CD40L protects against mouse hepatitis virus-induced neuroinflammatory demyelination.

Neurotropic mouse hepatitis virus (MHV-A59/RSA59) infection in mice induces acute neuroinflammation due to direct neural cell dystrophy, which proceeds with demyelination with or without axonal loss, the pathological hallmarks of human neurological disease, Multiple sclerosis (MS). Recent studies in the RSA59-induced neuroinflammation model of MS showed a protective role of CNS-infiltrating CD4+ T cells compared to their pathogenic role in the autoimmune model. The current study further investigated the molecular nexus between CD4+ T cell-expressed CD40Ligand and microglia/macrophage-expressed CD40 using CD40L-/- mice. Results demonstrate CD40L expression in the CNS is modulated upon RSA59 infection. We show evidence that CD40L-/- mice are more susceptible to RSA59 induced disease due to reduced microglia/macrophage activation and significantly dampened effector CD4+ T recruitment to the CNS on day 10 p.i. Additionally, CD40L-/- mice exhibited severe demyelination mediated by phagocytic microglia/macrophages, axonal loss, and persistent poliomyelitis during chronic infection, indicating CD40-CD40L as host-protective against RSA59-induced demyelination. This suggests a novel target in designing prophylaxis for virus-induced demyelination and axonal degeneration, in contrast to immunosuppression which holds only for autoimmune mechanisms of inflammatory demyelination.

Anti-MAG neuropathy: From biology to clinical management.

The acquired chronic demyelinating neuropathies include a growing number of disease entities that have characteristic, often overlapping, clinical presentations, mediated by distinct immune mechanisms, and responding to different therapies. After the discovery in the early 1980s, that the myelin associated glycoprotein (MAG) is a target antigen in an autoimmune demyelinating neuropathy, assays to measure the presence of anti-MAG antibodies were used as the basis to diagnose the anti-MAG neuropathy. The route was open for describing the clinical characteristics of this new entity as a chronic distal large fiber sensorimotor neuropathy, for studying its pathogenesis and devising specific treatment strategies. The initial use of chemotherapeutic agents was replaced by the introduction in the late 1990s of rituximab, a monoclonal antibody against CD20+ B-cells. Since then, other anti-B cells agents have been introduced. Recently a novel antigen-specific immunotherapy neutralizing the anti-MAG antibodies with a carbohydrate-based ligand mimicking the natural HNK-1 glycoepitope has been described.

Immune response to dermatomyositis-specific autoantigen, transcriptional intermediary factor 1γ can result in experimental myositis.

OBJECTIVES: To investigate whether autoimmunity to transcriptional intermediary factor 1 (TIF1)γ, a ubiquitous nuclear autoantigen for myositis-specific autoantibodies detected in patients with dermatomyositis (DM) is pathogenetic for inflammatory myopathy. METHODS: Wild-type, ß2-microglobulin-null, perforin-null, Igµ-null and interferon α/ß receptor (IFNAR)-null mice were immunised with recombinant human TIF1γ whole protein. A thymidine incorporation assay was performed using lymph node T cells from TIF1γ-immunised mice. Plasma was analysed using immunoprecipitation followed by western blot analysis and enzyme-linked immunosorbent assays. Femoral muscles were histologically and immunohistochemically evaluated. CD8+ or CD4+ T cells isolated from lymph node T cells or IgG purified from plasma were adoptively transferred to naïve mice. TIF1γ-immunised mice were treated with anti-CD8 depleting antibody and a Janus kinase inhibitor, tofacitinib. RESULTS: Immunisation with TIF1γ-induced experimental myositis presenting with necrosis/atrophy of muscle fibres accompanied by CD8+ T cell infiltration successfully in wild-type mice, in which TIF1γ-specific T cells and antihuman and murine TIF1γ IgG antibodies were detected. The incidence and severity of myositis were significantly lower in ß2-microglobulin-null, perforin-null, CD8-depleted or IFNAR-null mice, while Igµ-null mice developed myositis normally. Adoptive transfer of CD8+ T cells induced myositis in recipients, while transfer of CD4+ T cells or IgG did not. Treatment with tofacitinib inhibited TIF1γ-induced myositis. CONCLUSIONS: Here we show that TIF1γ is immunogenic enough to cause experimental myositis, in which CD8+ T cells and type I interferons, but not CD4+ T cells, B cells or antibodies, are required. This murine model would be a tool for understanding the pathologies of DM.

