Antibodies to gangliosides and myelin proteins in Guillain-Barré syndrome

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

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

Autoreactive T cells target peripheral nerves in Guillain-Barré syndrome

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

Immunoproteomic identification of antigenic candidate Campylobacter jejuni and human peripheral nerve proteins involved in Guillain-Barré syndrome

Immunoproteomics is become a potent methodology used for identifying immunoreactive proteins. In this study, an immunoproteomic approach based on 2-dimensional gel electrophoresis (2D-PAGE) and immunoblotting combined with high resolution mass spectrometry (MS) was used to identify immunoreactive proteins that might be involved in mechanisms of Guillain-Barré syndrome (GBS) development, regardless of their potential reciprocal molecular mimicry. Proteins isolated from C. jejuni and human peripheral nerve tissue (HPN) were separated with 2D SDS-PAGE and subjected to western blotting using serum samples from GBS patients. The peptides generated after proteolysis of the immunoreactive proteins were submitted to nanoflow-high performance liquid chromatography-nano electrospray ionization coupled to high resolution mass spectrometry (nHPLC-nESI-MS and MS/MS) followed by SEQUESTdata analysis for proteins identification. In C. jejuni, immunoreactivity was found for GroEL and DnaK, structural proteins (MOMP), key enzymatic proteins necessary for the microbial proliferation (adenylate kinase, enolase, inorganic pyrophosphatase and aspartate ammonia-lyase), and antioxidant enzymes (alkyl hydroperoxide reductase-AhpC and DNA protection during starvation protein - DNA protection factor against Fe²⁺-mediated oxidative stress). HPN immunoreactive proteins identified were heat shock proteins (HSP), intermediate filaments (vimentin and desmin), and other proteins and enzymes such as troponin/tropomyosin complex and ATP synthase subunit beta and the keratan sulfate proteoglycan lumican. The targeting of vimentin and desmin, suggested that the neuronal autoimmune damage is specifically directed to intermediate neuronal (vimentin) and neuromuscular IF, probably localized nearby cell surface, affording increased accessibility to autoantibodies. These findings suggest that the post-infectious development of GBS may be also associated to additional concomitant immune factors that lead to nerve damage generated by auto-immune trigger(s) different from molecular mimicry.

Sialylated intravenous immunoglobulin suppress anti-ganglioside antibody mediated nerve injury

The precise mechanisms underlying the efficacy of intravenous immunoglobulin (IVIg) in autoimmune neurological disorders including Guillain-Barré syndrome (GBS) are not known. Anti-ganglioside antibodies have been reported to be pathogenic in some variants of GBS, and we have developed passive transfer animal models to study anti-ganglioside antibody mediated-endoneurial inflammation and associated neuropathological effects and to evaluate the efficacy of new therapeutic approaches. Some studies indicate that IVIg's anti-inflammatory activity resides in a minor sialylated IVIg (sIVIg) fractions and is dependent on an innate Th2 response via binding to a specific ICAM3-grabbing nonintegrin related 1 receptor (SIGN-R1). Therefore the efficacy of IVIg, IVIg fractions with various IgG Fc sialylation status, and the involvement of Th2 pathway were examined in one of our animal model of antibody-mediated inhibition of axonal regeneration. We demonstrate that both IVIg and sIVIg ameliorated anti-glycan antibody mediated-pathological effect, whereas, the unsialylated fractions of IVIg were not beneficial in our model. Tenfold lower doses of sIVIg compared to whole IVIg provided equivalent efficacy in our studies. Moreover, we found that whole IVIg and sIVIg significantly upregulates the gene expression of IL-33, which itself can provide protection from antibody-mediated nerve injury in our model. Our results support that the SIGN-R1-Th2 pathway is involved in the anti-inflammatory effects of IVIg on endoneurium in our model and elements of this pathway including IL-33 can provide novel therapeutics in inflammatory neuropathies.

Chronic inflammatory demyelinating polyradiculoneuropathy: from pathology to phenotype

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an inflammatory neuropathy, classically characterised by a slowly progressive onset and symmetrical, sensorimotor involvement. However, there are many phenotypic variants, suggesting that CIDP may not be a discrete disease entity but rather a spectrum of related conditions. While the abiding theory of CIDP pathogenesis is that cell-mediated and humoral mechanisms act together in an aberrant immune response to cause damage to peripheral nerves, the relative contributions of T cell and autoantibody responses remain largely undefined. In animal models of spontaneous inflammatory neuropathy, T cell responses to defined myelin antigens are responsible. In other human inflammatory neuropathies, there is evidence of antibody responses to Schwann cell, compact myelin or nodal antigens. In this review, the roles of the cellular and humoral immune systems in the pathogenesis of CIDP will be discussed. In time, it is anticipated that delineation of clinical phenotypes and the underlying disease mechanisms might help guide diagnostic and individualised treatment strategies for CIDP.

Glycoconjugates as target antigens in peripheral neuropathies

Identification and characterization of antigens present at the human peripheral nerve is a great challenge in the field of neuroimmunology. The latest investigations are focused on the understanding of the biology of glycoconjugates present at the peripheral nerve, and their immunological reactivity. Increased titers of antibodies that recognize carbohydrate determinants of glycoconjugates (glycolipids and glycoproteins) are associated with distinct neuropathic syndromes. There is considerable cross-reactivity among anti-ganglioside antibodies, resulting from shared oligosaccharide epitopes, possibly explaining the overlap in syndromes observed in many affected patients. Sera from patients with neuropathies (GBS, chronic inflammatory demielynating polyneuropathy - CIDP, multifocal motor neuropathy - MMN), cross-react with glycoproteins isolated from human peripheral nerve and from Campylobacter jejuni O:19. The frequency of occurrence of antibodies against these glycoproteins is different, depending of the type of neuropathy. Identification of the cross-reactive glycoproteins and possible additional auto antigens could be useful in laboratory evaluation of peripheral neuropathies and help to develop a more effective therapeutic approach.

