Publications by authors named "Doron Merkler"

117 Publications

The Janus Kinase Inhibitor Ruxolitinib Prevents Terminal Shock in a Mouse Model of Arenavirus Hemorrhagic Fever.

Microorganisms 2021 Mar 9;9(3). Epub 2021 Mar 9.

Department of Biomedicine-Haus Petersplatz, Division of Experimental Virology, University of Basel, 4009 Basel, Switzerland.

Arenaviruses such as Lassa virus cause arenavirus hemorrhagic fever (AVHF), but protective vaccines and effective antiviral therapy remain unmet medical needs. Our prior work has revealed that inducible nitric oxide synthase (iNOS) induction by IFN-γ represents a key pathway to microvascular leak and terminal shock in AVHF. Here we hypothesized that Ruxolitinib, an FDA-approved JAK inhibitor known to prevent IFN-γ signaling, could be repurposed for host-directed therapy in AVHF. We tested the efficacy of Ruxolitinib in MHC-humanized (HHD) mice, which develop Lassa fever-like disease upon infection with the monkey-pathogenic lymphocytic choriomeningitis virus strain WE. Anti-TNF antibody therapy was tested as an alternative strategy owing to its expected effect on macrophage activation. Ruxolitinib but not anti-TNF antibody prevented hypothermia and terminal disease as well as pleural effusions and skin edema, which served as readouts of microvascular leak. As expected, neither treatment influenced viral loads. Intriguingly, however, and despite its potent disease-modifying activity, Ruxolitinib did not measurably interfere with iNOS expression or systemic NO metabolite levels. These findings suggest that the FDA-approved JAK-inhibitor Ruxolitinib has potential in the treatment of AVHF. Moreover, our observations indicate that besides IFN-γ-induced iNOS additional druggable pathways contribute essentially to AVHF and are amenable to host-directed therapy.
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http://dx.doi.org/10.3390/microorganisms9030564DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8001354PMC
March 2021

Heterologous arenavirus vector prime-boost overrules self-tolerance for efficient tumor-specific CD8 T cell attack.

Cell Rep Med 2021 Mar 3;2(3):100209. Epub 2021 Mar 3.

University of Basel, Department of Biomedicine, Basel, Switzerland.

Therapeutic vaccination regimens inducing clinically effective tumor-specific CD8 T lymphocyte (CTL) responses are an unmet medical need. We engineer two distantly related arenaviruses, Pichinde virus and lymphocytic choriomeningitis virus, for therapeutic cancer vaccination. In mice, life-replicating vector formats of these two viruses delivering a self-antigen in a heterologous prime-boost regimen induce tumor-specific CTL responses up to 50% of the circulating CD8 T cell pool. This CTL attack eliminates established solid tumors in a significant proportion of animals, accompanied by protection against tumor rechallenge. The magnitude of CTL responses is alarmin driven and requires combining two genealogically distantly related arenaviruses. Vector-neutralizing antibodies do not inhibit booster immunizations by the same vector or by closely related vectors. Rather, CTL immunodominance hierarchies favor vector backbone-targeted responses at the expense of self-reactive CTLs. These findings establish an arenavirus-based immunotherapy regimen that allows reshuffling of immunodominance hierarchies and breaking self-directed tolerance for efficient tumor control.
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http://dx.doi.org/10.1016/j.xcrm.2021.100209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7974551PMC
March 2021

TSPO PET imaging of natalizumab-associated progressive multifocal leukoencephalopathy.

Brain 2021 Mar 23. Epub 2021 Mar 23.

Institute of Clinical Neuroimmunology, University Hospital, Ludwig-Maximilians-Universität Munich, Munich, Germany.

Progressive multifocal leukoencephalopathy (PML) is a severe infection of the central nervous system caused by the polyomavirus JC (JCV) that can occur in multiple sclerosis (MS) patients treated with natalizumab. Clinical management of patients with natalizumab-associated PML is challenging not the least because current imaging tools for the early detection, longitudinal monitoring and differential diagnosis of PML lesions are limited. Here we evaluate whether TSPO positron emission tomography (PET) imaging can be applied to monitor the inflammatory activity of PML lesions over time and differentiate them from MS lesions. For this monocenter pilot study we followed 8 patients with natalizumab-associated PML with PET imaging using the TSPO radioligand [18F]GE-180 combined with frequent 3 T MRI imaging. In addition we compared TSPO PET signals in PML lesions with the signal pattern of MS lesions from 17 independent MS patients. We evaluated the standardized uptake value ratio (SUVR) as well as the morphometry of the TSPO uptake for putative PML and MS lesions areas compared to a radiologically unaffected pseudo-reference region in the cerebrum. Furthermore TSPO expression in situ was immunohistochemically verified by determining the density and cellular identity of TSPO-expressing cells in brain sections from four patients with early natalizumab-associated PML as well as five patients with other forms of PML and six patients with inflammatory demyelinating CNS lesions (clinically isolated syndrome/MS). Histological analysis revealed a reticular accumulation of TSPO expressing phagocytes in PML lesions, while such phagocytes showed a more homogenous distribution in putative MS lesions. TSPO PET imaging showed an enhanced tracer uptake in natalizumab-associated PML lesions that was present from the early to the chronic stages (up to 52 months after PML diagnosis). While gadolinium enhancement on MRI rapidly declined to baseline levels, TSPO tracer uptake followed a slow one phase decay curve. A TSPO-based 3-dimensional diagnostic matrix taking into account the uptake levels as well as the shape and texture of the TSPO signal differentiated more than 96% of PML and MS lesions. Indeed, treatment with rituximab after natalizumab-associated PML in three patients did not affect tracer uptake in the assigned PML lesions but reverted tracer uptake to baseline in the assigned active MS lesions. Taken together our study suggests that TSPO PET imaging can reveal CNS inflammation in natalizumab-associated PML. TSPO PET may facilitate longitudinal monitoring of disease activity and help to distinguish recurrent MS activity from PML progression.
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http://dx.doi.org/10.1093/brain/awab127DOI Listing
March 2021

