Diacylglycerol kinase synthesized by commensal Lactobacillus reuteri diminishes protein kinase C phosphorylation and histamine-mediated signaling in the mammalian intestinal epithelium.

Lactobacillus reuteri 6475 (Lr) of the human microbiome synthesizes histamine and can suppress inflammation via type 2 histamine receptor (H2R) activation in the mammalian intestine. Gut microbes such as Lr promote H2R signaling and may suppress H1R proinflammatory signaling pathways in parallel by unknown mechanisms. In this study, we identified a soluble bacterial enzyme known as diacylglycerol kinase (Dgk) from Lr that is secreted into the extracellular milieu and presumably into the intestinal lumen. DgK diminishes diacylglycerol (DAG) quantities in mammalian cells by promoting its metabolic conversion and causing reduced protein kinase C phosphorylation (pPKC) as a net effect in mammalian cells. We demonstrated that histamine synthesized by gut microbes (Lr) activates both mammalian H1R and H2R, but Lr-derived Dgk suppresses the H1R signaling pathway. Phospho-PKC and IκBα were diminished within the intestinal epithelium of mice and humans treated by wild-type (WT) Lr, but pPKC and IκBα were not decreased in treatment with ΔdgkA Lr. Mucosal IL-6 and systemic interleukin (IL)-1α, eotaxin, and granulocyte colony-stimulating factor (G-CSF) were suppressed in WT Lr, but not in ΔdgkA Lr colonized mice. Collectively, the commensal microbe Lr may act as a "microbial antihistamine" by suppressing intestinal H1R-mediated proinflammatory responses via diminished pPKC-mediated mammalian cell signaling.

Helicobacter saguini, a Novel Helicobacter Isolated from Cotton-Top Tamarins with Ulcerative Colitis, Has Proinflammatory Properties and Induces Typhlocolitis and Dysplasia in Gnotobiotic IL-10-/- Mice.

A urease-negative, fusiform, novel bacterium named Helicobacter saguini was isolated from the intestines and feces of cotton-top tamarins (CTTs) with chronic colitis. Helicobacter sp. was detected in 69% of feces or intestinal samples from 116 CTTs. The draft genome sequence, obtained by Illumina MiSeq sequencing, for H. saguini isolate MIT 97-6194-5, consisting of ∼2.9 Mb with a G+C content of 35% and 2,704 genes, was annotated using the NCBI Prokaryotic Genomes Automatic Annotation Pipeline. H. saguini contains homologous genes of known virulence factors found in other enterohepatic helicobacter species (EHS) and H. pylori These include flagellin, γ-glutamyl transpeptidase (ggt), collagenase, the secreted serine protease htrA, and components of a type VI secretion system, but the genome does not harbor genes for cytolethal distending toxin (cdt). H. saguini MIT 97-6194-5 induced significant levels of interleukin-8 (IL-8) in HT-29 cell culture supernatants by 4 h, which increased through 24 h. mRNAs for the proinflammatory cytokines IL-1ß, tumor necrosis factor alpha (TNF-α), IL-10, and IL-6 and the chemokine CXCL1 were upregulated in cocultured HT-29 cells at 4 h compared to levels in control cells. At 3 months postinfection, all H. saguini-monoassociated gnotobiotic C57BL/129 IL-10(-/-) mice were colonized and had seroconverted to H. saguini antigen with a significant Th1-associated increase in IgG2c (P < 0.0001). H. saguini induced a significant typhlocolitis, associated epithelial defects, mucosa-associated lymphoid tissue (MALT) hyperplasia, and dysplasia. Inflammatory cytokines IL-22, IL-17a, IL-1ß, gamma interferon (IFN-γ), and TNF-α, as well as inducible nitric oxide synthase (iNOS) were significantly upregulated in the cecal tissues of infected mice. The expression of the DNA damage response molecule γ-H2AX was significantly higher in the ceca of H. saguini-infected gnotobiotic mice than in the controls. This model using a nonhuman primate Helicobacter sp. can be used to study the pathogenic potential of EHS isolated from primates with naturally occurring inflammatory bowel disease (IBD) and colon cancer.

Helicobacter hepaticus infection in mice: models for understanding lower bowel inflammation and cancer.

