Predictive value of anti-GM1 ganglioside antibodies in neuromuscular diseases: a study of 180 sera

The presence and clinical significance of autoantibodies in amyotrophic lateral sclerosis: a narrative review

Amyotrophic lateral sclerosis (ALS) is a debilitating and rapidly fatal neurodegenerative disease, which is characterized by the selective loss of the upper and lower motor neurons. The pathogenesis of ALS remains to be elucidated and has been connected to genetic, environmental and immune conditions. Evidence from clinical and experimental studies has suggested that the immune system played an important role in ALS pathophysiology. Autoantibodies are essential components of the immune system. Several autoantibodies directed at antigens associated with ALS pathogenesis have been identified in the serum and/or cerebrospinal fluid of ALS patients. The aim of this review is to summarize the presence and clinical significance of autoantibodies in ALS.

Ganglioside GM1 and the Central Nervous System

GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

Gangliosides in the Brain: Physiology, Pathophysiology and Therapeutic Applications

Gangliosides are glycosphingolipids highly abundant in the nervous system, and carry most of the sialic acid residues in the brain. Gangliosides are enriched in cell membrane microdomains ("lipid rafts") and play important roles in the modulation of membrane proteins and ion channels, in cell signaling and in the communication among cells. The importance of gangliosides in the brain is highlighted by the fact that loss of function mutations in ganglioside biosynthetic enzymes result in severe neurodegenerative disorders, often characterized by very early or childhood onset. In addition, changes in the ganglioside profile (i.e., in the relative abundance of specific gangliosides) were reported in healthy aging and in common neurological conditions, including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis and epilepsy. At least in HD, PD and in some forms of epilepsy, experimental evidence strongly suggests a potential role of gangliosides in disease pathogenesis and potential treatment. In this review, we will summarize ganglioside functions that are crucial to maintain brain health, we will review changes in ganglioside levels that occur in major neurological conditions and we will discuss their contribution to cellular dysfunctions and disease pathogenesis. Finally, we will review evidence of the beneficial roles exerted by gangliosides, GM1 in particular, in disease models and in clinical trials.

Most of anti-glycolipid IgG-antibodies associated to neurological disorders occur without their IgM counterpart

Background

Different neurological disorders frequently display antibodies against several self-glycans. Increasing evidence supports their pathogenic role; however, far less is known about their origin. Meanwhile, antibodies recognizing non-self glycans appear in normal human serum during immune response to bacteria.

Methods

Using high performance thin layer chromatography-immunostaining, we comparatively evaluated humoral immune response (IgG and IgM immunoreactivity) against glycolipids carrying self-glycans (GM3/GM2/GM1/GD1a/GD1b/GD3/GT1b/GQ1b) and non-self glycans (Forssman/GA1/“A” blood group/Nt7) in sera from 383 patients with neurological disorders along with 87 healthy controls.

Results

In contrast to no healthy controls having anti-self glycan IgG antibodies, one-fifth of patients’ sera had anti-self glycan IgG antibodies: remarkably, 60% of these occurred without IgM antibodies of the same specificity. Contrary to this unusual fact (anti-self glycan IgG occurrence without simultaneous presence of IgM having the same specificity ~ IgG/IgM discordance), all IgG antibodies against non-self glycans occurred simultaneously with their IgM antibody counterpart (i.e. 0% discordance). When analyzed closer, the IgG/IgM discordance frequency for anti-self glycans exhibited a dual trend: below 40% for IgG antibodies against GM2, GM1 and GD1b, and greater than 53% for IgG antibodies against the remaining self glycans. Interestingly, this discordance behavior was common to several different neurological disorders.

Conclusions

Classic immunology principles indicate this anti-self glycan IgG/IgM discordance should not occur in an antibody response; its unusual presence is discussed within the “binding site drift hypothesis” context, where anti-self glycan IgG antibodies could originate from pre-existing IgG recognizing structurally-related non-self glycans.

Electronic supplementary material

The online version of this article (10.1186/s12929-019-0562-5) contains supplementary material, which is available to authorized users.

Anti-ganglioside antibodies in amyotrophic lateral sclerosis revisited

BACKGROUND

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disorder with typical onset in the 5th- 6th decade of life. The hypothesis of an autoimmune origin of ALS receives less attention today, but immunological phenomena still seem to be involved and mechanisms such as protective autoimmunity may be important. Detection of antibodies against a variety of gangliosides has been repeatedly described in ALS-patients by several authors, but widely differing frequencies and titres have been reported. Therefore, we investigated the presence of six common antibodies with a commercially available test panel for GA1, GM1, GM2, GD1a, GD1b and GQ1b in a large group of clinically well-characterized ALS patients and compared them to a collective of 200 healthy blood donors.

