Immunohistochemical localization of cytokines, C5b-9 and ICAM-1 in peripheral nerve of Guillain-Barré syndrome

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.

Development of a major histocompatibility complex class II conditional knockout mouse to study cell-specific and time-dependent adaptive immune responses in peripheral nerves

INTRODUCTION/AIMS

The precise relationship between molecular mimicry and tissue-specific autoimmunity is unknown. Major histocompatibility complex (MHC) class II antigen presenting cell-CD4+ T-cell receptor complex interactions are necessary for adaptive immunity. This study aimed to determine the role of endoneurial endothelial cell MHC class II in autoimmune polyneuropathy.

METHODS

Cryopreserved Guillain-Barré syndrome (GBS) patient sural nerve biopsies and sciatic nerves from the severe murine experimental autoimmune neuritis (sm-EAN) GBS model were studied. Cultured conditional ready MHC Class II antigen A-alpha chain (H2-Aa) embryonic stem cells were used to generate H2-Aaflox/+ C57BL/6 mice. Mice were backcrossed and intercrossed to the SJL background to generate H2-Aaflox/flox SJL mice, bred with hemizygous Tamoxifen-inducible von Willebrand factor Cre recombinase (vWF-iCre/+) SJL mice to generate H2-Aaflox/flox; vWF-iCre/+ mice to study microvascular endothelial cell adaptive immune responses. Sm-EAN was induced in Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+, H2-Aaflox/flox; +/+, H2-Aa+/+; vWF-iCre/+ and untreated H2-Aaflox/flox; vWF-iCre/+ adult female SJL mice. Neurobehavioral, electrophysiological and histopathological assessments were performed at predefined time points.

RESULTS

Endoneurial endothelial cell MHC class II expression was observed in normal and inflamed human and mouse peripheral nerves. Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+ mice were resistant to sm-EAN despite extensive MHC class II expression in lymphoid and non-lymphoid tissues.

DISCUSSION

A conditional MHC class II knockout mouse to study cell- and time-dependent adaptive immune responses in vivo was developed. Initial studies show microvascular endothelial cell MHC class II expression is necessary for peripheral nerve specific autoimmunity, as advocated by human in vitro adaptive immunity and ex vivo transplant rejection studies.

Engineering Neurotoxin-Functionalized Exosomes for Targeted Delivery to the Peripheral Nervous System

The administration of therapeutics to peripheral nerve tissue is challenging due to the complexities of peripheral neuroanatomy and the limitations imposed by the blood-nerve barrier (BNB). Therefore, there is a pressing need to enhance delivery effectiveness and implement targeted delivery methods. Recently, erythrocyte-derived exosomes (Exos) have gained widespread attention as biocompatible vehicles for therapeutics in clinical applications. However, engineering targeted Exos for the peripheral nervous system (PNS) is still challenging. This study aims to develop a targeted Exo delivery system specifically designed for presynaptic terminals of peripheral nerve tissue. The clostridium neurotoxin, tetanus toxin-C fragment (TTC), was tethered to the surface of red blood cell (RBC)-derived Exos via a facile and efficient bio-orthogonal click chemistry method without a catalyst. Additionally, Cyanine5 (Cy5), a reactive fluorescent tag, was also conjugated to track Exo movement in both in vitro and in vivo models. Subsequently, Neuro-2a, a mouse neuronal cell line, was treated with dye-labeled Exos with/without TTC in vitro, and the results indicated that TTC-Exos exhibited more efficient accumulation along the soma and axonal circumference, compared to their unmodified counterparts. Further investigation, using a mouse model, revealed that within 72 h of intramuscular administration, engineered TTC-Exos were successfully transported into the neuromuscular junction and sciatic nerve tissues. These results indicated that TTC played a crucial role in the Exo delivery system, improving the affinity to peripheral nerves. These promising results underscore the potential of using targeted Exo carriers to deliver therapeutics for treating peripheral neuropathies.

Evaluation of the retinal nerve fiber layer and choroidal thickness with optical coherence tomography in patients with psoriasis

BACKGROUND

To evaluate the retinal nerve fiber layer (RNFL), central retinal thickness (CRT), and choroidal thickness (CT) in patients with psoriasis.

METHODS

The study included 43 patients diagnosed with psoriasis not receiving systemic treatment and 41 healthy volunteers. Spectral domain optical coherence tomography was used for retinal and choroidal thickness measurements. The mean RNFL, quadrant RNFL (superior, inferior, nasal, temporal), and CRT values were recorded. The choroidal thickness measurements were taken from the subfoveal area, towards the temporal and nasal directions from the fovea at distances of 500, 1000, and 1500 µm.

RESULTS

The RNFL was determined to be thinner in the superior quadrant (p=0.025), and the CT was thicker at all the measurement points (p < 0.05) in the patients with psoriasis. The CRT values were similar in both groups (p > 0.05). No correlation was determined between the parameters measured and disease duration or severity.

CONCLUSIONS

Thinning of the RNFL and increased CT may be a sign of choroidal microvascular changes and ganglion cell damage due to psoriasis.

Development of a major histocompatibility complex class II conditional knockout mouse to study cell-specific and time-dependent adaptive immune responses in peripheral nerves

Introduction

Major histocompatibility complex (MHC) class II professional antigen presenting cell-naïve CD4+ T cell interactions via the T-cell receptor complex are necessary for adaptive immunity. MHC class II upregulation in multiple cell types occurs in human autoimmune polyneuropathy patient biopsies, necessitating studies to ascertain cellular signaling pathways required for tissue-specific autoimmunity.

Methods

Cryopreserved Guillain-Barré syndrome (GBS) patient sural nerve biopsies and sciatic nerves from the severe murine experimental autoimmune neuritis (sm-EAN) GBS model were studied. Cultured conditional ready MHC Class II antigen A-alpha chain (H2-Aa) embryonic stem cells were used to generate H2-Aa flox/+ C57BL/6 mice. Mice were backcrossed and intercrossed to the SJL background to generate H2-Aa flox/flox SJL mice, bred with hemizygous Tamoxifen-inducible von Willebrand factor Cre recombinase (vWF-iCre/+) SJL mice to generate H2-Aa flox/flox ; vWF-iCre/+ to study microvascular endothelial cell adaptive immune responses. Sm-EAN was induced in adult female SJL Tamoxifen-treated H2-Aa flox/flox ; vWF-iCre/+ mice and H2-Aa flox/flox ; +/+ littermate controls. Neurobehavioral, electrophysiological and histopathological assessments were performed at predefined time points.

