Matrix Metalloproteinase-2 Mediates Intestinal Immunopathogenesis in Campylobacter Jejuni-Infected Infant Mice

Toll-Like Receptor-4 Is Involved in Mediating Intestinal and Extra-Intestinal Inflammation in Campylobacter coli-Infected Secondary Abiotic IL-10-/- Mice

Human Campylobacter infections are emerging worldwide and constitute significant health burdens. We recently showed that the immunopathological sequelae in Campylobacter jejuni-infected mice were due to Toll-like receptor (TLR)-4 dependent immune responses induced by bacterial lipooligosaccharide (LOS). Information regarding the molecular mechanisms underlying Campylobacter coli-host interactions are scarce, however. Therefore, we analyzed C. coli-induced campylobacteriosis in secondary abiotic IL-10^−/− mice with and without TLR4. Mice were infected perorally with a human C. coli isolate or with a murine commensal Escherichia coli as apathogenic, non-invasive control. Independent from TLR4, C. coli and E. coli stably colonized the gastrointestinal tract, but only C. coli induced clinical signs of campylobacteriosis. TLR4^−/− IL-10^−/− mice, however, displayed less frequently fecal blood and less distinct histopathological and apoptotic sequelae in the colon versus IL-10^−/− counterparts on day 28 following C. coli infection. Furthermore, C. coli-induced colonic immune cell responses were less pronounced in TLR4^−/− IL-10^−/− as compared to IL-10^−/− mice and accompanied by lower pro-inflammatory mediator concentrations in the intestines and the liver of the former versus the latter. In conclusion, our study provides evidence that TLR4 is involved in mediating C. coli-LOS-induced immune responses in intestinal and extra-intestinal compartments during murine campylobacteriosis.

Pituitary Adenylate Cyclase-Activating Polypeptide Alleviates Intestinal, Extra-Intestinal and Systemic Inflammatory Responses during Acute Campylobacter jejuni-induced Enterocolitis in Mice

Human Campylobacter jejuni infections are emerging, and constitute a significant health burden worldwide. The ubiquitously expressed pituitary adenylate cyclase-activating polypeptide (PACAP) is well-known for its cell-protective and immunomodulatory effects. In our actual intervention study, we used an acute campylobacteriosis model and assessed the potential disease-alleviating effects of exogenous PACAP. Therefore, secondary abiotic IL-10^-/- mice were perorally infected with C. jejuni and treated with synthetic PACAP38 intraperitoneally from day 2 until day 5 post-infection. Whereas PACAP did not interfere with the gastrointestinal colonization of the pathogen, mice from the PACAP group exhibited less severe clinical signs of C. jejuni-induced disease, as compared to mock controls, which were paralleled by alleviated apoptotic, but enhanced cell proliferative responses in colonic epithelia on day 6 post-infection. Furthermore, PACAP dampened the accumulation of macrophages and monocytes, but enhanced regulatory T cell responses in the colon, which were accompanied by less IFN-γ secretion in intestinal compartments in PACAP versus mock-treated mice. Remarkably, the inflammation-dampening properties of PACAP could also be observed in extra-intestinal organs, and strikingly, even the systemic circulation on day 6 post-infection. For the first time, we provide evidence that synthetic PACAP might be a promising candidate to combat acute campylobacteriosis and post-infectious sequelae.

The Host-Specific Intestinal Microbiota Composition Impacts Campylobacter coli Infection in a Clinical Mouse Model of Campylobacteriosis

Human Campylobacter-infections are progressively rising globally. However, the molecular mechanisms underlying C. coli–host interactions are incompletely understood. In this study, we surveyed the impact of the host-specific intestinal microbiota composition during peroral C. coli infection applying an established murine campylobacteriosis model. Therefore, microbiota-depleted IL-10^−/− mice were subjected to peroral fecal microbiota transplantation from murine versus human donors and infected with C. coli one week later by gavage. Irrespective of the microbiota, C. coli stably colonized the murine gastrointestinal tract until day 21 post-infection. Throughout the survey, C. coli-infected mice with a human intestinal microbiota displayed more frequently fecal blood as their murine counterparts. Intestinal inflammatory sequelae of C. coli-infection could exclusively be observed in mice with a human intestinal microbiota, as indicated by increased colonic numbers of apoptotic epithelial cells and innate as well as adaptive immune cell subsets, which were accompanied by more pronounced pro-inflammatory cytokine secretion in the colon and mesenteric lymph nodes versus mock controls. However, in extra-intestinal, including systemic compartments, pro-inflammatory responses upon pathogen challenge could be assessed in mice with either microbiota. In conclusion, the host-specific intestinal microbiota composition has a profound effect on intestinal and systemic pro-inflammatory immune responses during C. coli infection.

Inflammatory Immune Responses and Gut Microbiota Changes Following Campylobacter coli Infection of IL-10-/- Mice with Chronic Colitis

Human infections with the food-borne enteropathogens Campylobacter are progressively rising. Recent evidence revealed that pre-existing intestinal inflammation facilitates enteropathogenic infection subsequently exacerbating the underlying disease. Given that only little is known about C. coli-host interactions and particularly during intestinal inflammation, the aim of the present study was to survey gastrointestinal colonization properties, gut microbiota changes and pro-inflammatory sequelae upon peroral C. coli-infection of IL-10^-/- mice with chronic colitis. C. coli colonized the gastrointestinal tract of mice with varying efficiencies until day 28 post-infection and induced macroscopic and microscopic inflammatory changes as indicated by shorter colonic lengths, more distinct histopathological changes in the colonic mucosa and higher numbers of apoptotic colonic epithelial cells when compared to mock-infected controls. Furthermore, not only colonic innate and adaptive immune cell responses, but also enhanced systemic TNF-α secretion could be observed following C. coli as opposed to mock challenge. Notably, C. coli induced intestinal inflammatory sequelae were accompanied with gut microbiota shifts towards higher commensal enterobacterial loads in the infected gut lumen. Moreover, the pathogen translocated from the intestinal tract to extra-intestinal tissue sites in some cases, but never to systemic compartments. Hence, C. coli accelerates inflammatory immune responses in IL-10^-/- mice with chronic colitis.

Toll-Like Receptor-4 Dependent Intestinal and Systemic Sequelae Following Peroral Campylobacter coli Infection of IL10 Deficient Mice Harboring a Human Gut Microbiota

Zoonotic Campylobacter, including C. jejuni and C. coli, are among the most prevalent agents of food-borne enteritis worldwide. The immunopathological sequelae of campylobacteriosis are caused by Toll-like Receptor-4 (TLR4)-dependent host immune responses, induced by bacterial lipooligosaccharide (LOS). In order to investigate C. coli-host interactions, including the roles of the human gut microbiota and TLR4, upon infection, we applied a clinical acute campylobacteriosis model, and subjected secondary abiotic, TLR4-deficient IL10-/- mice and IL10-/- controls to fecal microbiota transplantation derived from human donors by gavage, before peroral C. coli challenge. Until day 21 post-infection, C. coli could stably colonize the gastrointestinal tract of human microbiota-associated (hma) mice of either genotype. TLR4-deficient IL10-/- mice, however, displayed less severe clinical signs of infection, that were accompanied by less distinct apoptotic epithelial cell and innate as well as adaptive immune cell responses in the colon, as compared to IL10-/- counterparts. Furthermore, C. coli infected IL10-/-, as opposed to TLR4-deficient IL10-/-, mice displayed increased pro-inflammatory cytokine concentrations in intestinal and, strikingly, systemic compartments. We conclude that pathogenic LOS might play an important role in inducing TLR4-dependent host immune responses upon C. coli infection, which needs to be further addressed in more detail.

