Transient and persistent experimental infection of nonhuman primates with Helicobacter pylori: implications for human disease

Animal Models of Helicobacter pylori Infection and Vaccines: Current Status and Future Prospects

Helicobacter pylori infection causes chronic gastritis, ulcers, and gastric cancer, making it a threat to human health. Despite the use of antibiotic therapy, the global prevalence of H. pylori infection remains high, necessitating early eradication measures. Immunotherapy, especially vaccine development, is a promising solution in this direction, albeit the selection of an appropriate animal model is critical in efficient vaccine production. Accordingly, we conducted a literature, search and summarized the commonly used H. pylori strains, H. pylori infection-related animal models, and models for evaluating H. pylori vaccines. Based on factors such as the ability to replicate human diseases, strain compatibility, vaccine types, and eliciting of immune responses, we systematically compared the advantages and disadvantages of different animal models, to obtain the informed recommendations. In addition, we have proposed novel perspectives on H. pylori-related animal models to advance research and vaccine evaluation for the prevention and treatment of diseases such as gastric cancer.

Animal Models and Helicobacter pylori Infection

Helicobacter pylori colonize the gastric mucosa of at least half of the world’s population. Persistent infection is associated with the development of gastritis, peptic ulcer disease, and an increased risk of gastric cancer and gastric-mucosa-associated lymphoid tissue (MALT) lymphoma. In vivo studies using several animal models have provided crucial evidence for understanding the pathophysiology of H. pylori-associated complications. Numerous animal models, such as Mongolian gerbils, transgenic mouse models, guinea pigs, and other animals, including non-human primates, are being widely used due to their persistent association in causing gastric complications. However, finding suitable animal models for in vivo experimentation to understand the pathophysiology of gastric cancer and MALT lymphoma is a complicated task. In this review, we summarized the most appropriate and latest information in the scientific literature to understand the role and importance of H. pylori infection animal models.

Helicobacter pylori adhesins: HpaA a potential antigen in experimental vaccines for H. pylori

BACKGROUND

Helicobacter pylori is a gram-negative bacterium involved in many gastric pathologies such as ulcers and cancers. Although the treatment for this infection has existed for several years, the development of a vaccine is nevertheless necessary to reduce the severe forms of the disease. For more than three decades, many advances have been made particularly in the understanding of virulence factors as well as the pathogenesis of gastric diseases caused by H. pylori. Among these key virulence factors, specific antigens have been identified: Urease, Vacuolating cytotoxin A (VacA), Cytotoxin-associated gene A (CagA), Blood group antigen-binding adhesin (BabA), H. pylori adhesin A (HpaA), and others.

OBJECTIVES

This review will focus on H. pylori adhesins, in particular, on HpaA and on the current knowledge of H. pylori vaccines.

METHODS

All of the information included in this review was retrieved from published studies on H. pylori adhesins in H. pylori infections.

RESULTS

These proteins, used in their native or recombinant forms, induce protection against H. pylori in experimental animal models.

CONCLUSION

H. pylori adhesins are known to be promising candidate vaccines against H. pylori. Future research should be carried out on adhesins, in particular, on HpaA.

Evaluation of the guaiac fecal occult blood test for detection of gastrointestinal bleeding in the rhesus macaque (Macaca mulatta)

BACKGROUND

Gastrointestinal (GI) hemorrhage accompanies several common diseases of rhesus macaques (Macaca mulatta). Guaiac fecal occult blood testing (gFOBT) is a non-invasive means to detect such bleeding in several species; however, there are currently no data indicating reliability of this test to detect GI hemorrhage in macaques.

METHODS

We evaluated sensitivity and specificity of gFOBT to detect simulated and biopsy-associated bleeding in the stomach, duodenum, and colon of 15 rhesus macaques. Fecal samples were analyzed via gFOBT for 72 hours.

RESULTS

Guaiac fecal occult blood testing was more sensitive to detect lower vs upper GI bleeding; sensitivity was volume-dependent in the upper GI tract. Single-test specificity was 95.2%. Repeated fecal collections increased gFOBT sensitivity without affecting specificity.

CONCLUSIONS

Guaiac fecal occult blood testing is a useful screening test for both upper and lower GI bleeding in rhesus macaques. For highest sensitivity, gFOBT should be performed on three fecal samples collected 24 hours apart.

Helicobacter pylori outer membrane vesicles involvement in the infection development and Helicobacter pylori-related diseases

Helicobacter pylori - (H. pylori) play a role in the pathogenesis of gastritis, gastric and duodenal ulcers as well as gastric cancer. A possible involvement of outer membrane vesicles (OMVs) produced by H. pylori in the distribution of bacterial antigens through the gastric epithelial barrier and their role in the development of local and systemic host inflammatory and immune responses has been suggested. OMVs contain various biologically active compounds, which internalize into host cells affecting signaling pathways and promoting apoptosis of gastric epithelial and immunocompetent cells. OMVs-associated H. pylori virulence factors may strengthen or downregulate the immune responses leading to disease development. This review describes the biological importance of H. pylori OMVs and their role in the course of H. pylori infections, as well as H. pylori related local and systemic effects.

Evaluating the origin and virulence of a Helicobacter pylori cagA-positive strain isolated from a non-human primate

Helicobacter pylori cagA-positive strains are critically involved in the development of gastric cancer. Upon delivery into gastric epithelial cells via type IV secretion, the cagA-encoded CagA interacts with and thereby perturbs the pro-oncogenic phosphatase SHP2 and the polarity-regulating kinase PAR1b via the tyrosine-phosphorylated EPIYA-C/D segment and the CM sequence, respectively. Importantly, sequences spanning these binding regions exhibit variations among CagA proteins, which influence the pathobiological/oncogenic potential of individual CagA. Here we isolated an H. pylori strain (Hp_TH2099) naturally infecting the stomach of a housed macaque, indicating a zoonotic feature of H. pylori infection. Whole genome sequence analysis revealed that Hp_TH2099 belongs to the hpAsia2 cluster and possesses ABC-type Western CagA, which contains hitherto unreported variations in both EPIYA-C and CM sequences. The CM variations almost totally abolished PAR1b binding. Whereas pTyr + 5 variation in the EPIYA-C segment potentiated SHP2-binding affinity, pTyr-2 variation dampened CagA tyrosine phosphorylation and thus impeded CagA-SHP2 complex formation. As opposed to the H. pylori standard strain, infection of mouse ES cell-derived gastric organoids with Hp_TH2099 failed to elicit CagA-dependent epithelial destruction. Thus, the macaque-isolated H. pylori showed low virulence due to attenuated CagA activity through multiple substitutions in the sequences involved in binding with SHP2 and PAR1b.