Results

Endoneurial endothelial cell MHC class II expression was observed in normal and inflamed human and mouse peripheral nerves. Adult female Tamoxifen-treated H2-Aa flox/flox ; vWF-iCre/+ did not develop sm-EAN despite extensive MHC class II expression in lymphoid and non-lymphoid tissues.

Discussion

A conditional MHC class II knockout mouse to study cell- and time-dependent adaptive immune responses in vivo is developed. Initial studies show microvascular endothelial cell MHC class II expression is necessary for peripheral nerve specific autoimmunity, as advocated by human in vitro adaptive immunity and ex vivo transplant rejection studies.

Immune-Mediated Neuropathies: Pathophysiology and Management

Dysfunction of the immune system can result in damage of the peripheral nervous system. The immunological mechanisms, which include macrophage infiltration, inflammation and proliferation of Schwann cells, result in variable degrees of demyelination and axonal degeneration. Aetiology is diverse and, in some cases, may be precipitated by infection. Various animal models have contributed and helped to elucidate the pathophysiological mechanisms in acute and chronic inflammatory polyradiculoneuropathies (Guillain-Barre Syndrome and chronic inflammatory demyelinating polyradiculoneuropathy, respectively). The presence of specific anti-glycoconjugate antibodies indicates an underlying process of molecular mimicry and sometimes assists in the classification of these disorders, which often merely supports the clinical diagnosis. Now, the electrophysiological presence of conduction blocks is another important factor in characterizing another subgroup of treatable motor neuropathies (multifocal motor neuropathy with conduction block), which is distinct from Lewis-Sumner syndrome (multifocal acquired demyelinating sensory and motor neuropathy) in its response to treatment modalities as well as electrophysiological features. Furthermore, paraneoplastic neuropathies are also immune-mediated and are the result of an immune reaction to tumour cells that express onconeural antigens and mimic molecules expressed on the surface of neurons. The detection of specific paraneoplastic antibodies often assists the clinician in the investigation of an underlying, sometimes specific, malignancy. This review aims to discuss the immunological and pathophysiological mechanisms that are thought to be crucial in the aetiology of dysimmune neuropathies as well as their individual electrophysiological characteristics, their laboratory features and existing treatment options. Here, we aim to present a balance of discussion from these diverse angles that may be helpful in categorizing disease and establishing prognosis.

Pro-inflammatory cytokines and leukocyte integrins associated with chronic neuropathic pain in traumatic and inflammatory neuropathies: Initial observations and hypotheses

Leukocyte infiltration and persistence within peripheral nerves have been implicated in chronic nociception pathogenesis in murine peripheral neuropathy models. Endoneurial cytokine and chemokine expression contribute to leukocyte infiltration and maintenance of a pro-inflammatory state that delays peripheral nerve recovery and promotes chronic pain behaviors in these mice. However, there has been a failure to translate murine model data into safe and effective treatments for chronic neuropathic pain in peripheral neuropathy patients, or develop reliable biomarkers that may help diagnose or determine treatment responses in affected patients. Initial work showed that persistent sciatic nerve CD11b+ CD45+ leukocyte infiltration was associated with disease severity in three mouse models of inflammatory and traumatic peripheral neuropathies, implying a direct contributing role in disease pathogenesis. In support of this, CD11b+ leukocytes were also seen in the sural nerve biopsies of chronic neuropathic pain patients with three different peripheral neuropathies. Systemic CD11b antagonism using a validated function-neutralizing monoclonal antibody effectively treated chronic nociception following unilateral sciatic nerve crush injury (a representative traumatic neuropathy model associated with axonal degeneration and increased blood-nerve barrier permeability) and does not cause drug addiction behaviors in adult mice. These data suggest that CD11b could be an effective molecular target for chronic neuropathic pain treatment in inflammatory and traumatic peripheral neuropathies. Despite known murine peripheral neuropathy model limitations, our initial work suggests that early expression of pro-inflammatory cytokines, such as tissue inhibitor of metalloproteinases-1 may predict subsequent chronic nociception development following unilateral sciatic nerve crush injury. Studies aligning animal model investigation with observational data from well-characterized human peripheral neuropathies, including transcriptomics and proteomics, as well as animal model studies using a human clinical trial design should foster the identification of clinically relevant biomarkers and effective targeted treatments with limited addiction potential for chronic neuropathic pain in peripheral neuropathy patients.

Association of mannose-binding lectin 2 gene polymorphisms with Guillain-Barré syndrome

Complement activation plays a critical role in the pathogenesis of Guillain-Barré syndrome (GBS), a debilitating immune-mediated neuropathy. Mannose-binding lectin (MBL) is a complement activation factor of lectin pathway which as genetic host factor may influence the susceptibility or severity of GBS. We investigated the frequency of MBL2 promoter (- 550H/L and - 221X/Y) and functional region (exon 1 A/O) polymorphisms and their association with disease susceptibility, clinical features and serum MBL among GBS patients (n = 300) and healthy controls (n = 300) in Bangladesh. The median patient age was 30 years (IQR: 18-42; males, 68%). MBL2 polymorphisms were not significantly associated with GBS susceptibility compared to healthy controls. HL heterozygosity in GBS patients was significantly associated with mild functional disability at enrolment (P = 0.0145, OR, 95% CI 2.1, 1.17-3.82). The HY, YA, HA and HYA heterozygous haplotypes were more common among mildly affected (P = 0.0067, P = 0.0086, P = 0.0075, P = 0.0032, respectively) than severely affected patients with GBS. Reduced serum MBL was significantly associated with the LL, OO and no HYA variants and GBS disease severity. No significant association was observed between MBL2 polymorphisms and electrophysiological variants, recent Campylobacter jejuni infection or anti-ganglioside (GM1) antibody responses in GBS. In conclusion, MBL2 gene polymorphisms are related to reduced serum MBL and associated with the severity of GBS.

Retinal nerve fibre layer thickness and choroidal thickness: An evaluation in psoriasis patients

BACKGROUND/OBJECTIVES

To conduct a comparative study of retinal nerve fibre layer (RNFL) thickness and choroidal thickness of psoriasis patients and healthy volunteers.