Formation and immunomodulatory function of meningeal B-cell aggregates in progressive CNS autoimmunity.

Brain 2021 Mar 9. Epub 2021 Mar 9.

Klinikum rechts der Isar, Department of Neurology, Technical University of Munich, 81675 Munich, Germany.

Meningeal B lymphocyte aggregates have been described in autopsy material of patients with chronic Multiple Sclerosis. The presence of meningeal B cell aggregates has been correlated with worse disease. However, the functional role of these meningeal B cell aggregates is not understood. Here, we use a mouse model of Multiple Sclerosis, the spontaneous opticospinal encephalomyelitis model, which is built on the double transgenic expression of myelin oligodendrocyte glycoprotein-specific T cell- and B cell-receptors, to show that the formation of meningeal B cell aggregates is dependent on the expression of α4 integrins by antigen-specific T cells. T cell-conditional genetic ablation of α4 integrins in opticospinal encephalomyelitis mice impaired the formation of meningeal B cell aggregates, and surprisingly, led to a higher disease incidence as compared to opticospinal encephalomyelitis mice with α4 integrin-sufficient T cells. B cell-conditional ablation of α4 integrins in opticospinal encephalomyelitis mice resulted in the entire abrogation of the formation of meningeal B cell aggregates, and opticospinal encephalomyelitis mice with α4 integrin-deficient B cells suffered from a higher disease burden than regular opticospinal encephalomyelitis mice. While anti-CD20 antibody-mediated systemic depletion of B cells in opticospinal encephalomyelitis mice after onset of disease failed to efficiently decrease meningeal B cell aggregates without significantly modulating disease progression, treatment with anti-CD19 chimeric antigen receptor-T cells eliminated meningeal B cell aggregates and exacerbated clinical disease in opticospinal encephalomyelitis mice. Since about 20 percent of B cells in organised meningeal B cell aggregates produced either IL-10 or IL-35, we propose that meningeal B cell aggregates might also have an immunoregulatory function as to the immunopathology in adjacent spinal cord white matter. The immunoregulatory function of meningeal B cell aggregates needs to be considered when designing highly efficient therapies directed against meningeal B cell aggregates for clinical application in Multiple Sclerosis.
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http://dx.doi.org/10.1093/brain/awab093DOI Listing
March 2021

Neuronal metabotropic glutamate receptor 8 protects against neurodegeneration in CNS inflammation.

J Exp Med 2021 May;218(5)

Institut für Neuroimmunologie und Multiple Sklerose, Zentrum für Molekulare Neurobiologie Hamburg, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system with continuous neuronal loss. Treatment of clinical progression remains challenging due to lack of insights into inflammation-induced neurodegenerative pathways. Here, we show that an imbalance in the neuronal receptor interactome is driving glutamate excitotoxicity in neurons of MS patients and identify the MS risk-associated metabotropic glutamate receptor 8 (GRM8) as a decisive modulator. Mechanistically, GRM8 activation counteracted neuronal cAMP accumulation, thereby directly desensitizing the inositol 1,4,5-trisphosphate receptor (IP3R). This profoundly limited glutamate-induced calcium release from the endoplasmic reticulum and subsequent cell death. Notably, we found Grm8-deficient neurons to be more prone to glutamate excitotoxicity, whereas pharmacological activation of GRM8 augmented neuroprotection in mouse and human neurons as well as in a preclinical mouse model of MS. Thus, we demonstrate that GRM8 conveys neuronal resilience to CNS inflammation and is a promising neuroprotective target with broad therapeutic implications.
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http://dx.doi.org/10.1084/jem.20201290DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7938362PMC
May 2021

New advances in immune components mediating viral control in the CNS.

Curr Opin Virol 2021 Feb 23;47:68-78. Epub 2021 Feb 23.

