Accumulation of immunoglobulin across the 'blood-nerve barrier' in spinal roots in adoptive transfer experimental autoimmune neuritis

NF1-dependent disruption of the blood-nerve-barrier is improved by blockade of P2RY14

The blood-nerve-barrier (BNB) that regulates peripheral nerve homeostasis is formed by endoneurial capillaries and perineurial cells surrounding the Schwann cell (SC)-rich endoneurium. Barrier dysfunction is common in human tumorigenesis, including in some nerve tumors. We identify barrier disruption in human NF1 deficient neurofibromas, which were characterized by reduced perineurial cell glucose transporter 1 (GLUT1) expression and increased endoneurial fibrin(ogen) deposition. Conditional Nf1 loss in murine SCs recapitulated these alterations and revealed decreased tight junctions and decreased caveolin-1 (Cav1) expression in mutant nerves and in tumors, implicating reduced Cav1-mediated transcytosis in barrier disruption and tumorigenesis. Additionally, elevated receptor tyrosine kinase activity and genetic deletion of Cav1 increased endoneurial fibrin(ogen), and promoted SC tumor formation. Finally, when SC lacked Nf1, genetic loss or pharmacological inhibition of P2RY14 rescued Cav1 expression and barrier function. Thus, loss of Nf1 in SC causes dysfunction of the BNB via P2RY14-mediated G-protein coupled receptor (GPCR) signaling.

The pathophysiological role of endoneurial inflammatory edema in early classical Guillain-Barré syndrome

The objective of this review was to analyze the pathophysiological role of endoneurial inflammatory edema in initial stages of classic Guillain-Barré syndrome (GBS), arbitrarily divided into very early GBS (≤ 4 days after symptom onset) and early GBS (≤ 10 days). Classic GBS, with variable degree of flaccid and areflexic tetraparesis, encompasses demyelinating and axonal forms. Initial autopsy studies in early GBS have demonstrated that endoneurial inflammatory edema of proximal nerve trunks, particularly spinal nerves, is the outstanding lesion. Variable permeability of the blood-nerve barrier dictates such lesion topography. In proximal nerve trunks possessing epi-perineurium, edema may increase the endoneurial fluid pressure causing ischemic changes. Critical analysis the first pathological description of the axonal form GBS shows a combination of axonal degeneration and demyelination in spinal roots, and pure Wallerian-like degeneration in peripheral nerve trunks. This case might be reclassified as demyelinating GBS with secondary axonal degeneration. Both in acute motor axonal neuropathy and acute motor-sensory axonal neuropathy, Wallerian-like degeneration of motor fibers predominates in the distal part of ventral spinal roots abutting the dura mater, another feature re-emphasizing the pathogenic relevance of this area. Electrophysiological and imaging studies also point to a predominant alteration at the spinal nerve level, which is a hotspot in any early GBS subtype. Serum biomarkers of axonal damage, including neurofilament light chain and peripherin, are increased in the great majority of patients with any early GBS subtype; endoneurial ischemia of proximal nerve trunks could contribute to such axonal damage. It is concluded that inflammatory edema of proximal nerve trunks is an essential pathogenic event in early GBS, which has a tangible impact for accurate approach to the disease.

A novel algorithm to calculate elementary modes: Analysis of Campylobacter jejuni metabolism

We describe a novel algorithm, 'LPEM', that given a steady-state flux vector from a (possibly genome-scale) metabolic model, decomposes that vector into a set of weighted elementary modes such that the sum of these elementary modes is equal to the original flux vector. We apply the algorithm to a genome scale metabolic model of the human pathogen Campylobacter jejuni. This organism is unusual in that it has an absolute growth requirement for oxygen, despite being able to operate the electron transport chain anaerobically. We conclude that (1) Microaerophilly in C. jejuni can be explained by the dependence of pyridoxine 5'-phosphate oxidase for the synthesis of pyridoxal 5'- phosphate (the biologically active form of vitamin B6), (2) The LPEM algorithm is capable of determining the elementary modes of a linear programming solution describing the simultaneous production of 51 biomass precursors, (3) Elementary modes for the production of individual biomass precursors are significantly more complex when all others are produced simultaneously than those for the same product in isolation and (4) The sum of elementary modes for the production of all precursors in isolation requires a greater number of reactions and overall total flux than the simultaneous production of all precursors.

