Emily K. Mathey

Neurofascin as a novel target for autoantibody-mediated axonal injury

Axonal injury is considered the major cause of disability in patients with multiple sclerosis (MS), but the underlying effector mechanisms are poorly understood. Starting with a proteomics-based approach, we identified neurofascin-specific autoantibodies in patients with MS. These autoantibodies recognize the native form of the extracellular domains of both neurofascin 186 (NF186), a neuronal protein concentrated in myelinated fibers at nodes of Ranvier, and NF155, the oligodendrocyte-specific isoform of neurofascin. Our in vitro studies with hippocampal slice cultures indicate that neurofascin antibodies inhibit axonal conduction in a complement-dependent manner. To evaluate whether circulating antineurofascin antibodies mediate a pathogenic effect in vivo, we cotransferred these antibodies with myelin oligodendrocyte glycoprotein–specific encephalitogenic T cells to mimic the inflammatory pathology of MS and breach the blood–brain barrier. In this animal model, antibodies to neurofascin selectively targeted nodes of Ranvier, resulting in deposition of complement, axonal injury, and disease exacerbation. Collectively, these results identify a novel mechanism of immune-mediated axonal injury that can contribute to axonal pathology in MS.

Contactin-2/TAG-1-directed autoimmunity is identified in multiple sclerosis patients and mediates gray matter pathology in animals

Gray matter pathology is increasingly recognized as an important feature of multiple sclerosis (MS), but the nature of the immune response that targets the gray matter is poorly understood. Starting with a proteomics approach, we identified contactin-2/transiently expressed axonal glycoprotein 1 (TAG-1) as a candidate autoantigen recognized by both autoantibodies and T helper (Th) 1/Th17 T cells in MS patients. Contactin-2 and its rat homologue, TAG-1, are expressed by various neuronal populations and sequestered in the juxtaparanodal domain of myelinated axons both at the axonal and myelin sides. The pathogenic significance of these autoimmune responses was then explored in experimental autoimmune encephalitis models in the rat. Adoptive transfer of TAG-1–specific T cells induced encephalitis characterized by a preferential inflammation of gray matter of the spinal cord and cortex. Cotransfer of TAG-1–specific T cells with a myelin oligodendrocyte glycoprotein-specific mAb generated focal perivascular demyelinating lesions in the cortex and extensive demyelination in spinal cord gray and white matter. This study identifies contactin-2 as an autoantigen targeted by T cells and autoantibodies in MS. Our findings suggest that a contactin-2–specific T-cell response contributes to the development of gray matter pathology.

Chronic inflammatory demyelinating polyradiculoneuropathy: from pathology to phenotype

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an inflammatory neuropathy, classically characterised by a slowly progressive onset and symmetrical, sensorimotor involvement. However, there are many phenotypic variants, suggesting that CIDP may not be a discrete disease entity but rather a spectrum of related conditions. While the abiding theory of CIDP pathogenesis is that cell-mediated and humoral mechanisms act together in an aberrant immune response to cause damage to peripheral nerves, the relative contributions of T cell and autoantibody responses remain largely undefined. In animal models of spontaneous inflammatory neuropathy, T cell responses to defined myelin antigens are responsible. In other human inflammatory neuropathies, there is evidence of antibody responses to Schwann cell, compact myelin or nodal antigens. In this review, the roles of the cellular and humoral immune systems in the pathogenesis of CIDP will be discussed. In time, it is anticipated that delineation of clinical phenotypes and the underlying disease mechanisms might help guide diagnostic and individualised treatment strategies for CIDP.

Antibodies to MOG have a demyelination phenotype and affect oligodendrocyte cytoskeleton

Objective: To examine the clinical features of pediatric CNS demyelination associated with positive myelin oligodendrocyte glycoprotein (MOG) antibodies and to examine the functional effects of MOG antibody on oligodendrocyte cytoskeleton. Methods: We measured MOG antibody using a fluorescence-activated cell sorting live cell-based assay in acute sera of 73 children with CNS demyelination (DEM) (median age 8 years, range 1.3–15.3) followed for a median of 4 years. We used MO3.13 cells to examine immunoglobulin (Ig) G effects on oligodendrocyte cytoskeleton using 3D deconvolution imaging. Results: MOG antibodies were found in 31/73 patients with DEM (42%) but in 0/24 controls. At first presentation, MOG antibody–positive patients were more likely to have bilateral than unilateral optic neuritis (ON) (9/10 vs 1/5, respectively, p = 0.03), less likely to have brainstem findings (2/31 vs 16/42, p = 0.005), more likely to have a raised erythrocyte sedimentation rate >20 mm/h (9/19 vs 3/21, p = 0.05), less likely to have intrathecal oligoclonal bands (0/16 vs 5/27, p = 0.18), and less likely to be homozygous or heterozygous for human leukocyte antigen DRB1*1501 (3/18 vs 7/22, p = 0.46). MOG antibody positivity varied according to clinical phenotype, with ON and relapsing ON most likely to be seropositive. Two relapsing MOG antibody–positive patients treated with mycophenolate mofetil remain in remission and have become MOG antibody seronegative. Oligodendrocytes incubated with purified IgG from MOG antibody–positive patients showed a striking loss of organization of the thin filaments and the microtubule cytoskeleton, as evidenced by F-actin and β-tubulin immunolabelings. Conclusions: MOG antibody may define a separate demyelination syndrome, which has therapeutic implications. MOG antibody has functional effects on oligodendrocyte cytoskeleton.

