Antibody responses to peptides of peripheral nerve myelin proteins P0 and P2 in patients with inflammatory demyelinating neuropathy

Animal models of immune-mediated demyelinating polyneuropathies

Immune-mediated demyelinating polyneuropathies (IMDPs) are rare disorders in which dysregulated adaptive immune responses cause peripheral nerve demyelinating inflammation and axonal injury in susceptible individuals. Despite significant advances in understanding IMDP pathogenesis guided by patient data and representative mammalian models, specific therapies are lacking. Significant knowledge gaps in IMDP pathogenesis still exist, e.g. precise antigen(s) and mechanisms that initially trigger immune system activation and identification of large population disease susceptibility factors. The initial directional cues for antigen-specific effector or autoreactive leukocyte trafficking into peripheral nerves are also unknown. An overview of current animal models, with emphasis on the experimental autoimmune neuritis and spontaneous autoimmune peripheral polyneuropathy models, is provided. Insights on the initial directional cues for peripheral nerve tissue specific autoimmunity using a novel Major Histocompatibility Complex class II conditional knockout mouse strain are also discussed, suggesting an essential research tool to study cell- and time-dependent adaptive immunity in autoimmune diseases.

Expanding our understanding of Guillain-Barré syndrome: Recent advances and clinical implications

Guillain-Barré syndrome (GBS) is a rare yet potentially life-threatening disorder of the peripheral nervous system (PNS), characterized by substantial clinical heterogeneity. Although classified as an autoimmune disease, the immune mechanisms underpinning distinct GBS subtypes remain largely elusive. Traditionally considered primarily antibody-mediated, the pathophysiology of GBS lacks clarity, posing challenges in the development of targeted and effective treatments. Nevertheless, recent investigations have substantially expanded our understanding of the disease, revealing an involvement of autoreactive T cell immunity in a major subtype of GBS patients and opening new biomedical perspectives. This review highlights these discoveries and offers a comprehensive overview of current knowledge about GBS, including ongoing challenges in disease management.

Autoreactive T cells target peripheral nerves in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is a rare heterogenous disorder of the peripheral nervous system, which is usually triggered by a preceding infection, and causes a potentially life-threatening progressive muscle weakness1. Although GBS is considered an autoimmune disease, the mechanisms that underlie its distinct clinical subtypes remain largely unknown. Here, by combining in vitro T cell screening, single-cell RNA sequencing and T cell receptor (TCR) sequencing, we identify autoreactive memory CD4+ cells, that show a cytotoxic T helper 1 (TH1)-like phenotype, and rare CD8+ T cells that target myelin antigens of the peripheral nerves in patients with the demyelinating disease variant. We characterized more than 1,000 autoreactive single T cell clones, which revealed a polyclonal TCR repertoire, short CDR3β lengths, preferential HLA-DR restrictions and recognition of immunodominant epitopes. We found that autoreactive TCRβ clonotypes were expanded in the blood of the same patient at distinct disease stages and, notably, that they were shared in the blood and the cerebrospinal fluid across different patients with GBS, but not in control individuals. Finally, we identified myelin-reactive T cells in the nerve biopsy from one patient, which indicates that these cells contribute directly to disease pathophysiology. Collectively, our data provide clear evidence of autoreactive T cell immunity in a subset of patients with GBS, and open new perspectives in the field of inflammatory peripheral neuropathies, with potential impact for biomedical applications.

Current Biomarker Strategies in Autoimmune Neuromuscular Diseases

Inflammatory neuromuscular disorders encompass a diverse group of immune-mediated diseases with varying clinical manifestations and treatment responses. The identification of specific biomarkers has the potential to provide valuable insights into disease pathogenesis, aid in accurate diagnosis, predict disease course, and monitor treatment efficacy. However, the rarity and heterogeneity of these disorders pose significant challenges in the identification and implementation of reliable biomarkers. Here, we aim to provide a comprehensive review of biomarkers currently established in Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), myasthenia gravis (MG), and idiopathic inflammatory myopathy (IIM). It highlights the existing biomarkers in these disorders, including diagnostic, prognostic, predictive and monitoring biomarkers, while emphasizing the unmet need for additional specific biomarkers. The limitations and challenges associated with the current biomarkers are discussed, and the potential implications for disease management and personalized treatment strategies are explored. Collectively, biomarkers have the potential to improve the management of inflammatory neuromuscular disorders. However, novel strategies and further research are needed to establish clinically meaningful biomarkers.

