Experimental Allergic Encephalitis Research Articles

Inhibition of SUMOylation promotes remyelination and reduces IL-17 mediated autoimmune inflammation: Novel approach toward treatment of inflammatory CNS demyelinating disease

Small ubiquitin like modifiers (SUMO) are reversible posttranslational modifiers of intracellular proteins. In the CNS, expression of myelin genes is regulated by state of SUMOylation of their respective transcription factors. In the immune system, deSUMOylation activates innate immune responses and promotes anti-viral immunity. However, the role played by SUMO in an adaptive immune response and in the development of T cell mediated autoimmune disease has not been previously described.TAK981 is a synthetic small molecule which by forming adducts with SUMO proteins prevents SUMOylation. We examined the expression of myelin genes and their transcription factors following culture with TAK981 in Oligodendrocyte Precursor Cells (OPC). We found that myelin basic protein (MBP), a key myelin protein, is upregulated in OPC in the presence of TAK981. We also found increased expression of transcription factors Sox10 and Myrf, which engage in the expression of MBP. In the Cuprizone model of demyelination/remyelination, animals which were treated with TAK981 showed increased remyelination in areas of demyelination and an increase in the number of maturing oligodendrocytes compared to vehicle treated controls. In in vitro cultures of lymphocytes, TAK981 reduced the expression of TH17 in T cells in mice immunized with MOGp35–55. Following in vivo treatment with TAK981, there was a significant reduction in the clinical and pathological severity in mice immunized to develop experimental allergic encephalitis (EAE).The dual effects of deSUMOylation on remyelination and in regulating an autoimmune adaptive response offers a novel approach to the management of human inflammatory demyelinating diseases such as multiple sclerosis.

ID3 may protect mice from anti‑GBM glomerulonephritis by regulating the differentiation of Th17 and Treg cells.

Anti‑glomerular basement membrane glomerulonephritis (anti‑GBM GN) is an autoimmune disease that leads to severe and rapidly progressive renal injury. Inhibition of DNA‑binding factor 3 (ID3) serves a key role in autoimmune diseases, such as asthma and Sjögren's syndrome, and in experimental allergic encephalitis models. However, the role of ID3 in the progression of anti‑GBM GN remains unknown. In the present study, ID3 mRNA expression increased between 3‑ and 20‑fold in the renal tissues of anti‑GBM GN mice compared with the Control group, with a peak at day 14 post‑induction. In addition, ID3 protein expression was upregulated from day 7 onwards. The expression of ID3 was also examined in the spleen, and was demonstrated to be increased in the spleen of nephritic mice. T helper 17 (Th17) cells and regulatory T (Treg) cells were present throughout the entire period of observation (from day 7 to day 28) in anti‑GBM GN mice, which may vary at different time points, accompanied with the expression of ID3. Invitro, ID3 expression was increased when CD4+ T cells differentiated into Tregs; however, expression was lower in Th17 cells. Following treatment with ID3 small interfering RNA, RAR‑related orphan receptor γt, but not forkhead box P3, expression increased. Furthermore, increased expression of interleukin‑17A was also observed when ID3 was blocked. In addition, ID3 was able to interact with transcription factor E2A. A significant increase in binding between ID3 and E2A was observed in anti‑GBM GN from day 7 onwards, with a peak at day 14 in both renal tissue and spleen. In conclusion, ID3 may be involved in the differentiation of Th17 and Tregs by downregulating Th17 cells, which is probably associated with binding to E2A. The present results suggested that ID3 may offer protection against anti‑GBM GN in mice.

Administration of Uric Acid in the Emergency Treatment of Acute Ischemic Stroke.

