VH gene family utilization of anti-acetylcholine receptor antibodies in experimental autoimmune myasthenia gravis

The immunoglobulin heavy chain (V_H) gene family usage in experimental autoimmune myasthenia gravis (EAMG) model was investigated by RNA slot blot hybridization using V_H gene family specific probes. Anti-acetylcholine receptor (AChR) monoclonal antibodies (mAbs) isolated from susceptible C57BL/6 and resistant BALB/c mice were found to be encoded by V_H genes from at least six different families. The Vgam3.8 family was overrepresented in α-bungarotoxin blocking mAbs. Expression of cross-reactive idiotopes by anti-AChR mAbs was irrespective of the V_H gene family usage. Strain dependent differences in susceptibility for EAMG were not reflected in an aberrant V_H gene family usage of anti-AChR mAbs.     

Neurophysiological and immunohistochemical studies of IgG anti-GM1 monoclonal antibody on neuromuscular transmission: effects in rat neuromuscular junctions

Guillain–Barré syndrome, which is a variant of acute inflammatory neuropathy, is associated with anti-GM1 antibodies and causes ataxia. We investigated the effects of IgG anti-GM1 monoclonal antibody (IgG anti-GM1 mAb) on spontaneous muscle action potentials in a rat spinal cord–muscle co-culture system and the localization of IgG anti-GM1 mAb binding in the rat hemi-diaphragm. The frequency of spontaneous muscle action potentials in innervated muscle cells was acutely inhibited by IgG anti-GM1 mAb. When cultures were pretreated with GM2 synthase antisense oligodeoxynucleotide, IgG anti-GM1 mAb failed to inhibit spontaneous muscle action potentials, demonstrating the importance of the GM1 epitope in the action of IgG anti-GM1 mAb. Immunohistochemistry of rat hemi-diaphragm showed that IgG anti-GM1 mAb binding overlapped with neurofilament 200 (NF200) antibodies staining, but not α-bungarotoxin (α-BuTx) staining, demonstrating that IgG anti-GM1 mAb was localized at the presynaptic nerve terminal. IgG anti-GM1 mAb binding overlapped with syntaxin antibody and S-100 antibody in the nerve terminal. After collagenase treatment, IgG anti-GM1 mAb and NF200 antibodies did not show staining, but α-BuTx selectively stained the hemi-diaphragm. IgG anti-GM1 mAb binds to the presynaptic nerve terminal of neuromuscular junctions. Therefore, we suggest that the inhibitory effect of IgG anti-GM1 mAb on spontaneous muscle action potentials is related to the GM1 epitope in presynaptic motor nerve terminals at the NMJs.     

Somatically mutated member of the human VλVIII gene family encodes anti-myelin-associated glycoprotein (MAG) activity

A highly conserved small family of human V_λ genes was identified by DNA homology to a V_λ gene isolated from a patient with demyelinating peripheral neuropathy, and which encodes an autoantibody with anti-MAG activity. Comparison of the genes indicates that the patient V_λ gene was derived from one of the germline genes. Together with published analyses of other anti-MAG IgM antibodies, which also appear to be mutated in comparison to known germline V genes, these results suggest that development of these pathogenic antibodies may reflect an antigen-driven, T cell-dependent process.     

Use of peptide ligands to analyze the fine specificity of antibodies against asialo GM1

We recently described clone 10, a monoclonal Fab fragment that binds to asialo GM1 (GA1), and three mutated Abs derived from it that also bind GA1 and have a three to four times increase in avidity. We selected a phage display linear heptapeptide library with these four Abs, and an IgM mAb, 156, which binds to GM1 and GD1b, but not to GA1. Peptides with the same motif, KL/VWQXXX, were selected by clones 10 and the two heavy chain mutants 227 and 109. In contrast, the light chain mutant L3 58 selected an entirely different peptide motif, TFGLQSL. Moreover, a different motif, K/SWTNL/MPP, was selected by mAb 156. Although mAbs clone 10 and its mutants 109, 227 and L3 58 all bind only to GA1, differences in their fine specificity were revealed by binding to peptide ligands.     

