Since MOG-associated demyelinating disease is likely different from AQP4-IgG disease in terms of underlying disease mechanisms, relapse risk and possibly treatment, testing for MOG-IgG in patients with AQP4-IgG-negative NMOSD and other non-MS demyelination may have significant implications to management and clinical trials.
We conclude that the processing of AQP4 by antigen presenting cells in Lewis rats produces a highly encephalitogenic AQP4 epitope (AQP4268-285), that T cells specific for this epitope are found in the immune repertoire of normal Lewis rats and can be readily expanded, and that AQP4268-285-specific T cells produce NMO-like lesions in the presence of NMO-IgG.
Within the CNS autoimmunity control cohort, autoantibodies against aquaporin 4 and high-titer Abs against myelin oligodendrocyte glycoprotein were, as expected, specific for neuromyelitis optica spectrum disorders.
The NMO patients with AQP4 (-) showed higher prevalence of BL, ITL, and similar spinal cord lesion length, compared to AQP4 (+), and demonstrated deep grey matter atrophy, suggesting an intermediate phenotype between that of typical MS and NMO.
Longitudinally extensive transverse myelitis (LETM) accompanying systemic lupus erythematosus (SLE) is often due to coexisting aquaporin-4-IgG seropositive neuromyelitis optica spectrum disorder but has not been associated with myelin oligodendrocyte glycoprotein-IgG (MOG-IgG).
Mice, pretreated with bacterial proteins, received daily intraperitoneal injections of IgG purified from AQP4-IgG-seropositive NMOSD patients [IgG<sub>(AQP4+)</sub>], or IgG from AQP4-IgG-seronegative patients [IgG<sub>(AQP4-)</sub>] or healthy subjects [IgG<sub>(Healthy)</sub>] for 8 days.
Neuropathological assessments showed neuronal loss in cortical layers II, III, and IV, with nonlytic reaction of aquaporin-4 (AQP4)-negative astrocytes in layer I, massive activated microglia in layer II, and meningeal inflammation in NMOsd brains.
We conducted a retrospective study of hospital case records of 294 individuals diagnosed with neuromyelitis optica (NMO) (G36.0 ICD-10, 341.0 ICD-9) in the Swedish National Patient Register from 1987 to end of 2013 or detected by the presence of aquaporin-4 (AQP4) immunoglobulin G (IgG) in serum during the study period.
There is a consensus that the anti-aquaporin-4 antibody (AQP4-IgG) is the main pathogen detectable in majority of NMOSD patients, including traditional NMO and AQP4-IgG-positive optic neuritis.
The Lewis rat model of NMO uses a myelin-reactive experimental autoimmune encephalomyelitis (EAE) background with passive transfer of pooled human antibody from patients with aquaporin-4 (AQP4) seropositive NMO at onset of EAE symptoms.
Using cell-based assays with recombinant full-length, conformationally intact MOG, several recent studies have revealed that MOG Abs can be found in a subset of predominantly pediatric patients with acute disseminated encephalomyelitis (ADEM), aquaporin-4 (AQP4) seronegative neuromyelitis optica spectrum disorders (NMOSD), monophasic or recurrent isolated optic neuritis (ON), or transverse myelitis, in atypical MS and in <i>N</i>-methyl-d-aspartate receptor-encephalitis with overlapping demyelinating syndromes.
MOG-IgG was absent in 221 further controls, including 83 patients with AQP4-IgG-seropositive neuromyelitis optica spectrum disorders and 85 with multiple sclerosis (MS).
MRI indicated LESCLs more frequently affected PC and LC than AC in anti-AQP4 antibody-seropositive NMO/NMOSD (86.7%, 60.0% and 20.0%, P<sup>corr</sup> = 0.005, and P<sup>corr</sup> = 0.043, respectively) and AQP4 antibody-seronegative MS patients (86.7%, 73.3% and 33.3%, P<sup>corr</sup> = 0.063, and P<sup>corr</sup> = 0.043, respectively).
Serum antibodies to MOG (MOG-IgG) have recently been found to be a biomarker of MOG-IgG-associated disorder (MOGAD), a demyelinating disease distinct from both multiple sclerosis and aquaporin-4-IgG neuromyelitis optica spectrum disorder (AQP4-IgG-positive NMOSD).
Although complement-dependent astrocyte damage mediated by anti-aquaporin 4 autoantibody (AQP4-Ab) is well acknowledged to be the core of NMOSD pathogenesis, additional inflammatory cascades may contribute to the establishment of lesion formation.
The demographic, clinical, neuroimaging, and anti-AQP-4 antibody status were investigated in four patients from two Asian families with anti-AQP-4 antibody-positive NMO.
Microcystic macular edema (MME) was observed only in eyes of MOG-abs-positive (24%) and AQP4-abs-positive NMOSD (5.6%), but not in MOG-abs-negative MS or HC (p < 0.01).