Oxidative stress is one of the main mechanisms implicated in the pathophysiology of inflammatory and neurodegenerative diseases of the central nervous system (CNS). Uric acid (UA) is the end product of purine catabolism in humans, and it is the main endogenous antioxidant in blood. Low circulating UA levels have been associated with an increased prevalence and worse clinical course of several neurodegenerative and inflammatory diseases of the CNS, including Parkinson's disease and multiple sclerosis. Moreover, the exogenous administration of UA exerts robust neuroprotective properties in experimental models of CNS disease, including brain ischemia, spinal cord injury, meningitis, and experimental allergic encephalitis. In experimental brain ischemia, exogenous UA and the thrombolytic agent alteplase exert additive neuroprotective effects when administered in combination. UA is rapidly consumed following acute ischemic stroke, and higher UA levels at stroke admission are associated with a better outcome and reduced infarct growth at follow-up. A recent phase II trial demonstrated that the combined intravenous administration of UA and alteplase is safe and prevents an early decrease of circulating UA levels in acute ischemic stroke patients. Moreover, UA prevents the increase in the circulating levels of the lipid peroxidation marker malondialdehyde and of active matrix metalloproteinase (MMP) 9, a marker of blood-brain barrier disruption. The moderately sized URICOICTUS phase 2b trial showed that the addition of UA to thrombolytic therapy resulted in a 6% absolute increase in the rate of excellent outcome at 90 days compared to placebo. The trial also showed that UA administration resulted in a significant increment of excellent outcome in patients with pretreatment hyperglycemia, in females and in patients with moderate strokes. Overall, the encouraging neuroprotective effects of UA therapy in acute ischemic stroke warrants further investigation in adequately powered clinical trials.

Ocular nerve growth factor administration (oNGF) affects disease severity and inflammatory response in the brain of rats with experimental allergic encephalitis (EAE).

The rat acute experimental autoimmune encephalomyelitis (EAE) model was used to investigate the effects of ocularly administered nerve growth factor (oNGF) on disease development and brain inflammation. It was found that oNGF affects clinical scores. However, EAE rats receiving oNGF treatment showed reduced expression of pro-inflammatory cytokines and chemokines in the cerebellum and the hippocampus, but not in the frontal cortex. These data confirm the ability of oNGF to counteract the effects of EAE in the brain and suggest a role for oNGF in the regulation of local inflammatory responses observed in the acute phase of EAE.

IL-15-secreting γδT cells induce memory T cells in experimental allergic encephalomyelitis (EAE) mice

With the most recent data suggesting γδT cells as primary producers of the pro-inflammatory autoimmune-associated cytokine, the relationship between γδT cells and Th17 in experimental allergic encephalitis (EAE) mice requires more extensive investigation. By flow cytometry and qPCR, we identified a new subset of IL-15-secreting γδT (γδT15) cells that increased in EAE mice. The capacity of IL-15-secreting γδT cells inducing memory T cells and memory T cells inducing IL-17+Th17 was examined by transferring into EAE mice and 7-week-old female nude mice, respectively. We found that γδT15 induced CD44hi memory T cells by secreting IL-15. γδT15-induced memory T cells induced EAE by transforming into pathogenic Th17 cells. The data suggest that a new subset of IL-15-secreting γδT cells mediated the production of memory T cells which transformed into pathogenic Th17 cells in EAE mice.

Synthetic and natural inhibitors of phospholipases A2: their importance for understanding and treatment of neurological disorders.

Phospholipases A2 (PLA2) are a diverse group of enzymes that hydrolyze membrane phospholipids into arachidonic acid and lysophospholipids. Arachidonic acid is metabolized to eicosanoids (prostaglandins, leukotrienes, thromboxanes), and lysophospholipids are converted to platelet-activating factors. These lipid mediators play critical roles in the initiation, maintenance, and modulation of neuroinflammation and oxidative stress. Neurological disorders including excitotoxicity; traumatic nerve and brain injury; cerebral ischemia; Alzheimer's disease; Parkinson's disease; multiple sclerosis; experimental allergic encephalitis; pain; depression; bipolar disorder; schizophrenia; and autism are characterized by oxidative stress, inflammatory reactions, alterations in phospholipid metabolism, accumulation of lipid peroxides, and increased activities of brain phospholipase A2 isoforms. Several old and new synthetic inhibitors of PLA2, including fatty acid trifluoromethyl ketones; methyl arachidonyl fluorophosphonate; bromoenol lactone; indole-based inhibitors; pyrrolidine-based inhibitors; amide inhibitors, 2-oxoamides; 1,3-disubstituted propan-2-ones and polyfluoroalkyl ketones as well as phytochemical based PLA2 inhibitors including curcumin, Ginkgo biloba and Centella asiatica extracts have been discovered and used for the treatment of neurological disorders in cell culture and animal model systems. The purpose of this review is to summarize information on selective and potent synthetic inhibitors of PLA2 as well as several PLA2 inhibitors from plants, for treatment of oxidative stress and neuroinflammation associated with the pathogenesis of neurological disorders.

