Neurofascin IgG4 antibodies in CIDP associate with disabling tremor and poor response to IVIg

Intravenous immunoglobulin: pharmacological properties and use in polyneuropathies

INTRODUCTION

Intravenous immunoglobulin (IVIg) is increasingly used for the treatment of autoimmune and systemic inflammatory diseases with both licensed and off-label indications. The mechanism of action is complex and not fully understood, involving the neutralization of pathological antibodies, Fc receptor blockade, complement inhibition, immunoregulation of dendritic cells, B cells and T cells and the modulation of apoptosis. Areas covered: First, this review describes the pharmacological properties of IVIg, including the composition, mechanism of action, and adverse events. The second part gives an overview of some of the immune-mediated polyneuropathies, with special focus on the pathomechanism and clinical trials assessing the efficacy of IVIg. A literature search on PubMed was performed using the terms IVIg, IVIg preparations, side effects, mechanism of action, clinical trials, GBS, CIDP. Expert opinion: Challenges associated with IVIg therapy and the treatment possibilities for immune-mediated polyneuropathies are discussed. The availability of IVIg is limited, the expenses are high, and, in several diseases, a chronic therapy is necessary to maintain the immunomodulatory effect. The better understanding of the mechanism of action of IVIg could open the possibility of the development of disease-specific, targeted immune therapies.

Auto-antibodies to contactin-associated protein 1 (Caspr) in two patients with painful inflammatory neuropathy

Auto-antibodies against the paranodal proteins neurofascin-155 and contactin-1 have recently been described in patients with chronic inflammatory demyelinating polyradiculoneuropathy and are associated with a distinct clinical phenotype and response to treatment. Contactin-associated protein 1 (Caspr, encoded by CNTNAP1) is a paranodal protein that is attached to neurofascin-155 and contactin-1 (CNTN1) but has not yet been identified as a sole antigen in patients with inflammatory neuropathies. In the present study, we screened a cohort of 35 patients with chronic inflammatory demyelinating polyradiculoneuropathy (age range 20-80, 10 female, 25 male) and 22 patients with Guillain-Barré syndrome (age range 17-86, eight female, 14 male) for autoantibodies against paranodal antigens. We identified two patients, one with chronic inflammatory demyelinating polyradiculoneuropathy and one with Guillain-Barré syndrome, with autoantibodies against Caspr by binding assays using Caspr transfected human embryonic kidney cells and murine teased fibres. IgG3 was the predominant autoantibody subclass in the patient with Guillain-Barré syndrome, IgG4 was predominant in the patient with chronic inflammatory demyelinating polyradiculoneuropathy. Accordingly, complement deposition after binding to HEK293 cells was detectable in the patient with IgG3 autoantibodies only, not in the patient with IgG4. Severe disruption of the paranodal and nodal architecture was detectable in teased fibres of the sural nerve biopsy and in dermal myelinated fibres, supporting the notion of the paranodes being the site of pathology. Deposition of IgG at the paranodes was detected in teased fibre preparations of the sural nerve, further supporting the pathogenicity of anti-Caspr autoantibodies. Pain was one of the predominant findings in both patients, possibly reflected by binding of patients' IgG to TRPV1 immunoreactive dorsal root ganglia neurons. Our results demonstrate that the paranodal protein Caspr constitutes a new antigen that leads to autoantibody generation as part of the novel entity of neuropathies associated with autoantibodies against paranodal proteins.

Paranodal and other autoantibodies in chronic inflammatory neuropathies

PURPOSE OF REVIEW

Autoimmune disorders of the peripheral nerves are diverse and heterogeneous. T cells, macrophages, and autoantibodies have been implicated in their pathogenesis. Autoantibodies to peripheral nerve molecules seem to play a role not only in the pathogenesis but provide diagnostic, prognostic, and therapeutic help. We review the state of the art and most relevant recent findings regarding autoantibodies in chronic inflammatory neuropathies, focusing on their clinical utility.

RECENT FINDINGS

Research on autoantibodies in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) has received a recent boost with the description of antibodies against proteins of the node of Ranvier. Antibodies of the IgG4 isotype targeting the paranodal proteins contactin-1 (CNTN1) and neurofascin-155 (NF155) define specific CIDP subtypes and have diagnostic and prognostic implications. In multifocal motor neuropathy, anti-GM1 production is restricted to very few B-cell clones that could be the target of therapies aimed to remove or inactivate them. Moreover, novel ELISA and glycoarray techniques combining GM1 and galactocerebroside gangliosides improved the sensitivity of autoantibody detection. Detailed clinical and paraclinical features, including autoantibody reactivity patters, of autoimmune syndromes affecting simultaneously the central and peripheral nervous systems, are also described.