METHODS

IgG and IgM antibodies to the six gangliosides asialoGM1 (GA1), GM1, GM2, GD1a, GD1b, GQ1b were determined by GanglioCombi ELISA in sera of 84 ALS patients. Results were expressed as a %-ratio of a highly positive control and categorized as negative (<30%), borderline (30-50%), moderately (50-100%) and strongly positive (>100%). The values obtained from 200 Swiss blood donors served as a reference group.

RESULTS

In twenty-two (26.2%) ALS-patients elevated anti-ganglioside antibodies could be detected: Taking all subspecific antibodies together, IgG antibodies were found in 9/84 (10.7%) and IgM in 15/84 (17.9%) patients. There was no correlation between age, gender, site of onset or survival and anti-ganglioside-positive/-negative titres in ALS-patients. No statistically significant difference in the frequency of anti-ganglioside antibodies compared to the group of healthy blood donors was found.

CONCLUSION

Even with this more comprehensive approach, anti-ganglioside antibody frequencies and patterns in our ALS cohort closely resembled the values measured in healthy controls. In accordance with other studies, we did not observe any association of a distinct ALS phenotype with elevated anti-ganglioside antibodies or an impact on survival.

Pathogenic role of ganglioside metabolism in neurodegenerative diseases

Ganglioside metabolism is altered in several neurodegenerative diseases, and this may participate in several events related to the pathogenesis of these diseases. Most changes occur in specific areas of the brain and their distinct membrane microdomains or lipid rafts. Antiganglioside antibodies may be involved in dysfunction of the blood-brain barrier and disease progression in these diseases. In lipid rafts, interactions of glycosphingolipids, including ganglioside, with proteins may be responsible for the misfolding events that cause the fibril and/or aggregate processing of disease-specific proteins, such as α-synuclein, in Parkinson's disease, huntingtin protein in Huntington's disease, and copper-zinc superoxide dismutase in amyotrophic lateral sclerosis. Targeting ganglioside metabolism may represent an underexploited opportunity to design novel therapeutic strategies for neurodegeneration in these diseases.

Antibodies to Glycoproteins Shared by Human Peripheral Nerve and Campylobacter jejuni in Patients with Multifocal Motor Neuropathy

We have tested serum samples from 24 patients with multifocal motor neuropathy (MMN) for reactivity to ganglioside GM1 and to Gal( β 1-3)GalNAc-bearing glycoproteins isolated from human peripheral nerve and from Campylobacter jejuni (Cj) serotype O:19. IgM anti-GM1 antibodies were detected by ELISA in 11 patients (45.8%) with MMN and in only one subject (4%) from the control group. Western blots showed positive reactivity of sera from 6 patients (25%) with MMN to several Gal( β 1-3)GalNAc-bearing glycoproteins from human peripheral nerve and from Cj O:19 isolates. Sera from three patients (12.5%) with MMN showed positively reactive bands with similar electrophoretic mobility in all isolates (60-62 kDa, 48-51 kDa, 42 kDa, and 38 kDa). All six patients showed positive reactivity to 48-52 kDa protein isolated from human peripheral nerve. Increased titer of IgG antibodies to 60-62 kDa protein isolated from Cj O:19 associated with Guillain-Barré syndrome was detected in three patients, and their serum showed also IgG positive reactivity to peripheral nerve antigen with the same electrophoretic mobility. One of these patients had a previous history of Cj infection which suggests the possibility that Cj may be also involved in the pathogenesis of MMN.

Peripheral neuropathy: clinical and electrophysiological considerations

This article is a primer on the pathophysiology and clinical evaluation of peripheral neuropathy for the radiologist. Magnetic resonance neurography has utility in the diagnosis of many focal peripheral nerve lesions. When combined with history, examination, electrophysiology, and laboratory data, future advancements in high-field magnetic resonance neurography may play an increasingly important role in the evaluation of patients with peripheral neuropathy.

Antibodies to heteromeric glycolipid complexes in multifocal motor neuropathy

BACKGROUND

Measurement of anti-GM1 IgM antibodies in multifocal motor neuropathy (MMN) sera is confounded by relatively low sensitivity that limits clinical usefulness. Combinatorial assay methods, in which antibodies react to heteromeric complexes of two or more glycolipids, are being increasingly applied to this area of diagnostic testing.

METHODS

A newly developed combinatorial glycoarray able to identify antibodies to 45 different heteromeric glycolipid complexes and their 10 individual glycolipid components was applied to a randomly selected population of 33 MMN cases and 57 normal or disease controls. Comparison with an enzyme-linked immunosorbent assay (ELISA) was conducted for selected single glycolipids and their complexes.