The conundrum of colonization resistance against Campylobacter reloaded: The gut microbota composition in conventional mice does not prevent from Campylobacter coli infection

The physiological colonization resistance exerted by the murine gut microbiota prevents conventional mice from Campylobacter jejuni infection. In the present study we addressed whether this also held true for Campylobacter coli. Following peroral application, C. coli as opposed to C.jejuni could stably establish within the gastrointestinal tract of conventionally colonized mice until 3 weeks post-challenge. Neither before nor after either Campylobacter application any changes in the gut microbiota composition could be observed. C. coli, but not C. jejuni challenge was associated with pronounced regenerative, but not apoptotic responses in colonic epithelia. At day 21 following C. coli versus C. jejuni application mice exhibited higher numbers of adaptive immune cells including T-lymphocytes and regulatory T-cells in the colonic mucosa and lamina propria that were accompanied by higher large intestinal interferon-γ (IFN-γ) concentrations in the former versus the latter but comparable to naive levels. Campylobacter application resulted in decreased splenic IFN-γ, tumor necrosis factor-α (TNF-α), and IL-6 concentrations, whereas IL-12p70 secretion was increased in the spleens at day 21 following C. coli application only. In either Campylobacter cohort decreased IL-10 concentrations could be measured in splenic and serum samples. In conclusion, the commensal gut microbiota prevents mice from C. jejuni, but not C. coli infection.

Carvacrol ameliorates acute campylobacteriosis in a clinical murine infection model

BACKGROUND

The prevalence of human infections with the zoonotic pathogen Campylobacter jejuni is rising worldwide. Therefore, the identification of compounds with potent anti-pathogenic and anti-inflammatory properties for future therapeutic and/or preventive application to combat campylobacteriosis is of importance for global health. Results of recent studies suggested carvacrol (4-isopropyl-2-methylphenol) as potential candidate molecule for the treatment of campylobacteriosis in humans and for the prevention of Campylobacter colonization in farm animals.

RESULTS

To address this in a clinical murine infection model of acute campylobacteriosis, secondary abiotic IL-10-/- mice were subjected to synthetic carvacrol via the drinking water starting 4 days before peroral C. jejuni challenge. Whereas at day 6 post-infection placebo treated mice suffered from acute enterocolitis, mice from the carvacrol cohort not only harbored two log orders of magnitude lower pathogen loads in their intestines, but also displayed significantly reduced disease symptoms. Alleviated campylobacteriosis following carvacrol application was accompanied by less distinct intestinal apoptosis and pro-inflammatory immune responses as well as by higher numbers of proliferating colonic epithelial cells. Remarkably, the inflammation-ameliorating effects of carvacrol treatment were not restricted to the intestinal tract, but could also be observed in extra-intestinal organs such as liver, kidneys and lungs and, strikingly, systemically as indicated by lower IFN-γ, TNF, MCP-1 and IL-6 serum concentrations in carvacrol versus placebo treated mice. Furthermore, carvacrol treatment was associated with less frequent translocation of viable C. jejuni originating from the intestines to extra-intestinal compartments.

CONCLUSION

The lowered C. jejuni loads and alleviated symptoms observed in the here applied clinical murine model for human campylobacteriosis highlight the application of carvacrol as a promising novel option for both, the treatment of campylobacteriosis and hence, for prevention of post-infectious sequelae in humans, and for the reduction of C. jejuni colonization in the intestines of vertebrate lifestock animals.

Murine fecal microbiota transplantation lowers gastrointestinal pathogen loads and dampens pro-inflammatory immune responses in Campylobacter jejuni infected secondary abiotic mice

Conventional mice are protected from Campylobacter jejuni infection by the murine host-specific gut microbiota composition. We here addressed whether peroral fecal microbiota transplantation (FMT) might be an antibiotics-independent option to lower even high gastrointestinal C. jejuni loads in the infected vertebrate host. To address this, secondary abiotic mice were generated by broad-spectrum antibiotic treatment and perorally infected with C. jejuni by gavage. One week later, mice were stably colonized with more than 109 C. jejuni and subjected to peroral FMT from murine donors on three consecutive days. Two weeks post-intervention, gastrointestinal C. jejuni loads were up to 7.5 orders of magnitude lower following murine FMT versus mock challenge. Remarkably, FMT reversed C. jejuni induced colonic epithelial apoptosis, but enhanced proliferative and regenerative responses in the colon thereby counteracting pathogenic cell damage. Furthermore, FMT dampened both, innate and adaptive immune cell responses in the large intestines upon C. jejuni infection that were accompanied by less C. jejuni-induced colonic nitric oxide secretion. Our study provides strong evidence that novel probiotic formulations developed as alternative option to FMT in severe intestinal inflammatory morbidities including Clostridoides difficile infection might be effective to treat campylobacteriosis and lower pathogen loads in colonized vertebrates including farm animals.

Murine Fecal Microbiota Transplantation Alleviates Intestinal and Systemic Immune Responses in Campylobacter jejuni Infected Mice Harboring a Human Gut Microbiota

Human campylobacteriosis constitutes a zoonotic food-borne disease and a progressively rising health burden of significant socioeconomic impact. We have recently shown that conventional mice are protected from Campylobacter jejuni infection, which was not the case for human microbiota associated (hma) mice indicating that the host-specific gut microbiota composition primarily determines susceptibility to or resistance against C. jejuni infection. In our present preclinical intervention study we addressed whether gut microbiota changes in stably C. jejuni infected hma mice following murine fecal microbiota transplantation (mFMT) could alleviate pathogen-induced immune responses. To accomplish this, secondary abiotic C57BL/6 mice were generated by broad-spectrum antibiotic treatment, perorally reassociated with a complex human gut microbiota and challenged with C. jejuni by gavage. Seven days later C. jejuni infected hma mice were subjected to peroral mFMT on 3 consecutive days. Within a week post-mFMT fecal pathogenic burdens had decreased by two orders of magnitude, whereas distinct changes in the gut microbiota composition with elevated numbers of lactobacilli and bifidobacteria could be assessed. In addition, mFMT resulted in less C. jejuni induced apoptotic responses in colonic epithelia, reduced numbers of macrophages and monocytes as well as of T lymphocytes in the large intestinal mucosa and lamina propria and in less distinct intestinal pro-inflammatory cytokine secretion as compared to mock challenge. Strikingly, inflammation dampening effects of mFMT were not restricted to the intestinal tract, but could also be observed systemically as indicated by elevated serum concentrations of pro-inflammatory cytokines such as TNF-α, IL-12p70, and IL-6 in C. jejuni infected hma mice of the mock, but not the mFMT cohort. In conclusion, our preclinical mFMT intervention study provides evidence that changes in the gut microbiota composition which might be achieved by pre- or probiotic formulations may effectively lower intestinal C. jejuni loads, dampen both, pathogen-induced intestinal and systemic inflammatory sequelae and may represent a useful tool to treat continuous shedding of C. jejuni by asymptomatic carriers which is critical in the context of food production, hospitalization and immunosuppression.