Sex differences in Guillain Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy and experimental autoimmune neuritis

Guillain Barré syndrome (GBS) and its variants, and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP and its variants, are regarded as immune mediated neuropathies. Unlike in many autoimmune disorders, GBS and CIDP are more common in males than females. Sex is not a clear predictor of outcome. Experimental autoimmune neuritis (EAN) is an animal model of these diseases, but there are no studies of the effects of sex in EAN. The pathogenesis of GBS and CIDP involves immune response to non-protein antigens, antigen presentation through non-conventional T cells and, in CIDP with nodopathy, IgG4 antibody responses to antigens. There are some reported sex differences in some of these elements of the immune system and we speculate that these sex differences could contribute to the male predominance of these diseases, and suggest that sex differences in peripheral nerves is a topic worthy of further study.

The immune response and aging in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) consists of various autoimmune subtypes in which the peripheral nervous system (PNS) is attacked. CIDP can follow a relapsing-remitting or progressive course where the resultant demyelination caused by immune cells (e.g., T cells, macrophages) and antibodies can lead to disability in patients. Importantly, the age of CIDP patients has a role in their symptomology and specific variants have been associated with differing ages of onset. Furthermore, older patients have a decreased frequency of functional recovery after CIDP insult. This may be related to perturbations in immune cell populations that could exacerbate the disease with increasing age. In the present review, the immune profile of typical CIDP will be discussed followed by inferences into the potential role of relevant aging immune cell populations. Atypical variants will also be briefly reviewed followed by an examination of the available studies on the immunology underlying them.

Comprehensive approaches for diagnosis, monitoring and treatment of chronic inflammatory demyelinating polyneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is the most common chronic inflammatory neuropathy. CIDP is diagnosed according to the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria, which combine clinical features with the electrophysiological evidence of demyelination. However, firstly, diagnosis is challenging, as some patients e.g. with severe early axonal damage do not fulfil the criteria. Secondly, objective and reliable tools to monitor the disease course are lacking. Thirdly, about 25% of CIDP patients do not respond to evidence-based first-line therapy. Recognition of these patients is difficult and treatment beyond first-line therapy is based on observational studies and case series only. Individualized immunomodulatory treatment does not exist due to the lack of understanding of essential aspects of the underlying pathophysiology.

Novel diagnostic imaging techniques and molecular approaches can help to solve these problems but do not find enough implementation. This review gives a comprehensive overview of novel diagnostic techniques and monitoring approaches for CIDP and how these can lead to individualized treatment and better understanding of pathophysiology.

Peripheral Demyelinating Diseases: From Biology to Translational Medicine

Demyelinating diseases represent a spectrum of disorders that impose significant burden on global economy and society. Generally, the prognosis of these diseases is poor and there is no available cure. In recent decades, research has shed some light on the biology and physiology of Schwann cells and its neuroprotective effects in the peripheral nervous system (PNS). Insults to the PNS by various infectious agents, genetic predisposition and immune-related mechanisms jeopardize Schwann cell functions and cause demyelination. To date, there are no effective and reliable biomarkers for PNS-related diseases. Here, we aim to review the following: pathogenesis of various types of peripheral demyelinating diseases such as Guillain-Barre syndrome, Chronic Inflammatory Demyelinating Polyradiculoneuropathy, Anti-Myelin Associated Glycoprotein Neuropathy, POEMS syndrome, and Charcot-Marie-Tooth disease; emerging novel biomarkers for peripheral demyelinating diseases, and Schwann cell associated markers for demyelination.

Diagnostic insights into chronic-inflammatory demyelinating polyneuropathies

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare immune-mediated neuropathy with demyelination of nerve fibers as leading morphological feature. The course of disease can be chronic progressive or remitting relapsing. Whereas for acute immune-mediated neuropathies several serological markers have been identified and used successfully in clinical routine, the serological diagnosis of chronic variants such as CIDP has not yet been evolved satisfactory. The typical CIDP and its various atypical variants are characterized by a certain diversity of clinical phenotype and response to treatment. Thus, diagnostic markers could aid in the differential diagnosis of CIDP variants and stratification of patients for a better treatment response. Most patients respond well to a causal therapy including steroids, intravenous immunoglobulins and plasmapheresis. Apart from electrophysiological and morphological markers, several autoantibodies have been reported as candidate markers for CIDP, including antibodies against glycolipids or paranodal/nodal molecules. The present review provides a summary of the progress in autoantibody testing in CIDP and its possible implication on the stratification of the CIDP variants and treatment response.