METHODS

This study included 35 severe psoriasis patients, 35 mild psoriasis patients and 35 healthy individuals. RNFL and choroidal thickness analysis were performed by spectral field optical coherence tomography (SD-OCT). Only patients with psoriasis vulgaris who have not used systemic therapy for the last 3 months were included in the study.

RESULTS

In the severe psoriasis group, the RSLT thickness was found to be statistically significantly thinner and the choroid thickness was thicker than the mild psoriasis and control group (P < .001). There was no significant difference in terms of RNLF and choroid thickness compared to mild psoriasis and the control group (P > .05). The correlation between length of the disease duration, RNFL and choroidal thickness was not significant (P > 0,05).

CONCLUSION

The increase in choroidal thickness was found to be significant, while with respect to RNFL thickness, a decrease was evident, a possible indicator of damage to microvascular structures in the choroid and ganglion cells, especially in patients with severe psoriasis. Therefore, choroidal and RSLT thickness measurement with OCT device can assist in the detection of damage to psoriasis.

New evidence for secondary axonal degeneration in demyelinating neuropathies

Development of peripheral nervous system (PNS) myelin involves a coordinated series of events between growing axons and the Schwann cell (SC) progenitors that will eventually ensheath them. Myelin sheaths have evolved out of necessity to maintain rapid impulse propagation while accounting for body space constraints. However, myelinating SCs perform additional critical functions that are required to preserve axonal integrity including mitigating energy consumption by establishing the nodal architecture, regulating axon caliber by organizing axonal cytoskeleton networks, providing trophic and potentially metabolic support, possibly supplying genetic translation materials and protecting axons from toxic insults. The intermediate steps between the loss of these functions and the initiation of axon degeneration are unknown but the importance of these processes provides insightful clues. Prevalent demyelinating diseases of the PNS include the inherited neuropathies Charcot-Marie-Tooth Disease, Type 1 (CMT1) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) and the inflammatory diseases Acute Inflammatory Demyelinating Polyneuropathy (AIDP) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). Secondary axon degeneration is a common feature of demyelinating neuropathies and this process is often correlated with clinical deficits and long-lasting disability in patients. There is abundant electrophysiological and histological evidence for secondary axon degeneration in patients and rodent models of PNS demyelinating diseases. Fully understanding the involvement of secondary axon degeneration in these diseases is essential for expanding our knowledge of disease pathogenesis and prognosis, which will be essential for developing novel therapeutic strategies.

Biology of the human blood-nerve barrier in health and disease

A highly regulated endoneurial microenvironment is required for normal axonal function in peripheral nerves and nerve roots, which structurally consist of an outer collagenous epineurium, inner perineurium consisting of multiple concentric layers of specialized epithelioid myofibroblasts that surround the innermost endoneurium, which consists of myelinated and unmyelinated axons embedded in a looser mesh of collagen fibers. Endoneurial homeostasis is achieved by tight junction-forming endoneurial microvessels that control ion, solute, water, nutrient, macromolecule and leukocyte influx and efflux between the bloodstream and endoneurium, and the innermost layers of the perineurium that control interstitial fluid component flux between the freely permeable epineurium and endoneurium. Strictly speaking, endoneurial microvascular endothelium should be considered the blood-nerve barrier (BNB) due to direct communication with circulating blood. The mammalian BNB is considered the second most restrictive vascular system after the blood-brain barrier (BBB) based on classic in situ permeability studies. Structural alterations in endoneurial microvessels or interactions with hematogenous leukocytes have been described in several human peripheral neuropathies; however major advances in BNB biology in health and disease have been limited over the past 50 years. Guided by transcriptome and proteome studies of normal and pathologic human peripheral nerves, purified primary and immortalized human endoneurial endothelial cells that form the BNB and leukocytes from patients with well-characterized peripheral neuropathies, validated by in situ or ex vivo protein expression studies, data are emerging on the molecular and functional characteristics of the human BNB in health and in specific peripheral neuropathies, as well as chronic neuropathic pain. These early advancements have the potential to not only increase our understanding of how the BNB works and adapts or fails to adapt to varying insult, but provide insights relevant to pathogenic leukocyte trafficking, with translational potential and specific therapeutic application for chronic peripheral neuropathies and neuropathic pain.

Strategies for Targeted Delivery to the Peripheral Nerve

Delivery of compounds to the peripheral nervous system has the potential to be used as a treatment for a broad range of conditions and applications, including neuropathic pain, regional anesthesia, traumatic nerve injury, and inherited and inflammatory neuropathies. However, efficient delivery of therapeutic doses can be difficult to achieve due to peripheral neuroanatomy and the restrictiveness of the blood-nerve barrier. Depending on the underlying integrity of the blood-nerve barrier in the application at hand, several strategies can be employed to navigate the peripheral nerve architecture and facilitate targeted delivery to the peripheral nerve. This review describes different applications where targeted delivery to the peripheral nervous system is desired, the challenges that the blood-nerve barrier poses in each application, and bioengineering strategies that can facilitate delivery in each application.

Autoinflammatory and autoimmune contributions to complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a highly enigmatic syndrome typically developing after injury or surgery to a limb. Severe pain and disability are common among those with chronic forms of this condition. Accumulating evidence suggests that CRPS may involve both autoinflammatory and autoimmune components. In this review article, evidence for dysfunction of both the innate and adaptive immune systems in CRPS is presented. Findings from human studies in which cytokines and other inflammatory mediators were measured in the skin of affected limbs are discussed. Additional results from studies of mediator levels in animal models are evaluated in this context. Similarly, the evidence from human, animal, and translational studies of the production of autoantibodies and the potential targets of those antibodies is reviewed. Compelling evidence of autoinflammation in skin and muscle of the affected limb has been collected from CRPS patients and laboratory animals. Cytokines including IL-1β, IL-6, TNFα, and others are reliably identified during the acute phases of the syndrome. More recently, autoimmune contributions have been suggested by the discovery of self-directed pain-promoting IgG and IgM antibodies in CRPS patients and model animals. Both the autoimmune and the autoinflammatory components of CRPS appear to be regulated by neuropeptide-containing peripheral nerve fibers and the sympathetic nervous system. While CRPS displays a complex neuroimmunological pathogenesis, therapeutic interventions could be designed targeting autoinflammation, autoimmunity, or the neural support for these phenomena.

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.

