A conventional beagle dog model for acute and chronic infection with Helicobacter pylori

G-protein-coupled estrogen receptor prevents nuclear factor-kappa B promoter activation by Helicobacter pylori cytotoxin-associated gene A in gastric cancer cells

Helicobacter pylori is a well-known pathogen that causes chronic gastritis, leading to the development of gastric cancer. This bacterium has also been detected in dogs, and symptoms similar to those in humans have been reported. The cytotoxin-associated gene A (CagA) is involved in pathogenesis through aberrant activation of host signal transduction, including the nuclear factor-kappa B (NF-κB) pathway. We have previously shown the anti-inflammatory effect of the G-protein-coupled estrogen receptor (GPER) via inhibiting of NF-κB activation in several cells. Therefore, here, we investigated the effect of GPER on CagA-mediated NF-κB promoter activity and showed that CagA overexpression in gastric cancer cells activated the NF-κB reporter and induced interleukin 8 (il-8) expression, both of which were inhibited by the GPER agonist.

What Kinds of Dogs Are Used in Clinical and Experimental Research?

Simple Summary

The objective of this study was to evaluate the signalment of dogs used in veterinary research in six different specialties. In total, 150 randomly chosen clinical studies (25 studies per specialty) published between 2007 and 2019 were evaluated for the breed, sex, neuter status, age, and weight information of the dogs used. Breed information was given for 5.7% of the included animals. Beagles were used 1.9% of the time, which was a less significant role in research than we expected. Information about the sex of the dogs was lacking for 16.2% of the included animals, while age and weight information were missing for 22.7 and 32.7%, respectively. The neuter status was not given in 38.7% of the clinical studies. The results show deficits in the reporting of demographic data for the dogs. The need for an improvement in the documentation and/or reporting of animal signalment is obvious and should be addressed by authors, reviewers, and journal editors in the future.

Abstract

Background: Dogs are widely used in research to answer questions about canine or human conditions. For the latter, research dogs are often used as models, since they are physiologically more similar to humans than other species used in research and they share similar environmental conditions. From a veterinary perspective, research findings are widely based on academic research, and thus are generated under experimental conditions. In that regard, the question arises: do the dogs used for research adequately represent the dog population seen in veterinary practice? It may, for example, be assumed that Beagle dogs are often used as experimental animals. The objective of this study was to evaluate the signalment of dogs used in veterinary research. Furthermore, we aimed to assess other relevant criteria regarding the validity of clinical trials in the context of six different veterinary medicine specialties: cardiology, internal medicine, neurology, orthopaedics, reproduction, and surgery. Methods: A literature search was conducted and 25 studies per specialty were randomly selected. The breed, sex, neuter status, median age, and median weight of the dogs used for clinical studies (n = 150) published between 2007 and 2019 were evaluated. Results: In total, 596,542 dogs were used in the 150 trials. Breed information was given for 33,835 of these dogs (5.7%). Of the latter, 1.9% were Beagles. Nine clinical trials exclusively used Beagles. The most frequently used breeds were German Shepherds (7.3%), Labrador Retrievers (6.7%), and Golden Retrievers (4.7%). The major reporting deficits found were missing breed specification in 25.3% of the articles; missing information about the sex of the dogs in 16.2%; missing age and weight information in 22.7 and 32.7%, respectively; and missing neuter status in 38.7% of the clinical studies. The median sample size was 56 (Q1:29; Q3:365) dogs. Conclusions: The presented project revealed that Beagle dogs represent only a small proportion of dogs in veterinary research. Based on the evaluated publications, it seems that some relevant dog attributes differ between the specialties. The results, however, show deficits in the reporting of demographic data for the dogs. The need for an improvement in the documentation and/or reporting of animal signalment is obvious and should be addressed by authors, reviewers, and journal editors in the future.