University of Geneva, Department of Pathology and Immunology, Geneva, Switzerland; Division of Clinical Pathology, Geneva University Hospital, 1211 Geneva, Switzerland. Electronic address:

Protective immune responses in the central nervous system (CNS) must act efficiently but need to be tightly controlled to avoid excessive damage to this vital organ. Under homeostatic conditions, the immune surveillance of the CNS is mediated by innate immune cells together with subsets of memory lymphocytes accumulating over lifetime. Accordingly, a wide range of immune responses can be triggered upon pathogen infection that can be associated with devastating clinical outcomes, and which most frequently are due to neurotropic viruses. Here, we discuss recent advances about our understanding of anti-viral immune responses with special emphasis on mechanisms operating in the various anatomical compartments of the CNS.
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http://dx.doi.org/10.1016/j.coviro.2021.02.001DOI Listing
February 2021

Single-cell immune repertoire and transcriptome sequencing reveals that clonally expanded and transcriptionally distinct lymphocytes populate the aged central nervous system in mice.

Proc Biol Sci 2021 Feb 24;288(1945):20202793. Epub 2021 Feb 24.

Department of Biosystems and Engineering, ETH Zurich, Basel, Switzerland.

Neuroinflammation plays a crucial role during ageing and various neurological conditions, including Alzheimer's disease, multiple sclerosis and infection. Technical limitations, however, have prevented an integrative analysis of how lymphocyte immune receptor repertoires and their accompanying transcriptional states change with age in the central nervous system. Here, we leveraged single-cell sequencing to simultaneously profile B cell receptor and T cell receptor repertoires and accompanying gene expression profiles in young and old mouse brains. We observed the presence of clonally expanded B and T cells in the central nervous system of aged male mice. Furthermore, many of these B cells were of the IgM and IgD isotypes, and had low levels of somatic hypermutation. Integrating gene expression information additionally revealed distinct transcriptional profiles of these clonally expanded lymphocytes. Our findings implicate that clonally related T and B cells in the CNS of elderly mice may contribute to neuroinflammation accompanying homeostatic ageing.
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http://dx.doi.org/10.1098/rspb.2020.2793DOI Listing
February 2021

Persistence of self-reactive CD8+ T cells in the CNS requires TOX-dependent chromatin remodeling.

Nat Commun 2021 02 12;12(1):1009. Epub 2021 Feb 12.

Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland.

Self-reactive CD8 T cells are important mediators of progressive tissue damage in autoimmune diseases, but the molecular program underlying these cells' functional adaptation is unclear. Here we characterize the transcriptional and epigenetic landscape of self-reactive CD8 T cells in a mouse model of protracted central nervous system (CNS) autoimmunity and compare it to populations of CNS-resident memory CD8 T cells emerging from acute viral infection. We find that autoimmune CD8 T cells persisting at sites of self-antigen exhibit characteristic transcriptional regulation together with distinct epigenetic remodeling. This self-reactive CD8 T cell fate depends on the transcriptional regulation by the DNA-binding HMG-box protein TOX which remodels more than 400 genomic regions including loci such as Tcf7, which is central to stemness of CD8 T cells. Continuous exposure to CNS self-antigen sustains TOX levels in self-reactive CD8 T cells, whereas genetic ablation of TOX in CD8 T cells results in shortened persistence of self-reactive CD8 T cells in the inflamed CNS. Our study establishes and characterizes the genetic differentiation program enabling chronic T cell-driven immunopathology in CNS autoimmunity.
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http://dx.doi.org/10.1038/s41467-021-21109-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7881115PMC
February 2021

Phagocyte-mediated synapse removal in cortical neuroinflammation is promoted by local calcium accumulation.

Nat Neurosci 2021 03 25;24(3):355-367. Epub 2021 Jan 25.

Institute of Clinical Neuroimmunology, University Hospital, Ludwig-Maximilians University Munich, Munich, Germany.

Cortical pathology contributes to chronic cognitive impairment of patients suffering from the neuroinflammatory disease multiple sclerosis (MS). How such gray matter inflammation affects neuronal structure and function is not well understood. In the present study, we use functional and structural in vivo imaging in a mouse model of cortical MS to demonstrate that bouts of cortical inflammation disrupt cortical circuit activity coincident with a widespread, but transient, loss of dendritic spines. Spines destined for removal show local calcium accumulations and are subsequently removed by invading macrophages or activated microglia. Targeting phagocyte activation with a new antagonist of the colony-stimulating factor 1 receptor prevents cortical synapse loss. Overall, our study identifies synapse loss as a key pathological feature of inflammatory gray matter lesions that is amenable to immunomodulatory therapy.
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http://dx.doi.org/10.1038/s41593-020-00780-7DOI Listing
March 2021

Neuropathology associated with SARS-CoV-2 infection.

Lancet 2021 01;397(10271):276-277

Department of Pathology and Immunology, Division of Clinical Pathology, Geneva University Hospitals, Geneva 1211, Switzerland. Electronic address:

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http://dx.doi.org/10.1016/S0140-6736(21)00095-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7825940PMC
January 2021

Methylation profiling-based diagnosis of radiologically suspected congenital glioma.

Brain Tumor Pathol 2021 Jan 16;38(1):78-80. Epub 2020 Oct 16.

Institute of Pathology, University Hospital and University of Lausanne, Lausanne, Switzerland.

