Publications by authors named "Tobias Junt"

53 Publications

Two distinct immunopathological profiles in autopsy lungs of COVID-19.

Nat Commun 2020 10 8;11(1):5086. Epub 2020 Oct 8.

Institute of Pathology, Cantonal Hospital Baselland, Liestal, Switzerland.

Coronavirus Disease 19 (COVID-19) is a respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has grown to a worldwide pandemic with substantial mortality. Immune mediated damage has been proposed as a pathogenic factor, but immune responses in lungs of COVID-19 patients remain poorly characterized. Here we show transcriptomic, histologic and cellular profiles of post mortem COVID-19 (n = 34 tissues from 16 patients) and normal lung tissues (n = 9 tissues from 6 patients). Two distinct immunopathological reaction patterns of lethal COVID-19 are identified. One pattern shows high local expression of interferon stimulated genes (ISG) and cytokines, high viral loads and limited pulmonary damage, the other pattern shows severely damaged lungs, low ISGs (ISG), low viral loads and abundant infiltrating activated CD8 T cells and macrophages. ISG patients die significantly earlier after hospitalization than ISG patients. Our study may point to distinct stages of progression of COVID-19 lung disease and highlights the need for peripheral blood biomarkers that inform about patient lung status and guide treatment.
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http://dx.doi.org/10.1038/s41467-020-18854-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7546638PMC
October 2020

Target-Based Identification and Optimization of 5-Indazol-5-yl Pyridones as Toll-like Receptor 7 and 8 Antagonists Using a Biochemical TLR8 Antagonist Competition Assay.

J Med Chem 2020 08 30;63(15):8276-8295. Epub 2020 Jul 30.

Genomics Institute of the Novartis Research Foundation, San Diego, California 92121, United States.

Inappropriate activation of endosomal TLR7 and TLR8 occurs in several autoimmune diseases, in particular systemic lupus erythematosus (SLE). Herein, the development of a TLR8 antagonist competition assay and its application for hit generation of dual TLR7/8 antagonists are reported. The structure-guided optimization of the pyridone hit using this biochemical assay in combination with cellular and TLR8 cocrystal structural data resulted in the identification of a highly potent and selective TLR7/8 antagonist () with efficacy. The two key steps for optimization were (i) a core morph guided by a TLR7 sequence alignment to achieve a dual TLR7/8 antagonism profile and (ii) introduction of a fluorine in the piperidine ring to reduce its basicity, resulting in attractive oral pharmacokinetic (PK) properties and improved TLR8 binding affinity.
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http://dx.doi.org/10.1021/acs.jmedchem.0c00130DOI Listing
August 2020

Discovery of potent, orally bioavailable in vivo efficacious antagonists of the TLR7/8 pathway.

Bioorg Med Chem Lett 2020 09 24;30(17):127366. Epub 2020 Jun 24.

Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Dr., San Diego, CA 92121, USA.

Antagonism of the Toll-like receptors (TLRs) 7 and TLR8 has been hypothesized to be beneficial to patients suffering from autoimmune conditions. A phenotypic screen for small molecule antagonists of TLR7/8 was carried out in a murine P4H1 cell line. Compound 1 was identified as a hit that showed antagonistic activity on TLR7 and TLR8 but not TLR9, as shown on human peripheral blood mononuclear cells (hPBMCs). It was functionally cross reactive with mouse TLR7 but lacked oral exposure and had only modest potency. Chemical optimization resulted in 2, which showed in vivo efficacy following intraperitoneal administration. Further optimization resulted in 8 which had excellent in vitro activity, exposure and in vivo activity. Additional work to improve physical properties resulted in 15, an advanced lead that had favorable in vitro and exposure properties. It was further demonstrated that activity of the series tracked with binding to the extracellular domain of TLR7 implicating that the target of this series are endosomal TLRs rather than downstream signaling pathways.
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http://dx.doi.org/10.1016/j.bmcl.2020.127366DOI Listing
September 2020

Butyrate inhibits human mast cell activation via epigenetic regulation of FcεRI-mediated signaling.

Allergy 2020 08 24;75(8):1966-1978. Epub 2020 Apr 24.

Dermatological Allergology, Dermatology and Allergy, Charité - Universitätsmedizin Berlin, Berlin, Germany.

Background: Short-chain fatty acids (SCFAs) are fermented dietary components that regulate immune responses, promote colonic health, and suppress mast cell-mediated diseases. However, the effects of SCFAs on human mast cell function, including the underlying mechanisms, remain unclear. Here, we investigated the effects of the SCFAs (acetate, propionate, and butyrate) on mast cell-mediated pathology and human mast cell activation, including the molecular mechanisms involved.

Method: Precision-cut lung slices (PCLS) of allergen-exposed guinea pigs were used to assess the effects of butyrate on allergic airway contraction. Human and mouse mast cells were co-cultured with SCFAs and assessed for degranulation after IgE- or non-IgE-mediated stimulation. The underlying mechanisms involved were investigated using knockout mice, small molecule inhibitors/agonists, and genomics assays.