Anti-ganglioside antibodies alter presynaptic release and calcium influx

Acute motor axonal neuropathy (AMAN) variant of Guillain-Barré syndrome is often associated with IgG anti-GM1 and -GD1a antibodies. The pathophysiological basis of antibody-mediated selective motor nerve dysfunction remains unclear. We investigated the effects of IgG anti-GM1 and -GD1a monoclonal antibodies (mAbs) on neuromuscular transmission and calcium influx in hemidiaphragm preparations and in cultured neurons, respectively, to elucidate mechanisms of Ab-mediated muscle weakness. Anti-GM1 and -GD1a mAbs depressed evoked quantal release to a significant yet different extent, without affecting postsynaptic currents. At equivalent concentrations, anti-GD1b, -GT1b, or sham mAbs did not affect neuromuscular transmission. At fourfold higher concentration, an anti-GD1b mAb (specificity described in immune sensory neuropathies) induced completely reversible blockade. In neuronal cultures, anti-GM1 and -GD1a mAbs significantly reduced depolarization-induced calcium influx. In conclusion, different anti-ganglioside mAbs induce distinct effects on presynaptic transmitter release by reducing calcium influx, suggesting that this is one mechanism of antibody-mediated muscle weakness in AMAN.     

Primary structure of the antigen-binding domains of a human oligodendrocyte-reactive IgM monoclonal antibody derived from a patient with multiple sclerosis.

Several murine IgM monoclonal antibodies (mAbs) promoting remyelination in mice were shown to be germline gene-encoded natural autoantibodies that react with oligodendrocytes and intracellular antigens. Here, we show that human oligodendrocyte-reactive IgM mAb DS1F8 derived from a patient with multiple sclerosis targets microtubule-like structures similar to the murine mAbs. Sequencing of the cDNAs of the variable regions revealed that the antigen-binding domains are also encoded by germline genes. These similarities of mAb DS1F8 to the murine mAbs promoting remyelination suggest that this human mAb is a natural autoantibody. This may imply that the engineering of human autoantibodies for therapy of demyelinating diseases is feasible.     

Patterns of reactivity of human anti-GM1 antibodies with spinal cord and motor neurons.

Human anti-GM1 antibodies from patients with lower motor neuron disease or predominantly motor neuropathy recognize carbohydrate determinants shared by GM1 and related glycolipids and glycoproteins, but the identity of the antigens to which they bind in tissue is unknown. We examined the binding of anti-GM1 antibodies with differing fine specificities to spinal cord, isolated motor neurons, and dorsal root ganglia neurons in order to characterize the tissue antigens. All anti-GM1 antibodies tested bound to the surface of bovine spinal motor neurons and immunostained the gray matter of unfixed sections of spinal cord. The staining was blocked by cholera toxin, which is specific for GM1, indicating that GM1 itself was the target antigen. Binding to white matter was more variable and depended on fixation and the fine specificities of the antibodies. The anti-GM1 antibodies did not bind to dorsal root ganglia neurons in tissue sections or in culture. These studies suggest that the autoantibodies might exert their effect, in part, by binding to GM1 on the surface of motor neurons, and that the absence of binding to dorsal root ganglia neurons might explain the lack of sensory abnormalities in affected patients.     

Electrodiagnostic findings related to anti-GM1 and anti-GQ1b antibodies in Guillain-Barré syndrome

Antibodies against the gangliosides GM1 and GQ1b may induce conduction failure in mice. To investigate their possible site of action in the Guillain-Barré syndrome (GBS), we studied the relation between serum anti-GM1 and anti-GQ1b antibodies and electromyography in 124 GBS patients. Anti-GM1 antibodies were found in 22 (18%) and anti-GQ1b antibodies in 5 (4%) patients. Anti-GM1 antibodies were associated with low distal compound muscle action potential amplitudes and relatively high compound sensory nerve action potential (CSNAP) amplitudes. In none of the patients with anti-GQ1b antibodies could CSNAPs be detected. Patients with anti-GM1 and anti-GQ1b antibodies were heterogenous with respect to electrodiagnostic features exclusive for demyelination or axonal degeneration, although the anti-GM1 positive patients tended to have more axonal degeneration. In conclusion, electromyographic studies indicate selective and more severe damage of motor nerves in patients with anti-GM1 antibodies, while patients with anti-GQ1b antibodies have more severe damage of sensory nerves. These antibodies may interfere with the electrophysiologic properties of different nerve fibers and thereby contribute to the clinical heterogeneity in GBS. © 1997 John Wiley & Sons, Inc. Muscle Nerve, 20: 446–452, 1997     

