Human autoimmune neuropathies

Role of tubulin post-translational modifications in peripheral neuropathy

Peripheral neuropathy is a common disorder that results from nerve damage in the periphery. The degeneration of sensory axon terminals leads to changes or loss of sensory functions, often manifesting as debilitating pain, weakness, numbness, tingling, and disability. The pathogenesis of most peripheral neuropathies remains to be fully elucidated. Cumulative evidence from both early and recent studies indicates that tubulin damage may provide a common underlying mechanism of axonal injury in various peripheral neuropathies. In particular, tubulin post-translational modifications have been recently implicated in both toxic and inherited forms of peripheral neuropathy through regulation of axonal transport and mitochondria dynamics. This knowledge forms a new area of investigation with the potential for developing therapeutic strategies to prevent or delay peripheral neuropathy by restoring tubulin homeostasis.

Early targeting of endoneurial macrophages alleviates the neuropathy and affects abnormal Schwann cell differentiation in a mouse model of Charcot-Marie-Tooth 1A

We have previously shown that targeting endoneurial macrophages with the orally applied CSF-1 receptor specific kinase (c-FMS) inhibitor PLX5622 from the age of 3 months onwards led to a substantial alleviation of the neuropathy in mouse models of Charcot-Marie-Tooth (CMT) 1X and 1B disease, which are genetically-mediated nerve disorders not treatable in humans. The same approach failed in a model of CMT1A (PMP22-overexpressing mice, line C61), representing the most frequent form of CMT. This was unexpected since previous studies identified macrophages contributing to disease severity in the same CMT1A model. Here we re-approached the possibility of alleviating the neuropathy in a model of CMT1A by targeting macrophages at earlier time points. As a proof-of-principle experiment, we genetically inactivated colony-stimulating factor-1 (CSF-1) in CMT1A mice, which resulted in lower endoneurial macrophage numbers and alleviated the neuropathy. Based on these observations, we pharmacologically ablated macrophages in newborn CMT1A mice by feeding their lactating mothers with chow containing PLX5622, followed by treatment of the respective progenies after weaning until the age of 6 months. We found that peripheral neuropathy was substantially alleviated after early postnatal treatment, leading to preserved motor function in CMT1A mice. Moreover, macrophage depletion affected the altered Schwann cell differentiation phenotype. These findings underscore the targetable role of macrophage-mediated inflammation in peripheral nerves of inherited neuropathies, but also emphasize the need for an early treatment start confined to a narrow therapeutic time window in CMT1A models and potentially in respective patients.

The Neuroimmunology of Guillain-Barré Syndrome and the Potential Role of an Aging Immune System

Guillain-Barré syndrome (GBS) is a paralyzing autoimmune condition affecting the peripheral nervous system (PNS). Within GBS there are several variants affecting different aspects of the peripheral nerve. In general, there appears to be a role for T cells, macrophages, B cells, and complement in initiating and perpetuating attacks on gangliosides of Schwann cells and axons. Of note, GBS has an increased prevalence and severity with increasing age. In addition, there are alterations in immune cell functioning that may play a role in differences in GBS with age alongside general age-related declines in reparative processes (e.g., delayed de-differentiation of Schwann cells and decline in phagocytic ability of macrophages). The present review will explore the immune response in GBS as well as in animal models of several variants of the disorder. In addition, the potential involvement of an aging immune system in contributing to the increased prevalence and severity of GBS with age will be theorized.

Anti-neurofilament antibodies and neurodegeneration: Markers and generators

Neuroaxonal injury and loss result in the release of cytoskeleton components, including neurofilaments, into the cerebrospinal fluid and peripheral blood. Once released, neurofilaments are highly immunogenic, inducing a specific antibody response. Anti-neurofilament antibody levels correlate with the progression of diverse neurological diseases; however, their role both in the pathogenesis of disease and as a tool for monitoring disease progression is not well understood. This study reviews the current literature on anti-neurofilament antibodies. We suggest the testing of anti-neurofilament antibodies be further developed for diagnosis and targeted for treatment.

Brachial Plexus Injuries in Sport Medicine: Clinical Evaluation, Diagnostic Approaches, Treatment Options, and Rehabilitative Interventions

The brachial plexus represents a complex anatomical structure in the upper limb. This "network" of peripheral nerves permits the rearrangement of motor efferent fibers, coming from different spinal nerves, in several terminal branches directed to upper limb muscles. Moreover, afferent information coming from different cutaneous regions in upper limb are sorted in different spinal nerves through the brachial plexus. Severe brachial plexus injuries are a rare clinical condition in the general population and in sport medicine, but with dramatic consequences on the motor and sensory functions of the upper limb. In some sports, like martial arts, milder injuries of the brachial plexus can occur, with transient symptoms and with a full recovery. Clinical evaluation represents the cornerstone in the assessment of the athletes with brachial plexus injuries. Electrodiagnostic studies and imaging techniques, like magnetic resonance and high-frequency ultrasound, could be useful to localize the lesion and to define an appropriate treatment and a functional prognosis. Several conservative and surgical techniques could be applied, and multidisciplinary rehabilitative programs could be performed to guide the athlete toward the recovery of the highest functional level, according to the type of injury.

Biomarkers of Renal Tumors: the Current State and Clinical Perspectives

Renal cell carcinoma (RCC) ranks the first death rate among the urogenital tumors, whereas its incidence follows the incidences of prostate and bladder cancer. The diagnosis of RCC at early stages allows immediately undertaking appropriate treatment, which significantly increases patients' survival rate. Early and accurate diagnosis avoids inadequate treatment, provides the disease progression forecast, and permits to apply more efficient therapy. Unfortunately, the small renal tumors are usually asymptomatic resulting in the late diagnosis and, therefore, low efficacy of treatment. Thus, sensible and preventive biomarkers are essential for early RCC detection and monitoring of its progression. So far, many attempts were performed aimed at recognizing novel informative kidney tumor biomarkers applicable for early detection of the disease and possessing prognostic and predictive capabilities. This review summarizes recent advances in renal tumor biomarkers recognition, their diagnostic and prognostic values, and clinical feasibility.