RESULTS

By ELISA, 22/33 MMN cases had detectable anti-GM1 IgM antibodies, whereas 19/33 MMN samples were positive for anti-GM1 antibodies by glycoarray. Analysis of variance (anova) revealed that of the 55 possible single glycolipids and their 1:1 complexes, antibodies to the GM1:galactocerebroside (GM1:GalC) complex were most significantly associated with MMN, returning 33/33 MMN samples as positive by glycoarray and 29/33 positive by ELISA. Regression analysis revealed a high correlation in absolute values between ELISA and glycoarray. Receiver operator characteristic analysis revealed insignificantly different diagnostic performance between the two methods. However, the glycoarray appeared to offer slightly improved sensitivity by identifying antibodies in four ELISA-negative samples.

CONCLUSIONS

The use of combinatorial glycoarray or ELISA increased the diagnostic sensitivity of anti-glycolipid antibody testing in this cohort of MMN cases, without significantly affecting specificity, and may be a useful assay modification for routine clinical screening.

Predicting a positive response to intravenous immunoglobulin in isolated lower motor neuron syndromes

OBJECTIVE

To determine clinically related characteristics in patients with pure lower motor neuron (LMN) syndromes, not fulfilling accepted diagnostic criteria, who were likely to respond to intravenous immunoglobulin (IVIg) treatment.

METHODS

Demographic, clinical, laboratory and neurophysiological characteristics were prospectively collected from patients with undifferentiated isolated LMN syndromes who were then treated with IVIg. Patients were classified as either responders or non-responders to therapy with IVIg based on clinical data and the two groups were compared.

RESULTS

From a total cohort of 42 patients (30 males, 12 females, aged 18-83 years), 31 patients responded to IVIg and 11 did not. Compared to patients that developed progressive neurological decline, responders were typically younger (45.8 compared to 56.0 years, P<0.05) and had upper limb (83.9% compared to 63.6%, NS), unilateral (80.6% compared to 45.5%, P<0.05), and isolated distal (54.1% compared to 9.1%, P<0.05) weakness. Patients with predominantly upper limb, asymmetrical, and distal weakness were more likely to respond to IVIg therapy. Of the patients who responded to treatment, only 12.9% had detectable GM(1) antibodies and conduction block (not fulfilling diagnostic criteria) was only identified in 22.6%.

CONCLUSIONS

More than 70% of patients with pure LMN syndromes from the present series responded to treatment with IVIg therapy, despite a low prevalence of detectable GM(1) antibodies and conduction block. Patients with isolated LMN presentations, not fulfilling accepted diagnostic criteria, may respond to IVIg therapy, irrespective of the presence of conduction block or GM(1) antibodies, and should be given an empirical trial of IVIg to determine treatment responsiveness.

Glatiramer acetate immunization induces specific antibody and cytokine responses in ALS patients

We assessed humoral and cytokine responses in monthly plasma samples from ALS patients who received glatiramer acetate (GA) immunization every day or every other week, or remained untreated (control) from a six-month phase II trial. Samples were evaluated by GA-specific ELISA assays for detection of combined immunoglobulin (Ig) classes (IgM,A,G), IgG alone, and IgG subclasses (IgG1, IgG2, IgG3, and IgG4). T-helper (Th) type 1 and 2 (Th1 and Th2) cytokine levels were determined by flow cytometric cytokine bead arrays. Fourteen of 21 GA-immunized patients produced anti-GA Ig responses. Those treated every day produced anti-GA responses within one month, while those treated every other week exhibited responses by month two. All anti-GA IgG subclass concentrations were increased in excess of 4.2-fold in plasma from treated patients, and anti-GA IgG1 comprised the majority of the humoral response. Mean plasma cytokine levels were statistically indistinguishable between treatment regimens; however, stratification by patient and time on study showed more prevalent trends in changes of Th1 or Th2 cytokine levels following GA treatment every other week or every day, respectively. These data show significant humoral responses and cytokine trends following GA immunization in ALS patients.

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.

Antibody testing in peripheral neuropathies

Many autoantibodies have been described in association with peripheral neuropathy, but the use of antibody testing in clinical practice remains a matter of some debate. Serum autoantibodies to gangliosides or glycoproteins are implicated in a variety of sensory and motor neuropathy syndromes. Paraneoplastic antibodies help identify patients who have a neuropathy related to an underlying malignancy. Detection of an autoantibody in the right clinical setting provides some evidence that the peripheral nerve disturbance is immune mediated and that immunomodulatory therapy may be of benefit.

