increase in aggressively proliferating cells and changes in the cellular composition of the tumor. The response in vaccinated animals showed that the protected animals exhibited a strikingly different transcriptional profile compared to those of non-protected or control mice, indicating that the vaccination targeted the appropriate site leaving a long-lasting signature. The genes which were most significantly up-regulated included a number of adipocyte-specific factors, such as fat-cell specific cytokines and adipocyte surface markers. This study allowed for us to highlight the significance of antigen presentation in this disease and to hypothesis mechanisms associated with protective immunity.

Gastric lesions and immune responses caused by long-term infection with Helicobacter heilmannii in C57BL/6 mice

Helicobacter heilmannii is a gastric micro-organism that can induce gastritis and B-cell MALT (mucosa-associated lymphoid tissue) lymphoma in mice, in a host-dependent manner. The present study was designed to examine gastric lesions and immune responses caused by intragastric H. heilmannii infection of an inbred mouse strain, C57BL/6. Long-term infection led to the formation of gastric nodules and increased mucosal thickness of the stomach, due to gastric epithelial proliferation. Infection also induced the formation of lymphoid follicles in the corpus mucosa and submucosa. The follicular cells were mainly CD45R+ cells that did not produce immunoglobulin. However, scattered in the lamina propria and corpus submucosa, numerous IgA+ cells were found in infected mice, but not in control mice. RT-PCR results showed that H. heilmannii infection led to increased mRNA expression for IFN-gamma (a Th1 cytokine) and IL-10 (a Th2 cytokine) in the mouse stomach, suggesting that both Th1 and Th2 responses are associated with H. heilmannii infection. The mRNA of other cytokines and chemokines (IL-1beta, IL-12p40, TNF-alpha, MCP-1, KC and MIP-2) was also increased by infection.

Isolation and characterization of Helicobacter suis sp. nov. from pig stomachs

A new cultivation method was successfully applied for the in vitro isolation of a hitherto uncultured spiral Helicobacter species associated with ulceration of the non-glandular stomach and gastritis in pigs and formerly described as 'Candidatus Helicobacter suis'. Three isolates, HS1(T), HS2 and HS3, were subcultured from the stomach mucosa of three pigs after slaughter and were analysed using a polyphasic taxonomic approach. The novel isolates grew on biphasic culture plates or very moist agar bases in microaerobic conditions and exhibited urease, oxidase and catalase activities. Sequencing of the 16S rRNA gene, the 23S rRNA gene, the partial hsp60 gene and partial ureAB genes confirmed that the strains present in the gastric mucosa of pigs constituted a separate taxon, corresponding to 'Helicobacter heilmannii' type 1 strains as detected in the gastric mucosa of humans and other primates. For all genes sequenced, the highest sequence similarities were obtained with Helicobacter felis, Helicobacter bizzozeronii and Helicobacter salomonis, Helicobacter species isolated from the gastric mucosa of dogs and cats, which have also been detected in the human gastric mucosa and which are commonly referred to as 'Helicobacter heilmannii' type 2. SDS-PAGE of whole-cell proteins of strains HS1(T), HS2 and HS3 differentiated them from other Helicobacter species of gastric origin. The results of the polyphasic taxonomic analysis confirmed that the novel isolates constitute a novel taxon corresponding to 'Helicobacter heilmannii' type 1 strains from humans and to 'Candidatus H. suis' from pigs. The name Helicobacter suis sp. nov. is proposed for the novel isolates with the type strain HS1(T) (=LMG 23995(T)=DSM 19735(T)).

Primary gastric mucosa associated lymphoid tissue lymphoma: Clinical data predicted treatment outcome

AIM: To determine clinical characteristics and treatment outcome of gastric lymphoma after chemotherapy and immuno-chemotherapy.

METHODS: Thirty four patients with primary gastric mucosa associated lymphoid tissue (MALT) lymphoma (Ann Arbor stages I to IV) were enrolled. All had upper gastric endoscopy, abdominal ultrasonography, CT and H pylori status assessment (histology and serology). After anti-H pylori treatment and initial chemotherapy, patients were re-examined every 4 mo.

RESULTS: Histological regression of the lymphoma was complete in 22/34 (64.7%) and partial in 9 (26.5%) patients. Median follow up time for these 31 responders was 60 mo (range 48-120). No regression was noted in 3 patients. Among the 25 (73.5%) H pylori positive patients, the eradication rate was 100%.

CONCLUSION: Using univariate analysis, predictive factors for overall survival were international prognostic index (IPI) score, hemoglobin level, erythrocyte sedimentation rate (ESR), and platelet numbers (P < 0.005). In addition to this, Cox proportion hazard model differentiate IPI score, ESR, and platelets as predictors of survival.