Pioneering work in the 1990s first linked a novel microaerobic bacterium, Helicobacter hepaticus, with chronic active hepatitis and inflammatory bowel disease in several murine models. Targeted H. hepaticus infection experiments subsequently demonstrated its ability to induce colitis, colorectal cancer, and extraintestinal diseases in a number of mouse strains with defects in immune function and/or regulation. H. hepaticus is now widely utilized as a model system to dissect how intestinal microbiota interact with the host to produce both inflammatory and tolerogenic responses. This model has been used to make important advances in understanding factors that regulate both acquired and innate immune response within the intestine. Further, it has been an effective tool to help define the function of regulatory T cells, including their ability to directly inhibit the innate inflammatory response to gut microbiota. The complete genomic sequence of H. hepaticus has advanced the identification of several virulence factors and aided in the elucidation of H. hepaticus pathogenesis. Delineating targets of H. hepaticus virulence factors could facilitate novel approaches to treating microbially induced lower bowel inflammatory diseases.

Cytolethal distending toxin promotes Helicobacter cinaedi-associated typhlocolitis in interleukin-10-deficient mice.

Helicobacter cinaedi colonizes a wide host range, including rodents, and may be an emerging zoonotic agent. Colonization parameters, pathology, serology, and inflammatory responses to wild-type H. cinaedi (WT(Hc)) were evaluated in B6.129P2-IL-10(tm1Cgn) (IL-10(-/-)) mice for 36 weeks postinfection (WPI) and in C57BL/6 (B6) mice for 12 WPI. Because cytolethal distending toxin (CDT) may be a virulence factor, IL-10(-/-) mice were also infected with the cdtB(Hc) and cdtB-N(Hc) isogenic mutants and evaluated for 12 WPI. Consistent with other murine enterohepatic helicobacters, WT(Hc) did not cause typhlocolitis in B6 mice, but mild to severe lesions developed at the cecocolic junction in IL-10(-/-) mice, despite similar colonization levels of WT(Hc) in the cecum and colon of both B6 and IL-10(-/-) mice. WT(Hc) and cdtB mutants also colonized IL-10(-/-) mice to a similar extent, but infection with either cdtB mutant resulted in attenuated typhlocolitis and hyperplasia compared to infection with WT(Hc) (P < 0.03), and only WT(Hc) infection caused dysplasia and intramucosal carcinoma. WT(Hc) and cdtB(Hc) mutant infection of IL-10(-/-) mice elevated mRNA expression of tumor necrosis factor alpha, inducible nitric oxide synthase, and gamma interferon in the cecum, as well as elevated Th1-associated serum immunoglobulin G2a(b) compared to infection of B6 mice (P < 0.05). Although no hepatitis was noted, liver samples were PCR positive at various time points for WT(Hc) or the cdtB(Hc) mutant in approximately 33% of IL-10(-/-) mice and in 10 to 20% of WT(Hc)-infected B6 mice. These results indicate that WT(Hc) can be used to model inflammatory bowel disease in IL-10(-/-) mice and that CDT contributes to the virulence of H. cinaedi.

Rapid onset of ulcerative typhlocolitis in B6.129P2-IL10tm1Cgn (IL-10-/-) mice infected with Helicobacter trogontum is associated with decreased colonization by altered Schaedler's flora.

Infection with Helicobacter trogontum, a urease-positive helicobacter isolated from subclinically infected rats, was evaluated in B6.129P2-IL10(tm1Cgn) (interleukin-10(-/-) [IL-10(-/-)]) and C57BL/6 (B6) mice. In a first experiment, IL-10(-/-) mice naturally infected with Helicobacter rodentium had subclinical typhlocolitis but developed severe diarrhea and loss of body condition with erosive to ulcerative typhlocolitis within 1 to 3 weeks of experimental infection with H. trogontum. A second experiment demonstrated that helicobacter-free IL-10(-/-) mice dosed with H. trogontum also developed severe clinical signs and typhlocolitis within 2 to 4 weeks, whereas B6 mice colonized with H. trogontum were resistant to disease. In a third experiment, using helicobacter-free IL-10(-/-) mice, dosing with H. trogontum resulted in acute morbidity and typhlocolitis within 8 days. Acute typhlocolitis was accompanied by signs of sepsis supported by degenerative hemograms and recovery of Escherichia coli and Proteus spp. from the livers of infected mice. Quantitative PCR data revealed that H. rodentium and H. trogontum may compete for colonization of the lower bowel, as H. trogontum established higher colonization levels in the absence of H. rodentium (P < 0.003). H. trogontum-induced typhlocolitis was also associated with a significant decrease in the levels of colonization by five of eight anaerobes that comprise altered Schaedler's flora (P < 0.002). These results demonstrate for the first time that H. rodentium infection in IL-10(-/-) mice causes subclinical typhlocolitis and that infection with H. trogontum (with or without H. rodentium) induces a rapid-onset, erosive to ulcerative typhlocolitis which impacts the normal anaerobic flora of the colon and increases the risk of sepsis.