CagY-Dependent Regulation of Type IV Secretion in Helicobacter pylori Is Associated with Alterations in Integrin Binding

Strains of Helicobacter pylori that cause ulcer or gastric cancer typically express a type IV secretion system (T4SS) encoded by the cag pathogenicity island (cagPAI). CagY is an ortholog of VirB10 that, unlike other VirB10 orthologs, has a large middle repeat region (MRR) with extensive repetitive sequence motifs, which undergo CD4⁺ T cell-dependent recombination during infection of mice. Recombination in the CagY MRR reduces T4SS function, diminishes the host inflammatory response, and enables the bacteria to colonize at a higher density. Since CagY is known to bind human α₅β₁ integrin, we tested the hypothesis that recombination in the CagY MRR regulates T4SS function by modulating binding to α₅β₁ integrin. Using a cell-free microfluidic assay, we found that H. pylori binding to α₅β₁ integrin under shear flow is dependent on the CagY MRR, but independent of the presence of the T4SS pili, which are only formed when H. pylori is in contact with host cells. Similarly, expression of CagY in the absence of other T4SS genes was necessary and sufficient for whole bacterial cell binding to α₅β₁ integrin. Bacteria with variant cagY alleles that reduced T4SS function showed comparable reduction in binding to α₅β₁ integrin, although CagY was still expressed on the bacterial surface. We speculate that cagY-dependent modulation of H. pylori T4SS function is mediated by alterations in binding to α₅β₁ integrin, which in turn regulates the host inflammatory response so as to maximize persistent infection.IMPORTANCE Infection with H. pylori can cause peptic ulcers and is the most important risk factor for gastric cancer, the third most common cause of cancer death worldwide. The major H. pylori virulence factor that determines whether infection causes disease or asymptomatic colonization is the type IV secretion system (T4SS), a sort of molecular syringe that injects bacterial products into gastric epithelial cells and alters host cell physiology. We previously showed that recombination in CagY, an essential T4SS component, modulates the function of the T4SS. Here we found that these recombination events produce parallel changes in specific binding to α₅β₁ integrin, a host cell receptor that is essential for T4SS-dependent translocation of bacterial effectors. We propose that CagY-dependent binding to α₅β₁ integrin acts like a molecular rheostat that alters T4SS function and modulates the host immune response to promote persistent infection.

When is Helicobacter pylori acquired in populations in developing countries? A birth-cohort study in Bangladeshi children

Helicobacter pylori colonization is prevalent throughout the world, and is predominantly acquired during childhood. In developing countries, >70% of adult populations are colonized with H. pylori and >50% of children become colonized before the age of 10 years. However, the exact timing of acquisition is unknown. We assessed detection of H. pylori acquisition among a birth cohort of 105 children in Mirzapur, Bangladesh. Blood samples collected at time 0 (cord blood), and at 6, 12, 18, and 24 months of life were examined for the presence of IgG and IgA antibodies to whole cell H. pylori antigen and for IgG antibodies to the CagA antigen using specific ELISAs and immunoblotting. Breast milk samples were analyzed for H. pylori-specific IgA antibodies. Cord blood was used to establish maternal colonization status. H. pylori seroprevalence in the mothers was 92.8%. At the end of the two-year follow-up period, 50 (47.6%) of the 105 children were positive for H. pylori in more than one assay. Among the colonized children, CagA prevalence was 78.0%. A total of 58 children seroconverted: 50 children showed persistent colonization and 8 (7.6%) children showed transient seroconversion, but immunoblot analysis suggested that the transient seroconversion observed by ELISA may represent falsely positive results. Acquisition of H. pylori was not influenced by the mother H. pylori status in serum or breastmilk. In this population with high H. pylori prevalence, we confirmed that H. pylori in developing countries is detectable mainly after the first year of life.

Characterization of the Cag pathogenicity island in Helicobacter pylori from naturally infected rhesus macaques

Helicobacter pylori commonly infects the epithelial layer of the human stomach and in some individuals causes peptic ulcers, gastric adenocarcinoma or gastric lymphoma. Helicobacter pylori is a genetically diverse species, and the most important bacterial virulence factor that increases the risk of developing disease, versus asymptomatic colonization, is the cytotoxin associated gene pathogenicity island (cagPAI). Socially housed rhesus macaques are often naturally infected with H. pylori similar to that which colonizes humans, but little is known about the cagPAI. Here we show that H. pylori strains isolated from naturally infected rhesus macaques have a cagPAI very similar to that found in human clinical isolates, and like human isolates, it encodes a functional type IV secretion system. These results provide further support for the relevance of rhesus macaques as a valid experimental model for H. pylori infection in humans.

[Infections and epigenetic changes in cancer]

The role of epigenetics and infectious diseases at early stages of life influence pre-malignant lesions of cancer, in particular, gastric cancer, one of the most frequent tumours in Chile, Latin America, and worldwide. This article examines the role of H.pylori and epigenetic alterations (i.e. DNA methylation) at early stages of gastric cancer and proposes, from the paediatric point of view, strategies for prevention and early detection.

Analysis of a single Helicobacter pylori strain over a 10-year period in a primate model

Helicobacter pylori from different individuals exhibits substantial genetic diversity. However, the kinetics of bacterial diversification after infection with a single strain is poorly understood. We investigated evolution of H. pylori following long-term infection in the primate stomach; Rhesus macaques were infected with H. pylori strain USU101 and then followed for 10 years. H. pylori was regularly cultured from biopsies, and single colony isolates were analyzed. At 1-year, DNA fingerprinting showed that all output isolates were identical to the input strain; however, at 5-years, different H. pylori fingerprints were observed. Microarray-based comparative genomic hybridization revealed that long term persistence of USU101 in the macaque stomach was associated with specific whole gene changes. Further detailed investigation showed that levels of the BabA protein were dramatically reduced within weeks of infection. The molecular mechanisms behind this reduction were shown to include phase variation and gene loss via intragenomic rearrangement, suggesting strong selective pressure against BabA expression in the macaque model. Notably, although there is apparently strong selective pressure against babA, babA is required for establishment of infection in this model as a strain in which babA was deleted was unable to colonize experimentally infected macaques.