Is there a place for B cells as regulators of immune tolerance in allergic diseases?

Is there a place for B cells as regulators of immune tolerance in allergic diseases?

BAFF maintains T-cell survival by inducing OPN expression in B cells

Dysregulation of T-cell survival and apoptosis is the common cause of autoimmune diseases such as multiple sclerosis (MS). However, the factors inducing imbalance of T-cell survival and apoptosis in MS remains unclear. Here, we show that the resistance to apoptosis was associated with high levels of B-cell activating factor (BAFF). Blockade of BAFF with TACI (transmembrane activator and calcium modulator and cyclophilin ligand interactor)-IgG significantly reduced T-cell survival in myelin oligodendroglia glycoprotein (MOG)-induced chronic experimental allergic encephalitis (EAE). Furthermore, BAFF induced anti-apoptotic molecule Bcl2 expression in T cells by up-regulating osteopontin (OPN) secretion from B cells. BAFF mainly induced OPN expression in splenic CD21−CD23+ B cells via a NF-kB dependent signaling pathway. In addition, we found that BAFF and OPN levels were increased in MS patients similar to the results obtained from our mice research. The study suggests that BAFF regulates T-cell survival by inducing OPN secretion in B cells in autoimmune diseases.

Transcription of RORγt in developing Th17 cells is regulated by E-proteins.

In the present study we investigated the molecular mechanisms regulating the expression of RORγt, the central factor controlling IL-17 transcription and Th17 differentiation. In key studies we found that cells from mice with major deletions of the E-protein transcription factors, E2A and HEB, display greatly reduced RORγt/IL-17 expression and that E-protein-deficient mice exhibit greatly diminished IL-17-dependent inflammation in EAE models. In additional studies, we unexpectedly found that cells from mice with deletion of Id3, a protein that inhibits E-protein binding to DNA, display diminished RORγt/IL-17 expression and mice deficient in this protein exhibit decreased Th17-mediated inflammation in a cell-transfer colitis model. The explanation of these initially paradoxical findings came from studies showing that Id3 deficiency leads to increased IL-4-induced GATA-3 expression, the latter a negative regulator of RORγt transcription; thus, increased Id3 expression likely has a net positive effect on RORγt expression via its inhibition of IL-4 production. Finally, we found that both E-proteins and Id3 are up-regulated in tandem by the cytokines that induce Th17 differentiation, TGF-β and IL-6, implying that these transcription factors are critical regulators of Th17 induction.

Liposome‐encapsulated peptides protect against experimental allergic encephalitis

Multiple sclerosis (MS) is a severe inflammatory and neurodegenerative disease with an autoimmune background. Despite the variety of therapeutics available against MS, the development of novel approaches to its treatment is of high importance in modern pharmaceutics. In this study, experimental autoimmune encephalomyelitis (EAE) in Dark Agouti rats has been treated with immunodominant peptides of the myelin basic protein (MBP) encapsulated in mannosylated small unilamellar vesicles. The results show that liposome-encapsulated MBP46–62 is the most effective in reducing maximal disease score during the first attack, while MBP124–139 and MBP147–170 can completely prevent the development of the exacerbation stage. Both mannosylation of liposomes and encapsulation of peptides are critical for the therapeutic effect, since neither naked peptides nor nonmannosylated liposomes, loaded or empty, have proved effective. The liposome-mediated synergistic effect of the mixture of 3 MBP peptides significantly suppresses the progression of protracted EAE, with the median cumulative disease score being reduced from 22 to 14 points, compared to the placebo group; prevents the production of circulating autoantibodies; down-regulates the synthesis of Th1 cytokines; and induces the production of brain-derived neurotrophic factor in the central nervous system. Thus, the proposed formulation ameliorates EAE, providing for a less severe first attack and rapid recovery from exacerbation, and offers a promising therapeutic modality in MS treatment.—Belogurov, A. A., Jr., Stepanov, A. V., Smirnov, I. V., Melamed, D., Bacon, A., Mamedov, A. E., Boitsov, V. M., Sashchenko, L. P., Ponomarenko, N. A., Sharanova, S. N., Boyko, A. N., Dubina, M. V., Friboulet, A., Genkin, D. D., Gabibov, A. G. Liposome-encapsulated peptides protect against experimental allergic encephalitis.

