Tu1721 Shigella Spp. Adversely Affect Paracellular Permeability in In Vitro and Ex-Vivo Models of Intestinal Mucosa
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on severity of colitis induced by identical microbiota and 2) transfer of microbiota fromdifferent genetic backgrounds on induction of colitis in wild-type (WT) and KO mice ofeach strain. Methods: Germ- free KO or WT mice on B6 or 129 backgrounds were colonizedwith specific pathogen free feces (Helicobacter species-free) from 129 WT or B6 WT mice(Taconic) and evaluated 2 and 6 weeks post inoculation (PI). Colitis severity was evaluatedby blinded histological scores combined with measurement of cytokines secreted by MLNcells stimulated by cecal bacterial lysates (CBL). Lamina propria (LP) Th1/Th17 T cells wereanalyzed by flow cytometry (FACS). Results: No colitis was seen in B6WT or 129WTrecipients inoculated with B6 or 129 feces. At 2 weeks PI, KO mice on both B6 or 129backgrounds that were colonized with B6 feces developed more aggressive colitis comparedwith mild/moderate disease in those mice inoculated with 129 feces (p ,0.05, Table). B6feces induced more aggressive inflammation in B6KO than in 129 KO mice (p ,0.05)accompanied by higher levels of IL-17, IFN and IL-12/23p40 production by CBL- stimulatedMLN cells (p,0.05-0.005). Interestingly, B6KO and 129KO mice colonized with 129 fecesdisplayed no obvious differences in severity of colitis and production of IL-17 and IFN byMLN cells. FACS assay showed that frequency of IFN +- (2.4 vs. 1.8% of total LP cells) andIL-17+- CD4+ T cells (1.4 vs. 0.9%) in LP was higher in B6 feces B6KO mice vs.129fecesB6KO. At 6 weeks PI, increased colitis and elevated cytokine secretion were seen in129 KO vs. B6KO mice inoculated with B6 feces (p ,0.05 & 0.005). The source of fecalcolonization did not consistently affect the intensity of chronic colitis or cytokine secretionin B6KO or 129KO recipients. Conclusions: IL-10-/- mice on the B6 background developedaggressive colitis earlier than mice on a 129 background and remained stable or evendecreased with passage of time in contrast to 129 KO mice, which displayed progressivelyincreased colitis that exceeded that of B6 KO mice by 6 weeks. Different sources of fecesinfluence the severity of disease in IL-10 KO mice, particularly early in disease course,perhaps before host genetic background alters the microbiota.
CD103+ Dcs Contribute to the Manifestation of Citrobacter RodentiumInduced ColitisVera Kitowski, Markus F. Neurath, Raja Atreya, Kai HIldner
Dendritic cells (DC) are crucial orchestrators of adaptive immune responses during mucosalinflammatory conditions and infections. Furthermore, previous data under participation ofour group showed that certain pathogens specifically target subpopulations of dendritic cells(DC) to gain access to the infected host. For example, after i.v. administration Listeriamonocytogenes specifically infect CD8a+ DCs, which results in the transport of bacteriafrom the marginal zone into the T-cell zone of the white pulp. Mice deficient for thetranscription factor Batf3 lack CD8a+ and related CD103+ DC and are therefore protectedagainst i.v. Listeria infection. Here we seek to examine the contribution of mucosal CD103+DCs to intestinal inflammation and infection in the Citrobacter rodentium colitis modelusing Batf3-/- mice lacking CD103+CD11b- DCs. Oral Citrobacter rodentium (C. r.) infectioninduces colitis in mice and is widely accepted as a colitis model for human-pathogenic E.coli infections like EHEC. Following up the course of infection for more than 21 days afterp.o. infection of wildtype or Batf3-/- mice with a bioluminescent strain of C. r by in vivobioluminescence imaging, bacterial counts increased in wildtype mice and peaked at day7-10. In contrast, Batf3-/- mice were virtually protected against the expansion of C. r. invivo and displayed significantly reduced bacterial counts compared to wildtype control micethroughout the 21 day observation period. The caecum and here a specific immunologicstructure, the caecal patch (CP), are crucial anatomic sites where C. r. infection first accumu-lates within hours after p.o. infection followed by the spread of the bacteria anterogradethrough the colon over the next days. This implies that the CP might be a privileged nichethat is permissive for C. r. infection. Hence, we sought to test the hypothesis that the CPis involved in the diminished infection of Batf3-/- mice. Therefore we performed time courseexperiments comparing the bacterial burden at the CP in Batf3+/+ and Batf3-/- mice. 5hafter oral infection we did not detect any differences in bioluminescence between bothgroups. However, after 24h and especially after 72h Batf3+/+ mice showed significant higherbacterial counts at the CP compared to Batf3-/- mice. In summary, our data suggest a crucialrole of CD103+ DCs during the pathogenesis and establishment of the Citrobacter rodentiumcolitis and infection model. Further experiments are under way to further investigate thecontribution of CD103+ CD11b- DC to the relative protection of Batf3-/- mice after C.r. infection.
