Extended Freeze-Dried BCG Instructed pDCs Induce Suppressive Tregs and Dampen EAE

Several clinical observations have shown that Bacillus Calmette-Guérin (BCG) vaccine has beneficial impact on patients suffering from different chronic inflammatory diseases. Here we evaluated whether BCG inactivated by Extended Freeze-Drying (EFD) which circumvents all the side effects linked to the live bacteria, could influence the development of experimental autoimmune encephalomyelitis (EAE), a mouse model for Multiple Sclerosis. EFD BCG strongly attenuates inflammation, both systemically and at the central nervous system (CNS) level, alleviating EAE. Mechanistically, EFD BCG directly impacts the phenotype of plasmacytoid dendritic cells (pDCs), and promotes their ability to induce suppressive IL-10 secreting regulatory T cells (Tregs) that inhibit encephalitogenic CD4+ T cells. When co-cultured with human allogenic naive CD4+ T cells, EFD BCG exposed human pDCs similarly induce the differentiation of IL-10 producing Tregs. Our study provides evidence that EFD BCG could be used as an immunomodulator of encephalitogenic T cells in multiple sclerosis patients

Ribosome-Targeting Antibiotics Impair T Cell Effector Function and Ameliorate Autoimmunity by Blocking Mitochondrial Protein Synthesis

While antibiotics are intended to specifically target bacteria, most are known to affect host cell physiology. In addition, some antibiotic classes are reported as immunosuppressive for reasons that remain unclear. Here, we show that Linezolid, a ribosomal-targeting antibiotic (RAbo), effectively blocked the course of a T cell mediated autoimmune disease. Linezolid and other RAbos were strong inhibitors of T helper-17 cell effector function in vitro, showing that this effect was independent of their antibiotic activity. Perturbing mitochondria! translation in differentiating T cells, either with RAbos or through the inhibition of mitochondria! elongation factor G1 (mEF-G1) progressively compromised the integrity of the electron transport chain. Ultimately, this led to deficient oxidative phosphorylation, diminishing nicotinamide adenine dinucleotide concentrations and impairing cytokine production in differentiating T cells. In accordance, mice lacking mEF-G1 in T cells were protected from experimental autoimmune encephalomyelitis, demonstrating that this pathway is crucial in maintaining T cell function and pathogenicity

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly

Tolerogenic functions of plasmacytoid dendritic cells in T cell-medaited CNS autoimmunity

