Soluble complement receptor type 1 inhibits experimental autoimmune neuritis in Lewis rats

The Role of the Complement System in Chronic Inflammatory Demyelinating Polyneuropathy: Implications for Complement-Targeted Therapies

Chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common, heterogeneous, immune-mediated neuropathy, characterized by predominant demyelination of motor and sensory nerves. CIDP follows a relapsing-remitting or a progressive course and causes substantial disability. The pathogenesis of CIDP involves a complex interplay of multiple aberrant immune responses, creating a pro-inflammatory environment, subsequently inflicting damage on the myelin sheath. Though the exact triggers are unclear, diverse immune mechanisms encompassing cellular and humoral pathways are implicated. The complement system appears to play a role in promoting macrophage-mediated demyelination. Complement deposition in sural nerve biopsies, as well as signs of increased complement activation in serum and CSF of patients with CIDP, suggest complement involvement in CIDP pathogenesis. Here, we present a comprehensive overview of the preclinical and clinical evidence supporting the potential role of the complement system in CIDP. This understanding furnishes a strong rationale for targeting the complement system to develop new therapies that could serve the unmet needs of patients affected by CIDP, particularly in those refractory to standard therapies.

Nerve conductions studies in experimental models of autoimmune neuritis: A meta-analysis and guideline

Nerve conduction studies (NCS) are essential to assess peripheral nerve fiber function in research models of immune-mediated neuritis. However, the current lack of standard protocols and reference values impedes data comparability across models and studies. We performed a systematic review and subsequent meta-analysis of the last 30 years of NCS of immune-mediated neuritis in Lewis-rats. Twenty-six papers met the inclusion criteria for meta-analysis. Extracted data showed considerable heterogeneity of recorded nerve conduction velocity (NCV) and compound muscle action potential (CMAP). Studies also significantly differed in terms of technical, methodical, and data reporting issues. The heterogeneity of the underlying studies emphasizes the need for standardization when conducting and reporting NCS in rats. We provide normative values for NCS of the sciatic nerve of Lewis rats and propose seven items that should be addressed when NCS are performed when studying immune paradigms in Lewis rats.

NRG1 type I dependent autoparacrine stimulation of Schwann cells in onion bulbs of peripheral neuropathies

In contrast to acute peripheral nerve injury, the molecular response of Schwann cells in chronic neuropathies remains poorly understood. Onion bulb structures are a pathological hallmark of demyelinating neuropathies, but the nature of these formations is unknown. Here, we show that Schwann cells induce the expression of Neuregulin-1 type I (NRG1-I), a paracrine growth factor, in various chronic demyelinating diseases. Genetic disruption of Schwann cell-derived NRG1 signalling in a mouse model of Charcot-Marie-Tooth Disease 1A (CMT1A), suppresses hypermyelination and the formation of onion bulbs. Transgenic overexpression of NRG1-I in Schwann cells on a wildtype background is sufficient to mediate an interaction between Schwann cells via an ErbB2 receptor-MEK/ERK signaling axis, which causes onion bulb formations and results in a peripheral neuropathy reminiscent of CMT1A. We suggest that diseased Schwann cells mount a regeneration program that is beneficial in acute nerve injury, but that overstimulation of Schwann cells in chronic neuropathies is detrimental.

Onion bulbs are a hallmark of demyelinating peripheral neuropathies. Here the authors identify Neuregulin-1 type I expression in Schwann cells as an essential mechanism involved in the formation of these characteristic structures.

Biological Drugs in Guillain-Barré Syndrome: An Update

Background:

Guillain-Barré Syndrome (GBS) is currently considered the most common global cause of acute flaccid paralysis. Currently, standard therapy for Guillain-Barré Syndrome includes intravenous immunoglobulin or plasma exchange. Despite medical advances regarding these treatments, many treated patients do not reach full recovery. Therefore several biological agents have attracted the attentions from researchers during the last decades, and various studies have investigated their role in Guillain-Barré Syndrome.

Objective:

The present study aims to address emerging biological approaches to GBS while considering their efficiency and safety in treating the disease.

Materials and Methods:

An extensive electronic literature search was conducted by two researchers from April 2016 to July 2016. Original articles, clinical trials, systematic reviews (with or without meta-analysis) and case reports were selected. Titles and abstracts of papers were screened by reviewers to determine whether they met the eligibility criteria, and full texts of the selected articles were retrieved.