SUMMARY

The heterogeneity of chronic inflammatory neuropathies is being unraveled with the description of specific autoantibodies and their association with small disease subtypes. The recently described paranodal autoantibodies anti-CNTN1 and NF155 have direct clinical value and seem to determine response to treatment. Further studies are needed to fully understand the primary contribution of the antibodies to the pathophysiology of the immune neuropathies.

Improving the management of chronic inflammatory demyelinating polyradiculoneuropathy

This article considers several issues of current interest relating to the management of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), including diagnostic pitfalls, differences between CIDP patients with and without concurrent diabetes mellitus and how to best measure treatment response in daily practice. Despite the availability of diagnostic criteria, many patients diagnosed with CIDP do not meet these criteria; reasons for misdiagnosis are discussed. There are no definitive predictors of treatment response in CIDP; however, certain clinical and electrophysiological characteristics may be helpful. Patients with CIDP and concurrent diabetes present an additional diagnostic challenge; the differences between these groups, including possible differences in response predictors are discussed. Finally, the most appropriate outcome measures for use in daily practice are considered.

Contactin-1 IgG4 antibodies cause paranode dismantling and conduction defects

Paranodal axoglial junctions formed by the association of contactin-1, contactin-associated protein 1, and neurofascin-155, play important functions in nerve impulse propagation along myelinated axons. Autoantibodies to contactin-1 and neurofascin-155 define chronic inflammatory demyelinating polyradiculoneuropathy subsets of patients with specific clinical features. These autoantibodies are mostly of the IgG4 isotype, but their pathogenicity has not been proven. Here, we investigated the mechanisms how IgG subclasses to contactin-1 affect conduction. We show that purified anti-contactin-1 IgG1 and IgG4 bind to paranodes. To determine whether these isotypes can pass the paranodal barrier, we incubated isolated sciatic nerves with the purified antibody or performed intraneural injections. We found that IgG4 diffused into the paranodal regions in vitro or after intraneural injections. IgG4 infiltration was slow and progressive. In 24 h, IgG4 accessed the paranode borders near the nodal lumen, and completely fill the paranodal segments by 3 days. By contrast, control IgG, anti-contactin-1 IgG1, or even anti-contactin-associated-protein-2 IgG4 did not pass the paranodal barrier. To determine whether chronic exposure to these antibodies is pathogenic, we passively transferred anti-contactin-1 IgG1 and IgG4 into Lewis rats immunized with P2 peptide. IgG4 to contactin-1, but not IgG1, induced progressive clinical deteriorations combined with gait ataxia. No demyelination, axonal degeneration, or immune infiltration were observed. Instead, these animals presented a selective loss of the paranodal specialization in motor neurons characterized by the disappearance of the contactin-associated protein 1/contactin-1/neurofascin-155 complex at paranodes. Paranode destruction did not affect nodal specialization, but resulted in a moderate node lengthening. The sensory nerves and dorsal root ganglion were not affected in these animals. Electrophysiological examination further supported these results and revealed strong nerve activity loss affecting predominantly small diameter or slow conducting motor axons. These deficits partly matched with those found in patients: proximal motor involvement, gait ataxia, and a demyelinating neuropathy that showed early axonal features. The animal model thus seemed to replicate the early deteriorations in these patients and pointed out that paranodal loss in mature fibres results in conduction defects, but not conduction slowing. Our findings indicate that IgG4 directed against contactin-1 are pathogenic and are reliable biomarkers of a specific subset of chronic inflammatory demyelinating polyneuropathy patients. These antibodies appear to loosen the paranodal barrier, thereby favouring antibody progression and causing paranodal collapse.

Multifocal Motor Neuropathy Presenting as Pseudodystonia

Multifocal motor neuropathy (MMN) is an immune-mediated neuropathy. Wasting and weakness typically dominate the clinical presentation. We describe four cases presenting with prominent cramping resembling a primary movement disorder. All cases had features of focal motor conduction block on neurophysiological studies. The involuntary movements resolved in all four patients following treatment with intravenous immunoglobulin. The presented cases highlight an unusual presentation of MMN and emphasize that peripheral nerve pathology can present with movement disorders mimicking central nervous system disease. Furthermore, the movement disorder appears particularly sensitive to standard therapy.

Neurofascin-155 IgG4 in chronic inflammatory demyelinating polyneuropathy

OBJECTIVE

We report the clinical and serologic features of Japanese patients with chronic inflammatory demyelinating polyneuropathy (CIDP) displaying anti-neurofascin-155 (NF155) immunoglobulin G4 (IgG4) antibodies.

METHODS

In sera from 533 patients with CIDP, anti-NF155 IgG4 antibodies were detected by ELISA. Binding of IgG antibodies to central and peripheral nerves was tested.

