Project description:Genes and pathways in which inactivation dampens tissue inflammation present new opportunities for understanding the pathogenesis of common human inflammatory diseases, including inflammatory bowel disease, rheumatoid arthritis and multiple sclerosis. We identified a mutation in the gene encoding the deubiquitination enzyme USP15 (Usp15L749R) that protected mice against both experimental cerebral malaria (ECM) induced by Plasmodium berghei and experimental autoimmune encephalomyelitis (EAE). Combining immunophenotyping and RNA sequencing in brain (ECM) and spinal cord (EAE) revealed that Usp15L749R-associated resistance to neuroinflammation was linked to dampened type I interferon responses in situ. In hematopoietic cells and in resident brain cells, USP15 was coexpressed with, and functionally acted together with the E3 ubiquitin ligase TRIM25 to positively regulate type I interferon responses and to promote pathogenesis during neuroinflammation. The USP15-TRIM25 dyad might be a potential target for intervention in acute or chronic states of neuroinflammation.
Project description:Japanese encephalitis virus (JEV) is a causative agent of encephalitis, mostly prevalent in Asia and South-Asian countries. Neuroinflammation is the hallmark of encephalitis, mediated in parts through the activation of brain-resident microglial cell, thus playing a critical role in determining pathogenesis. Deregulated activity of microglia can be lethal for the brain tissue. Interferon Regulatory Factor 8 (Irf8) mediates differentiation and transformation of microglia to reactive phenotypes and also regulates antiviral response through cross-talk with interferon pathway. In this study, we have conducted a comparative study between JEV infected C57BL/6 wild type and Irf8 Knockout (IRF8-/-) to identify the genes directly or indirectly regulated by IRF8.
Project description:Although mast cells elicit proinflammatory and type I IFN responses upon VSV infection, in response to L.monocytogenes (L.m) or S. Typhimurium (S.t), such cells elicit a transcriptional program devoid of type I IFN response. Balanced induction of proinflamatory and type I interferon (IFN) responses upon activation of Toll like receptors (TLRs) determines the outcome of microbial infections and the pathogenesis of autoimmune and other inflammatory diseases. Mast cells, key components of the innate immune system, are known for their debilitating role in allergy and autoimmune syndromes. However, their potential role in anti-microbial host defenses is increasingly being acknowledged. How mast cells interact with microbes and the nature of responses triggered thereof is not well characterized. Here we show that in response to TLR activation by Gram-positive and negative bacteria or their components like LPS, unlike macrophages, mast cells elicit pro-inflammatory but not type I IFN responses. We demonstrate that in mast cells, the bound bacteria and TLR ligands remain trapped at the cell surface and do not undergo internalization - a prerequisite for type I IFN induction. Such cells could, however, elicit type I IFNs in response to vesicular stomatitis virus (VSV), which accesses the cytosolic RIG-I receptor. Although important for anti-viral immunity, a strong type I IFN response is known to contribute to pathogenesis during bacterial infection. Thus, while endowed with the capacity to elicit type I IFNs in response to viral infection, the fact that mast cells only elicit pro-inflammatory responses upon bacterial infection illustrates that mast cells, key effector cells of the innate immune system, are well adjusted for optimal anti-bacterial and anti-viral responses. Wild type control (cntr) or interferon receptor (IFNAR)-deficient mast cells (MC) or macrophages (MAC) were infected with L.m. and S.t. (MOIs 50 and 5 for MC and MAC, respectively). MC and MAC were exposed to VSV-AV2 (MOI: 2). Samples were analyzed after 6 hours. Uninfected/unstimulated cells were used as reference samples for calculating fold change in gene expression. Gene Expression levels were determined by the Affymetrix MOE 430 2.0 GeneChips. Signal Intensities were calculated using the RMA algorithm and for statistical analysis we applied GeneSpring GX 10 software suite (Agilent Technologies, Waldbronn, Germany). MultiExperiment Viewer (MEV) software version 4.4 of the Institute for Genomic Research was used for clustering algorithm data analysis and visualization.