Autoantibodies to GM1 ganglioside: different reactivity to GM1-liposomes in amyotrophic lateral sclerosis and lower motor neuron disorders

We studied the ability of anti-GM1 ganglioside antibodies to bind to GM1 in a lipid, "membrane-like" environment. Liposomes containing GM1 were synthesized to simulate this environment. We then compared the binding of anti-GM1 a autoantibodies to GM-1-liposomes and to purified GM1. Antibody binding was quantitated using enzyme-linked immunosorbent assay methodology. Our results showed a 250-fold variation in the ability of anti-GM1 antibodies to bind to GM1-liposomes. There was no correlation between GM-1-liposome binding and the carbohydrate specificities of the anti-GM1 antibodies. However, anti-GM1 antibodies from patients with amyotrophic lateral sclerosis (ALS) showed a 4 fold greater binding to GM1-liposomes than antibodies from patients with lower motor neuron (LMN) syndromes. We conclude that a lipid, presumably "membrane-like", environment may greatly influence the degree of anti-GM1 antibody binding to GM1. The low levels of anti-GM1 antibody binding to GM1-liposomes in patients with LMN syndromes may provide a diagnostic means for distinguishing these patients from those with ALS. Anti-GM1 antibodies from patients with ALS may bind especially well to neuronal membranes containing GM1 in vivo.     

Sialic acid and anti-ganglioside M1 antibodies are invaluable biomarkers correlated with the severity of autism spectrum disorder

BackgroundAutism spectrum disorders (ASD) are devastating neurodevelopmental disorders that showed global increased prevalence. They are characterized by impairment of social communication and stereotyped patterns.ObjectiveThis study aimed at measuring the levels of total sialic acid (SA) and anti-ganglioside M1 (anti- GM1) IgG antibodies as essential biomarkers in a cohort of children with ASD to identify their diagnostic yield as well as their correlation with the severity of autistic behaviors.MethodsThe demographic characteristics, anthropometric measurements, and clinical data were recorded. The levels of total plasma SA and serum anti-GM1 IgG antibodies levels were measured in 100 children with ASD and 100 healthy controls. The severity of ASD-related symptoms was assessed by using the Childhood Autism Rating Scale (CARS).ResultsChildren with ASD had significantly higher levels of both SA and anti-GM1 antibodies than healthy controls (p < 0.001). SA showed a statistically significant moderate diagnostic performance while anti-GM1 antibody showed a statistically significant high diagnostic in differentiating severe from mild to moderate autism. Moreover, both SA and anti-GM1 antibodies levels were significantly correlated to the severity of ASD symptoms (p < 0.001).ConclusionThe significantly increased levels of SA and anti-GM1 antibodies in children with ASD and their correlation with autism-related symptoms suggest their possible etiopathogenic role in autism as one of the pediatric autoimmune neuropsychiatric disorders. However, further large-scale studies are still needed to explore their possible bidirectional relationship as biomarkers for autism.     

Anti-ganglioside antibodies and clinical outcome of patients with Guillain-Barré Syndrome in northeast Brazil