Anti-GM1 antibodies as a model of the immune response to self-glycans

Glycans are a class of molecules with high structural variability, frequently found in the plasma membrane facing the extracellular space. Because of these characteristics, glycans are often considered as recognition molecules involved in cell social functions, and as targets of pathogenic factors. Induction of anti-glycan antibodies is one of the early events in immunological defense against bacteria that colonize the body. Because of this natural infection, antibodies recognizing a variety of bacterial glycans are found in sera of adult humans and animals. The immune response to glycans is restricted by self-tolerance, and no antibodies to self-glycans should exist in normal subjects. However, antibodies recognizing structures closely related to self-glycans do exist, and can lead to production of harmful anti-self antibodies. Normal human sera contain low-affinity anti-GM1 IgM-antibodies. Similar antibodies with higher affinity or different isotype are found in some neuropathy patients. Two hypotheses have been developed to explain the origin of disease-associated anti-GM1 antibodies. According to the "molecular mimicry" hypothesis, similarity between GM1 and Campylobacter jejuni lipopolysaccharide carrying a GM1-like glycan is the cause of Guillain-Barré syndrome associated with anti-GM1 IgG-antibodies. According to the "binding site drift" hypothesis, IgM-antibodies associated with disease originate through changes in the binding site of normally occurring anti-GM1 antibodies. We now present an "integrated" hypothesis, combining the "mimicry" and "drift" concepts, which satisfactorily explains most of the published data on anti-GM1 antibodies.

Pathogenesis of chronic inflammatory demyelinating polyradiculoneuropathy

The acute lesions of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) consist of endoneurial foci of chemokine and chemokine receptor expression and T cell and macrophage activation. The myelin protein antigens, P2, P0, and PMP22, each induce experimental autoimmune neuritis in rodent models and might be autoantigens in CIDP. The strongest evidence incriminates P0, to which antibodies have been found in 20% of cases. Failure of regulatory T-cell mechanism is thought to underlie persistent or recurrent disease, differentiating CIDP from the acute inflammatory demyelinating polyradiculoneuropathy form of Guillain-Barré syndrome. Corticosteroids, intravenous immunoglobulin and plasma exchange each provide short term benefit but the possible long-term benefits of immunosuppressive drugs have yet to be confirmed in randomised, controlled trials.

T cell reactivity to P0, P2, PMP-22, and myelin basic protein in patients with Guillain-Barre syndrome and chronic inflammatory demyelinating polyradiculoneuropathy

OBJECTIVES

It has been suggested that autoimmunity to peripheral myelin proteins is involved in the pathogenesis of Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We aimed to compare reactivity of peripheral blood mononuclear cells (PBMC) to antigens of peripheral myelin proteins in patients with GBS and patients with CIDP with that of healthy controls and patients with other non-immune mediated neuropathies (ON).

METHODS

We prepared PBMC from blood from 83 healthy controls and from 64 patients with GBS, 54 with CIDP, and 62 with ON. PBMC were tested in antigen specific proliferation assays against peptides from myelin proteins P0, P2, PMP22, and myelin basic protein (MBP), which is identical to myelin P1, and against whole human MBP. Interferon-gamma (IFN-gamma) and interleukin (IL)-5 enzyme linked immunospot (ELISPOT) assays were also performed in some subjects to assess spontaneous and peripheral myelin antigen specific PBMC cytokine secretion.

RESULTS

Antigen specific PBMC proliferation assays showed no significant elevation of peptide specific T cell responsiveness in patients with GBS or CIDP compared with healthy controls or patients with ON. Levels of spontaneous ELISPOT IFN-gamma secretion were increased in patients with GBS and significantly increased in those with CIDP compared with healthy controls and patients with ON. No convincing differences in antigen specific ELISPOT IFN-gamma secretion levels to individual peptides were detectable in patients with GBS. The proportion of patients with CIDP with an increased number of PBMC producing IFN-gamma in response to peptide PMP-22(51-64) was significantly increased compared with healthy controls and patients with ON. No significant differences in antigen specific ELISPOT IL-5 secretion levels were detectable in patients with GBS or CIDP compared with controls, but levels of spontaneous IL-5 secretion were significantly higher in patients with CIDP than in healthy controls or patients with ON.

CONCLUSIONS

Although the lack of significantly increased antigen specific PBMC proliferation in GBS and CIDP does not support a role for T cells, the more sensitive ELISPOT technique detected increased numbers of PBMC secreting IFN-gamma spontaneously in 25% of patients with GBS, providing further evidence for a role of T cells in the immunopathology of GBS. Increased numbers of spontaneous IFN-gamma and IL-5 secreting cells, and increased IFN-gamma secretion in response to PMP-22(51-64), in patients with CIDP provide further evidence for a role of myelin specific T cells in CIDP.

Antibodies to peripheral nerve myelin proteins in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired disorder of the peripheral nervous system with a probable auto-immune pathogenesis. The nature of the responsible autoantigens is unclear in most patients. We used the Western immunoblot technique to seek antibodies to peripheral nerve protein antigens. Sera from eight of 32 (25%) CIDP patients, 12 of 37 (32%) Guillain-Barré syndrome (GBS) patients, zero of 30 (0%) chronic idiopathic axonal polyneuropathy patients and two of 39 (5%) healthy control subjects contained anti-peripheral nerve protein antibodies. The frequency of such antibodies was significantly greater in both CIDP (p = 0.04) and GBS (p = 0.003) patients than in normal control subjects. For CIDP patients, there were non-significant trends for antibodies to be more common in females and in those who responded to treatment with either intravenous immunoglobulin or plasma exchange. The commonest antibodies were directed against a band at 28 kDa, resembling that labelled by a monoclonal antibody against myelin protein zero (P0). Six CIDP and seven GBS patients' sera reacted with this band. These results support the view that antibodies to myelin proteins, and especially P0, are present in the serum of some patients with CIDP and GBS.