RESULTS

Anti-NF155 IgG4 antibodies were identified in 38 patients (7%) with CIDP, but not in disease controls or normal participants. These patients were younger at onset as compared to 100 anti-NF155-negative patients with CIDP. Twenty-eight patients (74%) presented with sensory ataxia, 16 (42%) showed tremor, 5 (13%) presented with cerebellar ataxia associated with nystagmus, 3 (8%) had demyelinating lesions in the CNS, and 20 of 25 (80%) had poor response to IV immunoglobulin. The clinical features of the antibody-positive patients were statistically more frequent as compared to negative patients with CIDP (n = 100). Anti-NF155 IgG antibodies targeted similarly central and peripheral paranodes.

CONCLUSION

Anti-NF155 IgG4 antibodies were associated with a subgroup of patients with CIDP showing a younger age at onset, ataxia, tremor, CNS demyelination, and a poor response to IV immunoglobulin. The autoantibodies may serve as a biomarker to improve patients' diagnosis and guide treatments.

Combined central and peripheral demyelination: Clinical features, diagnostic findings, and treatment

Combined central and peripheral demyelination (CCPD) is rare, and current knowledge is based on case reports and small case series. The aim of our study was to describe the clinical features, diagnostic results, treatment and outcomes in a large cohort of patients with CCPD. Thirty-one patients entered this retrospective, observational, two-center study. In 20 patients (65%) CCPD presented, after an infection, as myeloradiculoneuropathy, encephalopathy, cranial neuropathy, length-dependent peripheral neuropathy, or pseudo-Guillain-Barré syndrome. Demyelinating features of peripheral nerve damage fulfilling European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) electrodiagnostic criteria for CIDP were found in 23 patients (74%), and spatial dissemination of demyelinating lesions on brain MRI fulfilling the 2010 McDonald criteria for multiple sclerosis (MS) in 11 (46%). Two thirds of the patients had a relapsing or progressive disease course, usually related to the appearance of new spinal cord lesions or worsening of the peripheral neuropathy, and showed unsatisfactory responses to high-dose corticosteroids and intravenous immunoglobulins. The clinical presentation of CCPD was severe in 22 patients (71%), who were left significantly disabled. Our data suggest that CCPD has heterogeneous features and shows frequent post-infectious onset, primary peripheral nervous system or central nervous system involvement, a monophasic or chronic disease course, inadequate response to treatments, and a generally poor outcome. We therefore conclude that the current diagnostic criteria for MS and CIDP may not fully encompass the spectrum of possible manifestations of CCPD, whose pathogenesis remains largely unknown.

Novel immunotherapeutic strategies in chronic inflammatory demyelinating polyneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a chronic immune-mediated neuropathy: it is clinically heterogeneous (relapsing-remitting form, chronic progressive form, monophasic form or CIDP having a Guillain-Barré syndrome-like onset), but potentially treatable. Although its pathophysiology remains largely unknown, CIDP is considered an immune-mediated neuropathy. Therefore, many immunotherapies have been proposed in this peripheral nervous system disorder, the most known efficient treatments being intravenous immunoglobulin, corticosteroids and plasma exchange. However, these therapies remain unsatisfactory for many patients, so numerous other immunotherapeutic strategies have been evaluated, based on their immunosuppressant or immunomodulatory potency. We have performed a large review of the literature about treatment in CIDP, with a special emphasis on novel and alternative immunotherapeutic strategies.

Immunotherapy in Peripheral Neuropathies

Immunotherapy has been investigated in a small subset of peripheral neuropathies, including an acute one, Guillain-Barré syndrome, and 3 chronic forms: chronic inflammatory demyelinating polyradiculoneuropathy, multifocal motor neuropathy, and neuropathy associated with IgM anti-myelin-associated glycoprotein. Several experimental studies and clinical data are strongly suggestive of an immune-mediated pathogenesis. Either cell-mediated mechanisms or antibody responses to Schwann cell, compact myelin, or nodal antigens are considered to act together in an aberrant immune response to cause damage to peripheral nerves. Immunomodulatory treatments used in these neuropathies aim to act at various steps of this pathogenic process. However, there are many phenotypic variants and, consequently, there is a significant difference in the response to immunotherapy between these neuropathies, as well as a need to improve our knowledge and long-term management of chronic forms.

The search for the target antigens of multiple sclerosis, part 2: CD8+ T cells, B cells, and antibodies in the focus of reverse-translational research

Interest in CD8+ T cells and B cells was initially inspired by observations in multiple sclerosis rather than in animal models: CD8+ T cells predominate in multiple sclerosis lesions, oligoclonal immunoglobulin bands in CSF have long been recognised as diagnostic and prognostic markers, and anti-B-cell therapies showed considerable efficacy in multiple sclerosis. Taking a reverse-translational approach, findings from human T-cell receptor (TCR) and B-cell receptor (BCR) repertoire studies provided strong evidence for antigen-driven clonal expansion in the brain and CSF. New methods allow the reconstruction of human TCRs and antibodies from tissue-infiltrating immune cells, which can be used for the unbiased screening of antigen libraries. Myelin oligodendrocyte glycoprotein (MOG) has received renewed attention as an antibody target in childhood multiple sclerosis and in a small subgroup of adult patients with multiple sclerosis. Furthermore, there is growing evidence that a separate condition in adults exists, tentatively called MOG-antibody-associated encephalomyelitis, which has clinical features that overlap with neuromyelitis optica spectrum disorder and multiple sclerosis. Although CD8+ T cells and B cells are thought to have a pathogenic role in some subgroups of patients, their target antigens have yet to be identified.