Guillain-Barré syndrome: a century of progress

In 1916, Guillain, Barré and Strohl reported on two cases of acute flaccid paralysis with high cerebrospinal fluid protein levels and normal cell counts - novel findings that identified the disease we now know as Guillain-Barré syndrome (GBS). 100 years on, we have made great progress with the clinical and pathological characterization of GBS. Early clinicopathological and animal studies indicated that GBS was an immune-mediated demyelinating disorder, and that severe GBS could result in secondary axonal injury; the current treatments of plasma exchange and intravenous immunoglobulin, which were developed in the 1980s, are based on this premise. Subsequent work has, however, shown that primary axonal injury can be the underlying disease. The association of Campylobacter jejuni strains has led to confirmation that anti-ganglioside antibodies are pathogenic and that axonal GBS involves an antibody and complement-mediated disruption of nodes of Ranvier, neuromuscular junctions and other neuronal and glial membranes. Now, ongoing clinical trials of the complement inhibitor eculizumab are the first targeted immunotherapy in GBS.

Neurodegeneration in Multiple Sclerosis: Relationship to Neurological Disability

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS. Most MS patients follow a relapsing-remitting course (RR-MS) for 8 to 15 years that transforms into a secondary progressive disease course (SP-MS). In this review, we discuss current data that describe MS as a neurodegenerative disease in which axonal loss is the major cause of irreversible neurological disability in MS patients. Neurological deficits in MS patients have two pathogeneses: acute inflammatory demyelination and axonal degeneration. Disability caused by inflammatory demyelination clinically dominates the early stages of RR-MS and is reversible. Axonal transection occurs at sites of inflammation and begins at disease onset but is clinically silent in RR-MS because the CNS compensates for neuronal loss. Once a threshold of axon loss is ex ceeded, MS patients enter an irreversible secondary progressive stage. In SP-MS, axonal degeneration is caused by chronic demyelination and may be irreversibly progressive. This view of MS provides a concep tional framework that explains conversion of RR-MS to SP-MS and provides a rationale for early aggressive anti-inflammatory and neuroprotective therapies. NEUROSCIENTIST 5:48-57, 1999

Pathogenesis of Guillain–Barré syndrome

Guillain-Barre syndrome is a postinfectious disorder caused by an aberrant immune response to an infectious pathogen, resulting in an autoimmune disease. As with other autoimmune diseases of infectious nature, the intricate balance of the numerous factors involved in the immune response may determine the outcome of the interaction between the microbe and host. Recent studies focusing on the role of cytokines and its network of related mediators and receptors suggest that any imbalance may make a significant contribution to the outcome of the infectious disease process. Better understanding of the pathogenesis of Guillain-Barre syndrome may lead to the discovery of newer therapeutics and may also serve as a model for studying other autoimmune diseases.

Animal models of autoimmune neuropathy

The peripheral nervous system (PNS) comprises the cranial nerves, the spinal nerves with their roots and rami, dorsal root ganglia neurons, the peripheral nerves, and peripheral components of the autonomic nervous system. Cell-mediated or antibody-mediated immune attack on the PNS results in distinct clinical syndromes, which are classified based on the tempo of illness, PNS component(s) involved, and the culprit antigen(s) identified. Insights into the pathogenesis of autoimmune neuropathy have been provided by ex vivo immunologic studies, biopsy materials, electrophysiologic studies, and experimental models. This review article summarizes earlier seminal observations and highlights the recent progress in our understanding of immunopathogenesis of autoimmune neuropathies based on data from animal models.

The therapeutic role of interleukin-10 after spinal cord injury

Spinal cord injury (SCI) is a devastating condition affecting 270,000 people in the United States. A potential treatment for decreasing the secondary inflammation, excitotoxic damage, and neuronal apoptosis associated with SCI, is the anti-inflammatory cytokine interleukin-10. The best characterized effects of IL-10 are anti-inflammatory-it downregulates pro-inflammatory species interleukin-1β (IL-1β), interleukin-2 (IL-2), interleukin-6 (IL-6), tumor necrosis factor-α, interferon-γ, matrix metalloproteinase-9, nitric oxide synthase, myeloperoxidase, and reactive oxygen species. Pro-apoptotic factors cytochrome c, caspase 3, and Bax are downregulated by IL-10, whereas anti-apoptotic factors B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X, B-cell lymphoma-extra large (Bcl-xl) are upregulated by IL-10. IL-10 also provides trophic support to neurons through the IL-10 receptor. Increased tissue sparing, functional recovery, and neuroprotection are seen with an immediate post-SCI systemic administration of IL-10. Treatment of SCI with IL-10 has been used successfully in combination with Schwann cell and olfactory glial cell grafts, as well as methylprednisolone. Minocycline, tetramethylpyrazine, and hyperbaric oxygen treatment all increase IL-10 levels in a SCI models and result in increased tissue sparing and functional recovery. A chronic systemic administration of IL-10 does not appear to be beneficial to SCI recovery and causes increased susceptibility to septicemia, pneumonia, and peripheral neuropathy. However, a localized upregulation of IL-10 has been shown to be beneficial and can be achieved by herpes simplex virus gene therapy, injection of poliovirus replicons, or surgical placement of a slow-release compound. IL-10 shows promise as a treatment for SCI, although research on local IL-10 delivery timeline and dosage needs to be expanded.

Fc receptor like 3 in Chinese patients of Han nationality with Guillain-Barré syndrome

Fc receptor like 3 gene (FcRL3) has been associated with some autoimmune diseases. Here, its role in Guillain-Barré syndrome (GBS) was evaluated by studying nine FcRL3 gene SNPs in a Chinese cohort of GBS patients. The frequencies of FcRL3-3-169C, FcRL3-6 intron3A, and FcRL3-8 exon15G alleles were significantly increased in GBS patients compared with healthy controls. The frequency of FcRL3-1→9 CCTGGAGAA haplotype was significantly increased, and the frequencies of FcRL3-1→9 CCTACAAAA,CCCACGAAA, and CCTGCGGAA haplotypes were significantly decreased compared with healthy controls. These results suggest that FcRL3 is associated with GBS incidence.

