Pathogenic potential of anti-ganglioside antibodies in a murine model of axonal Guillain-Barré syndrome

Guillian-Barré Syndrome (GBS) is the world’s leading cause of neuromuscular paralysis occurring in serologically and pathogenically distinct forms. GBS is believed to have an autoimmune basis, where antibodies raised during antecedent infections (eg Campylobacter jejuni) cross-react with self antigens, exemplifying the process of molecular mimicry. These self-antigens are gangliosides, which are glycolipid structures enriched in peripheral nerve in specific membrane compartments termed lipid rafts. To date, successful murine models of anti-GD1a and anti-Gq1b ganglioside mediated neuropathy exist. Clinical evidence supports the involvement of anti-GM1 antibodies in nerve injury, however generation of anti-GM1 antibody mediated neuropathy models remain an enigma, and to date, the only successful model is based in Japanese rabbits. This thesis aims to address the controversies surrounding anti-GM1 antibody mediated neuropathy by utilising a panel of anti-GM1 antibodies of differing specificity, and explores how the stereometric interactions of GM1 with lipid raft species underpin the pathogenic potential of these antibodies

Harnessing In Vivo Imaging to Investigate Immune-mediated Disorders of the Neuromuscular Junction

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Harnessing In Vivo Imaging to Investigate Immune-mediated Disorders of the Neuromuscular Junction

No abstract available

Rapid Deterioration and Steady Recovery of the Motor Nerve Terminal Integrity Following Complemenet-mediated Injury in a Murine Model of Guillain-Barré Syndrome

No abstract available

Rapid Deterioration and Steady Recovery of the Motor Nerve Terminal Integrity Following Complemenet-mediated Injury in a Murine Model of Guillain-Barré Syndrome

No abstract available

Neuropathophysiological potential of Guillain-Barré syndrome anti-ganglioside-complex antibodies at mouse motor nerve terminals

Objectives: Anti-ganglioside antibodies are present in approximately half of Guillain-Barré syndrome (GBS) patients. Recently, it has been shown that a considerable proportion of these patients has serum antibodies against antigenic epitopes formed by a complex of two different gangliosides. However, direct experimental evidence for neuropathogenicity of this special category of antibodies is currently lacking. Here, we explored a series of GBS and GBS-variant sera with anti-ganglioside-complex antibodies for their ability to induce complement-dependent deleterious effects at the living neuronal membrane. Methods: The neuropathophysiological potential of 31 GBS sera containing either anti-GM1/GD1a- or anti-GM1/GQ1b-ganglioside-complex antibodies was studied at motor nerve terminal presynaptic membranes in the mouse phrenic nerve/diaphragm muscle ex vivo experimental model. With electrophysiological measurements and confocal fluorescence microscopy, we assessed and quantified the damaging effect on neuronal membranes by anti-ganglioside-complex antibodies. Results: We show that anti-GM1/GD1a- and anti-GM1/GQ1b-ganglioside-complex positive sera can induce complement-mediated functional and morphological injury at mouse motor nerve terminals ex vivo. Of the 31 investigated anti-ganglioside-complex patient sera, 17 sera induced increases in miniature end-plate potential frequency in this experimental model, mostly associated with muscle fibre twitches. Variability in potency was observed, with the anti-GM1/GD1a-complex sera inducing the most outspoken effects. Conclusions: The present study shows the presence of ganglioside-complexes as available antigens in living neuronal membranes and supplies proof-of-principle that anti-ganglioside-complex antibodies in sera from GBS patients can induce complement-mediated damage. This strongly supports the hypothesis that autoimmune targeting of ganglioside-complexes is of pathogenic relevance in a proportion of GBS patients

Anti-ganglioside antibody internalization attenuates motor nerve terminal injury in a mouse model of acute motor axonal neuropathy

In the Guillain-Barré syndrome subform acute motor axonal neuropathy (AMAN), Campylobacter jejuni enteritis triggers the production of anti-ganglioside Abs (AGAbs), leading to immune-mediated injury of distal motor nerves. An important question has been whether injury to the presynaptic neuron at the neuromuscular junction is a major factor in AMAN. Although disease modeling in mice exposed to AGAbs indicates that complement-mediated necrosis occurs extensively in the presynaptic axons, evidence in humans is more limited, in comparison to the extensive injury seen at nodes of Ranvier. We considered that rapid AGAb uptake at the motor nerve terminal membrane might attenuate complement-mediated injury. We found that PC12 rat neuronal cells rapidly internalized AGAb, which were trafficked to recycling endosomes and lysosomes. Consequently, complement-mediated cytotoxicity was attenuated. Importantly, we observed the same AGAb endocytosis and protection from cytotoxicity in live mouse nerve terminals. AGAb uptake was attenuated following membrane cholesterol depletion in vitro and ex vivo, indicating that this process may be dependent upon cholesterol-enriched microdomains. In contrast, we observed minimal AGAb uptake at nodes of Ranvier, and this structure thus remained vulnerable to complement-mediated injury. These results indicate that differential endocytic processing of AGAbs by different neuronal and glial membranes might be an important modulator of site-specific injury in acute AGAb-mediated Guillain-Barré syndrome subforms and their chronic counterparts

The neuropathic potential of anti-GM1 autoantibodies is regulated by the local glycolipid environment in mice

Anti-GM1 ganglioside autoantibodies are used as diagnostic markers for motor axonal peripheral neuropathies and are believed to be the primary mediators of such diseases. However, their ability to bind and exert pathogenic effects at neuronal membranes is highly inconsistent. Using human and mouse monoclonal anti-GM1 antibodies to probe the GM1-rich motor nerve terminal membrane in mice, we here show that the antigenic oligosaccharide of GM1 in the live plasma membrane is cryptic, hidden on surface domains that become buried for a proportion of anti-GM1 antibodies due to a masking effect of neighboring gangliosides. The cryptic GM1 binding domain was exposed by sialidase treatment that liberated sialic acid from masking gangliosides including GD1a or by disruption of the live membrane by freezing or fixation. This cryptic behavior was also recapitulated in solid-phase immunoassays. These data show that certain anti-GM1 antibodies exert potent complement activation-mediated neuropathogenic effects, including morphological damage at living terminal motor axons, leading to a block of synaptic transmission. This occurred only when GM1 was topologically available for antibody binding, but not when GM1 was cryptic. This revised understanding of the complexities in ganglioside membrane topology provides a mechanistic account for wide variations in the neuropathic potential of anti-GM1 antibodies

Sulfatide binding properties of murine and human antiganglioside antibodies

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