The origin of anti-GM1 antibodies in neuropathies: the "binding site drift" hypothesis

Elevated titers of serum antibodies against GM1-ganglioside are associated with a variety of autoimmune neuropathies. The origin of these autoantibodies is still unknown, although there is evidence that they are produced by CD5+ B-lymphocytes and that antigen mimicry is involved. Anti-GM, IgM-antibodies in the normal human immunological repertoire are low affinity antibodies that cross-react with other glycoconjugates carrying Gal beta1-3GalNAc and probably do not have GM1-mediated biological activity. Other anti-GM1 IgM-antibodies with higher affinity and/or different fine specificity are present in patients with motor syndromes. Based on our studies of structural requirement for binding, we hypothesize that disease-associated anti-GM1 antibodies originate at random by mutations affecting the binding site of naturally-occurring ones. The hypothesis is conceptually similar to the established phenomenon of "genetic drift" in species evolutionary biology and is therefore termed "binding site drift".

Antibody pattern analysis in the Guillain-Barré syndrome and pathologic controls

The Guillain-Barré Syndrome (GBS) is an acute inflammatory polyneuroradiculopathy, which is considered to be caused by autoimmune processes. A number of single antigenic structures has been suggested to be targeted by the immune system, but a conclusive etiological concept has not been evolved yet. We compared reactions of sera from GBS patients (N=28) and from both two pathological control groups, 25 Multiple sclerosis (MS) patients and 32 patients with other non-inflammatory peripheral polyneuropathies (ONP) and from sex- and age-matched healthy controls (N=30). Porcine peripheral nerve proteins were used as antigens in a Western blot procedure. The blots were analysed by densitometry, and a multivariate statistical comparison of the antibody repertoires was carried out. Antibody patterns of GBS patients differed significantly (p<0.001) from each of the control groups. Discriminant analysis indicated that the discrimination resulted from pattern differences of specific regions of the blots containing proteins with estimated molecular weights of 58-64 and 28-29 kDa. We conclude that statistical analysis of antibody patterns may be helpful both in clinical diagnosis and in further research concerning the pathogenesis of GBS.

Can antiglycolipid antibodies present in HIV-infected individuals induce immune demyelination?

Of the eight clinically defined neuropathies associated with HIV infection, there is compelling evidence that acute and chronic inflammatory demyelinating polyneuropathy (IDPN) have an autoimmune pathogenesis. Many non-HIV infected individuals who suffer from sensory-motor nerve dysfunction have autoimmune indicators. The immunopathogenesis of demyelination must involve neuritogenic components in myelin. The various antigens suspected to play a role in HIV-seronegative IDPN include (i) P2 protein; (ii) sulfatide (GalS); (iii) various gangliosides (especially GM1); (iv) galactocerebroside (GalC); and (v) glycoproteins or glycolipids with the carbohydrate epitope glucuronyl-3-sulfate. These glycoproteins or glycolipids may be individually targeted, or an immune attack may be raised against a combination of any of these epitopes. The glycolipids, however, especially GalS, have recently evoked much interest as mediators of immune events underlying both non-HIV and HIV-associated demyelinating neuropathies. The present review outlines the recent research findings of antiglycolipid antibodies present in HIV-infected patients with and without peripheral nerve dysfunction, in an attempt to arrive at some consensus as to whether these antibodies may play a role in the immunopathogenesis of HIV-associated inflammatory demyelinating polyneuropathy.

Anti-GM1, anti-central myelin proteins, and anti-cardiolipin autoantibodies during plasma-exchange in Guillain-Barré syndrome (GBS)

We measured the autoantibodies to GM1, central myelin proteins, and cardiolipin in 30 GBS patients using sensitive ELISA and Western blot techniques. The sequential modifications of titers during plasma-exchange (PE) and at follow-up were investigated in 15 patients. In pretreatment sera, we found significantly increased antibody titers to GM1 (37% of the patients), central myelin proteins (28%), and cardiolipin (21%). Seventeen patients out of 29 (58%) presented increased IgG or IgM antibody to at least one of the antigens considered as compared to 10 out of 70 controls (14%, P = 0.00001). By Western blot, IgG or IgM antibodies reactive with the triton insoluble fraction of central myelin were observed in 19 out of 28 GBS patients (67%). The follow-up measurements during and after PE showed a declining autoantibody titer in 10 out of 15 patients. However, in the remaining 5 GBS patients, we observed a persistently elevated titer or an increase from baseline values occurring during or after PE and reaching a peak. In 2 of the 5 patients, the titer peak preceded a clinical re-exacerbation. The presence of a persistently elevated or an increasing autoantibody titer during treatment with PE merits further investigation and may help to clarify the pathogenesis of GBS and improve its treatment.

Anti-PMP22 antibodies in patients with inflammatory neuropathy

An experimental model of inflammatory radiculoneuropathy is induced by immunising rats with peripheral myelin protein 22 (PMP22). We have investigated whether PMP22 may be important in inducing human inflammatory neuropathy. We examined sera of patients with Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), other neuropathies (ONP) and normal controls for IgM and IgG antibodies against PMP22 by ELISA (against synthetic PMP22 extracellular peptide fragments) and Western blot (against cauda equina). Antibodies were detected by both methods in 52% of patients with GBS, 35% with CIDP, 3% with ONP and no normal controls. We conclude that an immune response against PMP22 may play a role in the pathogenesis of the inflammatory neuropathies.

Autoantibodies associated with peripheral neuropathy

High titers of serum antibodies to neural antigens occur in several forms of neuropathy. These include neuropathies associated with monoclonal gammopathy, inflammatory polyneuropathies, and paraneoplastic neuropathies. The antibodies frequently react with glycosylated cell surface molecules, including glycolipids, glycoproteins, and glycosaminoglycans, but antibodies to intracellular proteins have also been described. There are several correlations between antibody specificity and clinical symptoms, such as anti-MAG antibodies with demyelinating sensory or sensorimotor neuropathy, anti-GM1 ganglioside antibodies with motor nerve disorders, antibodies to gangliosides containing disialosyl moieties with sensory ataxic neuropathy and Miller-Fisher syndrome, and antibodies to the neuronal nuclear Hu antigens with paraneoplastic sensory neuronopathy. These correlations suggest that the neuropathies may be caused by the antibodies, but evidence for a causal relationship is stronger in some examples than others. In this review, we discuss the origins of the antibodies, evidence for and against their involvement in pathogenic mechanisms, and the implications of these findings for therapy.