TNFα, IFNγ and IL-2 mRNA expression in CIDP sural nerve biopsies

Proinflammatory cytokines contribute to the regulation of the disease process in inflammatory neuropathies. Cellular localisation of cytokine expression in CIDP nerve biopsies should provide further insight into the pathogenic mechanisms of the disease and the individual cells involved. In this study in situ hybridisation was used to determine the exact localisation and identity of cells that express TNFα, IFNγ and IL-2 mRNA within the CIDP nerve. Paraffin embedded and frozen sural nerve biopsies from three acute phase CIDP patients were used for the study. Sections of these samples were probed with digoxigenin labelled oligoprobes for TNFα, IFNγ and IL-2. The results demonstrate localisation of cytokine expression to the inner rim of the perineurium, epineurial and endoneurial blood vessels and infiltrating inflammatory cells. In addition strong staining for TNFα mRNA was widespread in the endoneurium in areas consistent with/suggestive of Schwann cells. Expression of cytokines in the perineurium and endoneurial blood vessels may have pertinent implications with respect to the breakdown of the blood nerve barrier associated with CIDP. In the very least the potential for an immunomodulatory role may be ascribed to these cells.

Expression and distribution of transcription factor NF-κB and inhibitor IκB in the inflamed peripheral nervous system

Abstract The NF-κB family of transcription factors is critically involved in the immune response. The activity of these proteins is under strict control of an inhibitory molecule called IκB. The present study investigated the expression and distribution pattern of NF-κB and IκB in sural nerve biopsies obtained from patients with Guillain–Barre syndrome, chronic inflammatory demyelinating polyradiculoneuropathy, and various non-inflammatory neuropathies. In inflammatory demyelinating as well as non-inflammatory neuropathies, NF-κB was primarily expressed by macrophages, as determined by immunohistochemistry. IκB, however, could be localized to macrophages as well as T cells in inflammatory demyelinating neuropathies, whereas in non-inflammatory controls Schwann cells were found to be the primary cell type expressing this inhibitor. Quantitation of immunoreactivity revealed a statistically significant increase of NF-κB expression in inflammatory demyelinating cases compared to controls. Our results suggest an important function of the NF-κB pool in the genesis of inflammatory demyelination in the peripheral nervous system.

Cyclo-oxygenases and prostaglandins in acute inflammatory demyelination of the peripheral nerve

Objective: To investigate the expression of cyclo-oxygenases (COX), key enzymes in propagating inflammatory responses by converting arachidonic acid to prostaglandins, in inflammatory demyelinating disorders of the peripheral nervous system (PNS). Methods: Expression and distribution of COX messenger RNA (mRNA) and protein were studied in sural nerve biopsies, serum, and CSF samples from patients with Guillain–Barré syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), or, for comparison, with vasculitic neuropathy (VN), which is a inflammatory nondemyelinating disorder, and noninflammatory neuropathies (NIN) using RT-PCR, immunohistochemistry, and immunoblotting. To confirm functional COX-2 activity, the expression of prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) was evaluated by ELISA ex vivo and in vitro. Results: Whereas COX-1 expression was unaltered in all investigated groups, a significant upregulation of COX-2 mRNA was detected in sural nerves from patients with GBS, CIDP, or VN but not in control subjects with noninflammatory disorders. Macrophages were identified as its primary cellular source. Increased COX-2 protein levels were detectable in serum and CSF from all patients with GBS and, in smaller numbers only, in samples from patients with CIDP or VN but not from the NIN group studied. Moreover, increased levels of PGE2 and PGF2α were measurable in sera from patients with GBS, CIDP, or VN and in cell culture supernatants from in vitro stimulated macrophages, indicative of COX-2 activity. Conclusions: Cyclo-oxygenase-2, expressed by macrophages, may generate prostaglandins during acute inflammatory demyelination of the peripheral nerve.

Antibodies to neurofascin exacerbate adoptive transfer experimental autoimmune neuritis

Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy are autoimmune disorders of the peripheral nervous system in which autoantibodies are implicated in the disease pathogenesis. Recent work has focused on the nodal regions of the myelinated axon as potential autoantibody targets. Here we screened patient sera for autoantibodies to neurofascin and assessed the pathophysiological relevance of anti-neurofascin antibodies in vivo. Levels of anti-neurofascin antibodies were higher in sera from patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy when compared with those of controls. Anti-neurofascin antibodies exacerbated and prolonged adoptive transfer experimental autoimmune neuritis and caused conduction defects when injected intraneurally.

An update on Schwann cell biology — Immunomodulation, neural regulation and other surprises

Schwann cells are primarily discussed in the context of their ability to form myelin. However there are many subtypes of these neural crest derived cells including satellite cells of the dorsal root ganglia and autonomic ganglia, the perisynaptic Schwann cells of the neuromuscular junction and the non-myelin forming Schwann cells which ensheathe the unmyelinated fibres of the peripheral nervous system which are about 80% of peripheral nerves. This review discusses the many functions of these Schwann cell subsets including their seminal role in axonal ensheathment, perineuronal organisation, maintenance of normal neural function, synapse formation, response to damage and repair and an increasingly recognised active role in pain syndromes.

Autoantibody responses to nodal and paranodal antigens in chronic inflammatory neuropathies

Autoantibodies to nodal/paranodal proteins have been reported in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). To determine the frequency of anti-paranodal antibodies in our cohort of CIDP patients and to validate the presence anti-nodal antibodies in MMN, sera were screened for IgG against human neurofascin 155, contactin-1, neurofascin 186 and gliomedin using ELISA. In CIDP patients, 7% were anti-NF155 IgG4 positive and 7% were anti-CNTN1 IgG4 positive. Positive results were confirmed using cell based assays and indirect immunofluorescence on teased nerve fibres. We did not detect IgG autoantibodies against these nodal/paranodal antigens in MMN patients.