Project description:The host genotype has been proposed to contribute to individually composed bacterial communities in the gut. To provide deeper insight into interactions between gut bacteria and their host, we associated germ-free C3H and C57BL/10 mice with intestinal bacteria from a C57BL/10 donor mouse. Analysis of microbiota similarity between the experimental animals with denaturing gradient gel electrophoresis (DGGE) 13 weeks after association revealed the development of a mouse strain specific microbiota. Gene expression in the colonic mucosa was analyzed with a microarray approach taking advantage of a modified Affymetrix mouse genome chip. We detected 202 genes whose expression differed significantly by a factor of < 2. Application of bioinformatics tools demonstrated that functional terms including signaling/secretion, lipid degradation/catabolism, guanine nucleotide/guanylate binding and immune response were significantly enriched in differentially expressed genes. We had a closer look at the 56 genes with expression differences of < 4 and observed a higher expression in C57BL/10 mice of the genes coding for toll-like receptor 1 (4-fold) and angiogenin 4 (33-fold) which are involved in the recognition and response to gut bacteria. In contrast, a 70-fold higher expression of the phospholipase A2, group IIA-encoding gene (Pla2g2a) was detected in C3H mice. In addition, a number of interferon-inducible genes were higher expressed in C3H than in C57BL/10 mice including Gbp1 (18-fold), Mal (7-fold), Oasl2 (7-fold), Ifi202b (7-fold), Rtp4 (6-fold), Ly6g6c (5-fold), Ifi27l2a (5-fold), Usp18 (5-fold), Ifit1 (5-fold), Ifi44 (4-fold), and Ly6g (4-fold) indicating that these cytokines play an essential role in microbiota regulation. However, genes coding for interferons, their receptors or factors involved in interferon signaling pathways were not differentially expressed between the two mouse strains. Taken together, our study confirms that the host genotype is involved in the establishment of host-specific bacterial communities in the gut. Based on expression differences after colonization with the same bacterial inoculum, we propose that Pla2g2a and interferon-dependent genes may contribute to this phenomenon. Total RNA was extracted from the colonic mucosa and hybridization was performed using 12.5M-BM- M-bM-^@M-^SM-BM- 20M-BM- M-BM-5g of cDNA on a customized Affymetrix nugomm 1a520177 chip.

Project description:Background: It has been shown that intracellular pathogens hijack DC functions to evade immune defense mechanisms. In this study, we investigated the responses of human monocyte derived DCs to four intracellular bacteria, Tropheryma whipplei, Coxiella burnetii, Brucella abortus and Orientia tsutsugamushi, responsible for human infectious diseases and known to infect myeloid cells. Methods: Whole genome microarrays were assessed to define common and specific transcriptionnal responses to bacterial pathogen. Bacterial pathogen ability to affect DC maturation was assessed by measuring lymphoproliferation and endocytosis as well as phenotypic maturation markers (CD80, CD83, CD86 and HLA-DR) expression. Results: We found that Coxiella burnetii, Orientia tsutsugamushi and Brucella abortus induced DC maturation assessed through decreased endocytosis ability, triggering lymphoproliferation, surface expression of HLA class II molecules and phenotypic changes, whereas Tropheryma whipplei did not induce DC maturation. As revealed by microarray analysis, the response of DCs to these bacteria consisted of a core associated with the maturation of DCs and signatures specific for each pathogen. The core response represented 10% of genes modulated in response to pathogens and consisted of general cellular processes including nucleotide binding, protein transport, cell fraction, protein kinase, cell cycle, mitochondrial membrane and cytoskeleton. The specific transcriptional signature induced by C. burnetii is associated with the communication between innate and adaptive immune cells and DC maturation. B. abortus signature specifically involved arachidonic acid and lipooxygenase pathways and O. tsutsugamushi signature involved type I and type III IFN responses. Conclusion: This study demonstrates that intracellular bacteria use multifaceted pathways to induce DC maturation which may lead to unadapted immune response. The understanding of these pathways may be useful to improve our knowledge of bacterial recognition by the immune system but also intracellular bacterial diseases.