Community-driven research on environmental sources of H. pylori infection in arctic Canada

The role of environmental reservoirs in H. pylori transmission remains uncertain due to technical difficulties in detecting living organisms in sources outside the stomach. Residents of some Canadian Arctic communities worry that contamination of the natural environment is responsible for the high prevalence of H. pylori infection in the region. This analysis aims to estimate associations between exposure to potential environmental sources of biological contamination and prevalence of H. pylori infection in Arctic Canada. Using data from 3 community-driven H. pylori projects in the Northwest and Yukon Territories, we estimated effects of environmental exposures on H. pylori prevalence, using odds ratios (OR) and 95% confidence intervals (CI) from multilevel logistic regression models to adjust for household and community effects. Investigated exposures include: untreated drinking water; livestock; dogs; cats; mice or mouse droppings in the home; cleaning fish or game. Our analysis did not identify environmental exposures associated clearly with increased H. pylori prevalence, except any exposure to mice or mouse droppings (OR = 4.6, CI = 1.2-18), reported by 11% of participants. Our multilevel models showed H. pylori clustering within households, but environmental exposures accounted for little of this clustering; instead, much of it was accounted for by household composition (especially: having infected household members; number of children). Like the scientific literature on this topic, our results do not clearly implicate or rule out environmental reservoirs of H. pylori; thus, the topic remains a priority for future research. Meanwhile, H. pylori prevention research should seek strategies for reducing direct transmission from person to person.

A mutation burst during the acute phase of Helicobacter pylori infection in humans and rhesus macaques

The evolution rate and genetic changes that occur during chronic infection with Helicobacter pylori have been analysed, but little is known about the genomic changes during the initial, acute bacterial infection phase. Here we analyse the rate and pattern of genome evolution in H. pylori from the genomes of two input strains isolated from human volunteers with asymptomatic infection, and the genomes of two output strains collected 20 and 44 days after re-infection. Similarly, we analyse genome evolution in bacteria from the genome sequences of input and output strains sequentially taken after experimental infection of a rhesus macaque. The estimated mutation rate reveals a mutation burst during the acute infection phase that is over 10 times faster than the mutation rate during chronic infection, and orders of magnitude faster than mutation rates in any other bacteria. The elevated frequency of mutations in outer membrane protein genes suggests that the mutation burst facilitates rapid host adaptation of the bacteria.

Evaluation of Gastric Lesions Based on Helicobacter pylori and Helicobacter-Like Organisms (HLOs) in Cats; A Histopathological and Bacteriological Study

Background:

The lesions induced by Helicobacter pylori in a candidate animal model should always be examined thoroughly. The resemblance of these lesions to those observed in humans can indicate whether the usage of this model will contribute to the understanding of the various pathogenic mechanisms involved in the development of human H. pylori-associated diseases.

Objectives:

The aim of this study was to perform a histopathological and bacteriological evaluation of gastric lesions based on H. pylori and Helicobacter-like organisms (HLOs) in cats.

Materials and Methods:

The present study was carried out on 28 cat’s (13 male and 15 female cases) gastric mucosae, which were tested by bacteriological and histopathological methods. Biochemical tests such as catalase, oxidase and urease were utilized in addition to Gram and Giemsa staining.

Results:

This research demonstrated that solely one case of H. pylori was isolated by gastric mucosal culture. Microscopically, the infected stomachs by HLOs comprised a mild to severe diffuse lymphoplasmacytic infiltration into the subglandular and gastric mucosa. Lymphoid follicles were also marked, particularly within pyloric tissues and mostly in displaced mucosal glands. For 75% of the gastritis cases, both HLOs and rapid urease tests were positive, whereas 83% of cases were more than one-year-old with gastritis. Furthermore, 75% of cats indicated gastritis, though 25% encompassed no gastritis; hence 20% had negative results for the rapid urease test and 25% for the Giemsa staining test. Such results may indicate that cats without gastritis were considered as free of HLOs pathogenic bacteria.

Conclusions:

These results suggest that most cases of gastritis were located in the antral region. Additionally, the isolation of H. pylori from domestic cats raises the possibility of zoonotic characteristics for the slightly pathogen; therefore transmission occurs from cats to human and vice versa.

Role of childhood infection in the sequelae of H. pylori disease

The persistence of Helicobacter pylori infection plays a fundamental role in the development of H. pylori-associated complications. Since the majority of infected persons acquire the bacteria during early childhood, an examination of the immunobiology of H. pylori infection in children compared with that of adults may help identify host factors that contribute to persistent infection. Therefore, we begin our review of the role of persistence in H. pylori disease with an assessment of the clinical features of H. pylori infection in children. We next review the bacterial factors that promote colonization and evasion of host defense mechanisms. We then focus our attention on the early host immunological factors that promote persistence of the infection and its complications in humans and mouse models. We also highlight topics in which further research is needed. An examination of how immunological factors cause divergent manifestations of H. pylori infection in children compared with adults may provide new insight for therapeutic modification or prevention of persistent H. pylori infection and its complications.

Identification of bacterial infection in neotropical primates

Emerging infectious diseases usually arise from wild animal populations. In the present work, we performed a screening for bacterial infection in natural populations of New World primates. The blood cell bulk DNAs from 181 individuals of four Platyrrhini genera were PCR screened for eubacterial 16S rRNA genes. Bacteria were detected and identified in 13 distinct individuals of Alouatta belzebul, Alouatta caraya, and Cebus apella monkeys from geographically distant regions in the states of Mato Grosso and Pará, Brazil. Sequence analyses showed that these Platyrrhini bacteria are closely related not only to human pathogens Pseudomonas spp. but also to Pseudomonas simiae and sheep-Acari infecting Pseudomonas spp. The identified Pseudomonas possibly represents a group of bacteria circulating in natural monkey populations.

