Differential Runx3, Eomes, and T-bet expression subdivides MS-associated CD4+ T cells with brain-homing capacity.

Multiple sclerosis (MS) is a common and devastating chronic inflammatory disease of the CNS. CD4+ T cells are assumed to be the first to cross the blood-central nervous system (CNS) barrier and trigger local inflammation. Here, we explored how pathogenicity-associated effector programs define CD4+ T cell subsets with brain-homing ability in MS. Runx3- and Eomes-, but not T-bet-expressing CD4+ memory cells were diminished in the blood of MS patients. This decline reversed following natalizumab treatment and was supported by a Runx3+ Eomes+ T-bet- enrichment in cerebrospinal fluid samples of treatment-naïve MS patients. This transcription factor profile was associated with high granzyme K (GZMK) and CCR5 levels and was most prominent in Th17.1 cells (CCR6+ CXCR3+ CCR4-/dim ). Previously published CD28- CD4 T cells were characterized by a Runx3+ Eomes- T-bet+ phenotype that coincided with intermediate CCR5 and a higher granzyme B (GZMB) and perforin expression, indicating the presence of two separate subsets. Under steady-state conditions, granzyme Khigh Th17.1 cells spontaneously passed the blood-brain barrier in vitro. This was only found for other subsets including CD28- cells when using inflamed barriers. Altogether, CD4+ T cells contain small fractions with separate pathogenic features, of which Th17.1 seems to breach the blood-brain barrier as a possible early event in MS.

Liver X receptor beta deficiency attenuates autoimmune-associated neuroinflammation in a T cell-dependent manner.

The initiation and progression of autoimmune disorders such as multiple sclerosis (MS) is linked to aberrant cholesterol metabolism and overt inflammation. Liver X receptors (LXR) are nuclear receptors that function at the crossroads of cholesterol metabolism and immunity, and their activation is considered a promising therapeutic strategy to attenuate autoimmunity. However, despite clear functional heterogeneity and cell-specific expression profiles, the impact of the individual LXR isoforms on autoimmunity remains poorly understood. Here, we show that LXRα and LXRß have an opposite impact on immune cell function and disease severity in the experimental autoimmune encephalomyelitis model, an experimental MS model. While Lxrα deficiency aggravated disease pathology and severity, absence of Lxrß was protective. Guided by flow cytometry and by using cell-specific knockout models, reduced disease severity in Lxrß-deficient mice was primarily attributed to changes in peripheral T cell physiology and occurred independent from alterations in microglia function. Collectively, our findings indicate that LXR isoforms play functionally non-redundant roles in autoimmunity, potentially having broad implications for the development of LXR-based therapeutic strategies aimed at dampening autoimmunity and neuroinflammation.

Treg-Resistant Cytotoxic CD4+ T Cells Dictate T Helper Cells in Their Vicinity: TH17 Skewing and Modulation of Proliferation.

Cytotoxic CD4+ T cells (CD4 CTL) are terminally differentiated T helper cells that contribute to autoimmune diseases, such as multiple sclerosis. We developed a novel triple co-culture transwell assay to study mutual interactions between CD4 CTL, conventional TH cells, and regulatory T cells (Tregs) simultaneously. We show that, while CD4 CTL are resistant to suppression by Tregs in vitro, the conditioned medium of CD4 CTL accentuates the suppressive phenotype of Tregs by upregulating IL-10, Granzyme B, CTLA-4, and PD-1. We demonstrate that CD4 CTL conditioned medium skews memory TH cells to a TH17 phenotype, suggesting that the CD4 CTL induce bystander polarization. In our triple co-culture assay, the CD4 CTL secretome promotes the proliferation of TH cells, even in the presence of Tregs. However, when cell-cell contact is established between CD4 CTL and TH cells, the proliferation of TH cells is no longer increased and Treg-mediated suppression is restored. Taken together, our results suggest that when TH cells acquire cytotoxic properties, these Treg-resistant CD4 CTL affect the proliferation and phenotype of conventional TH cells in their vicinity. By creating such a pro-inflammatory microenvironment, CD4 CTL may favor their own persistence and expansion, and that of other potentially pathogenic TH cells, thereby contributing to pathogenic responses in autoimmune disorders.