Treatment of Autoimmune Inflammation by a TLR7 Ligand Regulating the Innate Immune System

The Toll-like receptors (TLR) have been advocated as attractive therapeutic targets because TLR signaling plays dual roles in initiating adaptive immune responses and perpetuating inflammation. Paradoxically, repeated stimulation of bone marrow mononuclear cells with a synthetic TLR7 ligand 9-benzyl-8-hydroxy-2-(2-methoxyethoxy) adenine (called 1V136) leads to subsequent TLR hyporesponsiveness. Further studies on the mechanism of action of this pharmacologic agent demonstrated that the TLR7 ligand treatment depressed dendritic cell activation, but did not directly affect T cell function. To verify this mechanism, we utilized experimental allergic encephalitis (EAE) as an in vivo T cell dependent autoimmune model. Drug treated SJL/J mice immunized with proteolipid protein (PLP)139–151 peptide had attenuated disease severity, reduced accumulation of mononuclear cells in the central nervous system (CNS), and limited demyelination, without any apparent systemic toxicity. Splenic T cells from treated mice produced less cytokines upon antigenic rechallenge. In the spinal cords of 1V136-treated EAE mice, the expression of chemoattractants was also reduced, suggesting innate immune cell hyposensitization in the CNS. Indeed, systemic 1V136 did penetrate the CNS. These experiments indicated that repeated doses of a TLR7 ligand may desensitize dendritic cells in lymphoid organs, leading to diminished T cell responses. This treatment strategy might be a new modality to treat T cell mediated autoimmune diseases.

Th17 cells generated in the absence of TGF-β induce experimental allergic encephalitis upon adoptive transfer

Evaluation of: Ghoreschi K, Laurence A, Yang XP et al. Generation of pathogenic T(h)17 cells in the absence of TGF-β signalling. Nature 467(7318), 967–971 (2010).The discovery of IL-17-producing helper T cells (Th17) has led to new concepts of T-cell differentiation and immunity. Importantly, Th17 cells are thought to be important drivers of autoimmunity. TGF-β and IL-6 in combination were shown to induce differentiation of murine naive CD4 T cells into IL-17-producing cells in vitro. By contrast, human Th17 differentiation was shown to be independent of TGF-β and could be induced by IL-6 in conjunction with IL-21 or with IL-1. Ghoreschi et al. have elegantly demonstrated that mouse Th17 cell differentiation can also occur in the absence of TGF-β. A combination of IL-23, IL-1 and IL-6 can give rise to IL-17-producing cells, which are characterized by the expression of T-bet. Intriguingly, the adoptive transfer of such in vitro differentiated Th17 cells into lymphocyte-deficient mice resulted in the induction of experimental allergic encephalitis, which was more severe than in mice receiving Th17 cells differentiated in the presence of TGF-β. Collectively, the results suggest that a subpopulation of Th17 cells differentiated in the absence of TGF-β, expressing T-bet and RORγt, occur in vivo and may be responsible for autoimmunity.

The Starting Lineup: Key Microbial Players in Intestinal Immunity and Homeostasis

The complexity of microbiota inhabiting the intestine is increasingly apparent. Delicate balance of numerous bacterial species can affect development of the immune system, how susceptible a host is to pathogenic organisms, and the auto-inflammatory state of the host. In the last decade, with the increased use of germ-free mice, gnotobiotic mice, and animal models in which a germ-free animal has been colonized with a foreign microbiota such as humanized mice, it has been possible to delineate relationships that specific bacteria have with the host immune system and to show what role they may play in overall host health. These models have not only allowed us to tease out the roles of individual species, but have also allowed the discovery and characterization of functionally unknown organisms. For example, segmented filamentous bacteria (SFB) have been shown to play a vital role in expansion of IL-17 producing cells. Prior to linking their key role in immune system development, little was known about these organisms. Bacteroides fragilis can rescue some of the immune defects of gnotobiotic mice after mono-colonization and have anti-inflammatory properties that can alleviate colitis and experimental allergic encephalitis in murine models. Additionally, Clostridium species have most recently been shown to expand regulatory T-cell populations leading to anti-inflammatory conditions. This review will highlight and summarize some of the major findings within the last decade concerning the role of select groups of bacteria including SFB, Clostridium, Bacteroides, Bifidobacterium, and Lactobacillus, and their impact on host mucosal immune systems.