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http://dx.doi.org/10.1007/s10014-020-00384-wDOI Listing
January 2021

Inflammation and lymphocyte infiltration are associated with shorter survival in patients with high-grade glioma.

Oncoimmunology 2020 06 21;9(1):1779990. Epub 2020 Jun 21.

Center for Translational Research in Onco-Hematology, Division of Oncology, Geneva University Hospitals and University of Geneva, Geneva, Switzerland.

Glioma represents a serious health burden in terms of morbidity and mortality. The prognostic significance of the lymphoid and myeloid infiltrates in glioma is not clearly determined. Moreover, the characterization of different leukocyte subsets in the tumor microenvironment relies mainly on immunohistochemistry observations, and data about their association with prognosis are contradictory. Here, we performed acomprehensive study of both the tumor-infiltrating and circulating immune compartments of patients with high-grade glioma. Nineteen tumor biopsies and 30 PBMC samples were analyzed by RNA sequencing. Validation was performed on The Cancer Genome Atlas (TCGA) RNA sequencing data from glioma and on additional 39 tumor biopsies analyzed by flow cytometry. We identified prognostic tumor and peripheral immune signatures, which associate increased inflammation, immune infiltration and activation with shorter overall survival in high-grade glioma patients. Importantly, we confirmed our observations by flow cytometry analysis and validated the tumor-signature using the TCGA dataset. In addition, both tumor genotype and grade associated with the degree of glioma immune infiltration. Unlike in the majority of cancers, lymphocyte infiltration at the tumor site is anegative prognostic factor in glioma, suggesting the ambivalent pro-tumorigenic role of immune responses in glioma.
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http://dx.doi.org/10.1080/2162402X.2020.1779990DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7458651PMC
June 2020

Salivary gland macrophages and tissue-resident CD8 T cells cooperate for homeostatic organ surveillance.

Sci Immunol 2020 04;5(46)

Department of Oncology, Microbiology and Immunology, University of Fribourg, 1700 Fribourg, Switzerland.

It is well established that tissue macrophages and tissue-resident memory CD8 T cells (T) play important roles for pathogen sensing and rapid protection of barrier tissues. In contrast, the mechanisms by which these two cell types cooperate for homeostatic organ surveillance after clearance of infections is poorly understood. Here, we used intravital imaging to show that T dynamically followed tissue macrophage topology in noninflamed murine submandibular salivary glands (SMGs). Depletion of tissue macrophages interfered with SMG T motility and caused a reduction of interepithelial T cell crossing. In the absence of macrophages, SMG T failed to cluster in response to local inflammatory chemokines. A detailed analysis of the SMG microarchitecture uncovered discontinuous attachment of tissue macrophages to neighboring epithelial cells, with occasional macrophage protrusions bridging adjacent acini and ducts. When dissecting the molecular mechanisms that drive homeostatic SMG T motility, we found that these cells exhibit a wide range of migration modes: In addition to chemokine- and adhesion receptor-driven motility, resting SMG T displayed a remarkable capacity for autonomous motility in the absence of chemoattractants and adhesive ligands. Autonomous SMG T motility was mediated by friction and insertion of protrusions into gaps offered by the surrounding microenvironment. In sum, SMG T display a unique continuum of migration modes, which are supported in vivo by tissue macrophages to allow homeostatic patrolling of the complex SMG architecture.
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http://dx.doi.org/10.1126/sciimmunol.aaz4371DOI Listing
April 2020

Eomes broadens the scope of CD8 T-cell memory by inhibiting apoptosis in cells of low affinity.

PLoS Biol 2020 03 17;18(3):e3000648. Epub 2020 Mar 17.

Department of Histology and Embryology, University of Rijeka, Rijeka, Croatia.

The memory CD8 T-cell pool must select for clones that bind immunodominant epitopes with high affinity to efficiently counter reinfection. At the same time, it must retain a level of clonal diversity to allow recognition of pathogens with mutated epitopes. How the level of diversity within the memory pool is controlled is unclear, especially in the context of a selective drive for antigen affinity. We find that preservation of clones that bind the activating antigen with low affinity depends on expression of the transcription factor Eomes in the first days after antigen encounter. Eomes is induced at low activating signal strength and directly drives transcription of the prosurvival protein Bcl-2. At higher signal intensity, T-bet is induced which suppresses Bcl-2 and causes a relative survival advantage for cells of low affinity. Clones activated with high-affinity antigen form memory largely independent of Eomes and have a proliferative advantage over clones that bind the same antigen with low affinity. This causes high-affinity clones to prevail in the memory pool, despite their relative survival deficit. Genetic or therapeutic targeting of the Eomes/Bcl-2 axis reduces the clonal diversity of the memory pool, which diminishes its ability to respond to pathogens carrying mutations in immunodominant epitopes. Thus, we demonstrate on a molecular level how sufficient diversity of the memory pool is established in an environment of affinity-based selection.
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http://dx.doi.org/10.1371/journal.pbio.3000648DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7077837PMC
March 2020

Microglial A20 Protects the Brain from CD8 T-Cell-Mediated Immunopathology.