Results:

Herein authors focused on the literature data concerning emerging biological therapeutic agents, namely anti-C5 monoclonal antibody (Eculizumab), anti-C1q monoclonal antibody, anti-T cell monoclonal antibody, anti-CD2 monoclonal antibody, anti L-selectin monoclonal antibody, anti-CD20 monoclonal antibody (Rituximab), anti-CD52 monoclonal antibody (Alemtuzumab) and cytokine targets. By far, none of these agents have been approved for the treatment of GBS by FDA.

Conclusion:

Literature findings represented in current review herald promising results for using these biological targets. Current review represents a summary of what is already in regards and what progress is required to improve the immunotherapeutic approach of treating GBS via future studies.

Tissue resident macrophages are sufficient for demyelination during peripheral nerve myelin induced experimental autoimmune neuritis?

The contribution of resident endoneurial tissue macrophages versus recruited monocyte derived macrophages to demyelination and disease during Experimental Autoimmune Neuritis (EAN) was investigated using passive transfer of peripheral nerve myelin (PNM) specific serum antibodies or adoptive co-transfer of PNM specific T and B cells from EAN donors to leukopenic and normal hosts. Passive transfer of PNM specific serum antibodies or adoptive co-transfer of myelin specific T and B cells into leukopenic recipients resulted in a moderate reduction in nerve conduction block or in the disease severity compared to the normal recipients. This was despite at least a 95% decrease in the number of circulating mononuclear cells during the development of nerve conduction block and disease and a 50% reduction in the number of infiltrating endoneurial macrophages in the nerve lesions of the leukopenic recipients. These observations suggest that during EAN in Lewis rats actively induced by immunization with peripheral nerve myelin, phagocytic macrophages originating from the resident endoneurial population may be sufficient to engage in demyelination initiated by anti-myelin antibodies in this model.

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.

The role of complement in neurological and neuropsychiatric diseases

The complement system is a major component of innate immunity and a potent driver of inflammation. It has key roles in host defense against pathogens but can also contribute to pathology by driving inflammation and cell damage in diverse diseases. Complement has emerged as an important factor in the pathogenesis of numerous diseases of the CNS and PNS, including infectious, autoimmune and degenerative disorders, and is increasingly implicated in neuropsychiatric disease. Establishing the roles and relevance of complement in disease pathogenesis has become ever more important in recent years as new drugs targeting the complement system have reached the clinic, and the potential for using complement analytes as disease biomarkers has been recognized. In this brief review, the author summarizes the evidence implicating complement in these diseases and outlines ways in which this new understanding can be used to aid diagnosis and improve outcome.

FoxP3+ regulatory T cells determine disease severity in rodent models of inflammatory neuropathies

Inflammatory neuropathies represent disabling human autoimmune disorders with considerable disease variability. Animal models provide insights into defined aspects of their disease pathogenesis. Forkhead box P3 (FoxP3)+ regulatory T lymphocytes (Treg) are anti-inflammatory cells that maintain immune tolerance and counteract tissue damage in a variety of immune-mediated disorders. Dysfunction or a reduced frequency of Tregs have been associated with different human autoimmune disorders. We here analyzed the functional relevance of Tregs in determining disease manifestation and severity in murine models of autoimmune neuropathies. We took advantage of the DEREG mouse system allowing depletion of Treg with high specificity as well as anti-CD25 directed antibodies to deplete Tregs in mice in actively induced experimental autoimmune neuritis (EAN). Furthermore antibody-depletion was performed in an adoptive transfer model of chronic neuritis. Early Treg depletion increased clinical EAN severity both in active and adoptive transfer chronic neuritis. This was accompanied by increased proliferation of myelin specific T cells and histological signs of peripheral nerve inflammation. Late stage Treg depletion after initial disease manifestation however did not exacerbate inflammatory neuropathy symptoms further. We conclude that Tregs determine disease severity in experimental autoimmune neuropathies during the initial priming phase, but have no major disease modifying function after disease manifestation. Potential future therapeutic approaches targeting Tregs should thus be performed early in inflammatory neuropathies.