Comprehensive cytokine profiling provides evidence for a multi-lineage Th responses in Guillain Barré Syndrome

Guillain Barré Syndrome (GBS) is one of the commonest acquired immune-mediated neuropathies, often preceded by infections. Although cellular immune responses are shown to substantially account for the pathophysiology of GBS, the precise mechanistic basis of risk and disease course remains enigmatic till date. Cytokines are best known for their abilities to drive cellular immunity and inflammation through their co-ordinated actions. Data obtained from clinical and animal model studies suggest important implications of some of the cytokines in the progression and recovery of GBS. However, these studies were performed on few cytokines and small set of GBS patients, thereby lacking a complete understanding of the patterns of association of cytokines representing Th1, Th2, and Th17 responses with GBS. We studied 65 well-characterized GBS patients and 73 age- and sex-matched healthy controls. A panel of 15 cytokines representing Th1, Th2 and Th17 pathways was assayed using Multiplex Suspension Array platform. Plasma levels of five cytokines were found to be altered in GBS patients compared to healthy control subjects: (i) IL-1β exhibited reduced levels, and (ii) IFN-γ, IL-4, IL-21 and IL-33 were elevated in GBS patients. The most important finding of this study was up-regulated expression of IL-21 and IL-33 in patients with GBS. Given the role of IL-33 as an alarmin, the elevated level of this cytokine provides important indication about a much broader role of cytokines in GBS. This study also provides evidence towards a multi-lineage Th cells (Th1, Th2 and Th17) associated cytokine responses in the pathophysiology of GBS.

Zika virus infection elicits auto-antibodies to C1q

Zika virus (ZIKV) causes mostly asymptomatic infection or mild febrile illness. However, with an increasing number of patients, various clinical features such as microcephaly, Guillain-Barré syndrome and thrombocytopenia have also been reported. To determine which host factors are related to pathogenesis, the E protein of ZIKV was analyzed with the Informational Spectrum Method, which identifies common information encoded by primary structures of the virus and the respective host protein. The data showed that the ZIKV E protein and the complement component C1q cross-spectra are characterized by a single dominant peak at the frequency F = 0.338, suggesting similar biological properties. Indeed, C1q-specific antibodies were detected in sera obtained from mice and monkeys infected with ZIKV. As C1q has been known to be involved not only in immunity, but also in synaptic organization and different autoimmune diseases, a ZIKV-induced anti-C1q antibody response may contribute to the neurological complications. These findings might also be exploited for the design of safe and efficacious vaccines in the future.

The pathogenic relevance of αM-integrin in Guillain-Barré syndrome

The molecular determinants and mechanisms involved in leukocyte trafficking across the blood-nerve barrier (BNB) in the acute inflammatory demyelinating polyradiculoneuropathy (AIDP) variant of Guillain-Barré syndrome are incompletely understood. Prior work using a flow-dependent in vitro human BNB model demonstrated a crucial role for α_M-integrin (CD11b)-intercellular adhesion molecule-1 interactions in AIDP patient leukocyte trafficking. The aim of this study is to directly investigate the biological relevance of CD11b in AIDP pathogenesis. Immunohistochemistry was performed on three AIDP patient sural nerve biopsies to evaluate endoneurial leukocyte CD11b expression. A severe murine experimental autoimmune neuritis (sm-EAN) model was utilized to determine the functional role of CD11b in leukocyte trafficking in vivo and determine its effect on neurobehavioral measures of disease severity, electrophysiological assessments of axonal integrity and myelination and histopathological measures of peripheral nerve inflammatory demyelination. Time-lapse video microscopy and electron microscopy were employed to observe structural alterations at the BNB during AIDP patient leukocyte trafficking in vitro and in situ, respectively. Large clusters of endoneurial CD11b+ leukocytes associated with demyelinating axons were observed in AIDP patient sural nerves. Leukocyte CD11b expression was upregulated during sm-EAN. 5 mg/kg of a function-neutralizing monoclonal rat anti-mouse CD11b antibody administered after sm-EAN disease onset significantly ameliorated disease severity, as well as electrophysiological and histopathological parameters of inflammatory demyelination compared to vehicle- and isotype antibody-treated mice. Consistent with in vitro observations of leukocyte trafficking at the BNB, electron micrographs of AIDP patient sural nerves demonstrated intact electron-dense endoneurial microvascular intercellular junctions during paracellular mononuclear leukocyte transmigration. Our data support a crucial pathogenic role of CD11b in AIDP leukocyte trafficking, providing a potential therapeutic target for demyelinating variants of Guillain-Barré syndrome.

Evaluation of Macular Ganglion Cell-inner Plexiform Layer and Choroid in Psoriasis Patients Using Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography

PURPOSE

To evaluate changes in the thickness of the central macula, macular ganglion cell-inner plexiform layer (mGCIPL), and subfoveal choroid in patients with psoriasis using spectral domain optical coherence tomography (SD-OCT).

METHODS

The measurements of macular, mGCIPL thicknesses and subfoveal choroidal thickness (SFCT) obtained by SD-OCT of psoriasis patients (n = 46). These measurements were compared with those of 50 healthy controls.

RESULTS

The macular, mGCIPL, and choroidal thicknesses did not differ between the controls and psoriatic subjects (p>0.05). When the patients were divided into two distinct groups, only the SFCT was significantly thicker in the severe psoriasis group compared with the mild psoriasis group (p = 0.003).

CONCLUSIONS

These findings suggest that choroidal alterations are seen without macular changes in patients with psoriasis. Severe psoriasis appears to be related to increases in SFCT as a consequence of possible inflammatory cascades that are part of the disease's pathogenesis.

C1q-targeted inhibition of the classical complement pathway prevents injury in a novel mouse model of acute motor axonal neuropathy

Introduction

Guillain-Barré syndrome (GBS) is an autoimmune disease that results in acute paralysis through inflammatory attack on peripheral nerves, and currently has limited, non-specific treatment options. The pathogenesis of the acute motor axonal neuropathy (AMAN) variant is mediated by complement-fixing anti-ganglioside antibodies that directly bind and injure the axon at sites of vulnerability such as nodes of Ranvier and nerve terminals. Consequently, the complement cascade is an attractive target to reduce disease severity. Recently, C5 complement component inhibitors that block the formation of the membrane attack complex and subsequent downstream injury have been shown to be efficacious in an in vivo anti-GQ1b antibody-mediated mouse model of the GBS variant Miller Fisher syndrome (MFS). However, since gangliosides are widely expressed in neurons and glial cells, injury in this model was not targeted exclusively to the axon and there are currently no pure mouse models for AMAN. Additionally, C5 inhibition does not prevent the production of early complement fragments such as C3a and C3b that can be deleterious via their known role in immune cell and macrophage recruitment to sites of neuronal damage.