Chronic Stress-Related Gastroenteric Pathology in Cheetah: Relation between Intrinsic and Extrinsic Factors

Simple Summary

The cheetah is the fastest land mammal. Habitat destruction, high mortality due to other predators, and illegal wildlife trade has led to a decrease in the wild population. Currently, the global adult population present in their natural habitat is estimated to be 7100 individuals. In captivity, the population suffers from limited reproduction and disease. Both the wild and captive populations have reduced genetic diversity from a historic bottleneck, leading to increased ecological and environmental vulnerability. Over the years, conservation programs have been developed for habitat protection, management of human–animal conflict, and the study of disease and genetics. Among these, the one with the greatest prevalence in captivity is chronic gastritis. This review analyzes the scientific literature on gastric pathology in cheetah, with the potential causes divided into “extrinsic factors”, such as living conditions and diet, and “intrinsic factors”, including the presence of Helicobacter-like organisms and the genetic predisposition.

Abstract

The rapid decline of cheetah (Acinonyx jubatus) throughout their range and long-term studies of captive breeding has increased conservation action for this species including the study of chronic diseases. Gastritis is one of the captive diseases that leads to high mortality presented with symptoms including vomiting, diarrhea, anorexia, and weight loss. The disease presents different histological lesions in the gastrointestinal tract that are characterized by inconstant and different clinical appearance in captive and free-range cheetahs. The aim of this review is to summarize the causes of chronic gastritis in the cheetah. Factors including diet, living conditions, infections with gastric Helicobacter-like organisms (GHLOs), the lack of genetic polymorphism and the cheetah’s specific-immunocompetence are analyzed. All studies on gastroenteric cheetah pathologies, conducted between 1991 (to the best of our knowledge, the first report on online databases) and 2021, are included in this review, highlighting the possible correlation between stress-related captive conditions and chronic gastric pathology.

Canine Gastric Carcinomas: A Histopathological and Immunohistochemical Study and Similarities with the Human Counterpart

Simple Summary

Gastric carcinoma (GC) continues to be one of the leading causes of death in humans and is the most common neoplasm in the stomachs of dogs. In both species, previous studies have demonstrated that the disease is heterogeneous, with genetic and environmental factors playing a quintessential role in disease pathogenesis. Compared to humans, the incidence of gastric carcinoma in dogs is low although, in a small number of breeds, a higher incidence has been reported. In dogs, the etiology and molecular pathways involved remain largely unknown. This retrospective study reviews current signalment data, evaluates the inflammatory component and association with Helicobacter spp. presence in various canine gastric carcinoma histological subtypes, and investigates potential molecular pathways involved in one of the largest study cohorts to date. The benefit of such a comparative study is to highlight the parallel histological features and molecular pathways between dogs and humans.

Abstract

Canine gastric carcinoma (CGC) affects both sexes in relatively equal proportions, with a mean age of nine years, and the highest frequency in Staffordshire bull terriers. The most common histological subtype in 149 CGC cases was the undifferentiated carcinoma. CGCs were associated with increased chronic inflammation parameters and a greater chronic inflammatory score when Helicobacter spp. were present. Understanding the molecular pathways of gastric carcinoma is challenging. All markers showed variable expression for each subtype. Expression of the cell cycle regulator 14-3-3σ was positive in undifferentiated, tubular and papillary carcinomas. This demonstrates that 14-3-3σ could serve as an immunohistochemical marker in routine diagnosis and that mucinous, papillary and signet-ring cell (SRC) carcinomas follow a 14-3-3σ independent pathway. p16, another cell cycle regulator, showed increased expression in mucinous and SRC carcinomas. Expression of the adhesion molecules E-cadherin and CD44 appear context-dependent, with switching within tumor emboli potentially playing an important role in tumor cell survival, during invasion and metastasis. Within neoplastic emboli, acinar structures lacked expression of all markers, suggesting an independent molecular pathway that requires further investigation. These findings demonstrate similarities and differences between dogs and humans, albeit further clinicopathological data and molecular analysis are required.

Feline low-grade alimentary lymphoma: an emerging entity and a potential animal model for human disease

BACKGROUND

Low-grade alimentary lymphoma (LGAL) is characterised by the infiltration of neoplastic T-lymphocytes, typically in the small intestine. The incidence of LGAL has increased over the last ten years and it is now the most frequent digestive neoplasia in cats and comprises 60 to 75% of gastrointestinal lymphoma cases. Given that LGAL shares common clinical, paraclinical and ultrasonographic features with inflammatory bowel diseases, establishing a diagnosis is challenging. A review was designed to summarise current knowledge of the pathogenesis, diagnosis, prognosis and treatment of feline LGAL. Electronic searches of PubMed and Science Direct were carried out without date or language restrictions.