OBJECTIVES: The goal of this study was to investigate the frequency of GM1 antibodies and to assess whether exposure to Campylobacter jejuni was associated with a distinct clinical variant of Guillain-Barré Syndrome (GBS) or disease outcome in Rio Grande do Norte, Brazil. MATERIAL AND METHODS: Forty-one patients with a presumed diagnosis of GBS were enrolled and prospectively studied between June 1994 and November 1999. RESULTS: Anti-GM1 was present in 51.2% (n = 21) of patients. The presence of anti-GM1 was significantly associated with acute axonal motor neuropathy when compared to acute inflammatory demyelinating polyneuropathy (P = 0.01). Patients with anti-GM1 antibodies presented distal muscle involvement and fewer sensory deficits. Age, time to nadir and ventilatory assistance were not associated with anti-GM1 antibodies. Eight out of 21 patients (32%) presented with anti-C. jejuni antibodies. Clinical features were similar for patients with GBS with positive and negative C. jejuni antibodies. Anti-GM1 antibodies were associated with C. jejuni infection (P = 0.0005). Presence of anti-GM1 and C. jejuni antibodies did not indicate a worse prognosis. CONCLUSION: Patients with GBS and anti-GM1 antibodies had more distal muscle weakness, fewer sensory deficits, more axonal degeneration and C. jejuni infection, but these findings were not associated with a worse prognosis.     

Antiganglioside antibodies in motor neuron disease and motor dominant neuropathies

Serum antiganglioside antibodies were investigated in motor neuron disease (MND) and in chronic or acute immune-mediated motor-dominant neuropathies. IgM antibody binding to GM1 and GA1, reacting with Gal beta 1-3GalNAc epitope, was seen in 5 out of 26 cases of MND. IgM antibody binding to Gal beta 1-3GalNAc epitope was also detected in 3 out of 3 cases with motor dominant neuropathy with multifocal conduction block (MNMCB). The IgM M-protein in a case with motor dominant neuropathy bound to GM1, GD1b, GM2 but not to GA1. This M-protein may recognize carbohydrate epitope including sialic acid. Antiganglioside antibodies were detected in 11 out of 16 cases with Guillain-Barré syndrome (GBS). Among them, anti-GM1 antibodies were detected in 6 cases. Gal beta 1-3GalNAc epitope was recognized in 3 cases, and GM1 was monospecifically recognized in 3 cases. Thus the binding specificities of anti-GM1 antibody in motor dominant neuropathies were varied. The titers of anti-GM1 antibodies in 1 case with MNMCB and in 6 cases with GBS were more than 1:160, whereas those in MND were less than 1:80. The high titers of antibody in MNMCB and GBS decreased in association with clinical improvement, suggesting that they are closely related with the disease process. Although the titers are low, anti-GM1 antibody in MND may give us a clue to elucidate the pathogenetic mechanisms of this intractable disease.     

Anti-GM1 IgM antibodies in motor neuron disease and neuropathy

We found anti-GM1 IgM antibodies in 23% of 56 patients with motor neuron disease (MND), in 19% of 69 patients with neuropathy, and in 7% of 107 controls with other neurologic and nonneurologic diseases. Most of these patients had anti-GM1 IgM antibody titers of 1:80 or less; slightly higher antibody titers (up to 1:640) were found in 3 patients, 1 with MND and 2 with neuropathy, and very high titers (1:20,480) in a patient with MND and an IgM kappa M protein that reacted with GM1, GD1b, and asialo GM1. Six other patients with anti-GM1 IgM that also bound to GD1b. Reactivity with GD1b did not correlate with anti-GM1 titers but was only present in patients with MND or neuropathy. Anti-GM1 IgM antibodies may be a normal constituent of the human antibody repertoire but their frequency and, in some cases, their levels are higher in patients with MND and neuropathy. The origin and the pathogenetic role of these antibodies in neural impairment remain to be established.     

Ataxic Guillain-Barré syndrome associated with anti-GM1b and anti-GalNAc-GD1a antibodies

