Genetic background of IL-10(-/-) mice alters host-pathogen interactions with Campylobacter jejuni and influences disease phenotype

Innate Lymphoid Cells in Response to Intracellular Pathogens: Protection Versus Immunopathology

Innate lymphoid cells (ILCs) are a heterogeneous group of cytokine-producing lymphocytes which are predominantly located at mucosal barrier surfaces, such as skin, lungs, and gastrointestinal tract. ILCs contribute to tissue homeostasis, regulate microbiota-derived signals, and protect against mucosal pathogens. ILCs are classified into five major groups by their developmental origin and distinct cytokine production. A recently emerged intriguing feature of ILCs is their ability to alter their phenotype and function in response to changing local environmental cues such as pathogen invasion. Once the pathogen crosses host barriers, ILCs quickly activate cytokine production to limit the spread of the pathogen. However, the dysregulated ILC responses can lead to tissue inflammation and damage. Furthermore, the interplay between ILCs and other immune cell types shapes the outcome of the immune response. Recent studies highlighted the important role of ILCs for host defense against intracellular pathogens. Here, we review recent advances in understanding the mechanisms controlling protective and pathogenic ILC responses to intracellular pathogens. This knowledge can help develop new ILC-targeted strategies to control infectious diseases and immunopathology.

Campylobacter infection promotes IFNγ-dependent intestinal pathology via ILC3 to ILC1 conversion

Innate lymphoid cells (ILCs) are a heterogeneous family of immune regulators that protect against mucosal pathogens but can also promote intestinal pathology. Although the plasticity between ILCs populations has been described, the role of mucosal pathogens in inducing ILC conversion leading to intestinal pathology remains unclear. Here we demonstrate that IFNγ-producing ILCs are responsible for promoting intestinal pathology in a mouse model of enterocolitis caused by Campylobacter jejuni, a common human enteric pathogen. Phenotypic analysis revealed a distinct population of IFNγ-producing NK1.1^-T-bet⁺ILCs that accumulated in the intestine of C. jejuni-infected mice. Adoptive transfer experiments demonstrated their capacity to promote intestinal pathology. Inactivation of T-bet in NKp46⁺ ILCs ameliorated disease. Transcriptome analysis and cell-fate mapping experiments revealed that IFNγ-producing NK1.1^-ILCs correspond to ILC1 profile and develop from RORγt⁺ progenitors. Collectively, we identified a distinct population of NK1.1^-ex-ILC3s that promotes intestinal pathology through IFNγ production in response to C. jejuni infection.

Metagenomic Analysis of the Gut Microbiota of Wild Mice, a Newly Identified Reservoir of Campylobacter

Campylobacter, the most common etiologic agent of zoonotic gastroenteritis in humans, is present in many reservoirs including livestock animals, wildlife, soil, and water. Previously, we reported a novel Campylobacter jejuni strain SCJK02 (MLST ST-8388) from the gut of wild mice (Micromys minutus) using culture-dependent methods. However, due to fastidious growth conditions and the presence of viable but non-culturable Campylobacter spp., it is unclear whether M. minutus is a Campylobacter reservoir. This study aimed to: 1) determine the distribution and proportion of Campylobacter spp. in the gut microbiota of wild mice using culture-independent methods and 2) investigate the gut microbiota of wild mice and the relationship of Campylobacter spp. with other gut microbes. The gut microbiota of 38 wild mice captured from perilla fields in Korea and without any clinical symptoms (18 M. minutus and 20 Mus musculus) were analyzed. Metagenomic analysis showed that 77.8% (14 of 18) of the captured M. minutus harbored Campylobacter spp. (0.24–32.92%) in the gut metagenome, whereas none of the captured M. musculus carried Campylobacter spp. in their guts. Notably, 75% (6 of 8) of M. minutus determined to be Campylobacter-negative using culture-dependent methods showed a high proportion of Campylobacter through metagenome analysis. The results of metagenome analysis and the absence of clinical symptoms suggest that Campylobacter may be a component of the normal gut flora of wild M. minutus. Furthermore, linear discriminant analysis (LDA) showed that Campylobacter was the most enriched genus in the gut microbiota of M. minutus (LDA score, 5.37), whereas Lactobacillus was the most enriched genus in M. musculus (LDA score, −5.96). The differences in the presence of Campylobacter between the two species of wild mice may be attributed to the differential abundance of Campylobacter and Lactobacillus in their respective gut microbiota. In conclusion, the results indicate that wild M. minutus may serve as a potential Campylobacter reservoir. This study presents the first metagenomics analysis of the M. minutus gut microbiota to explore its possible role as an environmental Campylobacter reservoir and provides a basis for future studies using culture-independent methods to determine the role of environmental reservoirs in Campylobacter transmission.

IL-23 Contributes to Campylobacter jejuni-Induced Intestinal Pathology via Promoting IL-17 and IFNγ Responses by Innate Lymphoid Cells

Human pathogen Campylobacter jejuni is a significant risk factor for the development of long-term intestinal dysfunction although the cellular and molecular mechanisms remain scantily defined. IL-23 is an emerging therapeutic target for the treatment of inflammatory intestinal diseases, however its role in C. jejuni-driven intestinal pathology is not fully understood. IL-10 deficient mice represent a robust model to study the pathogenesis of C. jejuni infection because C. jejuni infection of mice lacking IL-10 results in symptoms and pathology that resemble human campylobacteriosis. To determine the role of IL-23 in C. jejuni-driven intestinal inflammation, we studied the disease pathogenesis in IL-23^-/- mice with inhibited IL-10Rα signaling. These mice exhibited reduced intestinal pathology independent from bacterial clearance. Further, levels of IFNγ, IL-17, IL-22, TNF, and IL-6 were reduced and associated with reduced accumulation of neutrophils, monocytes and macrophages in the colon. Flow cytometry analysis revealed reduced production of IL-17 and IFNγ by group 1 and 3 innate lymphoid cells. Thus, our data suggest that IL-23 contributes to intestinal inflammation in C. jejuni infected mice by promoting IL-17 and IFNγ production by innate lymphoid cells.