Project description:Type I interferons are critical anti-viral cytokines during virus infections and have also been implicated in the pathogenesis of systemic lupus erythematosus (SLE). The secretion of type I interferon of pDCs is modulated by Siglec-H, a DAP12 associated receptor on pDCs. We showed that Siglec-H deficient pDCs produce more of the type I interferon IFN-α in vitro and that Siglec-H ko mice produce more IFN-α after murine cytomegalovirus (mCMV) infection in vivo, leading to efficient clearance of the virus. Furthermore, ageing Siglec-H ko mice showed a mild form of systemic autoimmunity. In contrast, Siglec-H ko mice developed a severe form of systemic lupus-like autoimmune disease with strong kidney nephritis several weeks after a single mCMV infection. This induction of systemic autoimmune disease after virus infection in Siglec-H ko mice was accompanied by a type I interferon signature and fully dependent on type I interferon signaling. These results show that Siglec-H normally serves as modulator of type I interferon responses after infection with a persistent virus and thereby prevents induction of autoimmune disease. For microarray experiments gene expression profiles of total splenic cells from two wt and Siglec-H ko mice 26 weeks after infection with luciferase expressing murine Cytomegalovirus (5x105 pfu) or from two uninfected wt and Siglec-H ko control mice were analyzed
Project description:Although mast cells elicit proinflammatory and type I IFN responses upon VSV infection, in response to L.monocytogenes (L.m) or S. Typhimurium (S.t), such cells elicit a transcriptional program devoid of type I IFN response. Balanced induction of proinflamatory and type I interferon (IFN) responses upon activation of Toll like receptors (TLRs) determines the outcome of microbial infections and the pathogenesis of autoimmune and other inflammatory diseases. Mast cells, key components of the innate immune system, are known for their debilitating role in allergy and autoimmune syndromes. However, their potential role in anti-microbial host defenses is increasingly being acknowledged. How mast cells interact with microbes and the nature of responses triggered thereof is not well characterized. Here we show that in response to TLR activation by Gram-positive and negative bacteria or their components like LPS, unlike macrophages, mast cells elicit pro-inflammatory but not type I IFN responses. We demonstrate that in mast cells, the bound bacteria and TLR ligands remain trapped at the cell surface and do not undergo internalization - a prerequisite for type I IFN induction. Such cells could, however, elicit type I IFNs in response to vesicular stomatitis virus (VSV), which accesses the cytosolic RIG-I receptor. Although important for anti-viral immunity, a strong type I IFN response is known to contribute to pathogenesis during bacterial infection. Thus, while endowed with the capacity to elicit type I IFNs in response to viral infection, the fact that mast cells only elicit pro-inflammatory responses upon bacterial infection illustrates that mast cells, key effector cells of the innate immune system, are well adjusted for optimal anti-bacterial and anti-viral responses.
Project description:Type I interferons are critical anti-viral cytokines during virus infections and have also been implicated in the pathogenesis of systemic lupus erythematosus (SLE). The secretion of type I interferon of pDCs is modulated by Siglec-H, a DAP12 associated receptor on pDCs. We showed that Siglec-H deficient pDCs produce more of the type I interferon IFN-α in vitro and that Siglec-H ko mice produce more IFN-α after murine cytomegalovirus (mCMV) infection in vivo, leading to efficient clearance of the virus. Furthermore, ageing Siglec-H ko mice showed a mild form of systemic autoimmunity. In contrast, Siglec-H ko mice developed a severe form of systemic lupus-like autoimmune disease with strong kidney nephritis several weeks after a single mCMV infection. This induction of systemic autoimmune disease after virus infection in Siglec-H ko mice was accompanied by a type I interferon signature and fully dependent on type I interferon signaling. These results show that Siglec-H normally serves as modulator of type I interferon responses after infection with a persistent virus and thereby prevents induction of autoimmune disease.
Project description:Adjuvants are critical for the success of vaccines, and agonists for microbial pattern recognition receptors are promising new candidates. A mechanism for the immune enhancing role of adjuvants is to stimulate innate immunity. We studied the innate immune response in humans to synthetic double stranded RNA (poly ICLC), a ligand for TLR3 and MDA-5 cytosolic RNA helicase. Transcriptional analysis of blood samples from eight volunteers, after subcutaneous administration of poly ICLC showed upregulation of genes involved in multiple innate immune pathways in all subjects, including interferon and inflammasome signaling. Blocking of type I interferon receptor ex vivo significantly dampened the response to poly IC. Comparative transcriptional analysis showed that several innate pathways were similarly induced in volunteers immunized with the highly efficacious Yellow Fever Vaccine. Therefore a chemically defined microbial agonist like poly ICLC can be a reliable and authentic microbial mimic for inducing innate immunity, here for a live attenuated viral vaccine in humans. GSM813292-GSM813386: RNA expression obtained at different time points from Human blood after poly ICLC administration compared to RNA expression obtained from Human blood after placebo administration GSM813387-GSM813410: Blocking of type I interferon receptor ex vivo followed by poly IC stimulation
Project description:The CCDC88B gene (11q13) is a risk factor for several chronic inflammatory diseases in humans, including inflammatory bowel disease (IBD), multiple sclerosis and psoriasis. A Ccdc88b mutation in mice conveys protection against pathological inflammation in experimental models of microbial (cerebral malaria) and autoimmune (experimental autoimmune encephalomyelitis) of neuroinflammation and colitis. At the cellular level, loss of Ccdc88b function is phenotypically expressed as a migratory defect in vivo, and a cell mobility defect in vitro in mutant dendritic cells and lymphocytes. At the molecular level, CCDC88B belongs to a family of protein scaffold associated with the cytoskeleton and that feature protein:protein interactions domains. We used a co-immunoprecipitation / mass spectrometry-based approach to identify physical interactions of CCDC88B from mouse thymocytes and BI-141 cells.