Results: Butyrate treatment inhibited allergen-induced histamine release and airway contraction in guinea pig PCLS. Propionate and butyrate, but not acetate, inhibited IgE- and non-IgE-mediated human or mouse mast cell degranulation in a concentration-dependent manner. Notably, these effects were independent of the stimulation of SCFA receptors GPR41, GPR43, or PPAR, but instead were associated with inhibition of histone deacetylases. Transcriptome analyses revealed butyrate-induced downregulation of the tyrosine kinases BTK, SYK, and LAT, critical transducers of FcεRI-mediated signals that are essential for mast cell activation. Epigenome analyses indicated that butyrate redistributed global histone acetylation in human mast cells, including significantly decreased acetylation at the BTK, SYK, and LAT promoter regions.

Conclusion: Known health benefits of SCFAs in allergic disease can, at least in part, be explained by epigenetic suppression of human mast cell activation.
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http://dx.doi.org/10.1111/all.14254DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7703657PMC
August 2020

Requirement of Mucosa-Associated Lymphoid Tissue Lymphoma Translocation Protein 1 Protease Activity for Fcγ Receptor-Induced Arthritis, but Not Fcγ Receptor-Mediated Platelet Elimination, in Mice.

Arthritis Rheumatol 2020 06 26;72(6):919-930. Epub 2020 Apr 26.

Novartis Institutes for BioMedical Research, Basel, Switzerland.

Objective: Fcγ receptors (FcγR) play important roles in both protective and pathogenic immune responses. The assembly of the CBM signalosome encompassing caspase recruitment domain-containing protein 9, B cell CLL/lymphoma 10, and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT-1) is required for optimal FcγR-induced canonical NF-κB activation and proinflammatory cytokine release. This study was undertaken to clarify the relevance of MALT-1 protease activity in FcγR-driven events and evaluate the therapeutic potential of selective MALT-1 protease inhibitors in FcγR-mediated diseases.

Methods: Using genetic and pharmacologic disruption of MALT-1 scaffolding and enzymatic activity, we assessed the relevance of MALT-1 function in murine and human primary myeloid cells upon stimulation with immune complexes (ICs) and in murine models of autoantibody-driven arthritis and immune thrombocytopenic purpura (ITP).

Results: MALT-1 protease function is essential for optimal FcγR-induced production of proinflammatory cytokines by various murine and human myeloid cells stimulated with ICs. In contrast, MALT-1 protease inhibition did not affect the Syk-dependent, FcγR-mediated production of reactive oxygen species or leukotriene B . Notably, pharmacologic MALT-1 protease inhibition in vivo reduced joint inflammation in the murine K/BxN serum-induced arthritis model (mean area under the curve for paw swelling of 45.42% versus 100% in control mice; P = 0.0007) but did not affect platelet depletion in a passive model of ITP.

Conclusion: Our findings indicate a specific contribution of MALT-1 protease activity to FcγR-mediated events and suggest that MALT-1 protease inhibitors have therapeutic potential in a subset of FcγR-driven inflammatory disorders.
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http://dx.doi.org/10.1002/art.41204DOI Listing
June 2020

Malt1 Protease Deficiency in Mice Disrupts Immune Homeostasis at Environmental Barriers and Drives Systemic T Cell-Mediated Autoimmunity.

J Immunol 2019 12 28;203(11):2791-2806. Epub 2019 Oct 28.

Novartis Institutes for BioMedical Research, Novartis Pharma AG, 4002 Basel, Switzerland;

The paracaspase Malt1 is a key regulator of canonical NF-κB activation downstream of multiple receptors in both immune and nonimmune cells. Genetic disruption of Malt1 protease function in mice and mutations in humans results in reduced regulatory T cells and a progressive multiorgan inflammatory pathology. In this study, we evaluated the altered immune homeostasis and autoimmune disease in Malt1 protease-deficient (Malt1PD) mice and the Ags driving disease manifestations. Our data indicate that B cell activation and IgG1/IgE production is triggered by microbial and dietary Ags preferentially in lymphoid organs draining mucosal barriers, likely as a result of dysregulated mucosal immune homeostasis. Conversely, the disease was driven by a polyclonal T cell population directed against self-antigens. Characterization of the Malt1PD T cell compartment revealed expansion of T effector memory cells and concomitant loss of a CD4 T cell population that phenotypically resembles anergic T cells. Therefore, we propose that the compromised regulatory T cell compartment in Malt1PD animals prevents the efficient maintenance of anergy and supports the progressive expansion of pathogenic, IFN-γ-producing T cells. Overall, our data revealed a crucial role of the Malt1 protease for the maintenance of intestinal and systemic immune homeostasis, which might provide insights into the mechanisms underlying IPEX-related diseases associated with mutations in .
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http://dx.doi.org/10.4049/jimmunol.1900327DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6859376PMC
December 2019

GPR91 senses extracellular succinate released from inflammatory macrophages and exacerbates rheumatoid arthritis.

J Exp Med 2016 08 1;213(9):1655-62. Epub 2016 Aug 1.

Department of Autoimmunity Transplantation and Inflammation, Novartis Institutes for BioMedical Research, 4002 Basel, Switzerland.

When SUCNR1/GPR91-expressing macrophages are activated by inflammatory signals, they change their metabolism and accumulate succinate. In this study, we show that during this activation, macrophages release succinate into the extracellular milieu. They simultaneously up-regulate GPR91, which functions as an autocrine and paracrine sensor for extracellular succinate to enhance IL-1β production. GPR91-deficient mice lack this metabolic sensor and show reduced macrophage activation and production of IL-1β during antigen-induced arthritis. Succinate is abundant in synovial fluids from rheumatoid arthritis (RA) patients, and these fluids elicit IL-1β release from macrophages in a GPR91-dependent manner. Together, we reveal a GPR91/succinate-dependent feed-forward loop of macrophage activation and propose GPR91 antagonists as novel therapeutic principles to treat RA.
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http://dx.doi.org/10.1084/jem.20160061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4995082PMC
August 2016

The IL-33/ST2 pathway contributes to intestinal tumorigenesis in humans and mice.