Dynamics of Helicobacter pylori detection in stools during the first 5 years of life in Chile, a rapidly developing country

BACKGROUND

: Helicobacter pylori colonization/infection can be transitory or persistent, conditions that have not been thoroughly evaluated in young children. We aimed to characterize the dynamics of H. pylori stool detection and to determine host and environmental factors and symptoms associated with persistence.

METHOD

: In a 5-year cohort study, we followed-up infants from birth with clinic visits every 3 months. Symptoms and environmental risk factor survey and a stool sample for H. pylori antigen detection were requested in every visit. Secretor/ABH histo-blood group phenotype was determined in saliva.

RESULTS

: Overall, 218 of 1456 (15%) stool samples were positive for H. pylori and 39 of 96 (41%) children had at least 1 positive sample. Stool detection was transitory in 16 of 39 (41%), persistent in 19 (49%) and undetermined in 4 (10%) children. Persistence was acquired largely during the first 24 months (17/19 cases) and was associated with nonsecretor phenotype (32% versus 0% for transitory infection; P = 0.02) and daycare attendance (67% versus 26% for never infected; P = 0.019). Symptoms possibly associated with persistence were referred in only 1 child.

CONCLUSIONS

: Nearly 20% of this Chilean cohort had persistent H. pylori stool sample detections during the first 5 years of life, acquired mostly during the first 24 months. Persistence was significantly associated with nonsecretor phenotype and daycare attendance, and possibly associated gastrointestinal symptoms were rare. This relatively common group of young children with persistent H. pylori colonization/infection will require further study.

Serologic host response to Helicobacter pylori and Campylobacter jejuni in socially housed Rhesus macaques (Macaca mulatta)

Background

Helicobacter pylori are successful colonizers of the human gastric mucosa. Colonization increases the risk of peptic ulcer disease and adenocarcinoma. However, potential benefits of H. pylori colonization include protection against early-onset asthma and against gastrointestinal infections. Campylobacter jejuni are a leading cause of bacterial diarrhea and complications include Guillain-Barré syndrome. Here, we describe the development of reliable serological assays to detect antibodies against those two bacteria in Rhesus macaques and investigated their distribution within a social group of monkeys.

Methods

Two cohorts of monkeys were analyzed. The first cohort consisted of 30 monkeys and was used to establish an enzyme-linked immunosorbent assay (ELISA) for H. pylori antibodies detection. To evaluate colonization of those macaques, stomach biopsies were collected and analyzed for the presence of H. pylori by histology and culture. C. jejuni ELISAs were established using human serum with known C. jejuni antibody status. Next, plasma samples of the 89 macaques (Cohort 2) were assayed for antibodies and then statistically analyzed.

Results

An H. pylori IgG ELISA, which was 100% specific and 93% sensitive, was established. In contrast, the IgA ELISA was only 82% specific and 61% sensitive. The CagA IgG assay was 100% sensitive and 61% of the macaques were positive. In cohort 2, 62% macaques were H. pylori sero-positive and 52% were CagA positive. The prevalence of H. pylori IgG and CagA IgG increased with monkey age as described for humans. Of the 89 macaques 52% showed IgG against C. jejuni but in contrast to H. pylori, the sero-prevalence was not associated with increasing age. However, there was a drop in the IgG (but not in IgA) mean values between infant and juvenile macaques, similar to trends described in humans.

Conclusions

Rhesus macaques have widespread exposure to H. pylori and C. jejuni, reflecting their social conditions and implying that Rhesus macaques might provide a model to study effects of these two important human mucosal bacteria on a population.

Helicobacter pylori and type 1 diabetes mellitus: possibility of modifying chronic disease susceptibility with vaccinomics at the anvil

The human gastric pathogen, Helicobacter pylori, colonizes more than 50% of the world population and is a well-known cause of peptic ulcer disease. H. pylori has been epidemiologically linked to various other diseases, among which its putative link with certain complex diseases such as type 1 diabetes mellitus (T1DM) is of interest. Although antibiotic resistance is a significant clinical problem in H. pylori infection control, the exact cause and much of the underlying mechanisms of T1DM are not clearly understood. In addition, commensal microflora, gut-adapted microbial communities, and plausible roles of some of the chronic human pathogens add an important dimension to the control of T1DM. Given this, the present review attempts to analyze and examine the confounding association of H. pylori and T1DM and the approaches to tackle them, and how the emerging field of vaccinomics might help in this pursuit.

Longitudinal analysis of serological responses of adults to Helicobacter pylori antigens

Because Helicobacter pylori persist for decades in the human stomach, the aim of this study was to examine the long-term course of H. pylori-specific serum immunoglobulin G (IgG) responses with respect to subclass and antigenic target. We studied paired serum samples obtained in 1973 and in 1994 in Vammala, Finland, from 64 healthy H. pylori-positive adults and from other healthy control subjects. H. pylori serum immunoglobulin A, IgG, and IgG subclass responses were determined by antigen-specific enzyme-linked immunosorbent assays. H. pylori-specific IgG1 and IgG4 subtype responses from 47 subjects were similar in 1973 and 1994, but not when compared with unrelated persons. H. pylori-specific IgG1:IgG4 ratios among the participants varied >1000-fold; however, 57 (89.1%) of 64 subjects had an IgG1:IgG4 ratio >1.0, consistent with a predominant IgG1 (Th1) response. Furthermore, ratios in individual hosts were stable over the 21-year period (r = 0.56; P < .001). The immune response to heat shock protein HspA was unchanged in 49 (77%) of the 64 subjects tested; of the 15 whose serostatus changed, all seroconverted and were significantly younger than those whose status did not change. These findings indicate that H. pylori-specific antibody responses are host-specific with IgG1:IgG4 ratios stable over 21 years, IgG1 responses predominating, and HspA seroconversion with aging.

Diet synergistically affects helicobacter pylori-induced gastric carcinogenesis in nonhuman primates

BACKGROUND & AIMS

Gastric cancer results from a combination of Helicobacter pylori (H pylori) infection, exposure to dietary carcinogens, and predisposing genetic make-up. Because the role of these factors in gastric carcinogenesis cannot be determined readily in human beings, the present study examined the role of an oral carcinogen and H pylori infection in rhesus monkeys.