Gene expression profiling in multiple sclerosis brain

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system and the leading cause of non-traumatic neurological disability in young adults in the United States and Europe. The clinical disease course is variable and starts with reversible episodes of neurological disability in the third or fourth decade of life. Microarray-based comparative gene profiling provides a snapshot of genes underlying a particular condition. Several large scale microarray studies have been conducted using brain tissue from MS patients. In this review, we summarize existing data from different gene expression profiling studies and how they relate to understand the pathogenesis of MS.

Mechanisms of neuronal dysfunction and degeneration in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. Due to its high prevalence, MS is the leading cause of non-traumatic neurological disability in young adults in the United States and Europe. The clinical disease course is variable and starts with reversible episodes of neurological disability in the third or fourth decade of life. This transforms into a disease of continuous and irreversible neurological decline by the sixth or seventh decade. Available therapies for MS patients have little benefit for patients who enter this irreversible phase of the disease. It is well established that irreversible loss of axons and neurons are the major cause of the irreversible and progressive neurological decline that most MS patients endure. This review discusses the etiology, mechanisms and progress made in determining the cause of axonal and neuronal loss in MS.

"Listening" and "talking" to neurons: implications of immune activation for pain control and increasing the efficacy of opioids

It is recently become clear that activated immune cells and immune-like glial cells can dramatically alter neuronal function. By increasing neuronal excitability, these non-neuronal cells are now implicated in the creation and maintenance of pathological pain, such as occurs in response to peripheral nerve injury. Such effects are exerted at multiple sites along the pain pathway, including at peripheral nerves, dorsal root ganglia, and spinal cord. In addition, activated glial cells are now recognized as disrupting the pain suppressive effects of opioid drugs and contributing to opioid tolerance and opioid dependence/withdrawal. While this review focuses on regulation of pain and opioid actions, such immune-neuronal interactions are broad in their implications. Such changes in neuronal function would be expected to occur wherever immune-derived substances come in close contact with neurons.

Effective treatment of experimental autoimmune neuritis with human immunoglobulin

High-dose intravenous immunoglobulin (IVIg) is an effective treatment for inflammatory demyelinating neuropathies, although the mechanism(s) of action remain incompletely understood. Experimental autoimmune neuritis (EAN) is an animal model of inflammatory demyelinating neuropathies; however, there have been conflicting reports regarding the efficacy of human IVIg in EAN. To obtain a model suitable for the study of the mechanism(s) of action of IVIg in Guillain-Barré syndrome, we investigated the effect of IVIg in EAN in the rat using clinical, electrophysiological and morphological measures. Human IVIg administered at the onset of signs of disease proved effective in preventing further progression of disease and shortening disease duration. This effectiveness was associated with significant differences in electrophysiological parameters including less prolongation of somatosensory evoked potential (S wave) latencies, better maintained S wave amplitudes, less reduction of distal motor nerve conduction velocity, and better maintained amplitudes of compound muscle action potentials of the dorsal foot muscles after stimulation at ankle and hip. Moreover, treatment with IVIg resulted in significantly lower histological grades in rat EAN. The current study provides evidence that human IVIg is effective in the treatment of EAN in the rat, indicating that this model may facilitate further investigation of the mechanism(s) of action of IVIg in inflammatory demyelinating neuropathies.

Studies of HLA associations in male and female patients with Guillain–Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)

HLA associations are found to differ with the gender of the patient in some autoimmune diseases. Here we have investigated whether there are gender-related HLA associations in Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), both of which occur more frequently in male patients than in females. In GBS, no particular HLA associations were noted, except for a slight negative association in both males and females for carriage of HLA-DR5. In CIDP, the gene frequency and the frequency of individuals positive for HLA-DR2 were greater in female patients than female controls, although this was statistically significant only for the gene frequency. Furthermore more female CIDP patients were homozygous for DR2, than male CIDP patients, or male or female controls and patients with GBS. This suggests that sex-related factors may interact with the risk associated with carriage of HLA-DR2 for development of CIDP.

Role of immune cells in animal models for inherited peripheral neuropathies

Mice expressing half of the normal dose of protein zero (P0+/- mice) or completely deficient gap-junction protein connexin 32 -/- mice mimic demyelinating forms of inherited neuropathies, such as Charcot-Marie-Tooth (CMT) neuropathies type 1B and CMT type 1X, respectively. In both models, an almost normal myelin formation is observed during the first months of life, followed by a slowly progressing demyelinating neuropathy. In both models, there is a substantial increase of CD8+ T-lymphocytes and macrophages within the demyelinating nerves. Recently, this has also been observed in mice mildly overexpressing human peripheral myelin protein 22 kD mimicking the most common form of CMT, CMT type 1A. In all demyelinating models, the macrophages show close contacts with intact myelin sheaths or demyelinated axons, suggesting an active role of these cells in myelin degeneration. Additionally, fibroblast-like cells contact macrophages, suggesting a functional role of fibroblast-like cells in macrophage activation. By cross-breeding P0+/- and gap-junction protein connexin 32-/- mice with immunodeficient recombination activating gene-1-deficient mutants, a substantial alleviation of the demyelinating phenotype was observed. Similarly, cross-breeding of P0+/- mice with mutants with a defect in macrophage activation led to an alleviated phenotype as well. These findings demonstrate that the immune system is involved in the pathogenesis of demyelinating neuropathies. In contrast, in P0-/- mice, which display a compromised myelin compaction and axonal loss from onset, immune cells appear to have a neuroprotective effect because cross-breeding with recombination activating gene-1 mutants leads to an aggravation of axonopathic changes. In the present review, we discuss the influence of the immune system on inherited de- and dysmyelination regarding disease mechanisms and possible clinical implications.