RESULTS

A total of 176 peer-reviewed documents were identified and most of which were published in the last twenty years. 130 studies were found from the veterinary literature and 46 from the human medicine literature. Heterogeneity of study designs and outcome measures made meta-analysis inappropriate. The pathophysiology of feline LGAL still needs to be elucidated, not least the putative roles of infectious agents, environmental factors as well as genetic events. The most common therapeutic strategy is combination treatment with prednisolone and chlorambucil, and prolonged remission can often be achieved. Developments in immunohistochemical analysis and clonality testing have improved the confidence of clinicians in obtaining a correct diagnosis between LGAL and IBD. The condition shares similarities with some diseases in humans, especially human indolent T-cell lymphoproliferative disorder of the gastrointestinal tract.

CONCLUSIONS

The pathophysiology of feline LGAL still needs to be elucidated and prospective studies as well as standardisation of therapeutic strategies are needed. A combination of conventional histopathology and immunohistochemistry remains the current gold-standard test, but clinicians should be cautious about reclassifying cats previously diagnosed with IBD to lymphoma on the basis of clonality testing. Importantly, feline LGAL could be considered to be a potential animal model for indolent digestive T-cell lymphoproliferative disorder, a rare condition in human medicine.

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.

PREVALÊNCIA DE Helicobacter spp. EM CÃES DE CAMPO GRANDE-MS

Resumo A Helicobacter spp. é uma bactéria Gram negativa espiralada, de grande importância clínica, que se relaciona a patogenias como gastrite e úlceras pépticas e, mais recentemente, com o carcinoma gástrico em humanos. Evidências sugerem o potencial dos animais, principalmente os domésticos, como fonte de infecção zoonótica das helicobactérias, já que bactérias com morfologia similar às encontradas em animais foram observadas no estômago de humanos com gastrite. Nesse contexto, os cães podem ser um importante reservatório de agentes infecciosos como a Helicobacter spp. O presente trabalho teve como objetivo avaliar a prevalência de Helicobacter spp. em cães do Centro de Controle de Zoonoses de Campo Grande/MS. Para tanto, foram utilizados 96 cães dos quais foram colhidas amostras do corpo, fundo e antro gástrico, para avaliação da presença da Helicobacter spp. por meio do teste rápido de urease e análise histológica. O teste rápido de urease permitiu a detecção de Helicobacter spp. em 94,7% dos cães; já a análise histológica indicou a presença de Helicobacter spp. em 100% dos animais avaliados com predominio da bactéria na região do fundo do estômago.

Design, Optimization, and Evaluation of a Novel Metronidazole-Loaded Gastro-Retentive pH-Sensitive Hydrogel

Floating pH-sensitive chitosan hydrogels containing metronidazole were developed for the eradication of Helicobacter pylori from the stomach. Hydrogels were prepared by crosslinking medium or high molecular weight chitosan in lyophilized solutions containing metronidazole using either citrate or tripolyphosphate (TPP) salts at 1% or 2% concentration. A 2³ factorial design was developed to study the influence of formulation parameters on the physical characteristics of the prepared hydrogels. The interaction between hydrogel components was investigated. The morphology of the prepared hydrogels was inspected and their percentage swelling, release pattern, and moisture content were evaluated. The results revealed the absence of interaction between hydrogel components and their highly porous structure. Percentage swelling of the hydrogels was much higher, and drug release was faster in gastric pH compared with intestinal pH. The formula prepared using 2% high molecular weight chitosan and 2% TPP significantly swelled (700%) within the first 4 h and released the loaded drug over a period of 24 h. Its moisture content was not affected by storage at high relative humidity. Therefore, this formula was selected to be tested in dogs for its gastric retention (using X-ray radiography) and efficacy in the eradication of H. pylori (using histopathological and microbiological examination). The results revealed that the prepared hydrogel formula was retained in dog stomach for at least 48 h, and it was more effective against H. pylori than the commercially available oral metronidazole tablets (Flagyl®).

