Project description:Bacterial flagellin is a dominant innate immune activator of the intestine. Therefore, we examined the role of the intracellular flagellin receptor, NLRC4, in protecting the gut and/or driving inflammation. In accord with NLRC4 acting via transcription-independent pathways, loss of NLRC4 did not reduce the rapid robust changes in intestinal gene expression induced by flagellin administration. Loss of NLRC4 did not alter basal intestinal homeostasis nor predispose mice to development of colitis upon administration of an anti-IL-10R monoclonal antibody. However, in response to epithelial injury induced by dextran sulfate sodium (DSS), loss of NLRC4 resulted in more severe disease indicating a role for NLRC4 in protecting the gut. Moreover, loss of NLRC4 resulted in increased mortality in response to flagellate, but not aflagellate Salmonella infection. Thus, despite not being involved in rapid intestinal gene remodeling upon detection of flagellin, NLRC4-mediated inflammasome activation protects mice from mucosal and systemic challenges Flagellin (FliC) from WT Salmonella enterica serovar Typhimurium (SL3201, fljB–) was purified through sequential cation and anion-exchange chromatography and purity was verified as previously described 4. WT, T5KO, N4KO and T5/N4-DKO mice (n=6) were given either 0.2 mL PBS or flagellin (10μg/mouse in 0.2 mL PBS) intraperitoneally. After 1h, mice were euthanized and colon was taken and stored in RNAlater (Invitrogen) for 1 day. Total mRNA was isolated from colonic tissues using TRIzol (Invitrogen) and purified using the RNeasy® Plus Mini kit (Qiagen) according to the manufacturer’s instructions
Project description:Bacterial flagellin is a dominant innate immune activator of the intestine. Therefore, we examined the role of the intracellular flagellin receptor, NLRC4, in protecting the gut and/or driving inflammation. In accord with NLRC4 acting via transcription-independent pathways, loss of NLRC4 did not reduce the rapid robust changes in intestinal gene expression induced by flagellin administration. Loss of NLRC4 did not alter basal intestinal homeostasis nor predispose mice to development of colitis upon administration of an anti-IL-10R monoclonal antibody. However, in response to epithelial injury induced by dextran sulfate sodium (DSS), loss of NLRC4 resulted in more severe disease indicating a role for NLRC4 in protecting the gut. Moreover, loss of NLRC4 resulted in increased mortality in response to flagellate, but not aflagellate Salmonella infection. Thus, despite not being involved in rapid intestinal gene remodeling upon detection of flagellin, NLRC4-mediated inflammasome activation protects mice from mucosal and systemic challenges
Project description:Activators of innate immunity may have potential to combat a broad range of infectious agents. We report that treatment with bacterial flagellin prevented rotavirus (RV) infection in mice and cured chronically RV-infected mice. Protection was independent of adaptive immunity and interferon (IFN, type I and II) and required flagellin receptors Toll-like receptor 5 (TLR5) and NOD-like receptor C4 (NLRC4). Flagellin-induced activation of TLR5 on dendritic cells elicited production of the cytokine interleukin (IL)-22, which induced a protective gene expression program in intestinal epithelial cells. Flagellin also induced NLRC4-dependent production of IL-18 and immediate elimination of RV-infected cells. Administration of IL-22 and IL-18 to mice fully recapitulated the capacity of flagellin to prevent or eliminate RV infection, and thus holds promise as a broad-spectrum antiviral agent.
Project description:Inflammasome activation is critical for host defense against various microbial infections. Activation of the NLRC4 inflammasome requires detection of flagellin or type III secretion system (T3SS) components by NLR family apoptosis inhibitory proteins (NAIPs); yet how this pathway is regulated is unknown. Here we found that interferon regulatory factor 8 (IRF8) is required for optimal activation of the NLRC4 inflammasome in bone marrow-derived macrophages infected with Salmonella Typhimurium, Burkholderia thailandensis, or Pseudomonas aeruginosa but is dispensable for activation of the canonical and non-canonical NLRP3, AIM2, and Pyrin inflammasomes. IRF8 governs the transcription of Naips to allow detection of flagellin or T3SS proteins to mediate NLRC4 inflammasome activation. Furthermore, we found that IRF8 confers protection against bacterial infection in vivo, owing to its role in inflammasome-dependent cytokine production and pyroptosis. Altogether, our findings suggest that IRF8 is a critical regulator of NAIPs and NLRC4 inflammasome activation for defense against bacterial infection.