Campylobacter jejuni infection as a cause of the Guillain-Barré syndrome

A previously unrecognized sequelum of infection with Campylobacter jejuni, a common cause of gastroenteritis, is Guillain-Barré syndrome (GBS). GBS is the most common cause of acute neuromuscular paralysis; 30% to 40% of cases are preceded by C. jejuni infection. Both patient and bacterial characteristics likely play a role in the pathogenesis of C. jejuni-induced GBS. Molecular mimicry between the LPS of some campylobacters and structures present on the gangliosides of the peripheral nerve may explain how this acute infectious diarrheal illness triggers GBS.

Anti-GM1 ganglioside IgM-antibodies present in human plasma: affinity and biological activity changes in a patient with neuropathy

Low affinity anti-GM1 IgM-antibodies are part of the normal repertoire of human plasma antibodies (Mizutamari et al.: J Neuroimmunol 50:215-220, 1994), a fact that is against the pathological role proposed for them in autoimmune diseases. Here we present evidence that these low affinity IgM-antibodies are devoid of complement-mediated lytic activity to GM1-liposomes, suggesting that they should not be considered harmful. In contrast to the absence in normal individuals, in the plasma of a patient with sensory polyneuropathy we detected high affinity anti-GM1 IgM-antibodies. Concomitant with the presence of these high affinity anti-GM1 IgM-antibodies, the patient plasma is capable of producing complement-mediated lysis of GM1-liposomes. These results suggest that an increase in the affinity of the naturally existing anti-GM1 antibodies could be the trigger that switches them from non-harmful to pathological.

Factors defining target specificity in antibody-mediated neuropathy: density-dependent binding of anti-GD1a polyclonal IgG from a neurological patient

IgM and IgG antibodies reacting with components of human brain gangliosides were detected in a patient bearing severe sensory ataxy. Using different chemical and immunological methods, the antigen was identified as the GD1a ganglioside. The antibodies showed antigen "density-dependent" binding, a property only observed in tumor-specific monoclonal antibodies. The relevance of this result in regard with target specificity of neuropathy-associated antibodies directed to ubiquitous glycolipids is discussed.

The antibody repertoire in experimental allergic neuritis: evidence for PMP-22 as a novel neuritogen

Experimental allergic neuritis (EAN) is an autoimmune disease that serves as an animal model for the Guillain-Barré syndrome (GBS). In both disorders there is still great uncertainty as to the significance and diversity of autoantibodies involved. We focused on the characterization of serum antibody production in response to various peripheral nervous system (PNS) myelin proteins during the course of actively induced EAN in Lewis rats. These data were compared with EAN induced by adoptive transfer of P2-specific CD4+ T cells (AT-EAN) and with inoculation with complete Freund's adjuvant (CFA) alone. Semiquantitative Western blotting was applied to measure serum IgM and IgG titers against specific myelin proteins, including P2, P0, myelin basic protein (MBP), myelin-associated glycoprotein (MAG) and PMP-22. Considerable differences in the dynamics of antibody titers against individual myelin proteins were observed in active EAN and after inoculation with CFA alone. Our data suggest a pathogenic role of IgM antibodies against HNK adhesion carbohydrate epitope expressing PNS proteins P0, MAG and PMP-22. Among these, PMP-22, a novel candidate neuritogen may be of particular relevance. Thus, we provide evidence for the involvement of antibody-mediated immune response in actively induced EAN and a basis for similar studies on related human disorders such as GBS or other demyelinating neuropathies.

Chronic immune-related demyelinating neuropathies

In recent years many important advances have been made in the knowledge of the mechanisms that may produce peripheral nerve damage. Data in the literature indicate that in some chronic demyelinating neuropathy autoantibodies against myelin antigens may play a pathogenic role. The pathogenic role of T cells, cytokines, complement, and class II molecules has also been studied. Identification of specific immune-related demyelinating polyneuropathies provides clues to future therapeutic approaches. This paper focuses on the chronic inflammatory demyelinating polyneuropathy, chronic demyelinating neuropathies associated with monoclonal gammapathies of undetermined significance, and multifocal motor neuropathy, and reviews their clinical, patophysiological and immunological features.

Experimental immunization with Borrelia burgdorferi induces development of antibodies to gangliosides

Patients with neuroborreliosis produce antibodies, mostly of the immunoglobulin M (IgM) class, to gangliosides, particularly to those with Gal(beta 1-3)GalNac terminal sequences. Lewis rats were immunized with a nonpathogenic strain of Borrelia burgdorferi and with a chloroform-methanol extract (nonprotein) of this organism (CM) to determine whether antibodies to B. burgdorferi also recognized gangliosides. Rats were also immunized with asialo-GM1 to determine whether the elicited antibodies recognized antigens in B. burgdorferi. Rats immunized with B. burgdorferi produced low levels of IgM antibodies that cross-reacted with asialo-GM1 and GM1. Rats immunized with CM had marked IgM reactivity to asialo-GM1 and GM1. Immunization with asialo-GM1 resulted in antibodies that cross-reacted with B. burgdorferi antigens. Although antibodies to B. burgdorferi were of both the IgM and IgG classes, those to CM and to asialo-GM1 and GM1 were predominantly in the IgM fraction. Reactivity of the IgM antibodies decreased after adsorption with the heterologous and the homologous antigens, indicating bidirectional cross-reactivity between CM, asialo-GM1, and GM1 and that immunization with one produces antibodies to the other. There was no in vivo deposition of Ig in peripheral nerves, nor was there nerve pathology as a result of immunizations, but IgM antibodies to asialo-GM1 and CM recognized homologous antigens in the nodes of Ranvier of peripheral nerves from nonimmunized rats. This immunization model suggests that antibodies to gangliosides in Lyme disease have a microbial origin and are potentially relevant in pathogenesis.