Immunotherapy of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS), the most common cause of acute neuromuscular weakness and paralysis worldwide, encompasses a group of acute immune-mediated disorders restricted to peripheral nerves and roots. Immune-mediated attack of peripheral nervous system myelin, axons or both is presumed to be triggered by molecular mimicry, with both cell- and humoral-dependent mechanisms implicated in disease pathogenesis. Good circumstantial evidence exists for a pathogenic role for molecular mimicry in GBS pathogenesis, especially with its axonal forms, providing insights that could guide future immunotherapy. Intravenous immunoglobulin (IVIg) and plasma exchange (PE) are the most commonly prescribed immunotherapies for GBS with variable efficacy dependent on GBS subtype, severity at initial presentation and other clinical and electrophysiologic prognostic factors. The mechanisms of action of IVIg and PE are not known definitely. Despite recent significant advances in molecular biology that provide insights into GBS pathogenesis, no advances in therapeutics or significant improvements in patient outcomes have occurred over the past three decades. We summarize the clinical aspects of GBS, its current pathogenesis and immunotherapy, and highlight the potential of leukocyte trafficking inhibitors as novel disease-specific immunotherapeutic drugs.

Neurofascin and Compact Myelin Antigen-Specific T Cell Response Pattern in Chronic Inflammatory Demyelinating Polyneuropathy Subtypes

Objective

The objective of this study is to investigate whether chronic inflammatory demyelinating polyneuropathy (CIDP) and its subtypes differ in their type 1 T-helper (TH1) cell response against nodal/paranodal neurofascin (NF186, NF155) as well as myelin protein zero (P0 180–199) and myelin basic protein (MBP 82–100).

Methods

Interferon-gamma (IFN-γ) enzyme-linked immunospot assay was used to detect antigen-specific T cell responses in 48 patients suffering typical CIDP (n = 18), distal acquired demyelinating polyneuropathy (n = 8), multifocal acquired demyelinating sensory and motor polyneuropathy (MADSAM; n = 9), and sensory CIDP (n = 13) compared to other non-immune polyneuropathy (ON; n = 19) and healthy controls (n = 9).

Results

Compared to controls, MADSAM and sensory CIDP patients showed broadest IFN-γ T cell responses to all four antigens. Positive IFN-γ responses against two or more antigens were highly predictive for CIDP (positive predictive value = 0.95) and were found in 77% of CIDP patients. Patients with limited antigen-specific response were females, more severely affected with neuropathic pain and proximal paresis. The area under the receiver operating characteristics curve (AUC) of NF186 in MADSAM was 0.94 [95% confidential interval (CI) 0.82–1.00] compared to ON. For sensory CIDP, AUC of P0 180–199 was 0.94 (95% CI 0.86–1.00) and for MBP 82–100 0.95 (95% CI 0.88–1.00) compared to ON.

Conclusion

Cell-mediated immune responses to (para)nodal and myelin-derived antigens are common in CIDP. TH1 response against NF186 may be used as a biomarker for MADSAM and TH1 responses against P0 180–199 and MBP 82–100 as biomarkers for sensory CIDP. Larger multicenter studies study are warranted in order to establish these immunological markers as a diagnostic tools.

The Role of Peripheral Myelin Protein 2 in Remyelination

The protein component of the myelin layer is essential for all aspects of peripheral nerves, and its deficiency can lead to structural and functional impairment. The presence of peripheral myelin protein 2 (P2, PMP2, FABP8, M-FABP) in Schwann cells has been known for decades and shown recently to be involved in the lipid homeostasis in the peripheral neural system. However, its precise role during de- and remyelination has yet to be elucidated. To this end, we assessed remyelination after sciatic nerve crush injury in vivo, and in an experimental de/remyelination ex vivo myelinating culture model in P2-deficient (P2 -/- ) and wild-type (WT) animals. In vivo, the nerve crush paradigm revealed temporal structural and functional changes in P2 -/- mice as compared to WT animals. Concomitantly, P2 -/- DRG cultures demonstrated the presence of shorter internodes and enlarged nodes after ex vivo de/remyelination. Together, these data indicate that P2 may play a role in remyelination of the injured peripheral nervous system, presumably by affecting the nodal and internodal configuration.

Novel pathomechanisms in inflammatory neuropathies

Inflammatory neuropathies are rare autoimmune-mediated disorders affecting the peripheral nervous system. Considerable progress has recently been made in understanding pathomechanisms of these disorders which will be essential for developing novel diagnostic and therapeutic strategies in the future. Here, we summarize our current understanding of antigenic targets and the relevance of new immunological concepts for inflammatory neuropathies. In addition, we provide an overview of available animal models of acute and chronic variants and how new diagnostic tools such as magnetic resonance imaging and novel therapeutic candidates will benefit patients with inflammatory neuropathies in the future. This review thus illustrates the gap between pre-clinical and clinical findings and aims to outline future directions of development.