Cell Rep 2020 02;30(5):1585-1597.e6

Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg University of Mainz, 55131 Mainz, Germany. Electronic address:

Tumor-necrosis-factor-alpha-induced protein 3 (TNFAIP3), or A20, is a ubiquitin-modifying protein and negative regulator of canonical nuclear factor κB (NF-κB) signaling. Several single-nucleotide polymorphisms in TNFAIP3 are associated with autoimmune diseases, suggesting a role in tissue inflammation. While the role of A20 in peripheral immune cells has been well investigated, less is known about its role in the central nervous system (CNS). Here, we show that microglial A20 is crucial for maintaining brain homeostasis. Without microglial A20, CD8 T cells spontaneously infiltrate the CNS and acquire a viral response signature. The combination of infiltrating CD8 T cells and activated A20-deficient microglia leads to an increase in VGLUT1 terminals and frequency of spontaneous excitatory currents. Ultimately, A20-deficient microglia upregulate genes associated with the antiviral response and neurodegenerative diseases. Together, our data suggest that microglial A20 acts as a sensor for viral infection and a master regulator of CNS homeostasis.
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http://dx.doi.org/10.1016/j.celrep.2019.12.097DOI Listing
February 2020

Chronic Viral Infection Promotes Efficient Germinal Center B Cell Responses.

Cell Rep 2020 01;30(4):1013-1026.e7

Department of Biomedicine, Division of Experimental Virology, University of Basel, Haus Petersplatz, 4009 Basel, Switzerland. Electronic address:

Persistent viral infections subvert key elements of adaptive immunity. To compare germinal center (GC) B cell responses in chronic and acute lymphocytic choriomeningitis virus infection, we exploit activation-induced deaminase (AID) fate-reporter mice and perform adoptive B cell transfer experiments. Chronic infection yields GC B cell responses of higher cellularity than acute infections do, higher memory B cell and antibody secreting cell output for longer periods of time, a better representation of the late B cell repertoire in serum immunoglobulin, and higher titers of protective neutralizing antibodies. GC B cells of chronically infected mice are similarly hypermutated as those emerging from acute infection. They efficiently adapt to viral escape variants and even in hypermutation-impaired AID mutant mice, chronic infection selects for GC B cells with hypermutated B cell receptors (BCRs) and neutralizing antibody formation. These findings demonstrate that, unlike for CD8 T cells, chronic viral infection drives a functional, productive, and protective GC B cell response.
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http://dx.doi.org/10.1016/j.celrep.2019.12.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6996002PMC
January 2020

Initial Viral Inoculum Determines Kinapse-and Synapse-Like T Cell Motility in Reactive Lymph Nodes.

Front Immunol 2019 6;10:2086. Epub 2019 Sep 6.

Department of Oncology, Microbiology, and Immunology, University of Fribourg, Fribourg, Switzerland.

T cell activation in lymphoid tissue occurs through interactions with cognate peptide-major histocompatibility complex (pMHC)-presenting dendritic cells (DCs). Intravital imaging studies using peptide-pulsed DCs have uncovered that cognate pMHC levels imprint a wide range of dynamic contacts between these two cell types. T cell-DC interactions vary between transient, "kinapse-like" contacts at low to moderate pMHC levels to immediate "synapse-like" arrest at DCs displaying high pMHC levels. To date, it remains unclear whether this pattern is recapitulated when the immune system faces a replicative agent, such as a virus, at low and high inoculum. Here, we locally administered low and high inoculum of lymphocytic choriomeningitis virus (LCMV) in mice to follow activation parameters of Ag-specific CD4 and CD8 T cells in draining lymph nodes (LNs) during the first 72 h post infection. We correlated these data with kinapse- and synapse-like motility patterns of Ag-specific T cells obtained by intravital imaging of draining LNs. Our data show that initial viral inoculum controls immediate synapse-like T cell arrest vs. continuous kinapse-like motility. This remains the case when the viral inoculum and thus the inflammatory microenvironment in draining LNs remains identical but cognate pMHC levels vary. Our data imply that the Ag-processing capacity of draining LNs is equipped to rapidly present high levels of cognate pMHC when antigenic material is abundant. Our findings further suggest that widespread T cell arrest during the first 72 h of an antimicrobial immune responses is not required to trigger proliferation. In sum, T cells adapt their scanning behavior according to available antigen levels during viral infections, with dynamic changes in motility occurring before detectable expression of early activation markers.
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http://dx.doi.org/10.3389/fimmu.2019.02086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6743022PMC
October 2020

In Vivo Function of the Lipid Raft Protein Flotillin-1 during CD8 T Cell-Mediated Host Surveillance.

J Immunol 2019 11 23;203(9):2377-2387. Epub 2019 Sep 23.