Regulated Tristetraprolin Overexpression Dampens the Development and Pathogenesis of Experimental Autoimmune Uveitis.

Non-infectious uveitis, a common cause of blindness in man, is often mediated by autoimmunity, a process in which cytokines play major roles. The biosynthesis and secretion of pro-inflammatory cytokines are regulated in part by tristetraprolin (TTP), an endogenous anti-inflammatory protein that acts by binding directly to specific sequence motifs in the 3'-untranslated regions of target mRNAs, promoting their turnover, and inhibiting synthesis of their encoded proteins. We recently developed a TTP-overexpressing mouse (TTPΔARE) by deleting an AU-rich element (ARE) instability motif from the TTP mRNA, resulting in increased accumulation of TTP mRNA and protein throughout the animal. Here, we show that homozygous TTPΔARE mice are resistant to the induction of experimental autoimmune uveitis (EAU) induced by interphotoreceptor retinoid-binding protein (IRBP), an established model for human autoimmune (noninfectious) uveitis. Lymphocytes from TTPΔARE mice produced lower levels of the pro-inflammatory cytokines IFN-γ, IL-17, IL-6, and TNFα than wild type (WT) mice. TTPΔARE mice also produced lower titers of antibodies against the uveitogenic protein. In contrast, TTPΔARE mice produced higher levels of the anti-inflammatory cytokine IL-10, and had higher frequencies of regulatory T-cells, which, moreover, displayed a moderately higher per-cell regulatory ability. Heterozygous mice developed EAU and associated immunological responses at levels intermediate between homozygous TTPΔARE mice and WT controls. TTPΔARE mice were able, however, to develop EAU following adoptive transfer of activated WT T-cells specific to IRBP peptide 651-670, and naïve T-cells from TTPΔARE mice could be activated by antibodies to CD3/CD28. Importantly, TTPΔARE antigen presenting cells were significantly less efficient compared to WT in priming naïve T cells, suggesting that this feature plays a major role in the dampened immune responses of the TTPΔARE mice. Our observations demonstrate that elevated systemic levels of TTP can inhibit the pathogenic processes involved in EAU, and suggest the possible use of TTP-based treatments in humans with uveitis and other autoimmune conditions.

Blocking LFA-1 Aggravates Cardiac Inflammation in Experimental Autoimmune Myocarditis.

The lymphocyte function-associated antigen 1 (LFA-1) is a member of the beta2-integrin family and plays a pivotal role for T cell activation and leukocyte trafficking under inflammatory conditions. Blocking LFA-1 has reduced or aggravated inflammation depending on the inflammation model. To investigate the effect of LFA-1 in myocarditis, mice with experimental autoimmune myocarditis (EAM) were treated with a function blocking anti-LFA-1 antibody from day 1 of disease until day 21, the peak of inflammation. Cardiac inflammation was evaluated by measuring infiltration of leukocytes into the inflamed cardiac tissue using histology and flow cytometry and was assessed by analysis of the heart weight/body weight ratio. LFA-1 antibody treatment severely enhanced leukocyte infiltration, in particular infiltration of CD11b+ monocytes, F4/80+ macrophages, CD4+ T cells, Ly6G+ neutrophils, and CD133+ progenitor cells at peak of inflammation which was accompanied by an increased heart weight/body weight ratio. Thus, blocking LFA-1 starting at the time of immunization severely aggravated acute cardiac inflammation in the EAM model.

Low-Dose Subcutaneous Anti-CD20 Treatment Depletes Disease Relevant B Cell Subsets and Attenuates Neuroinflammation.