Altered PPARγ Expression Promotes Myelin-Induced Foam Cell Formation in Macrophages in Multiple Sclerosis.

Macrophages play a crucial role during the pathogenesis of multiple sclerosis (MS), a neuroinflammatory autoimmune disorder of the central nervous system. Important regulators of the metabolic and inflammatory phenotype of macrophages are liver X receptors (LXRs) and peroxisome proliferator-activated receptors (PPARs). Previously, it has been reported that PPARγ expression is decreased in peripheral blood mononuclear cells of MS patients. The goal of the present study was to determine to what extent PPARγ, as well as the closely related nuclear receptors PPARα and ß and LXRα and ß, are differentially expressed in monocytes from MS patients and how this change in expression affects the function of monocyte-derived macrophages. We demonstrate that monocytes of relapsing-remitting MS patients display a marked decrease in PPARγ expression, while the expression of PPARα and LXRα/ß is not altered. Interestingly, exposure of monocyte-derived macrophages from healthy donors to MS-associated proinflammatory cytokines mimicked this reduction in PPARγ expression. While a reduced PPARγ expression did not affect the inflammatory and phagocytic properties of myelin-loaded macrophages, it did impact myelin processing by increasing the intracellular cholesterol load of myelin-phagocytosing macrophages. Collectively, our findings indicate that an inflammation-induced reduction in PPARγ expression promotes myelin-induced foam cell formation in macrophages in MS.

Age-Associated B Cells with Proinflammatory Characteristics Are Expanded in a Proportion of Multiple Sclerosis Patients.

Immune aging occurs in the elderly and in autoimmune diseases. Recently, IgD-CD27- (double negative, DN) and CD21-CD11c+ (CD21low) B cells were described as age-associated B cells with proinflammatory characteristics. This study investigated the prevalence and functional characteristics of DN and CD21low B cells in multiple sclerosis (MS) patients. Using flow cytometry, we demonstrated a higher proportion of MS patients younger than 60 y with peripheral expansions of DN (8/41) and CD21low (9/41) B cells compared with age-matched healthy donors (1/33 and 2/33, respectively), which indicates an increase in age-associated B cells in MS patients. The majority of DN B cells had an IgG+ memory phenotype, whereas CD21low B cells consisted of a mixed population of CD27- naive, CD27+ memory, IgG+, and IgM+ cells. DN B cells showed similar (MS patients) or increased (healthy donors) MHC-II expression as class-switched memory B cells and intermediate costimulatory molecule expression between naive and class-switched memory B cells, indicating their potential to induce (proinflammatory) T cell responses. Further, DN B cells produced proinflammatory and cytotoxic cytokines following ex vivo stimulation. Increased frequencies of DN and CD21low B cells were found in the cerebrospinal fluid of MS patients compared with paired peripheral blood. In conclusion, a proportion of MS patients showed increased peripheral expansions of age-associated B cells. DN and CD21low B cell frequencies were further increased in MS cerebrospinal fluid. These cells could contribute to inflammation by induction of T cell responses and the production of proinflammatory cytokines.

Circulating Follicular Regulatory T Cells Are Defective in Multiple Sclerosis.

Follicular regulatory T cells (TFR) have been extensively characterized in mice and participate in germinal center responses by regulating the maturation of B cells and production of (auto)antibodies. We report that circulating TFR are phenotypically distinct from tonsil-derived TFR in humans. They have a lower expression of follicular markers, and display a memory phenotype and lack of high expression of B cell lymphoma 6 and ICOS. However, the suppressive function, expression of regulatory markers, and FOXP3 methylation status of blood TFR is comparable with tonsil-derived TFR. Moreover, we show that circulating TFR frequencies increase after influenza vaccination and correlate with anti-flu Ab responses, indicating a fully functional population. Multiple sclerosis (MS) was used as a model for autoimmune disease to investigate alterations in circulating TFR. MS patients had a significantly lower frequency of circulating TFR compared with healthy control subjects. Furthermore, the circulating TFR compartment of MS patients displayed an increased proportion of Th17-like TFR. Finally, TFR of MS patients had a strongly reduced suppressive function compared with healthy control subjects. We conclude that circulating TFR are a circulating memory population derived from lymphoid resident TFR, making them a valid alternative to investigate alterations in germinal center responses in the context of autoimmune diseases, and TFR impairment is prominent in MS.

