Oral Cladribine Impairs Intermediate, but Not Conventional, Monocyte Transmigration in Multiple Sclerosis Patients across a Model Blood-Brain Barrier.

Multiple sclerosis (MS) is a disease in which the immune system damages components of the central nervous system (CNS), leading to the destruction of myelin and the formation of demyelinating plaques. This often occurs in episodic "attacks" precipitated by the transmigration of leukocytes across the blood-brain barrier (BBB), and repeated episodes of demyelination lead to substantial losses of axons within and removed from plaques, ultimately leading to progressive neurological dysfunction. Within leukocyte populations, macrophages and T and B lymphocytes are the predominant effectors. Among current immunotherapies, oral cladribine's impact on lymphocytes is well characterised, but little is known about its impact on other leukocytes such as monocytes and dendritic cells (DCs). The aim of this study was to determine the transmigratory ability of monocyte and DC subsets in healthy subjects and untreated and cladribine-treated relapse-remitting MS (RRMS) patients using a well-characterised model of the BBB. Peripheral blood mononuclear cells from subjects were added to an in vitro transmigration assay to assess cell migration. Our findings show that while prior treatment with oral cladribine inhibits the migration of intermediate monocytes, it has no impact on the transmigration of DC subsets. Overall, our data indicate a previously unrecognised role of cladribine on intermediate monocytes, known to accumulate in the brain active MS lesions.

Peripheral B-cell dysregulation is associated with relapse after long-term quiescence in patients with multiple sclerosis.

B cells play a major role in multiple sclerosis (MS), with many successful therapeutics capable of removing them from circulation. One such therapy, alemtuzumab, is thought to reset the immune system without the need for ongoing therapy in a proportion of patients. The exact cells contributing to disease pathogenesis and quiescence remain to be identified. We utilized mass cytometry to analyze B cells from the blood of patients with relapse-remitting MS (RRMS) before and after alemtuzumab treatment, and during relapse. A complementary RRMS cohort was analyzed by single-cell RNA sequencing. The R package "Spectre" was used to analyze these data, incorporating FlowSOM clustering, sparse partial least squares-discriminant analysis and permutational multivariate analysis of variance. Immunoglobulin (Ig)A+ and IgG1 + B-cell numbers were altered, including higher IgG1 + B cells during relapse. B-cell linker protein (BLNK), CD40 and CD210 expression by B cells was lower in patients with RRMS compared with non-MS controls, with similar results at the transcriptomic level. Finally, alemtuzumab restored BLNK, CD40 and CD210 expression by IgA+ and IgG1 + B cells, which was altered again during relapse. These data suggest that impairment of IgA+ and IgG1 + B cells may contribute to MS pathogenesis, which can be restored by alemtuzumab.

Differential Toxicity of Antibodies to the Prion Protein.

Antibodies against the prion protein PrPC can antagonize prion replication and neuroinvasion, and therefore hold promise as possible therapeutics against prion diseases. However, the safety profile of such antibodies is controversial. It was originally reported that the monoclonal antibody D13 exhibits strong target-related toxicity, yet a subsequent study contradicted these findings. We have reported that several antibodies against certain epitopes of PrPC, including antibody POM1, are profoundly neurotoxic, yet antibody ICSM18, with an epitope that overlaps with POM1, was reported to be innocuous when injected into mouse brains. In order to clarify this confusing situation, we assessed the neurotoxicity of antibodies D13 and ICSM18 with dose-escalation studies using diffusion-weighted magnetic resonance imaging and various histological techniques. We report that both D13 and ICSM18 induce rapid, dose-dependent, on-target neurotoxicity. We conclude that antibodies directed to this region may not be suitable as therapeutics. No such toxicity was found when antibodies against the flexible tail of PrPC were administered. Any attempt at immunotherapy or immunoprophylaxis of prion diseases should account for these potential untoward effects.

Incidence and prevalence of NMOSD in Australia and New Zealand.