Results and Conclusions

In this study, we first developed a new in vivo transgenic mouse model of AMAN using mice that express complex gangliosides exclusively in neurons, thereby enabling specific targeting of axons with anti-ganglioside antibodies. Secondly, we have evaluated the efficacy of a novel anti-C1q antibody (M1) that blocks initiation of the classical complement cascade, in both the newly developed anti-GM1 antibody-mediated AMAN model and our established MFS model in vivo. Anti-C1q monoclonal antibody treatment attenuated complement cascade activation and deposition, reduced immune cell recruitment and axonal injury, in both mouse models of GBS, along with improvement in respiratory function. These results demonstrate that neutralising C1q function attenuates injury with a consequent neuroprotective effect in acute GBS models and promises to be a useful new target for human therapy.

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.

Differential gene expression of cytokines and neurotrophic factors in nerve and skin of patients with peripheral neuropathies

Pathophysiologically relevant alterations in cytokine and neurotrophic factor levels have been reported in neuropathy subtypes. We characterized gene expression profiles of pro- and anti-inflammatory cytokines and neurotrophic factors in nerve and skin samples of patients with neuropathies of different etiologies. We prospectively studied 133 patients with neuropathies and compared data between subtypes and with healthy controls. All patients underwent sural nerve and/or skin punch biopsy at the lateral thigh and lower leg; controls received skin punch biopsies. Gene expression of pro- and anti-inflammatory cytokines (IL-1β, IL-2, IL-6, TNF, IL-10), neurotrophic factors (BDNF, NGF, NT3, TrkA), and erythropoietin with the erythropoietin receptor (Epo, EpoR) was analyzed. Sural nerve gene expression of the investigated cytokines and neurotrophic factors did not differ between neuropathies of different etiologies; however, IL-6 (p < 0.01) and IL-10 (p < 0.05) expression was higher in painful compared to painless neuropathies. Skin IL-6 and IL-10 gene expression was increased in patients compared to controls (p < 0.05), and IL-10 expression was higher in lower leg skin of patients with non-inflammatory neuropathies compared to inflammatory neuropathies (p < 0.05). Proximal and distal skin neurotrophic factor and Epo gene expression of patients with neuropathies was reduced compared to controls (NGF, NT3, Epo; p < 0.05). Neuropathies are associated with an increase in cytokine expression and a decrease in neurotrophic factor expression including nerve and skin.

Circulating Th17, Th22, and Th1 cells are elevated in the Guillain-Barré syndrome and downregulated by IVIg treatments

The Guillain-Barré syndrome (GBS) is considered a T helper 1 (Th1) cells-mediated acute inflammatory peripheral neuropathy. However, some changes in GBS could not be explained completely by Th1 cells pathogenic role. Recently, Th17 cells have been identified and can mediate tissue inflammation and autoimmune response. Therefore, a study on the role of Th17 and Th22 cells and their cytokines in GBS is necessary for exploring the pathogenesis of GBS. Here, we detected the frequency of Th1, Th17, and Th22 cells by using 4-color flow cytometry and we detected the plasma levels of IL-17 and IL-22 by ELISA in GBS patients, relapsing-remitting multiple sclerosis patients at the acute phase of relapse, viral encephalitis or meningitis patients and healthy controls. Our data showed that the frequency of circulating Th1, Th17, and Th22 cells was significantly increased in GBS patients. The plasma levels of IL-17 and IL-22 in GBS and relapsing-remitting multiple sclerosis at the acute phase of relapse were also markedly elevated. Enhanced circulating Th22 cells were correlated with GBS severity. Intravenous immunoglobulin therapy downregulated Th17, and Th22 cells and the plasma levels of IL-17 and IL-22 in GBS patients. Th17 and Th22 cells may be involved in the pathogenesis of GBS, and intravenous immunoglobulin mediates therapeutic effects by downregulating these cells and their cytokines.

Molecules involved in the crosstalk between immune- and peripheral nerve Schwann cells

Schwann cells are the myelinating glial cells of the peripheral nervous system and establish myelin sheaths on large caliber axons in order to accelerate their electrical signal propagation. Apart from this well described function, these cells revealed to exhibit a high degree of differentiation plasticity as they were shown to re- and dedifferentiate upon injury and disease as well as to actively participate in regenerative- and inflammatory processes. This review focuses on the crosstalk between glial- and immune cells observed in many peripheral nerve pathologies and summarizes functional evidences of molecules, regulators and factors involved in this process. We summarize data on Schwann cell's role presenting antigens, on interactions with the complement system, on Schwann cell surface molecules/receptors and on secreted factors involved in immune cell interactions or para-/autocrine signaling events, thus strengthening the view for a broader (patho) physiological role of this cell lineage.

Cdc42 GTPases facilitate TNF-α-mediated secretion of CCL2 from peripheral nerve microvascular endoneurial endothelial cells

Trafficking of autoreactive leukocytes across the blood-nerve barrier and into peripheral nerves is an early pathological hallmark of Guillain-Barré syndrome (GBS). Tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, promotes transendothelial migration by upregulating endothelial expression of inflammatory mediators, including CCL2, a chemokine implicated in GBS. We sought to determine the mechanism by which TNF-α induces expression and secretion of CCL2 from peripheral nerve microvascular endoneurial endothelial cells (PNMECs). Expression of CCL2 mRNA and protein in quiescent PNMEC cultures was minimal. In contrast, cultures treated with TNF-α exhibited increased CCL2 mRNA and protein content, as well as protein secretion. Simvastatin significantly attenuated TNF-α-induced CCL2 secretion without affecting CCL2 mRNA or protein expression. Co-incubation with geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, prevented the effect of simvastatin. By comparison, inhibiting protein isoprenylation with GGTI-298, but not FTI-277, mimicked the effect of simvastatin and significantly attenuated transendothelial migration in vitro. Inhibition of the monomeric GTPase Cdc42, but not Rac1 or RhoA-C, attenuated TNF-α-mediated CCL2 secretion. TNF-α-mediated trafficking of autoreactive leukocytes into peripheral nerves during GBS may proceed by a mechanism that involves Cdc42-facilitated secretion of CCL2.