Antibodies induced by ganglioside-mimicking Campylobacter jejuni lipooligosaccharides recognise epitopes at the nodes of Ranvier

Molecular mimicry of gangliosides by Campylobacter jejuni lipooligosaccharides (LOSs) in the induction of anti-ganglioside antibodies has been hypothesised to contribute to GBS development. Rabbits were immunised with ganglioside-mimicking C. jejuni LOSs and anti-LOS responses were analysed using passive haemagglutination, and anti-ganglioside responses by enzyme-linked immunosorbent assay and thin-layer chromatography with immunostaining. High titres of anti-LOS antibodies were demonstrated in rabbit antisera that were cross-reactive with a panel of gangliosides. Non-ganglioside-mimicking C. jejuni HS:3 LOS induced a strong anti-LOS response, but no anti-ganglioside antibodies. Control rabbit antisera had no anti-LOS or -ganglioside responses. Moreover, IgG from a patient treated with parenteral gangliosides, who exhibited Guillain-Barré syndrome, had antibodies reactive with C. jejuni LOS. Biotinylated IgG fractions from the rabbit and the patient sera recognised epitopes at the nodes of Ranvier in sectioned human nerves, whereas fractions from controls did not. This study demonstrates that immunisation with ganglioside-mimicking C. jejuni LOS triggers the production of cross-reactive anti-ganglioside antibodies that recognise epitopes at the nodes of Ranvier.

Lipooligosaccharide of Campylobacter jejuni prevents myelin-specific enteral tolerance to autoimmune neuritis—a potential mechanism in Guillain-Barré syndrome?

Campylobacter jejuni-induced enteritis is the most common infection preceding Guillain-Barre syndrome (GBS), an immune-mediated polyradiculoneuritis. The acute autoimmune attack is thought to be based on C. jejuni antigens which may mimick antigens of the peripheral nervous system. Additional pathomechanisms, like disturbance of natural T cell immunoregulation by C. jejuni, have not been evaluated so far. In experimental autoimmune neuritis (EAN), a T lymphocyte-mediated animal model of human GBS, tolerance to myelin-derived autoantigens can be induced by oral feeding of the respective antigen. Here we investigated whether the lipooligosaccharide (LOS) fraction of C. jejuni may directly alter immunologic tolerance through gastrointestinal pathways. While EAN, actively induced by immunization with bovine peripheral nerve myelin could be ameliorated by precedent feeding of myelin, feeding of C. jejuni LOS along with the myelin antigen not only prevented the tolerizing effects of oral myelin but even accelerated the onset of overt EAN and augmented the myelin-specific B cell response. These findings provide evidence that LOS of C. jejuni, as produced in the gut during C. jejuni-induced enteritis, can disturb natural tolerance to definite proteins which may be or may mimic peripheral nerve antigens. In human patients this may be one of the potential mechanisms to explain why C. jejuni enteritis is a common trigger of GBS.

Antiglycolipid antibodies in Guillain-Barré syndrome and related diseases: Review of clinical features and antibody specificities

Guillain-Barré syndrome (GBS) is an acute inflammatory polyradiculoneuropathy that usually develops following a respiratory or intestinal infection. Although the pathogenic mechanisms of GBS have not been fully established, both humoral and cell-mediated immune factors have been shown to contribute to the disease process. Several antiglycosphingolipid (anti-GSL) antibodies have been found in the sera of patients with GBS or related diseases. Measurements of these antibody titers are very important in the diagnosis of GBS and in evaluating the effectiveness of treatments in clinical trials. The most common treatment strategies for these disorders involve plasmapheresis and the use of steroids for reducing anti-GSL antibody titers to ameliorate patients' clinical symptoms. Administration of intravenous immunoglobulin may also be beneficial in the treatment of neuropathies by suppressing the immune-mediated processes that are directed against antigenic targets in myelin and axons. In certain demyelinating neuropathies, the destruction or malfunctioning of the blood-nerve barrier, which results in the leakage of circulating antibodies into the peripheral nerve parenchyma, has been considered to be an initial step in development of the disease process. In addition, anti-GSL antibodies, such as anti-GM1, may cause nerve dysfunction and injury by interfering with the ion channel function at the nodes of Ranvier, where carbohydrate epitopes of glycoconjugates are located. These malfunctions thus contribute to the pathogenic mechanisms of certain demyelinating neuropathies.

Prevalence of anti-heat shock protein antibodies in cerebrospinal fluids of patients with Guillain–Barré syndrome

We examined antibodies against 10 heat shock proteins (HSPs) in cerebrospinal fluids (CSF) and sera from patients with Guillain-Barré syndrome (GBS). Significantly higher IgG antibody titers against HSP27, HSP60, HSP70 and HSP90 family, including mycobacterial HSP65 and Escherichia coli GroEL, were found in CSF from GBS patients as compared with motor neuron disease. Serum IgG antibodies against each HSP showed no difference between GBS patients and normal controls. GBS seems to be induced by reactive autoimmune responses frequently triggered by infections. The CSF antibodies against HSPs may modify the immune responses and/or cell-protective functions of HSPs in the pathophysiology of GBS.

Sensitivity and specificity of serology in determining recent acute Campylobacter infection

BACKGROUND

The measurement of serum antibodies to Campylobacter spp. has been used to investigate links between prior Campylobacter infections and the development of Guillain-Barre syndrome and its variants. Little is known of the serum antibody response to acute infections in the short- or long-term.

AIMS

The aims of the present study were to investigate the normal serum response to an acute Campylobacter infection and the sensitivity and specificity of anti-Campylobacter antibodies in determining recent Campylobacter infection.

METHODS

An enzyme-linked immunosorbent assay (ELISA) method was used to measure serum anti-Campylobacter immunoglobulin G (IgG), IgA and IgM antibodies. Controls consisted of 420 blood donors without recent gastroenteritis, 25 patients with other gastrointestinal infections, 24 patients with neurological conditions not affecting the peripheral nerves and 19 patients with autoimmune disorders. Three patient groups were assessed: 99 patients with acute Campylobacter infections, all of whom were tested 3 weeks post-infection; 69 of these patients tested 3-6 months later; and 74 additional patients tested >20 months post-infection. Western blot analysis was performed on controls and patients with high titre anti-Campylobacter antibodies to assess for cross-reactivity and specificity.