OBJECTIVES: We have undertaken a clinic-based survey of neuromyelitis optica spectrum disorders (NMOSDs) in Australia and New Zealand to establish incidence and prevalence across the region and in populations of differing ancestry. BACKGROUND: NMOSD is a recently defined demyelinating disease of the central nervous system (CNS). The incidence and prevalence of NMOSD in Australia and New Zealand has not been established. METHODS: Centres managing patients with demyelinating disease of the CNS across Australia and New Zealand reported patients with clinical and laboratory features that were suspicious for NMOSD. Testing for aquaporin 4 antibodies was undertaken in all suspected cases. From this group, cases were identified who fulfilled the 2015 Wingerchuk diagnostic criteria for NMOSD. A capture-recapture methodology was used to estimate incidence and prevalence, based on additional laboratory identified cases. RESULTS: NMOSD was confirmed in 81/170 (48%) cases referred. Capture-recapture analysis gave an adjusted incidence estimate of 0.37 (95% CI 0.35 to 0.39) per million per year and a prevalence estimate for NMOSD of 0.70 (95% CI 0.61 to 0.78) per 100 000. NMOSD was three times more common in the Asian population (1.57 (95% CI 1.15 to 1.98) per 100 000) compared with the remainder of the population (0.57 (95% CI 0.50 to 0.65) per 100 000). The latitudinal gradient evident in multiple sclerosis was not seen in NMOSD. CONCLUSIONS: NMOSD incidence and prevalence in Australia and New Zealand are comparable with figures from other populations of largely European ancestry. We found NMOSD to be more common in the population with Asian ancestry.

Plasma levels of endothelial and B-cell-derived microparticles are restored by fingolimod treatment in multiple sclerosis patients.

BACKGROUND: No molecular marker can monitor disease progression and treatment efficacy in multiple sclerosis (MS). Circulating microparticles represent a potential snapshot of disease activity at the blood brain barrier. OBJECTIVES AND METHODS: To profile plasma microparticles by flow cytometry in MS and determine how fingolimod could impact endothelial microparticles production. RESULTS: In non-treated MS patients compared to healthy and fingolimod-treated patients, endothelial microparticles were higher, while B-cell-microparticle numbers were lower. Fingolimod dramatically reduced tumour necrosis factor (TNF)-induced endothelial microparticle release in vitro. CONCLUSION: Fingolimod restored dysregulated endothelial and B-cell-microparticle numbers, which could serve as a biomarker in MS.

Autosomal dominant congenital spinal muscular atrophy: a true form of spinal muscular atrophy caused by early loss of anterior horn cells.

Autosomal dominant congenital spinal muscular atrophy is characterized by predominantly lower limb weakness and wasting, and congenital or early-onset contractures of the hip, knee and ankle. Mutations in TRPV4, encoding a cation channel, have recently been identified in one large dominant congenital spinal muscular atrophy kindred, but the genetic basis of dominant congenital spinal muscular atrophy in many families remains unknown. It has been hypothesized that differences in the timing and site of anterior horn cell loss in the central nervous system account for the variations in clinical phenotype between different forms of spinal muscular atrophy, but there has been a lack of neuropathological data to support this concept in dominant congenital spinal muscular atrophy. We report clinical, electrophysiology, muscle magnetic resonance imaging and histopathology findings in a four generation family with typical dominant congenital spinal muscular atrophy features, without mutations in TRPV4, and in whom linkage to other known dominant neuropathy and spinal muscular atrophy genes has been excluded. The autopsy findings in the proband, who died at 14 months of age from an unrelated illness, provided a rare opportunity to study the neuropathological basis of dominant congenital spinal muscular atrophy. There was a reduction in anterior horn cell number in the lumbar and, to a lesser degree, the cervical spinal cord, and atrophy of the ventral nerve roots at these levels, in the absence of additional peripheral nerve pathology or abnormalities elsewhere along the neuraxis. Despite the young age of the child at the time of autopsy, there was no pathological evidence of ongoing loss or degeneration of anterior horn cells suggesting that anterior horn cell loss in dominant congenital spinal muscular atrophy occurs in early life, and is largely complete by the end of infancy. These findings confirm that dominant congenital spinal muscular atrophy is a true form of spinal muscular atrophy caused by a loss of anterior horn cells localized to lumbar and cervical regions early in development.

Cladribine Reduces Trans-Endothelial Migration of Memory T Cells across an In Vitro Blood-Brain Barrier.