A reliable in vitro model for studying peripheral nerve myelination in mouse

The rat dorsal root ganglia (DRG) model is a long-standing in vitro model for analysis of myelination in the peripheral nervous system. For performing systematic, high throughput analysis with transgenic animals, a simplified BL6 mouse protocol is indispensable. Here we present a stable and reliable protocol for myelinating co-cultures producing a high myelin ratio using cells from C57BL/6 mice. As an easy accessible and operable method, Sudan staining proved to be efficient in myelin detection for fixed cultures. Green fatty acid stain turned out to be highly reliable for analysis of the dynamic biological processes of myelination in vital cultures. Once myelinated we were able to induce demyelination by the addition of forskolin into the model system. In addition, we provide an optimised rat DRG protocol with significantly improved myelin ratio and a comparison of the protocols presented. Our results strengthen the value of ex vivo myelination models in neurobiology.

Erythropoietin ameliorates rat experimental autoimmune neuritis by inducing transforming growth factor-β in macrophages

Erythropoietin (EPO) is a pleiotropic cytokine originally identified for its role in erythropoiesis. In addition, in various preclinical models EPO exhibited protective activity against tissue injury. There is an urgent need for potent treatments of autoimmune driven disorders of the peripheral nervous system (PNS), such as the Guillain-Barré syndrome (GBS), a disabling autoimmune disease associated with relevant morbidity and mortality. To test the therapeutic potential of EPO in experimental autoimmune neuritis (EAN) - an animal model of human GBS--immunological and clinical effects were investigated in a preventive and a therapeutic paradigm. Treatment with EPO reduced clinical disease severity and if given therapeutically also shortened the recovery phase of EAN. Clinical findings were mirrored by decreased inflammation within the peripheral nerve, and myelin was well maintained in treated animals. In contrast, EPO increased the number of macrophages especially in later stages of the experimental disease phase. Furthermore, the anti-inflammatory cytokine transforming growth factor (TGF)-beta was upregulated in the treated cohorts. In vitro experiments revealed less proliferation of T cells in the presence of EPO and TGF-beta was moderately induced, while the secretion of other cytokines was almost not altered by EPO. Our data suggest that EPO revealed its beneficial properties by the induction of beneficial macrophages and the modulation of the immune system towards anti-inflammatory responses in the PNS. Further studies are warranted to elaborate the clinical usefulness of EPO for treating immune-mediated neuropathies in affected patients.

Quinpramine ameliorates rat experimental autoimmune neuritis and redistributes MHC class II molecules

Activation of inflammatory cells is central to the pathogenesis of autoimmune demyelinating diseases of the peripheral nervous system. The novel chimeric compound quinpramine—generated from imipramine and quinacrine—redistributes cholesterol rich membrane domains to intracellular compartments. We studied the immunological and clinical effects of quinpramine in myelin homogenate induced Lewis rat experimental autoimmune neuritis (EAN), a model system for acute human inflammatory neuropathies, such as the Guillain-Barré syndrome. EAN animals develop paresis of all limbs due to autoimmune inflammation of peripheral nerves. Quinpramine treatment ameliorated clinical disease severity of EAN and infiltration of macrophages into peripheral nerves. It reduced expression of MHC class II molecules on antigen presenting cells and antigen specific T cell proliferation both in vitro and in vivo. Quinpramine exerted its anti-proliferatory effect on antigen presenting cells, but not on responder T cells. Our data suggest that quinpramine represents a candidate pharmaceutical for inflammatory neuropathies.

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.

Soluble complement receptor 1 protects the peripheral nerve from early axon loss after injury

Complement activation is a crucial early event in Wallerian degeneration. In this study we show that treatment of rats with soluble complement receptor 1 (sCR1), an inhibitor of all complement pathways, blocked both systemic and local complement activation after crush injury of the sciatic nerve. Deposition of membrane attack complex (MAC) in the nerve was inhibited, the nerve was protected from axonal and myelin breakdown at 3 days after injury, and macrophage infiltration and activation was strongly reduced. We show that both classical and alternative complement pathways are activated after acute nerve trauma. Inhibition of the classical pathway by C1 inhibitor (Cetor) diminished, but did not completely block, MAC deposition in the injured nerve, blocked myelin breakdown, inhibited macrophage infiltration, and prevented macrophage activation at 3 days after injury. However, in contrast to sCR1 treatment, early signs of axonal degradation were visible in the nerve, linking MAC deposition to axonal damage. We conclude that sCR1 protects the nerve from early axon loss after injury and propose complement inhibition as a potential therapy for the treatment of diseases in which axon loss is the main cause of disabilities.