A case of Lewis–Sumner syndrome with conduction abnormalities only in the brachial plexus and roots

We present a case of subacute weakness of one hand with unusual sensory involvement including the upper thorax. Despite normal distal conduction studies, a clinical diagnosis of Lewis-Sumner syndrome was made and the patient responded well to intravenous immunoglobulins. Repeated studies after clinical exacerbation finally proved the demyelinating nature of the neuropathy using proximal magnetic nerve stimulation. This case underlies the importance of seeking proximal conduction blocks in patients with suspected demyelinating neuropathy.

Multifocal motor neuropathy: current concepts and controversies

Multifocal motor neuropathy (MMN) is now a well-defined purely motor multineuropathy characterized by the presence of multifocal partial motor conduction blocks (CB), frequent association with anti-GM1 IgM antibodies, and usually a good response to high-dose intravenous immunoglobulin (IVIg) therapy. However, several issues remain to be clarified in the diagnosis, pathogenesis, and therapy of this condition including its nosological position and its relation to other chronic dysimmune neuropathies; the degree of CB necessary for the diagnosis of MMN; the existence of an axonal form of MMN; the pathophysiological basis of CB; the pathogenetic role of antiganglioside antibodies; the mechanism of action of IVIg treatments in MMN and the most effective regimen; and the treatment to be used in unresponsive patients. These issues are addressed in this review of the main clinical, electrophysiological, immunological, and therapeutic features of this neuropathy.

Autoantibody testing

Recent advances in neuroimmunology have led to improvements in the pathogenesis, diagnosis, prognosis, and treatment of many neuromuscular disorders. The value of autoantibody testing is increasing steadily in neurologic practice. Not all antibodies have a high yield in diagnosis. In some disorders, such as generalized adult onset of myasthenia gravis, Lambert-Eaton myasthenic syndrome,Miller Fisher syndrome, and multifocal motor neuropathy,autoantibody tests provide accurate diagnosis and can be considered biologic markers of these disorders.

Serum IgM anti-GM1 ganglioside antibodies in lower motor neuron syndromes

Lower motor neuron syndromes (LMNS) are heterogenous conditions, which include patients with progressive lower motor neuron disease (LMND) and cases with the clinical phenotype of motor neuropathy (MN). The aim of this study was to estimate the IgM anti-GM1 ganglioside antibodies titer and the ratio of the light chains in order to define the presence of autoimmunity process in particular cases with LMNS. Twenty-eight patients were diagnosed with LMND and 15 patients were diagnosed with MN (10 patients with multifocal motor neuropathy with conduction block, five patients with MN without conduction block). Total of 103 patients with classical amyotrophic lateral sclerosis (ALS) and 50 healthy, age-matched persons were also tested. The IgM anti-GM1 ganglioside titer and the ratio of lambda/kappa light chains in serum were determined using the ELISA technique. High titer of IgM anti-GM1 antibodies were detected in serum of 46% LMND patients, 80% of MN patients, and 18% of the classical ALS cases. An elevated ratio of lambda/kappa light chains appeared in 18% of LMND patients, and in 67% of the MN cases. The lambda/kappa light chains ratio was normal in all ALS patients. The presence of elevated titer of IgM anti-GM1 ganglioside antibodies and the changed ratio of the light chains supports the presence of autoimmune process in LMNS and may provide clues for their management.

Coincident Acetylcholine Receptor Antibody and Anti-Asialo GM1 Antibody in a Young Male

Coexistence of myasthenia gravis with an immunologically mediated neuropathy syndrome is rare. We present a young male patient with a history of generalized muscle weakness and fatigue with electrophysiological evidence of both a motor neuron syndrome and a neuromuscular junction abnormality accompanied by pathologic evidence of denervation with muscle biopsy. Laboratory evidence for both acetylcholine receptor (AchR) antibodies and anti-asialo GM1 antibodies, both of high levels, was found. The patient's fatigue and weakness showed an objective response to pyridostigmine, prednisone, and immunoglobulin therapy over a period of 9 months.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a recently identified peripheral nerve disorder characterized by progressive, predominantly distal, asymmetric limb weakness mostly affecting upper limbs, minimal or no sensory impairment, and by the presence on nerve conduction studies of multifocal persistent partial conduction blocks on motor but not sensory nerves. The etiopathogenesis of MMN is not known, but there is some evidence, based mostly on the clinical improvement after immunological therapies, that the disease has an immunological basis. Antibodies, mostly IgM, to the gangliosides GM1, and though less frequently, GM2 and GD1a, are frequently detected in patients' sera, helping in the diagnosis of this disease. Even if there is some experimental evidence that these antibodies may be pathogenic in vitro, their role in the neuropathy remains to be established. Patients with MMN do not usually respond to steroids or plasma exchange, which may occasionally worsen the symptoms, while the efficacy of cyclophosphamide is limited by its relevant side effects. More than 80% of MMN patients rapidly improve with high dose intravenous immunoglobulin therapy (IVIg). The effect of this therapy is, however, transient and improvement has to be maintained with periodic infusions. A positive response to interferon-beta has been recently reported in a minority of patients, some of whom were resistant to IVIg. Even if many progresses have been made on the diagnosis and therapy of MMN, there are still several issues on the nosological position, etiopathogenesis and long-term treatment of this neuropathy that need to be clarified.