Project description:The host genotype has been proposed to contribute to individually composed bacterial communities in the gut. To provide deeper insight into interactions between gut bacteria and their host, we associated germ-free C3H and C57BL/10 mice with intestinal bacteria from a C57BL/10 donor mouse. Analysis of microbiota similarity between the experimental animals with denaturing gradient gel electrophoresis (DGGE) 13 weeks after association revealed the development of a mouse strain specific microbiota. Gene expression in the colonic mucosa was analyzed with a microarray approach taking advantage of a modified Affymetrix mouse genome chip. We detected 202 genes whose expression differed significantly by a factor of < 2. Application of bioinformatics tools demonstrated that functional terms including signaling/secretion, lipid degradation/catabolism, guanine nucleotide/guanylate binding and immune response were significantly enriched in differentially expressed genes. We had a closer look at the 56 genes with expression differences of < 4 and observed a higher expression in C57BL/10 mice of the genes coding for toll-like receptor 1 (4-fold) and angiogenin 4 (33-fold) which are involved in the recognition and response to gut bacteria. In contrast, a 70-fold higher expression of the phospholipase A2, group IIA-encoding gene (Pla2g2a) was detected in C3H mice. In addition, a number of interferon-inducible genes were higher expressed in C3H than in C57BL/10 mice including Gbp1 (18-fold), Mal (7-fold), Oasl2 (7-fold), Ifi202b (7-fold), Rtp4 (6-fold), Ly6g6c (5-fold), Ifi27l2a (5-fold), Usp18 (5-fold), Ifit1 (5-fold), Ifi44 (4-fold), and Ly6g (4-fold) indicating that these cytokines play an essential role in microbiota regulation. However, genes coding for interferons, their receptors or factors involved in interferon signaling pathways were not differentially expressed between the two mouse strains. Taken together, our study confirms that the host genotype is involved in the establishment of host-specific bacterial communities in the gut. Based on expression differences after colonization with the same bacterial inoculum, we propose that Pla2g2a and interferon-dependent genes may contribute to this phenomenon.

Project description:Background: It has been shown that intracellular pathogens hijack DC functions to evade immune defense mechanisms. In this study, we investigated the responses of human monocyte derived DCs to four intracellular bacteria, Tropheryma whipplei, Coxiella burnetii, Brucella abortus and Orientia tsutsugamushi, responsible for human infectious diseases and known to infect myeloid cells. Methods: Whole genome microarrays were assessed to define common and specific transcriptionnal responses to bacterial pathogen. Bacterial pathogen ability to affect DC maturation was assessed by measuring lymphoproliferation and endocytosis as well as phenotypic maturation markers (CD80, CD83, CD86 and HLA-DR) expression. Results: We found that Coxiella burnetii, Orientia tsutsugamushi and Brucella abortus induced DC maturation assessed through decreased endocytosis ability, triggering lymphoproliferation, surface expression of HLA class II molecules and phenotypic changes, whereas Tropheryma whipplei did not induce DC maturation. As revealed by microarray analysis, the response of DCs to these bacteria consisted of a core associated with the maturation of DCs and signatures specific for each pathogen. The core response represented 10% of genes modulated in response to pathogens and consisted of general cellular processes including nucleotide binding, protein transport, cell fraction, protein kinase, cell cycle, mitochondrial membrane and cytoskeleton. The specific transcriptional signature induced by C. burnetii is associated with the communication between innate and adaptive immune cells and DC maturation. B. abortus signature specifically involved arachidonic acid and lipooxygenase pathways and O. tsutsugamushi signature involved type I and type III IFN responses. Conclusion: This study demonstrates that intracellular bacteria use multifaceted pathways to induce DC maturation which may lead to unadapted immune response. The understanding of these pathways may be useful to improve our knowledge of bacterial recognition by the immune system but also intracellular bacterial diseases. IL4/GM-CSF monocyte-derived dendritic cells were stimulated by T. whipplei, B. abortus, C. burnetii, O. tsutsugamushi and LPS during 6 hours. Common and specific signatures were determined by comparison with uninfected DCs. moDCs (5.10^6) were plated in 6 well plates and stimulated with bacteria or LPS for 6 hours, and total RNA was extracted using the RNeasy minikit (Qiagen, adresse CA) and DNase treatment. The Agilent-014850 4X44k Human Whole Genome microarrays (Agilent Technologies, CA) representing 44,000 probes were used as recently described. Reverse transcription, sample labeling and hybridization were performed according to protocols specified by the manufacturer (One-Color Microarray-Based Gene Expression Analysis). Three samples per experimental condition were included in the analysis.

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