Conduction block in immune-mediated neuropathy: paranodopathy versus axonopathy.

BACKGROUND AND PURPOSE: Conduction block is a pathognomonic feature of immune-mediated neuropathies. The aim of this study was to advance understanding of pathophysiology and conduction block in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). METHODS: A multimodal approach was used, incorporating clinical phenotyping, neurophysiology, immunohistochemistry and structural assessments. RESULTS: Of 49 CIDP and 14 MMN patients, 25% and 79% had median nerve forearm block, respectively. Clinical scores were similar in CIDP patients with and without block. CIDP patients with median nerve block demonstrated markedly elevated thresholds and greater threshold changes in threshold electrotonus, whilst those without did not differ from healthy controls in electrotonus parameters. In contrast, MMN patients exhibited marked increases in superexcitability. Nerve size was similar in both CIDP groups at the site of axonal excitability. However, CIDP patients with block demonstrated more frequent paranodal serum binding to teased rat nerve fibres. In keeping with these findings, mathematical modelling of nerve excitability recordings in CIDP patients with block support the role of paranodal dysfunction and enhanced leakage of current between the node and internode. In contrast, changes in MMN probably resulted from a reduction in ion channel density along axons. CONCLUSIONS: The underlying pathologies in CIDP and MMN are distinct. Conduction block in CIDP is associated with paranodal dysfunction which may be antibody-mediated in a subset of patients. In contrast, MMN is characterized by channel dysfunction downstream from the site of block.

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.

Massive astrocyte destruction in neuromyelitis optica despite natalizumab therapy.

Auto-antibody mediated astrocyte injury is implicated as a primary event in neuromyelitis optica (NMO) by biomarker, post-mortem and experimental studies that differentiate the condition from multiple sclerosis. We describe the clinical, radiological and neuropathological features of a severe cerebral attack in a natalizumab-treated patient with relapsing myelitis and serum aquaporin-4 antibodies. Our findings support autopsy evidence that abrupt astrocyte destruction precedes demyelination in NMO, and emphasize the importance of serological testing in patients with limited disease. Adherence to current NMO diagnostic criteria may delay treatment, or lead to inappropriate therapy with beta-interferon or natalizumab.

MS: is it one disease?

Neuropathological studies of early multiple sclerosis (MS) tissue have shaped prevailing views of the pathogenesis of the disease. The hallmark of the acute MS lesion, inflammatory demyelination, has been largely accepted as evidence of a macrophage-mediated attack on normal myelin, driven by perivascular and parenchymal autoreactive CD4+ Th1 cells primed in the periphery by an unknown self or foreign antigen(s). Predicated largely upon comparisons with experimental allergic encephalomyelitis, this paradigm has, in recent years, been recognized as a simplification of the events that constitute and perhaps presage lesion formation in the human disease; and the importance of the innate immune cells of the central nervous system, humoral factors, cytotoxic CD8+ T-cells and regulatory T-cells has been emphasized. An influential series of publications by one group, based on histopathological examination of actively demyelinating lesions in selected autopsy and biopsy MS tissue, defined four early lesion subtypes. In a given individual, these subtypes were reported to be mutually exclusive, suggesting that disparate pathogenetic pathways separate patients with clinically indistinguishable syndromes. This schema, which has considerable therapeutic implications, has not been independently verified and has recently been questioned by the finding of a uniform pre-phagocytic pathology and overlap of lesion subtypes in individual patients with typical relapsing and remitting disease. The latter findings would suggest that the heterogeneous features observed in active MS lesions sampled at different time-points are a reflection of the evolution of a single pathophysiological process, perhaps modified in part by genetic factors in individual cases.

Longitudinal assessment of anxiety, depression, and fatigue in people with multiple sclerosis.

