Helicobacter pylori infection in the cat: evaluation of gastric colonization, inflammation and function

Pattern-recognition receptors and gastric cancer

Chronic inflammation has been associated with an increased risk of several human malignancies, a classic example being gastric adenocarcinoma (GC). Development of GC is known to result from infection of the gastric mucosa by Helicobacter pylori, which initially induces acute inflammation and, in a subset of patients, progresses over time to chronic inflammation, gastric atrophy, intestinal metaplasia, dysplasia, and finally intestinal-type GC. Germ-line encoded receptors known as pattern-recognition receptors (PRRs) are critical for generating mature pro-inflammatory cytokines that are crucial for both Th1 and Th2 responses. Given that H. pylori is initially targeted by PRRs, it is conceivable that dysfunction within genes of this arm of the immune system could modulate the host response against H. pylori infection, and subsequently influence the emergence of GC. Current evidence suggests that Toll-like receptors (TLRs) (TLR2, TLR3, TLR4, TLR5, and TLR9), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) (NOD1, NOD2, and NLRP3), a C-type lectin receptor (DC-SIGN), and retinoic acid-inducible gene (RIG)-I-like receptors (RIG-I and MDA-5), are involved in both the recognition of H. pylori and gastric carcinogenesis. In addition, polymorphisms in genes involved in the TLR (TLR1, TLR2, TLR4, TLR5, TLR9, and CD14) and NLR (NOD1, NOD2, NLRP3, NLRP12, NLRX1, CASP1, ASC, and CARD8) signaling pathways have been shown to modulate the risk of H. pylori infection, gastric precancerous lesions, and/or GC. Further, the modulation of PRRs has been suggested to suppress H. pylori-induced inflammation and enhance GC cell apoptosis, highlighting their potential relevance in GC therapeutics. In this review, we present current advances in our understanding of the role of the TLR and NLR signaling pathways in the pathogenesis of GC, address the involvement of other recently identified PRRs in GC, and discuss the potential implications of PRRs in GC immunotherapy.

Electron microscopic, genetic and protein expression analyses of Helicobacter acinonychis strains from a Bengal tiger

Colonization by Helicobacter species is commonly noted in many mammals. These infections often remain unrecognized, but can cause severe health complications or more subtle host immune perturbations. The aim of this study was to isolate and characterize putative novel Helicobacter spp. from Bengal tigers in Thailand. Morphological investigation (Gram-staining and electron microscopy) and genetic studies (16SrRNA, 23SrRNA, flagellin, urease and prophage gene analyses, RAPD DNA fingerprinting and restriction fragment polymorphisms) as well as Western blotting were used to characterize the isolated Helicobacters. Electron microscopy revealed spiral-shaped bacteria, which varied in length (2.5-6 µm) and contained up to four monopolar sheathed flagella. The 16SrRNA, 23SrRNA, sequencing and protein expression analyses identified novel H. acinonychis isolates closely related to H. pylori. These Asian isolates are genetically very similar to H. acinonychis strains of other big cats (cheetahs, lions, lion-tiger hybrid and other tigers) from North America and Europe, which is remarkable in the context of the great genetic diversity among worldwide H. pylori strains. We also found by immunoblotting that the Bengal tiger isolates express UreaseA/B, flagellin, BabA adhesin, neutrophil-activating protein NapA, HtrA protease, γ-glutamyl-transpeptidase GGT, Slt lytic transglycosylase and two DNA transfer relaxase orthologs that were known from H. pylori, but not the cag pathogenicity island, nor CagA, VacA, SabA, DupA or OipA proteins. These results give fresh insights into H. acinonychis genetics and the expression of potential pathogenicity-associated factors and their possible pathophysiological relevance in related gastric infections.

Gastric Helicobacter spp. in animal models: pathogenesis and modulation by extragastric coinfections

Animal models are used to study complex host, microbial, and environmental influences associated with gastric Helicobacter infection. Evidence that gastric helicobacters are pathogenic in animals first came from ferrets. Felids, nonhuman primates, and many other species also harbor stomach helicobacters. Today, mice are preferred by most researchers for scientific investigation because of cost-efficiencies, rapid reproduction, choice of laboratory reagents, and availability of genetically engineered models. Infection with Helicobacter felis or H. pylori Sydney strain-1 in appropriate mouse strains produces disease with remarkable similarities to H. pylori in humans. Due to recent advances in genetic engineering, in vivo imaging, and system-wide genomics and proteomics, these models will become even more widespread in the future. Recently, it has been shown that extragastric infections can dramatically affect the severity of disease induced by gastric Helicobacter spp. through heterologous immunity. These models provide proof-of-principle for the "African enigma" wherein gastric cancer is underrepresented in low-lying tropical countries with concurrently high H. pylori and internal parasite prevalence. Helicobacter gastritis and carcinogenesis in mouse models may be augmented or ameliorated by other infectious agents depending on the character of the invoked immune response. Knowledge gained from the Human Microbiome Project and other investigations is certain to shed new light on the influence of extragastric bacterial, viral, fungal, and parasitic coinfections on H. pylori-associated peptic ulcer disease and gastric adenocarcinoma.