High Plasma Level of Lipopolisaccharyde and Anti-Flagellin Antibodies AmongPatients With Irritable Bowel Syndrome- Signs of Bacterial Translocation?Aldona Dlugosz, Piotr Nowak, Jessica Nystrm, Samir Abdurahman, Greger Lindberg
A role of immune activation in the pathophysiology of irritable bowel syndrome (IBS) issupported by a number of observations. Mediators released by immune cells impact on thefunction of enteric and sensory afferent nerves as well as on epithelial tight junctionscontrolling mucosal barrier in cell culture systems. Innate immune responses to conservedmicrobial products such as lipopolysaccharide (LPS) and flagellin are likely to be importantin the microbial-host interactions and intestinal homeostasis. We hypothesized that bacterialtranslocation and activation of mucosal immunity against common microbial antigens mightbe involved in the development of IBS. We therefore compared serum levels of LPS, CD14and flagellin antibodies between patients with different subtypes of IBS and healthy controls.Methods: We analyzed serum obtained from 91 patients (74 females) aged 19-(43)-73 yearsand 106 healthy volunteers (77 females) aged 19-(38)-62 years. Diarrhoea-predominant IBS(D-IBS) was present in 32 patients (35%), 22 patients (24%) had constipation-predominantIBS (C-IBS) and 37 patients (41%) had non-C-non-D IBS. We used ELISA for sCD14 andantibodies and limulus amebocyte assay (LAL) for LPS. Results: We found a significantlyhigher plasma level of LPS in patients with D-IBS compared to controls (p=0.0096). Thelevel of antibodies to flagellin was significantly higher among patients with IBS than amongcontrols (p=0.0003, mainly driven by higher levels in D-IBS). Since we used an in-houseanti-flagellin specific IgG ELISA we also determined the ratio Flagellin IgG/Total IgG.Obtained results confirmed the higher level of anti-flagellin antibodies among IBS patients(p=0.0014). The levels of soluble CD14 was lower among IBS-D patients compared tocontrols (p=0.0284). Conclusion: Our results support the concept that immune reactivityto luminal antigens may have a role in the development of IBS, especially in D-IBS.
Shigella Spp. Adversely Affect Paracellular Permeability in In Vitro and Ex-Vivo Models of Intestinal MucosaMaria R. Fiorentino, Karen M. Lammers, Marcelo Sztein, Alessio Fasano
Background: Shigellosis is a leading cause of diarrheal disease worldwide particularly indeveloping countries where it is estimated that 163 million cases with more than one milliondeaths occur annually. The pathogenesis of Shigella is based on the bacteria's ability to invadeand replicate within the colonic epithelium, which results in severe intestinal inflammatoryresponse and epithelial destruction. Aim: Because vaccines against shigellosis are urgentlyneeded, we are characterizing the pathogenic effects caused by wild type and potentialvaccine strains of Shigella flexneri and dysenteriae-1 in in vitro and ex-vivo models ofintestinal mucosa. Methods: To model the interactions of Shigella with the intestinal mucosa,we apically exposed monolayers of human colonic Caco2 cells and mouse jejeunum mucosato bacterial cultures. We monitored changes in paracellular permeability by measuring thetransepithelial electric resistance (TEER) and the passage of FITC-labeled molecules fromthe apical to the basolateral side. Additionally, we examined the pro-inflammatory responseof epithelial cells exposed to bacteria. Results: Inoculation of Shigella into human Caco2cell monolayers and murine mucosa mounted on snapwells, caused severe mucosal damage,which was apparent as a drastic reduction of the TEER, accompanied by a sharp increaseof paracellular passage of FITC-dextran (4kDa) through the epithelial layer. This decreasein epithelial permeability can be accounted for a breakdown of the tight junction integrity.Indeed, infected Caco2 cells showed the disruption of tight junction components at the cell-cell boundary and no adverse effect on cellular viability. Shigella infection of Caco2 cellsinduced the secretion of IL-8. The attenuated vaccine strains of Shigella (CVD1208S andCVD 1256) elicited a pro-inflammatory response with no damage of the intestinal barrierintegrity. Conclusions: Both the in vitro and ex-vivo systems are effective means to studythe interaction of Shigella with intestinal epithelial cells. Our experiments show that Shigellainterferes with the mucosal barrier function by disrupting the role of components of tightjunctions. In addition, the preliminary data with attenuated strains make them very attractiveas candidate vaccines.
Small Intestinal Microbiota of Colonic IBD Patients May Give Rise to anAltered Gut Microenvironment Enabling Selective Enrichment of BacterialPopulations: Implications of Microbiome Analysis on Ileal EffluentToru Kono, Mitsue Nishiyama,