Antibodies against peripheral nerve antigens in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a heterogeneous disease in which diverse autoantibodies have been described but systematic screening has never been performed. Detection of CIDP-specific antibodies may be clinically useful. We developed a screening protocol to uncover novel reactivities in CIDP. Sixty-five CIDP patients and 28 controls were included in our study. Three patients (4.6%) had antibodies against neurofascin 155, four (6.2%) against contactin-1 and one (1.5%) against the contactin-1/contactin-associated protein-1 complex. Eleven (18.6%) patients showed anti-ganglioside antibodies, and one (1.6%) antibodies against peripheral myelin protein 2. No antibodies against myelin protein zero, contactin-2/contactin-associated protein-2 complex, neuronal cell adhesion molecule, gliomedin or the voltage-gated sodium channel were detected. In IgG experiments, three patients (5.3%) showed a weak reactivity against motor neurons; 14 (24.6%) reacted against DRG neurons, four of them strongly (7.0%), and seven (12.3%) reacted against Schwann cells, three of them strongly (5.3%). In IgM experiments, six patients (10.7%) reacted against DRG neurons, while three (5.4%) reacted against Schwann cells. However, results were not statistically significant when compared to controls. Immunoprecipitation experiments identified CD9 and L1CAM as potential antigens, but reactivity could not be confirmed with cell-based assays. In summary, we describe a diverse autoantibody repertoire in CIDP patients, reinforcing the hypothesis of CIDP’s pathophysiological heterogeneity.

Autoantibodies in chronic inflammatory neuropathies: diagnostic and therapeutic implications

The chronic inflammatory neuropathies (CINs) are rare, very disabling autoimmune disorders that generally respond well to immune therapies such as intravenous immunoglobulin (IVIg). The most common forms of CIN are chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multifocal motor neuropathy, and polyneuropathy associated with monoclonal gammopathy of unknown significance. The field of CIN has undergone a major advance with the identification of IgG4 autoantibodies directed against paranodal proteins in patients with CIDP. Although these autoantibodies are only found in a small subset of patients with CIDP, they can be used to guide therapeutic decision-making, as these patients have a poor response to IVIg. These observations provide proof of concept that identifying the target antigens in tissue-specific antibody-mediated autoimmune diseases is important, not only to understand their underlying pathogenic mechanisms, but also to correctly diagnose and treat affected patients. This state-of-the-art Review focuses on the role of autoantibodies against nodes of Ranvier in CIDP, a clinically relevant emerging field of research. The role of autoantibodies in other immune-mediated neuropathies, including other forms of CIN, primary autoimmune neuropathies, neoplasms, and systemic diseases that resemble CIN, are also discussed.

Characterization of host response to Cryptococcus neoformans through quantitative proteomic analysis of cryptococcal meningitis co-infected with HIV

Cryptococcal meningitis is the most common opportunistic fungal infection causing morbidity and mortality (>60%) in HIV-associated immunocompromised individuals caused by Cryptococcus neoformans. Molecular mechanisms of cryptococcal infection in brain have been studied using experimental animal models and cell lines. There are limited studies for the molecular understanding of cryptococcal meningitis in human brain. The proteins involved in the process of invasion and infection in human brain still remains obscure. To this end we carried out mass spectrometry-based quantitative proteomics of frontal lobe brain tissues from cryptococcal meningitis patients and controls to identify host proteins that are associated with the pathogenesis of cryptococcal meningitis. We identified 317 proteins to be differentially expressed (≥2-fold) from a total of 3423 human proteins. We found proteins involved in immune response and signal transduction to be differentially expressed in response to cryptococcal infection in human brain. Immune response proteins including complement factors, major histocompatibility proteins, proteins previously known to be involved in fungal invasion to brain such as caveolin 1 and actin were identified to be differentially expressed in cryptococcal meningitis brain tissues co-infected with HIV. We also validated the expression status of 5 proteins using immunohistochemistry. Overexpression of major histocompatibility complexes, class I, B (HLA-B), actin alpha 2 smooth muscle aorta (ACTA2) and caveolin 1 (CAV1) and downregulation of peripheral myelin protein 2 (PMP2) and alpha crystallin B chain (CRYAB) in cryptococcal meningitis were confirmed by IHC-based validation experiments. This study provides the brain proteome profile of cryptococcal meningitis co-infected with HIV for a better understanding of the host response associated with the disease.