Clostridium piliforme infection in two farm-raised white-tailed deer fawns (Odocoileus virginianus) and association with copper toxicosis.

Necropsy of 2 white-tailed deer fawns who died acutely revealed diarrhea and melena in case No. 1 and no gross changes in case No. 2. Histologically, the livers of both deer displayed multifocal coagulative necrosis, with infiltrations of neutrophils, macrophages, and lymphocytes. By Warthin-Starry staining, bundles of filamentous bacteria were identified within hepatocytes at the periphery of the necrotic foci in case No. 1. There was multifocal myocardiocyte necrosis in case No. 1 and multifocal lymphoid necrosis of the Peyer's patches in case No. 2. Clostridium piliforme 16S ribosomal ribonucleic acid gene was detected in both livers by polymerase chain reaction (PCR) with C. piliforme-specific primers. The liver copper levels in both cases were normal to slightly elevated. The kidney copper level in case No. 2 was elevated. This represents the first published cases of Tyzzer's disease in deer, a novel use of PCR for the diagnosis of C. piliforme infection, and a possible association between copper toxicosis and Tyzzer's disease.

Cholangiohepatitis and inflammatory bowel disease induced by a novel urease-negative Helicobacter species in A/J and Tac:ICR:HascidfRF mice.

Helicobacter bilis and H. hepaticus, both urease-positive intestinal helicobacters of mice, have been shown experimentally to induce proliferative typhlocolitis in scid mice. We recently isolated a urease-negative Helicobacter sp. (H. sp.) that also induced proliferative typhlocolitis in pilot studies in scid mice. To determine the pathogenic potential of H. sp. in immunocompromised and immunocompetent mice, 5-week old male A/J or Tac:Icr:Ha(ICR)-scidfRF mice were inoculated by intraperitoneal (IP) injection with approximately 3 x 10(7) colony-forming units (CFU) of H. sp. Mice were necropsied at various time points postinoculation (PI). Sham-inoculated mice had no clinical, gross, or histopathological lesions. In contrast, scid mice inoculated IP with H. sp. had severe hemorrhagic diarrhea and decreased weight gain at 2, 7, and 18 weeks postinoculation (PI), with severe proliferative typhlocolitis, phlebothrombosis, and hepatitis. A/J mice had no clinical signs, but had mild to moderate proliferative typhlocolitis and moderate to marked cholangiohepatitis at 7 and 24 weeks PI. A/J mice infected with H. sp. developed robust immune responses of a predominant Th1 type. This report demonstrates that infection with a urease-negative helicobacter can cause inflammatory bowel disease (IBD) and hepatitis in scid and immunocompetent A/J mice. These results provide a new model of IBD and cholangio-hepatitis associated with a specific urease-negative, novel H. species.

Fluorogenic PCR-based quantitative detection of a murine pathogen, Helicobacter hepaticus.

Helicobacter hepaticus infection in mice is being used as an animal model for elucidating the pathogenesis of gastrointestinal and biliary diseases in humans. H. hepaticus, which forms a spreading film on selective agar, is not amenable to routine quantitative counts of organisms in tissues using a CFU method. In this study, a fluorogenic PCR-based assay was developed to quantitatively detect H. hepaticus in mouse ceca and feces using the ABI Prism 7700 sequence detection system. A pair of primers and a probe for this assay were generated from the H. hepaticus cdtB gene (encoding subunit B of the H. hepaticus cytolethal distending toxin). Using this assay, the sensitivity for detection of H. hepaticus chromosomal DNA prepared from pure culture was 20 fg, which is equivalent to approximately 14 copies of the H. hepaticus genome based on an estimated genome size of approximately 1.3 Mb determined by pulsed-field gel electrophoresis. H. hepaticus present in feces and cecal samples from H. hepaticus-infected mice was readily quantified. The selected PCR primers and probe did not generate fluorescent signals from eight other helicobacters (H. canis, H. cineadi, H. felis, H. mustelae, H. nemestrinae, H. pullorum, H. pylori, and H. rodentium). A fluorescent signal was detected from 20 ng of H. bilis DNA but with much lower sensitivity (10(6)-fold) than from H. hepaticus DNA. Therefore, this assay can be used with high sensitivity and specificity to quantify H. hepaticus in experimentally infected mouse models as well as in naturally infected mice.