Murine Models for the Investigation of Colonization Resistance and Innate Immune Responses in Campylobacter Jejuni Infections

Human infections with the food-borne pathogen Campylobacter jejuni are progressively increasing worldwide and constitute a significant socioeconomic burden to mankind. Intestinal campylobacteriosis in humans is characterized by bloody diarrhea, fever, abdominal pain, and severe malaise. Some individuals develop chronic post-infectious sequelae including neurological and autoimmune diseases such as reactive arthritis and Guillain-Barré syndrome. Studies unraveling the molecular mechanisms underlying campylobacteriosis and post-infectious sequelae have been hampered by the scarcity of appropriate experimental in vivo models. Particularly, conventional laboratory mice are protected from C. jejuni infection due to the physiological colonization resistance exerted by the murine gut microbiota composition. Additionally, as compared to humans, mice are up to 10,000 times more resistant to C. jejuni lipooligosaccharide (LOS) constituting a major pathogenicity factor responsible for the immunopathological host responses during campylobacteriosis. In this chapter, we summarize the recent progress that has been made in overcoming these fundamental obstacles in Campylobacter research in mice. Modification of the murine host-specific gut microbiota composition and sensitization of the mice to C. jejuni LOS by deletion of genes encoding interleukin-10 or a single IL-1 receptor-related molecule as well as by dietary zinc depletion have yielded reliable murine infection models resembling key features of human campylobacteriosis. These substantial improvements pave the way for a better understanding of the molecular mechanisms underlying pathogen-host interactions. The ongoing validation and standardization of these novel murine infection models will provide the basis for the development of innovative treatment and prevention strategies to combat human campylobacteriosis and collateral damages of C. jejuni infections.

Microbiota attenuates chicken transmission-exacerbated campylobacteriosis in Il10-/- mice

Campylobacter jejuni is a prevalent foodborne pathogen mainly transmitting through poultry. It remains unknown how chicken-transmitted C. jejuni and microbiota impact on human campylobacteriosis. Campylobacter jejuni AR101 (Cj-P0) was introduced to chickens and isolated as passage 1 (Cj-P1). Campylobacter jejuni Cj-P1-DCA-Anaero was isolated from Cj-P0-infected birds transplanted with DCA-modulated anaerobic microbiota. Specific pathogen free Il10-/- mice were gavaged with antibiotic clindamycin and then infected with Cj-P0, Cj-P1, or Cj-P1-DCA-Anaero, respectively. After 8 days post infection, Il10-/- mice infected with Cj-P1 demonstrated severe morbidity and bloody diarrhea and the experiment had to be terminated. Cj-P1 induced more severe histopathology compared to Cj-P0, suggesting that chicken transmission increased C. jejuni virulence. Importantly, mice infected with Cj-P1-DCA-Anaero showed attenuation of intestinal inflammation compared to Cj-P1. At the cellular level, Cj-P1 induced more C. jejuni invasion and neutrophil infiltration into the Il10-/- mouse colon tissue compared to Cj-P0, which was attenuated with Cj-P1-DCA-Anaero. At the molecular level, Cj-P1 induced elevated inflammatory mediator mRNA accumulation of Il17a, Il1β, and Cxcl1 in the colon compared to Cj-P0, while Cj-P1-DCA-Anaero showed reduction of the inflammatory gene expression. In conclusion, our data suggest that DCA-modulated anaerobes attenuate chicken-transmitted campylobacteriosis in mice and it is important to control the elevation of C. jejuni virulence during chicken transmission process.

Influence of Genetic Background and Sex on Gene Expression in the Mouse (Mus musculus) Tail in a Model of Intervertebral Disc Injury

To facilitate rational experimental design and fulfill the NIH requirement of including sex as a biologic variable, we examined the influences of genetic background and sex on responses to intervertebral disc (IVD) injury in the mouse tail. The goal of this study was to compare gene expression and histologic changes in response to a tail IVD injury (needle puncture) in male and female mice on the DBA and C57BL/6 (B6) backgrounds. We hypothesized that extracellular matrix gene expression in response to IVD injury differs between mice of different genetic backgrounds and sex. Consistent changes were detected in gene expression and histologic features after IVD injury in mice on both genetic backgrounds and sexes. In particular, expression of col1a1 and adam8 was higher in the injured IVD of DBA mice than B6 mice. Conversely, col2a1 expression was higher in B6 mice than DBA mice. Sex-associated differences were significant only in B6 mice, in which col2a1 expression was greater in male mice than in female. Histologic differences in response to injury were not apparent between DBA and B6 mice or between males and females. In conclusion, mouse tail IVD showed sex- and strain-related changes in gene expression and histology after needle puncture. The magnitude of change in gene expression differed with regard to genetic background and, to a lesser degree, sex.