RESULTS

Following acute infections, all antibody classes rose in the majority of but not in all patients, followed by decreasing titres that did not return to baseline levels. Sixteen per cent of enteritis cases did not demonstrate a rise in titres and 9% of cases had significant levels of antibodies >20 months post-infection. The ELISA used was shown to be highly specific for the detection of Campylobacter antibodies.

CONCLUSION

The use of Campylobacter-specific antibody levels as the sole marker of prior infection is an unreliable method of determining the association between Campylobacter infection and neurological disease.

Innate murine B cells produce anti-disialosyl antibodies reactive with Campylobacter jejuni LPS and gangliosides that are polyreactive and encoded by a restricted set of unmutated V genes

In Guillain-Barré syndrome following Campylobacter enteritis, anti-lipopolysaccharide antibodies cross-react with neural gangliosides, thereby precipitating autoimmune neuropathy. We examined the properties of 15 murine anti-LPS/ganglioside mAbs specific for NeuAc(alpha2-8)NeuAc-Gal disialosyl epitopes. Many mAbs displayed features of an innate B cell origin including polyreactivity (13/15), hybridoma CD5 mRNA expression (5/15), predominance of IgM (9/15) or IgG3 (3/6) isotype, low affinity, and utilisation of unmutated VH and VL VDJ rearrangements. Antibody specificity resided in highly selective V gene usage, with 6/15 mAbs being encoded by the VH7183.3b gene. These data indicate that neuropathogenic antiganglioside autoantibodies can arise from the natural autoantibody repertoire.

The Guillain-Barré syndrome: a true case of molecular mimicry

Molecular mimicry between microbial antigens and host tissue forms an attractive hypothetical mechanism for the triggering of autoimmune disease by preceding infections. Recent crucial reviews state that molecular mimicry, as the causative mechanism, remains unproven for any human autoimmune disease. However, the peripheral neuropathy Guillain-Barré syndrome (GBS) is largely overseen in this debate. Based on recent evidence, we argue that GBS should be considered as an excellent paradigm and an attractive model for elucidation of both host and microbial aspects of molecular mimicry.

Comparison of Campylobacter jejuni isolates implicated in Guillain-Barré syndrome and strains that cause enteritis by a DNA microarray

We asked whether Campylobacter jejuni isolated from patients with Guillain-Barré syndrome (GBS) differ from isolates isolated from patients with uncomplicated gastrointestinal infection using DNA microarray analysis. We found that specific GBS genes or regions were not identified, and microarray analysis confirmed significant genomic heterogeneity among the isolates.

Anti-GM1 IgG antibodies induce leukocyte effector functions via Fcgamma receptors

Guillain-Barré syndrome (GBS) is an immune-mediated neuropathy, in which leukocytes and humoral components of the immune system proposedly initiate localized inflammation. An important pathogenic role for anti-GM1 ganglioside antibodies has been suggested. Therefore, we evaluated anti-GM1 IgG antibody-induced leukocyte effector functions such as degranulation and phagocytosis using serum of 24 GBS patients. Serum without anti-GM1 antibodies of 9 GBS patients as well as pooled serum from healthy individuals served as controls. Ten out of 15 (67%) of anti-GM1 IgG positive sera were capable of inducing leukocyte degranulation, and 8 out of 15 (53%) of anti-GM1 IgG positive sera were capable of inducing phagocytosis of GM1-coated beads. In all of these sera anti-GM1 antibody titers were >or=1:800. No leukocyte degranulation or phagocytosis was observed in control sera. Leukocyte activation was completely abrogated in the presence of IgG receptor (FcgammaR) blocking antibodies, suggesting a crucial role for leukocyte FcgammaR in GBS pathogenesis. No correlation of antibody titers with the extent of leukocyte activation, or severity of disease was observed. These data document the capacity of anti-GM1 IgG antibodies to activate leukocyte inflammatory functions, and suggest an important role for anti-ganglioside IgG antibodies in the pathogenesis of GBS.

Differential distribution of HLA-DQ beta/DR beta epitopes in the two forms of Guillain-Barré syndrome, acute motor axonal neuropathy and acute inflammatory demyelinating polyneuropathy (AIDP): identification of DQ beta epitopes associated with susceptibility to and protection from AIDP

Guillain-Barré syndrome (GBS), an acute, immune-mediated paralytic disorder affecting the peripheral nervous system, is the most common cause of acute flaccid paralysis in the post-polio era. GBS is classified into several subtypes based on clinical and pathologic criteria, with acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN) being the most common forms observed. To better understand the pathogenesis of GBS and host susceptibility to developing the disease, the distribution of HLA class II Ags along with the seroreactivity to Campylobacter jejuni were investigated in a population of GBS patients from northern China. Using DNA-based typing methods, 47 patients with AMAN, 25 patients with AIDP, and 97 healthy controls were studied for the distribution of class II alleles. We found that the DQ beta RLD(55-57)/ED(70-71) and DR beta E(9)V(11)H(13) epitopes were associated with susceptibility to AIDP (p = 0.009 and p = 0.004, respectively), and the DQ beta RPD(55-57) epitope was associated with protection (p = 0.05) from AIDP. These DQ beta/DR beta positional residues are a part of pockets 4 (DQ beta 70, 71, DR beta 13), 6 (DR beta 11), and 9 (DQ beta 56, 57, DR beta 9); have been demonstrated to be important in peptide binding and T cell recognition; and are associated with other diseases that have a pathoimmunological basis. Class II HLA associations were not identified with AMAN, suggesting a different immunological mechanism of disease induction in the two forms of GBS. These findings provide immunogenetic evidence for differentiating the two disease entities (AMAN and AIDP) and focuses our attention on particular DR beta/DQ beta residues that may be instrumental in understanding the pathophysiology of AIDP.