COVID-19 as a trigger of Guillain-Barré syndrome: A review of the molecular mechanism

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a pandemic with serious complications. After coronavirus disease 2019 (COVID-19), several post-acute COVID-19 syndromes (PACSs) and long-COVID sequels were reported. PACSs involve many organs, including the nervous, gustatory, and immune systems. One of the PACSs after SARS-CoV-2 infection and vaccination is Guillain-Barré syndrome (GBS). The incidence rate of GBS after SARS-CoV-2 infection or vaccination is low. However, the high prevalence of COVID-19 and severe complications of GBS, for example, autonomic dysfunction and respiratory failure, highlight the importance of post-COVID-19 GBS. It is while patients with simultaneous COVID-19 and GBS seem to have higher admission rates to the intensive care unit, and demyelination is more aggressive in post-COVID-19 GBS patients. SARS-CoV-2 can trigger GBS via several pathways like direct neurotropism and neurovirulence, microvascular dysfunction and oxidative stress, immune system disruption, molecular mimicry, and autoantibody production. Although there are few molecular studies on the molecular and cellular mechanisms of GBS occurrence after SARS-CoV-2 infection and vaccination, we aimed to discuss the possible pathomechanism of post-COVID-19 GBS by gathering the most recent molecular evidence.

Campylobacter jejuni Infection, Anti-Ganglioside Antibodies, and Neuropathy

Preceding infection with Campylobacter jejuni (Cj) occurs in approximately 30% of patients with Guillain–Barre syndrome (GBS), and the risk of GBS following Cj infection is increased by 77 to 100-fold. GBS is most often of the axonal subtype and is thought to be mediated by IgG antibodies to peripheral nerve gangliosides that are cross reactive with oligosaccharides in the Cj lipopolysaccharides (LPS). The antibodies are thought to be induced by molecular mimicry, where immune reactivity to a cross reactive epitope in the infectious organism and normal tissue can cause autoimmune disease. Clonally restricted IgM antibodies that react with the same oligosaccharides in gangliosides and Cj-LPS are associated with chronic neuropathies of otherwise similar phenotypes. The anti-ganglioside antibodies in GBS are of the IgG1 and IgG3 subclasses, indicating T-cell reactivity to the same antigens that could help disrupt the blood–nerve barrier. Cj infection can activate multiple innate and adoptive pro-inflammatory pathways that can overcome immune tolerance and induce autoimmunity. Elucidation of the specific immune mechanisms involved in the development of the autoantibodies and neuropathy would help our understanding of the relation between infection and autoimmunity and aid in the development of more effective preventive interventions and therapies.

Inflammatory oedema of nerve trunks may be pathogenic in very early Guillain-Barré syndrome

The aim of this paper is to analyse the pathological background of very early Guillain-Barré (VEGBS) (≤ 4 days after onset) comparing it with initial stages of experimental autoimmune neuritis (EAN). The pathological hallmark of VEGBS is inflammatory oedema predominating in proximal nerve trunks. In EAN inflammatory oedema precedes the development of demyelination or axonal degeneration; such oedema may increase endoneurial fluid pressure (EFP) stretching the perineurium and constricting the transperineurial microcirculation. Centrofascicular or wedge-shaped areas of nerve ischemia have been reported in GBS and EAN. Additional support for proximal VEGBS pathology comes from electrophysiology showing alterations in late responses as the most frequent features, and ultrasonography illustrating that main changes rely on ventral rami of spinal nerves. Selective inefficiency of the blood-nerve barrier would explain the topography of changes in VEGBS. Increased serum neurofilament light chain concentration has recently been reported in VEGBS, with no difference between demyelinating and axonal subtypes. This is a marker of axonal damage, which could be correlated with endoneurial ischemia caused by increased EFP. Inflammatory oedema of proximal nerve trunks may be pathogenic in VEGBS, and consequently there is a pressing need for therapeutic strategies to stop its rapid impact on the axons.