Oncoimmunology 2016;5(1):e1062966. Epub 2015 Jun 26.

Institute of Pathology, University of Bern , Bern, Switzerland.

Colorectal cancer (CRC) develops through a multistep process and is modulated by inflammation. However, the inflammatory pathways that support intestinal tumors at different stages remain incompletely understood. Interleukin (IL)-33 signaling plays a role in intestinal inflammation, yet its contribution to the pathogenesis of CRC is unknown. Using immunohistochemistry on 713 resected human CRC specimens, we show here that IL-33 and its receptor ST2 are expressed in low-grade and early-stage human CRCs, and to a lesser extent in higher-grade and more advanced-stage tumors. In a mouse model of CRC, ST2-deficiency protects from tumor development. Moreover, bone marrow (BM) chimera studies indicate that engagement of the IL-33/ST2 pathway on both the radio-resistant and radio-sensitive compartment is essential for CRC development. Mechanistically, activation of IL-33/ST2 signaling compromises the integrity of the intestinal barrier and triggers the production of pro-tumorigenic IL-6 by immune cells. Together, this data reveals a tumor-promoting role of IL-33/ST2 signaling in CRC.
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http://dx.doi.org/10.1080/2162402X.2015.1062966DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4760343PMC
June 2015

Interleukin-33 Expression Indicates a Favorable Prognosis in Malignant Salivary Gland Tumors.

Int J Surg Pathol 2016 Aug 23;24(5):394-400. Epub 2016 Feb 23.

Institute of Pathology, Cantonal Hospital Baselland, Liestal, Switzerland

The cytokine interleukin-33 (IL-33) is abundantly expressed in epithelial barrier tissues such as salivary glands. Here, we characterized nuclear IL-33 protein expression by immunohistochemistry in benign and malignant salivary gland tumors and associated it with disease outcome. Most benign salivary gland tumors expressed IL-33, and all Warthin's tumors showed strong and consistent IL-33 expression in the basally oriented cells of their bilayered epithelium. In the malignant group of neoplasms, nuclear IL-33 expression was limited to specific tumor entities-for example, to epithelial-myopepithelial carcinomas (n = 9/11), acinic cell carcinomas (n = 13/27), and oncocytic carcinomas (n = 2/2). IL-33 expression in the combined group of malignant salivary gland neoplasms was significantly associated with favorable histological parameters, lack of metastasis, and longer overall survival, compared with IL-33-negative tumors. We conclude that IL-33 expression is a novel prognostic marker for malignant salivary gland tumors with potential use in clinical diagnostics.
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http://dx.doi.org/10.1177/1066896916633856DOI Listing
August 2016

The Intestinal Microbiota Contributes to the Ability of Helminths to Modulate Allergic Inflammation.

Immunity 2015 Nov 27;43(5):998-1010. Epub 2015 Oct 27.

Global Health Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland. Electronic address:

Intestinal helminths are potent regulators of their host's immune system and can ameliorate inflammatory diseases such as allergic asthma. In the present study we have assessed whether this anti-inflammatory activity was purely intrinsic to helminths, or whether it also involved crosstalk with the local microbiota. We report that chronic infection with the murine helminth Heligmosomoides polygyrus bakeri (Hpb) altered the intestinal habitat, allowing increased short chain fatty acid (SCFA) production. Transfer of the Hpb-modified microbiota alone was sufficient to mediate protection against allergic asthma. The helminth-induced anti-inflammatory cytokine secretion and regulatory T cell suppressor activity that mediated the protection required the G protein-coupled receptor (GPR)-41. A similar alteration in the metabolic potential of intestinal bacterial communities was observed with diverse parasitic and host species, suggesting that this represents an evolutionary conserved mechanism of host-microbe-helminth interactions.
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http://dx.doi.org/10.1016/j.immuni.2015.09.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4658337PMC
November 2015

Translating nucleic acid-sensing pathways into therapies.

Nat Rev Immunol 2015 Sep 21;15(9):529-44. Epub 2015 Aug 21.

German Center for Infection Research Cologne-Bonn, Institute of Clinical Chemistry and Clinical Pharmacology, University of Bonn, Sigmund-Freud Strasse 25, 53127 Bonn, Germany.

Nucleic acid sensing by innate receptors initiates immune defences against viruses and other pathogens. A hallmark of this response is the release of interferons (IFNs), which promote protective immunity by inducing IFN-stimulated genes (ISGs). A similar ISG signature is found in autoinflammatory and autoimmune conditions, indicating that chronic activation of nucleic acid-sensing pathways may contribute to these diseases. Here, we review how nucleic acid-sensing pathways are currently being targeted pharmacologically with both agonists and antagonists. We discuss how an improved understanding of the biology of these pathways is leading to novel therapies for infections, cancer, and autoimmune and autoinflammatory disorders, and how new therapeutics will, in turn, generate a deeper understanding of these complex diseases.
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http://dx.doi.org/10.1038/nri3875DOI Listing
September 2015

The IL-33/ST2 axis augments effector T-cell responses during acute GVHD.