Characterization of IgG4 anti-neurofascin 155 antibody-positive polyneuropathy

Objective

To investigate anti-neurofascin 155 (NF155) antibody-positive chronic inflammatory demyelinating polyneuropathy (CIDP).

Methods

Sera from 50 consecutive CIDP patients diagnosed in our clinic, 32 patients with multiple sclerosis, 40 patients with other neuropathies including 26 with Guillain–Barré syndrome (GBS)/Fisher syndrome, and 30 healthy controls were measured for anti-NF antibodies by flow cytometry using HEK293 cell lines stably expressing human NF155 or NF186. Four additional CIDP patients with anti-NF155 antibodies referred from other clinics were enrolled for clinical characterization.

Results

The positivity rate for anti-NF155 antibodies in CIDP patients was 18% (9/50), who all showed a predominance of IgG4 subclass. No other subjects were positive, except one GBS patient harboring IgG1 anti-NF155 antibodies. No anti-NF155 antibody carriers had anti-NF186 antibodies. Anti-NF155 antibody-positive CIDP patients had a significantly younger onset age, higher frequency of drop foot, gait disturbance, tremor and distal acquired demyelinating symmetric phenotype, greater cervical root diameter on magnetic resonance imaging neurography, higher cerebrospinal fluid protein levels, and longer distal and F-wave latencies than anti-NF155 antibody-negative patients. Marked symmetric hypertrophy of cervical and lumbosacral roots/plexuses was present in all anti-NF155 antibody-positive CIDP patients examined by neurography. Biopsied sural nerves from two patients with anti-NF155 antibodies demonstrated subperineurial edema and occasional paranodal demyelination, but no vasculitis, inflammatory cell infiltrates, or onion bulbs. Among anti-NF155 antibody-positive patients, treatment responders more frequently had daily oral corticosteroids and/or immunosuppressants in addition to intravenous immunoglobulins than nonresponders did.

Interpretation

Anti-NF155 antibodies occur in a subset of CIDP patients with distal-dominant involvement and symmetric nerve hypertrophy.

Rituximab in treatment-resistant CIDP with antibodies against paranodal proteins

Objective:

To describe the response to rituximab in patients with treatment-resistant chronic inflammatory demyelinating polyneuropathy (CIDP) with antibodies against paranodal proteins and correlate the response with autoantibody titers.

Methods:

Patients with CIDP and IgG4 anti–contactin-1 (CNTN1) or anti–neurofascin-155 (NF155) antibodies who were resistant to IV immunoglobulin and corticosteroids were treated with rituximab and followed prospectively. Immunocytochemistry was used to detect anti-CNTN1 and anti-NF155 antibodies and ELISA with human recombinant CNTN1 and NF155 proteins was used to determine antibody titers.

Results:

Two patients had a marked improvement; another patient improved slightly after 10 years of stable, severe disease; and the fourth patient had an ischemic stroke unrelated to treatment and was lost to follow-up. Autoantibodies decreased in all patients after rituximab treatment.

Conclusions:

Rituximab treatment is an option for patients with CIDP with IgG4 anti-CNTN1/NF155 antibodies who are resistant to conventional therapies.

Classification of evidence:

This study provides Class IV evidence that rituximab is effective for patients with treatment-resistant CIDP with IgG4 anti-CNTN1 or anti-NF155 antibodies.

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.

Plasma exchange for chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an uncommon progressive or relapsing paralysing disease caused by inflammation of the peripheral nerves. If the hypothesis that it is due to autoimmunity is correct, removal of autoantibodies in the blood by plasma exchange should be beneficial.

OBJECTIVES

To assess the effects of plasma exchange for treating CIDP.

SEARCH METHODS

On 30 June 2015, we searched the Cochrane Neuromuscular Disease Group Specialized Register, the Cochrane Central Register for Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL Plus, and LILACS. We also scrutinised the bibliographies of the trials, contacted the trial authors and other disease experts, and searched trials registries for ongoing studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs in participants of any age comparing plasma exchange with sham treatment or no treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected the trials, extracted the data, and assessed risk of bias. Where possible the review authors combined data according to the methods of the Cochrane Neuromuscular Disease Review Group.

PRIMARY OUTCOME MEASURE

one cross-over trial including 18 participants showed after four weeks, 2 (95% confidence interval (CI) 0.8 to 3.0) points more improvement on an 11-point disability scale with plasma exchange (10 exchanges over four weeks) than with sham exchange. Rapid deterioration after plasma exchange occurred in eight of 12 who had improved.