Soluble TNFR1 inhibits the development of experimental autoimmune neuritis by modulating blood–nerve-barrier permeability and inflammation

The role of TNFalpha/LTalpha during EAN induced by active immunization with peripheral nerve myelin was examined by administering a recombinant soluble chimeric form of human TNF receptor 1 (TNFR1-IgG). TNFalpha and LTalpha do not directly contribute to neurological deficit during EAN since treatment with TNFR1-IgG after onset failed to alter the course of disease. Prophylaxis with a single dose of TNFR1-IgG delayed the onset of EAN and was accompanied initially by inhibition of blood-nerve-barrier permeability and inflammation. Subsequently, the number of infiltrating macrophages and blood-nerve-barrier permeability increased but the disease symptoms remained mild for five days (on average a limp tail) after which severe EAN developed. The antibody titer to peripheral nerve myelin was unaltered by prophylaxis with TNFR1-IgG. The markedly altered tempo of disease onset after TNFR1-IgG prophylaxis indicates that TNFalpha and/or LTalpha have a key role in the development of blood-nerve-barrier permeability and the coupling of macrophage activation and recruitment to peripheral nerve pathology during EAN.

Pros and cons of treating murine myasthenia gravis with anti-C1q antibody

To test the feasibility of classical complement pathway manipulation in experimental autoimmune myasthenia gravis (EAMG) treatment, C57BL/6 (B6) and RIIIS/J mice with EAMG were treated with 10 microg or 100 microg of anti-C1q Ab or isotype Ab. Treatment with 10 microg anti-C1q Ab significantly reduced the clinical severity, decreased lymph node cell IL-6 production and T cell populations. Conversely, administration of 100 microg anti-C1q Ab caused harmful side effects such as increased serum anti-acetylcholine receptor antibody, immune complex, C3 and lymph node B cell levels and kidney C3 and IgG deposits, which reduced the treatment efficacy.

Strategies of therapeutic complement inhibition

The involvement of complement in the pathogenesis of a great number of partly life threatening diseases defines the importance to develop inhibitors which specifically interfere with its deleterious action. Endogenous soluble complement-inhibitors, antibodies or low molecular weight antagonists, either blocking key proteins of the cascade reaction or neutralizing the action of the complement-derived anaphylatoxins have successfully been tested in various animal models over the past years. Promising results consequently led to first clinical trials. This review is focused on different approaches for the development of inhibitors, on their site of action in the cascade, on possible indications for complement inhibition based on experimental animal data, and on potential side effects of such treatment.

Peri-sciatic proinflammatory cytokines, reactive oxygen species, and complement induce mirror-image neuropathic pain in rats

In inflammatory neuropathy, immune activation near intact peripheral nerves induces mechanical allodynia. The identity of the peripheral immune product(s) that lead to these changes in pain behavior is unknown. The present series of studies utilized the sciatic inflammatory neuropathy (SIN) model to examine this question. Here, inflammatory neuropathy is created by injecting an immune activator (zymosan) around one sciatic nerve via an indwelling catheter. Our prior studies demonstrated that peri-sciatic zymosan activated macrophages and neutrophils to release proinflammatory cytokines and reactive oxygen species (ROS). In addition, zymosan is a classical activator of the complement cascade. Thus the present series of experiments examined whether any of these inflammatory mediators are involved in the initial induction of SIN-induced ipsilateral or bilateral allodynias. Peri-sciatic injection of selective inhibitors/antagonists revealed that a number of immune products are early mediators of the resultant allodynias, including proinflammatory cytokines (tumor necrosis factor, interleukin-1, and interleukin-6), ROS, and complement. Thus these immune-derived substances can markedly alter sensory nerve function at mid-axon.