Multiple sclerosis (MS) is a chronic, demyelinating disease of the central nervous system (CNS) induced by immune dysregulation. Cladribine has been championed for its clinical efficacy with relatively minor side effects in treating MS. Although it is proposed that cladribine exerts an anti-migratory effect on lymphocytes at the blood-brain barrier (BBB) in addition to its lymphocyte-depleting and modulating effects, this has not been properly studied. Here, we aimed to determine if cladribine treatment influences trans-endothelial migration of T cell subsets across an inflamed BBB. Human brain endothelial cells stimulated with pro-inflammatory cytokines were used to mimic the BBB. Peripheral blood mononuclear cells were obtained from healthy controls, untreated and cladribine-treated MS patients. The trans-endothelial migration of CD4+ effector memory T (TEM) and CD8+ central memory T (TCM) cells was reduced in cladribine-treated MS patients. CD28 expression was decreased on both CD4+ TEM and CD8+ TCM cells, suggesting lowered peripheral activation of these cells thereby maintaining the integrity of the BBB. In addition, these cells have likely reconstituted following cladribine treatment, revealing a long-term anti-migratory effect. These results highlight new mechanisms by which cladribine acts to control MS pathogenesis.

Trans-Endothelial Migration of Memory T Cells Is Impaired in Alemtuzumab-Treated Multiple Sclerosis Patients.

The breakdown of the blood-brain barrier (BBB) and the trans-endothelial migration of lymphocytes are central events in the development of multiple sclerosis (MS). Autoreactive T cells are major players in MS pathogenesis, which are rapidly depleted following alemtuzumab treatment. This modulation, in turn, inhibits CNS inflammation, but alemtuzumab's effect on T cell migration into the CNS has been less studied. Human brain endothelial cells were stimulated with pro-inflammatory cytokines to mimic an inflamed BBB in vitro. Peripheral blood mononuclear cells from healthy controls, untreated or alemtuzumab-treated patients with relapsing-remitting MS (RRMS) were added to the BBB model to assess their transmigratory capacity. Here, the migration of CD4+ effector memory T (TEM) and CD8+ central memory T (TCM) cells across the BBB was impaired in alemtuzumab-treated patients. Naïve T (Tnaïve) cells were unable to migrate across all groups. CD38 was lowly expressed on CD8+ TCM cells, particularly for RRMS patients, compared to CD8+ Tnaïve cells. CD62L expression was lower on CD4+ TEM cells than CD4+ Tnaïve cells and decreased further in alemtuzumab-treated patients. These data suggest that repopulated memory T cells are phenotypically different from naïve T cells, which may affect their transmigration across the BBB in vitro.

Circulating CCR6+ILC proportions are lower in multiple sclerosis patients.

Objectives: The role of innate lymphoid cells (ILC), particularly helper ILC, in the pathogenesis of multiple sclerosis (MS) is not well understood. Here, we present a comprehensive analysis of peripheral ILC subsets in MS patients prior and after alemtuzumab administration using mass cytometry. Methods: Circulating ILC were analysed by mass cytometry in MS patients before and after alemtuzumab. These were compared with non-MS controls. MS-related shifts among ILC immunophenotypes were further elucidated by fast interpolation-based t-SNE (Flt-SNE) dimensionality reduction. Results: Neither natural killer (NK) cells nor helper ILC (ILC1, ILC2 and ILC3) levels were altered following alemtuzumab treatment. However, CD56bright NK cell expansions were observed in relapsing patients. MS patients prior to alemtuzumab further displayed proportional shifts from ILC1 to ILC2, with MS-associated decreases in CCR6+ helper ILC proportions. Conclusion: CD56bright NK cells during relapse indicate an immediate response to disease reactivation, while CCR6-related shifts among helper ILC suggest altered ILC migration to the CNS during MS.

Circulating Memory B Cells in Early Multiple Sclerosis Exhibit Increased IgA+ Cells, Globally Decreased BAFF-R Expression and an EBV-Related IgM+ Cell Signature.

Multiple sclerosis (MS) is an immune-mediated inflammatory disease of the central nervous system that results in demyelination of axons, inefficient signal transmission and reduced muscular mobility. Recent findings suggest that B cells play a significant role in disease development and pathology. To further explore this, B cell profiles in peripheral blood from 28 treatment-naive patients with early MS were assessed using flow cytometry and compared to 17 healthy controls. Conventional and algorithm-based analysis revealed a significant increase in MS patients of IgA+ memory B cells (MBC) including CD27+, CD27- and Tbet+ subsets. Screening circulating B cells for markers associated with B cell function revealed a significantly decreased expression of the B cell activation factor receptor (BAFF-R) in MS patients compared to controls. In healthy controls, BAFF-R expression was inversely associated with abundance of differentiated MBC but this was not observed in MS. Instead in MS patients, decreased BAFF-R expression correlated with increased production of proinflammatory TNF following B cell stimulation. Finally, we demonstrated that reactivation of Epstein Barr Virus (EBV) in MS patients was associated with several phenotypic changes amongst MBCs, particularly increased expression of HLA-DR molecules and markers of a T-bet+ differentiation pathway in IgM+ MBCs. Together, these data suggest that the B cell compartment is dysregulated in MS regarding aberrant MBC homeostasis, driven by reduced BAFF-R expression and EBV reactivation. This study adds further insights into the contribution of B cells to the pathological mechanisms of MS, as well as the complex role of BAFF/BAFF-R signalling in MS.