Effects of antibiotic resistance (AR) and microbiota shifts on Campylobacter jejuni-mediated diseases

Campylobacter jejuni is an important zoonotic pathogen recently designated a serious antimicrobial resistant (AR) threat. While most patients with C. jejuni experience hemorrhagic colitis, serious autoimmune conditions can follow including inflammatory bowel disease (IBD) and the acute neuropathy Guillain Barré Syndrome (GBS). This review examines inter-relationships among factors mediating C. jejuni diarrheal versus autoimmune disease especially AR C. jejuni and microbiome shifts. Because both susceptible and AR C. jejuni are acquired from animals or their products, we consider their role in harboring strains. Inter-relationships among factors mediating C. jejuni colonization, diarrheal and autoimmune disease include C. jejuni virulence factors and AR, the enteric microbiome, and host responses. Because AR C. jejuni have been suggested to affect the severity of disease, length of infections and propensity to develop GBS, it is important to understand how these interactions occur when strains are under selection by antimicrobials. More work is needed to elucidate host-pathogen interactions of AR C. jejuni compared with susceptible strains and how AR C. jejuni are maintained and evolve in animal reservoirs and the extent of transmission to humans. These knowledge gaps impair the development of effective strategies to prevent the emergence of AR C. jejuni in reservoir species and human populations.

Transplanted human fecal microbiota enhanced Guillain Barré syndrome autoantibody responses after Campylobacter jejuni infection in C57BL/6 mice

BACKGROUND

Campylobacter jejuni is the leading antecedent infection to the autoimmune neuropathy Guillain-Barré syndrome (GBS), which is accompanied by an autoimmune anti-ganglioside antibody attack on peripheral nerves. Previously, we showed that contrasting immune responses mediate C. jejuni induced colitis and autoimmunity in interleukin-10 (IL-10)-deficient mice, dependent upon the infecting strain. Strains from colitis patients elicited T helper 1 (T_H1)-dependent inflammatory responses while strains from GBS patients elicited T_H2-dependent autoantibody production. Both syndromes were exacerbated by antibiotic depletion of the microbiota, but other factors controlling susceptibility to GBS are unknown.

METHODS

Using 16S rRNA gene high-throughput sequencing, we examined whether structure of the gut microbial community alters host (1) gastrointestinal inflammation or (2) anti-ganglioside antibody responses after infection with C. jejuni strains from colitis or GBS patients. We compared these responses in C57BL/6 mice with either (1) stable human gut microbiota (^Humicrobiota) transplants or (2) conventional mouse microbiota (^Convmicrobiota).

RESULTS

Inoculating germ-free C57BL/6 wild-type (WT) mice with a mixed human fecal slurry provided a murine model that stably passed its microbiota over >20 generations. Mice were housed in specific pathogen-free (SPF) facilities, while extra precautions of having caretakers wear sterile garb along with limited access ensured that no mouse pathogens were acquired. ^Humicrobiota conferred many changes upon the WT model in contrast to previous results, which showed only colonization with no disease after C. jejuni challenge. When compared to ^Convmicrobiota mice for susceptibility to C. jejuni enteric or GBS patient strains, infected ^Humicrobiota mice had (1) 10-100 fold increases in C. jejuni colonization of both strains, (2) pathologic change in draining lymph nodes but only mild changes in colon or cecal lamina propria, (3) significantly lower Th1/Th17-dependent anti-C. jejuni responses, (4) significantly higher IL-4 responses at 5 but not 7 weeks post infection (PI), (5) significantly higher Th2-dependent anti-C. jejuni responses, and (6) significantly elevated anti-ganglioside autoantibodies after C. jejuni infection. These responses in ^Humicrobiota mice were correlated with a dominant Bacteroidetes and Firmicutes microbiota.

CONCLUSIONS

These data demonstrate that ^Humicrobiota altered host-pathogen interactions in infected mice, increasing colonization and Th-2 and autoimmune responses in a C. jejuni strain-dependent manner. Thus, microbiota composition is another factor controlling susceptibility to GBS.

Guillain Barré Syndrome is induced in Non-Obese Diabetic (NOD) mice following Campylobacter jejuni infection and is exacerbated by antibiotics

Campylobacter jejuni is a leading cause of bacterial gastroenteritis linked to several serious autoimmune sequelae such as the peripheral neuropathies Guillain Barré syndrome (GBS) and Miller Fisher syndrome (MFS). We hypothesized that GBS and MFS can result in NOD wild type (WT) mice or their congenic interleukin (IL)-10 or B7-2 knockouts secondary to C. jejuni infection. Mice were gavaged orally with C. jejuni strains HB93-13 and 260.94 from patients with GBS or CF93-6 from a patient with MFS and assessed for clinical neurological signs and phenotypes, anti-ganglioside antibodies, and cellular infiltrates and lesions in gut and peripheral nerve tissues. Significant increases in autoantibodies against single gangliosides (GM1, GQ1b, GD1a) occurred in infected NOD mice of all genotypes, although the isotypes varied (NOD WT had IgG1, IgG3; NOD B7-2^-/- had IgG3; NOD IL-10^-/- had IgG1, IgG3, IgG2a). Infected NOD WT and NOD IL-10^-/- mice also produced anti-ganglioside antibodies of the IgG1 isotype directed against a mixture of GM1/GQ1b gangliosides. Phenotypic tests showed significant differences between treatment groups of all mouse genotypes. Peripheral nerve lesions with macrophage infiltrates were significantly increased in infected mice of NOD WT and IL-10^-/- genotypes compared to sham-inoculated controls, while lesions with T cell infiltrates were significantly increased in infected mice of the NOD B7-2^-/- genotype compared to sham-inoculated controls. In both infected and sham inoculated NOD IL-10^-/- mice, antibiotic treatment exacerbated neurological signs, lesions and the amount and number of different isotypes of antiganglioside autoantibodies produced. Thus, inducible mouse models of post-C. jejuni GBS are feasible and can be characterized based on evaluation of three factors-onset of GBS clinical signs/phenotypes, anti-ganglioside autoantibodies and nerve lesions. Based on these factors we characterized 1) NOD B-7^-/- mice as an acute inflammatory demyelinating polyneuropathy (AIDP)-like model, 2) NOD IL-10^-/- mice as an acute motor axonal neuropathy (AMAN)-like model best employed over a limited time frame, and 3) NOD WT mice as an AMAN model with mild clinical signs and lesions. Taken together these data demonstrate that C. jejuni strain genotype, host genotype and antibiotic treatment affect GBS disease outcomes in mice and that many disease phenotypes are possible.