Anti-GM2 ganglioside antibodies are a biomarker for acute canine polyradiculoneuritis

Acute canine polyradiculoneuritis (ACP) is considered to be the canine equivalent of the human peripheral nerve disorder Guillain-Barré syndrome (GBS); an aetiological relationship, however, remains to be demonstrated. In GBS, anti-glycolipid antibodies (Abs) are considered as important disease mediators. To address the possibility of common Ab biomarkers, the sera of 25 ACP dogs, 19 non-neurological, and 15 epileptic control dogs were screened for IgG Abs to 10 glycolipids and their 1 : 1 heteromeric complexes using combinatorial glycoarrays. Anti-GM2 ganglioside Abs were detected in 14/25 ACP dogs, and anti-GA1 Abs in one further dog. All controls except for one were negative for anti-glycolipid Abs. In this cohort of cases and controls, the glycoarray screen reached a diagnostic sensitivity of 60% and a specificity of 97%; a lower sensitivity (32%) was reported using a conventional glycolipid ELISA. To address the possible pathogenic role for anti-GM2 Abs in ACP, we identified GM2 in canine sciatic nerve by both mass spectrometry and thin layer chromatography overlay. In immunohistological studies, GM2 was localized predominantly to the abaxonal Schwann cell membrane. The presence of anti-GM2 Abs in ACP suggests that it may share a similar pathophysiology with GBS, for which it could thus be considered a naturally occurring animal model.

Tumour necrosis factor α enhances CCL2 and ICAM-1 expression in peripheral nerve microvascular endoneurial endothelial cells

Recruitment and trafficking of autoreactive leucocytes across the BNB (blood-nerve barrier) is an early pathological insult in GBS (Guillain-Barré syndrome), an aggressive autoimmune disorder of the PNS (peripheral nervous system). Whereas the aetiology and pathogenesis of GBS remain unclear, pro-inflammatory cytokines, including TNFα (tumour necrosis factor α), are reported to be elevated early in the course of GBS and may initiate nerve injury by activating the BNB. Previously, we reported that disrupting leucocyte trafficking in vivo therapeutically attenuates the course of an established animal model of GBS. Here, PNMECs (peripheral nerve microvascular endothelial cells) that form the BNB were harvested from rat sciatic nerves, immortalized by SV40 (simian virus 40) large T antigen transduction and subsequently challenged with TNFα. Relative changes in CCL2 (chemokine ligand 2) and ICAM-1 (intercellular adhesion molecule 1) expression were determined. We report that TNFα elicits marked dose- and time-dependent increases in CCL2 and ICAM-1 mRNA and protein content and promotes secretion of functional CCL2 from immortalized and primary PNMEC cultures. TNFα-mediated secretion of CCL2 promotes, in vitro, the transendothelial migration of CCR2-expressing THP-1 monocytes. Increased CCL2 and ICAM-1 expression in response to TNFα may facilitate recruitment and trafficking of autoreactive leucocytes across the BNB in autoimmune disorders, including GBS.

α(M)β(2)-integrin-intercellular adhesion molecule-1 interactions drive the flow-dependent trafficking of Guillain-Barré syndrome patient derived mononuclear leukocytes at the blood-nerve barrier in vitro

The mechanisms of hematogenous leukocyte trafficking at the human blood-nerve barrier (BNB) are largely unknown. Intercellular adhesion molecule-1 (ICAM-1) has been implicated in the pathogenesis of Guillain-Barré syndrome (GBS). We developed a cytokine-activated human in vitro BNB model using primary endoneurial endothelial cells. Endothelial treatment with 10 U/ml tissue necrosis factor-α and 20 U/ml interferon-γ resulted in de novo expression of pro-inflammatory chemokines CCL2, CXCL9, CXCL11, and CCL20, with increased expression of CXCL2-3, CXCL8, and CXCL10 relative to basal levels. Cytokine treatment induced/enhanced ICAM-1, E- and P-selectin, vascular cell adhesion molecule-1 and the alternatively spliced pro-adhesive fibronectin variant, fibronectin connecting segment-1 expression in a time-dependent manner, without alterations in junctional adhesion molecule-A expression. Lymphocytes and monocytes from untreated GBS patients express ICAM-1 counterligands, α(M)- and α(L)-integrin, with differential regulation of α(M) -integrin expression compared to healthy controls. Under flow conditions that mimic capillary hemodynamics in vivo, there was a >3-fold increase in total GBS patient and healthy control mononuclear leukocyte adhesion/migration at the BNB following cytokine treatment relative to the untreated state. Function neutralizing monoclonal antibodies against human α(M)-integrin (CD11b) and ICAM-1 reduced untreated GBS patient mononuclear leukocyte trafficking at the BNB by 59% and 64.2%, respectively. Monoclonal antibodies against α(L)-integrin (CD11a) and human intravenous immunoglobulin reduced total leukocyte adhesion/migration by 22.8% and 17.6%, respectively. This study demonstrates differential regulation of α(M)-integrin on circulating mononuclear cells in GBS, as well as an important role for α(M)-integrin-ICAM-1 interactions in pathogenic GBS patient leukocyte trafficking at the human BNB in vitro.

Membrane attack by complement: the assembly and biology of terminal complement complexes

Complement system activation plays an important role in both innate and acquired immunity. Activation of the complement and the subsequent formation of C5b-9 channels (the membrane attack complex) on the cell membranes lead to cell death. However, when the number of channels assembled on the surface of nucleated cells is limited, sublytic C5b-9 can induce cell cycle progression by activating signal transduction pathways and transcription factors and inhibiting apoptosis. This induction by C5b-9 is dependent upon the activation of the phosphatidylinositol 3-kinase/Akt/FOXO1 and ERK1 pathways in a Gi protein-dependent manner. C5b-9 induces sequential activation of CDK4 and CDK2, enabling the G1/S-phase transition and cellular proliferation. In addition, it induces RGC-32, a novel gene that plays a role in cell cycle activation by interacting with Akt and the cyclin B1-CDC2 complex. C5b-9 also inhibits apoptosis by inducing the phosphorylation of Bad and blocking the activation of FLIP, caspase-8, and Bid cleavage. Thus, sublytic C5b-9 plays an important role in cell activation, proliferation, and differentiation, thereby contributing to the maintenance of cell and tissue homeostasis.