Axonal degeneration in Guillain-Barré syndrome: a reappraisal

The aim of this review was to analyse the pathophysiology of axonal degeneration in Guillain-Barré syndrome (GBS) with emphasis on early stages (≤ 10 days after onset). An overview of experimental autoimmune neuritis (EAN) models is provided. Originally GBS and acute inflammatory demyelinating polyneuropathy were equated, presence of axonal degeneration being attributed to a "bystander" effect. Afterwards, primary axonal GBS forms were reported, designated as acute motor axonal neuropathy/acute motor-sensory axonal neuropathy. Revision of the first pathological description of axonal GBS indicates the coexistence of active axonal degeneration and demyelination in spinal roots, and pure Wallerian-like degeneration in peripheral nerve trunks. Nerve conduction studies are essential for syndrome subtyping, though their sensitivity is scanty in early GBS. Serum markers of axonal degeneration include increased levels of neurofilament light chain and presence of anti-ganglioside reactivity. According to nerve ultrasonographic features and autopsy studies, ventral rami of spinal nerves are a hotspot in early GBS. In P₂-induced EAN models, the initial pathogenic change is inflammatory oedema of spinal roots and sciatic nerve, which is followed by demyelination, and Wallerian-like degeneration in nerve trunks possessing epi-perineurium; a critical elevation of endoneurial fluid pressure is a pre-requisite for inducing ischemic axonal degeneration. Similar lesion topography may occur in GBS. The repairing role of adaxonal Schwann cytoplasm in axonal degeneration is analysed. A novel pathophysiological mechanism for nerve trunk pain in GBS, including pure motor forms, is provided. The potential therapeutic role of intravenous boluses of methylprednisolone for early severe GBS and intractable pain is argued.

Very early Guillain-Barré syndrome: A clinical-electrophysiological and ultrasonographic study

Objectives

Using recent optimized electrodiagnostic criteria sets, we primarily aimed at verifying the accuracy of the initial electrophysiological test in very early Guillain-Barré syndrome (VEGBS), ≤4 days of onset, compared with the results of serial electrophysiology. Our secondary objective was to correlate early electrophysiological results with sonographic nerve changes.

Methods

This is a retrospective study based on consecutive VEGBS patients admitted to the hospital. Each patient had serial nerve conduction studies (NCS) in at least 4 nerves. Initial NCS were done within 4 days after onset, and serial ones from the second week onwards. Electrophysiological recordings of each case were re-evaluated, GBS subtype being established accordingly. Nerve ultrasonography was almost always performed within 2 weeks after onset.

Results

Fifteen adult VEGBS patients were identified with a mean age of 57.8 years. At first NCS, VEGBS sub-typing was only possible in 3 (20%) cases that showed an axonal pattern, the remaining patterns being mixed (combining axonal and demyelinating features) in 6 (40%), equivocal in 5 (33.3%), and normal in 1 (6.7%). Upon serial NCS, 7 (46.7%) cases were categorized as acute demyelinating polyneuropathy, 7 (46.7%) as axonal GBS, and 1 (6.6%) as unclassified syndrome. Antiganglioside reactivity was detected in 5 out of the 7 axonal cases. Nerve US showed that lesions mainly involved the ventral rami of scanned cervical nerves.

Conclusions

Serial electrophysiological evaluation is necessary for accurate VEGBS subtype classification. Ultrasonography helps delineate the topography of nerve changes.

Significance

We provide new VEGBS pathophysiological insights into nerve conduction alterations within the first 4 days of the clinical course.

In situ molecular characterization of endoneurial microvessels that form the blood-nerve barrier in normal human adult peripheral nerves

The blood-nerve barrier (BNB) formed by tight junction-forming endoneurial microvessels located in the innermost compartment of peripheral nerves, and the perineurium serve to maintain the internal microenvironment required for normal signal transduction. The specific molecular components that define the normal adult human BNB are not fully known. Guided by data derived from the adult human BNB transcriptome, we evaluated the in situ expression of 25 junctional complex, transporter, cell membrane, and cytoskeletal proteins in four histologically normal adult sural nerves by indirect fluorescent immunohistochemistry to determine proteins specifically expressed by restrictive endoneurial microvascular endothelium. Using Ulex Europaeus Agglutinin-1 expression to detect endothelial cells, we ascertained that the selected proteins were uniformly expressed in ≥90% of endoneurial microvessels. P-glycoprotein (also known as adenosine triphosphate-binding cassette subfamily B member 1) and solute carrier family 1 member 1 demonstrated restricted expression by endoneurial endothelium only, with classic tight junction protein claudin-5 also expressed on fenestrated epineurial macrovessels, and vascular-specific adherens junction protein cadherin-5 also expressed by the perineurium. The expression profiles of the selected proteins provide significant insight into the molecular composition of normal adult peripheral nerves. Further work is required to elucidate the human adult BNB molecular signature in order to better understand its development and devise strategies to restore function in peripheral neuropathies.