T cell lymphocytes play an essential role in the adaptive immunity. They arise from the hematopoietic compartment and reach the thymus, where they achieve their development through specialized maturation and selection steps. Immune system comprises specific and complex mechanisms in the thymus and the periphery aiming at preventing the generation and the survival of self-reactive T cells that could lead to autoimmune disorders. These mechanisms are known as central and peripheral tolerance and rely on different cellular actors such as medullary thymic epithelial cells (mTECs), dendritic cells (DCs), lymph node stromal cells (LNSCs) and regulatory T and B cells. Self-reactive T cells escaping thymic central tolerance are kept in check in the periphery through specific mechanisms that include T cell anergy, T cell deletion and Treg induction. Although conventional DCs (cDCs) have been first in line in mediating peripheral tolerance, increasing evidence demonstrates the contribution of other actors such as plasmacytoid dendritic cells (pDCs) in this process. pDCs are important linkers of the innate and adaptive immunity. They are characterized by their ability to secrete pro-inflammatory cytokines and large amount of type I interferon (IFN-I) upon pathogenic infections, but also express major Histocompatibility complex (MHC) and costimulatory molecules enabling them to interact with T cells. pDCs have been involved in the control of infections, but are also important actors of peripheral tolerance. The diversity of their functions, depending on the context in which they will evolve, has associated pDCs to pro-immunogenic and tolerogenic scopes. In the lab, we are principally interested in the contribution of pDCs in Multiple sclerosis, a progressive inflammatory demyelinating disease of the central nervous system (CNS). To address the role of pDCs in MS, we performed our studies in the murine model of Experimental autoimmune encephalomyelitis (EAE). Using genetically modified mice harbouring specific abrogation of Ag-presenting function in pDCs, my co-workers previously demonstrated that myelin Ag presentation by pDCs promotes the expansion of regulatory T cells (Tregs) that inhibit encephalitogenic TH1 and TH17 cell priming in secondary lymphoid organs (SLOs). In this manuscript I report our recent findings supporting that pDCs display tolerogenic functions during the priming and the effector phase of EAE development and are able to control and dampen the disease. The first study investigates the interplays between pDCs and Tregs and shows that Ag-specific MHCII interactions with Tregs licenced tolerogenic features in steady-state pDCs by inducing their expression of the indoleamine-2,3 dioxygenase (IDO1). In EAE context, Treg-educated IDO+ pDCs are required to confer suppressive functions to Tregs which promote the inhibition of encephalitogenic T cell priming in draining LNs, resulting in attenuated EAE. In the second study, we explore the therapeutic effect of pDCs transfer in EAE mice after disease onset. We show that the transfer of immature MOG35-55 pre-loaded pDCs during EAE acute phase leads to substantial reduction of CNS inflammation and significant amelioration of disease clinical scores. We demonstrate that pDC-protection relies on the massive recruitment of endogenous immature pDCs in the inflamed spinal cord via the Chemerine/CMKLR1 axis. Endogenous pDC recruitment is required to down-modulate CNS inflammation, encephalitogenic TH1 and TH17 cell responses and EAE severity. Overall this work supports previous findings showing the importance of pDCs in the regulation of CNS autoimmunity and unravel these cells for potential use, by targeting different particular functions, in the development of future therapies to treat MS patients

Oxysterols regulate CD4+ T cell trafficking during experimental autoimmune encephalomyelitis

Perturbation of steroids pathways has been linked to inflammation and chronic diseases. Oxysterols, oxidised forms of cholesterol, are essential for bile synthesis biosynthesis and sterol transportation. In addition to their basic metabolic properties, oxysterols modulate immune response and control trafficking of immune cells such as B lymphocytes and macrophages. Furthermore, serum oxysterols levels have been proposed as putative candidate biomarkers for neurological diseases such as Multiple sclerosis (MS). The enzyme cholesterol 25 hydroxylase (ch25h) is the rate limiting step to synthetize the oxysterol 7,25-dihydroxycholesterol (725-OHC) from cholesterol. We here report, using the MS murine model experimental autoimmune encephalomyelitis (EAE), that deletion of ch25h attenuated EAE disease course by dampening pathogenic T lymphocytes trafficking to the central nervous system (CNS). While systemic immune response is preserved in the absence of ch25h, IL-17 producing CD4+ T helper (TH17) cells accumulate in the draining lymph nodes. Furthermore, TH17 cells migrate towards 725-OHC in an Epstein-Barr virus-induced G-protein coupled receptor 2 (ebi2) dependent-manner. Collectively, our results reveal a critical involvement for oxysterols in migration of distinct subset of CD4+ T lymphocytes thus supporting a pro-inflammatory role for oxysterols during EAE

Oxysterols regulate encephalitogenic CD4⁺ T cell trafficking during central nervous system autoimmunity

Perturbation of steroids pathways is linked to inflammation and chronic diseases, however the underlying mechanism remains unclear. Oxysterols, oxidized forms of cholesterol, are not only essential for bile synthesis and sterol transportation but have recently been shown to contribute to the immune response. In addition, serum oxysterols levels have been proposed as suitable candidate biomarkers for neurological diseases such as multiple sclerosis (MS). However how oxysterols modulate adaptive immunity is unknown and their functions in autoimmunity have not been investigated. The enzyme cholesterol 25 hydroxylase (Ch25h) is the rate limiting step to synthesize the oxysterol 7α,25-dihydroxycholesterol (7α,25-OHC) from cholesterol. We here report, using the MS murine model experimental autoimmune encephalomyelitis (EAE), that Ch25h deletion significantly attenuated EAE disease course by limiting trafficking of pathogenic CD4(+) T lymphocytes to the central nervous system (CNS). Mechanistically, we show a critical involvement for oxysterols in recruiting leukocytes into inflamed tissues and propose that 7α,25-OHC preferentially promotes the migration of activated CD44(+)CD4(+) T cells by binding the G protein-coupled receptor called Epstein-Barr virus induced gene 2 (EBI2). Collectively, our results support a pro-inflammatory role for oxysterols during EAE and identify oxysterols as a potential therapeutic target to treat autoimmune diseases