MRI Patterns Distinguish AQP4 Antibody Positive Neuromyelitis Optica Spectrum Disorder From Multiple Sclerosis.

Neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) are inflammatory diseases of the CNS. Overlap in the clinical and MRI features of NMOSD and MS means that distinguishing these conditions can be difficult. With the aim of evaluating the diagnostic utility of MRI features in distinguishing NMOSD from MS, we have conducted a cross-sectional analysis of imaging data and developed predictive models to distinguish the two conditions. NMOSD and MS MRI lesions were identified and defined through a literature search. Aquaporin-4 (AQP4) antibody positive NMOSD cases and age- and sex-matched MS cases were collected. MRI of orbits, brain and spine were reported by at least two blinded reviewers. MRI brain or spine was available for 166/168 (99%) of cases. Longitudinally extensive (OR = 203), "bright spotty" (OR = 93.8), whole (axial; OR = 57.8) or gadolinium (Gd) enhancing (OR = 28.6) spinal cord lesions, bilateral (OR = 31.3) or Gd-enhancing (OR = 15.4) optic nerve lesions, and nucleus tractus solitarius (OR = 19.2), periaqueductal (OR = 16.8) or hypothalamic (OR = 7.2) brain lesions were associated with NMOSD. Ovoid (OR = 0.029), Dawson's fingers (OR = 0.031), pyramidal corpus callosum (OR = 0.058), periventricular (OR = 0.136), temporal lobe (OR = 0.137) and T1 black holes (OR = 0.154) brain lesions were associated with MS. A score-based algorithm and a decision tree determined by machine learning accurately predicted more than 85% of both diagnoses using first available imaging alone. We have confirmed NMOSD and MS specific MRI features and combined these in predictive models that can accurately identify more than 85% of cases as either AQP4 seropositive NMOSD or MS.

Epitope-specific anti-prion antibodies upregulate apolipoprotein E and disrupt membrane cholesterol homeostasis.

The mechanisms of neuronal degeneration induced by the transformation of normal cellular prion protein (PrP(C)) into disease-associated PrP(Sc) are not fully understood. Previous reports have demonstrated that cross-linking cellular prion protein by anti-PrP(C) antibodies can promote neuronal apoptosis. In this report, we now show that treatment of neuronal cells with anti-prion antibodies leads to sequestration of free cholesterol in cell membranes, significant overexpression of apolipoprotein E, and to cytoplasmic phospholipase A2 activation as well as to production of prostaglandin. These results confirm the in vivo toxic effects and indicate that anti-prion antibody treatment of neurons lead to deleterious effects. Finally, great caution should be exerted when adopting antibody-based therapy for prion diseases.

Selective modulation of trans-endothelial migration of lymphocyte subsets in multiple sclerosis patients under fingolimod treatment.

Multiple sclerosis (MS) is an autoimmune disorder where auto-aggressive T cells target the central nervous system (CNS), causing demyelination. The trans-endothelial migration of leucocytes across the blood-brain barrier (BBB) is one of the earliest CNS events in MS pathogenesis. We examined the effect of the disease state and treatment with fingolimod on the transmigration of peripheral blood mononuclear cells (PBMCs) in an in vitro BBB model. Patients' leucocyte numbers, subsets and phenotypes were assessed by flow cytometry. As expected, fingolimod treatment induced a significant reduction in T cell and B cell numbers compared to untreated MS patients and healthy controls. Interestingly fingolimod led to a marked reduction of CD4+ and a significant increase in CD8+ cell numbers. In migrated cells, only CD3+ cell numbers were reduced in fingolimod-treated, compared to untreated patients; it had no effect on B cell or monocyte transmigration. T cells were then differentiated into naïve, effector and memory subsets based on their expression of CCR7. This showed that MS patients had increased numbers of effector memory CD4+ cells re-expressing CD45RA (TEMRA) and a decrease in central memory (CM) CD8+ cells. The former was corrected by fingolimod, while the latter was not. CM CD4+ and CD8+ cells migrated across BBB more efficiently in fingolimod-treated patients. We found that while fingolimod reduced the proportions of naïve CD19+ B cells, it significantly increased the proportions of these cells which migrated. When B cells were further stratified based on CD24, CD27 and CD38 expression, the only effect of fingolimod was an enhancement of CD24hiCD27+ B cell migration, compared to untreated MS patients. The migratory capacities of CD8hi Natural Killer (NK), CD8dim NK and NK-T cells were also reduced by fingolimod. While the disease-modifying effects of fingolimod are currently explained by its effect on reducing circulating auto-aggressive lymphocytes, our data suggests that fingolimod may also have a direct though differential effect on the trans-endothelial migration of circulating lymphocyte populations.