The neuronal toxic factor in serum of type 1 diabetic patients is a complement-fixing autoantibody

Type 1 diabetes is an autoimmune disease resulting in destruction of pancreatic beta cells. Many of the pancreatic beta cell autoantigens are also neuronal cell components. Using adrenergic neuroblastoma cells, we have previously demonstrated that humoral mechanisms may contribute to the development of diabetic neuropathy in Type 1 patients. We hypothesize that the toxic factor in Type 1 diabetic serum is an immunoglobulin. When neuroblastoma cells were exposed to immunoglobulins precipitated from serum of Type 1 diabetes patients with neuropathy, cell growth was significantly inhibited by day 5 (3.8 +/- 2.4 x 10(5) cells) compared to cells cultured with immunoglobulins from control (8.2 +/- 2.3 x 10(5) cells) or Type 2 diabetic serum (7.0 +/- 3.0 x 10(5) cells). The inhibitory effect (3.2 +/- 0.9 x 10(5) cells) could be removed from Type 1 diabetic serum by affinity precipitation with protein A-agarose (8.0 +/- 0.8 x 10(5) cells). Mild heat denaturing of the serum reversed the inhibitory effect (3.8 +/- 0.9 vs 1.4 +/- 1.4 x 10(5) cells), indicating a requirement for complement. Immunofluorescent labelling with anti-IgG secondary antibody of cells exposed to Type 1 diabetic serum indicated recognition of a membrane-bound antigen. The studies in this report support the hypothesis that autoimmune neuronal destruction may contribute to the development of diabetic autonomic neuropathy in patients with Type 1 diabetes.

Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy: immune mechanisms and update on current therapies

The relation between Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy is discussed. Most likely they represent parts of a continuum, arbitrarily separated by their time course. Within the concept of chronic inflammatory demyelinating polyneuropathy the presence of a monoclonal gammopathy of undetermined significance is discussed. The pathogenesis of inflammatory demyelinating polyneuropathies has not been elucidated yet, but involvement of the immune system has been firmly established. Preceding infections, especially with Campylobacter jejuni, and the analysis of antiganglioside antibodies lend new support to the hypothesis of molecular mimicry between epitopes on infectious agents and peripheral nerve constituents as one of the mechanisms in Guillain-Barré syndrome. In the future, a further classification of individual patients based on clinical, epidemiological, electrophysiological, pathological, microbiological, and immunological criteria may give a basis for more individualized treatment strategies. In Guillain-Barré syndrome the efficacy of high-dose intravenous immune globulin treatment was established after earlier positive findings with plasma exchange; immune globulins are easier to administer and may be superior. Even with these treatments it should be anticipated that one fourth of patients after immune globulin treatment and one third of patients after plasma exchange will show further deterioration in the first 2 weeks after onset of treatment. Despite this, just one treatment course usually is indicated in the individual patient, and no valid arguments were found to switch to the other treatment modality. In chronic inflammatory demyelinating polyneuropathy, prednisone, plasma exchange, and immune globulins are effective in a proportion of patients. The last two are equally effective. Patients may respond to one of these if a previous treatment failed, and here switching therapy may be effective due to the chronic course of the disease. Complexity and costs make plasma exchange the last choice. Whether prednisone or immune globulin is the first choice depends on the speed of recovery and the estimation of long-term loss of quality of life due to side effects of prednisone versus the costs of immune globulins. The mechanism of immune globulins in inflammatory polyneuropathies is discussed. There is evidence that idiotypic-antiidiotypic interaction may play a role, but several other mechanisms also may be involved.

Activated T cells of nonneural specificity open the blood-nerve barrier to circulating antibody

Recent studies from our laboratory and by other investigators have shown that autoreactive CD4+ cells specific for peripheral nerve P2 protein have a powerful effect on blood-nerve barrier permeability. In this study we injected CD4+ T cells reactive to a nonneural antigen (ovalbumin) systemically and achieved their accumulation in the tibial nerve of Lewis rats by previous intraneural injection of ovalbumin. Selected rats were given systemic demyelinating antibody (antigalactocerebroside) to provide an indicator of changes in the permeability of the blood-nerve barrier, and the animals were monitored by sequential neurophysiological studies and histology. Circulating ovalbumin-specific T cells accumulated at sites of intraneural ovalbumin injection without inducing demyelination in control animals. In rats with circulating galactocerebroside antibodies, local conduction block and demyelination were seen in the region of T-cell accumulation. Electron microscopy demonstrated dissolution of some tight junctions between endothelial cells in areas of T-cell accumulation, and T cells traversing the endothelium between endothelial cells and through their cytoplasm. Endothelial cell damage was evident in these areas. This study demonstrates breakdown of the blood-nerve barrier by activated T cells, even of nonneural specificity, allowing the development of focal conduction block and demyelination in the presence of circulating antimyelin antibodies.

Immunopathogenesis and treatment of the Guillain-Barré syndrome--Part I

The etiology of the Guillain-Barré syndrome (GBS) still remains elusive. Recent years have witnessed important advances in the delineation of the mechanisms that may operate to produce nerve damage. Evidence gathered from cell biology, immunology, and immunopathology studies in patients with GBS and animals with experimental autoimmune neuritis (EAN) indicate that GBS results from aberrant immune responses against components of peripheral nerve. Autoreactive T lymphocytes specific for the myelin antigens P0 and P2 and circulating antibodies to these antigens and various glycoproteins and glycolipids have been identified but their pathogenic role remains unclear. The multiplicity of these factors and the involvement of several antigen nonspecific proinflammatory mechanisms suggest that a complex interaction of immune pathways results in nerve damage. Data on disturbed humoral immunity with particular emphasis on glycolipid antibodies and on activation of autoreactive T lymphocytes and macrophages will be reviewed. Possible mechanisms underlying initiation of peripheral nerve-directed immune responses will be discussed with particular emphasis on the recently highlighted association with Campylobacter jejuni infection.