Ecological characterization of the colonic microbiota of normal and diarrheic dogs

We used terminal restriction fragment polymorphism (T-RFLP) analysis to assess (1) stability of the fecal microbiota in dogs living in environments characterized by varying degrees of exposure to factors that might alter the microbiota and (2) changes in the microbiota associated with acute episodes of diarrhea. Results showed that the healthy canine GI tract harbors potential enteric pathogens. Dogs living in an environment providing minimal exposure to factors that might alter the microbiota had similar microbiotas; the microbiotas of dogs kept in more variable environments were more variable. Substantial changes in the microbiota occurred during diarrheic episodes, including increased levels of Clostridium perfringens, Enterococcus faecalis, and Enterococcus faecium. When diet and medications of a dog having a previously stable microbiota were changed repeatedly, the microbiota also changed repeatedly. Temporal trend analysis showed directional changes in the microbiota after perturbation, a return to the starting condition, and then fluctuating changes over time.

Safety and immunogenicity of an intramuscular Helicobacter pylori vaccine in noninfected volunteers: a phase I study

INTRODUCTION

Helicobacter pylori infection is among the most common human infections and the major risk factor for peptic disease and gastric cancer. Immunization with vaccines containing the H pylori vacuolating cytotoxin A (VacA), cytotoxin-associated antigen (CagA), and neutrophil-activating protein (NAP), alone or in combination, have been shown to prevent experimental infection in animals.

AIM

We sought to study the safety and immunogenicity of a vaccine consisting of recombinant VacA, CagA, and NAP given intramuscularly with aluminium hydroxide as an adjuvant to noninfected healthy subjects.

METHODS

This controlled, single-blind Phase I study randomized 57 H pylori-negative volunteers into 7 study arms exploring 2 dosages (10 and 25 microg) of each antigen and 3 schedules (0, 1, 2 weeks; 0, 1, 2 months; and 0, 1, 4 months) versus alum controls. All participants were followed for 5 months. Thirty-six subjects received a booster vaccination 18-24 months after the completion of the primary vaccination.

RESULTS

Local and systemic adverse reactions were mild and similar in placebo and vaccine recipients on the monthly schedules. All subjects responded to 1 or 2 of the antigens and 86% of all vaccines mounted immunoglobulin G antibody responses to all 3 antigens. Vaccinees exhibited an antigen-specific cellular response. Vaccination 18-24 months later elicited anamnestic antibody and cellular responses.

CONCLUSIONS

This intramuscular H pylori vaccine demonstrated satisfactory safety and immunogenicity, produced antigen-specific T-cell memory, and, therefore, warrants further clinical study.

Prevalência de Helicobacter em cães oriundos do biotério central da Universidade Estadual de São Paulo (UNESP)-Botucatu

OBJETIVO: Investigar a incidência de Helicobacter sp em cães oriundos do biotério central da UNESP. MÉTODOS: Utilizamos 109 cães oriundos do Biotério Central da UNESP Campus de Botucatu verificando a presença do Helicobacter sp através do exame de histopatologia corado pelo método Giemsa, pelo teste rápido de urease (TRU) e a prevalência de Helicobacter pylori pelo teste sorológico imunocromatográfico. RESULTADOS: O resultado para a presença de Helicobacter foi de 99% pela histopatologia e pelo TRU e 78,8% de prevalência para a espécie H. pylori pelo teste sorológico. CONCLUSÃO: As formas encontradas pela microscopia de imersão foram contrárias ao resultado do teste sorológico, sendo visibilzado formas compatíveis com a espécie H. heilmannii na maioria das amostras, e uma segunda forma de Helicobacter com características morfológicas distintas do H. pylori encontrado em humanos.

Therapeutic vaccination against Helicobacter pylori in the beagle dog experimental model: safety, immunogenicity, and efficacy

Helicobacter pylori is a gram-negative bacterium that colonizes the human gastric mucosa causing gastritis and peptic ulcer and increasing the risk of gastric cancer. The efficacy of current antibiotic-based therapies can be limited by problems of patient compliance and increasing antibiotic resistance; the vaccine approach can overcome these limits. The present study describes the therapeutic vaccination of experimentally H. pylori-infected beagle dogs, an animal model that reproduces several aspects of the human infection with H. pylori. The vaccine consisted of three recombinant H. pylori antigens, CagA, VacA, and NAP, formulated at different doses (10, 25, or 50 microg each) with alum and administered intramuscularly either weekly or monthly. No adverse effects were observed after vaccination and a good immunoglobulin G response was generated against each of the three antigens. Bacterial colonization and gastritis were decreased after the completion of the vaccination cycle, especially in the case of the monthly immunization schedule. In conclusion, therapeutic vaccination in the beagle dog model was safe and immunogenic and was able to limit H. pylori colonization and the related gastric pathology.