To explore the B cell depleting capacity of a low-dose (20 µg) subcutaneous mouse anti-CD20 antibody treatment on disease-relevant B cell populations within lymph nodes and the spleen. B cell depleting capacity was explored in healthy female C57BL/6 and BALB/c mice; following immune activation in two different mouse models: trinitrophenylated lipopolysaccharide model (thymus-independent response) and dinitrophenyl-keyhole limpet hemocyanin model (thymus-dependent response); and in a chronic neuroinflammation experimental autoimmune encephalomyelitis model. CD20 protein expression on B cell subpopulations was also studied. The subcutaneous anti-CD20 regimen resulted in rapid depletion of B cells in blood, lymph nodes and spleen. Low-dose subcutaneous treatment did not reduce antigen-specific immunoglobulin M and immunoglobulin G titers in all subgroups, and relatively spared splenic marginal zone (MZ) B cells in both T cell dependent and T cell independent B cell immunization models. Analysis of immune compartments during anti-CD20-modulated autoimmune neuroinflammation showed that the maximal B cell depletion was achieved within 2 days of treatment and was highest in the lymph node. Regardless of the tissues analyzed, low-dose subcutaneous treatment was characterized by rapid B cell repletion following treatment cessation. CD20 protein expression was consistent on all B cell subsets in blood, and was more pronounced in germinal center B cells of lymph nodes and MZ B-cells of the spleen. Low-dose subcutaneous anti-CD20 therapy effectively depleted B cells within lymphatic tissues and reduced the severity of neuroinflammation. These data suggest that subcutaneous anti-CD20 therapies can effectively target disease-relevant B cell populations, have shorter repletion kinetics and maintain vaccination responses, thereby achieving autoimmune amelioration without severely impacting immune surveillance functions. Graphical Abstract *p < 0.05; **p < 0.01. CD, cluster of differentiation; DNP-KLH, dinitrophenyl-keyhole limpet hemocyanin; EC50, concentration of a drug that gives half-maximal response; Ig, immunoglobulin; MZ, marginal zone; s.c., subcutaneous; SEM, standard error of mean; TNP-LPS, trinitrophenylatedlipopolysaccharide.

The autoimmune basis of hypopituitarism in traumatic brain injury: fiction or reality?

Post-traumatic hypopituitarism has remained as an obscured cause of worsening morbidity and mortality in head injury patients. Researchers have for decades been puzzled by the mechanism of pituitary dysfunction in these cases. Amongst other causes like direct injury, vascular injury etc, an immunological basis of hypopituitarism has been suggested in some animal studies as well as human research. In this article, we have reviewed the latest articles and compiled the evidence which suggests for or against the role of autoimmunity in post-traumatic hypopituitarism or which defines the strength to which autoimmunity has been established as a cause of head-injury induced pituitary dysfunction.

Human Stem Cell-Derived Models: Lessons for Autoimmune Diseases of the Nervous System.

Autoimmunity of the peripheral and central nervous system is an important cause of disease and long-term neurological disability. Autoantibodies can target both intracellular and extracellular neuronal epitopes. Autoantibodies that target cell-surface epitopes infer pathogenicity through several distinct mechanisms, while patients often respond to immunotherapy. However, the underlying pathogenesis of these autoantibodies is yet to be fully understood. Human stem cell-based disease modeling, and the rise of induced pluripotent stem cell technology in particular, has revolutionized the fields of disease modeling and therapeutic screening for neurological disorders. These human disease models offer a unique platform in which to study autoimmunity of the nervous system. Here, we take an in-depth look at the possibilities that these models provide to study neuronal autoantibodies and their underlying pathogenesis.

Nrf2/ARE pathway inhibits inflammatory infiltration by macrophage in rats with autoimmune myositis.