Campylobacter jejuni O:19 serotype-associated Guillain-Barré syndrome in a child: the first case reported from Greece

We present a case of Guillain-Barré syndrome (GBS) following Campylobacter jejuni HS serotype O:19 infection in a child. Antibodies against C. jejuni and autoantibodies to the peripheral nerve gangliosides GM1 were positive, a pattern correlating well with the existence of an inflammatory neuropathy like GBS. The patient shared the HLA-B35 and HLA-DR8 antigens, which have been found to be increased in GBS patients with previous C. jejuni infection. As this is the first diagnosed C. jejuni-associated GBS case reported from Greece, further clinical and epidemiologic investigations are warranted.

Antibodies to L-periaxin in sera of patients with peripheral neuropathy produce experimental sensory nerve conduction deficits

L-Periaxin is a PDZ-domain protein localized to the plasma membrane of myelinating Schwann cells and plays a key role in the stabilization of mature myelin in peripheral nerves. Mutations in L-periaxin have recently been described in some patients with demyelinating peripheral neuropathy, suggesting that disruption of L-periaxin function may result in nerve injury. In this study, we report the presence of autoantibodies to L-periaxin in sera from two of 12 patients with diabetes mellitus (type 2)-associated neuropathy and three of 17 patients with IgG monoclonal gammopathy of undetermined significance (MGUS) neuropathy, an autoimmune peripheral nerve disorder. By comparison, anti-L-periaxin antibodies were not present in sera from nine patients with IgM MGUS neuropathy or in sera from 10 healthy control subjects. The effect of anti-L-periaxin serum antibody on peripheral nerve function was tested in vivo by intraneural injection. Sera containing anti-L-periaxin antibody, but not sera from age-matched control subjects, injected into the endoneurium of rat sciatic nerve significantly (p < 0.005, n = 3) attenuated sensory-evoked compound muscle action potential (CMAP) amplitudes in the absence of temporal dispersion. In contrast, motor-evoked CMAP amplitudes and latencies were not affected by intraneural injection of sera containing anti-L-periaxin antibody. Light and electron microscopy of anti-L-periaxin serum-injected nerves showed morphologic evidence of demyelination and axon enlargement. Depleting sera of anti-L-periaxin antibodies neutralized the serum-mediated effects on nerve function and nerve morphology. Together, these data support anti-L-periaxin antibody as the pathologic agent in these serum samples. We suggest that anti-L-periaxin antibodies, when present in sera of patients with IgG MGUS- or diabetes-associated peripheral neuropathy, may elicit sensory nerve conduction deficits.

Beyond neurons: evidence that immune and glial cells contribute to pathological pain states

Chronic pain can occur after peripheral nerve injury, infection, or inflammation. Under such neuropathic pain conditions, sensory processing in the affected body region becomes grossly abnormal. Despite decades of research, currently available drugs largely fail to control such pain. This review explores the possibility that the reason for this failure lies in the fact that such drugs were designed to target neurons rather than immune or glial cells. It describes how immune cells are a natural and inextricable part of skin, peripheral nerves, dorsal root ganglia, and spinal cord. It then examines how immune and glial activation may participate in the etiology and symptomatology of diverse pathological pain states in both humans and laboratory animals. Of the variety of substances released by activated immune and glial cells, proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) appear to be of special importance in the creation of peripheral nerve and neuronal hyperexcitability. Although this review focuses on immune modulation of pain, the implications are pervasive. Indeed, all nerves and neurons regardless of modality or function are likely affected by immune and glial activation in the ways described for pain.

Tolerance to self gangliosides is the major factor restricting the antibody response to lipopolysaccharide core oligosaccharides in Campylobacter jejuni strains associated with Guillain-Barré syndrome

Guillain-Barré syndrome following Campylobacter jejuni infection is frequently associated with anti-ganglioside autoantibodies mediated by molecular mimicry with ganglioside-like oligosaccharides on bacterial lipopolysaccharide (LPS). The regulation of antibody responses to these T-cell-independent antigens is poorly understood, and only a minority of Campylobacter-infected individuals develop anti-ganglioside antibodies. This study investigates the response to gangliosides and LPS in strains of mice by using a range of immunization strategies. In normal mice following intraperitoneal immunization, antibody responses to gangliosides and LPS are low level but can be enhanced by the antigen format or coadministration of protein to recruit T-cell help. Class switching from the predominant immunoglobulin M (IgM) response to IgG3 occurs at low levels, suggesting B1-cell involvement. Systemic immunization results in poor responses. In GalNAc transferase knockout mice that lack all complex gangliosides and instead express high levels of GM3 and GD3, generation of anti-ganglioside antibodies upon immunization with either complex gangliosides or ganglioside-mimicking LPS is greatly enhanced and exhibits class switching to T-cell-dependent IgG isotypes and immunological memory, indicating that tolerance to self gangliosides is a major regulatory factor. Responses to GD3 are suppressed in knockout mice compared with wild-type mice, in which responses to GD3 are induced specifically by GD3 and as a result of polyclonal B-cell activation by LPS. The anti-ganglioside response generated in response to LPS is also dependent on the epitope density of the ganglioside mimicked and can be further manipulated by providing secondary signals via lipid A and CD40 ligation.

Autoantibodies to amphiphysin I and amphiphysin II in a patient with sensory-motor neuropathy

A proportion of patients with peripheral neuropathies has circulating autoantibodies directed against neural antigens. In some cases, autoantibodies may play a pathogenic role. We studied a patient with a progressive sensory-motor axonal neuropathy of unknown etiology, looking for circulating autoantibodies against neural antigens and we showed that the patient's serum contained anti-amphiphysin I (AMP I) and amphiphysin II (AMP II) autoantibodies. A sural nerve biopsy revealed an axonal neuropathy. Indirect immunofluorescence experiments with the patient's serum showed a staining of rat axons due to alpha-AMP I autoantibodies and a specific labelling of cytoplasm and Schmidt-Lanterman incisures of Schwann cells due to alpha-AMP II autoantibodies. In conclusion we identified a patient affected by a sensory-motor neuropathy with autoantibodies against both AMP I and AMP II.