Translational strategies in peripheral neuroinflammation and neurovascular repair

Current therapies for immune-mediated inflammatory disorders in peripheral nerves are non-specific, and partly efficacious. Peripheral nerve regeneration following axonal degeneration or injury is suboptimal, with current therapies focused on modulating the underlying etiology and treating the consequences, such as neuropathic pain and weakness. Despite significant advances in understanding mechanisms of peripheral nerve inflammation, as well as axonal degeneration and regeneration, there has been limited translation into effective new drugs for these disorders. A major limitation in the field has been the unavailability of reliable disease models or research tools that mimic some key essential features of these human conditions. A relatively overlooked aspect of peripheral nerve regeneration has been neurovascular repair required to restore the homeostatic microenvironment necessary for normal function. Using Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) as examples of human acute and chronic immune-mediated peripheral neuroinflammatory disorders respectively, we have performed detailed studies in representative mouse models to demonstrate essential features of the human disorders. These models are important tools to develop and test treatment strategies using realistic outcomes measures applicable to affected patients. In vitro models of the human blood-nerve barrier using endothelial cells derived by endoneurial microvessels provide insights into pro-inflammatory leukocyte-endothelial cell interactions relevant to peripheral neuroinflammation, as well as potential mediators and signaling pathways required for vascular proliferation, angiogenesis, remodeling and tight junction specialization necessary to restore peripheral nerve function following injury. This review discusses the progress we are making in translational peripheral neurobiology and our future directions.

[Antiganglioside antibodies--their pathophysiological effects on Guillain-Barré syndrome and variants]

Gangliosides, N-acetylneuraminic acid (sialic acid)-bearing glycosphingolipids, are believed to reside in clusters within membrane microdomains, called lipid rafts or glycosynapse. Recent studies demonstrated that antiganglioside antibodies play an important role in the pathogenesis of Guillain-Barré syndrome (GBS) and Fisher syndrome (FS). The anti-GM1 antibodies are likely to damage peripheral nerves through complement activation with dysfunction of voltage-gated sodium channels. Some antiganglioside antibodies may cause dysfunction of voltage-gated calcium channels without complement activation. Clustered epitopes of ganglioside complexes (GSCs) consisting of two gangliosides can be targeted by serum antibodies in GBS and FS. Anti-GD1a/GD1b complex antibodies are associated with severe GBS. Approximately 50% of FS patients have antibodies to GSCs containing GQ1b or GT1a. Various glycolipids including GSCs may form complex glycolipid environment in the cell membrane, regulating the accessibility and the avidity of antiganglioside antibodies. In addition to antibody specificity, the glycolipid environment or specific distribution of target gangliosides in peripheral nervous system can influence pathogenic effects of antiganglioside antibodies in GBS and FS. Conformational and functional analyses of glycoepitopes of GSCs in the biological membrane will provide new vistas to research on antibody-antigen interaction in GBS, and shed light on microdomain function mediated by carbohydrate-to-carbohydrate interaction.

Antibodies to gangliosides and ganglioside complexes in Guillain-Barré syndrome and Fisher syndrome: mini-review

Antiganglioside antibodies play a pathogenic role in the pathophysiology of Guillain-Barré syndrome (GBS) and Fisher syndrome (FS). Antiganglioside antibody-mediated nerve injury is likely to result from nerve damage through complement activation or dysfunction of molecules such as voltage-gated sodium and calcium channels. Clustered epitopes of complexes of two gangliosides in the cell membrane can be targeted by serum antibodies in GBS and FS and may regulate the accessibility and avidity of antiganglioside antibodies. The glycolipid environment or the specific distribution of target gangliosides in the peripheral nervous system may also influence the pathogenic effect of antiganglioside antibodies in GBS and FS. Structural and functional analyses of glycoepitopes of ganglioside complexes in membranes will provide new vistas on antibody-antigen interaction in GBS and shed light on microdomain function mediated by carbohydrate-carbohydrate interactions, which may lead to novel treatments for GBS and FS.

Innate immunity in the nervous system

The complement (C) system plays a central role in innate immunity and bridges innate and adaptive immune responses. A fine balance of C activation and regulation mediates the elimination of invading pathogens and the protection of the host from excessive C deposition on healthy tissues. If this delicate balance is disrupted, the C system may cause injury and contribute to the pathogenesis of various diseases, including neurodegenerative disorders and neuropathies. Here we review evidence indicating that C factors and regulators are locally synthesized in the nervous system and we discuss the evidence supporting the protective or detrimental role of C activation in health, injury, and disease of the nerve.

Status of immune mediators in painful neuropathies

Peripheral neuropathies of identical etiology can be painful or painless. The reason for this difference in clinical presentation is as yet unknown; however, immune mediators, particularly cytokines, may play a role. Cytokines are proteins that are produced by immune and nonimmune cells and are categorized as pro- and anti-inflammatory. The role of cytokines in the induction and maintenance of pain has been well established in animal models. Proinflammatory cytokines are mostly algesic, whereas anti-inflammatory cytokines have analgesic properties. Clinical research also gives evidence for the involvement of cytokines in painful and painless neuropathies. A proinflammatory cytokine profile seems to be associated with pain in peripheral neuropathies of different etiologies and in other painful disorders such as the complex regional pain syndrome. Specifically, an imbalance between pro- and anti-inflammatory cytokines may contribute to pain generation. A better understanding of the underlying pathophysiology may open new opportunities for the treatment of pain.

Antiganglioside antibodies and their pathophysiological effects on Guillain-Barré syndrome and related disorders--a review

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy which can cause acute quadriplegia. Infection with micro-organisms, including Campylobacter jejuni (C. jejuni), Haemophilus influenzae, and Cytomegalovirus (CMV), is recognized as a main triggering event for the disease. Lipooligosaccharide (LOS) genes are responsible for the formation of human ganglioside-like LOS structures in infectious micro-organisms that can induce GBS. Molecular mimicry of LOSs on the surface of infectious agents and of ganglioside antigens on neural cells is thought to induce cross-reactive humoral and cellular immune responses. Patients with GBS develop antibodies against those gangliosides, resulting in autoimmune targeting of peripheral nerve sites, leading to neural damage. Heterogeneity of ganglioside expression in the peripheral nervous system (PNS) may underlie the differential clinical manifestation of the GBS variants. Recent studies demonstrate that some GBS sera react with ganglioside complexes consisting of two different gangliosides, such as GD1a and GD1b, or GM1 and GD1a, but not with each constituent ganglioside alone. The discovery of antiganglioside complex antibodies not only improves the detection rate of autoantibodies in GBS, but also provides a new concept in the antibody-antigen interaction through clustered carbohydrate epitopes. Although ganglioside mimicry is one of the possible etiological causes of GBS, unidentified factors may also contribute to the pathogenesis of GBS. While GBS is not considered a genetic disease, host factors, particularly human lymphocyte antigen type, appear to have a role in the pathogenesis of GBS following C. jejuni infection.