Project description:We previously showed that pre-exposure of the cornea to TLR5 ligand flagellin induces profound mucosal innate protection against pathogenic microbes by reprogramming gene expression. To date, there was no genome-wide cDNA array to detect full scale of flagellin mediated reprogramming of gene expression in mucosal surface epithelial cells. Taking advantage of readily accessible, easily procurable epithelial cell population, this study is the first report to use genome-wide cDNA microarray approach to document genes associated with flagellin-induced protection against Pseudomonas aeruginosa infection in corneal epithelial cells (CECs).
Project description:We previously showed that pre-exposure of the cornea to TLR5 ligand flagellin induces profound mucosal innate protection against pathogenic microbes by reprogramming gene expression. To date, there was no genome-wide cDNA array to detect full scale of flagellin mediated reprogramming of gene expression in mucosal surface epithelial cells. Taking advantage of readily accessible, easily procurable epithelial cell population, this study is the first report to use genome-wide cDNA microarray approach to document genes associated with flagellin-induced protection against Pseudomonas aeruginosa infection in corneal epithelial cells (CECs). Total RNA obtained from isolated mouse corneal epithelial cells of the control (cells scrapped off from the corneas without infection), Pseudomonas aeruginosa infected (6 h post infection) and flagellin pretreated (24 h), followed by Pseudomonas aeruginosa infection (6 h).
Project description:Macrophages are an important component of the innate immune system. Flagellin has been extensively studied for its adjuvant activity owing to its TLR5 and NLRC4 binding sites. However, few studies have comprehensively investigated the effects of flagellin in macrophages using transcriptome sequencing. In this study, RNA sequencing (RNA-seq) was used to analyze the expression patterns of RAW264.7 cells induced by flagellin (FliC) of Salmonella typhimurium compared with unstimulated cells, to identify novel transcriptomic signatures in macrophages.
Project description:The study aimed at defining the local and systemic innate responses after intradermal injection of flagellin. For this purpose, mice were immunized by intradermal route with flagellin. Skin and blood were then sampled at selected times for microarray analyses.
Project description:The activity of the potent nasal adjuvant flagellin depends on initial activation of airway epithelilal cells. This study aims at investigating the immune cells involved in the antigen presentation within the respiratory tract. First, microarrays characterized that activation/recruitment of immune cells was the main signature of flagellin activation in lung. Neutrophils and classical monocytes were strongly recruited into the lungs and take up antigen upon nasal administration of flagellin. In contrast, the numbers of lung CD11b+ or CD103+ DC and alveolar macrophages were not enhanced although these cells were very efficient in antigen uptake. Our experiments showed that CD11b+ DC but not monocytes, PMN, CD103+ DC are not essential for the adjuvant effect. Flagellin signaling enhanced the functional activation of lung CD11b+ conventional DC and their migration to the lymph nodes. Using Cd11c-DTR mice, CD11b+ DC from lymph nodes were identified as the major stimulators of CD4 T cell activation. Finally, the migration and maturation of mucosal DC was independent of direct signaling, highlighting the contribution of epithelial factors in the mucosal adjuvant effect of flagellin. In conclusion, these data demonstrate that adjuvant activity can be dissociated from inflammatory cell recruitment an open new perpectives for improvement of vaccines. Female C57BL/6J (6 weeks old) mice were immunized with the TLR5 agonist Flagellin (1μg diluted in PBS) by intranasal (i.n.) administration. Blood samples of four time points post immunization were taken at 2h, 4h, 18h and 48h. Microarray experiments were performed as single-color hybridizations.
Project description:The study aimed at defining the local and systemic innate responses after intradermal injection of flagellin. For this purpose, mice were immunized by intradermal route with flagellin. Skin and blood were then sampled at selected times for microarray analyses. Mice were then immunized with the TLR5 agonist flagellin by intradermal route. Blood samples and punch biopsies of skin were sampled post-immunization and on mock animals. Total RNA was extracted and microarray experiments were performed as single-color hybridizations on Agilent 4x44K mouse whole genome catalog arrays (Agilent-014868) according supplier's recommendations.