Autoimmune-mediated peripheral neuropathies and autoimmune pain

Peripheral neuropathies have diverse acquired and inherited causes. The autoimmune neuropathies represent an important category where treatment is often available. There are overlapping signs and symptoms between autoimmune neuropathies and other forms. Making a diagnosis can be challenging and first assisted by electrophysiologic and sometimes pathologic sampling, with autoimmune biomarkers providing increased assistance. Here we provide a review of the autoimmune and inflammatory neuropathies, their available biomarkers, and approaches to treatment. Also discussed is new evidence to support a mechanism of autoimmune pain.

Inflammatory neuropathies: pathology, molecular markers and targets for specific therapeutic intervention

Inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both. Inflammatory neuropathies may be divided into three major disease categories: Guillain-Barré syndrome (particularly the acute inflammatory demyelinating polyradiculoneuropathy variant), chronic inflammatory demyelinating polyradiculoneuropathy and nonsystemic vasculitic neuropathy (or peripheral nerve vasculitis). Despite major advances in molecular biology, pathology and genetics, the pathogenesis of these disorders remains elusive. There is insufficient knowledge on the mechanisms of hematogenous leukocyte trafficking into the peripheral nervous system to guide the development of specific molecular therapies for immune-mediated inflammatory neuropathies compared to disorders such as psoriasis, inflammatory bowel disease, rheumatoid arthritis or multiple sclerosis. The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium. This review discusses our current knowledge of the classic pathological features of inflammatory neuropathies, attempts at molecular classification and genetic determinants, the utilization of in vitro and in vivo animal models to determine pathogenic mechanisms at the interface between the systemic circulation and the peripheral nervous system relevant to these disorders and prospects for future potential molecular pathology biomarkers and targets for specific therapeutic intervention.

Biomarkers of Guillain-Barré Syndrome: Some Recent Progress, More Still to Be Explored

Guillain-Barré syndrome (GBS), the axonal subtype of which is mainly triggered by C. jejuni with ganglioside-mimicking lipooligosaccharides (LOS), is an immune-mediated disorder in the peripheral nervous system (PNS) accompanied by the disruption of the blood-nerve barrier (BNB) and the blood-cerebrospinal fluid barrier (B-CSF-B). Biomarkers of GBS have been extensively explored and some of them are proved to assist in the clinical diagnosis and in monitoring disease progression as well as in assessing the efficacy of immunotherapy. Herein, we systemically review the literature on biomarkers of GBS, including infection-/immune-/BNB, B-CSF-B, and PNS damage-associated biomarkers, aiming at providing an overview of GBS biomarkers and guiding further investigations. Furthermore, we point out further directions for studies on GBS biomarkers.

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.

The frequencies of Killer immunoglobulin-like receptors and their HLA ligands in chronic inflammatory demyelinating polyradiculoneuropathy are similar to those in Guillian Barre syndrome but differ from those of controls, suggesting a role for NK cells in pathogenesis

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired inflammatory neuropathy, which has similar clinical and pathological features to Guillain-Barré Syndrome (GBS), but differs in time course. We investigated the frequency of genes encoding Killer immunoglobulin-like receptors and their HLA ligands in subjects with CIDP, in subjects with GBS and in healthy controls. There were no differences in KIR gene frequency among the 3 groups. The gene frequencies for HLA-B Bw4-I were significantly greater in CIDP than HC, but did not differ from GBS. The frequency of the combination of 3DL1/HLA-B Bw4I was greater in CIDP than HC, but did not differ from that of GBS. These data raise the possibility of NK cell function being an important factor in the pathogenesis of CIDP.

Exome Sequence Analysis Suggests that Genetic Burden Contributes to Phenotypic Variability and Complex Neuropathy

Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous distal symmetric polyneuropathy. Whole-exome sequencing (WES) of 40 individuals from 37 unrelated families with CMT-like peripheral neuropathy refractory to molecular diagnosis identified apparent causal mutations in ∼ 45% (17/37) of families. Three candidate disease genes are proposed, supported by a combination of genetic and in vivo studies. Aggregate analysis of mutation data revealed a significantly increased number of rare variants across 58 neuropathy-associated genes in subjects versus controls, confirmed in a second ethnically discrete neuropathy cohort, suggesting that mutation burden potentially contributes to phenotypic variability. Neuropathy genes shown to have highly penetrant Mendelizing variants (HPMVs) and implicated by burden in families were shown to interact genetically in a zebrafish assay exacerbating the phenotype established by the suppression of single genes. Our findings suggest that the combinatorial effect of rare variants contributes to disease burden and variable expressivity.