Long-term colonization levels of Helicobacter hepaticus in the cecum of hepatitis-prone A/JCr mice are significantly lower than those in hepatitis-resistant C57BL/6 mice.

Helicobacter hepaticus infection causes hepatitis in A/JCr mice but mild or no disease in C57BL/6 mice. Colonization of H. hepaticus in the cecum of experimentally infected A/JCr and C57BL/6 mice was quantified by use of real-time polymerase chain reaction (PCR) analysis with primers for the H. hepaticus cdtB gene and mouse 18srRNA. Eight-week-old mice were experimentally (n = 48) or sham (n = 24) infected with H. hepaticus, then were necropsied 6 months after infection. Liver specimens from experimentally infected mice had negative results of PCR analysis for H. hepaticus; thus, real-time quantification was not attempted. Quantitative PCR analysis of H. hepaticus in cecal specimens indicated that C57BL/6 mice were colonized to a greater extent than were A/JCr mice (P < 0.006). Appreciable typhlitis was not observed, but was consistent with that of previous reports; A/JCr mice developed more severe parenchymal necrosis, portal inflammation, and phlebitis in the liver (P < 0.0001), with mild disease observed in infected C57BL/6 mice. Thus, hepatitis in A/JCr mice caused by H. hepaticus infection is associated with significantly lower colonization levels of H. hepaticus in the cecum, compared with those of hepatitis-resistant C57BL/6 mice. Host responses of A/JCr mice that limit cecal colonization with H. hepaticus may have important roles in the pathogenesis of hepatic lesions.

Monitoring sentinel mice for Helicobacter hepaticus, H rodentium, and H bilis infection by use of polymerase chain reaction analysis and serologic testing.

BACKGROUND AND PURPOSE: Natural infection of research mice with enterohepatic Helicobacter spp. is common and may confound experimental studies from intercurrent disease. We evaluated a protocol of dirty bedding exposure for transmission of Helicobacter infection from colony mice to female Tac:(SW)fBR sentinel mice over 6 months. METHODS: Cecal scrapings from culled colony mice and associated sentinel mice were tested for H. hepaticus, H. rodentium, and H. bilis using polymerase chain reaction analysis (PCR). These results were correlated with the results of sentinel serum IgG responses measured by ELISA. RESULTS: In 9 colony rooms, 43 of 45 mice were infected with H. hepaticus; in 14 rooms, 58 of 70 mice were infected with H. rodentium; and in 2 rooms, 2 of 10 mice were infected with H. bilis. Concurrence of Helicobacter infection between colony and sentinel mice was 82% for H. hepaticus, 88% for H. rodentium, and 94% for H. bilis. Concurrence of Helicobacter infection status of sentinel cagemates was 98% for H. hepaticus, 86% for H. rodentium, and 95% for H. bilis. Fecal samples pooled by sentinel cage had positive PCR results for H. hepaticus and H. rodentium at 1 month in 60 and 44%, respectively, of the cages that contained test-positive mice at necropsy (6 months). By 3 months, detection rates were 100 and 81% for H. hepaticus and H. rodentium, respectively, and H. bilis was not detected until 4 months. Newly acquired infections with H. rodentium and H. bilis were evident throughout the 6-month study period. Seroconversion was coincident with positive PCR results in sentinel mice, and serum IgG values continued to increase until necropsy. The serum IgG ELISA was 98 to 100% sensitive, but was low in specificity (34 to 44%), most likely attributable to common coinfection with H. hepaticus and H. rodentium. CONCLUSION: Sentinel mice acquire infection with Helicobacter spp. through dirty bedding exposure. Combined use of PCR analysis and serologic testing of sentinel mice was predictive of Helicobacter infection status of mouse colonies used for biomedical research.