Campylobacter jejuni is not merely a commensal in commercial broiler chickens and affects bird welfare

Campylobacter jejuni is the leading cause of bacterial food-borne infection; chicken meat is its main source. C. jejuni is considered commensal in chickens based on experimental models unrepresentative of commercial production. Here we show that the paradigm of Campylobacter commensalism in the chicken is flawed. Through experimental infection of four commercial breeds of broiler chickens, we show that breed has a significant effect on C. jejuni infection and the immune response of the animals, although these factors have limited impact on the number of bacteria in chicken ceca. All breeds mounted an innate immune response. In some breeds, this response declined when interleukin-10 was expressed, consistent with regulation of the intestinal inflammatory response, and these birds remained healthy. In another breed, there was a prolonged inflammatory response, evidence of damage to gut mucosa, and diarrhea. We show that bird type has a major impact on infection biology of C. jejuni. In some breeds, infection leads to disease, and the bacterium cannot be considered a harmless commensal. These findings have implications for the welfare of chickens in commercial production where C. jejuni infection is a persistent problem. Importance: Campylobacter jejuni is the most common cause of food-borne bacterial diarrheal disease in the developed world. Chicken is the most common source of infection. C. jejuni infection of chickens had previously not been considered to cause disease, and it was thought that C. jejuni was part of the normal microbiota of birds. In this work, we show that modern rapidly growing chicken breeds used in intensive production systems have a strong inflammatory response to C. jejuni infection that can lead to diarrhea, which, in turn, leads to damage to the feet and legs on the birds due to standing on wet litter. The response and level of disease varied between breeds and is related to regulation of the inflammatory immune response. These findings challenge the paradigm that C. jejuni is a harmless commensal of chickens and that C. jejuni infection may have substantial impact on animal health and welfare in intensive poultry production:

Contrasting immune responses mediate Campylobacter jejuni-induced colitis and autoimmunity

Campylobacter jejuni is a leading cause of foodborne enteritis that has been linked to the autoimmune neuropathy, Guillain Barré syndrome (GBS). C57BL/6 interleukin (IL)-10(+/+) and congenic IL-10(-/-) mice serve as C. jejuni colonization and colitis models, respectively, but a mouse model for GBS is lacking. We demonstrate that IL-10(-/-) mice infected with a C. jejuni colitogenic human isolate had significantly upregulated type 1 and 17 but not type 2 cytokines in the colon coincident with infiltration of phagocytes, T cells and innate lymphoid cells (ILCs). Both ILC and T cells participated in interferon-γ (IFN-γ), IL-17, and IL-22 upregulation but in a time- and organ-specific manner. T cells were, however, necessary for colitis as mice depleted of Thy-1(+) cells were protected while neither Rag1(-/-) nor IL-10R blocked Rag1(-/-) mice developed colitis after infection. Depleting IFN-γ, IL-17, or both significantly ameliorated colitis and drove colonic responses toward type 2 cytokine and antibody induction. In contrast, C. jejuni GBS patient strains induced mild colitis associated with blunted type 1/17 but enhanced type 2 responses. Moreover, the type 2 but not type 1/17 antibodies cross-reacted with peripheral nerve gangliosides demonstrating autoimmunity.

Campylobacter jejuni colonization is associated with a dysbiosis in the cecal microbiota of mice in the absence of prominent inflammation

Background

Campylobacter jejuni causes enterocolitis in humans, but does not incite disease in asymptomatic carrier animals. To survive in the intestine, C. jejuni must successfully compete with the microbiota and overcome the host immune defense. Campylobacter jejuni colonization success varies considerably amongst individual mice, and we examined the degree to which the intestinal microbiota was affected in mice (i.e. a model carrier animal) colonized by C. jejuni at high relative to low densities.

Methods

Mice were inoculated with C. jejuni or buffer, and pathogen shedding and intestinal colonization were measured. Histopathologic scoring and quantification of mRNA expression for α-defensins, toll-like receptors, and cytokine genes were conducted. Mucosa-associated bacterial communities were characterized by two approaches: multiplexed barcoded pyrosequencing and terminal restriction fragment length polymorphism analysis.

Results

Two C. jejuni treatments were established based on the degree of cecal and colonic colonization; C. jejuni Group A animals were colonized at high cell densities, and C. jejuni Group B animals were colonized at lower cell densities. Histological examination of cecal and colonic tissues indicated that C. jejuni did not incite visible pathologic changes. Although there was no significant difference among treatments in expression of mRNA for α-defensins, toll-like receptors, or cytokine genes, a trend for increased expression of toll-like receptors and cytokine genes was observed for C. jejuni Group A. The results of the two methods to characterize bacterial communities indicated that the composition of the cecal microbiota of C. jejuni Group A mice differed significantly from C. jejuni Group B and Control mice. This difference was due to a reduction in load, diversity and richness of bacteria associated with the cecal mucosa of C. jejuni Group A mice.