Dreams for Type 1 Diabetes: Shutting Off Autoimmunity and Stimulating β-Cell Regeneration

Although not the first study to show that inhibitors of dipeptidyl peptidase IV (DPP-IV) can reverse newly diagnosed diabetes in nonobese diabetic (NOD) mice (1), a study by Tian et al. (2) in this issue of Endocrinology confirms this finding with a different DPP-IV inhibitor (NVP-DPP728) and provides explanations for the reversal by finding reduced islet inflammation, increases in CD4 CD25 FoxP3 regulatory T cells, and -cell regeneration. Impressively, 6 wk of treatment with this agent reversed diabetes in 73% of the mice. DPP-IV inhibitors are usedclinically to treatdiabetesbecause they slow the breakdown of the incretin hormone glucagon-like peptide 1 (GLP-1), which can stimulate insulin secretion, inhibit -cell apoptosis, and promote -cell replication (3). However, these inhibitors have long been known to have effects on the immune system, which presumably contributed to the marked reduction in islet inflammation. In particular, lymphocytes have a membrane-associated protein with DPP-IV activity, CD26, which has been shown to have important effects upon T-cell development, migration, and cytokine production (4). It has been previously shown that inhibition of DPP-IV can slow the progression of experimental allergic encephalitis and increase the production of TGF, which is known to suppress autoimmunity (5). In the present study, the reversal of diabetes was accompanied by a reduction of insulitis, an increase in CD4 CD25 FoxP3 regulatory T cells, and an increase in circulating TGF. Interestingly, the regulatory T cells were particularly plentiful in the thymus and pancreatic lymph nodes. It is possible that the therapeutic benefit of the present study is not completely due to the effects of DPP-IV inhibition on the immune system but in part a result of increased circulating levels of GLP-1. Inhibition of CD26 is an attractive mechanism, but the actual contribution from this specific mechanism remains to be defined. It is even possible that GLP-1 can somehow ameliorate immune killing of -cells independently of DPP-IV. We certainly have much more to learn about the effects of GLP-1 on the immune system (3). It is noteworthy that the combination of GLP-1 and gastrin has been shown to reverse diabetes in NOD mice, and this reversal was even seen in some mice with just GLP-1 treatment alone (6). The effect of GLP-1 on the target of the immune attack, the -cell, may be very important. GLP-1 is known to have an antiapoptotic effect upon -cells, probably by bolstering the insulin receptor substrate 2 signaling pathway (7, 8). Therefore, it is possible that a reduction of -cell death and less release of antigen could somehow influence the balance of T-cell regulation and slow the rate of immune destruction. Clearly, more work is needed to sort out the relative contributions of DPP-IV inhibition and GLP-1 agonism. Another addition to the equation is gastrin, the circulating levels of which can be increased with either injections of the peptide or the use of proton pump inhibitors. We know that gastrin given in combination with either epidermal growth factor or GLP-1 agonism can stimulate -cell regeneration (6, 9). Now we must ask how gastrin might contribute to reduced autoimmune destruction. The demonstration of -cell regeneration, accompanied by increased -cell replication, is similar to what has been found with some other but not all interventions that reverse diabetes in NOD mice. It seems likely that increases in -cell mass result from replication of residual -cells, although there is a provocative recent report sug-

Identification of a novel cerebral malaria susceptibility locus (Berr5) on mouse chromosome 19