Blood 2015 May 26;125(20):3183-92. Epub 2015 Mar 26.

Department of Pediatrics, Division of Hematology, Oncology, and Blood and Marrow Transplantation, University of Minnesota, Minneapolis, MN;

Interleukin (IL)-33 binding to the receptor suppression of tumorigenicity 2 (ST2) produces pro-inflammatory and anti-inflammatory effects. Increased levels of soluble ST2 (sST2) are a biomarker for steroid-refractory graft-versus-host disease (GVHD) and mortality. However, whether sST2 has a role as an immune modulator or only as a biomarker during GVHD was unclear. We show increased IL-33 production by nonhematopoietic cells in the gastrointestinal (GI) tract in mice post-conditioning and patients during GVHD. Exogenous IL-33 administration during the peak inflammatory response worsened GVHD. Conversely, GVHD lethality and tumor necrosis factor-α production was significantly reduced in il33(-/-) recipients. ST2 was upregulated on murine and human alloreactive T cells and sST2 increased as experimental GVHD progressed. Concordantly, st2(-/-) vs wild-type (WT) donor T cells had a marked reduction in GVHD lethality and GI histopathology. Alloantigen-induced IL-18 receptor upregulation was lower in st2(-/-) T cells, and linked to reduced interferon-γ production by st2(-/-) vs WT T cells during GVHD. Blockade of IL-33/ST2 interactions during allogeneic-hematopoietic cell transplantation by exogenous ST2-Fc infusions had a marked reduction in GVHD lethality, indicating a role of ST2 as a decoy receptor modulating GVHD. Together, these studies point to the IL-33/ST2 axis as a novel and potent target for GVHD therapy.
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http://dx.doi.org/10.1182/blood-2014-10-606830DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4432012PMC
May 2015

Cessation of CCL2 inhibition accelerates breast cancer metastasis by promoting angiogenesis.

Nature 2014 Nov 22;515(7525):130-3. Epub 2014 Oct 22.

Friedrich Miescher Institute for Biomedical Research (FMI), Basel 4058, Switzerland.

Secretion of C-C chemokine ligand 2 (CCL2) by mammary tumours recruits CCR2-expressing inflammatory monocytes to primary tumours and metastatic sites, and CCL2 neutralization in mice inhibits metastasis by retaining monocytes in the bone marrow. Here we report a paradoxical effect of CCL2 in four syngeneic mouse models of metastatic breast cancer. Surprisingly, interruption of CCL2 inhibition leads to an overshoot of metastases and accelerates death. This is the result of monocyte release from the bone marrow and enhancement of cancer cell mobilization from the primary tumour, as well as blood vessel formation and increased proliferation of metastatic cells in the lungs in an interleukin (IL)-6- and vascular endothelial growth factor (VEGF)-A-dependent manner. Notably, inhibition of CCL2 and IL-6 markedly reduced metastases and increased survival of the animals. CCL2 has been implicated in various neoplasias and adopted as a therapeutic target. However, our results call for caution when considering anti-CCL2 agents as monotherapy in metastatic disease and highlight the tumour microenvironment as a critical determinant of successful anti-metastatic therapy.
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http://dx.doi.org/10.1038/nature13862DOI Listing
November 2014

Gut microbiota metabolism of dietary fiber influences allergic airway disease and hematopoiesis.

Nat Med 2014 Feb 5;20(2):159-66. Epub 2014 Jan 5.

Faculty of Biology and Medicine, University of Lausanne, Service de Pneumologie, BH19.206 Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland.

Metabolites from intestinal microbiota are key determinants of host-microbe mutualism and, consequently, the health or disease of the intestinal tract. However, whether such host-microbe crosstalk influences inflammation in peripheral tissues, such as the lung, is poorly understood. We found that dietary fermentable fiber content changed the composition of the gut and lung microbiota, in particular by altering the ratio of Firmicutes to Bacteroidetes. The gut microbiota metabolized the fiber, consequently increasing the concentration of circulating short-chain fatty acids (SCFAs). Mice fed a high-fiber diet had increased circulating levels of SCFAs and were protected against allergic inflammation in the lung, whereas a low-fiber diet decreased levels of SCFAs and increased allergic airway disease. Treatment of mice with the SCFA propionate led to alterations in bone marrow hematopoiesis that were characterized by enhanced generation of macrophage and dendritic cell (DC) precursors and subsequent seeding of the lungs by DCs with high phagocytic capacity but an impaired ability to promote T helper type 2 (TH2) cell effector function. The effects of propionate on allergic inflammation were dependent on G protein-coupled receptor 41 (GPR41, also called free fatty acid receptor 3 or FFAR3), but not GPR43 (also called free fatty acid receptor 2 or FFAR2). Our results show that dietary fermentable fiber and SCFAs can shape the immunological environment in the lung and influence the severity of allergic inflammation.
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http://dx.doi.org/10.1038/nm.3444DOI Listing
February 2014

Naive B-cell trafficking is shaped by local chemokine availability and LFA-1-independent stromal interactions.

Blood 2013 May 4;121(20):4101-9. Epub 2013 Apr 4.

Theodor Kocher Institute, University of Bern, Bern, Switzerland.