Conclusions

High density colonization by C. jejuni is associated with a dysbiosis in the cecal microbiota independent of prominent inflammation.

Charles JL, Buffa BA, Brooks AP, Poe SA, Eaton KA, Stanhope MJ, Mansfield LS. Outcome of infection of C57BL/6 IL-10(-/-) mice with Campylobacter jejuni strains is correlated with genome content of open reading frames up- and down-regulated in vivo

Human Campylobacter jejuni infection can result in an asymptomatic carrier state, watery or bloody diarrhea, bacteremia, meningitis, or autoimmune neurological sequelae. Infection outcomes of C57BL/6 IL-10(-/-) mice orally infected with twenty-two phylogenetically diverse C. jejuni strains were evaluated to correlate colonization and disease phenotypes with genetic composition of the strains. Variation between strains was observed in colonization, timing of development of clinical signs, and occurrence of enteric lesions. Five pathotypes of C. jejuni in C57BL/6 IL-10(-/-) mice were delineated: little or no colonization, colonization without disease, colonization with enteritis, colonization with hemorrhagic enteritis, and colonization with neurological signs with or without enteritis. Virulence gene content of ten sequenced strains was compared in silico; virulence gene content of twelve additional strains was compared using a C. jejuni pan-genome microarray. Neither total nor virulence gene content predicted pathotype; nor was pathotype correlated with multilocus sequence type. Each strain was unique with regard to absences of known virulence-related loci and/or possession of point mutations and indels, including phase variation, in virulence-related genes. An experiment in C. jejuni 11168-infected germ-free mice showed that expression levels of ninety open reading frames (ORFs) were significantly up- or down-regulated in the mouse cecum at least two-fold compared to in vitro growth. Genomic content of these ninety C. jejuni 11168 ORFs was significantly correlated with the capacity to colonize and cause enteritis in C57BL/6 IL-10(-/-) mice. Differences in gene expression levels and patterns are thus an important determinant of pathotype in C. jejuni strains in this mouse model.

Phosphatidylinositol 3-kinase-γ signaling promotes Campylobacter jejuni-induced colitis through neutrophil recruitment in mice

Crypt abscesses caused by excessive neutrophil accumulation are prominent features of human campylobacteriosis and its associated pathology. The molecular and cellular events responsible for this pathological situation are currently unknown. We investigated the contribution of PI3K-γ signaling in Campylobacter jejuni-induced neutrophil accumulation and intestinal inflammation. Germ-free and specific pathogen-free Il10(-/-) and germ-free Il10(-/-);Rag2(-/-) mice were infected with C. jejuni (10(9) CFU/mouse). PI3K-γ signaling was manipulated using either the pharmacological PI3K-γ inhibitor AS252424 (i.p. 10 mg/kg daily) or genetically using Pi3k-γ(-/-) mice. After up to 14 d, inflammation was assessed histologically and by measuring levels of colonic Il1β, Cxcl2, and Il17a mRNA. Neutrophils were depleted using anti-Gr1 Ab (i.p. 0.5 mg/mouse/every 3 d). Using germ-free Il10(-/-);Rag2(-/-) mice, we observed that innate immune cells are the main cellular compartment responsible for campylobacteriosis. Pharmacological blockade of PI3K-γ signaling diminished C. jejuni-induced intestinal inflammation, neutrophil accumulation, and NF-κB activity, which correlated with reduced Il1β (77%), Cxcl2 (73%), and Il17a (72%) mRNA accumulation. Moreover, Pi3k-γ(-/-) mice pretreated with anti-IL-10R were resistant to C. jejuni-induced intestinal inflammation compared with Wt mice. This improvement was accompanied by a reduction of C. jejuni translocation into the colon and extraintestinal tissues and by attenuation of neutrophil migratory capacity. Furthermore, neutrophil depletion attenuated C. jejuni-induced crypt abscesses and intestinal inflammation. Our findings indicate that C. jejuni-induced PI3K-γ signaling mediates neutrophil recruitment and intestinal inflammation in Il10(-/-) mice. Selective pharmacological inhibition of PI3K-γ may represent a novel means to alleviate severe cases of campylobacteriosis, especially in antibiotic-resistant strains.

Campylobacter jejuni induces acute enterocolitis in gnotobiotic IL-10-/- mice via Toll-like-receptor-2 and -4 signaling

Background

Campylobacter jejuni is a leading cause of foodborne bacterial enterocolitis worldwide. Investigation of immunopathology is hampered by a lack of suitable vertebrate models. We have recently shown that gnotobiotic mice as well as conventional IL-10^−/− animals are susceptible to C. jejuni infection and develop intestinal immune responses. However, clinical symptoms of C. jejuni infection were rather subtle and did not reflect acute bloody diarrhea seen in human campylobacteriosis.