Vitamin D in Acute Campylobacteriosis-Results From an Intervention Study Applying a Clinical Campylobacter jejuni Induced Enterocolitis Model

Human Campylobacter infections are progressively rising and of high socioeconomic impact. In the present preclinical intervention study we investigated anti-pathogenic, immuno-modulatory, and intestinal epithelial barrier preserving properties of vitamin D applying an acute campylobacteriosis model. Therefore, secondary abiotic IL-10^−/− mice were perorally treated with synthetic 25-OH-cholecalciferol starting 4 days before peroral Campylobacter jejuni infection. Whereas, 25-OH-cholecalciferol application did not affect gastrointestinal pathogen loads, 25-OH-cholecalciferol treated mice suffered less frequently from diarrhea in the midst of infection as compared to placebo control mice. Moreover, 25-OH-cholecalciferol application dampened C. jejuni induced apoptotic cell responses in colonic epithelia and promoted cell-regenerative measures. At day 6 post-infection, 25-OH-cholecalciferol treated mice displayed lower numbers of colonic innate and adaptive immune cell populations as compared to placebo controls that were accompanied by lower intestinal concentrations of pro-inflammatory mediators including IL-6, MCP1, and IFN-γ. Remarkably, as compared to placebo application synthetic 25-OH-cholecalciferol treatment of C. jejuni infected mice resulted in lower cumulative translocation rates of viable pathogens from the inflamed intestines to extra-intestinal including systemic compartments such as the kidneys and spleen, respectively, which was accompanied by less compromised colonic epithelial barrier function in the 25-OH-cholecalciferol as compared to the placebo cohort. In conclusion, our preclinical intervention study provides evidence that peroral synthetic 25-OH-cholecalciferol application exerts inflammation-dampening effects during acute campylobacteriosis.

Immunopathological properties of the Campylobacter jejuni flagellins and the adhesin CadF as assessed in a clinical murine infection model

Background

Campylobacter jejuni infections constitute serious threats to human health with increasing prevalences worldwide. Our knowledge regarding the molecular mechanisms underlying host–pathogen interactions is still limited. Our group has established a clinical C. jejuni infection model based on abiotic IL-10^−/− mice mimicking key features of human campylobacteriosis. In order to further validate this model for unraveling pathogen-host interactions mounting in acute disease, we here surveyed the immunopathological features of the important C. jejuni virulence factors FlaA and FlaB and the major adhesin CadF (Campylobacter adhesin to fibronectin), which play a role in bacterial motility, protein secretion and adhesion, respectively.

Methods and results

Therefore, abiotic IL-10^−/− mice were perorally infected with C. jejuni strain 81-176 (WT) or with its isogenic flaA/B (ΔflaA/B) or cadF (ΔcadF) deletion mutants. Cultural analyses revealed that WT and ΔcadF but not ΔflaA/B bacteria stably colonized the stomach, duodenum and ileum, whereas all three strains were present in the colon at comparably high loads on day 6 post-infection. Remarkably, despite high colonic colonization densities, murine infection with the ΔflaA/B strain did not result in overt campylobacteriosis, whereas mice infected with ΔcadF or WT were suffering from acute enterocolitis at day 6 post-infection. These symptoms coincided with pronounced pro-inflammatory immune responses, not only in the intestinal tract, but also in other organs such as the liver and kidneys and were accompanied with systemic inflammatory responses as indicated by increased serum MCP-1 concentrations following C. jejuni ΔcadF or WT, but not ΔflaA/B strain infection.

Conclusion

For the first time, our observations revealed that the C. jejuni flagellins A/B, but not adhesion mediated by CadF, are essential for inducing murine campylobacteriosis. Furthermore, the secondary abiotic IL-10^−/− infection model has been proven suitable not only for detailed investigations of immunological aspects of campylobacteriosis, but also for differential analyses of the roles of distinct C. jejuni virulence factors in induction and progression of disease.

Electronic supplementary material

The online version of this article (10.1186/s13099-019-0306-9) contains supplementary material, which is available to authorized users.

Protease Activity of Campylobacter jejuni HtrA Modulates Distinct Intestinal and Systemic Immune Responses in Infected Secondary Abiotic IL-10 Deficient Mice

Even though human Campylobacter jejuni infections are progressively increasing worldwide, the underlying molecular mechanisms of pathogen-host-interactions are still not fully understood. We have recently shown that the secreted serine protease HtrA plays a key role in C. jejuni cellular invasion and transepithelial migration in vitro, and is involved in the onset of intestinal pathology in murine infection models in vivo. In the present study, we investigated whether the protease activity of HtrA had an impact in C. jejuni induced acute enterocolitis. For this purpose, we perorally infected secondary abiotic IL-10^-/- mice with wildtype C. jejuni strain NCTC11168 (11168^WT) or isogenic bacteria carrying protease-inactive HtrA with a single point mutation at S197A in the active center (11168^HtrA-S197A). Irrespective of the applied pathogenic strain, mice harbored similar C. jejuni loads in their feces and exhibited comparably severe macroscopic signs of acute enterocolitis at day 6 postinfection (p.i.). Interestingly, the 11168^HtrA-S197A infected mice displayed less pronounced colonic apoptosis and immune cell responses, but enhanced epithelial proliferation as compared to the 11168^WT strain infected controls. Furthermore, less distinct microscopic sequelae in 11168^HtrA-S197A as compared to parental strain infected mice were accompanied by less distinct colonic secretion of pro-inflammatory cytokines such as MCP-1, IL-6, TNF, and IFN-γ in the former as compared to the latter. Strikingly, the S197A point mutation was additionally associated with less pronounced systemic pro-inflammatory immune responses as assessed in serum samples. In conclusion, HtrA is a remarkable novel virulence determinant of C. jejuni, whose protease activity is not required for intestinal colonization and establishment of disease, but aggravates campylobacteriosis by triggering apoptosis and pro-inflammatory immune responses.