Cerebral malaria (CM) is an acute, generally lethal condition characterized by high fever, seizures and coma. The genetic component to CM can be investigated in mouse models that vary in degree of susceptibility to infection with Plasmodium berghei ANKA. Using survival time to measure susceptibility in an informative F2 cross (n=257), we identified linkage to chromosome 19 (Berr5 (Berghei resistance locus 5), LOD=4.69) controlling, in part, the differential response between resistant BALB/c and susceptible C57BL/6 progenitors. BALB/c alleles convey increased survival through the cerebral phase of infection but have no quantitative effect on parasitemia during the later, anemic phase. The Berr5 locus colocalizes with three other immune loci, including Trl-4 (tuberculosis resistance), Tsiq2 (T-cell secretion of IL-4) and Eae19 (experimental allergic encephalitis 19), suggesting the possibility of a common genetic effect underlying these phenotypes. Potential positional candidates include the family of Ifit1-3 (interferon-inducible protein with tetratricopeptide repeats 1-3) and Fas.

E3 ubiquitin ligase GRAIL controls primary T cell activation and oral tolerance

T cell unresponsiveness or anergy is one of the mechanisms that maintain inactivity of self-reactive lymphocytes. E3 ubiquitin ligases are important mediators of the anergic state. The RING finger E3 ligase GRAIL is thought to selectively function in anergic T cells but its mechanism of action and its role in vivo are largely unknown. We show here that genetic deletion of Grail in mice leads not only to loss of an anergic phenotype in various models but also to hyperactivation of primary CD4(+) T cells. Grail(-/-) CD4(+) T cells hyperproliferate in vitro to TCR stimulation alone or with concomitant anti-CD28 costimulation, with transient increased survival. In vitro differentiated T helper 1 cells show slight but significant hypersecretion of IFN-gamma in Grail(-/-) mice whereas Th2 and Th17 cytokine secretions are unchanged. Consistent with defective in vitro anergy, oral tolerance is abolished in vivo in OT-II TCR transgenic Grail(-/-) mice fed with ovalbumin. In experimental allergic encephalitis, a model of organ-specific autoimmunity, oral tolerization with myelin basic protein was abrogated as well in Grail(-/-) mice. On the protein level, Grail(-/-) naïve T cells show no significant differences of total and phosphorylated levels of ZAP70, phospholipase Cgamma1, and MAP kinases p38 and JNK but elevated baseline levels of MAP kinase ERK1/2. In summary, we define a role for GRAIL in primary T cell activation, survival, and differentiation. In addition, we formally prove an indispensable role for GRAIL in T cell anergy and oral tolerance-a promising, antigen-specific strategy to treat autoimmune diseases.

Down-regulation of Gfi-1 expression by TGF-β is important for differentiation of Th17 and CD103+ inducible regulatory T cells

Growth factor independent 1 (Gfi-1), a transcriptional repressor, is transiently induced during T cell activation. Interleukin (IL) 4 further induces Gfi-1, resulting in optimal Th2 cell expansion. We report a second important function of Gfi-1 in CD4 T cells: prevention of alternative differentiation by Th2 cells, and inhibition of differentiation of naive CD4 T cells to either Th17 or inducible regulatory T (iTreg) cells. In Gfi1−/− Th2 cells, the Rorc, Il23r, and Cd103 loci showed histone 3 lysine 4 trimethylation modifications that were lacking in wild-type Th2 cells, implying that Gfi-1 is critical for epigenetic regulation of Th17 and iTreg cell–related genes in Th2 cells. Enforced Gfi-1 expression inhibited IL-17 production and iTreg cell differentiation. Furthermore, a key inducer of both Th17 and iTreg cell differentiation, transforming growth factor β, repressed Gfi-1 expression, implying a reciprocal negative regulation of CD4 T cell fate determination. Chromatin immunoprecipitation showed direct binding of the Gfi-1–lysine-specific demethylase 1 repressive complex to the intergenic region of Il17a/Il17f loci and to intron 1 of Cd103. T cell–specific Gfi1 conditional knockout mice displayed a striking delay in the onset of experimental allergic encephalitis correlated with a dramatic increase of Foxp3+CD103+ CD4 T cells. Thus, Gfi-1 plays a critical role both in enhancing Th2 cell expansion and in repressing induction of Th17 and CD103+ iTreg cells.