Assessment of experimental autoimmune neuritis in the rat by electrophysiology of the tail nerve

The assessment of experimental autoimmune neuritis (EAN) by electrophysiological studies of the sciatic innervation of the plantar muscle may be complicated by local inflammation. We therefore utilized the tail nerve-muscle system to monitor disease progression in 20 rats with EAN and 10 control rats. Early changes were detected in motor nerve conduction velocity (32.06 +/- 1.85 m/s versus 43.57 +/- 3.98 m/s in controls, P < 0.001) at 15 days postimmunization (DPI), and conduction block (70.6 +/- 9.4% compared to 12.4 +/- 3.4%, P < 0.001) at 22 DPI. No consistent conduction block (22.4 +/- 10.4%) was found in the plantar muscle measurements. The tail nerve response of EAN rats demonstrated severe temporal dispersion at 43 DPI, which returned to normal at 135 DPI, although motor nerve conduction velocity values were still lower than in controls (24.4 +/- 0.9 m/s, P < 0.001). The tail nerve may be a useful addition to electrophysiological studies in this model of the Guillain-Barré syndrome.

Sciatic inflammatory neuritis (SIN): behavioral allodynia is paralleled by peri-sciatic proinflammatory cytokine and superoxide production

We have recently developed a model of sciatic inflammatory neuritis (SIN) to assess how immune activation near peripheral nerves influences somatosensory processing. Administration of zymosan (yeast cell walls) around a single sciatic nerve produces dose-dependent low-threshold mechanical allodynia without thermal hyperalgesia. Low (4 microg) doses produce both territorial and extraterritorial allodynia restricted to the injected hindleg. In contrast, higher (40 microg) doses produce territorial and extraterritorial allodynias of both hindlegs, an effect not accounted for by systemic spread of the zymosan. The aim of these experiments was to determine whether these behavioral allodynias were correlated with immunological and/or anatomical changes in or around the sciatic nerve. These experiments reveal that zymosan-induced bilateral allodynia was associated with the following: (a) increased release of both interleukin-1beta and tumor necrosis factor-alpha from peri-sciatic immune cells; (b) increased release of reactive oxygen species from perisciatic immune cells; (c) no change in circulating levels of proinflammatory cytokine; (d) no apparent zymosan-induced influx of immune cells into the sciatic nerve from the endoneurial blood vessels; (e) mild edema of the sciatic, which was predominantly restricted to superficial regions closest to the peri-sciatic immune cells; and (f) no anatomic evidence of changes in either the ipsilateral saphenous nerve or contralateral sciatic nerve that could account for the appearance of extraterritorial or contralateral ("mirror") allodynia, respectively. No reliable differences were found when the low-dose zymosan was compared with vehicle controls. Taken together, these data suggest that substances released by peri-sciatic immune cells may induce changes in the sciatic nerve, leading to the appearance of bilateral allodynia.

The role of macrophages in immune-mediated damage to the peripheral nervous system

Macrophage-mediated segmental demyelination is the pathological hallmark of autoimmune demyelinating polyneuropathies, including the demyelinating form of Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy. Macrophages serve a multitude of functions throughout the entire pathogenetic process of autoimmune neuropathy. Resident endoneurial macrophages are likely to act as local antigen-presenting cells by their capability to express major histocompatibility complex antigens and costimulatory B7-molecules, and may thus be critical in triggering the autoimmune process. Hematogenous infiltrating macrophages then find their way into the peripheral nerve together with T-cells by the concerted action of adhesion molecules, matrix metalloproteases and chemotactic signals. Within the nerve, macrophages regulate inflammation by secreting several pro-inflammatory cytokines including IL-1, IL-6, IL-12 and TNF-alpha. Autoantibodies are likely to guide macrophages towards their myelin or primarily axonal targets, which then attack in a complement-dependent and receptor-mediated manner. In addition, non-specific tissue damage occurs through the secretion of toxic mediators and cytokines. Later, macrophages contribute to the termination of inflammation by promoting T-cell apoptosis and expressing anti-inflammatory cytokines including TGF-beta1 and IL-10. During recovery, they are tightly involved in allowing Schwann cell proliferation, remyelination and axonal regeneration to proceed. Macrophages, thus, play dual roles in autoimmune neuropathy, being detrimental in attacking nervous tissue but also salutary, when aiding in the termination of the inflammatory process and the promotion of recovery.

