Abstract Details

Title Aquaporin-1 Autoantibodies in Patients with Neuromyelitis Optica Spectrum Disorders

Topic MS and Related Diseases

Presentation(s) S60 - (-)

Poster/Presentation
Number 004

Objective

Background NMOsd group includes neuromyelitis optica (NMO), with major characteristics longitudinally extensive transverse myelitis (LETM) and optic neuritis, only LETM, only recurrent optic neuritis and related disorders. Autoantibodies against AQP4 (a water channel in CNS astrocytes) are detected in [sim]50-80% of all patients with NMOsd. These antibodies present an invaluable biomarker for NMOsd and for the differential diagnosis of multiple sclerosis (MS). However, diagnosis of anti-AQP4-seronegative NMOsd remains challenging. Human astrocytes also express aquaporin-1 (AQP1), suggesting AQP1 might be an autoantigen in anti-AQP4-antibody negative NMOsd.

Design/Methods Anti-AQP1 autoantibodies cannot be detected by the classical NMO-IgG assay. We therefore developed a radioimmunoprecipitation assay (confirmed by competition and protein immunoblotting experiments), and searched for anti-AQP1 and anti-AQP4 antibodies in sera from 348 patients suspected for NMOsd, 40 MS patients, 142 patients with non-demyelinating neuroimmune diseases, and 100 healthy individuals.

Results Anti-AQP1 autoantibodies were detected in 16.7% of the patients with suspected NMOsd, whereas 12% had anti-AQP4 autoantibodies; about 4% were double-positive. Most anti-AQP1 autoantibodies were of the complement-activating IgG1 subclass. Anti-AQP1 antibodies were not detected in 242 healthy individuals or patients with non-demyelinated neuroimmune diseases, but were detected in 3/40 patients diagnosed with MS. Retrospective analysis of 15 anti-AQP1+/anti-AQP4- patients showed that 12 had longitudinally extensive transverse myelitis (LETM, a form of NMOsd), 3 of which also had optic neuritis (i.e. NMO). 1/15 had transverse myelitis and 2/15 were diagnosed with MS but with predominant spinal cord lesions.

Conclusions Anti-AQP1 autoantibodies are present in a subgroup of patients with chronic demyelination in the CNS with similarities and differences to anti-AQP4-positive NMOsd patients, offering a novel biomarker for CNS demyelination disorders.

Authors/Disclosures
John Tzartos, MD (Aiginiteio University Hospital of Athens) PRESENTER	No disclosure on file
	No disclosure on file
Konstantinos Kilintirea, MD (Aiginitio Hospital of Athens)	No disclosure on file
	No disclosure on file
Thomas Thomaidis, MD (Red Cross Hospital)	No disclosure on file
	No disclosure on file
	No disclosure on file

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