BACKGROUND: Idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases characterized by muscle disorders. We conducted this study to detect whether NF-E2-related factor 2 (Nrf2) pathway inhibit inflammatory infiltration by macrophage in experimental autoimmune myositis (EAM) rat model. METHODS: CD163 levels were examined by immunohistochemistry (IHC), while serum creatine kinase (CK), reactive oxygen species (ROS), and serum monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) levels were determined by enzyme linked immunosorbnent assay (ELISA), both in IIM patients and EAM rat. We also detected MCP-1, TNF-α, IL-6, and Nrf2 levels by Realtime quantitative PCR (RT-PCR) in patients' muscles, and MCP-1, TNF-α, IL-6, and Nrf2, HO-1, NQO-1 levels by RT-PCR and Western blot in EAM rats' muscles. EAM macrophages were separated, and Nrf2 over-expression macrophages were constructed. ROS level and cell migration were detected by flow cytometer and transwell assay respectively. Then, levels of MCP-1, TNF-α, IL-6, Nrf2, Heme oxygenase-1 (HO-1) and NAD(P)H: quinine oxidoreductase 1 (NQO-1) were detected by RT-PCR and Western blot. RESULTS: Results showed that EAM rats were histopathologically inflammatory cell infiltration. Levels of CD163, serum CK and ROS, serum/muscle MCP-1, TNF-α and IL-6 increased and muscle Nrf2 level decreased in IIM patients and EAM rats. Cell migration ability and levels of ROS, MCP-1, TNF-α, IL-6, and plasma Nrf2 were down-regulated, and total/nucleus Nrf2, HO-1, NQO-1 were up-regulated notably when Nrf2 over-expressed. CONCLUSION: Nrf2 inhibited EAM macrophage infiltration by activating Nrf2/ARE pathway which could induce ROS degradation and inhibit pro-inflammatory factors expression.

MicroRNA-381 reduces inflammation and infiltration of macrophages in polymyositis via downregulating HMGB1.

The downregulation of microRNA (miR)-381 has been detected in various diseases. The present study aimed to investigate the effects, and underlying mechanisms of miR-381 on inflammation and macrophage infiltration in polymyositis (PM). A mouse model of experimental autoimmune myositis (EAM) was generated in this study. Hematoxylin and eosin staining was conducted to detect the inflammation of muscle tissues. In addition, ELISA and immunohistochemistry were performed to determine the expression levels of associated factors, and reverse transcription-quantitative polymerase chain reaction and western blotting were used to detect the expression levels of related mRNAs and proteins. A luciferase activity assay was used to confirm the binding of miR-381 and high mobility group box 1 (HMGB1) 3' untranslated region. Transwell assays were also performed to assess the migratory ability of macrophages. The results demonstrated that serum creatine kinase (s-CK), HMGB1 and cluster of differentiation (CD)163 expression in patients with PM were increased compared within healthy controls. Conversely, the expression levels of miR-381 were downregulated in patients with PM. Furthermore, high HMGB1 expression was associated with poor survival rate in patients with PM. In the mouse studies, muscle inflammation and CD163 expression were decreased in the anti-IL-17 and anti-HMGB1 groups, compared with in the EAM model group. The expression levels of s-CK, HMGB1, IL-17 and intercellular adhesion molecule (ICAM)-1 were also downregulated in response to anti-IL-17 and anti-HMGB1. These findings indicated that HMGB1 was closely associated with inflammatory responses. In addition, the present study indicated that transfection of macrophages with miR-381 mimics reduced the migration of inflammatory macrophages, and the expression levels of HMGB1, IL-17 and ICAM-1. Conversely, miR-381 inhibition exerted the opposite effects. The effects of miR-381 inhibitors were reversed by HMGB1 small interfering RNA. In conclusion, miR-381 may reduce inflammation and the infiltration of macrophages; these effects were closely associated with the downregulation of HMGB1.

Exacerbation of Murine Experimental Autoimmune Myositis by Toll-Like Receptor 7/8.