Multidrug-Resistant Pseudomonas aeruginosa Accelerate Intestinal, Extra-Intestinal, and Systemic Inflammatory Responses in Human Microbiota-Associated Mice With Subacute Ileitis

The globally rising incidences of multidrug-resistant (MDR) Pseudomonas aeruginosa (Psae) in humans and live-stock animals has prompted the World Health Organization to rate MDR Psae as serious threat for human health. Only little is known, however, regarding factors facilitating gastrointestinal Psae-acquisition by the vertebrate host and subsequently induced inflammatory sequelae. In the present study, we addressed whether subacute ileitis predisposed mice harboring a human gut microbiota for intestinal MDR Psae carriage and whether inflammatory responses might be induced following peroral challenge with the opportunistic pathogen. To accomplish this, secondary abiotic mice were associated with a human gut microbiota by fecal microbiota transplantation. Ten days later (i.e., on day 0), subacute ileitis was induced in human microbiota associated (hma) mice by peroral low-dose Toxoplasma gondii infection. On day 5 post-infection, mice were perorally challenged with 10⁹ colony forming units of a clinical MDR Psae isolate by gavage and the fecal bacterial loads surveyed thereafter. Four days post-peroral challenge, only approximately one third of mice with a human gut microbiota and subacute ileitis harbored the opportunistic pathogen in the intestinal tract. Notably, the gut microbiota composition was virtually unaffected by the Psae-carriage status during subacute ileitis of hma mice. The Psae challenge resulted, however, in more pronounced intestinal epithelial apoptotic cell and T lymphocyte responses upon ileitis induction that were not restricted to the ileum, but also affected the large intestines. Higher Psae-induced abundances of T cells could additionally be observed in extra-intestinal compartments including liver, kidney, lung, and heart of hma mice with subacute ileitis. Furthermore, higher apoptotic cell numbers, but lower anti-inflammatory IL-10 concentrations were assessed in the liver of Psae as compared to mock treated mice with ileitis. Remarkably, Psae-challenge was accompanied by even more pronounced systemic secretion of pro-inflammatory cytokines such as TNF and IL-6 at day 9 post ileitis induction. In conclusion, whereas in one third of hma mice with subacute ileitis Psae could be isolated from the intestines upon peroral challenge, the opportunistic pathogen was responsible for inflammatory sequelae in intestinal, extra-intestinal, and even systemic compartments and thus worsened subacute ileitis outcome irrespective of the Psae-carrier status.

Enhanced Systemic Response of Matrix Metalloproteinases and Their Regulators in Campylobacter and Salmonella Patients

Campylobacters are major enteropathogens worldwide with a substantial financial burden. Matrix metalloproteinases (MMPs) are proteolytic metalloendopeptidases with ability to modify immune response and shown to be upregulated in patients with several tissue destructive diseases, including infections. We measured here serum concentrations of MMP-8 and MMP-9 together with their regulators myeloperoxidase (MPO), human neutrophil elastase (HNE), and tissue inhibitor of metalloproteinases (TIMP)-1 in 80 Campylobacter and 25 Salmonella patients as well as in 27 healthy controls. Paired serum samples were available for 73 and 23 patients, respectively. When the initial serum samples were compared to those from controls, both Campylobacter and Salmonella patients showed elevated concentrations of all biomarkers tested (p ≤ 0.037). In the follow-up samples, collected about 25 days afterwards, MMP-8 levels of Campylobacter patients had already turned to normal but all the other biomarkers still showed elevated, although from the initial levels significantly dropped, levels. For the follow-up samples of Salmonella patients, only MMP-9 and MPO levels were at a significantly higher level than in controls. It remains to be studied if the systematically enhanced neutrophil-derived proteolytic and oxidative stress, induced by Campylobacter infection as shown here and persisting for several weeks, is important for the development of late sequelae.

Comparisons of gut microbiota profiles in wild-type and gelatinase B/matrix metalloproteinase-9-deficient mice in acute DSS-induced colitis

Gut microbiota help to educate the immune system and a number of involved immune cells were recently characterized. However, specific molecular determinants in these processes are not known, and, reciprocally, little information exists about single host determinants that alter the microbiota. Gelatinase B/matrix metalloproteinase-9 (MMP-9), an innate immune regulator and effector, has been suggested as such a host determinant. In this study, acute colitis was induced in co-housed MMP-9^-/- mice (n = 10) and their wild-type (WT) littermates (n = 10) via oral administration of 3% dextran sodium sulfate (DSS) for 7 days followed by 2 days of regular drinking water. Control mice (10 WT and 10 MMP-9^-/-) received normal drinking water. Fecal samples were collected at time of sacrifice and immediately frozen at −80 °C. Microbiota analysis was performed using 16S rRNA amplicon sequencing on Illumina MiSeq and taxonomic annotation was performed using the Ribosomal Database Project as reference. Statistical analysis correcting for multiple testing was done using R. No significant differences in clinical or histopathological parameters were found between both genotypes with DSS-induced colitis. Observed microbial richness at genus level and microbiota composition were not significantly influenced by host genotype. In contrast, weight loss, disease activity index, cage, and phenotype did significantly influence the intestinal microbiota composition. After multivariate analysis, cage and phenotype were identified as the sole drivers of microbiota composition variability. In conclusion, changes in fecal microbiota composition were not significantly altered in MMP-9-deficient mice compared to wild-type littermates, but instead were mainly driven by DSS-induced colonic inflammation.

A protein that regulates aspects of the immune system has been proposed to influence gut microbial populations implicated in the inflammatory conditions known as colitis, but new evidence suggests the protein has no such effect. Ghislain Opdenakker and colleagues at the Rega Institute for Medical Research in Belgium examined the issue in mice with chemically induced colitis. The gut microbes of normal “wild-type” animals were compared with those in animals lacking the gene for the protein, “gelatinase B/matrix metalloproteinase-9”. The absence of the gene, and therefore of the protein it codes for, caused no significant alteration in the gut microbial population. The presence of colitis, however, did alter the gut microbial population relative to mice with no colitis. The results will assist work to understand the networks of cause and effect linking gut microbes and colitis.

The octapetide NAP alleviates intestinal and extra-intestinal anti-inflammatory sequelae of acute experimental colitis

The octapeptide NAP has been shown to exert neuroprotective properties and reduce neuro-inflammatory responses. The aim of the present study was to investigate if NAP provides anti-inflammatory effects in acute murine colitis. To address this, C57BL/6 j mice were challenged with 3.5% dextran sulfate sodium from day 0 until day 6 to induce colitis, either treated intraperitoneally with NAP or placebo (NaCl 0.9%) from day 1 until day 6 post-induction (p.i.) and subjected to in depth macroscopic, microscopic and immunological evaluations. Whereas NAP application did not alleviate macroscopic (i.e. clinical) sequelae of colitis, lower numbers of apoptotic, but higher counts of proliferating/regenerating colonic epithelial cells could be observed in NAP as compared to placebo treated mice at day 7 p.i. Furthermore, lower numbers of adaptive immune cells such as T lymphocytes and regulatory T cells were abundant in the colonic mucosa and lamina propria upon NAP versus placebo treatment that were accompanied by less colonic secretion of pro-inflammatory mediators including IFN-γ and nitric oxide at day 7 p.i. In mesenteric lymph nodes, pro-inflammatory IFN-γ, TNF and IL-6 concentrations were increased in placebo, but not NAP treated mice at day 7 p.i., whereas interestingly, elevated anti-inflammatory IL-10 levels could be observed in NAP treated mice only. The assessed anti-inflammatory properties of NAP were not restricted to the intestinal tract, given that in extra-intestinal compartments such as the kidneys, IFN-γ levels increased in placebo, but not NAP treated mice upon colitis induction. NAP induced effects were accompanied by distinct changes in intestinal microbiota composition, given that colonic luminal loads of bifidobacteria, regarded as anti-inflammatory, "health-promoting" commensal species, were two orders of magnitude higher in NAP as compared to placebo treated mice and even naive controls. In conclusion, NAP alleviates intestinal and extra-intestinal pro-inflammatory sequelae of acute experimental colitis and may provide novel treatment options of intestinal inflammatory diseases in humans.