OBJECTIVES: No longitudinal studies have concurrently evaluated predictors of anxiety, depression, and fatigue in people with multiple sclerosis (PwMS). This study determined factors that best predicted anxiety, depression, and fatigue in MS patients from a large pool of disease, cognitive, life-event stressor (LES), psychosocial, life-style, and demographic factors. DESIGN: A 2-year prospective longitudinal study evaluated predictors of psychological distress and fatigue in PwMS. METHODS: One hundred and one consecutive participants with MS were recruited from two MS clinics in Sydney, Australia. LES, anxiety, depression, and fatigue were assessed at baseline and at 3-monthly intervals for 2-years. Disease, cognitive, demographic, psychosocial, and life-style factors were assessed at baseline. Patient-reported relapses were recorded and corroborated by neurologists or evaluated against accepted relapse criteria. RESULTS: Depression strongly predicted anxiety and fatigue, and anxiety and fatigue strongly predicted later depression. Psychological distress (i.e. anxiety, depression) was also predicted by a combination of unhealthy behaviours (e.g. drug use, smoking, no exercise, or relaxation) and psychological factors (e.g. low optimism, avoidance coping), similar to the results of community-based studies. However, state-anxiety and fatigue were also predicted by immunotherapy status, and fatigue was also predicted by LES and demographics. CONCLUSIONS: These results suggest that similar factors might underpin psychological distress and fatigue in MS patients and community-well samples, although MS treatment factors may also be important. These results might assist clinicians in determining which MS patients are at greatest risk of developing anxiety, depression, or fatigue.

Relationship between stress and relapse in multiple sclerosis: Part I. Important features.

OBJECTIVE: The aim of this two-year prospective study was to examine the relationship between multiple aspects of life-event stress and relapse in multiple sclerosis (MS) patients. BACKGROUND: Few studies have defined the critical features of this life-event stress; for example, stressor duration, frequency, severity, disease-dependency, valency, or stressor constructs, such as the propensity to cause emotional distress/threat or the frustration of life goals. METHODS: 101 consecutive participants with MS were recruited from two MS clinics in Sydney, Australia. Stressful life events were assessed at study-entry and at three-monthly intervals for two years. Patient-reported relapses were recorded and corroborated by neurologists or evaluated against accepted relapse criteria. RESULTS: Acute events, but not chronic difficulties (CDs), predicted relapse occurrence: acute stressor frequency counts predicted greater relapse risk, along with low disability score (EDSS) and being male. We also confirmed the bi-directional stress-illness hypothesis: stressors predicted relapse, and relapse separately predicted stressors. CONCLUSIONS: Life-event stress impacts to a small degree on MS relapse. The number and not the severity of acute stressors are most important; chronic stressors do not predict later relapse. Males and those with early stage disease are also at greater risk of relapse. MS patients should be encouraged to reduce acute stressors during times of high stress, and feel reassured that disease-related chronic stressors do not increase their relapse risk.

Relationship between stress and relapse in multiple sclerosis: Part II. Direct and indirect relationships.

OBJECTIVE: The aim of this two-year prospective study was to determine which factors were: (i) directly related and/or (ii) indirectly related to multiple sclerosis (MS) relapse. These factors included life-event stressors, disease, demographic, psychosocial and lifestyle factors. BACKGROUND: Relatively little attention has been paid to the role of non-clinical relapse predictors (other than stressful life-events) in MS, or factors that indirectly impact on the stress-relapse relationship. METHODS: A total of 101 consecutive participants with MS were recruited from two MS clinics in Sydney, Australia. Stressful life-events, depression, anxiety and fatigue were assessed at study-entry and at three-monthly intervals for two years. Disease, demographic, psychosocial and lifestyle factors were assessed at baseline. Patient-reported relapses were recorded and corroborated by neurologists or evaluated against accepted relapse criteria. RESULTS: MS relapse was predicted by acute stressor frequency counts, coping responses that utilized social support, and being born in Australia, but not by chronic stressors, disease, demographic, psychosocial or lifestyle factors. No factors were found to indirectly impact on the stress relapse relationship. CONCLUSIONS: The number rather than severity of stressors was most important in relation to MS relapse risk, along with coping responses that utilized social support, suggesting that MS patients should avoid situations that are likely to generate multiple stressors or which provide few avenues for social support.

Gene expression and genotyping studies implicate the interleukin 7 receptor in the pathogenesis of primary progressive multiple sclerosis.