Project description:STAT5 plays a critical role in mediating cellular responses following cytokine stimulation. The activated STAT5 proteins can form dimers and tetramers with distinct biological functions. The role of STAT5 tetramerization in autoimmune-mediated neuroinflammation has not been investigated. Using the STAT5 tetramer-deficient Stat5a-Stat5b N-domain double knock-in (DKI) mouse strain, we report here that STAT5 tetramers promote the pathogenesis of experimental autoimmune encephalomyelitis (EAE). The mild EAE phenotype observed in DKI mice correlates with the impaired extravasation of pathogenic Th17 cells and interactions between Th17 cells and monocyte-derived cells (MDCs) in the meninges. We further demonstrated that STAT5 tetramerization regulates the GM-CSF-dependent production of CCL17 by MDCs. Importantly, DKI Th17 cells expanded with CCL17 exhibit more severe EAE. Mechanistically, the effect of CCL17 is dependent on the activity of the integrin VLA-4. Thus, our study uncovered a novel GM-CSF-STAT5 tetramer-CCL17 pathway that promotes autoimmune neuroinflammation via the regulation of Th17 cell migration.
Project description:Polymorphisms in the transcription factor interferon regulatory factor 5 (IRF5) are strongly associated in human genetic studies with an increased risk of developing the autoimmune disease systemic lupus erythematosus. However, the biological role of IRF5 in lupus pathogenesis, if any, is not known. In this study we show that IRF5 is absolutely required for disease development in the FcgRIIB-/-Yaa and FcgRIIB-/- lupus models. In contrast to IRF5-sufficient FcgRIIB-/-Yaa mice, IRF5-deficient FcgRIIB-/-Yaa mice do not develop lupus manifestations and have a phenotype comparable to wildtype mice. Strikingly, full expression of IRF5 is required for the development of autoimmunity, as IRF5-heterozygotes had dramatically reduced disease. One effect of IRF5 is to induce the production of the type I interferon IFN-gamma, a cytokine implicated in lupus pathogenesis. To address the mechanism by which IRF5 promotes disease, we evaluated FcgRIIB-/-Yaa mice lacking the type I interferon receptor IFNAR1. Unlike the IRF5-deficient and IRF5-heterozygous FcgRIIB-/-Yaa mice, IFNAR1-deficient FcgRIIB-/-Yaa mice maintained a substantial level of residual disease. Furthermore, in FcgRIIB-/- mice lacking Yaa, IRF5-deficiency also markedly reduced disease manifestations, indicating that the beneficial effects of IRF5 deficiency in FcgRIIB-/-Yaa mice are not due only to inhibition of the enhanced TLR7 signaling associated with the Yaa mutation. Overall, we demonstrate that IRF5 plays an essential role in lupus pathogenesis in murine models and that this is mediated through pathways beyond that of type I interferon production. The fact that even IRF5 heterozygous mice developed minimal disease makes IRF5 a particularly attractive therapeutic target. Serum samples from a total of 70 mice were run on the Utz Lab Whole Protein Autoantigen Array V1.0 (a single-color platform) in order to profile their autoantibodies against a library of autoimmune antigens. All samples were run once with no replicates. The samples consisted of the following groups: For data appearing in Figure 3D, illustrating that mice lacking IRF5 have their autoantibody levels significantly affected: R2Yaa IRF5+/+: 12 R2Yaa IRF5+/-: 11 R2Yaa IRF5-/-: 14 C57BL/6 ("WT" control): 13 Total mice (arrays) for this group: 50 For data appearing in Figure 6D, illustrating that mice lacking Ifnar1 do not have their autoantibody levels significantly affected: R2Yaa Ifnar+/+: 10 R2Yaa Ifnar-/-: 10 Total mice (arrays) for this group: 20