OBJECTIVE: Toll-like receptor 7 (TLR-7), TLR-8, and interferon (IFN)-induced genes are expressed in patients with idiopathic inflammatory myositis. This study was undertaken to investigate whether their activation influences the natural history of the disease. METHODS: Experimental autoimmune myositis was induced in mice by injection of the amino-terminal portion of the murine histidyl-transfer RNA synthetase (HisRS). Disease was compared in the presence or the absence of the TLR-7/8 agonist R-848 in wild-type mice and in mice that fail to express the IFNα/ß receptor (IFNα/ßR-null mice). RESULTS: Experimental autoimmune myositis induced by a single intramuscular immunization with HisRS spontaneously abated after 7-8 weeks. In contrast, levels of anti-HisRS autoantibodies, endomysial/perimysial leukocyte infiltration, and myofiber regeneration persisted at the end of the follow-up period (22 weeks after immunization) in mice immunized with HisRS in the presence of R-848. Myofiber major histocompatibility complex (MHC) class I molecules were detectable only in mice immunized with both HisRS and R-848. MHC up-regulation occurred early and in muscles that were not directly injected with HisRS. Muscle MHC expression paralleled with leukocyte infiltration. MHC class I molecules were selectively up-regulated in myotubes challenged with R-848 in vitro. Type I IFN was necessary for the prolonged autoantibody response and for the spreading of the autoimmune response, as demonstrated using IFNα/ßR-null mice. Muscle infiltration was maintained in the injected muscle up to the end of the follow-up period. CONCLUSION: TLR-7/8 activation is necessary to induce and maintain a systemic autoimmune response targeting the skeletal muscle. This experimental autoimmune myositis model reproduces many characteristics of human idiopathic inflammatory myopathies and may represent a tool for preclinical studies.

Mapping autoantigen epitopes: molecular insights into autoantibody-associated disorders of the nervous system.

BACKGROUND: Our knowledge of autoantibody-associated diseases of the central (CNS) and peripheral (PNS) nervous systems has expanded greatly over the recent years. A number of extracellular and intracellular autoantigens have been identified, and there is no doubt that this field will continue to expand as more autoantigens are discovered as a result of improved clinical awareness and methodological practice. In recent years, interest has shifted to uncover the target epitopes of these autoantibodies. MAIN BODY: The purpose of this review is to discuss the mapping of the epitope targets of autoantibodies in CNS and PNS antibody-mediated disorders, such as N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), leucine-rich glioma-inactivated protein 1 (Lgi1), contactin-associated protein-like 2 (Caspr2), myelin oligodendrocyte glycoprotein (MOG), aquaporin-4 (AQP4), 65 kDa glutamic acid decarboxylase (GAD65), acetylcholine receptor (AChR), muscle-specific kinase (MuSK), voltage-gated calcium channel (VGCC), neurofascin (NF), and contactin. We also address the methods used to analyze these epitopes, the relevance of their determination, and how this knowledge can inform studies on autoantibody pathogenicity. Furthermore, we discuss triggers of autoimmunity, such as molecular mimicry, ectopic antigen expression, epitope spreading, and potential mechanisms for the rising number of double autoantibody-positive patients. CONCLUSIONS: Molecular insights into specificity and role of autoantibodies will likely improve diagnosis and treatment of CNS and PNS neuroimmune diseases.

Macrophages and cardiac fibroblasts are the main producers of eotaxins and regulate eosinophil trafficking to the heart.

Cardiac manifestations are a major cause of morbidity and mortality in patients with eosinophil-associated diseases. Eosinophils are thought to play a pathogenic role in myocarditis. We investigated the pathways that recruit eosinophils to the heart using a model of eosinophilic myocarditis, in which experimental autoimmune myocarditis (EAM) is induced in IFNγ-/- IL-17A-/- mice. Two conditions are necessary for efficient eosinophil trafficking to the heart: high eotaxin (CCL11, CCL24) expression in the heart and expression of the eotaxin receptor CCR3 by eosinophils. We identified cardiac fibroblasts as the source of CCL11 in the heart interstitium. CCL24 is produced by F4/80+ macrophages localized at inflammatory foci in the heart. Expression of CCL11 and CCL24 is controlled by Th2 cytokines, IL-4 and IL-13. To determine the relevance of this pathway in humans, we analyzed endomyocardial biopsy samples from myocarditis patients. Expression of CCL11 and CCL26 was significantly increased in eosinophilic myocarditis compared to chronic lymphocytic myocarditis and positively correlated with the number of eosinophils. Thus, eosinophil trafficking to the heart is dependent on the eotaxin-CCR3 pathway in a mouse model of EAM and associated with cardiac eotaxin expression in patients with eosinophilic myocarditis. Blocking this pathway may prevent eosinophil-mediated cardiac damage.