METHODS

Gastroscopies were performed in 23 monkeys assigned to 4 groups: controls; nitrosating carcinogen ethyl-nitro-nitrosoguanidine administration alone; inoculation of a virulent H pylori strain alone (H); and ethyl-nitro-nitrosoguanidine in combination with H pylori (EH). Follow-up gastroscopies and biopsies were performed at 3-month intervals for 5 years for pathologic and molecular studies.

RESULTS

Postinoculation, H and EH groups showed persistent infection and antral gastritis. Starting at 2 and 5 years, respectively, gastric intestinal metaplasia and intraepithelial neoplasia developed in 3 EH monkeys but in no other groups. Transcriptional analysis of biopsy specimens at 5 years revealed group-specific expression profiles, with striking changes in EH monkeys, plus a neoplasia-specific expression profile characterized by changes in multiple cancer-associated genes. Importantly, this neoplastic profile was evident in nonneoplastic mucosa, suggesting that the identified genes may represent markers preceding cancer.

CONCLUSIONS

Gastric intraglandular neoplasia is induced in primates when H pylori infection is associated with consumption of a carcinogen similar to the nitrosamines found in pickled vegetables, suggesting that H pylori and the carcinogen synergistically induce gastric neoplasia in primates.

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.

Helicobacter pylori in water sources: a global environmental health concern

Helicobacter pylori are Gram-negative micro-aerophilic motile curve rods that inhabit the gastric mucosa of the human stomach. The bacterium chronically infects billions of people worldwide and is one of the most genetically diverse of bacterial species. More than half of the world population in both developed and developing countries are infected with this organism. Infection usually occurs without overt clinical symptoms, particularly in poor communities. If untreated, the infection can last for decades without causing symptoms. In some communities, however, infection with the organism causes peptic and duodenal ulcers, gastritis, duodenitis, and gastric cancers. How H. pylori initially enters the stomach is not known, but contaminated food particles and water are suspected, with the former physically shielding it from stomach acid. Similarly, the route of transmission of this pathogen is unknown. Several reports have suggested the possibility of waterborne transmission as the organism can survive for a few days in fresh cold water, salt water, distilled water, and tap water. Knowledge of the epidemiology and mode of transmission of H. pylori is important to prevent its spread and may be useful in identifying high risk populations.

DNA-level diversity and relatedness of Helicobacter pylori strains in shantytown families in Peru and transmission in a developing-country setting

The efficiency of transmission of a pathogen within families compared with that between unrelated persons can affect both the strategies needed to control or eradicate infection and how the pathogen evolves. In industrialized countries, most cases of transmission of the gastric pathogen Helicobacter pylori seems to be from mother to child. An alternative model, potentially applicable among the very poor in developing countries, where infection is more common and the sanitary infrastructure is often deficient, invokes frequent transmission among unrelated persons, often via environmental sources. In the present study, we compared the genotypes of H. pylori from members of shantytown households in Peru to better understand the transmission of H. pylori in developing-country settings. H. pylori cultures and/or DNAs were obtained with informed consent by the string test (a minimally invasive alternative to endoscopy) from at least one child and one parent from each of 62 families. The random amplified polymorphic DNA fingerprints of 57 of 81 (70%) child-mother strain pairs did not match, nor did the diagnostic gene sequences (>1% DNA sequence difference), independent of the child's age (range, 1 to 39 years). Most strains from siblings or other paired family members were also unrelated. These results suggest that H. pylori infections are often community acquired in the society studied. Transmission between unrelated persons should facilitate the formation of novel recombinant genotypes by interstrain DNA transfer and selection for genotypes that are well suited for individual hosts. It also implies that the effective prevention of H. pylori infection and associated gastroduodenal disease will require anti-H. pylori measures to be applied communitywide.

A better method for confirming Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

Our aim was to evaluate the accuracy of the stool antigen test and the optimal time point for detecting Helicobacter pylori infection in a Mongolian gerbil model.

METHODS

We inoculated 8-week-old Mongolian gerbils with H. pylori (Vac A (+)/CagA(+)). The gerbil-infected model was developed as follows: H. pylori was put into broth (about 10(9) CFU/ml), and 50 gerbils were then fed with 1 ml intragastrically twice within a 3-day interval. Another ten gerbils were fed broth only. Twenty-six weeks after the inoculation, the gerbils were killed. The gastric mucosa was sampled for a series of examinations including culture, histology, rapid urease test, and polymerase chain reaction. Stool samples for a stool antigen test, H. pylori-specific stool antigen assay (HpSA), were collected during weeks 4, 6, 8, 12, and 26 after inoculation. Of the 50 gerbils inoculated with H. pylori, the inoculation was successful in 88%. Severe active gastritis, ulceration, and intestinal metaplasia were obvious.

RESULTS

The HpSA test results were sensitivity, 88.6%; specificity, 100%; positive predictive value (PPV), 100%; negative predictive value (NPV), 54.5%, and accuracy, 90%. The HpSA test began to be more sensitive and accurate (P < 0.05) beginning during week 6 after inoculation. We also found that H. pylori could be detected earlier and more easily in the group with high H. pylori density.

CONCLUSIONS

HpSA seems to be suitable for confirming colonization of gerbils with H. pylori. The optimal testing time point is around 6 weeks after inoculation. This test is a good choice for long-term observation of H. pylori infection in Mongolian gerbils.

Helicobacter pylori vaccine: from past to future

Helicobacter pylori infection is highly prevalent worldwide and is an important cause of gastritis, peptic ulcer disease, gastric mucosa-associated lymphoid tissue lymphoma (MALToma), and gastric adenocarcinoma. Infection is usually acquired during childhood and tends to persist unless treated. Because eradication requires treatment with multidrug regimens, prevention of initial infection by a suitable vaccine is attractive. Although immunization with H pylori protein subunits has been encouraging in animals, similar vaccine trials in humans have shown adjuvant-related adverse effects and only moderate effectiveness. Newer immunization approaches (use of DNA, live vectors, bacterial ghosts, and microspheres) are being developed. Several questions about when and whom to vaccinate will need to be appropriately answered, and a cost-effective vaccine production and delivery strategy will have to be useful for developing countries. For this review, we searched MEDLINE using the Medical Subject Heading (MeSH) terms Helicobacter pylori and vaccines for articles in English from 1990 to 2007.