Immunopathogenesis and treatment of the Guillain-Barré syndrome--Part II

In the second part of our review the role of antecedent infections in the pathogenesis of GBS is discussed. The association with Campylobacter jejuni (C. jejuni) is highlighted and the concept of molecular mimicry, i.e., sharing of epitopes between microbes and peripheral nerve, explained. Alternative mechanisms to relate an infection with the immune-mediated neuropathy are elaborated. Current therapies of the GBS include plasma exchange, high-dose intravenous immunoglobulins, and supportive treatment directed to secondary complications. Published therapeutic trials are reviewed and future approaches are outlined. Principles of general care are also summarized.

Myelin- and microbe-specific antibodies in Guillain-Barré syndrome

We surveyed the frequency of reported infections and target autoantigens in 56 Guillain Barré syndrome (GBS) patients by detecting antibodies to myelin and microbes. Sulfatide (43%), cardiolipin (48%), GD1a (15%), SGPG (11%), and GM3 (11%) antibodies were the most frequently detected heterogenous autoantibodies. A wide spectrum of antimicrobial IgG and IgM antibodies were also detected; mumps-specific IgG (66%), adenovirus-specific IgG (52%), varicella-zoster virus-specific IgG (46%), and S. pneumoniae serotype 7-specific IgG (45%) were the most prevalent. Our results indicate that polyclonal expansion of physiologic and pathologic antibodies and/or molecular mimicry likely occurs following infection and is related to other autoimmune factors in the etiology of GBS. Although no single definitive myelin-specific autoantibody was identified, our results suggest a unique pattern of reactivity against autoantigens.

Serum IgG antibodies to a 35-kDa P0-related glycoprotein in motor neuron disease

Using an immunoblot technique we found a significantly higher frequency of serum IgG antibodies to a 35-kDa peripheral nerve myelin glycoprotein in patients with motor neuron disease (MND) (39% of 70) than in patients with neuropathy (13% of 61), other neurological disease (9% of 32) and normal subjects (5% of 20) (P < 0.005 in all cases), but not with multiple sclerosis (MS) (20% of 30) or non-neural immune diseases (25% of 32). Most positive patients had antibody titers of 1:200 or 1:2000 while higher titers were only found in seven patients with MND, one with chronic inflammatory demyelinating neuropathy, two with MS, two with non-neural immune diseases and one with stroke. The reacting protein had a higher molecular mass than P0 and was only faintly bound by an anti-P0 antiserum, but had the same N-terminal amino acid sequence of P0. The difference in molecular mass between P0 and the 35-kDa protein and the IgG reactivity of one patient's IgG with the 35-kDa protein persisted after its deglycosylation and dephosphorylation. Although there is no evidence that these antibodies are pathogenic, their frequent occurrence in MND and other immune-mediated conditions supports the hypothesis of an activation of the immune system in MND.

Characterization of anti-ganglioside antibodies present in normal human plasma

Samples of plasma from normal human adults were screened for anti-ganglioside antibodies by HPTLC-immunostaining and enzyme-linked immunosorbent assay (ELISA). All the samples analyzed showed IgM-immunoreactivity to GM1 ganglioside and its related glycolipid GA1. Reactivity to GD1b, GM2 and LM1 was also detected in 85, 80 and 20% of the analyzed samples, respectively. The main immunoreactivity is related to the asialo-ganglioside GA1. Using inhibition by soluble antigen and affinity chromatography techniques it was possible to distinguish two populations of anti-GA1 antibodies. One with high affinity reacting only with GA1, and another with low affinity reacting also with GM1 and GD1b. The antibodies that recognize GM2 are of low affinity and appear to be different from those that react with GA1. We postulate that the anti-GM1/GD1b immunoreactivity present in normal human plasma could be a cross-reaction of antibodies originally directed to a GA1-like carbohydrate structure. Anti-GA1 and anti-GM1 titers were calculated as the reciprocal of the plasma dilution needed to obtain the half maximal antibody binding, a titer definition that we consider more suitable to compare data from different laboratories than those usually employed.

The spectrum of immune responses to Campylobacter jejuni and glycoconjugates in Guillain-Barré syndrome and in other neuroimmunological disorders

An acute infectious illness frequently precedes the Guillain-Barré syndrome. Recently, Campylobacter jejuni was claimed to be a predominant precipitating agent that may also trigger a humoral immune response to glycoconjugates of peripheral myelin in Guillain-Barré syndrome. Because of conflicting reports, we determined the frequency of a recent infection with C. jejuni in 38 patients with Guillain-Barré syndrome using a highly sensitive and specific immunoblot technique, and of the presence of circulating antibodies to gangliosides. We detected IgM and/or IgG C. jejuni directed antibodies in 15 of 38 patients with Guillain-Barré syndrome. In contrast, only 7 of 39 healthy control subjects, 3 of 20 patients with multiple sclerosis, and 2 of 72 patients with neuroborreliosis showed IgA or IgM antibody responses to C. jejuni. In Guillain-Barré syndrome, C. jejuni-specific antibodies were predominantly directed to outer membrane proteins of one specific serotype, Lior 11, whereas the most common serotype associated with enteritis in Germany is Lior 4. Two of 27 patients with Guillain-Barré syndrome had ganglioside-specific IgA antibodies; 1 of 32 patients, antibodies of IgM; and 4 of 31 patients, antibodies of IgG class. There was no correlation between severity, type (axonal versus demyelinating), and outcome of the disease and the presence or absence of a humoral immune response to C. jejuni or to glycoconjugates. Our findings do not support previous suggestions that a preceding C. jejuni infection heralds a poorer outcome or that antibodies to gangliosides carry prognostic significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Reactivity of neuroborreliosis patients (Lyme disease) to cardiolipin and gangliosides