The quest for a vaccine against Helicobacter pylori: how to move from mouse to man?

Several lines of evidence from experimental animal models of infection have clearly demonstrated the feasibility of a prophylactic and therapeutic vaccine against Helicobacter pylori. However, comparatively few clinical studies have been carried out to evaluate whether the positive results obtained in animals can be reproduced in humans. The preliminary results obtained with single component, mucosally delivered vaccines have shown very limited results thus far. Very good immunogenicity and safety profiles are now being obtained with parenterally delivered, aluminium hydroxide-adjuvanted multicomponent candidate vaccines. For sure, better vaccine formulations, better antigen preparation(s), better adjuvants, and better delivery systems have to be designed and tested for safety and immunogenicity. These studies are also needed for deciphering those aspects of the effector immune responses that correlate with protection against H. pylori infection and disease.

Investigation of Helicobacter pylori in raw sheep milk samples

It is known that Helicobacter pylori is a cause of chronic gastritis and peptic ulcer disease in humans. However the origin and transmission of this bacterium has not been clearly explained. One of the suggested theories is transmission via raw milk from animals to human beings. In this study, the presence of H. pylori was investigated in sheep milk that is commonly consumed as human food. For this purpose, a total of 440 raw sheep milk samples collected from the Burdur region of Turkey were examined by specific cultural procedures, however, H. pylori was not isolated in any sample.

Effects of metronidazole, tetracycline, and bismuth-metronidazole-tetracycline triple therapy in the Helicobacter pylori SS1 mouse model after 1 day of dosing: development of an H. pylori lead selection model

We evaluated the effect of optimized doses and dosing schedules of metronidazole, tetracycline, and bismuth-metronidazole-tetracycline (BMT) triple therapy with only 1 day of dosing on Helicobacter pylori SS1 titers in a mouse model. A reduction of bacterial titers was observable with 22.5 and 112.5 mg of metronidazole per kg of body weight (as well as BMT) given twice daily and four times daily (QID). Two hundred milligrams of tetracycline per kilogram, given QID, resulted in only a slight reduction of H. pylori titers in the stomach. We argue that optimization of doses based on antimicrobial drug levels in the animal and shortened (1 or 2 days) drug administration can be used to facilitate early evaluation of putative anti-H. pylori drug candidates in lieu of using human doses and extended schedules (7 to 14 days), as can be deduced from the results seen with these antimicrobial agents.

Helicobacter pylori-induced gastritis in experimentally infected conventional piglets

A conventional nonmutant animal that could be experimentally infected with Helicobacter pylori isolates would be a useful animal model for human H. pylori-associated gastritis. Gnotobiotic and barrier-born pigs are susceptible to H. pylori infection, but attempts to infect conventional pigs with this bacterium have been unsuccessful. In the present study, a litter of eight 20-day-old crossbreed piglets were purchased from a commercial farm. Six of them were orally challenged two to five times at different ages, between 29 and 49 days, with doses of H. pylori inoculum containing approximately 10(9) bacterial cells. Two animals served as controls. The inoculation program began 2 days postweaning when the piglets were 29 days of age. Prior to every inoculation, the piglets were fasted and pretreated with cimetidine, and prior to the first and second inoculation each piglet also was pretreated with dexamethasone. The challenged piglets were euthanasized between 36 and 76 days of age. H. pylori colonized all six inoculated piglets. The pathology of the experimentally induced gastritis was examined macroscopically and by light and electron microscopy. H. pylori induced a severe lymphocytic gastritis in the conventional piglets and reproduced the large majority of the pathologic features of the human disease. Therefore, the conventional piglet represents a promising new model for study of the various pathogenic mechanisms involved in the development of lesions of the human H. pylori-associated gastritis.