IgG3 + B cells are associated with the development of multiple sclerosis.

OBJECTIVES: Disease-modifying therapies (DMTs) targeting B cells are amongst the most effective for preventing multiple sclerosis (MS) progression. IgG3 antibodies and their uncharacterised B-cell clones are predicted to play a pathogenic role in MS. Identifying subsets of IgG3 + B cells involved in MS progression could improve diagnosis, could inform timely disease intervention and may lead to new DMTs that target B cells more specifically. METHODS: We designed a 31-parameter B-cell-focused mass cytometry panel to interrogate the role of peripheral blood IgG3 + B cells in MS progression of two different patient cohorts: one to investigate the B-cell subsets involved in conversion from clinically isolated syndrome (CIS) to MS; and another to compare MS patients with inactive or active stages of disease. Each independent cohort included a group of non-MS controls. RESULTS: Nine distinct CD20+IgD-IgG3 + B-cell subsets were identified. Significant changes in the proportion of CD21+CD24+CD27-CD38- and CD27+CD38hiCD71hi memory B-cell subsets correlated with changes in serum IgG3 levels and time to conversion from CIS to MS. The same CD38- double-negative B-cell subset was significantly elevated in MS patients with active forms of the disease. A third CD21+CD24+CD27+CD38- subset was elevated in patients with active MS, whilst narrowband UVB significantly reduced the proportion of this switched-memory B-cell subset. CONCLUSION: We have identified previously uncharacterised subsets of IgG3 + B cells and shown them to correlate with autoimmune attacks on the central nervous system (CNS). These results highlight the potential for therapies that specifically target IgG3 + B cells to impact MS progression.

Relapse Patterns in NMOSD: Evidence for Earlier Occurrence of Optic Neuritis and Possible Seasonal Variation.

Neuromyelitis optica spectrum disorders (NMOSD) and multiple sclerosis (MS) show overlap in their clinical features. We performed an analysis of relapses with the aim of determining differences between the two conditions. Cases of NMOSD and age- and sex-matched MS controls were collected from across Australia and New Zealand. Demographic and clinical information, including relapse histories, were recorded using a standard questionnaire. There were 75 cases of NMOSD and 101 MS controls. There were 328 relapses in the NMOSD cases and 375 in MS controls. Spinal cord and optic neuritis attacks were the most common relapses in both NMOSD and MS. Optic neuritis (p < 0.001) and area postrema relapses (P = 0.002) were more common in NMOSD and other brainstem attacks were more common in MS (p < 0.001). Prior to age 30 years, attacks of optic neuritis were more common in NMOSD than transverse myelitis. After 30 this pattern was reversed. Relapses in NMOSD were more likely to be treated with acute immunotherapies and were less likely to recover completely. Analysis by month of relapse in NMOSD showed a trend toward reduced risk of relapse in February to April compared to a peak in November to January (P = 0.065). Optic neuritis and transverse myelitis are the most common types of relapse in NMOSD and MS. Optic neuritis tends to occur more frequently in NMOSD prior to the age of 30, with transverse myelitis being more common thereafter. Relapses in NMOSD were more severe. A seasonal bias for relapses in spring-summer may exist in NMOSD.

The clinical profile of NMOSD in Australia and New Zealand.

