Microglial autophagy-associated phagocytosis is essential for recovery from neuroinflammation

Multiple sclerosis (MS) is a leading cause of incurable progressive disability in young adults caused by inflammation and neurodegeneration in the central nervous system (CNS). The capacity of microglia to clear tissue debris is essential for maintaining and restoring CNS homeostasis. This capacity diminishes with age, and age strongly associates with MS disease progression, although the underlying mechanisms are still largely elusive. Here, we demonstrate that the recovery from CNS inflammation in a murine model of MS is dependent on the ability of microglia to clear tissue debris. Microglia-specific deletion of the autophagy regulator Atg7, but not the canonical macroautophagy protein Ulk1, led to increased intracellular accumulation of phagocytosed myelin and progressive MS-like disease. This impairment correlated with a microglial phenotype previously associated with neurodegenerative pathologies. Moreover, Atg7-deficient microglia showed notable transcriptional and functional similarities to microglia from aged wild-type mice that were also unable to clear myelin and recover from disease. In contrast, induction of autophagy in aged mice using the disaccharide trehalose found in plants and fungi led to functional myelin clearance and disease remission. Our results demonstrate that a noncanonical form of autophagy in microglia is responsible for myelin degradation and clearance leading to recovery from MS-like disease and that boosting this process has a therapeutic potential for age-related neuroinflammatory conditions.Swedish Research CouncilSwedish Brain FoundationSwedish Association for Persons with Neurological DisabilitiesStockholm County Council (ALF project)AstraZeneca (AstraZeneca-Science for Life Laboratory collaboration)European Union Horizon 2020/European Research Council Consolidator Grant (Epi4MS)Knut and Alice Wallenbergs FoundationMargeretha af Ugglas FoundationAlltid Litt SterkereFoundation of Swedish MS researchNEURO SwedenKarolinska InstitutetAccepte

Immunological consequences of Epstein-Barr Virus replication

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus involved in the pathogenesis of a wide spectrum of malignant and non-malignant diseases. In healthy EBV carriers, the virus is believed to infect two major cellular targets - B lymphocytes and epithelial cells. While EBV latency is established predominantly, if not exclusively, in B-lymphocytes, virus replication can take place both in B cells and epithelial cells. Lytic replication ensures virus transmission to new carriers and replenishes the cellular reservoirs of virus persistence. The generally asymptomatic and harmless persistence of EBV relies on a tightly controlled immune response and distinct modes of virus/cell interactions observed at different stages of EBV life cycle. The aim of this thesis was to characterize the mutual influence of the host immune system and EBV at the replicative stage of virus infection. We showed that EBV enters monocytes and inhibits their differentiation into dendritic cells (DCs) without the need of viral gene expression. The sensitivity of the cells to virus-induced apoptosis progressively decreases along the process of DC maturation and is strongly dependent on the cell type in which the virus replicated before infecting DC precursors, since epithelial-cells derived viruses exhibited a significantly stronger pro-apoptotic activity than their B cell-derived counterparts. The capacity of the virus to suppress DC development might help in delaying the establishment of EBV specific immunity before the pool of infected B cells reaches the size sufficient for long-term virus persistence. During virus replication, both B cells and epithelial cells may escape recognition by cytotoxic CD8+ T cells through downregulation of MHC class I molecules. Our work demonstrated that MHC class I heavy-chain and beta2m mRNA and protein synthesis are inhibited during EBV replication. Several other characteristic changes observed in the MHC class I processing and presentation pathway during the lytic cycle were recapitulated by chemical inhibition of protein synthesis. These results were recently confirmed by others and the viral protein responsible for host-cell global protein synthesis shutdown was shown to be encoded by the BGLF5 open reading frame of the EBV genome. Triggering of receptors of the tumor necrosis factor (TNF) superfamily participates both in determining the fate of B-lymphocytes during the process of their differentiation and in immunologic clearance of virus infected targets. Initiation of EBV lytic cycle counteracted sensitization to death induced by TNF-related apoptosis-inducing ligand (TRAIL) that resulted from B-cell receptor (BCR) triggering in Burkitt s lymphoma cells. Differential modulation of death-transmitting and decoy TRAIL receptors was associated with sensitization to TRAIL in response to BCR-triggering or protection from TRAIL by EBV lytic cycle. Interference with TRAIL-mediated checkpoints in B-cell differentiation may account for the involvement of EBV in autoimmune diseases. Decreased sensitivity to TRAIL may also protect EBV infected cells from recognition by CTL and NK-cells. B-cell homeostasis is severely perturbed during malaria infection. We showed that the CIDR1á domain of P. falciparum erythrocyte membrane protein 1 (PfEMP1), a multiadhesive protein expressed during the erythrocytic phase of the parasite life cycle, binds to B cells and induces EBV replication. This might partly explain the increased EBV viral load during malaria infection and the increased risk of B cell immortalization in the ontogenesis of endemic Burkitt s lymphoma. Results presented in this thesis strengthen the notion that EBV replication actively modulates the functioning of the immune system at different levels through complex interactions of viral products with several types of cells and contributes to immune suppression, autoimmunity and tumorogenesis through a number of mechanisms whose details require further characterization. Research lines defined by this work may lead to new approaches towards management of EBV associated diseases