Concurrent enteric helminth infection modulates inflammation and gastric immune responses and reduces helicobacter-induced gastric atrophy.

Helicobacter pylori is causally associated with gastritis and gastric cancer. Some developing countries with a high prevalence of infection have high gastric cancer rates, whereas in others, these rates are low. The progression of helicobacter-induced gastritis and gastric atrophy mediated by type 1 T-helper cells may be modulated by concurrent parasitic infection. Here, in mice with concurrent helminth infection, helicobacter-associated gastric atrophy was reduced considerably despite chronic inflammation and high helicobacter colonization. This correlated with a substantial reduction in mRNA for cytokines and chemokines associated with a gastric inflammatory response of type 1 T-helper cells. Thus, concurrent enteric helminth infection can attenuate gastric atrophy, a premalignant lesion.

Colonization and tissue tropism of Helicobacter pylori and a novel urease-negative Helicobacter species in ICR mice are independent of route of exposure.

BACKGROUND: In humans, Helicobacter pylori is known to colonize the stomach and to induce persistent gastritis; selected reports also suggest it causes extragastric disease, including hepatitis. H. pylori and a novel urease-negative Helicobacter sp. induce gastritis and typhlocolitis, respectively, when inoculated orally into mice. Experimental typhlocolitis and hepatitis have been caused by intraperitoneal (i.p.) injection of H. hepaticus, H. bilis, and the novel Helicobacter spp. However, the route by which i.p.-inoculated organisms localize to specific areas of the gastrointestinal system is unknown. MATERIALS AND METHODS: To determine whether Helicobacter spp. can be isolated from blood, can preferentially colonize specific tissues, and can cause pathological changes, we inoculated 6-week-old outbred mice orally or intraperitoneally with H. pylori or a novel Helicobacter sp. RESULTS: When these mice were inoculated by the i.p. route, H. pylori was cultured from lungs, spleen, liver, cecum, and stomach on day 1 after inoculation, from liver and stomach mucosa on day 3 after inoculation, and from the stomach on day 30 after inoculation, suggesting preferential colonization of the stomach. After inoculation by the i.p. route, the novel intestinal Helicobacter sp. was cultured from the blood, lungs, spleen, liver, kidneys, cecum, and feces but not from stomach mucosa on day 1 after inoculation. By day 30 after inoculation, the novel Helicobacter sp. was cultured from cecum and feces only, suggesting that it had preferentially colonized the lower bowel. By the i.p. route, the novel Helicobacter sp. induced hepatitis that persisted for 30 days after inoculation. Though mice inoculated intraperitoneally with H. pylori developed an acute hepatitis, the liver lesion began to resolve 30 days after inoculation. Mice inoculated orally with either H. pylori or the novel Helicobacter sp. did not have hepatitis on day 30 after inoculation but developed 100% colonization of stomach and cecum, respectively. CONCLUSION: The isolation of H. pylori and the novel Helicobacter sp. from multiple tissues infers that a transient helicobacter bacteremia occurs when Helicobacter spp. are injected intraperitoneally, but organisms are cleared rapidly from nontarget tissues and preferentially colonize specific regions of the gastrointestinal tract.

SCID/NCr mice naturally infected with Helicobacter hepaticus develop progressive hepatitis, proliferative typhlitis, and colitis.

Hepatitis, proliferative typhlitis, and colitis were characterized in young adult and older SCID/NCr mice naturally infected with Helicobacter hepaticus. Liver lesions consisted of Kupffer, Ito, and oval cell hyperplasia along with multifocal to coalescing coagulative hepatocyte necrosis. Numerous Warthin-Starry-positive bacteria were observed in the parenchyma, and there were minimal to mild accumulations of monocytic cells and neutrophils. Proliferative typhlitis was characterized by moderate to marked mucosal epithelial cell hyperplasia with mild monocytic and neutrophilic infiltration. Minimal to mild colitis with mucosal epithelial cell hyperplasia of the colon was most marked in older mice. Comparable gastrointestinal lesions were not observed in uninfected control SCID/NCr mice. H. hepaticus was cultured from fetal viscera of 2 of 11 pups sampled late in gestation from infected SCID/NCr females, suggesting transplacental infection of H. hepaticus. As expected, most of the naturally infected SCID/NCr mice had no serum immunoglobulin G response against H. hepaticus. These findings contrast with those in infected immunocompetent A/JCr mice, which develop a significant immune response to H. hepaticus associated with prominent multifocal mononuclear cell infiltrates in the liver, with only rare bacteria observable at the periphery of inflammatory foci or in the biliary canaliculi. The results demonstrate that chronic inflammatory and proliferative lesions simultaneously affecting the liver, cecum, and colon are associated with natural infection of SCID/NCr mice with H. hepaticus and that lesions are progressive with age. Concurrent infection with H. hepaticus may confound studies that have been attributed to similar lesions due to other experimental manipulations of SCID/NCr mice.