Intestinal and Systemic Immune Responses upon Multi-drug Resistant Pseudomonas aeruginosa Colonization of Mice Harboring a Human Gut Microbiota

The World Health Organization has rated multi-drug resistant (MDR) Pseudomonas aeruginosa as serious threat for human health. It is, however, unclear, whether intestinal MDR P. aeruginosa carriage is associated with inflammatory responses in intestinal or even systemic compartments. In the present study, we generated with respect to their microbiota "humanized" mice by human fecal microbiota transplantation of secondary abiotic mice. Following peroral challenge with a clinical P. aeruginosa isolate on two consecutive days, mice harboring a human or murine microbiota were only partially protected from stable intestinal P. aeruginosa colonization given that up to 78% of mice were P. aeruginosa-positive at day 28 post-infection (p.i.). Irrespective of the host-specificity of the microbiota, P. aeruginosa colonized mice were clinically uncompromised. However, P. aeruginosa colonization resulted in increased intestinal epithelial apoptosis that was accompanied by pronounced proliferative/regenerative cell responses. Furthermore, at day 7 p.i. increased innate immune cell populations such as macrophages and monocytes could be observed in the colon of mice harboring either a human or murine microbiota, whereas this held true at day 28 p.i. for adaptive immune cells such as B lymphocytes in both the small and large intestines of mice with murine microbiota. At day 7 p.i., pro-inflammatory cytokine secretion was enhanced in the colon and mesenteric lymph nodes, whereas the anti-inflammatory cytokine IL-10 was down-regulated in the former at day 28 p.i. Strikingly, cytokine responses upon intestinal P. aeruginosa colonization were not restricted to the intestinal tract, but could also be observed systemically, given that TNF and IFN-γ concentrations were elevated in spleens as early as 7 days p.i., whereas splenic IL-10 levels were dampened at day 28 p.i. of mice with human microbiota. In conclusion, mere intestinal carriage of MDR P. aeruginosa by clinically unaffected mice results in pro-inflammatory sequelae not only in intestinal, but also systemic compartments.

Toll-Like Receptor-4 Dependent Inflammatory Responses Following Intestinal Colonization of Secondary Abiotic IL10-Deficient Mice with Multidrug-Resistant Pseudomonas Aeruginosa

The rising incidences of infections with multidrug-resistant (MDR) Gram-negative bacteria including Pseudomonas aeruginosa (PA) have gained increasing attention in medicine, but also in the general public and global health politics. The mechanisms underlying opportunistic pathogen–host interactions are unclear, however. To address this, we challenged secondary abiotic IL10^–/– mice deficient for Toll-like receptor-4 (TLR4^–/– × IL10^–/–), the main receptor of the Gram-negative cell wall constituent lipopolysaccharide, with a clinical MDR PA isolate. Despite higher intestinal colonization densities, apoptotic colonic epithelial cell numbers were lower in TLR4^–/– × IL10^–/– mice as compared to IL10^–/– controls at day 14 postinfection (p.i.), whereas proliferating/regenerating cells had increased in the latter only. Furthermore, PA-colonized TLR4^–/– × IL10^–/– mice displayed less distinct innate and adaptive immune cell responses in the colon as compared to IL10^–/– counterparts that were accompanied by lower nitric oxide concentrations in mesenteric lymph nodes in the former at day 14 p.i. Conversely, splenic NO levels were higher in both naive and PA-colonized TLR4-deficient IL10^–/– mice versus IL10^–/– controls. Remarkably, intestinal MDR PA was able to translocate to extra-intestinal including systemic compartments of TLR4^–/– × IL10^–/– mice only. Hence, MDR PA-induced intestinal and systemic immune responses observed in secondary abiotic IL10^–/– mice are TLR4-dependent.

Multidrug-Resistant Pseudomonas Aeruginosa Induce Systemic Pro-Inflammatory Immune Responses in Colonized Mice

The World Health Organization has rated multidrug-resistant (MDR) Pseudomonas aeruginosa as a critical threat to human health. In the present study, we performed a survey of intestinal colonization, and local and systemic immune responses following peroral association of secondary abiotic mice with either a clinical MDR P. aeruginosa or a commensal murine Escherichia coli isolate. Depletion of the intestinal microbiota following antibiotic treatment facilitated stable intestinal colonization of both P. aeruginosa and E. coli that were neither associated with relevant clinical nor histopathological sequelae. Either stable bacterial colonization, however, resulted in distinct innate and adaptive immune cell responses in the intestines, whereas a pronounced increase in macrophages and monocytes could be observed in the small as well as large intestines upon P. aeruginosa challenge only, which also applied to colonic T lymphocytes. In addition, TNF secretion was exclusively elevated in large intestines of P. aeruginosa-colonized mice. Strikingly, association of secondary abiotic mice with MDR P. aeruginosa, but not commensal E. coli, resulted in pronounced systemic pro-inflammatory responses, whereas anti-inflammatory responses were dampened. Hence, intestinal carriage of MDR P. aeruginosa as compared to a mere commensal Gram-negative strain in otherwise healthy individuals results in distinct local and systemic pro-inflammatory sequelae.

Absence of Nucleotide-Oligomerization-Domain-2 Is Associated with Less Distinct Disease in Campylobacter jejuni Infected Secondary Abiotic IL-10 Deficient Mice

Human Campylobacter jejuni-infections are progressively increasing worldwide. Despite their high prevalence and socioeconomic impact the underlying mechanisms of pathogen-host-interactions are only incompletely understood. Given that the innate immune receptor nucleotide-oligomerization-domain-2 (Nod2) is involved in clearance of enteropathogens, we here evaluated its role in murine campylobacteriosis. To address this, we applied Nod2-deficient IL-10-/- (Nod2-/- IL-10-/-) mice and IL-10-/- counterparts both with a depleted intestinal microbiota to warrant pathogen-induced enterocolitis. At day 7 following peroral C. jejuni strain 81-176 infection, Nod2 mRNA was down-regulated in the colon of secondary abiotic IL-10-/- and wildtype mice. Nod2-deficiency did neither affect gastrointestinal colonization nor extra-intestinal and systemic translocation properties of C. jejuni. Colonic mucin-2 mRNA was, however, down-regulated upon C. jejuni-infection of both Nod2-/- IL-10-/- and IL-10-/- mice, whereas expression levels were lower in infected, but also naive Nod2-/- IL-10-/- mice as compared to respective IL-10-/- controls. Remarkably, C. jejuni-infected Nod2-/- IL-10-/- mice were less compromised than IL-10-/- counterparts and displayed less distinct apoptotic, but higher regenerative cell responses in colonic epithelia. Conversely, innate as well as adaptive immune cells such as macrophages and monocytes as well as T lymphocytes and regulatory T-cells, respectively, were even more abundant in large intestines of Nod2-/- IL-10-/- as compared to IL-10-/- mice at day 7 post-infection. Furthermore, IFN-γ concentrations were higher in ex vivo biopsies derived from intestinal compartments including colon and mesenteric lymph nodes as well as in systemic tissue sites such as the spleen of C. jejuni infected Nod2-/- IL-10-/- as compared to IL10-/- counterparts. Whereas, at day 7 postinfection anti-inflammatory IL-22 mRNA levels were up-regulated, IL-18 mRNA was down-regulated in large intestines of Nod2-/- IL-10-/- vs. IL-10-/- mice. In summary, C. jejuni-infection induced less clinical signs and apoptosis, but more distinct colonic pro- and (of note) anti-inflammatory immune as well as regenerative cell responses in Nod2 deficient IL-10-/- as compared to IL-10-/- control mice. We conclude that, even though colonic Nod2 mRNA was down-regulated upon pathogenic challenge, Nod2-signaling is essentially involved in the well-balanced innate and adaptive immune responses upon C. jejuni-infection of secondary abiotic IL-10-/- mice, but does neither impact pathogenic colonization nor translocation.