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.

Antiganglioside GM1 antibodies and their complement activating capacity in central and peripheral nervous system disorders and in controls

So far, the pathogenic significance and use for diagnosis of antiganglioside GM1 antibodies (anti-GM1) are unclear. We therefore compared serum IgM and IgG antimonosialo ganglioside GM1 levels of 33 patients with presumed immune-mediated neuropathies, 100 patients with various other central or peripheral neurological disorders, and 110 controls by ELISA. We also measured the complement-activating capacity of anti-GM1 by C5b-9-GM1-ELISA to evaluate its value to distinguish between pathogenic and nonpathogenic autoantibodies. Low levels of anti-GM1 were observed in all disease categories and in controls (healthy blood donors). Twenty-four of the controls including the 10 with the highest serum IgM or IgG anti-GM1 were examined for neurological disorders in a double-blind checkup study. In the patients, elevated IgM anti-GM1 levels were predominantly found in those with neuropathies (NP), but barely in patients with central nervous system disease (CNSD). We found elevated IgG anti-GM1 levels predominantly in patients with NP of inflammatory origin (multifocal motor neuropathy, chronic inflammatory demyelinating polyneuropathy or Guillain-Barré syndrome), rarely in patients with NP of noninflammatory origin or CNSD, but not in the control disease group myasthenia gravis (MG). Median levels of IgM-, IgG-, (IgM+IgG)-, and C5b-9-binding anti-GM1 were significantly higher in patients with inflammatory NP as compared to the controls (p < 0.025). In addition, median levels of IgG- and (IgM+IgG)-anti-GM1 were significantly higher in inflammatory NP versus CNSD. Elevated complement-binding activity was associated with low or elevated IgM and/or IgG anti-GM1. Nevertheless, there was a significant correlation between anti-GM1 level (IgM+IgG) and the respective complement-activating capacity (r = 0.758; n = 243). Estimation of anti-GM1 and their respective complement-activating capacity may be helpful in the diagnosis of inflammatory neuropathies. However, neither an elevated anti-GM1 level nor an increased C5b-9 binding seems specific for a given disease category (e.g. peripheral nerve disease) nor a disease process (e.g. demyelination or inflammation).

Results of testing for anti-GM1 antibodies

We used an ELISA technique to measure IgG and IgM antibodies to the ganglioside GM1, with the results expressed in arbitrary units. We tested 1007 sera from patients with peripheral neuropathy or muscle weakness. For IgG and IgM antibodies, the distribution of results differed significantly from a normal distribution. In the patient group, 81 of 1007 sera had elevated levels of IgG antibodies (> 10 units). Of these, 11 patients had very high levels (> 50 units). These 11 patients had diagnoses of GBS (4), motor neurone disease (3) or non-specific idiopathic neuropathy (4). For IgM antibodies, 115 of 1007 sera were positive (> 20 units). Of these, 18 patients had very high levels (> 50 units). These 18 patients had diagnoses of Guillain-Barré syndrome or Miller Fisher syndrome (4), multifocal motor neuropathy (4), motor neurone disease (2), non-specific neuropathy (2). We conclude that anti-GM1 antibodies in high titre are uncommon. Patients with multifocal motor neuropathy have high levels of antibody. However, patients with other disorders may also have high levels, so that anti-GM1 antibody levels alone are not a specific test for multifocal motor neuropathy. We found that antibodies to GM1 were present in the sera of patients with chronic idiopathic neuropathy, leading us to suggest that these antibodies may sometimes arise as a secondary response to disease.

Anti-neural antibodies in serum and cerebrospinal fluid of amyotrophic lateral sclerosis (ALS) patients

OBJECTIVES

An autoimmune basis has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). This hypothesis is supported by the presence of antibodies that interact with motoneuron antigens in serum of these patients. Against autoimmunity are the discrepances in the frequency of the antibodies appearance and also failure of immunosuppression. The aim of our study was to evaluate the titer of antibodies against GM1-gangliosides, AGM1-gangliosides and anti-sulfatides in paired serum and cerebrospinal fluid samples in the ALS patients.