Chronic active hepatitis induced by Helicobacter hepaticus in the A/JCr mouse is associated with a Th1 cell-mediated immune response.

Helicobacter hepaticus infection in A/JCr mice results in chronic active hepatitis characterized by perivascular, periportal, and parenchymal infiltrates of mononuclear and polymorphonuclear cells. This study examined the development of hepatitis and the immune response of A/JCr mice to H. hepaticus infection. The humoral and cell-mediated T helper immune response was profiled by measuring the postinfection (p.i.) antibody response in serum, feces, and bile and by the production of cytokines and proliferative responses by splenic mononuclear cells to H. hepaticus antigens. Secretory immunoglobulin A (IgA) and systemic IgG2a antibody developed by 4 weeks p.i. and persisted through 12 months. Splenocytes from infected mice proliferated and produced more gamma interferon (IFN-gamma) than interleukin-4 (IL-4) or IL-5 when cultured with H. hepaticus outer membrane proteins. The predominantly IgG2a antibody response in serum and the in vitro production of IFN-gamma in excess of IL-4 or IL-5 are consistent with a Th1 immune response reported in humans and mice infected with Helicobacter pylori and Helicobacter felis, respectively. Mice infected with H. hepaticus developed progressively severe perivascular, periportal, and hepatic parenchymal lesions consisting of lymphohistiocytic and plasmacytic cellular infiltrates. In addition, transmural typhlitis was observed at 12 months p.i. The characterization of a cell-mediated Th1 immune response to H. hepaticus infection in the A/JCr mouse should prove valuable as a model for experimental regimens which manipulate the host response to Helicobacter.

Experimental Helicobacter pylori infection induces antral gastritis and gastric mucosa-associated lymphoid tissue in guinea pigs.

Humans infected with Helicobacter pylori have abnormally low levels of the antioxidant vitamin C, which protects against the formation of carcinogenic nitrosamines, in gastric juice. Guinea pigs, like humans and nonhuman primates, have a dietary requirement for vitamin C. As such, these species have gastrointestinal vitamin C transport systems not found in other animals. We have developed and characterized a guinea pig model of chronic gastric H. pylori infection with the rodent-adapted Sydney strain of H. pylori. At 4 weeks postinfection, five of six animals of the infected group and zero of two animals of the control group were positive for H. pylori as determined by culture or PCR. At 15 weeks, six of six animals of the infected group and zero of two animals of the control group were positive. H. pylori-specific seroconversion was observed among infected animals. There were no histologic abnormalities in the gastric antra or fundi of control guinea pigs. In contrast, there was multifocal, mild to moderate lymphohistiocytic antral gastritis and formation of antral lymphoid follicles in H. pylori-infected animals. The lesion distribution in the gastric antra paralleled that observed in H. pylori-infected humans. The H. pylori-infected guinea pig should prove useful in modeling the interaction of helicobacter and vitamin C in gastric carcinogenesis.

Reduction in animal numbers required for antisera production using the subcutaneous chamber technique in rabbits.

The purpose of this study was to determine if the subcutaneous chamber technique would reduce the number of rabbits required for antisera production by enabling serial use of individual animals for multiple antigens. Rabbits were assigned to immunization protocols against two antigens in series that involved combinations of chamber implantation, Freund's adjuvant and injection of antigen either by the subcutaneous route or by direct inoculation into the chamber. Results indicate the systemic immune response to both antigens achieved similar magnitude and duration by use of either Freund's adjuvant or direct inoculation of antigen into the chamber, suggesting that chamber use may be able to replace use of Complete Freund's adjuvant for many antigens. Rabbits re-used for a second antigen were equally successful in production of significant titres in both serum and chamber fluid without evidence of either a significant inflammatory response due to the chronic presence of the implant or a decrease in the yield of antisera harvested from the chamber. These results support the advantages of chamber use as reported by others and demonstrate that the chamber technique can significantly extend the productive life of an individual animal that would otherwise be euthanized following a single use in antisera production.