Department of Oncology, Microbiology and Immunology, University of Fribourg, 1700 Fribourg, Switzerland;

Flotillin-1 (Flot1) is an evolutionary conserved, ubiquitously expressed lipid raft-associated scaffolding protein. Migration of Flot1-deficient neutrophils is impaired because of a decrease in myosin II-mediated contractility. Flot1 also accumulates in the uropod of polarized T cells, suggesting an analogous role in T cell migration. In this study, we analyzed morphology and migration parameters of murine wild-type and Flot1 CD8 T cells using in vitro assays and intravital two-photon microscopy of lymphoid and nonlymphoid tissues. Flot1 CD8 T cells displayed significant alterations in cell shape and motility parameters in vivo but showed comparable homing to lymphoid organs and intact in vitro migration to chemokines. Furthermore, their clonal expansion and infiltration into nonlymphoid tissues during primary and secondary antiviral immune responses was comparable to wild-type CD8 T cells. Taken together, Flot1 plays a detectable but unexpectedly minor role for CD8 T cell behavior under physiological conditions.
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http://dx.doi.org/10.4049/jimmunol.1900075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6820809PMC
November 2019

Cell-type-specific profiling of brain mitochondria reveals functional and molecular diversity.

Nat Neurosci 2019 10 9;22(10):1731-1742. Epub 2019 Sep 9.

Institute of Neuronal Cell Biology, Technical University of Munich, Munich, Germany.

Mitochondria vary in morphology and function in different tissues; however, little is known about their molecular diversity among cell types. Here we engineered MitoTag mice, which express a Cre recombinase-dependent green fluorescent protein targeted to the outer mitochondrial membrane, and developed an isolation approach to profile tagged mitochondria from defined cell types. We determined the mitochondrial proteome of the three major cerebellar cell types (Purkinje cells, granule cells and astrocytes) and identified hundreds of mitochondrial proteins that are differentially regulated. Thus, we provide markers of cell-type-specific mitochondria for the healthy and diseased mouse and human central nervous systems, including in amyotrophic lateral sclerosis and Alzheimer's disease. Based on proteomic predictions, we demonstrate that astrocytic mitochondria metabolize long-chain fatty acids more efficiently than neuronal mitochondria. We also characterize cell-type differences in mitochondrial calcium buffering via the mitochondrial calcium uniporter (Mcu) and identify regulator of microtubule dynamics protein 3 (Rmdn3) as a determinant of endoplasmic reticulum-mitochondria proximity in Purkinje cells. Our approach enables exploring mitochondrial diversity in many in vivo contexts.
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http://dx.doi.org/10.1038/s41593-019-0479-zDOI Listing
October 2019

Dendritic Cell Accumulation in the Gut and Central Nervous System Is Differentially Dependent on α4 Integrins.

J Immunol 2019 09 9;203(6):1417-1427. Epub 2019 Aug 9.

Abteilung für Experimentelle Neuroimmunologie, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany;

Homing of pathogenic CD4 T cells to the CNS is dependent on α4 integrins. However, it is uncertain whether α4 integrins are also required for the migration of dendritic cell (DC) subsets, which sample Ags from nonlymphoid tissues to present it to T cells. In this study, after genetic ablation of in DCs and monocytes in mice via the promoters of and (also known as LysM), respectively, the recruitment of α4 integrin-deficient conventional and plasmacytoid DCs to the CNS was unaffected, whereas α4 integrin-deficient, monocyte-derived DCs accumulated less efficiently in the CNS during experimental autoimmune encephalomyelitis in a competitive setting than their wild-type counterparts. In a noncompetitive setting, α4 integrin deficiency on monocyte-derived DCs was fully compensated. In contrast, in small intestine and colon, the fraction of α4 integrin-deficient CD11bCD103 DCs was selectively reduced in steady-state. Yet, T cell-mediated inflammation and host defense against were not impaired in the absence of α4 integrins on DCs. Thus, inflammatory conditions can promote an environment that is indifferent to α4 integrin expression by DCs.
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http://dx.doi.org/10.4049/jimmunol.1900468DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6731453PMC
September 2019

Brain-resident memory T cells generated early in life predispose to autoimmune disease in mice.

Sci Transl Med 2019 06;11(498)

Department of Pathology and Immunology, University of Geneva, 1211 Geneva, Switzerland.

Epidemiological studies associate viral infections during childhood with the risk of developing autoimmune disease during adulthood. However, the mechanistic link between these events remains elusive. We report that transient viral infection of the brain in early life, but not at a later age, precipitates brain autoimmune disease elicited by adoptive transfer of myelin-specific CD4 T cells at sites of previous infection in adult mice. Early-life infection of mouse brains imprinted a chronic inflammatory signature that consisted of brain-resident memory T cells expressing the chemokine (C-C motif) ligand 5 (CCL5). Blockade of CCL5 signaling via C-C chemokine receptor type 5 prevented the formation of brain lesions in a mouse model of autoimmune disease. In mouse and human brain, CCL5 T were located predominantly to sites of microglial activation. This study uncovers how transient brain viral infections in a critical window in life might leave persisting chemotactic cues and create a long-lived permissive environment for autoimmunity.
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http://dx.doi.org/10.1126/scitranslmed.aav5519DOI Listing
June 2019

TOX reinforces the phenotype and longevity of exhausted T cells in chronic viral infection.