Helicobacter spp. in cats: association between infecting species and epithelial proliferation within the gastric lamina propria

The aim of this study was to determine whether there is an association between Helicobacter spp. infection of the feline stomach and the presence of gastric lesions and epithelial proliferation within the mucosa of this tissue. The study included 23 pet cats of both sexes and of varied age and breed. Eighteen of these animals were clinically normal and five had a history of chronic vomiting. Samples of the mucosa of the pyloric antrum, corpus and fundus were collected by gastroscopy. The presence of Helicobacter spp. was confirmed by polymerase chain reaction (PCR) or Warthin-Starry (WS) staining and the species of Helicobacter was determined by PCR. Mucosal lesions were evaluated by examination of sections stained by haematoxylin and eosin (HE) and epithelial proliferation was determined by enumerating nucleolar organizer regions (AgNOR). In 20 (87%) cats the presence of Helicobacter spp. was confirmed by both PCR and WS. There was no significant difference in colonization density between the different gastric regions. H. heilmannii was the most frequently identified species (17 of 20 cats), and H. felis was only identified in co-infection (two of 17 cats). One sample that was PCR positive to the genus level for Helicobacter spp. was negative for the four individual species reactions. Histological changes in the lamina propria included mild mononuclear inflammatory infiltration, the presence of lymphoid follicles, fibrosis and glandular degeneration. These changes were most severe in the pyloric antrum. There was significant association between infection with gastric Helicobacter spp. and the presence of lymphoid follicles (P=0.03), and between infection and epithelial proliferation in the antrum (P<0.01), corpus (P<0.001) and fundus (P<0.001).

Survey of Helicobacter infection in domestic and feral cats in Korea

Discovery of Helicobacter (H.) pylori has led to a fundamental change in our understanding of gastric diseases in humans. Previous studies have found various Helicobacter spp. in dogs and cats, and pets have been questioned as a zoonotic carrier. The present study surveyed the Helicobacter infections and investigated the presence of H. felis and H. pylori infections in domestic and feral cats in Korea. Sixty-four domestic cats and 101 feral cats were selected from an animal shelter. Saliva and feces were evaluated by Helicobacter genus-specific polymerase chain reaction (PCR). Genus-specific PCR positive samples were further evaluated for H. felis and H. pylori using specific primer pairs. Thirty-six of 64 (56.3%) samples from domestic cats and 92 of 101 (91.1%) samples from feral cats were PCR positive; the positive rate of feces samples was higher than that of saliva samples in both groups. H. felis and H. pylori species-specific PCR was uniformly negative. The prevalence of Helicobacter spp. in feral cats was approximately two-fold higher than that of domestic cats. The fecal-oral route may be more a common transmission route not only between cats but also in humans.

Immunogenicity and pathogenicity of Helicobacter infections of veterinary animals

The initial discovery that the human stomach is commonly infected by the bacterium Helicobacter pylori subsequently resulted in the identification of a whole new family of pathogenic bacteria. In less than 25 years, the Helicobacter genus has grown from obscurity to number at least 38 different species with many more awaiting classifications. These bacteria, many of which are either direct or opportunistic pathogens, are present in virtually every mammalian species examined, and have also now been identified in a number of birds. The pathogenesis associated with these infections is predominantly the result of a chronic inflammatory response mounted by the host against the infection. This is typically a Th1-driven response which can result in a range of conditions from hepatitis, through gallstones to cancer. In some cases the inflammatory response to these infections is normally well managed by the host and disease only results when there is a breakdown or misbalance in the immunoregulatory process, which for example can result in inflammatory bowel disease in experimental models. Understanding the disease association and pathogenic mechanisms of the different Helicobacter infections is clearly of potential significance not only from an animal welfare point of view but also from the growing realisation of how commonly transmission of Helicobacter occurs between different mammals, including pathogenic zoonotic infections of humans.