MATERIAL AND METHODS

Serum of 103 and CSF of 79 patients with ALS was examined. The "disease controls" consisted of 22 cases of other motor neuron diseases and 50 healthy, age-matched normals. CSF was drawn at the same time from 79 ALS patients, 6 cases of the "disease controls" and 50 normals. To study the titer of antibodies against GM1-gangliosides, AGM1-gangliosides and sulfatides the ELISA technique has been applied.

RESULTS

An increased titer against GM1-gangliosides, AGM1-gangliosides and sulfatides in ALS appeared in serum in 18%, 32%, and 11%, resp., in the "disease controls" the increased antibodies titer appeared in single cases. In CSF the appropriate values in ALS were 20%, 15%, 8%, resp. In the "disease controls" a high antibodies titer was a rare finding.

CONCLUSIONS

It is concluded that in some ALS cases and also in some patients with other motor neuron diseases an autoimmune mechanism may contribute to motor neuron injury.

Inter-laboratory validation of an ELISA for the determination of serum anti-ganglioside antibodies

Anti-ganglioside antibodies are frequently sought in the sera of patients with autoimmune peripheral neuropathy, using an enzyme-linked immunosorbent assay (ELISA) as the principal method for antibody detection. Wide variations in assay performance between laboratories have been reported. In this study, we established a standardized ELISA method between laboratories within the European Inflammatory Neuropathy Cause and Treatment (INCAT) group and determined the inter-laboratory variance in assay performance using both the standardized INCAT method and in-house local methods. As expected, the inter-laboratory variances were greater using local methods than using the standardized method, producing titre estimates which could be 24.8 or 7.6 times larger or smaller, respectively, than the true means for these laboratories. Using the standardized method, the within laboratory measurement error accounted for 41% of the inter-laboratory variation, providing a theoretical upper limit to which technical improvements within laboratories could reduce inter-laboratory variation. These data describe the intrinsic weaknesses within the widely used ganglioside antibody ELISA methods and reinforce the importance of inter-laboratory cooperation within this area. Standardized serological reagents used in this study are available from INCAT members.

Antibodies against peripheral myelin glycolipids in people with HIV infection

Plasma samples from 35 individuals with HIV infection but without clinical peripheral neuropathy were screened by ELISA for IgM and IgG antibodies against peripheral myelin. Eighteen of the 35 samples (51%) showed IgM reactivity and 11 (31%) showed IgG reactivity. By comparison, none of 48 samples from healthy blood donors showed IgM or IgG reactivity. Epitopes reacting with these antibodies were identified by TLC immunostaining as sulphatide (GalS) and the gangliosides GM1, GD1a and GD1b. Plasma samples from four people with HIV infection and neuropathy (HIV+PN), six HIV-seronegative individuals with IgM paraproteinaemic demyelinating neuropathy (IgMPDN) and 12 HIV-seronegative individuals with a variety of other neurological disorders (HIV-OND) were also investigated. Two of the four HIV+PN samples showed IgM reactivity with GalS; and two showed IgG reactivity against GalS. Of the six IgMPDN samples, three showed IgM reactivity with GalS. These data indicate that antibodies against peripheral myelin glycolipids, in particular GalS, occur more frequently in HIV infection than in HIV-seronegative individuals with and without neurological disease, and may contribute to subclinical neuropathy in HIV infection.

Demyelinating inflammatory neuropathies, including Guillain-Barré syndrome

The highly complex and multiple mechanisms responsible for the development of demyelinating neuropathies are reviewed, in particular Guillain-Barré syndrome and its variant Miller Fisher syndrome, chronic inflammatory demyelinating neuropathy, multifocal motor neuropathy, anti-myelin-associated glycoprotein neuropathy, as well as experimental models. Recent investigations into the role of auto antibodies against myelin proteins, or glycolipids have given insights into the pathogenesis of demyelinating inflammatory neuropathies.

Serum autoantibodies to neurofilament proteins in sporadic amyotrophic lateral sclerosis

Anti-neurofilament (NF) autoantibodies were searched for by enzyme-linked immunosorbent assays (ELISA) in the serum from 85 sporadic amyotrophic lateral sclerosis (ALS) patients, 98 healthy controls and 79 patients with unrelated immunological diseases (Guillain-Barré syndrome, myasthenia gravis and multiple sclerosis). ELISA cutoff value was determined as mean control levels +2 SD and it corresponded to a specificity of 94%. Such high level antibodies were detected in 24.7% of ALS patients contrasting with 12.6% of neurological controls (P<0.05) and only 6.1% of healthy subjects (P<5.10[-4]). In ALS, anti-NF antibodies were significantly associated with a slow evolution, as measured by the mean time spent in the initial functional states. They did not relate with age, sex and clinical form. The predominant isotype of the anti-NF antibodies was IgM lambda by ELISA. In contrast to negative sera, indirect immunohistochemical studies demonstrated that most sera positive for anti-NF antibodies reacted with axons with predominant isotypes restricted to IgM lambda. By using Western blotting, small amounts of serum monoclonal IgM were found with a high frequency in anti-NF antibody-positive patients. These results suggest the possible involvement of anti-NF antibodies in an autoimmune process in a subgroup of ALS patients.