CD73 Expressed on γδ T Cells Shapes Their Regulatory Effect in Experimental Autoimmune Uveitis.

γδ T cells can either enhance or inhibit an adaptive immune response, but the mechanisms involved are not fully understood. Given that CD73 is the main enzyme responsible for conversion of AMP into the immunosuppressive molecule adenosine, we investigated its role in the regulatory function of γδ T cells in experimental autoimmune uveitis (EAU). We found that γδ T cells expressed different amounts of CD73 during the different stages of EAU and that low CD73 expression on γδ T cells correlated with enhanced Th17 response-promoting activity. Functional comparison of CD73-deficient and wild-type B6 (CD73+/+) mice showed that failure to express CD73 decreased both the enhancing and suppressive effects of γδ T cells on EAU. We also demonstrated that γδ T cells expressed different amounts of CD73 when activated by different pathways, which enabled them to either enhance or inhibit an adaptive immune response. Our results demonstrate that targeting CD73 expression on γδ T cells may allow us to manipulate their pro- or anti-inflammatory effect on Th17 responses.

Loss of galectin-3 decreases the number of immune cells in the subventricular zone and restores proliferation in a viral model of multiple sclerosis.

Multiple sclerosis (MS) frequently starts near the lateral ventricles, which are lined by subventricular zone (SVZ) progenitor cells that can migrate to lesions and contribute to repair. Because MS-induced inflammation may decrease SVZ proliferation and thus limit repair, we studied the role of galectin-3 (Gal-3), a proinflammatory protein. Gal-3 expression was increased in periventricular regions of human MS in post-mortem brain samples and was also upregulated in periventricular regions in a murine MS model, Theiler's murine encephalomyelitis virus (TMEV) infection. Whereas TMEV increased SVZ chemokine (CCL2, CCL5, CCL, and CXCL10) expression in wild type (WT) mice, this was inhibited in Gal-3(-/-) mice. Though numerous CD45+ immune cells entered the SVZ of WT mice after TMEV infection, their numbers were significantly diminished in Gal-3(-/-) mice. TMEV also reduced neuroblast and proliferative SVZ cell numbers in WT mice but this was restored in Gal-3(-/-) mice and was correlated with increased numbers of doublecortin+ neuroblasts in the corpus callosum. In summary, our data showed that loss of Gal-3 blocked chemokine increases after TMEV, reduced immune cell migration into the SVZ, reestablished SVZ proliferation and increased the number of progenitors in the corpus callosum. These results suggest Gal-3 plays a central role in modulating the SVZ neurogenic niche's response to this model of MS.

Roles of Treg/Th17 Cell Imbalance and Neuronal Damage in the Visual Dysfunction Observed in Experimental Autoimmune Optic Neuritis Chronologically.

Optic neuritis associated with multiple sclerosis and its animal model, experimental autoimmune optic neuritis (EAON), is characterized by inflammation, T cell activation, demyelination, and neuronal damage, which might induce permanent vision loss. Elucidating the chronological relationship among the features is critical for treatment of demyelinating optic neuritis. EAON was induced in C57BL/6 mice immunized with myelin oligodendrocyte glycoprotein subcutaneously, and visual function was assessed by flash-visual evoked potential (F-VEP) at days 7, 11, 14, 19, 23, 28 post-immunization. Retinal ganglion cell (RGC) apoptosis was measured by terminal-deoxynucleotidyl transferase-mediated nick-end labeling. Demyelination and axonal damage were verified with myelin basic protein (MBP) and ß-amyloid precursor protein staining, respectively. Real-time polymerase chain reaction quantified IL-17, IL-1ß, TGF-ß, FoxP3, IL-6, and IL-10 mRNA expression in the optic nerve, as well as FoxP3 and IL-17 staining. Systemic changes of Th17 and Treg cells were tested by flow cytometry in spleen. F-VEP latency was prolonged at 11 days and peaked at 23 days commensurate with demyelination. However, F-VEP amplitude was reduced at 11 days, preceding axon damage, and was exacerbated at 23 days when a peak in RGC apoptosis was detected. Th17 cells up-regulated as early as 7 days and peaked at 11 days, while Treg cells down-regulated inversely compared to Th17 cells change as verified by IL-17 and FoxP3 expression; spleen cell samples were slightly different, demonstrating marked changed at 14 days. Treg/Th17 cell imbalance in the optic nerve precedes and may initiate neuronal damage of axons and RGCs. These changes are commensurate with the appearances of visual dysfunction reflected in F-VEP and hence may offer a novel therapeutic avenue for vision preservation.