Multiple sclerosis (MS) is an enigmatic disease of the central nervous system resulting in sclerotic plaques with the pathological hallmarks of demyelination and axonal damage, which can be directly or indirectly orchestrated by cells from the peripheral circulation. The majority of patients with MS follow a relapsing-remitting course in the early stages of the disease (RRMS) but most ultimately enter a secondary progressive phase (SPMS). About 10% of patients follow a primary progressive course from the onset (PPMS). We measured gene expression in whole blood of people with and without chronic progressive MS (CPMS), PPMS and SPMS, to discover genes which may be differentially expressed in peripheral blood in active disease, and so identify pathologically significant genes and pathways; and we investigated genetic differences in the promoters of dysregulated genes encoded in genomic regions associated with MS. If SPMS and PPMS were independently compared to the controls, there was little overlap in the set of most dysregulated genes. Ribosomal protein genes, whose expression is usually associated with cell proliferation and activation, were dramatically over-represented in the set of most down-regulated genes in PPMS compared to SPMS (P < 10(-4), chi(2)). The T cell proliferation gene IL7R (CD127) was also underexpressed in PPMS, but was up-regulated in SPMS compared to the controls. One interleukin 7 receptor (IL7R) promoter single nucleotide polymorphism (SNP), -504 C, was undertransmitted in PPMS trios (P = 0.05, TDT), and carriers of this allele were under-represented in PPMS cases from two independent patient cohorts (combined P = 0.006, FE). The four known IL7R promoter haplotypes were shown to have similar expression levels in healthy controls, but not in CPMS (P < 0.01, t test). These data support the hypothesis that PPMS has significant pathogenetic differences from SPMS, and that IL7R may be a useful therapeutic target in PPMS.

A review of stress-relapse interactions in multiple sclerosis: important features and stress-mediating and -moderating variables.

Studies do not provide a consensus opinion of the relationship between stress and relapse in relapsing-remitting multiple sclerosis (RRMS). Few studies have defined the critical features of these stressful situations, or examined the role of stress-mediating and -moderating variables. Available evidence indicates that the relationship between life stress and relapse is complex, and is likely to depend on factors such as stressor chronicity, frequency, severity and type, and individual patient characteristics such as depression, health locus of control and coping strategy use. Little is known about how these factors, individually or in combination, are related to MS disease activity. Viral infections are also likely to precipitate relapse in MS, and significant life-stress may further enhance this relationship. The nature and strength of these interrelationships have strong clinical implications. MS patients are particularly vulnerable to a deteriorating cycle of stressful life events, illness episodes and disability. Timely multidisciplinary care interventions aimed at both minimizing psychological distress and physical symptoms may halt this downward reciprocal cycle. Little is known of the pathogenesis of these putative stress-induced changes in disease activity, and almost all stressor studies suffer from some biases or limitations.

A locus for hereditary sensory neuropathy with cough and gastroesophageal reflux on chromosome 3p22-p24.

Hereditary sensory neuropathy type I (HSN I) is a group of dominantly inherited degenerative disorders of peripheral nerve in which sensory features are more prominent than motor involvement. We have described a new form of HSN I that is associated with cough and gastroesophageal reflux. To map the chromosomal location of the gene causing the disorder, a 10-cM genome screen was undertaken in a large Australian family. Two-point analysis showed linkage to chromosome 3p22-p24 (Zmax=3.51 at recombination fraction (theta) 0.0 for marker D3S2338). A second family with a similar phenotype shares a different disease haplotype but segregates at the same locus. Extended haplotype analysis has refined the region to a 3.42-cM interval, flanked by markers D3S2336 and D3S1266.

Hamster cardiac xenografts are protected against antibody mediated damage, early after transplantation to Lewis rats.