Nature 2019 07 17;571(7764):265-269. Epub 2019 Jun 17.

Division of Animal Physiology and Immunology, School of Life Sciences Weihenstephan, Technical University of Munich, Freising, Germany.

Cytotoxic T cells are essential mediators of protective immunity to viral infection and malignant tumours and are a key target of immunotherapy approaches. However, prolonged exposure to cognate antigens often attenuates the effector capacity of T cells and limits their therapeutic potential. This process, known as T cell exhaustion or dysfunction, is manifested by epigenetically enforced changes in gene regulation that reduce the expression of cytokines and effector molecules and upregulate the expression of inhibitory receptors such as programmed cell-death 1 (PD-1). The underlying molecular mechanisms that induce and stabilize the phenotypic and functional features of exhausted T cells remain poorly understood. Here we report that the development and maintenance of populations of exhausted T cells in mice requires the thymocyte selection-associated high mobility group box (TOX) protein. TOX is induced by high antigen stimulation of the T cell receptor and correlates with the presence of an exhausted phenotype during chronic infections with lymphocytic choriomeningitis virus in mice and hepatitis C virus in humans. Removal of its DNA-binding domain reduces the expression of PD-1 at the mRNA and protein level, augments the production of cytokines and results in a more polyfunctional T cell phenotype. T cells with this deletion initially mediate increased effector function and cause more severe immunopathology, but ultimately undergo a massive decline in their quantity, notably among the subset of TCF-1 self-renewing T cells. Altogether, we show that TOX is a critical factor for the normal progression of T cell dysfunction and the maintenance of exhausted T cells during chronic infection, and provide a link between the suppression of effector function intrinsic to CD8 T cells and protection against immunopathology.
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http://dx.doi.org/10.1038/s41586-019-1326-9DOI Listing
July 2019

CD8 T cells induce cachexia during chronic viral infection.

Nat Immunol 2019 06 20;20(6):701-710. Epub 2019 May 20.

CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria.

Cachexia represents a leading cause of morbidity and mortality in various cancers, chronic inflammation and infections. Understanding of the mechanisms that drive cachexia has remained limited, especially for infection-associated cachexia (IAC). In the present paper we describe a model of reversible cachexia in mice with chronic viral infection and identify an essential role for CD8 T cells in IAC. Cytokines linked to cancer-associated cachexia did not contribute to IAC. Instead, virus-specific CD8 T cells caused morphologic and molecular changes in the adipose tissue, which led to depletion of lipid stores. These changes occurred at a time point that preceded the peak of the CD8 T cell response and required T cell-intrinsic type I interferon signaling and antigen-specific priming. Our results link systemic antiviral immune responses to adipose-tissue remodeling and reveal an underappreciated role of CD8 T cells in IAC.
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http://dx.doi.org/10.1038/s41590-019-0397-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6531346PMC
June 2019

Bassoon proteinopathy drives neurodegeneration in multiple sclerosis.

Nat Neurosci 2019 06 22;22(6):887-896. Epub 2019 Apr 22.

Institut für Neuroimmunologie und Multiple Sklerose, Zentrum für Molekulare Neurobiologie Hamburg, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.

Multiple sclerosis (MS) is characterized by inflammatory insults that drive neuroaxonal injury. However, knowledge about neuron-intrinsic responses to inflammation is limited. By leveraging neuron-specific messenger RNA profiling, we found that neuroinflammation leads to induction and toxic accumulation of the synaptic protein bassoon (Bsn) in the neuronal somata of mice and patients with MS. Neuronal overexpression of Bsn in flies resulted in reduction of lifespan, while genetic disruption of Bsn protected mice from inflammation-induced neuroaxonal injury. Notably, pharmacological proteasome activation boosted the clearance of accumulated Bsn and enhanced neuronal survival. Our study demonstrates that neuroinflammation initiates toxic protein accumulation in neuronal somata and advocates proteasome activation as a potential remedy.
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http://dx.doi.org/10.1038/s41593-019-0385-4DOI Listing
June 2019

Phase I/II trial testing safety and immunogenicity of the multipeptide IMA950/poly-ICLC vaccine in newly diagnosed adult malignant astrocytoma patients.

Neuro Oncol 2019 07;21(7):923-933

Department of Oncology, Clinical Research Unit, Dr Dubois Ferrière Dinu Lipatti Research Foundation, Geneva University Hospital, Geneva, Switzerland.

Background: Peptide vaccines offer the opportunity to elicit glioma-specific T cells with tumor killing ability. Using antigens eluted from the surface of glioblastoma samples, we designed a phase I/II study to test safety and immunogenicity of the IMA950 multipeptide vaccine adjuvanted with poly-ICLC (polyinosinic-polycytidylic acid stabilized with polylysine and carboxymethylcellulose) in human leukocyte antigen A2+ glioma patients.