Mucins in the mucosal barrier to infection

The mucosal tissues of the gastrointestinal, respiratory, reproductive, and urinary tracts, and the surface of the eye present an enormous surface area to the exterior environment. All of these tissues are covered with resident microbial flora, which vary considerably in composition and complexity. Mucosal tissues represent the site of infection or route of access for the majority of viruses, bacteria, yeast, protozoa, and multicellular parasites that cause human disease. Mucin glycoproteins are secreted in large quantities by mucosal epithelia, and cell surface mucins are a prominent feature of the apical glycocalyx of all mucosal epithelia. In this review, we highlight the central role played by mucins in accommodating the resident commensal flora and limiting infectious disease, interplay between underlying innate and adaptive immunity and mucins, and the strategies used by successful mucosal pathogens to subvert or avoid the mucin barrier, with a particular focus on bacteria.

Pathogenesis of Helicobacter pylori Infection

SUMMARY

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori .

Pathogenesis of Helicobacter pylori Infection

SUMMARY

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori .

Pathogenesis of Helicobacter pylori Infection

SUMMARY

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori .

Pathogenesis of Helicobacter pylori infection

Helicobacter pylori is the first formally recognized bacterial carcinogen and is one of the most successful human pathogens, as over half of the world's population is colonized with this gram-negative bacterium. Unless treated, colonization usually persists lifelong. H. pylori infection represents a key factor in the etiology of various gastrointestinal diseases, ranging from chronic active gastritis without clinical symptoms to peptic ulceration, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. Disease outcome is the result of the complex interplay between the host and the bacterium. Host immune gene polymorphisms and gastric acid secretion largely determine the bacterium's ability to colonize a specific gastric niche. Bacterial virulence factors such as the cytotoxin-associated gene pathogenicity island-encoded protein CagA and the vacuolating cytotoxin VacA aid in this colonization of the gastric mucosa and subsequently seem to modulate the host's immune system. This review focuses on the microbiological, clinical, immunological, and biochemical aspects of the pathogenesis of H. pylori.

Host Lewis phenotype-dependent Helicobacter pylori Lewis antigen expression in rhesus monkeys

Both human and H. pylori populations are polymorphic for the expression of Lewis antigens. Using an experimental H. pylori challenge of rhesus monkeys of differing Lewis phenotypes, we aimed to determine whether H. pylori populations adapt their Lewis phenotypes to those of their hosts. After inoculation of four monkeys with a mixture of seven strains identified by RAPD-polymerase chain reaction, H. pylori Lewis expression was followed in 86 isolates obtained over 40 wk. Host Lewis(a/b) secretion status was characterized by immunological assays. Fingerprints of the predominating strain (J166) were identical in all four animals after 40 wk, but its Lewis phenotype had substantial variability in individual hosts. At 40 wk, J166 populations from two Lewis(a-b+) animals predominantly expressed Lewis(y). In contrast, J166 populations had switched to a Lewis(x) dominant phenotype in the two Lewis(a+b-) animals; a frame shift in futC, regulating conversion of Lewis(x) to Lewis(y), accounted for the phenotypic switch. The results indicate that individual cells in H. pylori populations can change Lewis phenotypes during long-term colonization of natural hosts to resemble those of their hosts, providing evidence for host selection for bacterial phenotypes.

Preclinical Assessment of Gastrooesophageal Tolerance of the New Antiosteoporotic Drug Strontium Ranelate: An Endoscopic Study in Monkeys

This study was aimed at evaluating the digestive tolerance of the new antiosteoporotic drug, strontium ranelate, and to compare it to that of another strontium salt, strontium chloride (SrCl2). Strontium ranelate, SrCl2, or placebo were administered orally (capsules) to 3 groups of 2 male and 2 female cynomolgus monkeys (Macaca fascicularis) once a day for 7 days at a dose of 2 g/day, which is the recommended therapeutic dose in man. Endoscopic examination of the oesophagus, the stomach and the first part of the duodenum was performed on fasted animals approximately 3 hr after the first (Day 1) and last dosing (Day 7), and, on Day 8 and Day 14 in case of lesions on Day 7. Strontium ranelate did not induce any acute or subchronic toxic effect on the gastric mucosa, the oesophagus and the first part of the duodenum. On the contrary, acute and superficial damages were noted on all animals receiving SrCl2 such as haemorrhagic and erosive lesions (formation of an ulcer in one male and a marked congestive antritis in one female). These effects were reversible after cessation of treatment. The microscopic examination of biopsies sampled at the site of gastric lesions revealed moderate granulocyte infiltration, indicating a local irritating origin of the lesions. Strontium ranelate by oral route is safe for the gastric mucosa while SrCl2 induced superficial and reversible lesions.

Environment as a Critical Factor for the Pathogenesis and Outcome of Gastrointestinal Disease: Experimental and Human Inflammatory Bowel Disease and Helicobacter-Induced Gastritis

Environmental factors play an important role in the manifestation, course, and prognosis of diseases of the gastrointestinal tract such as inflammatory bowel disease (IBD) and Helicobacter pylori-induced gastritis. These two disease complexes were chosen for a discussion of the contribution of environmental factors to the disease outcome in humans and animal models. Dissecting complex diseases like IBD and Helicobacter-induced gastritis has shown that the outcome of disease depends on the allelic constellation of a host and the microbial and physical environments. Host alleles predisposing to a disease in one genomic and/or environmental milieu may not be deleterious in other constellations; on the other hand, microbes can have different effects in different hosts and under different environmental conditions. The impact of the complex interaction between host genetics and environmental factors, particularly microflora, also underlines the importance of a defined genetic background and defined environments in animal studies and is indicative of the difficulties in analyzing complex diseases in humans.