Optimizing IgG therapy in chronic autoimmune neuropathies: a hypothesis driven approach

Prolonged intravenous immunoglobulin (IVIG) therapy is used for the chronic autoimmune neuropathies chronic idiopathic demyelinating polyneuropathy and multifocal motor neuropathy, but the doses and treatment intervals are usually chosen empirically due to a paucity of data from dose-response studies. Recent studies of the electrophysiology and immunology of these diseases suggest that antibody-induced reversible dysfunction of nodes of Ranvier may play a role in conduction block and disability which responds to immunotherapy more rapidly than would be expected for demyelination or axonal damage per se. Clinical reports suggest that in some cases, the effects of each dose of IVIG may be transient, wearing-off before the next dose is due. These observations lead us to hypothesize that that therapeutic IgG acts by competing with pathologic autoantibodies and that individual patients may require different IgG levels for optimal therapeutic effects. Frequent IVIG dosing and weekly subcutaneous IgG have been tried as ways of continuously maintaining high serum IgG levels, resulting in stabilization of neuromuscular function in small case series. Frequent grip strength and disability measurements, performed by the patient at home and reported electronically, can be used to assess the extent and duration of responses to IgG doses. Individualization of IgG treatment regimens may optimize efficacy, minimize disability, and identify nonresponders.

Antibodies to contactin-1 in chronic inflammatory demyelinating polyneuropathy

OBJECTIVE

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a frequent autoimmune neuropathy with a heterogeneous clinical spectrum. Clinical and experimental evidence suggests that autoantibodies may be involved in its pathogenesis, but the target antigens are unknown. Axoglial junction proteins have been proposed as candidate antigens. We examined the reactivity of CIDP patients' sera against neuronal antigens and used immunoprecipitation for antigen unraveling.

METHODS

Primary cultures of hippocampal neurons were used to select patients' sera that showed robust reactivity with the cell surface of neurons. The identity of the antigens was established by immunoprecipitation and mass spectrometry, and subsequently confirmed with cell-based assays, immunohistochemistry with teased rat sciatic nerve, and immunoabsorption experiments.

RESULTS

Four of 46 sera from patients with CIDP reacted strongly against hippocampal neurons (8.6%) and paranodal structures on peripheral nerve. Two patients' sera precipitated contactin-1 (CNTN1), and 1 precipitated both CNTN1 and contactin-associated protein 1 (CASPR1). Reactivity against CNTN1 was confirmed in 2 cases, whereas the third reacted only when CNTN1 and CASPR1 were cotransfected. No other CIDP patient or any of the 104 controls with other neurological diseases tested positive. All 3 patients shared common clinical features, including advanced age, predominantly motor involvement, aggressive symptom onset, early axonal involvement, and poor response to intravenous immunoglobulin.

INTERPRETATION

Antibodies against the CNTN1/CASPR1 complex occur in a subset of patients with CIDP who share common clinical features. The finding of this biomarker may help to explain the symptoms of these patients and the heterogeneous response to therapy in CIDP.

Chronic inflammatory demyelinating polyradiculoneuropathy in a patient with systemic lupus erythematosus and good outcome with rituximab treatment

A patient with chronic inflammatory demyelinating polyradiculoneuropathy and systemic lupus erythematosus arising after rubella vaccination was initially treated with plasmapheresis, corticosteroids and intravenous immunoglobulins, with partial response. After shift to rituximab, most clinical symptoms improved markedly, emphasizing the possible role of this monoclonal antibody in conventional therapy-resistant cases.

Guillain-barré syndrome: modern theories of etiology

Guillain-Barré syndrome (GBS) is a classic failure of the immune system with a life-threatening attack upon a critical self-component. The active phase of the disease is short, concordant with the latency of a primary adaptive immune response. Triggers for GBS include infection and (rarely) vaccination; cross-reactivity between infectious and neural epitopes has been well demonstrated, particularly for Campylobacter jejuni and motor axonal forms of GBS in which non-protein gangliosides are antigenic. Most people are probably exposed to a GBS trigger, but only rarely does the disease develop. We propose that GBS illustrates competing determinants of the immune system's decision about whether to mount a response, and that in unlucky affected individuals, co-presentation of cross-reactive antigens with danger signals activating pattern-recognition receptors overcomes normal self-recognition such that a primary response is initiated that attacks the nerve. Then, in most cases of GBS, the response rapidly turns off, and second attacks rarely occur. This suggests active restoration of tolerance, and specific privileged site attributes of nerve and declining danger signals as the trigger wanes may contribute to this restoration. Standard immunosuppression has not been effective in GBS. We suggest this is because immune tolerance is already being restored by the time such therapies are initiated. This in turn suggests that improvements in GBS outcomes are likely to come from better protection of the nerve cells under attack while normal resumption of tolerance is permitted to proceed rather than exploring more aggressive immunosuppressive approaches.