It is not known how naive B cells compute divergent chemoattractant signals of the T-cell area and B-cell follicles during in vivo migration. Here, we used two-photon microscopy of peripheral lymph nodes (PLNs) to analyze the prototype G-protein-coupled receptors (GPCRs) CXCR4, CXCR5, and CCR7 during B-cell migration, as well as the integrin LFA-1 for stromal guidance. CXCR4 and CCR7 did not influence parenchymal B-cell motility and distribution, despite their role during B-cell arrest in venules. In contrast, CXCR5 played a nonredundant role in B-cell motility in follicles and in the T-cell area. B-cell migration in the T-cell area followed a random guided walk model, arguing against directed migration in vivo. LFA-1, but not α4 integrins, contributed to B-cell motility in PLNs. However, stromal network guidance was LFA-1 independent, uncoupling integrin-dependent migration from stromal attachment. Finally, we observed that despite a 20-fold reduction of chemokine expression in virus-challenged PLNs, CXCR5 remained essential for B-cell screening of antigen-presenting cells. Our data provide an overview of the contribution of prototype GPCRs and integrins during naive B-cell migration and shed light on the local chemokine availability that these cells compute.
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http://dx.doi.org/10.1182/blood-2012-10-465336DOI Listing
May 2013

Neutralisation of the interleukin-33/ST2 pathway ameliorates experimental colitis through enhancement of mucosal healing in mice.

Gut 2013 Dec 21;62(12):1714-23. Epub 2012 Nov 21.

CNRS and University, UMR7355, Molecular Immunology, Orleans, France and Institute of Infectious Disease and Molecular Medicine, University of Cape Town, RSA.

Objective: Inflammatory bowel diseases (IBD) have been intrinsically linked to a deregulated cytokine network, but novel therapeutic principles are urgently needed. Here we identify the interleukin (IL)-33 and its receptor ST2 as key negative regulators of wound healing and permeability in the colon of mice.

Design: Expression of IL-33 and ST2 was determined by qRT-PCR, ELISA, immunohistochemistry and western-blot analysis. Wild-type and St2(-/-) mice were used in wound healing experiments and in two experimental models of IBD triggered by 2,4,6-trinitrobenzene sulphonic acid or dextran sodium sulphate (DSS). Neutralisation of ST2 was performed by using a specific blocking antibody.

Results: Nuclear localisation and enhanced expression of IL-33 in myofibroblasts and enterocytes was linked to disease involvement independently of inflammation, while the expression of ST2 was primarily restricted to the colonic epithelia. In two experimental models of IBD, genetic ablation of ST2 significantly improved signs of colitis, while a sustained epithelial expression of the cyto-protective factor connexin-43 was observed in DSS-treated St2-deficient mice. Unexpectedly, absence of ST2 in non-hematopoietic cells was sufficient to protect against colitis. Consistently, specific inhibition of endogenous ST2-mediated signalling by treatment with neutralising antibody improved DSS-induced colitis. In addition, IL-33 treatment impaired epithelial barrier permeability in vitro and in vivo, whereas absence of ST2 enhanced wound healing response upon acute mechanical injury in the colon.

Conclusions: Our study unveiled a novel non-hematopoietic function of IL-33 in epithelial barrier function and wound healing. Therefore, blocking the IL-33/ST2 axis may represent an efficient therapy in IBD.
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http://dx.doi.org/10.1136/gutjnl-2011-301785DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3841767PMC
December 2013

A novel role of sphingosine 1-phosphate receptor S1pr1 in mouse thrombopoiesis.

J Exp Med 2012 Nov 12;209(12):2165-81. Epub 2012 Nov 12.

Medizinische Klinik und Poliklinik I, Klinikum der Universität, Ludwig-Maximilian-Universität München, 81337 Munich, Germany.

Millions of platelets are produced each hour by bone marrow (BM) megakaryocytes (MKs). MKs extend transendothelial proplatelet (PP) extensions into BM sinusoids and shed new platelets into the blood. The mechanisms that control platelet generation remain incompletely understood. Using conditional mutants and intravital multiphoton microscopy, we show here that the lipid mediator sphingosine 1-phosphate (S1P) serves as a critical directional cue guiding the elongation of megakaryocytic PP extensions from the interstitium into BM sinusoids and triggering the subsequent shedding of PPs into the blood. Correspondingly, mice lacking the S1P receptor S1pr1 develop severe thrombocytopenia caused by both formation of aberrant extravascular PPs and defective intravascular PP shedding. In contrast, activation of S1pr1 signaling leads to the prompt release of new platelets into the circulating blood. Collectively, our findings uncover a novel function of the S1P-S1pr1 axis as master regulator of efficient thrombopoiesis and might raise new therapeutic options for patients with thrombocytopenia.
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http://dx.doi.org/10.1084/jem.20121090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3501353PMC
November 2012

If you don't look, you won't see: intravital multiphoton imaging of primary and metastatic breast cancer.

J Mammary Gland Biol Neoplasia 2012 Jun 12;17(2):125-9. Epub 2012 May 12.

Friedrich Miescher Institute for Biomedical Research (FMI), Maulbeerstrasse 66, Basel, Switzerland.

A fundamental hallmark of cancer is progression to metastasis and the growth of breast cancer metastases in lung, bone, liver and/or brain causes fatal complications. Unfortunately, the cellular and biochemical mechanisms of the metastatic process remain ill-defined. Recent application of intravital multiphoton microscopy (MP-IVM) to image fluorescently labeled cells in mouse models of cancer has allowed dynamic observation of this multi-step process at the cellular and subcellular levels. In this article, we discuss the use of MP-IVM in studies of breast cancer metastasis, as well as surgical techniques for exposing tumors prior to imaging. We also describe a versatile multiphoton microscope for imaging tumor-stroma interactions.
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http://dx.doi.org/10.1007/s10911-012-9250-8DOI Listing
June 2012

CCL17-expressing dendritic cells drive atherosclerosis by restraining regulatory T cell homeostasis in mice.