C5 inhibitor rEV576 protects against neural injury in an in vitro mouse model of Miller Fisher syndrome

Guillain-Barré syndrome and its clinical variants, including the anti-GQ1b ganglioside-mediated Miller Fisher syndrome (MFS), comprise the world's leading cause of acute neuromuscular paralysis. Presently, no specific drug therapies exist. The complement cascade, which is activated in these patients, forms an attractive drug target. In this study, we tested whether the complement C5-inhibiting recombinant protein, rEV576, was able to prevent neural injury in a previously developed in vitro mouse model for MFS. Mouse hemidiaphragm preparations were treated with anti-GQ1b antibody and normal human serum as a source of complement with added rEV576 or control protein. Immunohistology in control tissue showed deposition of C3c and membrane attack complex at neuromuscular junctions (NMJs), along with terminal motor axonal neurofilament degradation as well as ethidium homodimer-2 staining showing perisynaptic Schwann cell (pSC) injury. Electrophysiological and functional analyses showed block of synaptic transmission at the NMJ after an initial period of a dramatically high level of asynchronous acetylcholine release. In tissue treated with rEV576, all these indicators of motor neuronal damage were absent, except for the presence of C3c, indicating effective inhibition of C5. These results demonstrate that rEV576 effectively prevents development of neuronal and pSC damage in experimental murine neuropathy.

Complement inhibitor prevents disruption of sodium channel clusters in a rabbit model of Guillain-Barré syndrome

Complement-mediated disruption of voltage-gated sodium channels at the nodes of Ranvier acts in the development of acute motor axonal neuropathy. Nafamostat mesilate, a synthetic serine protease inhibitor, used in clinical practice for more than 20 years, has anti-complement activity. Acute motor axonal neuropathy rabbits obtained by GM1 ganglioside sensitization were or were not given nafamostat mesilate intravenously. Complement deposition and sodium channel disruption in the spinal anterior roots were significantly less frequent in the treated rabbits than in the controls. Nafamostat mesilate inhibited complement deposition and prevented sodium channel disruption. This provided the rationale for a clinical trial.

Anti-ganglioside antibodies and the presynaptic motor nerve terminal

The Guillain Barré syndromes (GBS) are the world's leading cause of acute autoimmune neuromuscular paralysis. Understanding the pathophysiological events of GBS, and improving immunotherapies are fundamental to improving the clinical outcome. Recent research into GBS and the Miller Fisher syndrome (MFS) variant has focused on the forms mediated by anti-ganglioside antibodies in which correlations have been established between anti-ganglioside antibodies and specific clinical phenotypes, notably between anti-GM1/GD1a antibodies and the acute motor axonal variant and anti-GQ1b/GT1a antibodies and MFS. Anti-ganglioside antibodies can arise through molecular mimicry with GBS-associated Campylobacter jejuni oligosaccharides. Our work has focused on axonal and glial components of the motor nerve terminal as a model site of injury, and through combined active and passive immunization paradigms in glycosyltransferase knockout mice we have developed murine neuropathy phenotypes mediated by anti-ganglioside antibodies. Several determinants influence disease expression including the level of immunological tolerance to microbial glycans that mimic self gangliosides, the degree of complement activation, and the ganglioside density in target tissue. Such studies provide us with clear information on an antibody-mediated pathogenesis model for GBS and should lead to rational therapeutic testing of agents that are potentially suitable for use in man.

CD4 T cells mediate axonal damage and spinal cord motor neuron apoptosis in murine p0106-125-induced experimental autoimmune neuritis

The pathogenesis of inflammatory autoimmune diseases of the peripheral nervous system, leading to demyelination and/or axonal damage, remains incompletely understood. In particular, it is controversial regarding the extent to which (i) autoimmune-mediated destruction of peripheral nerves results in secondary damage of the central nervous system, and (ii) CD4 and CD8 T cells contribute to disease. To address these issues, we applied the murine model of P0(106-125)-induced experimental autoimmune neuritis. Immunization of C57BL/6 mice with P0(106-125) resulted in severe axonal damage and mild demyelination. Importantly, these mice developed a "dying-back" axonopathy with apoptosis of a large fraction of neurons in the anterior horn of the lumbar and thoracic spinal cord and a progressive neurogenic muscular atrophy. T cell-depletion experiments identified CD4, but not CD8, T cells as important mediators of experimental autoimmune neuritis. CD4 T cells represented the major cellular source of antigen-specific interferon-gamma and interleukin-17 production, regulated the number of tumor necrosis factor-positive and inducible nitric oxide synthase-positive macrophages in the diseased sciatic nerve, and mediated axonal damage and subsequent neuronal apoptosis and neurogenic muscular atrophy. In contrast, the demyelination of peripheral nerves was only slightly ameliorated in CD4 T cell-depleted mice. In conclusion, P0(106-125)-induced experimental autoimmune neuritis is a CD4 T cell-mediated autoimmune disease that affects both the peripheral and central nervous systems.

Expression of cytokines and cytokine receptors in human Schwann cells

The expression of cytokines and cytokine receptors was investigated in enriched populations of human fetal Schwann cells by reverse transcribed-PCR and enzyme-linked immunosorbent assay. Human fetal Schwann cells constitutively expressed mRNA of IL-1beta, IL-6, IL-8, IL-11, IL-12, IL-15 and TGF-beta, and also cytokine receptors for IL-1, IL-4, IL-6, IL-8, IL-13, tissue necrosis factor and gp130. The expression of IL-1beta, IL-6 and IL-15 was upregulated following treatment with IL-1beta or TGF-beta. The protein levels of IL-6 were increased with IL-1beta treatment, but were decreased with IFN-gamma treatment. Human Schwann cells may respond to cytokine signals in the nerve injury sites and modify the pathological conditions by secreting cytokines. The secreted cytokines may play a role in leukocyte recruitment and exacerbation of axonal injury process.