Inhibition of Heavy Chain and β(2)-Microglobulin Synthesis as a Mechanism of Major Histocompatibility Complex Class I Downregulation during Epstein-Barr Virus Replication

The mechanisms of major histocompatibility complex (MHC) class I downregulation during Epstein-Barr virus (EBV) replication are not well characterized. Here we show that in several cell lines infected with a recombinant EBV strain encoding green fluorescent protein (GFP), the virus lytic cycle coincides with GFP expression, which thus can be used as a marker of virus replication. EBV replication resulted in downregulation of MHC class II and all classical MHC class I alleles independently of viral DNA synthesis or late gene expression. Although assembled MHC class I complexes, the total pool of heavy chains, and β(2)-microglobulin (β(2)m) were significantly downregulated, free class I heavy chains were stabilized at the surface of cells replicating EBV. Calnexin expression was increased in GFP(+) cells, and calnexin and calreticulin accumulated at the cell surface that could contribute to the stabilization of class I heavy chains. Decreased expression levels of another chaperone, ERp57, and TAP2, a transporter associated with antigen processing and presentation, correlated with delayed kinetics of MHC class I maturation. Levels of both class I heavy chain and β(2)m mRNA were reduced, and metabolic labeling experiments demonstrated a very low rate of class I heavy chain synthesis in lytically infected cells. MHC class I and MHC class II downregulation was mimicked by pharmacological inhibition of protein synthesis in latently infected cells. Our data suggest that although several mechanisms may contribute to MHC class I downregulation in the course of EBV replication, inhibition of MHC class I synthesis plays the primary role in the process

Approximation by harmonic functions Lecture

SIGLETIB: RO 1945 (115) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Cross-reactive EBNA1 immunity targets alpha-crystallin B and is associated with multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system, for which and Epstein-Barr virus (EBV) infection is a likely prerequisite. Due to the homology between Epstein-Barr nuclear antigen 1 (EBNA1) and alpha-crystallin B (CRYAB), we examined antibody reactivity to EBNA1 and CRYAB peptide libraries in 713 persons with MS (pwMS) and 722 matched controls (Con). Antibody response to CRYAB amino acids 7 to 16 was associated with MS (OR = 2.0), and combination of high EBNA1 responses with CRYAB positivity markedly in-creased disease risk (OR = 9.0). Blocking experiments revealed antibody cross-reactivity between the homolo-gous EBNA1 and CRYAB epitopes. Evidence for T cell cross-reactivity was obtained in mice between EBNA1 and CRYAB, and increased CRYAB and EBNA1 CD4+ T cell responses were detected in natalizumab-treated pwMS. This study provides evidence for antibody cross-reactivity between EBNA1 and CRYAB and points to a similar cross-reactivity in T cells, further demonstrating the role of EBV adaptive immune responses in MS development

Identification of four novel T cell autoantigens and personal autoreactive profiles in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS), in which pathological T cells, likely autoimmune, play a key role. Despite its central importance, the autoantigen repertoire remains largely uncharacterized. Using a novel in vitro antigen delivery method combined with the Human Protein Atlas library, we screened for T cell autoreactivity against 63 CNS-expressed proteins. We identified four previously unreported autoantigens in MS: fatty acid-binding protein 7, prokineticin-2, reticulon-3, and synaptosomal-associated protein 91, which were verified to induce interferon-gamma responses in MS in two cohorts. Autoreactive profiles were heterogeneous, and reactivity to several autoantigens was MS-selective. Autoreactive T cells were predominantly CD4(+) and human leukocyte antigen-DR restricted. Mouse immunization induced antigen-specific responses and CNS leukocyte infiltration. This represents one of the largest systematic efforts to date in the search for MS autoantigens, demonstrates the heterogeneity of autoreactive profiles, and highlights promising targets for future diagnostic tools and immunomodulatory therapies in MS

Homomorphisms and Ramsey properties of antimatroids

SIGLEBibliothek Weltwirtschaft Kiel C132,202 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Combined sequence-based and genetic mapping analysis of complex traits in outbred rats

<p>Genetic mapping on fully sequenced individuals is transforming understanding of the relationship between molecular variation and variation in complex traits. Here we report a combined sequence and genetic mapping analysis in outbred rats that maps 355 quantitative trait loci for 122 phenotypes. We identify 35 causal genes involved in 31 phenotypes, implicating new genes in models of anxiety, heart disease and multiple sclerosis. The relationship between sequence and genetic variation is unexpectedly complex: at approximately 40% of quantitative trait loci, a single sequence variant cannot account for the phenotypic effect. Using comparable sequence and mapping data from mice, we show that the extent and spatial pattern of variation in inbred rats differ substantially from those of inbred mice and that the genetic variants in orthologous genes rarely contribute to the same phenotype in both species.</p>