J Clin Invest 2011 Jul;121(7):2898-910

Institute for Cardiovascular Prevention, Ludwig-Maximilians-Universität München, Munich, Germany.

Immune mechanisms are known to control the pathogenesis of atherosclerosis. However, the exact role of DCs, which are essential for priming of immune responses, remains elusive. We have shown here that the DC-derived chemokine CCL17 is present in advanced human and mouse atherosclerosis and that CCL17+ DCs accumulate in atherosclerotic lesions. In atherosclerosis-prone mice, Ccl17 deficiency entailed a reduction of atherosclerosis, which was dependent on Tregs. Expression of CCL17 by DCs limited the expansion of Tregs by restricting their maintenance and precipitated atherosclerosis in a mechanism conferred by T cells. Conversely, a blocking antibody specific for CCL17 expanded Tregs and reduced atheroprogression. Our data identify DC-derived CCL17 as a central regulator of Treg homeostasis, implicate DCs and their effector functions in atherogenesis, and suggest that CCL17 might be a target for vascular therapy.
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http://dx.doi.org/10.1172/JCI44925DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3223829PMC
July 2011

Th17 cells, not IL-17+ γδ T cells, drive arthritic bone destruction in mice and humans.

J Immunol 2011 Feb 7;186(4):2602-12. Epub 2011 Jan 7.

Department of Autoimmunity, Novartis Institutes for BioMedical Research, 4002 Basel, Switzerland.

The mechanism whereby IL-17 drives rheumatoid arthritis remains incompletely understood. We demonstrate that anti-IL-17 therapy in collagen-induced arthritis ameliorates bone damage by reducing the number of osteoclasts in joints. We found equal numbers of CD4(+) Th17 and IL-17 producing γδ T cells in the joints of arthritic mice, and in vitro, both populations similarly induced osteoclastogenesis. However, individual depletion and adoptive transfer studies revealed that in vivo, Th17 cells dominated with regard to bone destruction. Unlike γδ T cells, Th17 cells were found in apposition to tartrate-resistant acid phosphatase positive osteoclasts in subchondral areas of inflamed joints, a pattern reproduced in patient biopsies. This localization was caused by Ag-specific retention, because OVA-primed Th17 cells showed a γδ T cell-like diffuse distribution. Because IL-23, as produced by osteoclasts, enhanced T cell-mediated osteoclastogenesis, we propose that Ag-specific juxtaposition is key to foster the molecular cross talk of Th17 cells and osteoclasts, thus driving arthritic bone destruction.
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http://dx.doi.org/10.4049/jimmunol.1003370DOI Listing
February 2011

Merkel cell polyomavirus is present in common warts and carcinoma in situ of the skin.

Hum Pathol 2010 Oct 22;41(10):1369-79. Epub 2010 Jul 22.

Kempf & Pfaltz Histological Diagnostics, Research Unit, Zurich, Switzerland.

Polyomaviruses have been linked to diseases of immunosuppressed patients. We sought to determine the prevalence of Merkel cell polyomavirus in benign epithelial skin neoplasms and nonmelanoma skin cancer of immunosuppressed renal transplant recipients and long-term dialysis patients. Merkel cell polyomavirus DNA was detected by polymerase chain reaction (PCR) in 2 (10%) of 20 patients, in carcinomas in situ (Bowen's disease). In one of our patients with Merkel cell polyomavirus-positive carcinoma in situ, 9 (39.1%) of 23 skin lesions at various anatomical locations tested positive for Merkel cell polyomavirus sequences by PCR, including all of his common warts (4/4), half of his carcinoma in situ lesions (3/6), and 2 of his 3 seborrheic keratoses. In a second cohort of immunosuppressed renal transplant recipients, Merkel cell polyomavirus DNA was found in 1 (6.3%) of 16 common warts and in 2 (9.5%) of 21 carcinomas in situ. In immunocompetent individuals, Merkel cell polyomavirus DNA was found in 2 (6.7%) of 30 common warts and in 2 (8.3%) of 24 carcinomas in situ. DNA of other human polyomaviruses was not detected in any of the investigated skin neoplasms. We conclude that common warts and carcinomas in situ can be positive for Merkel cell polyomavirus in immunosuppressed as well as immunocompetent individuals. Remarkably, some of the Merkel cell polyomavirus-positive common warts did not contain human papillomavirus. Furthermore, Merkel cell polyomavirus can be found in various skin neoplasms of the same individual.
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http://dx.doi.org/10.1016/j.humpath.2010.01.023DOI Listing
October 2010

Subcapsular sinus macrophages prevent CNS invasion on peripheral infection with a neurotropic virus.

Nature 2010 Jun;465(7301):1079-83

Immune Disease Institute and Department of Pathology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, USA.