Neuromyelitis optica spectrum disorders (NMOSD) are an inflammation of the central nervous system associated with autoantibodies to aquaporin-4. We have undertaken a clinic-based survey of NMOSD in the Australia and New Zealand populations with the aim of characterising the clinical features and establishing the value of recently revised diagnostic criteria. Cases of possible NMOSD and age and sex-matched controls with multiple sclerosis (MS) were referred from centres across Australia and New Zealand. Cases were classified as NMOSD if they met the 2015 IPND criteria and remained as suspected NMOSD if they did not. Clinical and paraclinical data were compared across the three groups. NMOSD was confirmed in 75 cases and 89 had suspected NMOSD. There were 101 controls with MS. Age at onset, relapse rates and EDSS scores were significantly higher in NMOSD than in MS. Lesions and symptoms referable to the optic nerve were more common in NMOSD whereas brainstem, cerebellar and cerebral lesions were more common in MS. Longitudinally extensive spinal cord lesions were seen in 48/71 (68%) of cases with NMOSD. Elevations of CSF, white cell count and protein were more common in NMOSD. We have confirmed a clinical pattern of NMOSD that has been seen in several geographical regions. We have demonstrated the clinical utility of the current diagnostic criteria. Distinct patterns of disease are evident in NMOSD and MS, but there remains a large number of patients with NMOSD-like features who do not meet the current diagnostic criteria for NMOSD and remain a diagnostic challenge.

Beta-PrP form of human prion protein stimulates production of monoclonal antibodies to epitope 91-110 that recognise native PrPSc.

Prion diseases are associated with accumulation of strain-dependent biochemically distinct, disease-related isoforms (PrP(Sc)) of host-encoded prion protein (PrP(C)). PrP(Sc) is characterised by increased beta-sheet content, detergent insolubility and protease resistance. Recombinant alpha-PrP adopts a PrP(C)-like conformation, while beta-PrP conformationally resembles PrP(Sc), to these we raised 81 monoclonal antibodies in Prnp(0/0) mice. The N-terminal residues 91-110 are highly immunogenic in beta-PrP-immunised mice and of (17/41) anti-beta-PrP antibodies that could be epitope-mapped, approximately 70%, recognised this segment. In contrast, only 3/40 anti-alpha-PrP antibodies could be mapped and none interacted with this region, instead recognising residues 131-150, 141-160 and 171-190. Native PrP(C) was recognised by both antibody groups, but only anti-beta-PrP antibodies directed to 91-110 residues recognised native PrP(Sc) with high affinity, where in addition, species heterogeneity was also evident. Within the six anti-beta-PrP antibodies studied, they all recognised PK-treated native human and mouse PrP(Sc), four failed to recognise PK-treated native bovine PrP(Sc), one of which also did not recognise native PK-treated ovine PrP(Sc), showing the epitope becomes exposed on unfolding and disaggregation. These results demonstrate strain-dependent variations in chain conformation and packing within the 91-110 region of PrP(Sc).

Fatal reversible cerebral vasoconstriction syndrome.

We report four fatal cases of fulminant reversible cerebral vasoconstriction syndrome, all initially diagnosed as primary central nervous system vasculitis and treated with corticosteroids. Although reversible cerebral vasoconstriction syndrome is usually self-limiting without permanent neurologic deficits, rarely it can be fatal and worse outcomes have been associated with corticosteroid treatment.

Exosomal microRNA signatures in multiple sclerosis reflect disease status.

Multiple Sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). There is currently no single definitive test for MS. Circulating exosomes represent promising candidate biomarkers for a host of human diseases. Exosomes contain RNA, DNA, and proteins, can cross the blood-brain barrier, and are secreted from almost all cell types including cells of the CNS. We hypothesized that serum exosomal miRNAs could present a useful blood-based assay for MS disease detection and monitoring. Exosome-associated microRNAs in serum samples from MS patients (n = 25) and matched healthy controls (n = 11) were profiled using small RNA next generation sequencing. We identified differentially expressed exosomal miRNAs in both relapsing-remitting MS (RRMS) (miR-15b-5p, miR-451a, miR-30b-5p, miR-342-3p) and progressive MS patient sera (miR-127-3p, miR-370-3p, miR-409-3p, miR-432-5p) in relation to controls. Critically, we identified a group of nine miRNAs (miR-15b-5p, miR-23a-3p, miR-223-3p, miR-374a-5p, miR-30b-5p, miR-433-3p, miR-485-3p, miR-342-3p, miR-432-5p) that distinguished relapsing-remitting from progressive disease. Eight out of nine miRNAs were validated in an independent group (n = 11) of progressive MS cases. This is the first demonstration that microRNAs associated with circulating exosomes are informative biomarkers not only for the diagnosis of MS, but in predicting disease subtype with a high degree of accuracy.