Antibodies play a crucial role in the rejection of xenografts. We tested the hypothesis that xenografts are protected against antibody-mediated attack early after transplantation in a concordant model. We investigated the role of xenoreactive antibodies as a stimulus for protection and the effects of a total blockade of the antibody response by the leflunomide analog malononitrilamide 279. Hamster cardiac xenografts were transplanted to Lewis rat recipients. Second transplants and retransplants of xenografts were performed to untreated rats that had a xenograft in place for 3 d. Untreated rats rejected hamster cardiac xenografts after 4.0 +/- 0.0 d. Significant levels of anti-donor IgM, as measured by flowcytometry, were present on day 3 after transplantation (11.2% +/- 2.8 vs. 1.2% +/- 0.0 on day 0, P < 0.001). 'Fresh' second xenografts transplanted to rats that had a first xenograft in place for 3 d and had anti-hamster antibodies, underwent hyperacute rejection. The first xenografts remained functioning. Xenografts that were removed on day 3 from untreated rats and then retransplanted remained functioning. Xenografts that were removed on d 3 from rats that had been treated with malononitrilamide 279, 15 mg/kg/d and were retransplanted underwent hyperacute rejection. IgM levels at the time of removal were 1.1% +/- 0.5 in these rats and not different from baseline (P = 0.96). We conclude that xenografts are protected against antibody-mediated damage early after transplantation. The presence of anti-donor antibodies might be an essential stimulus for the induction of protection. There seems to be a delicate balance between the injurious and protective effects of antibodies. Treatment strategies that are designed to block antibody formation completely might prevent the induction of protection.

A spontaneous novel XK gene mutation in a patient with McLeod syndrome.

A 29-year-old man with a history of elevated creatine kinase and necrotizing myopathy was reviewed. Prominent red cell acanthocytosis in association with reduced Kell antigen expression was present, findings consistent with the McLeod syndrome. Investigation of the patient's XK gene revealed a novel TGG- to-TAG transition at position 1023 in exon 3. This point mutation creates an in-frame stop codon (W314X), and predicts a truncated XK protein of 313 amino acids, compared with 444 amino acids in the normal XK protein. The mutation was not identified in the patient's mother or sister indicating that this mutation was spontaneous.

P0 protein is a target antigen in chronic inflammatory demyelinating polyradiculoneuropathy.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is widely regarded as an autoimmune disorder, although the autoantigen remains unknown. In this study, the sera of 21 CIDP patients were examined by immunofluorescence for antimyelin activity and by Western blotting for binding to myelin proteins. Six sera contained anti-P0 immunoglobulin G antibodies, and four of these caused conduction block and demyelination following intraneural injection in experimental animals. Absorption with P0 protein eliminated the demyelinating activity. These results show that P0 is an autoantigen in some patients with CIDP. Since P0 possesses powerful adhesion properties and is largely responsible for myelin compaction, the demonstration of demyelination by human anti-P0 antibodies provides new insight into this important and common immunopathological process.

Dominance of autoreactive T cell-mediated delayed-type hypersensitivity or antibody-mediated demyelination results in distinct forms of experimental autoimmune neuritis in the Lewis rat.

The role of anti-myelin antibodies in the pathogenesis of experimental autoimmune neuritis (EAN) induced in the Lewis rat by immunization with peripheral nerve myelin has been assessed. Passive transfer with lymph node cells (LNC) or purified serum immunoglobulin from rats with EAN was employed to directly measure the contribution of B cells and anti-myelin antibodies to demyelination and disease. Lewis rats with EAN transferred by LNC or purified serum immunoglobulin from EAN donors in conjunction with a low dose of P2-specific CD4+ T cells demonstrated profound histopathological and neurophysiological evidence of demyelination during disease. In contrast, the classical adoptive transfer model of EAN in the Lewis rat induced by the injection of P2-specific CD4+ T cells was characterized by histopathological and neurophysiological evidence of axonal dysfunction and degeneration with limited demyelination. These findings demonstrate that the synergistic action of T cells and anti-myelin antibodies mediating demyelination or purely T cell mediated axonal dysfunction and degeneration are distinct pathways by which a specific autoimmune response in the peripheral nervous system can cause neurological disease.

Severe infantile axonal neuropathy with respiratory failure.