Methodology/Principal Findings

In order to overcome these limitations we generated gnotobiotic IL-10^−/− mice by quintuple antibiotic treatment starting right after weaning. The early treatment was essential to prevent these animals from chronic colitis. Following oral infection C. jejuni colonized the gastrointestinal tract at high levels and induced acute enterocolitis within 7 days as indicated by bloody diarrhea and pronounced histopathological changes of the colonic mucosa. Immunopathology was further characterized by increased numbers of apoptotic cells, regulatory T-cells, T- and B-lymphocytes as well as elevated TNF-α, IFN-γ, and MCP-1 concentrations in the inflamed colon. The induction of enterocolitis was specific for C. jejuni given that control animals infected with a commensal E. coli strain did not display any signs of disease. Most strikingly, intestinal immunopathology was ameliorated in mice lacking Toll-like-receptors-2 or -4 indicating that C. jejuni lipoproteins and lipooligosaccharide are essential for induction and progression of immunopathology.

Conclusion/Significance

Gnotobiotic IL-10^−/− mice develop acute enterocolitis following C. jejuni infection mimicking severe episodes of human campylobacteriosis and are thus well suited to further dissect mechanisms underlying Campylobacter infections in vivo.

Passage of Campylobacter jejuni through the chicken reservoir or mice promotes phase variation in contingency genes Cj0045 and Cj0170 that strongly associates with colonization and disease in a mouse model

Human illness due to Camplyobacter jejuni infection is closely associated with consumption of poultry products. We previously demonstrated a 50 % shift in allele frequency (phase variation) in contingency gene Cj1139 (wlaN) during passage of C. jejuni NCTC11168 populations through Ross 308 broiler chickens. We hypothesized that phase variation in contingency genes during chicken passage could promote subsequent colonization and disease in humans. To test this hypothesis, we passaged C. jejuni strains NCTC11168, 33292, 81-176, KanR4 and CamR2 through broiler chickens and analysed the ability of passaged and non-passaged populations to colonize C57BL6 IL-10-deficient mice, our model for human colonization and disease. We utilized fragment analysis and nucleotide sequence analysis to measure phase variation in contingency genes. Passage through the chicken reservoir promoted phase variation in five specific contingency genes, and these 'successful' populations colonized mice. When phase variation did not occur in these same five contingency genes during chicken passage, these 'unsuccessful' populations failed to colonize mice. Phase variation during chicken passage generated small insertions or deletions (indels) in the homopolymeric tract (HT) in contingency genes. Single-colony isolates of C. jejuni strain KanR4 carrying an allele of contingency gene Cj0170 with a10G HT colonized mice at high frequency and caused disease symptoms, whereas single-colony isolates carrying the 9G allele failed to colonize mice. Supporting results were observed for the successful 9G allele of Cj0045 in strain 33292. These data suggest that phase variation in Cj0170 and Cj0045 is strongly associated with mouse colonization and disease, and that the chicken reservoir can play an active role in natural selection, phase variation and disease.

What you eat is what you get: Novel Campylobacter models in the quadrangle relationship between nutrition, obesity, microbiota and susceptibility to infection

Enterocolitis caused by Campylobacter jejuni-infections represents an important socioeconomic burden worldwide. Recent results from novel murine infection models reveal that the intestinal microbiota is essential for maintaining colonization resistance against C. jejuni. We extended these studies to investigate the role of nutrition and obesity in susceptibility to C. jejuni-infection. Gnotobiotic (GB) mice generated by antibiotic treatment, which were fed with a human cafeteria diet (CAF), as well as obese (ob/ob) mice with a conventional microbiota harbored higher Escherichia coli loads in their colon as compared to respective controls. Following oral infection, C. jejuni 43431 ATCC readily colonized the intestines of CAF and ob/ob mice, whereas GB mice fed with a standard chow (MUD) eradicated the pathogen within days. Furthermore, live C. jejuni translocated into mesenteric lymph nodes of CAF, but not MUD mice. Strikingly, stably infected animals developed enterocolitis as indicated by increased numbers of immune and apoptotic cells in the colon in situ. We conclude that a specific human diet and obesity render mice susceptible to C. jejuni infection. The corresponding murine models are excellently suited for the study of C. jejuni pathogenesis and will help to get further insights into interplays between C. jejuni, microbiota, diet, obesity and immunity.

Novel murine infection models provide deep insights into the "ménage à trois" of Campylobacter jejuni, microbiota and host innate immunity

Background

Although Campylobacter jejuni-infections have a high prevalence worldwide and represent a significant socioeconomic burden, it is still not well understood how C. jejuni causes intestinal inflammation. Detailed investigation of C. jejuni-mediated intestinal immunopathology is hampered by the lack of appropriate vertebrate models. In particular, mice display colonization resistance against this pathogen.

Methodology/Principal Findings

To overcome these limitations we developed a novel C. jejuni-infection model using gnotobiotic mice in which the intestinal flora was eradicated by antibiotic treatment. These animals could then be permanently associated with a complete human (hfa) or murine (mfa) microbiota. After peroral infection C. jejuni colonized the gastrointestinal tract of gnotobiotic and hfa mice for six weeks, whereas mfa mice cleared the pathogen within two days. Strikingly, stable C. jejuni colonization was accompanied by a pro-inflammatory immune response indicated by increased numbers of T- and B-lymphocytes, regulatory T-cells, neutrophils and apoptotic cells, as well as increased concentrations of TNF-α, IL-6, and MCP-1 in the colon mucosa of hfa mice. Analysis of MyD88^−/−, TRIF^−/−, TLR4^−/−, and TLR9^−/− mice revealed that TLR4- and TLR9-signaling was essential for immunopathology following C. jejuni-infection. Interestingly, C. jejuni-mutant strains deficient in formic acid metabolism and perception induced less intestinal immunopathology compared to the parental strain infection. In summary, the murine gut flora is essential for colonization resistance against C. jejuni and can be overcome by reconstitution of gnotobiotic mice with human flora. Detection of C. jejuni-LPS and -CpG-DNA by host TLR4 and TLR9, respectively, plays a key role in immunopathology. Finally, the host immune response is tightly coupled to bacterial formic acid metabolism and invasion fitness.