Lymph nodes (LNs) capture microorganisms that breach the body's external barriers and enter draining lymphatics, limiting the systemic spread of pathogens. Recent work has shown that CD11b(+)CD169(+) macrophages, which populate the subcapsular sinus (SCS) of LNs, are critical for the clearance of viruses from the lymph and for initiating antiviral humoral immune responses. Here we show, using vesicular stomatitis virus (VSV), a relative of rabies virus transmitted by insect bites, that SCS macrophages perform a third vital function: they prevent lymph-borne neurotropic viruses from infecting the central nervous system (CNS). On local depletion of LN macrophages, about 60% of mice developed ascending paralysis and died 7-10 days after subcutaneous infection with a small dose of VSV, whereas macrophage-sufficient animals remained asymptomatic and cleared the virus. VSV gained access to the nervous system through peripheral nerves in macrophage-depleted LNs. In contrast, within macrophage-sufficient LNs VSV replicated preferentially in SCS macrophages but not in adjacent nerves. Removal of SCS macrophages did not compromise adaptive immune responses against VSV, but decreased type I interferon (IFN-I) production within infected LNs. VSV-infected macrophages recruited IFN-I-producing plasmacytoid dendritic cells to the SCS and in addition were a major source of IFN-I themselves. Experiments in bone marrow chimaeric mice revealed that IFN-I must act on both haematopoietic and stromal compartments, including the intranodal nerves, to prevent lethal infection with VSV. These results identify SCS macrophages as crucial gatekeepers to the CNS that prevent fatal viral invasion of the nervous system on peripheral infection.
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http://dx.doi.org/10.1038/nature09118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892812PMC
June 2010

Inflammatory monocytes are a reservoir for Merkel cell polyomavirus.

J Invest Dermatol 2010 Apr 17;130(4):1146-51. Epub 2009 Dec 17.

Kempf and Pfaltz Histological Diagnostics, Research Unit, Zurich, Switzerland.

Merkel cell polyomavirus (MCPyV) is a recently discovered virus that is implicated in the oncogenesis of Merkel cell carcinoma (MCC). The route of dissemination and the reservoir(s) of MCPyV within the human body have not yet been identified. In this study we describe two patients with multiple MCPyV-positive inflammatory and neoplastic skin lesions at different anatomic sites. Patient 1 was suffering from psoriasis for many years and was diagnosed with MCC 7 years before this study. Patient 2 had developed numerous non-melanoma skin cancer lesions under post-transplant immunosuppression. In both patients, MCPyV DNA was detected in whole blood and in urine using PCR and direct sequencing of PCR products. When we analyzed different blood compartments, we found MCPyV exclusively in cell-free serum and in blood monocytes, but not in lymphocytes or granulocytes. Upon separate analysis of resident (CD14(lo)CD16(+)) and inflammatory (CD14(+)CD16(-)) monocytes, we detected MCPyV exclusively in inflammatory, but not in resident monocytes. Our findings raise the possibility that MCPyV persists in inflammatory monocytes and spreads along the migration routes of inflammatory monocytes. This points to intervention strategies to contain MCPyV. Moreover, blood or urine tests may serve as ancillary tests to confirm MCPyV infection in a clinical setting.
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http://dx.doi.org/10.1038/jid.2009.392DOI Listing
April 2010

Form follows function: lymphoid tissue microarchitecture in antimicrobial immune defence.

Nat Rev Immunol 2008 Oct;8(10):764-75

Novartis Institutes for BioMedical Research, 4002 Basel, Switzerland.

Secondary lymphoid organs (SLOs) are tissues that facilitate the induction of adaptive immune responses. These organs capture pathogens to limit their spread throughout the body, bring antigen-presenting cells into productive contact with their cognate lymphocytes and provide niches for the differentiation of immune effector cells. Therefore, the microanatomy of SLOs defines the ability of an organism to respond to pathogens. SLO microarchitecture is, at the same time, extremely adaptable to environmental changes. In this Review, we discuss recent insights into the function and plasticity of the SLO microenvironment with regards to antimicrobial immune defence.
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http://dx.doi.org/10.1038/nri2414DOI Listing
October 2008

Triggering the succinate receptor GPR91 on dendritic cells enhances immunity.

Nat Immunol 2008 Nov 28;9(11):1261-9. Epub 2008 Sep 28.

Novartis Institutes for Biomedical Research, Vienna A-1235, Austria.

Succinate acts as an extracellular mediator signaling through the G protein-coupled receptor GPR91. Here we show that dendritic cells had high expression of GPR91. In these cells, succinate triggered intracellular calcium mobilization, induced migratory responses and acted in synergy with Toll-like receptor ligands for the production of proinflammatory cytokines. Succinate also enhanced antigen-specific activation of human and mouse helper T cells. GPR91-deficient mice had less migration of Langerhans cells to draining lymph nodes and impaired tetanus toxoid-specific recall T cell responses. Furthermore, GPR91-deficient allografts elicited weaker transplant rejection than did the corresponding grafts from wild-type mice. Our results suggest that the succinate receptor GPR91 is involved in sensing immunological danger, which establishes a link between immunity and a metabolite of cellular respiration.
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http://dx.doi.org/10.1038/ni.1657DOI Listing
November 2008

Overexpression of lymphotoxin in T cells induces fulminant thymic involution.

Am J Pathol 2008 Jun 15;172(6):1555-70. Epub 2008 May 15.

Institute of Neuropathology, University Hospital of Zürich, Schmelzbergstrasse 12, CH-8091 Zürich, Switzerland.