IL-15 amplifies the pathogenic properties of CD4+CD28- T cells in multiple sclerosis.

CD4(+)CD28(-) T cells arise through repeated antigenic stimulation and are present in diseased tissues of patients with various autoimmune disorders, including multiple sclerosis (MS). These cells are believed to have cytotoxic properties that contribute to the pathogenic damaging of the target organ. Endogenous cues that are increased in the diseased tissue may amplify the activity of CD4(+)CD28(-) T cells. In this study, we focused on IL-15, a cytotoxicity-promoting cytokine that is increased in the serum and cerebrospinal fluid of MS patients. Using immunohistochemistry, we demonstrate that IL-15 is mainly produced by astrocytes and infiltrating macrophages in inflammatory lesions of MS patients. Moreover, in vitro transmigration studies reveal that IL-15 selectively attracts CD4(+)CD28(-) T cells of MS patients, but not of healthy individuals. IL-15 further induces the expression of chemokine receptors and adhesion molecules on CD4(+)CD28(-) T cells, as investigated using flow cytometry, resulting in enhanced migration over a monolayer of human brain endothelial cells. Finally, flow cytometric analyses revealed that IL-15 increases the proliferation and production of GM-CSF, expression of cytotoxic molecules (NKG2D, perforin, and granzyme B), and degranulation capacity of CD4(+)CD28(-) T cells. Taken together, these findings indicate that increased peripheral and local levels of IL-15 amplify the pathogenic potential of CD4(+)CD28(-) T cells, thus contributing to tissue damage in MS brain lesions.

B cells of multiple sclerosis patients induce autoreactive proinflammatory T cell responses.

Antibody-independent B cell functions play an important role in multiple sclerosis (MS) pathogenesis. In this study, B cell antigen presentation and costimulation in MS were studied. Peripheral blood B cells of MS patients showed increased expression of costimulatory CD86 and CD80 molecules compared with healthy controls (HC). In MS cerebrospinal fluid (CSF), 12-fold and 2-fold increases in CD86+ and CD80+ B cells, respectively, were evidenced compared with peripheral blood. Further, B cells from MS patients induced proinflammatory T cells in response to myelin basic protein (MBP). Immunomodulatory treatment restored B cell costimulatory molecule expression and caused significantly reduced B cell induced T cell responses. Together, these results demonstrate the potential of B cells from MS patients to induce autoreactive proinflammatory T cell responses. Immunomodulatory therapy abrogated this effect, emphasizing the importance of B cell antigen presentation and costimulation in MS pathology.

Autoantibodies to two novel peptides in seronegative and early rheumatoid arthritis.

OBJECTIVES: Despite recent progress in biomarker discovery for RA diagnostics, still over one-third of RA patients-and even more in early disease-present without RF or ACPA. The aim of this study was to confirm the presence of previously identified autoantibodies to novel Hasselt University (UH) peptides in early and seronegative RA. METHODS: Screening for antibodies against novel UH peptides UH-RA.1, UH-RA.9, UH-RA.14 and UH-RA.21, was performed in two large independent cohorts. Peptide ELISAs were developed to screen for the presence of antibodies to UH-RA peptides. First, 292 RA patients (including 39 early patients), 90 rheumatic and 97 healthy controls from UH were studied. Antibody reactivity to two peptides (UH-RA.1 and UH-RA.21) was also evaluated in 600 RA patients, 309 patients with undifferentiated arthritis and 157 rheumatic controls from the Leiden Early Arthritis Clinic cohort. RESULTS: In both cohorts, 38% of RA patients were seronegative for RF and ACPA. Testing for autoantibodies to UH-RA.1 and UH-RA.21 reduced the serological gap from 38% to 29% in the UH cohort (P = 0.03) and from 38% to 32% in the Leiden Early Arthritis Clinic cohort (P = 0.01). Furthermore, 19-33% of early RA patients carried antibodies to these peptides. Specificities in rheumatic controls ranged from 82 to 96%. Whereas antibodies against UH-RA.1 were related to remission, anti-UH-RA.21 antibodies were associated with inflammation, joint erosion and higher tender and swollen joint counts. CONCLUSION: This study validates the presence of antibody reactivity to novel UH-RA peptides in seronegative and early RA. This might reinforce current diagnostics and improve early diagnosis and intervention in RA.

