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TC06.02 - Presentation 02 (ID 605)
Abstract
Abstract
Antigen recognition and pathomechanisms of MOG-Abs
Myelin oligodendrocyte glycoprotein (MOG) is a membrane-anchored protein displayed on the outer surface of internodal myelin. This localization makes MOG principally accessible to auto-antibodies. Autoantibodies to MOG are detected in a proportion of patients with inflammatory disorders of the CNS. In this lecture, assays to detect MOG-Abs will be presented and methods to identify epitopes on MOG will be introduced. Strategies to explore possible pathogenic activities of MOG-Abs using in vitro and in vivo models will be outlined. Using affinity-purified MOG-Abs from selected patients and an intrathecal injection in a rat model of experimental autoimmune encephalitis pathogenic mechanisms could identified: MOG-Abs from patients synergize with T cells. MOG-Abs may mediate demyelination, if the blood-brain barrier is breached by T cells and may enhance local activation of cognate MOG-specific T cells.
TC06.03 - Presentation 03 (ID 606)
Abstract
Abstract
The myelin oligodendrocyte glycoprotein (MOG) is a protein expressed in the outermost surface of the myelin sheath of the central nervous system. Its localization makes it a target for autoantibodies. Over the last few years, serum autoantibodies recognizing MOG (MOG-IgG) have been associated to optic neuritis, myelitis, acute disseminated encephalomyelitis, cortical encephalitis, and some cases of aquaporin-4 (AQP4-IgG) negative neuromyelitis optica spectrum disorder (NMOSD). Pediatric cases represent a significant proportion of MOG-IgG+ patients; MOG-IgG+ cases may be even more frequent than AQP4-IgG+ NMOSD at this age group. Several groups have published case reports and observational studies reporting clinical features and treatments regimes used in clinical practice. Nevertheless, given the recent recognition of this condition, there is still no randomized controlled trial on acute phase and long-term treatments. Most of the MOG-IgG+ patients receive high- or low-dose corticosteroids in the acute phase, demonstrating a better response compared to AQP4-IgG+ NMOSD. Other treatments for acute phase are intravenous human immunoglobulin and plasma exchange. Some of the MOG-IgG+ patients may have a monophasic disease and become MOG-IgG negative after 6 months to 2 years, so it is controversial to start long-term attack-prevention treatments after the first MOG-IgG demyelinating episode. Strategies like long-term oral corticosteroids and/or azathioprine may not have a clear benefit of these approaches and expose patients to the risks of complications due to prolonged corticosteroid use or immunosuppression. On the other hand, long-term treatment is usually indicated for relapsing cases, especially in those with persistent MOG-IgG titers. Some MOG-IgG+ patients have been misdiagnosed and exposed to disease-modifying treatments for multiple sclerosis (MS). Few anecdotal reports indicated that these patients experienced more relapses under interferon-beta but it is unclear if other drugs may increase the number and/or promote severe relapses as previously observed in AQP4-IgG+ NMOSD. In clinical practice, common long-term attack-prevention treatments for MOG-IgG+ patients are immunosuppressive drugs such as azathioprine, mycophenolate mofetil and cyclophosphamide or B-cell depleting therapies like rituximab; however, the clinical response seems to be different from AQP4-IgG+ NMOSD. A recent cohort study of relapsing MOG-IgG+ pediatric patients showed efficacy of repeated intravenous human immunoglobulin in reducing the number of relapses compared to immunosuppressive treatments.