SECONDARY OUTCOME MEASURES

when we combined the results of this cross-over trial and a trial with 29 participants treated in a parallel-group design, there were 31 points (95% CI 16 to 45) more improvement on an impairment scale (maximum score 280) after plasma exchange (six exchanges over three weeks) than after sham exchange. There were significant improvements in both trials in an electrophysiological measure, the proximally evoked compound muscle action potential, after three or four weeks. Nonrandomised evidence indicates that plasma exchange induces adverse events in 3% to 17% of procedures. These events are sometimes serious. Both trials had a low risk of bias. A trial that showed no significant difference in the benefit between plasma exchange and intravenous immunoglobulin is included in the Cochrane review of intravenous immunoglobulin for this condition.

AUTHORS' CONCLUSIONS

Moderate- to high-quality evidence from two small trials shows that plasma exchange provides significant short-term improvement in disability, clinical impairment, and motor nerve conduction velocity in CIDP but rapid deterioration may occur afterwards. Adverse events related to difficulty with venous access, use of citrate, and haemodynamic changes are not uncommon. We need more research to identify agents that will prolong the beneficial action of plasma exchange.

Autoantibodies against vinculin in patients with chronic inflammatory demyelinating polyneuropathy

To identify the target molecules of chronic inflammatory demyelinating polyneuropathy (CIDP), we used proteomic-based approach in the extracted proteins from porcine cauda equina. Two of 31 CIDP patients had markedly elevated serum autoantibodies against vinculin, a cell adhesion protein. Both of the patients with anti-vinculin antibodies had similar clinical manifestation, which are compatible with those of "typical" CIDP. Immunocytochemistry showed that vinculin was stained at the myelin sheath of the sciatic nerves by serum samples. Our results suggest that vinculin is a possible immunological target molecule in a subpopulation of typical CIDP patients.

Contactin-1 and Neurofascin-155/-186 Are Not Targets of Auto-Antibodies in Multifocal Motor Neuropathy

Multifocal motor neuropathy is an immune mediated disease presenting with multifocal muscle weakness and conduction block. IgM auto-antibodies against the ganglioside GM1 are detectable in about 50% of the patients. Auto-antibodies against the paranodal proteins contactin-1 and neurofascin-155 and the nodal protein neurofascin-186 have been detected in subgroups of patients with chronic inflammatory demyelinating polyneuropathy. Recently, auto-antibodies against neurofascin-186 and gliomedin were described in more than 60% of patients with multifocal motor neuropathy. In the current study, we aimed to validate this finding, using a combination of different assays for auto-antibody detection. In addition we intended to detect further auto-antibodies against paranodal proteins, specifically contactin-1 and neurofascin-155 in multifocal motor neuropathy patients’ sera. We analyzed sera of 33 patients with well-characterized multifocal motor neuropathy for IgM or IgG anti-contactin-1, anti-neurofascin-155 or -186 antibodies using enzyme-linked immunosorbent assay, binding assays with transfected human embryonic kidney 293 cells and murine teased fibers. We did not detect any IgM or IgG auto-antibodies against contactin-1, neurofascin-155 or -186 in any of our multifocal motor neuropathy patients. We conclude that auto-antibodies against contactin-1, neurofascin-155 and -186 do not play a relevant role in the pathogenesis in this cohort with multifocal motor neuropathy.

Inhibitory axons are targeted in hippocampal cell culture by anti-Caspr2 autoantibodies associated with limbic encephalitis

Contactin-associated protein-like 2 (Caspr2), also known as CNTNAP2, is a cell adhesion molecule that clusters voltage-gated potassium channels (Kv1.1/1.2) at the juxtaparanodes of myelinated axons and may regulate axonal excitability. As a component of the Kv1 complex, Caspr2 has been identified as a target in neuromyotonia and Morvan syndrome, but also in some cases of autoimmune limbic encephalitis (LE). How anti-Caspr2 autoimmunity is linked with the central neurological symptoms is still elusive. In the present study, using anti-Caspr2 antibodies from seven patients affected by pure LE, we determined that IgGs in the cerebrospinal fluid of four out seven patients were selectively directed against the N-terminal Discoïdin and LamininG1 modules of Caspr2. Using live immunolabeling of cultured hippocampal neurons, we determined that serum IgGs in all patients strongly targeted inhibitory interneurons. Caspr2 was highly detected on GAD65-positive axons that are surrounding the cell bodies and at the VGAT-positive inhibitory presynaptic contacts. Functional assays indicated that LE autoantibodies may induce alteration of Gephyrin clusters at inhibitory synaptic contacts. Next, we generated a Caspr2-Fc chimera to reveal Caspr2 receptors on hippocampal neurons localized at the somato-dendritic compartment and post-synapse. Caspr2-Fc binding was strongly increased on TAG-1-transfected neurons and conversely, Caspr2-Fc did not bind hippocampal neurons from TAG-1-deficient mice. Our data indicate that Caspr2 may participate as a cell recognition molecule in the dynamics of inhibitory networks. This study provides new insight into the potential pathogenic effect of anti-Caspr2 autoantibodies in central hyperexcitability that may be related with perturbation of inhibitory interneuron activity.