Time Course of Axon and Myelin Degeneration in Peripheral Nerves in Experimental Autoimmune Neuritis Rats

Experimental autoimmune neuritis (EAN) is an animal model for Guillain-Barré syndrome (GBS), which results in neurological symptoms and histopathological changes in peripheral nerves. In this model, the correlation between the progression of the disease and the histopathological changes is not clear. To further examine histopathological changes in peripheral nerves in EAN rats, sciatic nerves were sampled at onset (day 10), peak (day 16), and recovery (days 22 and 25) of neurological symptoms in P2(57-81)-peptide-administered rats. Axon and myelin degeneration was observed by light microscopy at onset, degeneration became severe at peak, and persisted at recovery. Densities of myelinated nerve fibers and myelin areas decreased from day 10 to a minimum on day 22. Slight axon and myelin degeneration, such as accumulation of vesicles in axons and focal myelin splitting and folding, was observed by transmission electron microscopy at onset; severe degeneration, such as axonal loss, myelin ovoid, and demyelination, increased at peak; and regenerative changes, such as remyelination and enlargement of Schwann cell cytoplasm, occurred at recovery. These results suggest that EAN rats have histopathological similarities to some types of GBS patients and that EAN rats are a useful model to understand the pathogenesis of GBS.

Relationship Between Cerebrospinal Fluid Protein Levels and Electrophysiologic Abnormalities in Guillain-Barré Syndrome

OBJECTIVES

The cerebrospinal fluid (CSF) protein level is known to be elevated in patients with Guillain-Barré syndrome (GBS). This report correlates the degree of CSF protein elevation with the number of electrophysiologic abnormalities on nerve conduction study (NCS).

METHODS

We reviewed 38 patients admitted to our institution with a diagnosis of GBS and had both a measured CSF protein level and a NCS within 24 hours of each other.

RESULTS

CSF protein level correlates with the number of NCS demyelination criteria, as described by Cornblath, in patients with GBS.

CONCLUSIONS

This retrospective study is the first to demonstrate a relationship between the CSF protein level and the electrophysiologic abnormalities that accompany GBS.

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

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

Mesenchymal stem cells lack efficacy in the treatment of experimental autoimmune neuritis despite in vitro inhibition of T-cell proliferation

Mesenchymal stem cells have been demonstrated to ameliorate experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis, prompting clinical trials in multiple sclerosis which are currently ongoing. An important question is whether this therapeutic effect generalises to other autoimmune neurological diseases. We performed two trials of efficacy of MSCs in experimental autoimmune neuritis (EAN) in Lewis (LEW/Han (M)Hsd) rats, a model of human autoimmune inflammatory neuropathies. No differences between the groups were found in clinical, histological or electrophysiological outcome measures. This was despite the ability of mesenchymal stem cells to inhibit proliferation of CD4+ T-cells in vitro. Therefore the efficacy of MSCs observed in autoimmune CNS demyelination models do not necessarily generalise to the treatment of other forms of neurological autoimmunity.

Pathogenesis and treatment of immune-mediated neuropathies

Immune-mediated neuropathies represent a heterogeneous spectrum of peripheral nerve disorders that can be classified according to time course, predominant involvement of motor/sensory fibers, distribution of deficits and paraclinical parameters such as electrophysiology and serum antibodies. In the last few years, significant advances have been achieved in elucidating underlying pathomechanisms, which made it possible to identify potential therapeutic targets. In this review, we discuss the latest development in pathogenesis and treatment of immune-mediated neuropathies.

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

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

Induction of experimental ataxic sensory neuronopathy in cats by immunization with purified SGPG