Intravenous immunoglobulins neutralize blocking antibodies in Guillain-Barré syndrome

Intravenous immunoglobulin (IVIg) treatment ameliorates the course of Guillain-Barré syndrome (GBS), but its specific mode of action is unknown. We attempted to delineate the effect of IVIg on neuromuscular blocking antibodies in GBS. A total of seven GBS serum samples were examined for blocking antibodies and the effect of IVIg with a macro-patch-clamp technique in mouse hemidiaphragms. First, serum was tested before and after treatment with IVIg. Second, we investigated with coincubation experiments whether the IVIg was capable of neutralizing neuromuscular blocking antibodies in GBS serum or affinity-purified immunoglobulin G (IgG) fractions. Finally, the mechanism of the neutralizing effect was studied by the coincubation of active blocking GBS IgG with Fab and Fc fragments prepared from IVIg. All GBS sera (two adults and two children) and GBS IgG fractions (three adults) taken before treatment with IVIg blocked evoked quantal release by approximately 90%. Blocking activity was markedly reduced in sera obtained after treatment with IVIg. Coincubation of the pretreatment blocking serum with the posttreatment serum, or with the IVIg preparation used for treatment, reduced the blocking activity of the pretreatment GBS serum. When GBS IgG was coincubated with IVIg, the blocking activity of GBS IgG was diminished dose-dependently. Monovalent and divalent Fab fragments prepared from the IVIg were as effective as whole IVIg, but Fc fragments were ineffective. Therapeutic IVIg is capable of neutralizing neuromuscular blocking antibodies in GBS by a dose-dependent, antibody-mediated mechanism. This may, in part, explain its therapeutic efficacy.

Elevated serum titers of proinflammatory cytokines and CNS autoantibodies in patients with chronic spinal cord injury

This study characterized the proinflammatory cytokines, interleukin-2 (IL-2) and tumor necrosis factor alpha (TNFalpha), the antiinflammatory cytokines, IL-4 and IL-10, autoantibodies specific for GM1 ganglioside (anti-GM1), IgG and IgM, and myelin-associated glycoprotein (anti-MAG), in the sera of infection-free, chronic (>12 months), traumatically injured SCI patients (n = 24). Healthy able-bodied subjects (n = 26) served as controls. The proinflammatory cytokines and anti-GM1 antibodies were of particular interest as they have been implicated in an autoimmune "channelopathy" component to central and peripheral conduction deficits in various chronic neuroinflammatory diseases. Antibody and cytokine titers were established using enzyme-linked immunosorbent assays (ELISA). The mean anti-GM(1) (IgM) titer value for the SCI group was significantly higher (p < 0.05) than controls. The SCI group also demonstrated significantly higher titers (p < 0.05) of IL-2 and TNF alpha than controls. No differences were found between the SCI group and control group mean levels of IL-4 or IL-10. Overall, the serum of 57% of SCI patients contained increased levels of autoantibodies or proinflammatory cytokines relative to control values. These results provide preliminary support for the hypothesis that chronic immunological activation in the periphery occurs in a subpopulation of chronic SCI patients. It remains to be established whether elevated serum titers of proinflammatory cytokines and autoantibodies against GM1 are beneficial to the patients or whether they are surrogate markers of a channelopathy that compounds the neurological impairment associated with traumatic axonopathy or myelinopathy.

Immune mechanisms in acquired demyelinating neuropathies: lessons from animal models

The peripheral nervous system (PNS) is the target for a heterogenous immune attack mediated by T-cells, B-cells, and macrophages. The interaction of the humoral and cellular immune system with the structural components in the peripheral nervous system may determine the extent of inflammation and possibly repair mechanisms. The animal model experimental autoimmune neuritis (EAN) allows detailed study of the various effector pathways and tests novel therapeutic strategies in vivo. Unexpectedly, involvement of the immune system is also found in animal models for inherited neuropathies and in its human counterpart Charcot-Marie-Tooth (CMT) disease, suggesting an autoimmune reaction triggered by the genetically determined demyelinating disorder. A better understanding of immune regulation and its failure in the peripheral nervous system may help to develop more specific and more effective immunotherapies.

Chronic effects of Campylobacter infection

Campylobacter jejuni is one of the most common causes of bacterial gastroenteritis and chronic sequelae, such as reactive arthritis and Guillain-Barré syndrome (GBS), are known to follow uncomplicated infections. While little is known about reactive arthritis following Campylobacter infection, our knowledge on the pathogenesis of Campylobacter-induced GBS is expanding rapidly and is summarized in this review.

Role of immune cells in animal models for inherited neuropathies: facts and visions

Mice heterozygously deficient in the peripheral myelin adhesion molecule P0 (P0+/- mice) are models for some forms of Charcot-Marie-Tooth (CMT) neuropathies. In addition to the characteristic hallmarks of demyelination, elevated numbers of CD8-positive T-lymphocytes and F4/80-positive macrophages are striking features in the nerves of these mice. These immune cells increase in number with age and progress of demyelination, suggesting that they might be functionally related to myelin damage. In order to investigate the pathogenetic role of lymphocytes, the myelin mutants were cross-bred with recombination activating gene 1 (RAG-1)-deficient mice, which lack mature T- and B-lymphocytes. The immunodeficient myelin mutants showed a less severe myelin degeneration. The beneficial effect of lymphocyte-deficiency was reversible, since demyelination worsened in immunodeficient myelin-mutants when reconstituted with bone marrow from wild-type mice. Ultrastructural analysis revealed macrophages in close apposition to myelin and demyelinated axons. We therefore cross-bred the P0+/- mice with spontaneous osteopetrotic (op) mutants deficient in the macrophage colony-stimulating factor (M-CSF), hence displaying impaired macrophage activation. In the corresponding double mutants the numbers of macrophages were not elevated in the peripheral nerves, and the demyelinating phenotype was less severe than in the genuine P0+/- mice, demonstrating that macrophages are also functionally involved in the pathogenesis of genetically mediated demyelination. We also examined other models for inherited neuropathies for a possible involvement of immune cells. We chose mice deficient in the gap junction component connexin 32, a model for the X-linked form of CMT. Similar to P0-deficient mice, T-lymphocytes and macrophages were elevated and macrophages showed a close apposition to degenerating myelin. We conclude that the involvement of T-lymphocytes and macrophages is a common pathogenetic feature in various forms of slowly progressive inherited neuropathies.