Methods: Adult patients with newly diagnosed glioblastoma (n = 16) and grade III astrocytoma (n = 3) were treated with radiochemotherapy followed by IMA950/poly-ICLC vaccination. The first 6 patients received IMA950 (9 major histocompatibility complex [MHC] class I and 2 MHC class II peptides) intradermally and poly-ICLC intramuscularly (i.m.). After protocol amendment, IMA950 and poly-ICLC were mixed and injected subcutaneously (n = 7) or i.m. (n = 6). Primary endpoints were safety and immunogenicity. Secondary endpoints were overall survival, progression-free survival at 6 and 9 months, and vaccine-specific peripheral cluster of differentiation (CD)4 and CD8 T-cell responses.

Results: The IMA950/poly-ICLC vaccine was safe and well tolerated. Four patients presented cerebral edema with rapid recovery. For the first 6 patients, vaccine-induced CD8 T-cell responses were restricted to a single peptide and CD4 responses were absent. After optimization of vaccine formulation, we observed multipeptide CD8 and sustained T helper 1 CD4 T-cell responses. For the entire cohort, CD8 T-cell responses to a single or multiple peptides were observed in 63.2% and 36.8% of patients, respectively. Median overall survival was 19 months for glioblastoma patients.

Conclusion: We provide, in a clinical trial, using cell surface-presented antigens, insights into optimization of vaccines generating effector T cells for glioma patients.

Trial Registration: Clinicaltrials.gov NCT01920191.
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http://dx.doi.org/10.1093/neuonc/noz040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6620642PMC
July 2019

Resident-Memory T Cells in Tissue-Restricted Immune Responses: For Better or Worse?

Front Immunol 2018 30;9:2827. Epub 2018 Nov 30.

Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland.

Tissue-resident-memory CD8+ T cells (T) have been described as a non-circulating memory T cell subset that persists at sites of previous infection. While T in all non-lymphoid organs probably share a core signature differentiation pathway, certain aspects of their maintenance and effector functions may vary. It is well-established that T provide long-lived protective immunity through immediate effector function and accelerated recruitment of circulating immune cells. Besides immune defense against pathogens, other immunological roles of T are less well-studied. Likewise, evidence of a putative detrimental role of T for inflammatory diseases is only beginning to emerge. In this review, we discuss the protective and harmful role of T in organ-specific immunity and immunopathology as well as prospective implications for immunomodulatory therapy.
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http://dx.doi.org/10.3389/fimmu.2018.02827DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6284001PMC
October 2019

Myeloid-derived suppressor cells control B cell accumulation in the central nervous system during autoimmunity.

Nat Immunol 2018 12 29;19(12):1341-1351. Epub 2018 Oct 29.

Department of Experimental Neuroimmunology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.

Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) have been characterized in the context of malignancies. Here we show that PMN-MDSCs can restrain B cell accumulation during central nervous system (CNS) autoimmunity. Ly6G cells were recruited to the CNS during experimental autoimmune encephalomyelitis (EAE), interacted with B cells that produced the cytokines GM-CSF and interleukin-6 (IL-6), and acquired properties of PMN-MDSCs in the CNS in a manner dependent on the signal transducer STAT3. Depletion of Ly6G cells or dysfunction of Ly6G cells through conditional ablation of STAT3 led to the selective accumulation of GM-CSF-producing B cells in the CNS compartment, which in turn promoted an activated microglial phenotype and lack of recovery from EAE. The frequency of CD138 B cells in the cerebrospinal fluid (CSF) of human subjects with multiple sclerosis was negatively correlated with the frequency of PMN-MDSCs in the CSF. Thus PMN-MDSCs might selectively control the accumulation and cytokine secretion of B cells in the inflamed CNS.
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http://dx.doi.org/10.1038/s41590-018-0237-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6241855PMC
December 2018

Functional Gut Microbiota Remodeling Contributes to the Caloric Restriction-Induced Metabolic Improvements.

Cell Metab 2018 12 30;28(6):907-921.e7. Epub 2018 Aug 30.

Department of Cell Physiology and Metabolism, Centre Médical Universitaire, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; Diabetes Centre, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; Institute of Genetics and Genomics in Geneva, University of Geneva, 1211 Geneva, Switzerland. Electronic address:

Caloric restriction (CR) stimulates development of functional beige fat and extends healthy lifespan. Here we show that compositional and functional changes in the gut microbiota contribute to a number of CR-induced metabolic improvements and promote fat browning. Mechanistically, these effects are linked to a lower expression of the key bacterial enzymes necessary for the lipid A biosynthesis, a critical lipopolysaccharide (LPS) building component. The decreased LPS dictates the tone of the innate immune response during CR, leading to increased eosinophil infiltration and anti-inflammatory macrophage polarization in fat of the CR animals. Genetic and pharmacological suppression of the LPS-TLR4 pathway or transplantation with Tlr4 bone-marrow-derived hematopoietic cells increases beige fat development and ameliorates diet-induced fatty liver, while Tlr4 or microbiota-depleted mice are resistant to further CR-stimulated metabolic alterations. These data reveal signals critical for our understanding of the microbiota-fat signaling axis during CR and provide potential new anti-obesity therapeutics.
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http://dx.doi.org/10.1016/j.cmet.2018.08.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288182PMC
December 2018