Injury and subsequent regeneration of muscles for activation of local innate immunity to facilitate the development and relapse of autoimmune myositis in C57BL/6 mice.

OBJECTIVE: To determine whether injury and regeneration of the skeletal muscles induce an inflammatory milieu that facilitates the development and relapse of autoimmune myositis. METHODS: The quadriceps of C57BL/6 mice were injured with bupivacaine hydrochloride (BPVC) and evaluated histologically. Macrophages and regenerating myofibers in the treated muscles and differentiating C2C12 myotubes were examined for cytokine expression. Mice were immunized with C protein fragments at the base of the tail and in the right hind footpads (day 0) to evoke systemic anti-C protein immunity and to induce local myositis in the right hind limbs. The contralateral quadriceps muscles were injured with BPVC or phosphate buffered saline (PBS) on day 7 or after spontaneous regression of myositis (day 42). The quadriceps muscle in nonimmunized mice was injured with BPVC on day 7. The muscles were examined histologically 14 days after treatment. RESULTS: The BPVC-injured muscles had macrophage infiltration most abundantly at 3 days after the injection, with emergence of regenerating fibers from day 5. The macrophages expressed inflammatory cytokines, including tumor necrosis factor α, interleukin-1ß, and CCL2. Regenerating myofibers and C2C12 myotubes also expressed the cytokines. The BPVC-injected muscles from nonimmunized mice had regenerating myofibers with resolved cell infiltration 14 days after treatment. In mice preimmunized with C protein fragments, the muscles injected with BPVC on day 7 as well as on day 42, but not those injected with PBS, had myositis accompanied by CD8+ T cell infiltration. CONCLUSION: Injury and regeneration could set up an inflammatory milieu in the muscles and facilitate the development and relapse of autoimmune myositis.

Required role of apoptotic myogenic precursors and toll-like receptor stimulation for the establishment of autoimmune myositis in experimental murine models.

OBJECTIVE: Muscle regeneration is a hallmark of the idiopathic inflammatory myopathies (IIMs), a group of autoimmune disorders that are characterized by leukocyte infiltration and dysfunction of the skeletal muscle. Despite detailed studies describing the clinical and histopathologic features of IIMs, the immunopathogenesis of these disorders remains undefined. The aim of this study was to investigate the immunopathologic processes of autoimmune myositis in experimental murine models. METHODS: Expression of the autoantigen histidyl-transfer RNA synthetase (HisRS) was analyzed in mice with acutely injured or dystrophic muscles, in inflammatory leukocytes, and in purified satellite cells. Anti-HisRS antibodies and myositis induction were assessed in mice after muscle injury and immunization with apoptotic satellite cells or C2C12 myoblasts, in the presence or absence of the Toll-like receptor 7 (TLR-7) agonist R848. RESULTS: Muscle necrosis, leukocyte infiltration, and myofiber regeneration induced by toxic agents (cardiotoxin or glycerol) or promoted by genetic disruption of the α-sarcoglycan/dystrophin complex in mice were uniformly associated with up-regulated expression of HisRS. Although regenerating myofibers and purified satellite cells are known to show increased expression of HisRS in these settings, anti-HisRS antibodies were not detectable. However, intramuscular immunization with ultraviolet B-irradiated, HisRS-expressing apoptotic myoblasts in the presence of R848 triggered the production of anti-HisRS IgG antibodies as well as persistent lymphocyte infiltration and prolonged/delayed muscle regeneration. Conversely, intramuscular administration of R848 alone or in combination with living or postapoptotic/necrotic myoblasts failed to generate this myositis phenotype. CONCLUSION: In the presence of TLR/adjuvant signals and underlying muscle injury, apoptotic myogenic precursors expressing high levels of autoantigen can provoke autoantibody formation and lymphocytic infiltration of muscle tissue, effectively replicating the features of IIM.