Destruction of paranodal architecture in inflammatory neuropathy with anti-contactin-1 autoantibodies

OBJECTIVE

Autoantibodies against paranodal proteins have been described in patients with inflammatory neuropathies, but their association with pathology of nodes of Ranvier is unclear. We describe the clinical phenotype and histopathological changes of paranodal architecture of patients with autoantibodies against contactin-1, identified from a cohort with chronic inflammatory demyelinating polyradiculoneuropathy (n=53) and Guillain-Barré syndrome (n=21).

METHODS

We used ELISA to detect autoantibodies against contactin-1. Specificity of the autoantibodies was confirmed by immunoblot assay, binding to contactin-1-transfected human embryonic kidney cells, binding to paranodes of murine teased fibres and preabsorption experiments. Paranodal pathology was investigated by immunofluorescence labelling of dermal myelinated fibres.

RESULTS

High reactivity to contactin-1 by ELISA was found in four patients with chronic inflammatory demyelinating polyradiculoneuropathy and in none of the patients with Guillain-Barré syndrome, which was confirmed by cell binding assays in all four patients. The four patients presented with a typical clinical picture, namely acute onset of disease and severe motor symptoms, with three patients manifesting action tremor. Immunofluorescence-labelling of paranodal proteins of dermal myelinated fibres revealed disruption of paranodal architecture. Semithin sections showed axonal damage but no classical signs of demyelination.

INTERPRETATION

We conclude that anti-contactin-1-related neuropathy constitutes a presumably autoantibody-mediated form of inflammatory neuropathy with distinct clinical symptoms and disruption of paranodal architecture as a pathological correlate. Anti-contactin-1-associated neuropathy does not meet morphological criteria of demyelinating neuropathy and therefore, might rather be termed a 'paranodopathy' rather than a subtype of demyelinating inflammatory neuropathy.

[A case of combined central and peripheral demyelination]

A 22-year-old man had had difficulty running fast since about he was 10 years old. In June 2011, he was referred to us because of worsened unsteady gait. A neurological examination revealed mild ataxic speech, weakness of the four limbs, with spasticity, and pes cavus. Magnetic resonance T2-weighted images showed multiple high-intensity lesions in the bilateral periventricular white matter, brainstem, and thoracic spinal cord. Peripheral nerve conduction studies revealed marked motor conduction velocities were markedly reduced and sensory nerve velocities were not evoked in the upper and lower limbs. A sural nerve biopsy showed highly active demyelinating lesions. The patient was treated with high-dose steroid therapy (intravenous methylprednisolone, 1,000 mg/day × 3 days) followed by self-injection of interferon β. With these treatments, his symptoms gradually improved. In this case, we could not detect the causative factors, and all autoantibodies tested, except for the anti-neurofascin antibody, were negative. The anti-neurofascin antibody might induce demyelination in the central and peripheral nervous systems. However, in the literature, the evidence of an association between this antibody and these clinical characteristics is not conclusive. We need more studies on the pathogenesis of combined central and peripheral demyelination to establish more effective therapies.

Diagnostic Utility of Auto Antibodies in Inflammatory Nerve Disorders

A wide range of autoantibodies have been described in immune-mediated nerve disorders that target glycans borne by glycolipids and glycoproteins enriched in the peripheral nerves. Their use as diagnostic biomarkers is very widespread, despite some limitations on sensitivity and specificity, and the lack of standardized assays and access to quality assurance schemes. Although many methods have been applied to measurement, ELISA, in the form of commercial kits or in-house assays, still remains the most widely available and convenient assay methodology.Some antibodies have a particularly robust and widely appreciated clinical significance. Thus, the anti-MAG IgM antibodies that are found in IgM paraprotein related neuropathies define a relatively uniform clinical and prognostic phenotype. IgG antibodies against gangliosides GM1 and GD1a are strongly associated with motor axonal variants of Guillain-Barré syndrome, and anti-GQ1b with Miller Fisher syndrome. In other chronic neuropathies, antibodies against disialylated gangliosides including GD1b and GD3 are detected in ataxic neuropathies, usually associated with an IgM paraprotein, and antibodies against GM1 and the complex GM1:GalC are frequently found in multifocal motor neuropathy. Unfortunately, autoantibodies strongly associated with the diagnosis of chronic inflammatory demyelinating polyneuropathies and with demyelinating forms of GBS are still lacking.Identification of autoantibodies that map onto a specific clinical phenotype not only allows for improved classification, but also provides better understanding of the pathophysiology of inflammatory neuropathies and the potential for therapeutic interventions.