Small Intestinal Pro-Inflammatory Immune Responses Following Campylobacter Jejuni Infection of Secondary Abiotic IL-10-/- Mice Lacking Nucleotide-Oligomerization-Domain-2

Host immune responses are crucial for combating enteropathogenic infections including Campylobacter jejuni. Within 1 week following peroral C. jejuni infection, secondary abiotic IL-10^–/– mice develop severe immunopathological sequelae affecting the colon (ulcerative enterocolitis). In the present study, we addressed whether pathogen-induced pro-inflammatory immune responses could also be observed in the small intestines dependent on the innate receptor nucleotide-oligomerization-domain-protein 2 (Nod2). Within 7 days following peroral infection, C. jejuni stably colonized the gastrointestinal tract of both IL-10^–/– mice lacking Nod2 (Nod2^–/– IL-10^–/–) and IL-10^–/– controls displaying bloody diarrhea with similar frequencies. Numbers of apoptotic and regenerating epithelial cells increased in the small intestines of C. jejuni-infected mice of either genotype that were accompanied by elevated ileal T and B lymphocyte counts. Notably, ileal T cell numbers were higher in C. jejuni-infected Nod2^–/– IL-10^–/– as compared to IL-10^–/– counterparts. Furthermore, multifold increased concentrations of pro-inflammatory cytokines including IFN-γ, TNF, and MCP-1 could be measured in small intestinal ex vivo biopsies derived from C. jejuni-infected mice of either genotype. In conclusion, C. jejuni-induced pro-inflammatory immune responses affected the small intestines of both Nod2^–/– IL-10^–/– and IL-10^–/– mice, whereas ileal T lymphocyte numbers were even higher in the former.

Immune responses upon Campylobacter jejuni infection of secondary abiotic mice lacking nucleotide-oligomerization-domain-2

Background

Campylobacter jejuni infections are of rising importance worldwide. Given that innate immune receptors including nucleotide-oligomerization-domain-2 (Nod2) are essentially involved in combating enteropathogenic infections, we here surveyed the impact of Nod2 in murine campylobacteriosis.

Methods and results

In order to overcome physiological colonization resistance preventing from C. jejuni infection, we generated secondary abiotic Nod2^−/− and wildtype (WT) mice by broad-spectrum antibiotic treatment. Mice were then perorally infected with C. jejuni strain 81-176 on 2 consecutive days and could be stably colonized by the pathogen at high loads. Notably, Nod2 deficiency did not affect gastrointestinal colonization properties of C. jejuni. Despite high intestinal pathogenic burdens mice were virtually uncompromised and exhibited fecal blood in single cases only. At day 7 postinfection (p.i.) similar increases in numbers of colonic epithelial apoptotic cells could be observed in mice of either genotype, whereas C. jejuni infected Nod2^−/− mice displayed more distinct regenerative properties in the colon than WT controls. C. jejuni infection was accompanied by increases in distinct immune cell populations such as T lymphocytes and regulatory T cells in mice of either genotype. Increases in T lymphocytes, however, were less pronounced in large intestines of Nod2^−/− mice at day 7 p.i. when compared to WT mice, whereas colonic numbers of B lymphocytes were elevated in WT controls only upon C. jejuni infection. At day 7 p.i., colonic pro-inflammatory mediators including nitric oxide, TNF, IFN-γ and IL-22 increased more distinctly in Nod2^−/− as compared to WT mice, whereas C. jejuni induced IL-23p19 and IL-18 levels were lower in the large intestines of the former. Converse to the colon, however, ileal concentrations of nitric oxide, TNF, IFN-γ, IL-6 and IL-10 were lower in Nod2^−/− as compared to WT mice at day 7 p.i. Even though MUC2 was down-regulated in C. jejuni infected Nod2^−/− mice, this did not result in increased pathogenic translocation from the intestinal tract to extra-intestinal compartments.

Conclusion

In secondary abiotic mice, Nod2 signaling is involved in the orchestrated host immune responses upon C. jejuni infection, but does not control pathogen loads in the gastrointestinal tract.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-017-0182-0) contains supplementary material, which is available to authorized users.

Lactobacillus johnsonii ameliorates intestinal, extra-intestinal and systemic pro-inflammatory immune responses following murine Campylobacter jejuni infection

Campylobacter jejuni infections are progressively increasing worldwide. Probiotic treatment might open novel therapeutic or even prophylactic approaches to combat campylobacteriosis. In the present study secondary abiotic mice were generated by broad-spectrum antibiotic treatment and perorally reassociated with a commensal murine Lactobacillus johnsonii strain either 14 days before (i.e. prophylactic regimen) or 7 days after (i.e. therapeutic regimen) peroral C. jejuni strain 81-176 infection. Following peroral reassociation both C. jejuni and L. johnsonii were able to stably colonize the murine intestinal tract. Neither therapeutic nor prophylactic L. johnsonii application, however, could decrease intestinal C. jejuni burdens. Notably, C. jejuni induced colonic apoptosis could be ameliorated by prophylactic L. johnsonii treatment, whereas co-administration of L. johnsonii impacted adaptive (i.e. T and B lymphocytes, regulatory T cells), but not innate (i.e. macrophages and monocytes) immune cell responses in the intestinal tract. Strikingly, C. jejuni induced intestinal, extra-intestinal and systemic secretion of pro-inflammatory mediators (such as IL-6, MCP-1, TNF and nitric oxide) could be alleviated by peroral L. johnsonii challenge. In conclusion, immunomodulatory probiotic species might offer valuable strategies for prophylaxis and/or treatment of C. jejuni induced intestinal, extra-intestinal as well as systemic pro-inflammatory immune responses in vivo.

Campylobacter jejuni infection of conventionally colonized mice lacking nucleotide-oligomerization-domain-2

Background

The nucleotide-binding oligomerisaton protein 2 (NOD2) constitutes a pivotal sensor of bacterial muramyl dipeptide and assures expression of distinct antimicrobial peptides and mediators produced by enterocytes and immune cells directed against pathogens including Campylobacter jejuni. We here elucidated the role of NOD2 during murine C. jejuni infection in more detail.