Development of an improved animal model of experimental autoimmune myositis.

Multiple animal models of experimental autoimmune myositis (EAM) have been developed. However, these models vary greatly in the severity of disease and reproducibility. The goal of this study was to test whether vaccination twice with increased dose of rat myosin and pertussis toxin (PT) could induce EAM with severer disease in mice. BALB/c mice were injected with 1 mg rat myosin in 50% complete Freund's adjuvant (CFA) weekly for four times and one time of PT (EAM) or twice with 1.5 mg myosin in CFA and PT (M-EAM). In comparison with that in the CFA and PT injected controls, vaccination with rat myosin and injection PT significantly reduced the muscle strength and EMG duration, elevated serum creatine kinase levels, promoted inflammatory infiltration in the muscle tissues, leading to pathological changes in the muscle tissues, demonstrating to induce EAM. Interestingly, we found that vaccination twice with the high dose of myosin and PT prevented EAM-related gain in body weights and caused significantly less muscle strength in mice. More importantly, all of the mice receiving high dose of myosin and PT survived while 3 out of 16 mice with four times of low dose of myosin died. Finally, vaccination with high dose of myosin promoted CD4(+) and CD8(+) T cell infiltration in the muscle tissues and up-regulated MHC-I expression in the muscle tissues of mice. Hence, the new model of EAM is a time-saving, efficient and easily replicable tool for studying autoimmune myositis.

Beneficial role of rapamycin in experimental autoimmune myositis.

INTRODUCTION: We developed an experimental autoimmune myositis (EAM) mouse model of polymyositis where we outlined the role of regulatory T (Treg) cells. Rapamycin, this immunosuppressant drug used to prevent rejection in organ transplantation, is known to spare Treg. Our aim was to test the efficacy of rapamycin in vivo in this EAM model and to investigate the effects of the drug on different immune cell sub-populations. METHODS: EAM is induced by 3 injections of myosin emulsified in CFA. Mice received rapamycin during 25 days starting one day before myosin immunization (preventive treatment), or during 10 days following the last myosin immunization (curative treatment). RESULTS: Under preventive or curative treatment, an increase of muscle strength was observed with a parallel decrease of muscle inflammation, both being well correlated (R(2) = -0.645, p<0.0001). Rapamycin induced a general decrease in muscle of CD4 and CD8 T cells in lymphoid tissues, but spared B cells. Among T cells, the frequency of Treg was increased in rapamycin treated mice in draining lymph nodes (16.9 ± 2.2% vs. 9.3 ± 1.4%, p<0.001), which were mostly activated regulatory T cells (CD62L(low)CD44(high): 58.1 ± 5.78% vs. 33.1 ± 7%, treated vs. untreated, p<0.001). In rapamycin treated mice, inhibition of proliferation (Ki-67(+)) is more important in effector T cells compared to Tregs cells (p<0.05). Furthermore, during preventive treatment, rapamycin increased the levels of KLF2 transcript in CD44(low) CD62L(high) naive T cell and in CD62L(low) CD44(high) activated T cell. CONCLUSIONS: Rapamycin showed efficacy both as curative and preventive treatment in our murine model of experimental myositis, in which it induced an increase of muscle strength with a parallel decrease in muscle inflammation. Rapamycin administration was also associated with a decrease in the frequency of effector T cells, an increase in Tregs, and, when administered as preventive treatment, an upregulation of KFL2 in naive and activated T cells.