Ag-Presenting CpG-Activated pDCs Prime Th17 Cells That Induce Tumor Regression

Plasmacytoid dendritic cells (pDC) rapidly and massively produce type I IFN and other inflammatory cytokines in response to foreign nucleic acids, thereby indirectly influencing T-cell responses. Moreover, antigen (Ag)-presenting pDCs directly regulate T-cell differentiation. Depending on the immune environment, pDCs exhibit either tolerogenic or immunogenic properties. Here, we show that CpG-activated pDCs promote efficient Th17 differentiation. Indeed, Th17 responses are defective in mice selectively lacking MHCII on pDCs upon antigenic challenge. Importantly, in those mice, the frequency of Th17 cells infiltrating solid tumors is impaired. As a result, the recruitment of infiltrating leukocytes in tumors, including tumor-specific cytotoxic T lymphocytes (CTL), is altered and results in increased tumor growth. Importantly, following immunization with tumor Ag and CpG-B, MHCII-restricted Ag presentation by pDCs promotes the differentiation of antitumor Th17 cells that induce intratumor CTL recruitment and subsequent regression of established tumors. Our results highlight a new role for Ag presenting activated pDCs in promoting the development of Th17 cells and impacting on antitumor immunity. Cancer Res; 74(22); 6430-40. ©2014 AACR

pDC therapy induces recovery from EAE by recruiting endogenous pDC to sites of CNS inflammation

Plasmacytoid dendritic cells (pDCs) exhibit both innate and adaptive functions. In particular they are the main source of type I IFNs and directly impact T cell responses through antigen presentation. We have previously demonstrated that during experimental autoimmune encephalomyelitis (EAE) initiation, myelin-antigen presentation by pDCs is associated with suppressive Treg development and results in attenuated EAE. Here, we show that pDCs transferred during acute disease phase confer recovery from EAE. Clinical improvement is associated with migration of injected pDCs into inflamed CNS and is dependent on the subsequent and selective chemerin-mediated recruitment of endogenous pDCs to the CNS. The protective effect requires pDC pre-loading with myelin antigen, and is associated with the modulation of CNS-infiltrating pDC phenotype and inhibition of CNS encephalitogenic T cells. This study may pave the way for novel pDC-based cell therapies in autoimmune diseases, aiming at specifically modulating pathogenic cells that induce and sustain autoimmune inflammation

IDO-orchestrated crosstalk between pDCs and Tregs inhibits autoimmunity

Plasmacytoid dendritic cells (pDCs) have been shown to both mediate and prevent autoimmunity, and the regulation of their immunogenic versus tolerogenic functions remains incompletely understood. Here we demonstrate that, compared to other cells, pDCs are the major expressors of Indoleamine-2,3-dioxygenase (IDO) in steady-state lymph nodes (LNs). IDO expression by LN pDCs was closely dependent on MHCII-mediated, antigen-dependent, interactions with Treg. We further established that IDO production by pDCs was necessary to confer suppressive function to Tregs. During EAE development, IDO expression by pDCs was required for the generation of Tregs capable of dampening the priming of encephalitogenic T cell and disease severity. Thus, we describe a novel crosstalk between pDCs and Tregs: Tregs shape tolerogenic functions of pDCs prior to inflammation, such that pDCs in turn, promote Treg suppressive functions during autoimmunity