IgM paraproteins in about 50% of the patients with neuropathy associated with IgM gammopathy react with carbohydrate moieties in myelin-associated glycoprotein (MAG) and in sulfated glucuronic glycolipids (SGGLs) in human peripheral nerves. However, the role of anti-MAG/SGGL antibodies in the pathogenesis of neuropathy remains unclear. In order to induce an animal model of neuropathy associated with anti-MAG/SGGL antibodies, cats were immunized with sulfoglucuronyl paragloboside (SGPG). All four cats immunized with SGPG developed clinical signs of sensory neuronopathy within 11 months after initial immunization, characterized by unsteadiness, falling, hind limb weakness and ataxia. In two cats the ataxia and hind limb paralysis were so severe that the animals had to be euthanized. Pathological examination revealed sensory ganglionitis with inflammatory infiltrates in the dorsal root ganglia. No overt signs of pathology were noted in the examined roots or nerves. High titer anti-SGPG/MAG antibodies were detected in all 4 cats immunized with SGPG but not in 3 control cats. Our data demonstrate that immunization of cats with SGPG induced anti-SGPG antibodies and sensory neuronopathy clinically resembling the sensory ataxia of patients with monoclonal IgM anti-MAG/SGPG antibodies. This study suggests that these anti-MAG/SGPG antibodies play a role in the pathogenesis of this neuropathy.

From bench to bedside--experimental rationale for immune-specific therapies in the inflamed peripheral nerve

Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy are autoimmune-mediated inflammatory diseases of the PNS. In recent years, substantial progress has been made towards understanding the immune mechanisms that underlie these conditions, in large part through the study of experimental models. Here, we review the available animal models that partially mimic human Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy, and discuss the wide range of therapeutic approaches that have been successfully established in these models of inflammatory neuropathies. Transfer of this preclinical knowledge to patients has been far less successful, and inflammatory neuropathies are still associated with significant morbidity and mortality. We will summarize successful therapeutic trials in human autoimmune neuropathies to provide a vantage point for the transfer of experimental treatment strategies to clinical practice in immune-mediated diseases of the peripheral nerve.

Anti-ganglioside antibodies and elevated CSF IgG levels in Guillain-Barré syndrome

Anti-ganglioside antibody production and dysfunction of blood-cerebrospinal fluid (CSF) barrier (BCB) are frequent findings in dysimmune neuropathy patients, whereas intrathecal synthesis of immunoglobulins is still a matter of debate. We examined the CSF, immunological and electrophysiological characteristics from a cohort of patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP), and from patients with other neurological diseases as control. Thirty-eight percent of GBS patients and 28% of CIDP patients had detectable serum titers of anti-ganglioside antibodies, which were associated with a high incidence of motor conduction block and increased F wave latencies. In GBS patients, but not in CIDP or control patients, there was an association between anti-ganglioside antibodies and increased CSF immunoglobulin-G (IgG) levels as determined by the IgG index. However, none of the GBS patients had CSF oligoclonal bands (OBs) or indications of intrathecal anti-ganglioside antibody synthesis. The possibility of an abnormal CSF concentration of immunoglobulins from serum through dysfunctional BCB or damaged nerve roots, and the role of serum anti-ganglioside reactivity in this process are discussed.

Assessment of lesion evolution in experimental autoimmune neuritis by gadofluorine M-enhanced MR neurography

Experimental autoimmune neuritis (EAN) represents an animal model of acute inflammatory nerve injury mirroring pathophysiological aspects of the human Guillain-Barré syndrome. In the present study, we for the first time visualized the spatiotemporal evolution of autoimmune nerve injury and recovery by magnetic resonance imaging (MRI) by use of the novel micellar magnetic resonance (MR) contrast agent gadofluorine M (Gf). EAN was induced in Lewis rats by T-cell transfer (AT-EAN) leading to severe axonal damage, and Gf was applied intravenously at various disease stages mostly 24 h before MRI. In naive rats, Gf enhancement was present solely in the vascular compartment. In AT-EAN, clinically asymptomatic rats already showed consistent Gf uptake in spinal nerves on day 3, while sciatic nerves were spared. The cauda equina correspondingly exhibited massive T-cell infiltration. Gf enhancement further extended to the plexus lumbosacralis on day 4. On days 5 and 6, the entire peripheral neuraxis from the cauda equina, along the sciatic down to the tibial and peroneal nerves, showed strong Gf enhancement. Spinal and peripheral nerves now exhibited massive inflammation and axonal injury on parallel histological analysis. Gf enhancement persisted in the afflicted nerves until complete recovery and disappeared with a proximodistal gradient. In conclusion, Gf-enhanced MR neurography opens a new avenue for monitoring nerve damage in-vivo during an immune attack.