Distribution of Th17 cells and Th1 cells in peripheral blood and cerebrospinal fluid in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated demyelinating disease of the peripheral nervous system. Th17 and Th1 cells contribute to the pathogenesis of most autoimmune diseases, but little is known about their distribution and reciprocal relationship in CIDP. In this study, we analyzed the distribution of Th17, Th1, and Th17/Th1 cells in the peripheral blood and cerebrospinal fluid (CSF). The results showed that the frequency of Th17 cells was significantly higher in the peripheral blood mononuclear cell (PBMCs) and CSF of active CIDP in comparison with remitting CIDP or to other non-inflammatory neurological diseases (ONDs), accompanied by similar findings for Th17/Th1 cells. Both active and remitting CIDP have higher percentage of Th1 cells in the CSF than OND. CSF protein levels positively correlated with the frequencies of Th17 cells either in the PBMCs or CSF of active CIDP, while there was no significant correlation with Th1 cells. In line with these observations, the levels of interleukin-17 (IL-17) in plasma and transcript factors retinoic acid receptor-related orphan receptor (ROR)γt expressed by PBMCs were significantly higher in the active CIDP than remitting CIDP or OND. In summary, our preliminary findings suggest that elevated numbers of inflammatory T cells, especially for Th17 cells, might be an important determinant in the evolution of CIDP.

Circulating subsets and CD4(+)CD25(+) regulatory T cell function in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an inflammatory disease of the peripheral nervous system that is probably autoimmune in origin. Different components of the adaptive and innate immunity may be responsible for the aberrant response towards nerve antigens. To investigate this, we examined lymphocyte subsets and regulatory T cell (Treg) function in the blood of CIDP patients, healthy controls (HC) and subjects with non-immune mediated neuropathies (other neuropathies, ON). We used flow cytometry to determine the frequency of monocytes, B cells, natural killer (NK) and NK-T cells, total and activated CD4(+) and CD8(+) T cells, effector memory and central memory CD4(+) and CD8(+) T cells, and CD4(+)CD25(high)Foxp3(+) Tregs. Treg function was studied after polyclonal stimulation and antigen specific stimulation with myelin protein peptides in CIDP and HC. There was an increased frequency of monocytes (p = 0.02) and decreased frequency of NK cells (p = 0.02) in CIDP compared with HC but not ON. There were no significant differences in other populations. Treg function was impaired in CIDP compared to HC (p = 0.02), whilst T cell proliferation to myelin protein peptides before and after depletion of Tregs was not different between patients and controls. This study shows increased circulating monocytes and reduced NK cells in CIDP. Although Treg frequency was not altered, we confirm that Tregs display a defect of suppressive function. Myelin protein peptides were not the target of the altered peripheral regulation of the immune response. The mechanisms of peripheral immune tolerance in CIDP and their relevance to the pathogenesis deserve further exploration.

Myelin basic protein and myelin protein 2 act synergistically to cause stacking of lipid bilayers

Saltatory conduction of nerve impulses along axonal membranes depends on the presence of a multilayered membrane, myelin, that wraps around the axon. Myelin basic protein (MBP) and myelin protein 2 (P2) are intimately involved in the generation of the myelin sheath. They are also implicated in a number of neurological diseases, including autoimmune diseases of both the central and peripheral nervous systems. Here, we have used atomic force microsopy (AFM) to study the effects of MBP and P2 on lipid bilayers. MBP in association with a mica substrate appeared unstructured, and tended to coat the mica surface in the form of a monolayer. In contrast, P2 appeared as discrete particles, with molecular volumes consistent with the formation of both monomers and dimers. Either MBP or P2, at micromolar concentrations, caused stacking of brain lipid bilayers. This stacking effect was significantly potentiated when both proteins were added together. Bilayers composed of phosphatidylcholine (PC) and phosphatidylserine (PS) were stacked by MBP, provided that cholesterol was also present; in contrast, P2 did not stack PC/PS/cholesterol bilayers. Hence, the bilayer stacking effects of the two proteins have different lipid requirements.