Sperm-associated antigen 16 is a novel target of the humoral autoimmune response in multiple sclerosis.

We have previously identified eight novel autoantibody targets in the cerebrospinal fluid of multiple sclerosis (MS) patients, including sperm-associated Ag 16 (SPAG16). In the current study, we further investigated the autoantibody response against SPAG16-a protein with unknown function in the CNS-and its expression in MS pathology. Using isoelectric focusing, we detected SPAG16-specific oligoclonal bands in the cerebrospinal fluid of 5 of 23 MS patients (22%). Analysis of the anti-SPAG16 Ab reactivity in the plasma of a total of 531 donors using ELISA demonstrated significantly elevated anti-SPAG16 Ab levels (p = 0.002) in 32 of 153 MS patients (21%) compared with all other control groups with 95% specificity for the disease. To investigate the pathologic relevance of anti-SPAG16 Abs in vivo, anti-SPAG16 Abs were injected in mice with experimental autoimmune encephalomyelitis, resulting in a significant disease exacerbation. Finally, we demonstrated a consistent upregulation of SPAG16 in MS brain and experimental autoimmune encephalomyelitis spinal cord lesions, more specifically in reactive astrocytes. We conclude that SPAG16 is a novel autoantibody target in a subgroup of MS patients and in combination with other diagnostic criteria, elevated levels of anti-SPAG16 Abs could be used as a biomarker for diagnosis. Furthermore, the pathologic relevance of anti-SPAG16 Abs was shown in vivo.

Oncostatin M protects against demyelination by inducing a protective microglial phenotype.

Multiple sclerosis (MS) is a chronic disabling disease of the central nervous system (CNS), in which destruction of myelin sheaths leads to disturbed axonal conduction. Available MS therapies modulate the immune response, but are unable to prevent neurological decline. Therefore, great efforts are made to develop therapies that limit demyelination and axonal degeneration. Oncostatin M (OSM), a member of the interleukin (IL)-6 cytokine family, is produced in demyelinating lesions of MS patients and stimulates neuronal survival. In this study, we reveal that the OSM receptor (OSMR) was robustly upregulated on microglia/macrophages and astrocytes in the cuprizone-induced demyelination model. While OSMR deficiency led to aggravated demyelination, CNS-targeted OSM treatment largely prevented demyelination. OSM treatment increased IL-4 expression and induced polarization of myeloid cells towards an anti-inflammatory M2 phenotype in vivo. This study reveals a previously uncharacterized and protective role for OSM during demyelination, and indicates that OSM is a promising therapeutic candidate to limit CNS damage in demyelinating diseases including MS.