Of microbe and man: determinants ofHelicobacter pylori-related diseases

The human gastric pathogen Helicobacterpylori infects the human gastric mucus layer of approximately half of the world's population. Colonization with this bacterium results in superficial gastritis without clinical symptoms, but can progress into gastric or duodenal ulcers, gastric malignancies and mucosa-associated lymphoid tissue-lymphomas. Disease outcome is affected by a complex interplay between host, environmental and bacterial factors. Irrespective of disease outcome, the majority of H. pylori infected individuals remain colonized for life. Changing conditions in the human gastric mucosa may alter gene expression and/or result in the outgrowth of more fit H. pylori variants. As such, H. pylori is a highly flexible organism that is optimally adapted to its host. the heterogeneity in H. pylori populations make predictions on H. pylori-related pathogenesis difficult. In this review, we discuss host, environmental and bacterial factors that are important in disease progression. Moreover, H. pylori adaptive mechanisms, which allow its life-long survival and growth in the gastric mucosa are considered.

Comparison of Helicobacter pylori virulence gene expression in vitro and in the Rhesus macaque

We used a quantitative real-time reverse transcriptase PCR assay to measure the transcript abundance of 46 known and putative Helicobacter pylori virulence genes, including 24 genes on the Cag pathogenicity island. The expression profile of H. pylori cells grown in vitro was also compared to expression in vivo after experimental infection of rhesus macaques. Transcript abundance in vitro (mid-log phase) ranged from about 0.004 (feoB and hpaA) to 20 (ureAB, napA, and cag25) copies/cell. Expression of most genes was repressed during the transition from logarithmic- to stationary-phase growth, but several well-characterized H. pylori virulence genes (katA, napA, vacA, and cagA) were induced. Comparison of results in the rhesus macaque with similar data from humans showed a strong correlation (r = 0.89). The relative in vivo expression in the rhesus monkey was highly correlated with in vitro expression during mid-log (r = 0.89)- and stationary (r = 0.88)-phase growth. Transcript abundance was on average three- to fourfold reduced in vivo compared to in vitro during mid-log phase. However, when compared to stationary phase, increased expression in vivo was observed for 6 of 7 genes on a contiguous portion of the pathogenicity island, several of which are thought to encode the H. pylori type IV structural pilus and its accessory proteins. These results suggest the possibility that some genes encoding the H. pylori type IV structural pilus and accessory proteins may form an operon that is induced during growth in vivo.

B-cell and T-cell immune responses to experimental Helicobacter pylori infection in humans

The acute antibody and T-cell immune response to Helicobacter pylori infection in humans has not been studied systematically. Serum from H. pylori-naive volunteers challenged with H. pylori and cured after 4 or 12 weeks was tested by enzyme-linked immunosorbent assays for anti-H. pylori-specific immunoglobulin M (IgM) and IgA established using bacterial lysates from homologous (the infecting strain) and heterologous H. pylori. Proteins recognized by IgM antibody were identified by mass spectrometry of immunoreactive bands separated by two-dimensional gel electrophoresis. Mucosal T-cell subsets (CD4, CD8, CD3, and CD30 cells) were assessed by immunohistochemistry. All 18 infected volunteers developed H. pylori-specific IgM responses to both homologous or heterologous H. pylori antigens. H. pylori antigens reacted with IgM antibody at 4 weeks postinfection. IgM Western blotting showed immunoreactivity of postinfection serum samples to multiple H. pylori proteins with molecular weights ranging between 9,000 (9K) to 150K with homologous strains but only a 70K band using heterologous antigens. Two-dimensional electrophoresis demonstrated that production of H. pylori-specific IgM antibodies was elicited by H. pylori flagellins A and B, urease B, ABC transporter binding protein, heat shock protein 70 (DnaK), and alkyl hydroperoxide reductase. Mucosal CD3, CD4, and CD8 T-cell numbers increased following infection. IgM antibody responses were detected to a range of homologous H. pylori antigens 2 to 4 weeks postchallenge. The majority of H. pylori proteins were those involved in motility and colonization and may represent targets for vaccine development.

Chemokine networks and in vivo T-lymphocyte trafficking in nonhuman primates

T-lymphocyte migratory circuits in human and nonhuman primates remain largely unexplored due to the difficulty of defining cell trafficking in vivo. However, this knowledge may reveal critical aspects of immunity and T-lymphocyte homeostasis in both health and disease. Furthermore, in vivo T-lymphocyte trafficking studies may facilitate defining mechanism(s) of immune dysfunction in the nonhuman primate model for acquired immunodeficiency syndrome (AIDS). Here, we developed a model for in vivo T-lymphocyte trafficking in nonhuman primates, and delineated homing characteristics of unstimulated peripheral blood mononuclear cells (PBMCs) to lymphoid and nonlymphoid compartments in healthy rhesus macaques. T-lymphocyte homing of autologous, carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled PBMCs was defined within 48 h of intravenous transfer. The highest relative frequency of CFSE+ T lymphocytes was observed in peripheral blood and spleen. Expression of chemokine receptor CCR7 and its ligands correlated with recirculation of T lymphocytes through the periphery and homing to paracortical regions of lymph node, where cells remained largely excluded from B-cell follicles. T-lymphocyte trafficking was also detected to the liver and bone marrow, and at low levels to the thymus and small intestine. The liver contained the highest proportion of CD45RA- T lymphocytes, consistent with homing of activated/memory T lymphocytes to this nonlymphoid site. Our data suggest that lymphoid and nonlymphoid organs are under continuous immunosurveillance in healthy macaques, and that this model may serve to investigate aberrant patterns in disease.

Specific Immunoglobulin A Antibodies in Maternal Milk and Delayed Helicobacter pylori Colonization in Gambian Infants

BACKGROUND

Immunoglobulin A (IgA) in maternal milk may protect Gambian infants from early Helicobacter pylori colonization. This study sought evidence that this protection could be due to specific IgA antibodies.

METHODS

Sixty-five infants were screened from 12 weeks of age with [13C]-urea breath tests. Antibodies in maternal milk were measured to determine total IgA content and to detect specific IgA antibodies against crude whole-cell and recombinant H. pylori urease antigen preparations.

RESULTS

Ten children (15%) had no evidence of early H. pylori colonization, 10 (15%) had early H. pylori colonization, and 43 (66%) had mixed results. Levels of maternal circulating specific immunoglobulin G, total milk IgA, and IgA directed against crude whole-cell H. pylori antigen preparation were not significantly associated with the rate of infant H. pylori colonization. However, mothers of infants with no evidence of early colonization produced significantly higher levels of anti-recombinant urease IgA antibodies in milk than did control mothers, particularly at 8, 16, and 20 weeks postpartum (P<.01).