A subset of patients (50%) with neuroborreliosis (Lyme disease) showed IgG reactivity to cardiolipin in solid phase ELISA. In addition, a subset of patients with neuroborreliosis (29%) and syphilis (59%) had IgM reactivity to gangliosides with a Gal(beta 1-3) GalNac terminal sequence (GM1, GD1b, and asialo GM1). Anti-ganglioside IgM antibodies were significantly more frequent in these two groups of patients compared to patients with cutaneous and articular Lyme disease, primary antiphospholipid syndrome, systemic lupus erythematosus and normal controls. Correlative evidence and adsorption experiments indicated that antibodies to cardiolipin had separate specificities from those directed against the gangliosides. IgM antibodies to Gal(beta 1-3) GalNac gangliosides appeared to have similar specificities since these were positively correlated and inhibitable by cross adsorption assays. Given the clinical associations of patients with neuroborreliosis and syphilis with IgM reactivity to gangliosides sharing the Gal(beta 1-3) GalNac terminus, we suggest that these antibodies could represent a response to injury in neurological disease or a cross reactive event caused by spirochetes.

Detection and quantification of antibodies to the extracellular domain of P0 during experimental allergic neuritis

Quantification of the peripheral nerve myelin glycoprotein P0 and antibodies to P0 is difficult due to insolubility of P0 in physiological solutions. We have overcome this problem by using the water-soluble recombinant form of the extracellular domain of P0 (P0-ED) and describe newly developed assays which allow detection and quantitation of P0 and antibodies to P0, in serum and cerebrospinal fluid (CSF). These sensitive and specific assays based on the ELISA technique were used to study humoral immune responses to P0 during experimental autoimmune ("allergic") neuritis (EAN). In order to establish these tests, monoclonal antibodies to different epitopes of rodent and human P0-ED were produced. A two-antibody sandwich-ELISA allowing quantitation of P0 (lower detection limit of 0.5 ng/ml or 30 fmol/ml) and an antibody-capture ELISA (lower detection limit 1 ng specific antibody/ml) to detect antibodies to P0 in serum and CSF were developed. EAN was induced in rats by active immunization with bovine myelin or the neuritogenic protein P2 or by adoptive transfer using P2 specific CD4 positive T cells. Serum and CSF were assayed for the presence of P0-ED and antibodies to P0-ED or P2. Antibodies to P0-ED were detected during active myelin-induced EAN, but not during P2-induced or adoptive transfer EAN. The anti-P0-ED antibodies in the CSF showed a correlation with disease activity. In contrast, in the same model antibodies to P2 persisted long after the disease ceased. No soluble P0-like fragments could be found in serum or CSF during any of the three types of EAN. We conclude that P0 may be a B-cell epitope in EAN. These findings warrant a screen for antibodies to P0-ED in human immune neuropathies.

Antibody responses to P0 and P2 myelin proteins in Guillain-Barré syndrome and chronic idiopathic demyelinating polyradiculoneuropathy

Immunisation with the peripheral nerve myelin proteins P0 or P2 induces inflammatory neuropathy in animals. We sought antibodies with an ELISA to these proteins in 38 patients with acute Guillain-Barré syndrome (GBS), 32 patients with chronic idiopathic demyelinating polyradiculoneuropathy (CIDP), 31 patients with other neuropathies (ONP) and 26 normal control (NC) subjects. We discovered IgM antibodies to human P0 protein in the sera of 18.5% of the patients with GBS, 15.6% with CIDP, 6.4% with ONP and 3.8% of NC subjects. Of the sera which reacted with P0, sera from 4/7 of GBS, 3/5 of CIDP, 1/2 of ONP patients and 0/1 of NC subjects reacted with a synthetic P0 peptide representing residues 150-169 from the cytoplasmic portion of the molecule. IgG antibodies to P0 were slightly less common than IgM antibodies, being present in only 7.9% of GBS, 0% of CIDP and 3% of ONP patients and 0% of NC subjects. We found antibodies to bovine P2 protein more commonly than antibodies to P0. IgM antibodies were present in 39.5% of GBS, 34.4% of CIDP, 16.1% of ONP patients and 15.4% of NC subjects. IgG antibodies were present in 18.4% of GBS, 12.5% of CIDP, 3.2% of ONP patients and 7.6% of NCs. Of the sera which contained antibodies to P2 protein, only a few reacted with P2 peptides 14-25 or 58-81, but without any consistent pattern of reactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of IgG anti-GD1a antibody with severe Guillain-Barré syndrome

We earlier reported cases of 2 patients with severe acute Guillain-Barré syndrome (GBS) associated with high-IgG anti-GD1a antibody titer. We now have investigated the autoantibody against GD1a or GM1 in 37 GBS patients using the enzyme-linked immunosorbent assay and have found a statistically significant association between IgG anti-GD1a antibody and the severity of the disease (need of a respirator for more than 1 month and a poor functional prognosis 3 months after neurologic onset). An autopsy which showed severe GBS associated with IgG anti-GD1a antibody produced the following findings: (1) severe axonal degeneration and segmental demyelination of peripheral nerves; (2) lymphocytic infiltration; and (3) marked central chromatolysis of the lower motoneurons.

Effects of ganglioside administration on experimental autoimmune neuritis induced by peripheral nerve myelin or P2-specific T cell lines

We studied the effects of ganglioside administration in two animal models of inflammatory demyelinating polyneuropathy. We administered a mixture of bovine brain gangliosides intraperitoneally to Lewis rats with myelin-induced or T cell line-mediated experimental autoimmune neuritis (EAN). Under the experimental conditions we had chosen, we only detected marginal but not statistically significant effects on disease course and severity, as evidenced by motor function, electrophysiological findings, and morphological signs of inflammation and demyelination. There was no significant induction of antibody production against gangliosides, and we did not detect signs of increased cellular reactivity towards gangliosides. We conclude that the administration of gangliosides modulates EAN at best marginally, and does not induce a cellular or humoral immune reaction.