Results

Conventionally colonized NOD2 deficient (NOD2^−/−) mice and corresponding wildtype (WT) counterparts were perorally infected with C. jejuni strain 81–176 on three consecutive days. The pathogen colonized both WT and NOD2^−/− mice only sporadically until day 14 post infection (p.i.). However, the slightly higher prevalence of C. jejuni in NOD2^−/− mice was accompanied by higher intestinal Escherichia coli loads known to facilitate C. jejuni colonization. Neither overt macroscopic (clinical) nor microscopic sequelae (such as colonic epithelial apoptosis) could be observed upon murine C. jejuni infection of either genotype. Innate immune responses were less distinctly induced in C. jejuni infected NOD2^−/− versus WT mice as indicated by lower colonic numbers of neutrophils in the former. Conversely, adaptive immune cell counts including T lymphocytes were higher in large intestines of NOD2^−/− as compared to WT mice that were paralleled by increased colonic IL-6 secretion and higher TNF and IL-18 mRNA expression levels in large intestines of the former. Only in NOD2^−/− mice, however, colonic IL-22 mRNA expression was down-regulated at day 14 p.i. Whereas viable commensal intestinal bacteria could exclusively be detected in mesenteric lymph nodes and livers of NOD2^−/− mice, bacterial translocation rates to kidneys and spleen were NOD2 independent. Notably, large intestinal mRNA expression levels of mucin-2, constituting a pivotal factor involved in epithelial barrier integrity, were comparable in naive and C. jejuni infected mice of either genotype.

Conclusion

NOD2 is involved in the well-balanced regulation of innate and adaptive pro-inflammatory immune responses of conventional mice upon C. jejuni infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-017-0155-3) contains supplementary material, which is available to authorized users.

Microbiota Composition and Immune Responses During Campylobacter Jejuni Infection in Conventionally Colonized IL-10-/- Mice Lacking Nucleotide Oligomerization Domain 2

Host immune responses are pivotal for combating enteropathogenic infections. We here assessed the impact of the innate receptor nucleotide oligomerization domain protein 2 (NOD2) in murine Campylobacter jejuni-infection. Conventionally colonized IL-10^–/– mice lacking NOD2 and IL-10^–/– controls were perorally challenged with C. jejuni strain 81-176 and displayed comparable pathogenic colonization of intestines until day 14 postinfection (p.i.). Whereas overall intestinal microbiota compositions were comparable in naive mice, NOD2^–/– IL-10^–/– mice exhibited less fecal bifidobacteria and lactobacilli than IL-10^–/– counterparts after infection. Interestingly, NOD2^–/– IL-10^–/– mice were clinically more compromised during the early phase of infection, whereas, conversely, IL-10^–/– animals exhibited more frequently bloody feces lateron. While colonic apoptotic cell and T lymphocyte numbers were comparable in either C. jejuni-infected mice, B lymphocytes were lower in the colon of infected NOD2^–/– IL-10^–/– mice versus controls. At day 14 p.i., colonic TNF and IL-23p19 mRNA levels were upregulated in NOD2^–/– IL-10^–/– mice only. Translocation rates of intestinal commensals to mesenteric lymphnodes and extra-intestinal compartments including liver and kidney were comparable, whereas viable bacteria were more frequently detected in spleens derived from IL-10^–/– as compared to NOD2^–/– IL-10^–/– mice. In conclusion, NOD2 is involved during C. jejuni infection in conventionally colonized IL-10^–/– mice in a time-dependent manner.

The IL-23/IL-22/IL-18 axis in murine Campylobacter jejuni infection

Background

Human Campylobacter jejuni infections are worldwide on the rise. Information about the distinct molecular mechanisms underlying campylobacteriosis, however, are scarce. In the present study we investigated whether cytokines including IL-23, IL-22 and IL-18 sharing pivotal functions in host immunity were involved in mediating immunopathological responses upon C. jejuni infection.

Results

To address this, conventionally colonized IL-23p19^−/−, IL-22^−/− and IL-18^−/− mice were perorally infected with C. jejuni strain ATCC 43431. Respective gene-deficient, but not wildtype mice were susceptible to C. jejuni infection and could be readily colonized with highest pathogenic loads in the terminal ileum and colon at day 14 postinfection (p.i.). In IL-23p19^−/−, IL-22^−/− and IL-18^−/− mice viable C. jejuni were detected in MLNs, but did not translocate to spleen, liver, kidney and blood in the majority of cases. Susceptible IL-22^−/−, but neither IL-23p19^−/−, nor IL-18^−/− mice harbored higher intestinal commensal E. coli loads when compared to resistant wildtype mice. Alike C. jejuni, commensal E. coli did not translocate from the intestinal to extra-intestinal tissue sites. Despite C. jejuni infection, mice lacking IL-23p19, IL-22 or IL-18 exhibited less apoptotic cells, but higher numbers of proliferating cells in their colonic epithelium as compared to wildtype mice at day 14 p.i. Less pronounced apoptosis was parallelled by lower abundance of neutrophils within the colonic mucosa and lamina propria of infected IL-23p19^−/− and IL-22^−/− as compared to wildtype control mice, whereas less distinct colonic TNF secretion could be measured in IL-22^−/− and IL-18^−/− than in wildtype mice at day 14 p.i. Notably, in infected IL-22^−/− mice, colonic IL-23p19 mRNA levels were lower, whereas the other way round, colonic IL-22 expression rates were lower in IL-23p19^−/− mice as compared to wildtype controls. Moreover, IL-18 mRNA was less distinctly expressed in large intestines of naive and infected IL-22^−/− mice, but not vice versa, given that IL-22 mRNA levels did not differ between in IL-18^−/− and wildtype mice.

Conclusion

Cytokines belonging to the IL-23/IL-22/IL-18 axis mediate immunopathological responses upon murine C. jejuni infection in a differentially orchestrated manner. Future studies need to further unravel the underlying regulatory mechanisms orchestrating pathogenic-host interaction.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-016-0106-4) contains supplementary material, which is available to authorized users.

Interleukin-18 Mediates Immune Responses to Campylobacter jejuni Infection in Gnotobiotic Mice

BACKGROUND

Human Campylobacter jejuni infections are progressively rising worldwide. Information about the molecular mechanisms underlying campylobacteriosis, however, are limited. In the present study we investigated whether cytokines such as IL-23, IL-22 and IL-18, which share pivotal functions in host immunity, were involved in mediating intestinal and systemic immunopathological responses upon C. jejuni infection.