The design of vaccines against Helicobacter pylori and their development

Helicobacter pylori is a gram negative, spiral, microaerophylic bacterium that infects the stomach of more than 50% of the human population worldwide. It is mostly acquired during childhood and, if not treated, persists chronically, causing chronic gastritis, peptic ulcer disease, and in some individuals, gastric adenocarcinoma and gastric B cell lymphoma. The current therapy, based on the use of a proton-pump inhibitor and antibiotics, is efficacious but faces problems such as patient compliance, antibiotic resistance, and possible recurrence of infection. The development of an efficacious vaccine against H. pylori would thus offer several advantages. Various approaches have been followed in the development of vaccines against H. pylori, most of which have been based on the use of selected antigens known to be involved in the pathogenesis of the infection, such as urease, the vacuolating cytotoxin (VacA), the cytotoxin-associated antigen (CagA), the neutrophil-activating protein (NAP), and others, and intended to confer protection prophylactically and/or therapeutically in animal models of infection. However, very little is known of the natural history of H. pylori infection and of the kinetics of the induced immune responses. Several lines of evidence suggest that H. pylori infection is accompanied by a pronounced Th1-type CD4(+) T cell response. It appears, however, that after immunization, the antigen-specific response is predominantly polarized toward a Th2-type response, with production of cytokines that can inhibit the activation of Th1 cells and of macrophages, and the production of proinflammatory cytokines. The exact effector mechanisms of protection induced after immunization are still poorly understood. The next couple of years will be crucial for the development of vaccines against H. pylori. Several trials are foreseen in humans, and expectations are that most of the questions being asked now on the host-microbe interactions will be answered.

Analysis of host responses of guinea pigs during Helicobacter pylori infection

Host responses of guinea pigs infected with Helicobacter pylori were investigated. Passaged H. pylori colonised the stomach for up to 13 weeks after infection, but after 1 month the number of bacteria fell sharply. Specific antibodies, predominantly of the IgG2 subtype, were present from week 3 onwards. Antibodies to urease A and flagella were abundant. Severe inflammation of the gastric mucosa and damage to the stomach epithelium was seen. Infiltrates of mononuclear cells and eosinophils were found near the parietal glands. As infection progressed, inflammation and tissue damage became more localised and more variable between individual animals. These parameters can be used as markers for colonisation of the stomach by H. pylori.

Immunohistochemical study of lymphocyte populations infiltrating the gastric mucosa of beagle dogs experimentally infected with Helicobacter pylori

Experimental infection of beagle dogs with Helicobacter pylori induces recruitment to the gastric mucosae of neutrophils at early stages and later of mononuclear cells that organize into lymphoid follicles. These structures become macroscopically evident and consist of peripheral CD4(+) T lymphocytes and central CD21(+) B lymphocytes. Furthermore, transient expression of interleukin-8 (IL-8) parallels the presence of neutrophils in the gastric mucosae, whereas expression of IL-6 tends to persist chronically.

Differences in genotypes of Helicobacter pylori from different human populations

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution.

Helicobacter pylori infection in wild-type and cytokine-deficient C57BL/6 and BALB/c mouse mutants

Helicobacter pylori causes gastroduodenal ulcer disease in humans. T lymphocytes and their cytokines are thought to play a substantial role in the control of H. pylori infection. To determine the importance of T helper (Th) cytokines and background genes we investigated the natural course of H. pylori infection in BALB/c and C57BL/6 wild-type or mutant mice deficient for either interleukin (IL)-4 or interferon (IFN)-gamma. H. pylori SPM 326 persisted for at least six months in C57BL/6 but was cleared by BALB/c wild-type mice nine weeks postinfection. H. pylori was recovered more frequently from IFN-gamma(-/-) BALB/c and IFN-gamma( -/-) C57BL/6 mice than from the respective wild-type animals. In contrast, IL-4 deficiency had no detectable effect on H. pylori recovery rates from either strain of mice. Our data suggest a protective role of IFN-gamma by mediating inflammation in murine H. pylori infection. In addition, our data emphasize that background genes which differ between BALB/c and C57BL/6 mice regulate the clearance of H. pylori.