Mice carrying a truncated Apc gene have diminished gastric epithelial proliferation, gastric inflammation, and humoral immunity in response to Helicobacter felis infection.

Helicobacter pylori infection and adenomatous polyposis coli (Apc) gene mutations have been linked to gastric cancer in humans, but possible synergistic interaction(s) between these risk factors have not been examined. Fourteen C57BL/6 wild-type and 14 Apc1638 heterozygous mice were inoculated with Helicobacter felis at 6 weeks of age and compared at various time points with a similar number of uninfected control mice of the same genotype. Both infected and uninfected Apc1638 mice had a limited incidence of atypical proliferation foci in the mucosa of the antrum and pyloric junction at 4.5 and 6 months of age, whereas polyps of the antrum and pylorus were present in all mice, regardless of infection status, at 7.5 months. In contrast, no altered gastric mucosal foci were observed in control or infected C57BL/6 mice at any time point. Interestingly, the infected Apc1638 mice had less epithelial proliferation and inflammation in the body of the stomach, lower anti-H. felis serum IgG antibody responses (although both the wild-type and Apc mutant mice had a Th1-like immune response, based on a predominantly IgG2a immunoglobulin response), and higher bacteria and urease scores than did infected wild-type C57BL/6 mice. In conclusion, the Apc1638 truncating mutation leads to gastric dysplasia and polyposis of the antrum and pyloric junction, but H. felis infection of the Apc mutant mouse does not lead to an increased rate of gastric neoplasia. In addition, our data suggest this Apc mutation may actually lead to decreased immune, inflammatory, and gastric hyperplastic responses to Helicobacter infection, suggesting the possibility of a novel role for this tumor suppressor gene in the immune and local tissue responses to gastric bacterial infection.

Promotion of ulcerative duodenitis in young ferrets by oral immunization with Helicobacter mustelae and muramyl dipeptide.

BACKGROUND: The purpose of this study was to determine whether oral immunization of ferret kits with a whole-cell sonicate of Helicobacter mustelae lysate (Hml) and the adjuvant muramyl dipeptide (MDP) would reduce the incidence of natural colonization with H. mustelae and the extent of Helicobacter-associated gastritis by enhancing the host mucosal immune response. MATERIALS AND METHODS: Between the ages of 4 and 11 weeks, 44 ferret kits were gavaged with Hml and various doses of MDP. The extent of gastritis and duodenitis and the immune response to H. mustelae were evaluated. RESULTS: All kits became colonized naturally with H. mustelae and the majority developed mild to severe gastritis and duodenitis. Kits that received Hml with MDP developed significantly greater inflammation of the gastric antrum and duodenum, as compared to kits vaccinated with Hml alone. Vaccination with Hml and 50 micrograms of MDP was associated with severe lesions in the proximal duodenum characterized by accumulation of mononuclear inflammatory cells, mucosal erosion, and ulceration. Although serum antibody specific for H. mustelae in 4-week-old kits was approximately 50% of adult levels, a finding attributable to passively acquired maternal antibody, both systemic and mucosal antibody levels became depressed over time despite oral vaccination. The humoral immune response was sufficiently low to prevent detection of any significant dose effect of MDP on antibody levels among experimental groups. CONCLUSIONS: Oral vaccination of young ferrets with Hml and 50 micrograms MDP increased the risk of Helicobacter-associated mucosal ulceration in the proximal duodenum, which was associated with low humoral (but significant cell-mediated) immune responses to H. mustelae. In retrospect, the frequency of vaccination may have suppressed the systemic humoral immune response, thereby promoting mucosal damage by H. mustelae. The 50-microgram dose of MDP enhanced the cell-mediated immune response, which indirectly contributed to development of severe lesions. The increased frequency of mucosal damage associated with this vaccination regimen enhances the value of the ferret model for studying duodenal ulceration secondary to Helicobacter infection.