METHODOLOGY/PRINCIPAL FINDINGS

To assure stable infection, gnotobiotic (i.e. secondary abiotic) IL-23p19-/-, IL-22-/- and IL-18-/- mice were generated by broad-spectrum antibiotic treatment. Following peroral C. jejuni strain 81-176 infection, mice of all genotypes harbored comparably high pathogenic loads in their intestines. As compared to wildtype controls, however, IL-18-/- mice displayed less distinct C. jejuni induced sequelae as indicated by less pronounced large intestinal shrinkage and lower numbers of apoptotic cells in the colonic epithelial layer at day 8 postinfection (p.i.). Furthermore, lower colonic numbers of adaptive immune cells including regulatory T cells and B lymphocytes were accompanied by less distinct secretion of pro-inflammatory cytokines such as TNF and IFN-γ and lower IL-17A mRNA expression levels in colonic ex vivo biopsies of infected IL-18-/- as compared to wildtype mice. Upon C. jejuni infection, colonic IL-23p19 expression was up-regulated in IL-18-/- mice only, whereas IL-22 mRNA levels were lower in uninfected and infected IL-23p19-/- as well as infected IL-18-/- as compared to respective wildtype control mice. Remarkably, not only intestinal, but also systemic infection-induced immune responses were less pronounced in IL-18-/- mice as indicated by lower TNF, IFN-γ and IL-6 serum levels as compared to wildtype mice.

CONCLUSION/SIGNIFICANCE

We here show for the first time that IL-18 is essentially involved in mediating C. jejuni infection in the gnotobiotic mouse model. Future studies need to further unravel the underlying regulatory mechanisms orchestrating pathogen-host interaction.

Colonic Expression of Genes Encoding Inflammatory Mediators and Gelatinases During Campylobacter Jejuni Infection of Conventional Infant Mice

Within 1 week following peroral Campylobacter jejuni infection, infant mice develop acute enteritis resolving thereafter. We here assessed colonic expression profiles of mediators belonging to the IL-23/IL-22/IL-18 axis and of matrix-degrading gelatinases MMP-2 and MMP-9 at day 6 post C. jejuni strain 81-176 infection. Whereas the pathogen readily colonized the intestines of infant IL-18^–/– mice only, colonic mucin-2 mRNA, a pivotal mucus constituent, was downregulated in IL-22^–/– mice and accompanied by increased expression of pro-inflammatory cytokines including IFN-γ, TNF, IL-17A, and IL-1β. Furthermore, in both naive and infected IL-22^–/– mice, colonic expression of IL-23p19 and IL-18 was lower as compared to wildtype mice, whereas, conversely, colonic IL-22 mRNA levels were lower in IL-18^–/– and colonic IL-18 expression lower in IL-23p19^–/– as compared to wildtype mice. Moreover, colonic expression of MMP-2 and MMP-9 and their endogenous inhibitor TIMP-1 were lower in IL-22^–/– as compared to wildtype mice at day 6 postinfection. In conclusion, mediators belonging of the IL-23/IL-22/IL-18 axis as well as the gelatinases MMP-2 and MMP-9 are involved in mediating campylobacteriosis of infant mice in a differentially regulated fashion.

The Role of IL-23, IL-22, and IL-18 in Campylobacter Jejuni Infection of Conventional Infant Mice

We have recently shown that, within 1 week following peroral Campylobacter jejuni infection, conventional infant mice develop self-limiting enteritis. We here investigated the role of IL-23, IL-22, and IL-18 during C. jejuni strain 81-176 infection of infant mice. The pathogen efficiently colonized the intestines of IL-18(-/-) mice only, but did not translocate to extra-intestinal compartments. At day 13 postinfection (p.i.), IL-22(-/-) mice displayed lower colonic epithelial apoptotic cell numbers as compared to wildtype mice, whereas, conversely, colonic proliferating cells increased in infected IL-22(-/-) and IL-18(-/-) mice. At day 6 p.i., increases in neutrophils, T and B lymphocytes were less pronounced in gene-deficient mice, whereas regulatory T cell numbers were lower in IL-23p19(-/-) and IL-22(-/-) as compared to wildtype mice, which was accompanied by increased colonic IL-10 levels in the latter. Until then, colonic pro-inflammatory cytokines including TNF, IFN-γ, IL-6, and MCP-1 increased in IL-23p19(-/-) mice, whereas IL-18(-/-) mice exhibited decreased cytokine levels and lower colonic numbers of T and B cell as well as of neutrophils, macrophages, and monocytes as compared to wildtype controls. In conclusion, IL-23, IL-22, and IL-18 are differentially involved in mediating C. jejuni-induced immunopathology of conventional infant mice.

Intestinal Expression of Genes Encoding Inflammatory Mediators and Gelatinases During Arcobacter Butzleri Infection of Gnotobiotic Il-10 Deficient Mice

We have previously shown that Arcobacter butzleri induces intestinal, extra-intestinal, and systemic immune responses in perorally infected gnotobiotic IL-10(-/-) mice in a strain-dependent fashion. Here, we present a comprehensive survey of small and large intestinal expression profiles of inflammatory and regulatory mediators as well as of the matrix-degrading gelatinases MMP-2 and MMP-9 following murine A. butzleri infection. Gnotobiotic IL-10(-/-) mice were infected with A. butzleri strains CCUG 30485 or C1 of human and chicken origin, respectively. At day 6 following A. butzleri infection, mucin-2 mRNA, an integral part of the intestinal mucus layer, was downregulated in the colon, whereas TNF and IL-23p19 mRNA were upregulated in the ileum. Furthermore, IFN-γ, IL-17A, IL-1β, and IL-22 mRNA were upregulated in both colonic and ileal ex vivo biopsies at day 6 post strain CCUG 30485 infection. These changes were accompanied by downregulated colonic MMP-9 levels, whereas both MMP-2 and MMP-9 mRNA were upregulated in the ileum. In conclusion, these data indicate that A. butzleri infection induces changes in the expression of genes involved in pro-inflammatory and regulatory immune responses as well as in tissue degradation.

The Role of Gelatinases in Campylobacter Jejuni Infection of Gnotobiotic Mice

Matrix metalloproteinases (MMP)-2 and -9 (also referred to gelatinases-A and -B, respectively) are upregulated in the inflamed gut of mice and men. We recently demonstrated that synthetic gelatinase blockage reduced large intestinal pro-inflammatory immune responses and apoptosis following murine Campylobacter (C.) jejuni infection. In order to address which gelatinase mediates C. jejuni-induced immune responses, gnotobiotic MMP-2(-/-), MMP-9(-/-), and wildtype (WT) mice were generated by broadspectrum antibiotic treatment and perorally infected with C. jejuni strain 81-176. The pathogen stably colonized the murine intestinal tract irrespective of the genotype but did not translocate to extra-intestinal compartments. At days 8 and 14 postinfection (p.i.), less pronounced colonic histopathological changes were observed in infected MMP-2(-/-) mice, less distinct epithelial apoptosis, but more epithelial proliferation in both MMP-2(-/-) and MMP-9(-/-) mice, as compared to WT controls. Reduced immune responses in gelatinase-deficient mice were characterized by lower numbers of effector as well as innate and adaptive immune cells within the colonic mucosa and lamina propria. The expression of IL-22, IL-18, IL-17A, and IL-1β mRNA was higher in the colon of MMP-2(-/-) as compared to WT mice. In conclusion, both MMP-2 and MMP-9 are differentially involved in mediating C. jejuni-induced intestinal immunopathology.