Development of Laquinimod for Relapsing–Remitting Multiple Sclerosis

Laquinimod, a quinoline-3-carboxamide derivative, is a new, once-daily oral immunomodulatory therapy in development for the treatment of relapsing–remitting multiple sclerosis (MS). It has demonstrated efficacy in both acute and chronic experimental allergic encephalitis and in animal models of other inflammatory autoimmune diseases. It appears to act, in part, by shifting the immune response from a Th1 to a Th2 response and does not act through nonspecific immunosuppression. In Phase II studies in relapsing forms of MS, laquinimod brought about a 60% decrease in the cumulative number of gadolinium-enhancing lesions and a 33% decrease in relapse rates. In Phase II studies it was safe and well-tolerated. The most common laboratory abnormalities were a transient rise in alanine aminotransferase and C-reactive protein that returned to normal values despite continued therapy. There was no evidence of a proinflammatory effect. Phase III clinical trials for registration are in progress. Laquinimod may find use as a first-line agent in the treatment of relapsing forms of MS.

GM-CSF mediates autoimmunity by enhancing IL-6–dependent Th17 cell development and survival

Granulocyte macrophage–colony stimulating factor (GM-CSF) is critically involved in development of organ-related autoimmune inflammatory diseases including experimental allergic encephalitis and collagen-induced arthritis. Roles of GM-CSF in the initiation and in the effector phase of the autoimmune response have been proposed. Our study was designed to investigate the mechanisms of GM-CSF in autoimmunity using a model of autoimmune heart inflammatory disease (myocarditis). The pathological sequel after immunization with heart myosin has been shown previously to depend on IL-1, IL-6, IL-23, and IL-17. We found that innate GM-CSF was critical for IL-6 and IL-23 responses by dendritic cells and generation of pathological Th17 cells in vivo. Moreover, GM-CSF promoted autoimmunity by enhancing IL-6–dependent survival of antigen specific CD4+ T cells. These results suggest a novel role for GM-CSF in promoting generation and maintenance of Th17 cells by regulation of IL-6 and IL-23 in vivo.

A GMCSF/Interleukin-15 Fusokine Leads to the Generation of a Novel Type of CD2/MHCII Immune Regulatory Cell with Potent Immune Suppressive Properties as Demonstrated in the EAE Mouse Model of Multiple Sclerosis.

Multiple sclerosis (MS) is an autoimmune disease characterised by the infiltration of autoreactive T-cell causing damages to the central nervous system. So far, interferon-β and glatiramer acetate are the only two immunomodulatory coumpounds that have been approved as non-curative disease managing strategies. Therefore, there is an urgent need for the development of novel efficient therapies that can be both safe and potent in inhibiting MS progression and promote reversal of disease state. We have recently published a report describing a novel synthetic GMCSF and IL15 Fusion Transgene (GIFT15) and have described its paradoxical and potent immune suppressive properties in vivo [Rafei et al., Blood ( March 2007)]. Its mechanism of action relies on STAT3 hyperactivation arising from aberrant signalling taking place downstream of the IL15 receptor. We have now further studied the effect of GIFT15 on mouse spleen cells in vitro and here demonstrate that it leads to the conversion of murine T-cells to a novel suppressive regulatory cell type. Indeed, GIFT15-treated splenocytes (hereafter GIFT15 regs) shed their TCR and loose expression of CD3, CD4 and CD8, retain CD2 expression and acquire expression of MHC II. Distinct to classic T-regulatory cells, GIFT15 regs do not express CD25 or FOXP3. GIFT15 regs were able to suppress an in vitro two-way MLR by a contact-dependent mechanism as well as by the contemporaneous production of interleukin (IL)-10. Furthermore, GIFT15 regs were able to block antigen-specific activation of CD4-T-cells in response to autologous macrophage stimulation. As a proof-of-principle in vivo study, GIFT15 regs were injected intravenously in mice with pre-established experimental allergic encephalitis (EAE) and disease score was monitored over time. Interestingly, mice recovered significantly faster than controls following administration GIFT15 regs and a blockade in EAE progression was also noticed over time. In conclusion, our data suggests that GIFT15 can be used as a method to ex vivo generate suppressor cells of a new type which are distinct from classic Tregs or Tr1 cells. We propose that GIFT15 regs derived from autologous lymphocytes may be exploited for the treatment of autoimmune disease such as MS and may also be of use for other autoimmune ailments as well.