N/A

N/A

Helicobacter-induced gastritis in mice not expressing metallothionein-I and II

BACKGROUND

Helicobacter pylori a primary cause of gastritis and peptic ulcer disease, is associated with increased production of reactive oxygen species within the gastric mucosa. Metallothionein (MT), a low-molecular-weight, cysteine-rich, metal-binding ligand, has been shown to sequester reactive oxygen species and reduce tissue damage. This study investigates the role of MT in H. pylori-induced gastritis in mice.

MATERIALS AND METHODS

Control (MT+/+) and MT-null (MT-/-) mice were inoculated with either 1 x 108H. pylori or H. felis, and were infected for 4, 8 and 16 weeks or 8 weeks, respectively. H. pylori load was determined by culture. Myloperoxidase activity and MT levels were also determined.

RESULTS

The stomachs of H. felis-infected mice were more severely inflamed than those of H. pylori-infected mice. H. felis-induced gastritis was more severe (p =.003) in MT-/- than in MT+/+ mice. MT-/- mice also had higher (60%; p <.05) H. pylori loads than MT+/+ mice 4 weeks after infection but not 8 or 16 weeks after infection. Myloperoxidase activity with H. pylori was similar between MT+/+ and MT-/- mice. Thirty-three per cent greater (p <.05) myloperoxidase activity was observed in MT-/- than in MT+/+ mice infected with H. felis. In MT+/+ mice infected with H. pylori, liver MT was increased by 33 and 39% (p <.05) at 8 and 16 weeks, respectively, whereas gastric MT increased by 46% (p <.05) at 4 weeks and declined to baseline levels at 8 and 16 weeks.

CONCLUSIONS

Mice lacking MT are more susceptible to H. pylori colonization and gastric inflammation, indicating that MT may be protective against H. pylori-induced gastritis.

Quantitative evaluation of inflammatory and immune responses in the early stages of chronic Helicobacter pylori infection

The early consequences of Helicobacter pylori infection and the role of bacterial virulence determinants in disease outcome remain to be established. The present study sought to measure the development of host inflammatory and immune responses and their relationship to the putative bacterial virulence factors cag pathogenicity island (cagPAI), vacA allele, and oipA in combination with bacterial colonization density in a feline model of the early stages of H. pylori infection. Gastric tissues obtained from infected and uninfected cats were evaluated for H. pylori ureB, cagPAI, vacA allele, and oipA and colonization density (urease, histology, and real-time PCR). Inflammation was assessed by measuring mRNA upregulation of gamma interferon (IFN-gamma), interleukin (IL)-1 alpha, IL-1 beta, IL-4, IL-6, IL-8, IL-10, and IL-12 p40 and histopathology. The mucosal immune response was characterized by morphometric analysis of lymphoid follicles and by differentiating lymphocyte populations with antibodies against surface markers. Infecting H. pylori strains were positive for vacAs1 but lacked cagPAI and an active oipA gene. Colonization density was uniform throughout the stomach. Upregulation of IFN-gamma, IL-1 alpha, IL-1 beta, and IL-8 and increased severity of inflammatory infiltrates and fibrosis were observed in infected cats. The median number and total area of lymphoid aggregates were 5 and 10 times greater, respectively, in the stomachs of infected than uninfected cats. Secondary lymphoid follicles in uninfected cats were rare and positive for BLA.36 and B220 but negative for CD3 and CD79 alpha, whereas in infected cats they were frequent and positive for BLA.36, CD79 alpha, and CD3 but negative for B220. Upregulation of IFN-gamma, IL-1 alpha, IL-1 beta, and IL-8 and marked hyperplasia of secondary lymphoid follicles are early consequences of H. pylori infection in cats. The response appears to be similar to that of infected people, particularly children, can develop independently of the pathogenicity factors cagPAI and oipA, and is not correlated with the degree of colonization density or urease activity.

Complement component anaphylatoxins upregulate chemokine expression by human astrocytes

The complement (C) system, a major component of the innate immune system, has been described as a factor implicated in some brain disorders. C activation leads to the release of anaphylatoxins, two proinflammatory polypeptides acting through specific receptors that have been detected on brain cells. Here, we examined the effect of anaphylatoxins on chemokine expression by human astrocytes. We showed that anaphylatoxins significantly increase chemokine mRNA expression. However, anaphylatoxin-induced chemokine secretion (interleukin-8) was observed only in the presence of interleukin-1beta. Thus, anaphylatoxins could initiate a chemokine cascade and, at least in part, be involved in pathogenesis of the brain.