The Diagnostic Utility of Determining Anti-GM1: GalC Complex Antibodies in Multifocal Motor Neuropathy: A Validation Study.

BACKGROUND: Multifocal motor neuropathy (MMN) is associated with IgM antibodies to GM1 ganglioside. The importance of the lipid milieu that might facilitate or inhibit antibody binding to GM1 in immunoassays is well recognised. Existing studies, using a range of different approaches, generally concur that anti-GM1 IgM antibody detection rates are improved by the addition of galactocerebroside (GalC) to the GM1 assay. OBJECTIVE: The current study sought to formally evaluate the clinical utility of the GM1:GalC complex assay in the diagnosis of MMN. METHODS: Anti-GM1 and -GM1:GalC antibodies were examined using ELISA and glycoarray (dot blot) in a fully blinded study design, consisting of 100 MMN patients, 100 ALS cases and 100 healthy controls. RESULTS: The detection of anti-GM1 Abs using glycoarray was 67% sensitive and 85% specific. The addition of GalC to GM1, (1:1 weight to weight ratio), increased the sensitivity to 81% , whilst dropping specificity to 80% . Increasing the GalC content to a 1:5 ratio (or higher) further decreased specificity, and in doing so limited the usefulness of the GM1:GalC assay to the level of GM1 alone. The addition of GalC to the ELISA method also significantly increased sensitivity compared with GM1 alone, albeit with a significant decrease in specificity. CONCLUSIONS: This study indicates that the GM1:GalC assay is an advantageous assay adaptation for detecting anti-GM1 antibodies in MMN, using either glycoarray or ELISA, and warrants introduction into clinical diagnostic practice.

Improving the detection of IgM antibodies against glycolipids complexes of GM1 and Galactocerebroside in Multifocal Motor Neuropathy using glycoarray and ELISA assays.

Antibodies against complexes of GM1:GalC are detected in multifocal motor neuropathy. Previous studies used different techniques, explaining disparities in the results. Antibodies against GM1 and GM1:GalC with different proportions of GalC were measured with both glycoarray and ELISA in 20 multifocal motor neuropathies, and 45 controls. The 1:5 ratio and the 1:1 ratio of GM1:GalC (weight ratio) were respectively the most effective for glycoarray and for ELISA. Testing for anti-GM1:GalC antibodies increased the sensitivity from 40% with anti-GM1 antibodies to 65% with array and 60% with ELISA without loss in specificity (above 91%). Anti-GM1:GalC antibodies are effective biological tools to diagnose multifocal motor neuropathy.

The application of glycosphingolipid arrays to autoantibody detection in neuroimmunological disorders.

Humans with autoimmune peripheral neuropathies frequently harbour serum antibodies to single glycosphingolipids, especially gangliosides. Recently it has been appreciated that glycolipid and lipid complexes, formed from two or more individual species, can interact to create molecular shapes capable of being recognised by these autoantibodies whilst not binding to the single individuals. As a result of this, novel autoantibody targets have been identified. This newly termed 'combinatorial glycomic' approach has provided the impetus to redesigning the assay methodologies traditionally used in the neuropathy-associated autoantibody field. Combinatorial glycoarrays can be readily constructed in house using lipids of interest. Herein we especially highlight the role of the neutral lipids cholesterol and galactocerebroside in modifying glycosphingolipid orientation that subsequently favours or inhibits autoantibody binding.

Anti-GQ1b ganglioside positive Miller Fisher syndrome - evidence of paranodal pathology on nerve biopsy.

BACKGROUND: Miller Fisher syndrome is a regional variant of Guillain-Barre syndrome with a characteristic clinical triad of ophthalmoplegia, areflexia and ataxia and occasionally distal limb sensory loss. 90% of patients have associated antibodies to the GQ1b ganglioside. The pathophysiology of antibody-mediated peripheral nerve impairment remains uncertain. This report includes the first description of a peripheral sensory nerve biopsy in Miller Fisher syndrome. RESULTS: A single case report is described of a 46 year old woman who presented with 2 weeks of distal glove and stocking sensory loss to both deep and superficial sensory modalities, areflexia and weight loss. This was followed by rapid onset of ataxia, ophthalmoplegia, and bulbar impairment. Peripheral neurophysiology showed reduced sensory nerve amplitudes with preserved conduction velocities in keeping with an axonal pattern of impairment. Clinical concerns of a systemic inflammatory disorder led to a diagnostic peripheral nerve biopsy from the sensory branch of the radial nerve. However she subsequently made a complete recovery over 5 weeks. Combinatorial glycoarrays confirmed restricted serum binding for GQ1b in acute serum which later resolved in a convalescent sample. The nerve biopsy showed lengthening of nodes of Ranvier, myelin splitting and macrophage internodal axonal invasion without any features of demyelination. CONCLUSIONS: The pathological features were strikingly similar to those found in acute motor axonal neuropathy and indicate the region of the node of Ranvier to be a primary focus of GQ1b induced damage in Miller Fisher syndrome, at least in this particular overlap syndrome with prominent sensory nerve involvement.

Anti-GM2 ganglioside antibodies are a biomarker for acute canine polyradiculoneuritis.

Acute canine polyradiculoneuritis (ACP) is considered to be the canine equivalent of the human peripheral nerve disorder Guillain-Barré syndrome (GBS); an aetiological relationship, however, remains to be demonstrated. In GBS, anti-glycolipid antibodies (Abs) are considered as important disease mediators. To address the possibility of common Ab biomarkers, the sera of 25 ACP dogs, 19 non-neurological, and 15 epileptic control dogs were screened for IgG Abs to 10 glycolipids and their 1 : 1 heteromeric complexes using combinatorial glycoarrays. Anti-GM2 ganglioside Abs were detected in 14/25 ACP dogs, and anti-GA1 Abs in one further dog. All controls except for one were negative for anti-glycolipid Abs. In this cohort of cases and controls, the glycoarray screen reached a diagnostic sensitivity of 60% and a specificity of 97%; a lower sensitivity (32%) was reported using a conventional glycolipid ELISA. To address the possible pathogenic role for anti-GM2 Abs in ACP, we identified GM2 in canine sciatic nerve by both mass spectrometry and thin layer chromatography overlay. In immunohistological studies, GM2 was localized predominantly to the abaxonal Schwann cell membrane. The presence of anti-GM2 Abs in ACP suggests that it may share a similar pathophysiology with GBS, for which it could thus be considered a naturally occurring animal model.

Lipid arrays identify myelin-derived lipids and lipid complexes as prominent targets for oligoclonal band antibodies in multiple sclerosis.

The presence of oligoclonal bands of IgG (OCB) in cerebrospinal fluid (CSF) is used to establish a diagnosis of multiple sclerosis (MS), but their specificity has remained an enigma since its first description over forty years ago. We now report that the use of lipid arrays identifies heteromeric complexes of myelin derived lipids as a prominent target for this intrathecal B cell response.