Abstract. Ataxic Guillain-Barré syndrome (GBS) associated with anti-GQ1b IgG antibody has been reported. We, however, have had a patient with ataxic GBS who had IgG antibodies to the minor gangliosides GM1b and GalNAc-GD1a, and we therefore retrospectively investigated the clinical features of patients who had antibodies to GM1b or GalNAc-GD1a, but not to GQ1b. Information on patients antecedent illnesses, initial symptoms, neurological signs, and CSF findings was reviewed in those with ataxic GBS or Fisher syndrome (FS) with anti-GM1b or anti-GalNAc-GD1a IgG antibodies. We tested whether the anti-GM1b and anti-GalNAc-GD1a antibodies are cross-reactive and constructed three-dimensional structural models of GM1b and GalNAc-GD1a. Ataxic GBS was diagnosed in 1 of 65 patients who had both anti-GM1b and anti-GalNAc-GD1a antibodies and in 3 of 159 patients who had anti-GM1b antibody without anti-GalNAc-GD1a antibody: FS was diagnosed in 1 of the 159 patients and in 1 of 35 who had anti-GalNAc-GD1a antibody without anti-GM1b antibody. All the patients antibodies to GM1b or GalNAc-GD1a were associated with the IgG isotype. The clinical features of patients with ataxic GBS associated with anti-GM1b or anti-GalNAc-GD1a IgG antibodies did not differ from those of patients who had anti-GQ1b IgG antibody. Absorption study findings for serum from the patient who had both anti-GM1b and anti-GalNAc-GD1a IgG antibodies showed significant absorbance of anti-GM1b IgG antibody by GalNAc-GD1a and of anti-GalNAc-GD1a IgG antibody by GM1b, indicating that these antibodies are cross-reactive. This is the first report of ataxic GBS or FS associated with anti-GM1b or anti-GalNAc-GD1a IgG antibodies. These autoantibodies, as well as anti-GQ1b IgG antibody, may function in the development of some patients with ataxic GBS and FS.     

Lewis rats immunized with GM1 ganglioside do not develop peripheral neuropathy

Elevated levels of anti-GM1 antibodies are associated with motor nerve syndromes. Although there is a lot of circumstantial evidence that anti-GM1 antibodies may be causing the disease, their precise role remains unclear. In order to study the role of anti-GM1 antibodies in the pathogenesis of peripheral neuropathy, eight Lewis rats were injected with GM1 ganglioside mixed with keyhole limpet hemocyanin (KLH) and emulsified with Freund's adjuvant and three rats were immunized with GM1 in liposomes. Although IgM class anti-GM1 antibodies were detected in all animals immunized with GM1, none of the animals exhibited overt signs of neuropathy during 6 months after initial immunization. IgG antibody to GM1 was not produced in any of the animals. There was no pathological evidence of nerve damage. These studies suggest that elevated levels of IgM anti-GM1 antibodies by themselves do not cause nerve damage in rats.     

Restricted use of VH4 Germline segments in an acute multiple sclerosis brain

Multiple sclerosis (MS) cerebrospinal fluid and brain contain increased IgG and oligoclonal bands. Whether this oligoclonal and polyclonal IgG is directed against a disease-relevant antigen remains unknown. To distinguish between random activation versus a targeted B-cell response, we analyzed the IgG heavy chain variable region (V_H) repertoire expressed in different lesions of an acute MS brain. To obtain a representative sample of the V_H repertoire, we constructed directional complementary DNA libraries from plaque-periplaque messenger RNA and amplified V_H regions from the library by nested polymerase chain reaction. When MS V_H sequences were aligned to germline segments, about 60% of different V_H sequences in the acute MS brain were V_H4 germline segments, significantly greater than the known approximately 20% V_H4 germline prevalence. Specific V_H sequences were overrepresented and expressed at multiple plaque sites. Within some overexpressed populations, there were distinct sequence differences (clonal variants) indicative of clonal expansion. Alignment of V_H sequences to their closest germline counterparts revealed extensive somatic mutation and the preferential accumulation of amino acid replacement mutations in complementarity determining regions. These observations suggest the limited B-cell response found in this acute MS brain was antigen driven.     