Childhood peripheral neuropathy with autoantibodies to myelin glycoprotein P0

The serum of a 4-year-old child with severe hypertrophic peripheral neuropathy contained high-titer polyclonal antibodies, mainly of IgG class, reacting with the 30-kd P0 glycoprotein of peripheral nerve. This was demonstrated by indirect immunofluorescence, immunoblot analysis of myelin proteins, and enzyme-linked immunosorbent assay with purified P0 glycoprotein. The antibodies did not react with myelin-associated glycoprotein, sulfated glycuronic acid-containing paragloboside (SGPG and SGLPG), or other peripheral nerve glycolipids or gangliosides. To our knowledge this is the first report of strong antibody activity specifically directed against P0. This antibody may play a causative role in the pathogenesis of the peripheral neuropathy in this patient.

Effects of Guillain-Barré sera containing antibodies against glycolipids in cultures of rat Schwann cells and sensory neurons

Serum samples from 52 patients with the acute Guillain-Barré syndrome (GBS), 19 patients with other neurological disorders, and 18 healthy volunteers were tested for cytotoxicity in cultures of rat Schwann cells and dorsal root ganglion neurons. The samples were also examined by enzyme-linked immunosorbent assay for IgG and IgM antibodies against various acidic and neutral glycolipids. Samples from 16 of the 52 (31%) acute GBS patients and from 1 of the 6 patients with chronic inflammatory demyelinating polyneuropathy produced myelin breakdown in culture. Although 10 of the 16 cytotoxic acute GBS serum samples contained anti-glycolipid immunoglobulins, there was no correlation in individual samples between cytotoxic activity and the presence of antibodies against specific glycolipids. While our results do not exclude a role for anti-glycolipid antibodies in the pathogenesis of the acute GBS, the cytotoxic effects of acute GBS serum in cultures of Schwann cells and sensory neurons are probably not due to these antibodies alone.

Influence of gangliosides on experimental allergic neuritis

The development of myelin-induced experimental allergic neuritis (EAN) in Lewis rats can be depressed and delayed by adding a ganglioside mixture (GM1, GD1a, GD1b, GT1b) to the immunization compound; however, gangliosides may enhance the induction of adjuvant arthritis. Antibodies against multiple gangliosides are produced in rats after immunization with gangliosides after addition of myelin, but only low titers can be detected in animals immunized with myelin and complete Freund's adjuvant alone. We conclude that this antibody production is not the result of peripheral nerve inflammation but depends rather from external applied gangliosides.

Antibodies to acidic glycolipids in Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy

Using an enzyme-linked immunosorbent assay and a thin-layer chromatography-immunostaining procedure, we detected serum antibodies against acidic glycolipids in 36 of 53 patients with Guillain-Barré syndrome (GBS) and 8 of 16 patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Although we also found anti-acidic glycolipid antibodies in 4 of 13 patients with other neurological diseases; 2 of 10 patients with multiple sclerosis; 8 of 33 patients with inflammatory, infectious, allergic or autoimmune disorders and 3 of 32 healthy subjects, the levels of antibodies in these controls were much lower than in GBS patients. There were several patterns of reactivity of GBS sera including antibodies to LM1 and HexLM1, GM1 or GD1b or both, various other gangliosides, sulfated glycolipids, and as yet unidentified glycolipids. Sera from 30% of GBS patients had antibodies against two or more antigenically distinct acidic glycolipid antigens. Levels of anti-acidic glycolipid antibodies correlated with clinical symptoms in 9 of 11 GBS patients. While the increased incidence of antibodies to acidic glycolipids in patients with GBS (P less than 0.001) and CIDP (P less than 0.025) compared to controls could be an epiphenomenon, anti-acidic glycolipid antibodies may play a role in nerve injury in some GBS and CIDP patients.

Anti-GM1 IgA antibodies in Guillain-Barré syndrome

Serum anti-GM1 IgA antibodies were detected in 15 of 53 (28%) patients with the acute Guillain-Barré syndrome (GBS) and in one of 26 (4%) patients with other neurological diseases. Although nine GBS patients had anti-GM1 IgA titers of 1:200 or less, six patients had titers of 1:800 or more. Some GBS patients with anti-GM1 IgA antibodies also had antibodies against GD1b or GM2 or both. The presence of markedly elevated anti-GM1 IgA was associated with a poor clinical outcome at 6 and 12 months following onset of the GBS. The possible pathogenetic role of anti-GM1 IgA antibodies remains to be established.

Effects of gangliosides on the expression of autoimmune demyelination in the peripheral nervous system

To test whether gangliosides (GA) might exert neuritogenic effects in vivo, experimental allergic neuritis (EAN) was studied clinically, neuropathologically, and immunologically in Lewis rats immunized with bovine peripheral nerve, P2 myelin protein, P2 myelin protein plus two different doses of GA, P2 with galactocerebroside (GC), and GA alone, each emulsified in adjuvant. All except the GA-treated group developed signs of EAN between days 11 and 14 after the injection. Rats immunized with P2 alone were the most severely affected. Rats given P2 plus GA and those given P2 plus GC displayed a significantly lower clinical score. Histological analysis revealed a comparable degree of inflammation of the peripheral nervous system and demyelination in the spinal nerve roots of bovine peripheral nerve- and P2-immunized rats. The P2 plus GA and P2 plus GC groups revealed similar degrees of pathology in the spinal nerve roots but the latter group stood apart from the rest in that it showed widespread peripheral nervous system changes extending distally into the sciatic nerve. Serological analysis demonstrated that P2 and GC, but not GA, elicited antibody (IgG) responses, but there was no correlation between antibody titer and clinical or histological involvement. The present data fail to support an enhancing role for gangliosides in the expression of EAN and, by extrapolation, in the Guillain-Barré syndrome, for which EAN serves as the laboratory model, and in which suggestions have been made that antibodies to GA may have pathogenetic significance.