Guillain-Barré syndrome

Guillain-Barré syndrome consists of at least four subtypes of acute peripheral neuropathy. Major advances have been made in understanding the mechanisms of some of the subtypes. The histological appearance of the acute inflammatory demyelinating polyradiculoneuropathy (AIDP) subtype resembles experimental autoimmune neuritis, which is predominantly caused by T cells directed against peptides from the myelin proteins P0, P2, and PMP22. The role of T-cell-mediated immunity in AIDP remains unclear and there is evidence for the involvement of antibodies and complement. Strong evidence now exists that axonal subtypes of Guillain-Barré syndrome, acute motor axonal neuropathy (AMAN), and acute motor and sensory axonal neuropathy (AMSAN), are caused by antibodies to gangliosides on the axolemma that target macrophages to invade the axon at the node of Ranvier. About a quarter of patients with Guillain-Barré syndrome have had a recent Campylobacter jejuni infection, and axonal forms of the disease are especially common in these people. The lipo-oligosaccharide from the C jejuni bacterial wall contains ganglioside-like structures and its injection into rabbits induces a neuropathy that resembles acute motor axonal neuropathy. Antibodies to GM1, GM1b, GD1a, and GalNac-GD1a are in particular implicated in acute motor axonal neuropathy and, with the exception of GalNacGD1a, in acute motor and sensory axonal neuropathy. The Fisher's syndrome subtype is especially associated with antibodies to GQ1b, and similar cross-reactivity with ganglioside structures in the wall of C jejuni has been discovered. Anti-GQ1b antibodies have been shown to damage the motor nerve terminal in vitro by a complement-mediated mechanism. Results of international randomised trials have shown equivalent efficacy of both plasma exchange and intravenous immunoglobulin, but not corticosteroids, in hastening recovery from Guillain-Barré syndrome. Further research is needed to discover treatments to prevent 20% of patients from being left with persistent and significant disability.

An anti-ganglioside antibody-secreting hybridoma induces neuropathy in mice

Immune responses against gangliosides are strongly implicated in the pathogenesis of some variants of Guillain-Barré syndrome (GBS). For example, IgG antibodies against GM1, GD1a, and related gangliosides are frequently present in patients with post-Campylobacter acute motor axonal neuropathy (AMAN) variant of GBS, and immunization of rabbits with GM1 has produced a model of AMAN. However, the role of anti-ganglioside antibodies in GBS continues to be debated because of lack of a passive transfer model. We recently have raised several monoclonal IgG anti-ganglioside antibodies. We passively transfer these antibodies by intraperitoneal hybridoma implantation and by systemic administration of purified anti-ganglioside antibodies in mice. Approximately half the animals implanted with an intraperitoneal clone of anti-ganglioside antibody-secreting hybridoma developed a patchy, predominantly axonal neuropathy affecting a small proportion of nerve fibers. In contrast to hybridoma implantation, passive transfer with systemically administered anti-ganglioside antibodies did not cause nerve fiber degeneration despite high titre circulating antibodies. Blood-nerve barrier studies indicate that animals implanted with hybridoma had leaky blood-nerve barrier compared to mice that received systemically administered anti-ganglioside antibodies. Our findings suggest that in addition to circulating antibodies, factors such as antibody accessibility and nerve fiber resistance to antibody-mediated injury play a role in the development of neuropathy.

Induction of human IgM and IgG anti-GM1 antibodies in transgenic mice in response to lipopolysaccharides from Campylobacter jejuni

Campylobacter jejuni lipopolysaccharides (LPS) are implicated in the development of autoantibodies to GM1 ganglioside in patients with neuropathy following C. jejuni infection. CjLPS bears oligosaccharides that are cross reactive with GM1 ganglioside and presumably exerts its effects via molecular mimicry. To study the mechanisms that are involved in development of the autoantibody response, a transgenic mouse line was developed that expresses an IgM anti-GM1 antibody derived from a patient with multifocal motor neuropathy (MMN). In vivo stimulation of the transgenic mice with C. jejuni lipopolysaccharides (CjLPS), but not of wild-type mice readily elicited high serum titers of anti-GM1 IgM antibodies, followed by IgG anti-GM1 antibodies after two booster injections. In in vitro experiments, CjLPS stimulated the transgenic B-cells at lower concentration than control LPS. The increased sensitivity to CjLPS and the induction of IgG anti-GM1 by CjLPS but not control LPS are consistent with a mechanism of B-cell activation that involves both the LPS and the antigen-specific surface Ig receptors, with possible participation of T-cells.