Binding of immunoglobulin G antibodies in Guillain-Barré syndrome sera to a mixture of GM1 and a phospholipid: possible clinical implications

Anti-GM1 immunoglobulin G (IgG) antibodies are frequently present in sera from patients with Guillain-Barré syndrome (GBS). A previous report on a patient who had a neuropathy with immunoglobulin M (IgM) M-protein binding to a conformational epitope formed by phosphatidic acid (PA) and gangliosides prompted us to investigate the binding of IgG antibodies in GBS sera to a mixture of GM1 and PA (GM1/PA). Of 121 GBS patients, 32 had anti-GM1 IgG antibodies. All 32 also had antibody activity against GM1/PA. Twenty-five (78%) of 32 patients had greater activity against GM1/PA than against GM1 alone. Twelve patients who had no anti-GM1 IgG antibodies had IgG antibody activity against GM1/PA. No GBS patient had IgG antibody against PA alone. In contrast, two rabbit anti-GM1 antisera had greater activity against GM1 alone than against GM1/PA. IgG antibody with greater binding activity against a mixture of GM1 and a phospholipid than against GM1 alone may have an important role in the pathogenesis of GBS and has implications for diagnosis.     

Anti-GM1 antibodies in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) treated with intravenous immunoglobulin (IVIg)

Patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and with a chronic polyneuropathy (non-CIDP) were studied for the presence of anti-GM1 antibodies. In pretreatment sera of CIDP patients, we found IgG anti-GM1 antibodies in 23%, IgM in 7%, and IgA in 14%. Predominantly motor involvement was associated with IgG and IgM anti-GM1 antibodies in CIDP patients (P = 0.002). Improvement after intravenous immunoglobulin (IVIg) therapy was not associated with anti-GM1 antibody titer before or after treatment. Anti-GM1 antibody titers before onset of treatment was not related to poor clinical outcome, although large clinical improvements after IVIg therapy were observed less often (P = 0.057) in patients with high titer anti-GM1 antibodies before treatment.     

Serum anti-GM2 and anti-GalNAc-GD1a ganglioside IgG antibodies are biomarkers for immune-mediated polyneuropathies in cats

Recent work identified anti-GM2 and anti-GalNAc-GD1a IgG ganglioside antibodies as biomarkers in dogs clinically diagnosed with acute canine polyradiculoneuritis, in turn considered a canine equivalent of Guillain-Barré syndrome. This study aims to investigate the serum prevalence of similar antibodies in cats clinically diagnosed with immune-mediated polyneuropathies. The sera from 41 cats clinically diagnosed with immune-mediated polyneuropathies (IPN), 9 cats with other neurological or neuromuscular disorders (ONM) and 46 neurologically normal cats (CTRL) were examined for the presence of IgG antibodies against glycolipids GM1, GM2, GD1a, GD1b, GalNAc-GD1a, GA1, SGPG, LM1, galactocerebroside and sulphatide. A total of 29/41 IPN-cats had either anti-GM2 or anti-GalNAc-GD1a IgG antibodies, with 24/29 cats having both. Direct comparison of anti-GM2 (sensitivity: 70.7%; specificity: 78.2%) and anti-GalNAc-GD1a (sensitivity: 70.7%; specificity: 70.9%) antibodies narrowly showed anti-GM2 IgG antibodies to be the better marker for identifying IPN-cats when compared to the combined ONM and CTRL groups (P = .049). Anti-GA1 and/or anti-sulphatide IgG antibodies were ubiquitously present across all sample groups, whereas antibodies against GM1, GD1a, GD1b, SGPG, LM1 and galactocerebroside were overall only rarely observed. Anti-GM2 and anti-GalNAc-GD1a IgG antibodies may serve as serum biomarkers for immune-mediated polyneuropathies in cats, as previously observed in dogs and humans.     

IgG anti-GM1 antibodies from patients with acute motor neuropathy are predominantly of the IgG1 and IgG3 subclasses

Increased titers of IgG anti-GM1 and anti-asialo GM1 (GA1) ganglioside antibodies are present in some patients with the Guillain-Barré syndrome, particularly with the motor axonal variant, and following infection with Campylobacter jejuni or parenteral administration of gangliosides. The subclass distribution of IgG anti-GM1 or GA1 antibodies from 19 patients with acute motor neuropathy and elevated antibody titers were measured by ELISA using mouse monoclonal antibodies specific for human IgG subclasses. The anti-GM1 or GA1 antibodies were predominantly of the IgG1 and IgG3 subclasses, which are capable of complement fixation, and are characteristic of a T cell-dependent antibody response.