Antibody panels in idiopathic polyneuropathy and motor neuron disease

We prospectively evaluated patients with idiopathic polyneuropathy (PN) and motor neuron disease (MND) with commercial antibody (Ab) panels. Patients with sensorimotor PN received a "sensorimotor neuropathy profile" [3-sulfated glucuronyl paragloboside (SGPG)/myelin-associated glycoprotein (MAG), GM1, asialo-GM1, GD1b, Hu, sulfatide]. Motor neuropathy or MND patients underwent a "motor neuropathy profile" (SGPG/MAG, GM1, asialo-GM1). Seven of 78 patients (9.0%) with sensorimotor PN and 3 of 44 patients (6.8%) with MND had abnormal panels. None of 60 patients with axonal sensory or sensorimotor PN had antisulfatide Ab. Seven of 13 patients (54%) with multifocal motor neuropathy had abnormal panels, with 6 seropositive to GM1. We found abnormal Ab panels in fewer than 10% of patients with idiopathic sensorimotor PN and MND. Moreover, abnormal Ab tests often did not relate to the clinical context. Our data do not support the use of commercial Ab panels in the evaluation of patients with idiopathic PN or MND.

Cryptogenic partial epilepsies with anti-GM1 antibodies: a new form of immune-mediated epilepsy?

PURPOSE

We wished to study immune system dysfunction which has been proposed as a potential cause of epilepsy. Epileptogenic action of antibodies directed against GM1 gangliosides was demonstrated in rats, but the potential role of anti-GM1 antibodies in human epilepsy has not yet been studied.

METHODS

We investigated the presence of IgG or IgM anti-GM1 antibodies in the sera of 64 patients with various types of epileptic syndromes: idiopathic generalized epilepsy (IGE) (n = 6), symptomatic or cryptogenic generalized epilepsy (SCGE) (n = 7), symptomatic partial epilepsy (SPE) (n = 26), and cryptogenic partial epilepsy (CPE) (n = 25).

RESULTS

Two patients had elevated titers of IgM anti-GM1 antibodies, one patient had elevated titers of both IgM and IgG anti-GM1 antibodies, and 1 patient had elevated titers of IgG anti-GM1 antibodies. All 4 patients had complex partial seizures (CPS) secondarily generalized, drug resistance, psychiatric disorders, and normal brain imaging. Anti-GM1 antibodies were never associated with IGE, SCGE, or SPE. We compared the reactivity of sera from these patients with the sera from 5 patients with motor neuropathies with conduction block (MNCB) against different gangliosides and concluded that epilepsy sera did not react with the Gal(beta 1-3)GalNAc epitope. Two anti-GM1-positive patients were treated successfully with high-dose intravenous immunoglobulins (IgIV).

CONCLUSIONS

Our findings suggest that detection of anti-GM1 antibodies could allow identification of a subgroup of patients with partial epilepsy associated with an autoimmune response. If anti-GM1 antibodies prove pathogenic, they could be an important prognostic factor for drug resistance and worsening of seizures.

Association of polyclonal anti-GM1 IgM and anti-neurofilament antibodies with CSF oligoclonal bands in a young with amyotrophic lateral sclerosis

INTRODUCTION

The significance of the association of motor neuron syndromes with anti-GM1 antibodies remains unclear. We report the immunological study of a juvenile case of amyotrophic lateral sclerosis (ALS).

MATERIALS AND METHODS

Serum anti-Gm1 and anti-neurofilament antibodies were assayed by ELISA and western blotting and cerebrospinal fluid (CSF) isoelectrofocusing was performed. Immunocytochemical studies were carried out with the patient's serum and CSF on human brain and spinal cord sections.

RESULTS

Serum polyclonal IgM anti-GM1, anti-neurofilament antibodies and CSF oligoclonal bands were detected. Furthermore, an in vitro production of anti-GM1 IgM was demonstrated. Immunocytochemical studies showed cytoplasm motor neuron immunostaining, due to both IgG and IgM, that substantially decreased after immunoabsorption of the serum with bovine neurofilament proteins but not with GM1-containing liposomes. No immunostaining was obtained with CSF. Immunosuppressive treatment with cyclophosphamide and two cycles of plasma exchanges lowered anti-GM1 antibody levels, but did not determine any clinical improvement.