Leukemia inhibitory factor tips the immune balance towards regulatory T cells in multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS), for which current treatments are unable to prevent disease progression. Based on its neuroprotective and neuroregenerating properties, leukemia inhibitory factor (LIF), a member of the interleukin-6 (IL-6) cytokine family, is proposed as a novel candidate for MS therapy. However, its effect on the autoimmune response remains unclear. In this study, we determined how LIF modulates T cell responses that play a crucial role in the pathogenesis of MS. We demonstrate that expression of the LIF receptor was strongly increased on immune cells of MS patients. LIF treatment potently boosted the number of regulatory T cells (Tregs) in CD4(+) T cells isolated from healthy controls and MS patients with low serum levels of IL-6. Moreover, IL-6 signaling was reduced in the donors that responded to LIF treatment in vitro. Our data together with previous findings revealing that IL-6 inhibits Treg development, suggest an opposing function of LIF and IL-6. In a preclinical animal model of MS we shifted the LIF/IL-6 balance in favor of LIF by CNS-targeted overexpression. This increased the number of Tregs in the CNS during active autoimmune responses and reduced disease symptoms. In conclusion, our data show that LIF downregulates the autoimmune response by enhancing Treg numbers, providing further impetus for the use of LIF as a novel treatment for MS and other autoimmune diseases.

Identification of a genetic variant for joint damage progression in autoantibody-positive rheumatoid arthritis.

BACKGROUND: Joint destruction is a hallmark of autoantibody-positive rheumatoid arthritis (RA), though the severity is highly variable between patients. The processes underlying these interindividual differences are incompletely understood. METHODS: We performed a genome-wide association study on the radiological progression rate in 384 autoantibody-positive patients with RA. In stage-II 1557 X-rays of 301 Dutch autoantibody-positive patients with RA were studied and in stage-III 861 X-rays of 742 North American autoantibody-positive patients with RA. Sperm-Associated Antigen 16 (SPAG16) expression in RA synovium and fibroblast-like synoviocytes (FLS) was examined using Real-Time Quantitative Polymerase Chain Reaction (RT-qPCR) and immunohistochemistry. FLS secrete metalloproteinases that degrade cartilage and bone. SPAG16 genotypes were related to matrix metalloproteinase (MMP)-3 and MMP-1 expression by FLS in vitro and MMP-3 production ex vivo. RESULTS: A cluster of single nucleotide polymorphisms (SNPs) at 2q34, located at SPAG16, associated with the radiological progression rate; rs7607479 reached genome-wide significance. A protective role of rs7607479 was replicated in European and North American patients with RA. Per minor allele, patients had a 0.78-fold (95% CI 0.67 to 0.91) progression rate over 7 years. mRNA and protein expression of SPAG16 in RA synovium and FLS was verified. FLS carrying the minor allele secreted less MMP-3 (p=1.60×10(-2)). Furthermore, patients with RA carrying the minor allele had lower serum levels of MMP-3 (p=4.28×10(-2)). In a multivariate analysis on rs7607479 and MMP-3, only MMP-3 associated with progression (p=2.77×10(-4)), suggesting that the association between SPAG16-rs7607479 and joint damage is mediated via an effect on MMP-3 secretion. CONCLUSIONS: Genetic and functional analyses indicate that SPAG16 influences MMP-3 regulation and protects against joint destruction in autoantibody-positive RA. These findings could enhance risk stratification in autoantibody-positive RA.

Clonal heterogeneity of thymic B cells from early-onset myasthenia gravis patients with antibodies against the acetylcholine receptor.

Myasthenia gravis (MG) with antibodies against the acetylcholine receptor (AChR-MG) is considered as a prototypic autoimmune disease. The thymus is important in the pathophysiology of the disease since thymus hyperplasia is a characteristic of early-onset AChR-MG and patients often improve after thymectomy. We hypothesized that thymic B cell and antibody repertoires of AChR-MG patients differ intrinsically from those of control individuals. Using immortalization with Epstein-Barr Virus and Toll-like receptor 9 activation, we isolated and characterized monoclonal B cell lines from 5 MG patients and 8 controls. Only 2 of 570 immortalized B cell clones from MG patients produced antibodies against the AChR (both clones were from the same patient), suggesting that AChR-specific B cells are not enriched in the thymus. Surprisingly, many B cell lines from both AChR-MG and control thymus samples displayed reactivity against striated muscle proteins. Striational antibodies were produced by 15% of B cell clones from AChR-MG versus 6% in control thymus. The IgVH gene sequence analysis showed remarkable similarities, concerning VH family gene distribution, mutation frequency and CDR3 composition, between B cells of AChR-MG patients and controls. MG patients showed clear evidence of clonal B cell expansion in contrast to controls. In this latter aspect, MG resembles multiple sclerosis and clinically isolated syndrome, but differs from systemic lupus erythematosus. Our results support an antigen driven immune response in the MG thymus, but the paucity of AChR-specific B cells, in combination with the observed polyclonal expansions suggest a more diverse immune response than expected.