The expanding field of IgG4-mediated neurological autoimmune disorders

At least 13 different disease entities affecting the central nervous system, peripheral nervous system and connective tissue of the skin or kidneys are associated with immunoglobulin G4 (IgG4) immune reactivity. IgG4 has always been considered a benign, non-inflammatory subclass of IgG, in contrast to the well-known complement-activating pro-inflammatory IgG1 subclass. A comprehensive review of these IgG4 autoimmune disorders reveals striking similarities in epitope binding and human leukocyte antigen (HLA) associations. Mechanical interference of extracellular ligand-receptor interactions by the associated IgG4 antibodies seems to be the common/converging disease mechanism in these disorders.

Tremor in Charcot-Marie-Tooth disease: No evidence of cerebellar dysfunction

OBJECTIVES

Tremor in Charcot-Marie-Tooth disease (CMT) can be disabling. Cerebellar abnormalities are thought to underpin neuropathic tremor. Here, we aim to clarify the potential role of the cerebellum in CMT tremor.

METHODS

We assessed prevalence of tremor by questionnaire in 84 patients with CMT. Of those, 23 patients with CMT with and without arm tremor and healthy controls underwent a clinical assessment, classical eyeblink conditioning, electro-oculography, visuomotor adaptation test, tremor recording with surface EMG and accelerometry, and retrospective correlation with nerve conduction studies to investigate the possible mechanisms of tremor generation.

RESULTS

The prevalence study revealed tremor in 21% of patients and in 42% of those it caused impairment of function. Tremor recordings revealed a mild-to-moderate amplitude tremor with a weight load-invariant 7.7 Hz frequency component. Performance on classical eyeblink conditioning, visuomotor adaptation and electro-oculography were no different between tremulous and non-tremulous patients and healthy controls.

CONCLUSIONS

These results argue against a prominent role for an abnormal cerebellum in tremor generation in the patients studied with CMT. Rather, our results suggest an enhancement of the central neurogenic component of physiological tremor as a possible mechanism for tremor in the patients studied.

SIGNIFICANCE

This study is the first to propose differing pathogenic mechanisms for subtypes of neuropathic tremor.

Glycans in the immune system and The Altered Glycan Theory of Autoimmunity: a critical review

Herein we will review the role of glycans in the immune system. Specific topics covered include: the glycosylation sites of IgE, IgM, IgD, IgE, IgA, and IgG; how glycans can encode "self" identity by functioning as either danger associated molecular patterns (DAMPs) or self-associated molecular patterns (SAMPs); the role of glycans as markers of protein integrity and age; how the glycocalyx can dictate the migration pattern of immune cells; and how the combination of Fc N-glycans and Ig isotype dictate the effector function of immunoglobulins. We speculate that the latter may be responsible for the well-documented association between alterations of the serum glycome and autoimmunity. Due to technological limitations, the extent of these autoimmune-associated glycan alterations and their role in disease pathophysiology has not been fully elucidated. Thus, we also review the current technologies available for glycan analysis, placing an emphasis on Multiple Reaction Monitoring (MRM), a rapid high-throughput technology that has great potential for glycan biomarker research. Finally, we put forth The Altered Glycan Theory of Autoimmunity, which states that each autoimmune disease will have a unique glycan signature characterized by the site-specific relative abundances of individual glycan structures on immune cells and extracellular proteins, especially the site-specific glycosylation patterns of the different immunoglobulin(Ig) classes and subclasses.

Pathophysiology and biomarkers in chronic inflammatory demyelinating polyradiculoneuropathies

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired dysimmune disorder characterized by strong heterogeneity in terms of clinical manifestations, prognostic and response to treatment. To date, its pathophysiology and potential target antigens are not totally identified despite substantial progress in the understanding of the involved molecular mechanisms. Recent researches in the field have underlined the importance of cell-mediated immunity (lymphocytesT CD4+, CD8+ and macrophages), the breakdown of blood-nerve barrier, a failure of T-cell regulation, and the disruption of nodal and paranodal organization at the node of Ranvier. This last point is possibly mediated by autoantibodies towards axoglial adhesion molecules which may disrupt sodium and potassium voltage-gated channels clustering leading to a failure of saltatory conduction and the apparition of conduction blocks. The purpose of this article is to overview the main pathophysiologic mechanisms and biomarkers identified in CIDP.