Structural and functional characterization of human peripheral nervous system myelin protein P2

The myelin sheath is a tightly packed multilayered membrane structure insulating selected axons in the central and the peripheral nervous systems. Myelin is a biochemically unique membrane, containing a specific set of proteins. In this study, we expressed and purified recombinant human myelin P2 protein and determined its crystal structure to a resolution of 1.85 A. A fatty acid molecule, modeled as palmitate based on the electron density, was bound inside the barrel-shaped protein. Solution studies using synchrotron radiation indicate that the crystal structure is similar to the structure of the protein in solution. Docking experiments using the high-resolution crystal structure identified cholesterol, one of the most abundant lipids in myelin, as a possible ligand for P2, a hypothesis that was proven by fluorescence spectroscopy. In addition, electrostatic potential surface calculations supported a structural role for P2 inside the myelin membrane. The potential membrane-binding properties of P2 and a peptide derived from its N terminus were studied. Our results provide an enhanced view into the structure and function of the P2 protein from human myelin, which is able to bind both monomeric lipids inside its cavity and membrane surfaces.

Acute paretic syndrome in juvenile White Leghorn chickens resembles late stages of acute inflammatory demyelinating polyneuropathies in humans

BACKGROUND

Sudden limb paresis is a common problem in White Leghorn flocks, affecting about 1% of the chicken population before achievement of sexual maturity. Previously, a similar clinical syndrome has been reported as being caused by inflammatory demyelination of peripheral nerve fibres. Here, we investigated in detail the immunopathology of this paretic syndrome and its possible resemblance to human neuropathies.

METHODS

Neurologically affected chickens and control animals from one single flock underwent clinical and neuropathological examination. Peripheral nervous system (PNS) alterations were characterised using standard morphological techniques, including nerve fibre teasing and transmission electron microscopy. Infiltrating cells were phenotyped immunohistologically and quantified by flow cytometry. The cytokine expression pattern was assessed by quantitative real-time PCR (qRT-PCR). These investigations were accomplished by MHC genotyping and a PCR screen for Marek's disease virus (MDV).

RESULTS

Spontaneous paresis of White Leghorns is caused by cell-mediated, inflammatory demyelination affecting multiple cranial and spinal nerves and nerve roots with a proximodistal tapering. Clinical manifestation coincides with the employment of humoral immune mechanisms, enrolling plasma cell recruitment, deposition of myelin-bound IgG and antibody-dependent macrophageal myelin-stripping. Disease development was significantly linked to a 539 bp microsatellite in MHC locus LEI0258. An aetiological role for MDV was excluded.

CONCLUSIONS

The paretic phase of avian inflammatory demyelinating polyradiculoneuritis immunobiologically resembles the late-acute disease stages of human acute inflammatory demyelinating polyneuropathy, and is characterised by a Th1-to-Th2 shift.

T cells from patients with Guillain-Barré syndrome produce interferon-gamma in response to stimulation with the ganglioside GM1

Guillain-Barré syndrome (GBS) is an acquired demyelinating neuropathy, characterized by infiltration of peripheral nerves with macrophages and T cells. There have been reports of antibodies to glycolipids in GBS. We have previously found T cell reactivity to glycolipids in patients with the demyelinating form of GBS. This study was performed to characterize the cytokines produced by these T cells. Peripheral blood lymphocytes from patients with GBS, chronic inflammatory demyelinating polyradiculoneuropathy, healthy control patients and other neuropathies were incubated with the ganglioside GM1 and transferred to enzyme-linked immunospot plates. The average number per well of spot-forming cells (SFC) in the absence of antigen was counted. The average spontaneous SFC number was subtracted from the average SFC number in the presence of GM1, to produce a corrected SFC. There was significantly increased production of interferon-gamma but not interleukin-5 in response to stimulation with the ganglioside GM1. This could indicate that SFC have a role in pathogenesis of disease.

The effect of 2,5-hexanedione on permeability of blood-nerve barrier in rats

To explore the effect of 2,5-hexanedione on permeability of blood-nerve barrier, adult Wistar rats were administered with 400 mg x kg(-1) x d(- 1) 2,5-hexanedione to establish animal model of 2,5-hexnedione neuropathy. Evans blue was injected through left femoral vein of the rats after the model had been established. The distribution of fluorescence in sciatic-tibial nerve was observed and assessed. For the transverse sections of sciatic-tibial nerves, the average fluorescence intensity of proximal section was stronger (p < .01) than those of intermediate and distal sections and the average fluorescence intensity of intermediate section was stronger (p < .01) than that of distal section in the intoxicated group. In the control, the weak fluorescence was shown, and average fluorescence intensity of distal section was stronger (p < .05) than that of proximal section. The average fluorescence intensity of proximal, intermediate and distal sections in the intoxicated group was stronger (p < .01) than those of the corresponding sections in the control. For the longitudinal sections of sciatic-tibial nerves, fluorescence was observed in both proximal and distal sections in the intoxicated group. The fluorescence intensity of distal section in the control was weak and almost no fluorescence was shown in the proximal section. The permeability of blood-nerve barrier could be increased by 2,5-hexanedione.