CONCLUSION

To our knowledge, this is the first report of ALS, associated with circulating levels and in vitro production of polyclonal IgM anti-GM1, anti-neurofilament antibodies and CSF oligoclonal bands. These findings suggest the occurrence in our patients of an autoimmune process that could be involved in the pathogenesis of ALS.

Multifocal motor neuropathy with conduction block: a study of 24 patients

Twenty four patients with pure motor neuropathy are reported. The chronic motor involvement associated with fasciculations and cramps, mainly in the arms, led, in most patients, to an initial diagnosis of motor neuron disease. In some patients (nine of 24), there was no appreciable muscle atrophy. Tendon reflexes were often absent or weak. The finding of persistent multifocal conduction block confined to motor nerve fibres raises questions about the nature and the importance of this syndrome. Segmental reduction of motor conduction velocity occurred at the site of the block, but significant slowing of motor nerve conduction was not found outside this site. The response to intravenous IVIg treatment seems to be correlated with the absence of amyotrophy. Patients with little or no amyotrophy had an initial and sustained response to IVIg, and did not develop amyotrophy during the follow up study. They could be considered to have a variant of chronic inflammatory demyelinating polyneuropathy. Patients with pronounced amyotrophy independent of the disease duration did not respond as well to IVIg treatment, suggesting the existence of a distinct entity. Among the patients treated about two thirds who had an initial good response to IVIg had high or significant antiganglioside GM1 (anti-GM1) antibody titres, but there was no correlation between the high titres before treatment and long lasting response to IVIg treatment.

Chronic motor neuropathies: diagnosis, therapy, and pathogenesis

Pure motor neuropathy syndromes resemble amyotrophic lateral sclerosis variants with no upper motor neuron signs. Their identification is important, as, in contrast to amyotrophic lateral sclerosis, they are often immune mediated and treatable. Typically the immune-mediated motor neuropathy syndromes are distal and asymmetrical and progress slowly. The clinical features may help alert the clinician to the diagnosis, but other ancillary evidence such as abnormalities on electrophysiological testing and the presence of serum autoantibodies to neural antigens are helpful in making the diagnosis more secure. Electrophysiological abnormalities include not only motor conduction block but also other evidence of a demyelinative process such as prolonged distal latencies or F-wave abnormalities. High-titer anti-GM1 antibodies occur frequently but more specific patterns of reactivity may be especially helpful. Treatment of these motor neuropathy syndromes includes cyclophosphamide, which we use in combination with plasma exchange, and in some patients, human immune globulin. Clinical responses to therapy may occur within the first 2 to 4 months in patients with motor neuropathy syndromes with demyelinative features, but only become obvious 6 months or later after starting treatment in patients with predominantly axonal disorders.

Pathogenesis and therapy of neuropathies associated with monoclonal gammopathies

Approximately 10% of patients with peripheral neuropathy of otherwise unknown etiology have an associated monoclonal gammopathy. Both the neuropathies and the monoclonal gammopathies in these patients are heterogeneous, but several distinct clinical syndromes that may respond to specific therapies can be recognized. It is important to recognize these syndromes because monoclonal gammopathies also occur in 1% of the normal adult population, and in some cases, monoclonal gammopathies are coincidental and unrelated to the neuropathy. In patients with IgM monoclonal gammopathies, IgM M proteins frequently have autoantibody activity and are implicated in the pathogenesis of the neuropathy. IgM M proteins that bind to myelin-associated glycoprotein (MAG) have been shown to cause demyelinating peripheral neuropathy; anti-GM1 antibody activity is associated with predominantly motor neuropathy, and anti-sulfatide or chondroitin sulfate antibodies are associated with sensory neuropathy. The IgM monoclonal gammopathies may be malignant or nonmalignant, and polyclonal antibodies with the same specificities are associated with similar clinical presentations in the absence of monoclonal gammopathy. IgG or IgA monoclonal gammopathies are associated with neuropathy in patients with osteosclerotic myeloma or the POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy myeloma, and skin changes). Amyloidosis or cryoglobulinemic neuropathies can occur with either IgM or IgG and IgA monoclonal gammopathies. Therapeutic intervention depends on the specific clinical syndrome but is generally directed at removing the autoantibodies, reducing the number of monoclonal B cells, and interfering with the effector mechanisms.

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.

Antiglycolipid antibodies in peripheral neuropathy: fact or fiction?

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