Sequential expression of chemokines in experimental autoimmune neuritis

Recruitment of inflammatory cells is of critical importance in the pathogenesis of immune-mediated demyelinating diseases in the peripheral nervous system (PNS). Evidence is increasing that chemokines might play a key role in this process, since they promote leukocyte entry into the nervous system during immune-mediated inflammation. In the present study we report the expression pattern of the chemokines interferon-gamma-inducible protein (IP)-10, monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and regulated upon activation normal T cell expressed and secreted (RANTES) in sciatic nerves from animals with myelin-induced experimental autoimmune neuritis, using a semiquantitative reverse transcriptase-PCR dot-blot hybridization assay. The mRNAs for MIP-1alpha and MIP-1beta were found to be upregulated with peak values at day 13 post-immunization (p.i.), preceding maximum disease severity. In contrast, mRNAs for MCP-1, RANTES, and IP-10 exhibited peak levels coincident with peak of the disease at day 15 p.i. Increased mRNA expression was associated with enhanced protein levels, as demonstrated by immunoblotting for each chemokine investigated. Immunohistochemistry for IP-10 protein revealed immunoreactivity associated with perineurial endothelial cells. RANTES protein was localized immunohistologically to invading T lymphocytes. Our findings suggest that chemokines, which act towards T cells and mononuclear phagocytes, are sequentially upregulated during the clinical course of EAN and thus may contribute to the pathogenesis of inflammatory demyelinating diseases of the PNS.

Novel therapeutic approaches to Guillain-Barré syndrome

Guillain-Barré syndrome is an autoimmune disease which occurs throughout the world. Whilst the majority of patients can expect a reasonable recovery, about 10% die and 10% are left disabled with current therapy. The standard treatment is a five day course of iv. immunoglobulin, given at a dose of 0.4 g/kg/day, with plasma exchange as an equally efficacious alternative. Steroids are ineffective in Guillain-Barré syndrome. All new potential therapeutic agents need to be tested in addition to the standard agents available. Future potential therapies are suggested by the study of the animal model experimental autoimmune neuritis in the Lewis rat. Whilst in theory it is possible to target the different stages of the immune response, in practice not all of the steps at which experimental autoimmune neuritis can be prevented will be translatable to human Guillain-Barré syndrome. This is because Guillain-Barré syndrome probably presents after the immune reaction has been ongoing for some time and therefore early aspects of the immune response cannot be prevented. Many of the possible measures would have widespread immunosuppressive effects which would be unacceptable to patients. Interfering with the immune response by attempting to block antigen binding or inducing tolerance may not be practical, owing to the possibility of exacerbating disease. Once we have a more thorough understanding of the pathogenesis of Guillain-Barré syndrome, then immune-specific therapy for Guillain-Barré syndrome may become a possibility, rather than general immunosuppressive measures. Trials of beta-interferon and of a combination of steroid and i.v. immunoglobulin are underway. A trial of a second course of i.v. immunoglobulin is planned.

Development of Adenovirus Vectors Encoding Rat Complement Regulators for Use in Therapy in Rodent Models of Inflammatory Diseases

C activation has been implicated in the pathogenesis of numerous inflammatory human diseases and disease models. A therapy based on C inhibition might therefore be of benefit to reduce inflammation and ameliorate disease. C inhibition in vivo can be accomplished by the delivery of soluble recombinant C regulators either systemically or directly to a target site, but effects are transitory. We have developed a strategy for the efficient delivery of the membrane-bound rat C inhibitors, CD59, Crry, and decay-accelerating factor (DAF), using replication-deficient adenovirus vectors with the intention of treating rat models of disease in which C is implicated. The adenovirus recombinants(RAd), RAdCD59, RAdCrry, and RAdDAF, respectively, have been tested for expression and function of the transgene in vitro. Infection of human fetal foreskin fibroblasts resulted in high levels of expression of each of the rat inhibitors. The constructs were also tested for inhibition of rat C-mediated cell lysis and C3b deposition. In a cell lysis assay, each inhibited to varying degrees of efficiency in the order RAdCD59 = RAdDAF &gt; RAdCrry. In a C3b deposition assay, RAdDAF caused a greater reduction in C3b deposition than RAdCrry and RAdCD59 was ineffective. These agents, individually or in combination, provide the tools for testing the effects of prolonged inhibition of C at a target site on the progress of experimental models of disease.