Macrophage subsets and microglia in multiple sclerosis.

Along with microglia and monocyte-derived macrophages, macrophages in the perivascular space, choroid plexus, and meninges are the principal effector cells in neuroinflammatory and neurodegenerative disorders. These phagocytes are highly heterogeneous cells displaying spatial- and temporal-dependent identities in the healthy, injured, and inflamed CNS. In the last decade, researchers have debated on whether phagocytes subtypes and phenotypes are pathogenic or protective in CNS pathologies. In the context of this dichotomy, we summarize and discuss the current knowledge on the spatiotemporal physiology of macrophage subsets and microglia in the healthy and diseased CNS, and elaborate on factors regulating their behavior. In addition, the impact of macrophages present in lymphoid organs on CNS pathologies is defined. The prime focus of this review is on multiple sclerosis (MS), which is characterized by inflammation, demyelination, neurodegeneration, and CNS repair, and in which microglia and macrophages have been extensively scrutinized. On one hand, microglia and macrophages promote neuroinflammatory and neurodegenerative events in MS by releasing inflammatory mediators and stimulating leukocyte activity and infiltration into the CNS. On the other hand, microglia and macrophages assist in CNS repair through the production of neurotrophic factors and clearance of inhibitory myelin debris. Finally, we define how microglia and macrophage physiology can be harnessed for new therapeutics aimed at suppressing neuroinflammatory and cytodegenerative events, as well as promoting CNS repair. We conclude that microglia and macrophages are highly dynamic cells displaying disease stage and location-specific fates in neurological disorders. Changing the physiology of divergent phagocyte subsets at particular disease stages holds promise for future therapeutics for CNS pathologies.

HLA-E restricted CD8+ T cell subsets are phenotypically altered in multiple sclerosis patients.

BACKGROUND: The importance of Qa-1 restricted CD8(+) T cells in regulating autoreactive T cell responses has been demonstrated in animal models for autoimmune disorders, including multiple sclerosis (MS). OBJECTIVE: We hypothesize that their human variant, HLA-E restricted CD8(+) T cells, fulfills a similar regulatory role in man and that these cells are of importance in MS. METHODS: A large cohort of MS patients and healthy controls was genotyped for the two known HLA-E polymorphisms. Flow cytometry was used to determine HLA-E expression kinetics and to phenotype HLA-E restricted CD8(+) T cells. Immunohistochemistry was performed to investigate HLA-E expression in the central nervous system (CNS) of MS patients. RESULTS: HLA-E is upregulated on immune cells upon in vitro activation and this upregulation is polymorphism-dependent for T and B cells. T and B cells in lesions of MS patients show enhanced HLA-E expression. Furthermore, NKG2C(+)CD8(+) T cells of MS patients have a significantly lower Foxp3 expression, while NKG2A(+)CD8(+) T cells of MS patients produce higher levels of pro-inflammatory cytokines compared to those of healthy individuals. CONCLUSION: Our study indicates that the HLA-E system is altered in MS and could play a regulatory role in disease.

Circulating dendritic cells of multiple sclerosis patients are proinflammatory and their frequency is correlated with MS-associated genetic risk factors.

