Die zelluläre Initiation der Typ I Interferon Antwort in vivo
Final Report Abstract
Type I interferons, consisting mainly of multiple IFNα subtypes and a single IFNβ, are central molecular components of early anti-infectious immune responses. Due to a lack of sufficiently sensitive assay systems the cell types responsible for the production of these effector cytokines in many situations still remain ill defined. To identify the cellular expression pattern of IFNβ and the underlying regulatory mechanisms in distinct stimulation and infection conditions we employed the IFNβmob/mob knock-in reporter mouse (mob: messenger of IFN beta) in which YFP is expressed from a bicistronic mRNA linked by an internal ribosomal entry site to the endogenous IFNβ mRNA. As in general IFNβ is the first type I interferon to be produced this allows for a direct monitoring of the initiation of the type I IFN response in vivo. The Emmy Noether research group established the IFNβmob/mob mouse as a valuable in vivo analysis tool which was used in the second and third funding period for mechanistic analyses of the functional role of IFN type I and IFNβ-producing effector cells in complex in vivo disease models. The IFNβmob/mob knock-in reporter mouse is now widely used in national and international collaborations within the scientific immunology and molecular biology community. A focus of our efforts was placed on transcriptome analyses of sorted effector cells from IFNβmob/mob mice. Comparison of identical pDCs subpopulations differing only in IFNβ expression revealed that more than 1,500 genes were differentially expressed between IFNβ-producing and non-producing pDCs. IFNβ/YFP+ pDCs exhibited a higher expression of several genes involved in immune modulation, e.g. interleukins and chemokines, and this was independent of IFNAR-mediated signalling. Thus IFNβ expression defines a subpopulation of pDCs, which is unique not only with regard to their expression of IFNβ, but also differs in the expression of other immune-relevant factors from pDCs not producing IFNβ. IFNβ-producing pDCs might, therefore, fulfill specialized functions in secondary lymphoid organs e.g. activation of NKT cells and modulation of CD4+ T cells. In MCMV infection we identified CD8α+ pDCs as the exclusive producers of IFNβ which were not productively infected. Here we showed in vivo that not only cDCs but also CD8- pDCs harbour MCMV within the first 24 h of infection. This led to the hypothesis that pDCs in an early maturation state can be infected leading to a transdifferentiation into CD8α+ cDC like cells highly active in cross-presentation. More mature pDCs coming in contact with the virus, however, efficiently block virus replication early on and initiate the type I IFN response. For the visualization of IFNβ, the most widely used treatment in multiple sclerosis, in autoimmunity we defined in the MOG peptide induced EAE model activated microglia as major endogenous producers of the protective IFNβ at the peak of EAE. In cerebellar organotypic slice cultures (OSCs) this phenotype of IFNβ producing cells in the CNS could be confirmed after poly(I:C) treatment. Further, poly(I:C) stimulation induces IFNβ production in microglia, which promotes phagocytosis of myelin debris. Also, altered myelin debris accumulation could be observed in OSCs from IFNβ deficient animals after spontaneous demyelination. This study defines an up to now unknown function of IFNβ in enhancing phagocytosis and possibly neuronal regeneration during EAE. To analyze the coregulatory mechanisms between IFNβ and IL-12p40 expression in a clinically relevant setting we used the well-established bacterial sepsis model of colon ascendens stent peritonitis (CASP) in the context of a preceding viral infection mimicked by poly(I:C). Here we showed that specifically IFNβ contributes to mortality in the early phase of polymicrobial peritonitis after prestimulation with viral molecular compounds. Using a double knockin reporter mouse model for IFNβ and IL-12p40, we defined for the first time in a sepsis model that cDCs are the major source of the detrimental IFNβ as well as the protective IL-12p40. These cDCs exhibited stabilized expression of both cytokines after viral prestimulation and show an inability to adapt appropriately to a secondary bacterial infection. This lack of cytokine plasticity in activated cDCs reveals a novel mechanism contributing to a dysregulated cytokine response and the development of septic shock. The findings established in the first funding period have already lead to the identification of specialized IFNβ producing effector cell types in different infection and autoimmune pathologies. With results generated in the second and third funding period a more detailed knowledge of the cellular interaction partners and the molecular control mechanisms of the initiation of the type I IFN response was achieved. This can contribute significantly to the optimized development of novel vaccination and therapeutic approaches.
Publications
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2008. Transcription factor E2-2 is an essential and specific regulator of plasmacytoid dendritic cell development. Cell 135:37-48
Cisse, B., M.L. Caton, M. Lehner, T. Maeda, S. Scheu, R. Locksley, D. Holmberg, C. Zweier, N.S. den Hollander, S.G. Kant, W. Holter, A. Rauch, Y. Zhuang, and B. Reizis
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2008. Visualization of IFNbeta production by plasmacytoid versus conventional dendritic cells under specific stimulation conditions in vivo. Proc Natl Acad Sci USA 105:20416-20421
Scheu, S., P. Dresing, and R.M. Locksley
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2010. A fluorescence reporter model defines "TipDCs" as the cellular source of interferon beta in murine Listeriosis. PLoS ONE 5:e15567
Dresing, P., S. Borkens, M. Kocur, S. Kropp, and S. Scheu
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2010. Tissue macrophages suppress viral replication and prevent severe immunopathology in an interferon-I-dependent manner in mice. Hepatology 52:25-32
Lang, P.A., M. Recher, N. Honke, S. Scheu, S. Borkens, N. Gailus, C. Krings, A. Meryk, A. Kulawik, L. Cervantes-Barragan, N. Van Rooijen, U. Kalinke, B. Ludewig, H. Hengartner, N. Harris, D. Häussinger, P.S. Ohashi, R.M. Zinkernagel, and K.S. Lang
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2012. CC chemokine receptor 4 is required for experimental autoimmune encephalomyelitis by regulating GM-CSF and IL-23 production in dendritic cells. Proc Natl Acad Sci USA 109:3897-902
Poppensieker K., D.M. Otte, B. Schürmann, A. Limmer, P. Dresing, E. Drews, B. Schumak, L. Klotz, J. Raasch, A. Mildner, A. Waisman, S. Scheu, P. Knolle, I. Förster, M. Prinz, W. Maier, A. Zimmer, and J. Alferink
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2012. Stochastic Expression of the Interferon-β gene. PLOS Biol 10:e1001249
Zhao M., J. Zhang, H. Phatnani, S. Scheu, T Maniatis
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2013. Reduced tape I interferon production by dendritic cells and weakened antiviral immunity in patients with Wiskott-Aldrich syndrome protein deficiency. J Allergy Clin Immunol 131:815-824
Lang P.A., N. Shaabani, S. Borkens, N. Honke, S. Scheu, S. Booth, D. Brenner, A. Meryk, C. Barthuber, M. Recher, T.W. Mak, P.S. Ohashi, D. Häussinger, G.M. Griffiths, A.J. Thrasher, G. Bouma, and K.S. Lang