Immunoglobulin G-class mouse monoclonal antibodies to major brain gangliosides

Mice genetically engineered to lack complex gangliosides are improved hosts for raising antibodies against those gangliosides. We report the generation and characterization of nine immunoglobulin G (IgG)-class monoclonal antibodies (mAbs) raised against the four major brain gangliosides in mammals. These include (designated as ganglioside specificity-IgG subclass) two anti-GM1 mAbs (GM1-1, GM1-2b), three anti-GD1a mAbs (GD1a-1, GD1a-2a, GD1a-2b), one anti-GD1b mAb (GD1b-1), and three anti-GT1b mAbs (GT1b-1, GT1b-2a, GT1b-2b). Each mAb demonstrated high specificity, with little or no cross-reactivity with other major brain gangliosides. Enzyme-linked immunosorbent assay (ELISA) screening against 14 closely related synthetic and purified gangliosides confirmed the high specificity, with no significant cross-reactivity except that of the anti-GD1a mAbs for the closely related minor ganglioside GT1a alpha. All of the mAbs were useful for ELISA, TLC immunooverlay, and immunocytochemistry. Neural cells from wild-type rats and mice were immunostained to differing levels with the anti-ganglioside antibodies, whereas neural cells from mice engineered to lack complex gangliosides (lacking the ganglioside-specific biosynthetic enzyme UDP-GalNAc:GM3/GD3 N-acetylgalactosaminyltransferase) remained unstained, demonstrating that most of the mAbs react only with gangliosides and not with related structures on glycoproteins. These mAbs may provide useful tools for delineation of the expression and function of the major brain gangliosides and for probing the pathology of anti-ganglioside autoimmune diseases.

Antibodies against gangliosides: a link between preceding infection and immunopathogenesis of Guillain-Barré syndrome

Autoantibodies against gangliosides GM1 and GQ1b, characteristic cell surface glycolipids of the nervous system, are present in specific clinical types of GuillainBarré syndrome (GBS). Close associations of anti-GM1 with acute motor axonal neuropathy, and of anti-GQ1b with Miller Fisher syndrome, strongly suggest that these antibodies contribute to neuropathy pathogenesis. Immune responses against gangliosides are suspected to originate as a result of molecular mimicry between gangliosides and lipopolysaccharides of Campylobacter jejuni, the most frequent infectious trigger of GBS. Thus, antibodies against gangliosides may link C. jejuni infection with the precipitation of neurological disease.

Characterization of a phospholipid antigen reacting with serum antibody in patients with peripheral neuropathies and paraproteinemia

A phospholipid antigen that reacted with the serum antibody from a patient with peripheral neuropathy and paraproteinemia with both impaired sensory and motor functions, but not with sera from patients with only impaired sensory functions and healthy controls, was purified from bovine cauda equina as a minor component with a concentration of about 0.6 microg per gram wet-weight tissue. The structure of the phospholipid was characterized as lysophosphatidylinositol by means of thin-layer chromatography, gas-liquid chromatography, and negative-ion fast-atom-bombardment mass spectrometry. The major fatty acid component of this phospholipid was stearic acid (> 81%). Our data suggest the possible involvement of a lysophospholipid antigen in the immunopathogenesis of peripheral neuropathies with severe motor and sensory dysfunctions. There is an intriguing possibility that the difference in immunoreactivity of serum antibodies may underlie the differential clinical manifestations in patients with peripheral neuropathy and paraproteinemia.

Bone marrow transfer from wild-type mice reverts the beneficial effect of genetically mediated immune deficiency in myelin mutants

Inherited demyelinating neuropathies are chronically disabling human disorders caused by various genetic defects, including deletions, single site mutations, and duplications in the respective myelin genes. We have shown in a mouse model of one distinct hereditary demyelinating neuropathy (heterozygous P0-deficiency, P0+-) that an additional null mutation in the recombination activating gene-1 (RAG-1--) leads to a substantially milder disorder, indicating a disease modifying role of T-lymphocytes. In the present study, we addressed the role of lymphocytes in the mouse model by reconstituting bone marrow of P0+-/RAG-1-- mice with bone marrow from immunocompetent wild-type mice. We compared the pathology and nerve conduction in double mutant mice (P0+-/RAG-1-- on a C57BL/6 background) with that in double mutants after receiving a bone marrow transplant. We found that the milder demyelination seen in the lymphocyte-deficient P0+-/RAG-1-- mutants was reverted to the more severe pathology by reestablishing a competent immune system by bone marrow transfer. These data corroborate the concept that the immune system contributes substantially to the pathologic process in this mouse model and may open new avenues to ameliorate human hereditary neuropathies by exploiting immunosuppressive treatments.

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.

Role of integrins in the peripheral nervous system

Integrins, a subgroup of adhesion receptors, are transmembrane glycoproteins that mediate interactions between cytoplasm and the extracellular environment. These interactions influence, among others, events such as cell migration, proliferation, and differentiation. Differential expression of integrins is developmentally regulated in the peripheral nervous system (PNS) and is associated with crucial events in both physiological and pathological processes. Preliminary studies suggest that integrin expression influences neural crest cell migration, axonal outgrowth, and Schwann cell differentiation. Similarly, the abnormal expression of integrins or their ligands, is associated with degenerative, inflammatory, and malignant disorders of the PNS. Finally, integrins participate in the complex interactions that promote repair of the PNS. A better comprehension of the role of integrins in the PNS, their protein interactions and transducing signals is being achieved by selected biochemical and genetic experiments. Here we review a large bias of evidence suggesting the key functions for integrins in the PNS.