BACKGROUND: The role of the adaptive immune system and more specifically T cells in the pathogenesis of multiple sclerosis (MS) has been studied extensively. Emerging evidence suggests that dendritic cells (DCs), which are innate immune cells, also contribute to MS. OBJECTIVES: This study aimed to characterize circulating DC populations in MS and to investigate the contribution of MS-associated genetic risk factors to DCs. METHODS: Ex vivo analysis of conventional (cDCs) and plasmacytoid DCs (pDCs) was carried out on peripheral blood of MS patients (n = 110) and age- and gender-matched healthy controls (n = 112). RESULTS: Circulating pDCs were significantly decreased in patients with chronic progressive MS compared to relapsing-remitting MS and healthy controls. While no differences in cDCs frequency were found between the different study groups, HLA-DRB1*1501(+) MS patients and patients not carrying the protective IL-7Rα haplotype 2 have reduced frequencies of circulating cDCs and pDCs, respectively. MS-derived DCs showed enhanced IL-12p70 production upon TLR ligation and had an increased expression of the migratory molecules CCR5 and CCR7 as well as an enhanced in vitro chemotaxis. CONCLUSION: DCs in MS are in a pro-inflammatory state, have a migratory phenotype and are affected by genetic risk factors, thereby contributing to pathogenic responses.

Which immune cells matter? The immunopathogenesis of multiple sclerosis.

Multiple sclerosis (MS) is a complex disease of the central nervous system (CNS), which is believed to be immune-mediated. While CD4+ T cells have been the main suspects for years, there is ample evidence that other immune cells (including those of the innate immune system) play a contributing or regulating role in this disease. After a general introduction, this review focuses on different immune cell subsets implicated in MS pathogenesis and on current and future possibilities to target them for therapeutic use.

Identification of coronin-1a as a novel antibody target for clinically isolated syndrome and multiple sclerosis.

Recently, we identified the mimotope UH-CIS6 as a novel candidate antibody target for clinically isolated syndrome (CIS) and relapsing-remitting (RR) multiple sclerosis (MS). The purpose of this study was to further validate UH-CIS6 as an antibody target for CIS and MS and to identify the in vivo antibody target of UH-CIS6. First, a UH-CIS6 peptide ELISA was optimized. Next, we investigated the antibody response toward UH-CIS6 in cerebrospinal fluid (CSF) from patients with CIS (n = 20), MS (n = 43) and other neurological diseases (n = 42). Immunoprecipitation of anti-UH-CIS6 antibodies on a normal human brain lysate was performed to identify the in vivo antibody target of UH-CIS6. The cellular expression of an in vivo candidate target was investigated by immunohistochemistry using MS brain tissue sections. Antibody reactivity toward UH-CIS6 was detected in a significantly increased proportion of CSF samples from CIS and RR-MS patients as compared with neurological controls (p = 0.046). We identified and confirmed coronin-1a as the in vivo antibody target for UH-CIS6. Furthermore, coronin-1a was expressed by T cells and macrophages in an active MS lesion. Together, these results demonstrate that coronin-1a is a novel antibody target for CIS and MS.

Local overexpression of interleukin-11 in the central nervous system limits demyelination and enhances remyelination.

Demyelination is one of the pathological hallmarks of multiple sclerosis (MS). To date, no therapy is available which directly potentiates endogenous remyelination. Interleukin-11 (IL-11), a member of the gp130 family of cytokines, is upregulated in MS lesions. Systemic IL-11 treatment was shown to ameliorate clinical symptoms in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. IL-11 modulates immune cells and protects oligodendrocytes in vitro. In this study, the cuprizone-induced demyelination mouse model was used to elucidate effects of IL-11 on de- and remyelination, independent of the immune response. Prophylactic-lentiviral- (LV-) mediated overexpression of IL-11 in mouse brain significantly limited acute demyelination, which was accompanied with the preservation of CC1(+) mature oligodendrocytes (OLs) and a decrease in microglial activation (Mac-2(+)). We further demonstrated that IL-11 directly reduces myelin phagocytosis in vitro. When IL-11 expressing LV was therapeutically applied in animals with extensive demyelination, a significant enhancement of remyelination was observed as demonstrated by Luxol Fast Blue staining and electron microscopy imaging. Our results indicate that IL-11 promotes maturation of NG2(+) OPCs into myelinating CC1(+) OLs and may thus explain the enhanced remyelination. Overall, we demonstrate that IL-11 is of therapeutic interest for MS and other demyelinating diseases by limiting demyelination and promoting remyelination.