Conclusion/Significance

We conclude that gnotobiotic and “humanized” mice represent excellent novel C. jejuni-infection and -inflammation models and provide deep insights into the immunological and molecular interplays between C. jejuni, microbiota and innate immunity in human campylobacteriosis.

Gnotobiotic IL-10; NF-kappaB mice develop rapid and severe colitis following Campylobacter jejuni infection

Limited information is available on the molecular mechanisms associated with Campylobacter jejuni (C. jejuni) induced food-borne diarrheal illnesses. In this study, we investigated the function of TLR/NF-kappaB signaling in C. jejuni induced pathogenesis using gnotobiotic IL-10(-/-); NF-kappaB(EGFP) mice. In vitro analysis showed that C. jejuni induced IkappaB phosphorylation, followed by enhanced NF-kappaB transcriptional activity and increased IL-6, MIP-2alpha and NOD2 mRNA accumulation in infected-mouse colonic epithelial cells CMT93. Importantly, these events were blocked by molecular delivery of an IkappaB inhibitor (Ad5IkappaBAA). NF-kappaB signalling was also important for C.jejuni-induced cytokine gene expression in bone marrow-derived dendritic cells. Importantly, C. jejuni associated IL-10(-/-); NF-kappaB(EGFP) mice developed mild (day 5) and severe (day 14) ulcerating colonic inflammation and bloody diarrhea as assessed by colonoscopy and histological analysis. Macroscopic analysis showed elevated EGFP expression indicating NF-kappaB activation throughout the colon of C. jejuni associated IL-10(-/-); NF-kappaB(EGFP) mice, while fluorescence microscopy revealed EGFP positive cells to be exclusively located in lamina propria mononuclear cells. Pharmacological NF-kappaB inhibition using Bay 11-7085 did not ameliorate C. jejuni induced colonic inflammation. Our findings indicate that C. jejuni induces rapid and severe intestinal inflammation in a susceptible host that correlates with enhanced NF-kappaB activity from lamina propria immune cells.

Immune response to and histopathology of Campylobacter jejuni infection in ferrets (Mustela putorius furo)

Campylobacter jejuni is 1 of the most common enteric bacterial pathogens worldwide. The mechanisms of pathogenesis remain obscure, in part because of limitations of small animal models. Young ferrets develop diarrhea when fed C. jejuni, but their pathology and the immune response after infection have not been examined in detail. In the present study, we examined the pathogenesis of C. jejuni CG8421 and associated immune responses in ferrets. After oral infection with C. jejuni CG8421, 86.7% of the animals developed diarrhea and inflammatory responses that were similar to those seen in human infection. Pronounced histopathologic changes in the colonic mucosa of infected animals were observed during the acute phase (days 1 through 3) of infection. Electron micrographs of colonic epithelium revealed disruption of the villi and internalized bacteria that were not within membrane vacuoles. During the acute phase, C. jejuni was isolated from the livers of 7 of 9 (78%) animals, and bacteria were visualized immunohistochemically in the livers from 5 of the 7 animals (71%) from which C. jejuni was isolated. A vigorous systemic and mucosal immune response to Campylobacter antigens was elicited after infection of ferrets. The data presented contribute to the current knowledge of the pathogenicity of and immunologic response to C. jejuni CG8421 in ferrets and better understanding of this model.

Recombinant interleukin-4 enhances Campylobacter jejuni invasion of intestinal pig epithelial cells (IPEC-1)

Campylobacter jejuni, a leading cause of bacterial gastroenteritis, has a diverse spectrum of disease expression. Polymicrobial infections may contribute to this, such as Trichuris, which elicits type 2 cytokines (including IL-4) and downregulates type 1 immunity. In previous studies, gnotobiotic piglets infected with C. jejuni and Trichuris suis had bloody diarrhea and marked gastrointestinal pathology, including bacterial invasion into epithelial cells and macrophages. Neonatal swine given these dual infections had elevated IL-4 and IL-10 responses in feces. In the studies reported here, we hypothesized that IL-4 or IL-10 enhances invasion of intestinal pig epithelial cells (IPEC-1) by C. jejuni. 10-14-day-old IPEC-1 cells were pretreated with recombinant IL-4 (rIL-4) or rIL-10 for 5h and then challenged with C. jejuni. Cells pretreated with rIL-4 were viable and showed approximately 6-fold increases in C. jejuni (but not Escherichia coli DH5alpha) internalization compared to cells with no pretreatment. Enhanced C. jejuni invasion was rIL-4 dose-dependent and reversed by addition of anti-IL-4 antibody. Preincubation with rIL-10 did not significantly alter C. jejuni internalization. Transepithelial electrical resistance (TEER) was significantly reduced following rIL-4 treatment, but not rIL-10 treatment. After rIL-4 pretreatment and C. jejuni challenge, light microscopy showed vacuolated cells with damaged paracellular junctions. Transmission electron microscopy (TEM) showed multiple internalized bacteria. Most were in the cytoplasm, but some were within or adjacent to vacuoles. We conclude that rIL-4 damages paracellular junctions and alters the physiology of these epithelial cells allowing increased invasion of C. jejuni.