The expression of CD59 in experimental allergic neuritis

Complement is implicated as an effector in inflammatory demyelination occurring in Guillain-Barré syndrome (GBS) and in experimental allergic neuritis (EAN). CD59, a potent complement regulatory protein that inhibits the formation of the terminal cytolytic membrane attack complex (MAC), is expressed on human and rat Schwann cells. In EAN the expression of CD59 was increased on Schwann cells during demyelination and axonal degeneration, evaluated by immunostaining of nerve sections and teased fibres. Mac-1 (CD11b) positive leukocytes were localized close to the Schwann cells showing enhanced CD59 staining. The increased CD59 expression in EAN could therefore be due to the release of cytokines or other immunoregulatory molecules from the inflammatory cells. However, interferon gamma (IFN-gamma) or tumor necrosis factor alfa (TNF-alpha) did not upregulate the expression of CD59 on rat Schwann cells in culture. The increased expression of CD59 in EAN is likely to be important in the protection of Schwann cells from MAC.

Soluble complement receptor 1 (sCR1) is not as effective as cobra venom factor in the treatment of experimental allergic neuritis

To further investigate the role of complement activation in Experimental Allergic Neuritis (EAN), the effect of systemic complement blockade by soluble CR1 (sCR1) was compared to complement depletion by Cobra Venom Factor (CVF) in EAN rats immunized with bovine peripheral nerve myelin. EAN rats treated with CVF (n = 10) had significantly reduced clinical scores compared to rats treated with sCR1 (n = 9) or saline (n = 10) (score: sCR1 0.66 +/- 0.7; CVF 0; saline 0.6 +/- 0.8; mean +/- SD). CVF treatment more effectively decreased inflammation and demyelination compared to sCR1 treatment which had only a partial effect (inflammation: sCR1 1.8 +/- 1.4; CVF 0.3 +/- 0.7; saline 1.9 +/- 1.2; demyelination; sCR1 1.3 +/- 1; CVF 0.1 +/- 0.6; saline 1.7 +/- 1.2). In lumbosacral nerve roots significantly less infiltrating ED1 positive macrophages and CD11bc (expressing complement receptor 3 or CR3) positive inflammatory cells were present in CVF treated EAN rats while there was a limited decrease in inflammation in the sCR1 treated animals compared to the saline treated rats (ED1: sCR1 1.4 +/- 1.2; CVF 0.5 +/- 0.6; saline 1.7 +/- 1.2; CD11bc: sCR1 1.9 +/- 1.2; CVF 0.9 +/- 1; saline 2.1 +/- 1.2). Our findings suggest that complement depletion by CVF is more effective than complement blockade by sCR1 in reducing the severity of inflammatory peripheral nerve demyelination.

Soluble complement receptor 1 (sCR1) protects against experimental autoimmune myasthenia gravis

The loss of muscle function seen in myasthenia gravis and in the animal model of the disease, experimental autoimmune myasthenia gravis (EAMG) is in part due to the activation of complement by anti-acetylcholine receptor (AChR) antibodies at the motor end-plate. In this study we describe the effects of a soluble recombinant form of human complement receptor 1 (sCR1) on the development of clinical disease and receptor loss in EAMG induced passively by administration of anti-AChR antibodies. Daily intraperitoneal injection of sCR1 significantly reduced the weight loss and severity of clinical symptoms seen and allowed treated animals to recover normal muscle function. These data suggest that sCR1 could provide a useful additional therapeutic agent in myasthenia.

Immune attack on the Schwann cell surface in acute inflammatory demyelinating polyneuropathy

The localization, mode of action, and roles of complement in the Guillain-Barre syndrome have been controversial. We used high-resolution immunocytochemistry to localize complement activation products in early stages of the acute inflammatory demyelinating polyneuropathy (AIDP) pattern of Guillain-Barre syndrome. Three AIDP subjects who were autopsied had had symptoms for 3 to 9 days at the time of death. Immunocytochemistry was performed on etched, epoxy resin-embedded sections, and the next thin section was compared by electron microscopy (thick/thin sections). Many fibers had a rim of the complement activation marker C3d and the terminal complement complex neoantigen C5b-9 along the outer surface of the Schwann cells. Ultrastructural analysis of these C3d-positive fibers showed mild vesicular changes of the outermost myelin lamellae. Vesicular degeneration was seen before the invasion of macrophages into the myelin, and was the predominant change in the subject with symptoms for 3 days. C3d staining was not found on myelin membranes. The results suggest that at least some forms of AIDP are complement mediated. We speculate that complement is activated by antibody bound to epitopes on the outer surface of the Schwann cell and that the resulting complement activation initiates the vesiculation of myelin.