Activated lymphocytes and lymphoid-tissue inducer cells express lymphotoxins (LTs), which are essential for the organogenesis and maintenance of lymphoreticular microenvironments. Here we describe that T-cell-restricted overexpression of LT induces fulminant thymic involution. This phenotype was prevented by ablation of the LT receptors tumor necrosis factor receptor (TNFR) 1 or LT beta receptor (LTbetaR), representing two non-redundant pathways. Multiple lines of transgenic Ltalphabeta and Ltalpha mice show such a phenotype, which was not observed on overexpression of LTbeta alone. Reciprocal bone marrow transfers between LT-overexpressing and receptor-ablated mice show that involution was not due to a T cell-autonomous defect but was triggered by TNFR1 and LTbetaR signaling to radioresistant stromal cells. Thymic involution was partially prevented by the removal of one allele of LTbetaR but not of TNFR1, establishing a hierarchy in these signaling events. Infection with the lymphocytic choriomeningitis virus triggered a similar thymic pathology in wt, but not in Tnfr1(-/-) mice. These mice displayed elevated TNFalpha in both thymus and plasma, as well as increased LTs on both CD8(+) and CD4(-)CD8(-) thymocytes. These findings suggest that enhanced T cell-derived LT expression helps to control the physiological size of the thymic stroma and accelerates its involution via TNFR1/LTbetaR signaling in pathological conditions and possibly also in normal aging.
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http://dx.doi.org/10.2353/ajpath.2008.070572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2408416PMC
June 2008

Restoration of lymphoid organ integrity through the interaction of lymphoid tissue-inducer cells with stroma of the T cell zone.

Nat Immunol 2008 Jun 20;9(6):667-75. Epub 2008 Apr 20.

Research Department, Kantonal Hospital of St. Gallen, 9007 St. Gallen, Switzerland.

The generation of lymphoid microenvironments in early life depends on the interaction of lymphoid tissue-inducer cells with stromal lymphoid tissue-organizer cells. Whether this cellular interface stays operational in adult secondary lymphoid organs has remained elusive. We show here that during acute infection with lymphocytic choriomeningitis virus, antiviral cytotoxic T cells destroyed infected T cell zone stromal cells, which led to profound disruption of secondary lymphoid organ integrity. Furthermore, the ability of the host to respond to secondary antigens was lost. Restoration of the lymphoid microanatomy was dependent on the proliferative accumulation of lymphoid tissue-inducer cells in secondary lymphoid organs during the acute phase of infection and lymphotoxin alpha(1)beta(2) signaling. Thus, crosstalk between lymphoid tissue-inducer cells and stromal cells is reactivated in adults to maintain secondary lymphoid organ integrity and thereby contributes to the preservation of immunocompetence.
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http://dx.doi.org/10.1038/ni.1605DOI Listing
June 2008

In vivo imaging of T cell priming.

Sci Signal 2008 Mar 25;1(12):pt2. Epub 2008 Mar 25.

Department of Pathology and the Immune Disease Institute, Harvard Medical School, Boston, MA 02115, USA.

The rules by which naïve T cells decide whether and how to respond to antigenic stimuli are incompletely understood. Using multiphoton intravital microscopy (MP-IVM) in lymph nodes (LNs), we have shown that CD8+ T cells are primed by antigen-presenting dendritic cells (DCs) in three consecutive phases. During phase one, T cells undergo brief serial contacts with many DCs for several hours after homing into the LNs. Subsequently, during phase two, T cells engage in prolonged stable interactions with DCs. Finally, in the third phase, T cells return to transient interactions with DCs as they begin to proliferate and eventually leave the LNs. We have examined the influence of antigen dose on the duration of phase one by systematically varying both the number of cognate peptide-major histocompatability (pMHC) complexes per DC and the density of cognate pMHC complex-presenting DCs per LN. The duration of phase one and the kinetics of CD8+ T cell activation were inversely correlated with both parameters. Very few pMHC complexes were needed for full T cell activation and effector differentiation. Furthermore, there was a sharp threshold of antigen dose below which T cells did not transition to phase two but continued to migrate until they exited the LN, unactivated. The stability of peptide binding to MHC was a critical determinant of this threshold antigen dose in vivo. Our results suggest an integrative mechanism that allows T cells to reach an informed decision about whether to respond, based on the overall antigen dose encountered.
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http://dx.doi.org/10.1126/stke.112pt2DOI Listing
March 2008

T cell sensing of antigen dose governs interactive behavior with dendritic cells and sets a threshold for T cell activation.

Nat Immunol 2008 Mar 20;9(3):282-91. Epub 2008 Jan 20.

Department of Pathology and the Immune Disease Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.

After homing to lymph nodes, CD8+ T cells are primed by dendritic cells (DCs) in three phases. During phase one, T cells undergo brief serial contacts with DCs for several hours, whereas phase two is characterized by stable T cell-DC interactions. We show here that the duration of phase one and T cell activation kinetics correlated inversely with the number of complexes of cognate peptide and major histocompatibility complex (pMHC) per DC and with the density of antigen-presenting DCs per lymph node. Very few pMHC complexes were necessary for the induction of full-fledged T cell activation and effector differentiation. However, neither T cell activation nor transition to phase two occurred below a threshold antigen dose determined in part by pMHC stability. Thus, phase one permits T cells to make integrated 'measurements' of antigen dose that determine subsequent T cell participation in immune responses.
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http://dx.doi.org/10.1038/ni1559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698867PMC
March 2008