We describe 5 infants (4 male, 1 female) with a severe intractable form of motor-sensory axonal neuropathy. All became ventilator-dependent, 4 have since died and 1 remains static. Diaphragmatic paralysis was an early feature with generalized neuropathy evolving rapidly. Nerve conduction studies and biopsies were consistent with axonal disease. This disorder could be a new condition or part of the spectrum of inherited neuropathies of the axonal degenerative type. It may be that there is a "switching-off" in the infant's Schwann cell-axonal interactions in utero or in the early postnatal period, resulting in severe progressive deterioration and then a static period without recovery.

Introduction to the synthesis and purification of oligonucleotides.

Modern nucleic acid synthesizers utilize phosphite triester chemistries that employ stable phosphoramidite monomers to build a growing polymer. These robust reactions allow easy generation of specific oligodeoxyribo- and oligoribonucleotides with a variety of labels, modified linkages, and nonstandard bases. Strategies are given for the maximization of synthetic yield, the generation of sequences containing site-specific modifications, and the isolation of synthetic oligonucleotides. Protocols describe monitoring the progress of synthesis via the trityl assay and methods for deprotection.

Synthesis and purification of oligonucleotides.

This unit provides strategies on the maximization of synthetic yield, the generation of sequences containing site-specific modifications, and the isolation of synthetic oligonucleotides. Protocols describe monitoring the progress of synthesis via the trityl assay and methods for deprotection of DNA and RNA oligonucleotides.

Purification of oligonucleotides using denaturing polyacrylamide gel electrophoresis.

Cloning vectors derived from filamentous phage are extremely useful because they allow cloned DNA to be isolated as either single- or double-stranded DNA. This unit contains protocols for preparing both forms of DNA and for characterizing inserts in M13-derived vectors. A protocol is also presented for preparing single-stranded DNA from plasmids using superinfection with helper phage. This method is advantageous because it allows cloned DNA to be maintained in the form of a plasmid while permitting single-stranded DNA to be isolated for DNA sequencing.

Separation of small DNA fragments by conventional gel electrophoresis.

Large amounts of small (<1000-bp) DNA fragments can be separated by conventional electrophoretic means. The purified fragments can then be used for cloning, sequencing, and labeling. In this unit, the techniques of DNA separation via both nondenaturing polyacrylamide and sieving agarose electrophoresis are discussed. Methods are detailed for the pouring and electrophoresis of nondenaturing polyacrylamide gels, followed by elution of the labeled or unlabeled separated DNA fragments from the gels by either passive diffusion or electroelution. A method is also provided for the use of sieving agarose, a specially treated type of agarose designed to be used at high concentrations. Poured and run like conventional agarose gels, this matrix can resolve small DNA fragments much like a nondenaturing polyacrylamide gel.

Unusual muscle pathology in McLeod syndrome.

Muscle pathology in McLeod syndrome is usually mild; patchy necrotic or regenerating fibres, occasional internal nuclei, and the absence of an inflammatory cell infiltrate are the usual findings. We report on a 29 year old man presenting with chronic fatiguability and excessive sweating in whom an open quadriceps muscle biopsy demonstrated grouped necrotic fibres accompanied by striking patchy mononuclear cell infiltrates. The diagnosis of McLeod syndrome was made on the basis of red blood cell acanthocytosis, raised serum creatine kinase, and weak expression of Kell blood group antigens. The quadriceps muscle infiltrate consisted principally of histologically typical macrophages. These cells had prominent nucleoli, displayed numerous mitoses, and were strongly CD68+. A small population of typical CD3+, CD43+ lymphocytes was also present. In addition, a small population of large atypical CD3+ cells was noted. Immunoperoxidase stains for CD20, CD30, CD79a, and CD56 were negative. Immunocytochemical studies for the common muscular dystrophies were normal. The muscle biopsy findings highlight a potential for confusion of this condition with idiopathic polymyositis. The expanding range of muscle pathology reported in McLeod syndrome, to which this case adds, may reflect variable involvement of the XK gene on chromosome Xp21, or of the adjacent loci of Duchenne muscular dystrophy and chronic granulomatous disease.