CONCLUSIONS

These observations support the hypothesis that antibodies in mother's milk directed against H. pylori urease can protect against colonization in human infancy.

Gastric transcription profile of Helicobacter pylori infection in the rhesus macaque

Infection with Helicobacter pylori is usually asymptomatic but sometimes progresses to peptic ulcer disease or gastric adenocarcinoma. The development of disease involves both host and bacterial factors. In order to better understand host factors in pathogenesis, we studied the gastric transcription profile of H. pylori infection in the rhesus macaque by using DNA microarrays. Significant changes were found in the expression of genes important for innate immunity, chemokines and cytokines, cell growth and differentiation, apoptosis, structural proteins, and signal transduction and transcription factors. This broad transcription profile demonstrated expected up-regulation of cell structural elements and the host inflammatory and immune response, as well as the novel finding of down-regulation of heat shock proteins. These results provide a unique view of acute H. pylori infection in a relevant animal model system and will direct future studies regarding the host response to H. pylori infection.

Rhesus monkey gastric mucins: oligomeric structure, glycoforms and Helicobacter pylori binding

Mucins isolated from the stomach of Rhesus monkey are oligomeric glycoproteins with a similar mass, density, glycoform profile and tissue localization as human MUC5AC and MUC6. Antibodies raised against the human mucins recognize those from monkey, which thus appear to be orthologous to those from human beings. Rhesus monkey muc5ac and muc6 are produced by the gastric-surface epithelium and glands respectively, and occur as three distinct glycoforms. The mucins are substituted with the histo blood-group antigens B, Le(a) (Lewis a), Le(b), Le(x), Le(y), H-type-2, the Tn-antigen, the T-antigen, the sialyl-Le(x) and sialyl-Le(a) structures, and the expression of these determinants varies between individuals. At neutral pH, Helicobacter pylori strains expressing BabA (blood-group antigen-binding adhesin) bind Rhesus monkey gastric mucins via the Le(b) or H-type-1 structures, apparently on muc5ac, as well as on a smaller putative mucin, and binding is inhibited by Le(b) or H-type-1 conjugates. A SabA (sialic acid-binding adhesin)-positive H. pylori mutant binds to sialyl-Le(x)-positive mucins to a smaller extent compared with the BabA-positive strains. At acidic pH, the microbe binds to mucins substituted by sialylated structures such as sialyl-Le(x) and sialylated type-2 core, and this binding is inhibited by DNA and dextran sulphate. Thus mucin- H. pylori binding occurs via at least three different mechanisms: (1) BabA-dependent binding to Le(b) and related structures, (2) SabA-dependent binding to sialyl-Le(x) and (3) binding through a charge-mediated mechanism to sialylated structures at low pH values.

Development of a noninvasive method for detecting and monitoring the time course of Helicobacter pylori infection

Helicobacter pylori infection status following experimental inoculation of mice presently requires euthanasia. The purpose of this study was to develop a method for following the time course of H. pylori infection in live experimental animals. Twenty-six C57BL/6, Helicobacter-free female mice were inoculated with H. pylori Sydney strain 1, and 16 mice were sham inoculated. The mice were repeatedly tested during a period of about 1 year with an H. pylori species-specific primer-based PCR analysis of DNA extracted from fecal pellets of mice. The mice were euthanized at 6 months (n = 15) and 10 months (n = 15) to determine their infection status by histology, culture, and PCR of gastric specimens. H. pylori-inoculated mice were tested via the PCR method at 6 and 10 months prior to necropsy. Nine of 13 (69%) and 10 of 13 (77%) mice tested at 6 and 10 months, respectively, were positive. All sham-inoculated mice were negative. These two PCR results suggested a specificity of 100% with a sensitivity range between 69 and 77%. In contrast, sensitivity and specificity rose to 90 and 100% if groups of mice were tested once daily for 4 days. Seventy-seven to 85% of the experimental mice were also positive for H. pylori by culture. The histopathology demonstrated mild to severe gastritis. These findings demonstrate that the persistence or transience of H. pylori infection in live mice can be repeatedly evaluated over time. This method could allow the determination of the time course of infection and the efficacy of medications and/or vaccine without necropsy.

Role of the Helicobacter pylori outer-membrane proteins AlpA and AlpB in colonization of the guinea pig stomach

The human gastric pathogen Helicobacter pylori expresses several putative outer-membrane proteins (OMPs), but the role of individual OMPs in colonization of the stomach by H. pylori is still poorly understood. The role of four such OMPs (AlpA, AlpB, OipA and HopZ) in a guinea pig model of H. pylori infection has been investigated. Single alpA, alpB, hopZ and oipA isogenic mutants were constructed in the guinea pig-adapted, wild-type H. pylori strain GP15. Guinea pigs were inoculated intragastrically with the wild-type strain, single mutants or a mixture of the wild-type and a single mutant in a 1: 1 ratio. Three weeks after infection, H. pylori could be isolated from stomach sections of all animals that were infected with the wild-type, the hopZ mutant or the oipA mutant, but from only five of nine (P = 0.18) and one of seven (P = 0.02) animals that were infected with the alpA or alpB mutants, respectively. The hopZ and oipA mutants colonized the majority of animals that were inoculated with the strain mixture, whereas alpA and alpB mutants could not be isolated from animals that were infected with the strain mixture (P < 0.01). Specific IgG antibody responses were observed in all animals that were infected with either the wild-type or a mutant, but IgG levels were lower in animals that were infected with either the alpA or the alpB mutants, compared to the wild-type strain (P < 0.05). In conclusion, absence of AlpA or AlpB is a serious disadvantage for colonization of the stomach by H. pylori.

Helicobacter pylori persistence: biology and disease

Helicobacter pylori are bacteria that have coevolved with humans to be transmitted from person to person and to persistently colonize the stomach. Their population structure is a model for the ecology of the indigenous microbiota. A well-choreographed equilibrium between bacterial effectors and host responses permits microbial persistence and health of the host but confers risk of serious diseases, including peptic ulceration and gastric neoplasia.