Campylobacter jejuni-induced activation of dendritic cells involves cooperative signaling through Toll-like receptor 4 (TLR4)-MyD88 and TLR4-TRIF axes

Campylobacter jejuni is an important cause of human enteritis and has been linked to the development of autoimmune diseases. Recently we showed that infection of murine dendritic cells (DCs) with C. jejuni resulted in DC activation and induction of Campylobacter-specific Th1-effector responses. Toll-like receptor (TLR) signaling through myeloid differentiation factor 88 (MyD88) and/or Toll-interleukin 1 (IL-1) receptor domain-containing adaptor-inducing beta interferon (IFN-beta) (TRIF) is critical in inducing immunity against pathogens. In this study, we investigated the role of TLR2, TLR4, MyD88, and TRIF signaling in C. jejuni-induced inflammatory activation of DCs. DC upregulation of major histocompatibility complex class II and costimulatory molecules after C. jejuni challenge was profoundly impaired by TLR2, TLR4, MyD88, and TRIF deficiencies. Similarly, C. jejuni-induced secretion of IL-12, IL-6, and tumor necrosis factor alpha was significantly inhibited in TLR2(-/-), TLR4(-/-), MyD88(-/-), and TRIF(-/-) DCs compared to that in wild-type DCs; however, the magnitude of inhibition was greater in MyD88(-/-), TRIF(-/-), and TLR4(-/-) DCs than in TLR2(-/-) DCs. Furthermore, C. jejuni induced interferon regulatory factor 3 phosphorylation and IFN-beta secretion by DCs in a TLR4-TRIF-dependent fashion, further demonstrating activation of this pathway by C. jejuni. Importantly, TLR2, TLR4, MyD88, and TRIF deficiencies all markedly impaired the Th1-priming ability of C. jejuni-infected DCs. Thus, our results show that cooperative signaling through the TLR4-MyD88 and TLR4-TRIF axes represents a novel mechanism mediating C. jejuni-induced inflammatory responses of DCs. To our knowledge, such a mechanism has not been demonstrated previously for an intact bacterium.

Multiple factors interact to produce responses resembling spectrum of human disease in Campylobacter jejuni infected C57BL/6 IL-10-/- mice

BACKGROUND

Campylobacter jejuni infection produces a spectrum of clinical presentations in humans--including asymptomatic carriage, watery diarrhea, and bloody diarrhea--and has been epidemiologically associated with subsequent autoimmune neuropathies. This microorganism is genetically variable and possesses genetic mechanisms that may contribute to variability in nature. However, relationships between genetic variation in the pathogen and variation in disease manifestation in the host are not understood. We took a comparative experimental approach to explore differences among different C. jejuni strains and studied the effect of diet on disease manifestation in an interleukin-10 deficient mouse model.

RESULTS

In the comparative study, C57BL/6 interleukin-10-/- mice were infected with seven genetically distinct C. jejuni strains. Four strains colonized the mice and caused disease; one colonized with no disease; two did not colonize. A DNA:DNA microarray comparison of the strain that colonized mice without disease to C. jejuni 11168 that caused disease revealed that putative virulence determinants, including loci encoding surface structures known to be involved in C. jejuni pathogenesis, differed from or were absent in the strain that did not cause disease. In the experimental study, the five colonizing strains were passaged four times in mice. For three strains, serial passage produced increased incidence and degree of pathology and decreased time to develop pathology; disease shifted from watery to bloody diarrhea. Mice kept on an ~6% fat diet or switched from an approximately 12% fat diet to an approximately 6% fat diet just before infection with a non-adapted strain also exhibited increased incidence and severity of disease and decreased time to develop disease, although the effects of diet were only statistically significant in one experiment.

CONCLUSION

C. jejuni strain genetic background and adaptation of the strain to the host by serial passage contribute to differences in disease manifestations of C. jejuni infection in C57BL/6 IL-10-/- mice; differences in environmental factors such as diet may also affect disease manifestation. These results in mice reflect the spectrum of clinical presentations of C. jejuni gastroenteritis in humans and contribute to usefulness of the model in studying human disease.

Dendritic cells from C57BL/6 mice undergo activation and induce Th1-effector cell responses against Campylobacter jejuni

Food-borne Campylobacter jejuni (Cj) is an important cause of enteritis. We showed that C57BL/6 and congenic interleukin (IL)-10(-/-) mice serve as models of Cj colonization and enteritis, respectively. Thus, C57BL/6 mice are resistant to Cj induced disease. Because dendritic cells (DCs) are central to regulating adaptive immune responses, we investigated the interaction of Cj with murine bone marrow-derived DCs (BM-DCs) to assess bacterial killing, DC activation, and the ability of Cj-infected BM-DCs to stimulate Campylobacter-specific T cell responses in vitro. BM-DCs challenged with Cj efficiently internalized and killed Cj 11168 and significantly upregulated surface MHC-II, CD40, CD80 and CD86 demonstrating a mature phenotype. Infected BM-DCs secreted significant amounts of tumor necrosis factor-alpha (TNF-alpha), IL-6 and IL-12p70. Formalin-killed Cj also induced maturation of BM-DCs with similar cytokine production but at a significantly lower magnitude than live bacteria. Maximal activation of murine BM-DCs required internalization of Cj; attachment alone was not sufficient to elicit significant responses. Also, various strains of Cj elicited different magnitudes of cytokine production from BM-DCs. Finally, in a coculture system, Cj-infected BM-DCs induced high level interferon-gamma (INF-gamma) production from CD4+T cells indicating Th1 polarization. Thus, DCs from resistant C57BL/6 mice initiate T cell responses against Cj.