Autoimmune encephalopathies

Over the past 10 years, the continual discovery of novel forms of encephalitis associated with antibodies to cell-surface or synaptic proteins has changed the paradigms for diagnosing and treating disorders that were previously unknown or mischaracterized. We review here the process of discovery, the symptoms, and the target antigens of 11 autoimmune encephalitic disorders, grouped by syndromes and approached from a clinical perspective. Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis, several subtypes of limbic encephalitis, stiff-person spectrum disorders, and other autoimmune encephalitides that result in psychosis, seizures, or abnormal movements are described in detail. We include a novel encephalopathy with prominent sleep dysfunction that provides an intriguing link between chronic neurodegeneration and cell-surface autoimmunity (IgLON5). Some of the caveats of limited serum testing are outlined. In addition, we review the underlying cellular and synaptic mechanisms that for some disorders confirm the antibody pathogenicity. The multidisciplinary impact of autoimmune encephalitis has been expanded recently by the discovery that herpes simplex encephalitis is a robust trigger of synaptic autoimmunity, and that some patients may develop overlapping syndromes, including anti-NMDAR encephalitis and neuromyelitis optica or other demyelinating diseases.

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.

Challenges in the treatment of chronic inflammatory demyelinating polyradiculoneuropathy

Chronic idiopathic demyelinating polyradiculoneuropathy (CIDP) is a rare disease, the most frequent one within the spectrum of the so-called "chronic immune-mediated neuropathies". Challenges in the treatment of CIDP firstly concern its diagnosis, which may be difficult, mainly for the atypical forms. Secondly, challenges encompass the choice of the first-line treatment, such as corticosteroids, intravenous immunoglobulins (IVIg), and plasma exchanges (PE) that have been proven as efficacious by several randomized controlled trials (RCT). Recent reports have focused on both different regimens of corticosteroids, and the occurrence of relapses following treatment with either corticosteroids or IVIg. These data may be helpful for the choice of the first-line treatment and may result in changing the guidelines for treatment of CIDP in clinical practice. The third and more difficult challenge is to manage long-term treatment for CIDP, since no immunomodulatory treatment has to date been proven as efficacious in this situation. Lastly, challenges in the treatment concern the choice of the best outcome measure for CIDP in RCT and clinical practice. The aim of this article is to overview the results of the more recently reported published trials for CIDP, and to give some insights for the current and future management of CIDP.

Fragments of truth: T-cell targets of polyclonal immunoglobulins in autoimmune diseases

The expanding therapeutic use of high-dose intravenous immunoglobulin (IVIg) in autoimmune diseases has raised important practical and conceptual issues over the last few years. These have prompted a number of research efforts aimed at characterizing aspects of the mechanism of action of current IVIg preparations, which might lead to the development of standardized, more cost-effective agents. Although polyclonal IgG in these preparations are mostly thought to act via direct interference with disease-specific, pathogenic autoantibodies, evidence from clinical and experimental work points to the involvement of crucial checkpoints upstream of self-reactive B-cell activation and autoantibody production. Reviewed herein are the results of the most recent studies documenting the crucial role of regulatory T cells (Treg) in the immunomodulatory activity of IVIg, and the molecular mechanisms mediating the effect of specific IgG fragments and glycoforms on Treg activity and the ensuing downregulation of T-cell effector responses of different sign and magnitude. Further progress in this area of translational research may lead to the development of innovative strategies aimed at restoring tolerance in autoimmune diseases.

Specific contactin N-glycans are implicated in neurofascin binding and autoimmune targeting in peripheral neuropathies

Cell adhesion molecules (CAMs) play a crucial role in the formation of the nodes of Ranvier and in the rapid propagation of the nerve impulses along myelinated axons. These CAMs are the targets of autoimmunity in inflammatory neuropathies. We recently showed that a subgroup of patients with aggressive chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) shows autoantibodies to contactin (1). The complex of contactin·Caspr·neurofascin-155 (NF155) enables the formation of paranodal junctions, suggesting that antibody attack against paranodes may participate in the severity of CIDP. In the present study, we mapped the molecular determinants of contactin targeted by the autoantibodies. In three patients, immunoreactivity was directed against the Ig domains of contactin and was dependent on N-glycans. The serum of one patient was selectively directed against contactin bearing mannose-rich N-glycans. Strikingly, the oligomannose type sugars of contactin are required for association with its glial partner NF155 (2). To investigate precisely the role of contactin N-glycans, we have mutated each of the nine consensus N-glycosylation sites independently. We found that the mutation of three sites (N467Q/N473Q/N494Q) in Ig domain 5 of contactin prevented soluble NF155-Fc binding. In contrast, these mutations did not abolish cis-association with Caspr. Next, we showed that the cluster of N-glycosylation sites (Asn-467, Asn-473, and Asn-494) was required for immunoreactivity in one patient. Using cell aggregation assays, we showed that the IgGs from the four CIDP patients prevented adhesive interaction between contactin·Caspr and NF155. Importantly, we showed that the anti-contactin autoantibodies induced alteration of paranodal junctions in myelinated neuronal culture. These results strongly suggest that antibodies to CAMs may be pathogenic and induce demyelination via functional blocking activity.