The neutrophil-activating protein (HP-NAP) of Helicobacter pylori is a protective antigen and a major virulence factor

Helicobacter pylori infection induces the appearance of inflammatory infiltrates, consisting mainly of neutrophils and monocytes, in the human gastric mucosa. A bacterial protein with neutrophil activating activity (HP-NAP) has been previously identified, but its role in infection and immune response is still largely unknown. Here, we show that vaccination of mice with HP-NAP induces protection against H. pylori challenge, and that the majority of infected patients produce antibodies specific for HP-NAP, suggesting an important role of this factor in immunity. We also show that HP-NAP is chemotactic for human leukocytes and that it activates their NADPH oxidase to produce reactive oxygen intermediates, as demonstrated by the translocation of its cytosolic subunits to the plasma membrane, and by the lack of activity on chronic granulomatous disease leukocytes. This stimulating effect is strongly potentiated by tumor necrosis factor alpha and interferon gamma and is mediated by a rapid increase of the cytosolic calcium concentration. The activation of leukocytes induced by HP-NAP is completely inhibited by pertussis toxin, wortmannin, and PP1. On the basis of these results, we conclude that HP-NAP is a virulence factor important for the H. pylori pathogenic effects at the site of infection and a candidate antigen for vaccine development.

Tyrosine phosphorylation of the Helicobacter pylori CagA antigen after cag-driven host cell translocation

Helicobacter pylori strains associated with severe tissue damage and inflammation possess a unique genetic locus, cag, containing 31 genes originating from a distant event of horizontal transfer and retained as a pathogenicity island. The cag system is an Helicobacter-specific type IV secretion engine involved in cellular responses like induction of pedestals, secretion of IL-8, and phosphorylation of proteic targets. It has previously been reported that cocultivation of epithelial cells with Helicobacter pylori triggers signal transduction and tyrosine phosphorylation of a 145-kDa putative host cell protein. Herein, we demonstrate that this protein is not derived from the host but rather is the bacterial immunodominant antigen CagA, a virulence factor commonly expressed in peptic ulcer disease and thought to be an orphan of a specific biological function. Thus, CagA is delivered into the epithelial cells by the cag type IV secretion system where it is phosphorylated on tyrosine residues by an as yet unidentified host cell kinase and wired to eukaryotic signal transduction pathways and cytoskeletal plasticity.

Pathogenesis of Helicobacter pylori infection

Helicobacter pylori, a gram-negative, microaerophilic, motile, spiral-shaped bacterium, has been established as the etiologic agent of gastritis and peptic ulcers and is a major risk factor for gastric adenocarcinoma and mucosa-associated lymphoid tissue lymphoma (MALT). The ability of H. pylori to cause this spectrum of diseases depends on host, bacterial, and environmental factors. Bacterial factors critical for H. pylori colonization of the gastric mucosa include urease, flagella, adhesins, and delta-glutamyltranspeptidase. Lipopolysaccharide, urease, and vacuolating cytotoxin are among the factors that allow H. pylori to persist for decades and invoke an intense inflammatory response, leading to damaged host cells. Genes in the cag pathogenicity island also contribute to the inflammatory response by initiating a signal transduction cascade, resulting in interleukin-8 production. Proinflammatory cytokines and a Th-1 cytokine response further exacerbates the inflammation. Products of the enzymes nitric oxide synthase (iNOS) and cyclooxygenase may perturb the balance between gastric epithelial cell apoptosis (ulcer formation) and proliferation (cancer). The host Th-1 response and antibodies directed against H. pylori do not eliminate the organism, which presents challenges to vaccine development. Vaccines that include urease have shown some promise, but improved adjuvants and animal models should hasten progress in vaccine research. H. pylori is the most genetically diverse organism known, and the panmictic population structure may contribute to the varying ranges of disease severity produced by different strains. The complete genome sequence of two strains of H. pylori has propelled this field forward, and numerous groups are now using genomic, proteomic, and mutagenetic approaches to identify new virulence genes. Discovered only in 1982, H. pylori is now among the most intensely investigated organisms. This review summarizes recent progress in this rapidly moving field.

Helicobacter pylori virulence and genetic geography

Isolated for the first time in 1982 from human gastric biopsy, Helicobacter pylori is responsible for gastritis, peptic ulcer, and gastric cancer. A pathogenicity island acquired by horizontal transfer, coding for a type IV secretion system, is a major determinant of virulence. The infection is now treated with antibiotics, and vaccines are in preparation. The geographic distribution suggests coevolution of man and Helicobacter pylori.