Dataset Information

Antibody to aquaporin 4 in the diagnosis of neuromyelitis optica.

ABSTRACT:

Background

Neuromyelitis optica (NMO) is a demyelinating disease of the central nervous system (CNS) of putative autoimmune aetiology. Early discrimination between multiple sclerosis (MS) and NMO is important, as optimum treatment for both diseases may differ considerably. Recently, using indirect immunofluorescence analysis, a new serum autoantibody (NMO-IgG) has been detected in NMO patients. The binding sites of this autoantibody were reported to colocalize with aquaporin 4 (AQP4) water channels. Thus we hypothesized that AQP4 antibodies in fact characterize NMO patients.

Methods and findings

Based on these observations we cloned human water channel AQP4, expressed the protein in a eukaryotic transcription/translation system, and employed the recombinant AQP4 to establish a new radioimmunoprecipitation assay (RIPA). Indeed, application of this RIPA showed that antibodies against AQP4 exist in the majority of patients with NMO (n = 37; 21 positive) as well as in patients with isolated longitudinally extensive transverse myelitis (n = 6; six positive), corresponding to a sensitivity of 62.8% and a specificity of 98.3%. By contrast, AQP4 antibodies were virtually absent in 291 other participants, which included patients with MS (n = 144; four positive), patients with other inflammatory and noninflammatory neurological diseases (n = 73; one positive), patients with systemic autoimmune diseases (n = 45; 0 positive), and healthy participants (n = 29; 0 positive).

Conclusions

In the largest series reported so far to our knowledge, we quantified AQP4 antibodies in patients with NMO versus various other diseases, and showed that the aquaporin 4 water channel is a target antigen in a majority of patients with NMO. The newly developed assay represents a highly specific, observer-independent, and easily reproducible detection method facilitating clinically relevant discrimination between NMO, MS, and other inflammatory diseases.

SUBMITTER: Paul F

PROVIDER: S-EPMC1852124 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:BackgroundRecognizing the predictors of disease relapses in patients with anti-aquaporin-4 antibody (AQP4-ab)-positive neuromyelitis optica spectrum disorder (NMOSD) is essential for individualized treatment strategy. We aimed to identify the factors that predicted relapses among patients with AQP4-ab-positive NMOSD, develop outcome prediction models, and validate them in a multicenter validation cohort.MethodsBetween January 2015 and December 2020, 820 patients with NMOSD were registered at Huashan Hospital. We retrospectively reviewed their medical records, and included 358 AQP4-ab-positive patients with 1135 treatment episodes. Univariate and multivariate analyses were used to explore the predictors of relapse, severe visual or motor disability during follow-up. A model predicting the 1- and 2-year relapse-free probability was developed and validated in an external validation cohort of 92 patients with 213 treatment episodes.ResultsLower serum AQP4-ab titer (< 1:100), higher Expanded Disability Status Scale (EDSS) score at onset (≥ 2.5), and use of intravenous methylprednisolone (IVMP) at the first attack predicted an overall lower annualized relapse rate. Older age (> 48 years), optic neuritis at onset, and higher onset EDSS score (≥ 2.5) significantly increased the risk for blindness, while IVMP at the first attack and maintenance therapy reduced the risk for blindness. Myelitis at onset increased the possibility of motor disability (EDSS ≥ 6.0), severe motor disability or death (EDSS ≥ 8.0), while maintenance therapy reduced these possibilities. Anderson and Gill model identified that the risk factors predicting recurrent relapses under certain treatment status were female gender, high AQP4-ab titer (≥ 1:100), previous attack under same therapy, lower EDSS score at treatment initiation (< 2.5), and no maintenance therapy or oral prednisone lasting less than 6 months. A nomogram using the above factors showed good discrimination and calibration abilities. The concordance indexes in the primary and validation cohort were 0.66 and 0.65, respectively.ConclusionThis study reports the demographic, clinical and therapeutic predictors of relapse, and severe visual or motor disability in NMOSD. Early identification of patients at risk of unfavorable outcomes is of paramount importance to inform treatment decisions.

Project description:Objective Neuromyelitis optica and its spectrum disorders (NMOSD) are inflammatory demyelinating diseases (IDD) with a specific biomarker, aquaporin-4-IgG. Prior NMO/NMOSD epidemiological studies are limited by lack of aquaporin-4-IgG seroprevalence assessment, absence of population-based USA studies and under-representation of blacks. To overcome these limitations, we sought to compare NMO/NMOSD seroepidemiology across two ethnically divergent populations. Methods We performed a population-based comparative study of the incidence (2003-2011) and prevalence (on December 31, 2011) of NMO/NMOSD and aquaporin-4-IgG seroincidence and seroprevalence (sera collected in 80-84% of IDD) among patients with IDD diagnosis in Olmsted County, USA (82% white [Caucasian]) and Martinique (90% black [Afro-Caribbean]). Aquaporin-4-IgG was measured by M1-isoform-fluorescent-activated-cell-sorting assays. Results The age and sex adjusted incidence (7.3 vs 0.7/1,000,000 person-years [p<0.01]) and prevalence (10 vs 3.9/100,000[p=0.01]) in Martinique exceeded that in Olmsted County. The AQP4-IgG age and sex-adjusted seroincidence (6.5 vs 0.7/1,000,000 person-years [p<0.01]) and seroprevalence (7.9 vs 3.3/100,000[p=0.04]) were also higher in Martinique than Olmsted County. The ethnicity-specific prevalence was similar in Martinique and Olmsted County: 11.5 and 13/100,000 in blacks, and 6.1 and 4.0/100,000 in whites, respectively. NMO/NMOSD represented a higher proportion of IDD in Martinique than Olmsted County (16% vs 1.4%; p<0.01). The onset age (median, 35-37 years) and female:male distribution (8-9:1) were similar across both populations; 60% of prevalent cases were either blind in one eye, dependent on a gait aid or both. Interpretation This study reports the highest prevalence of NMO/NMOSD in any population (10/100,000 in Martinique), estimates it affects 16,000-17,000 in the USA (higher than previous predictions) and demonstrates it disproportionately affects blacks. This article is protected by copyright. All rights reserved.

Project description:ObjectiveWe previously identified the independent predictors of recurrent relapse in neuromyelitis optica spectrum disorder (NMOSD) with anti-aquaporin-4 antibody (AQP4-ab) and designed a nomogram to estimate the 1- and 2-year relapse-free probability, using the Cox proportional hazard (Cox-PH) model, assuming that the risk of relapse had a linear correlation with clinical variables. However, whether the linear assumption fits real disease tragedy is unknown. We aimed to employ deep learning and machine learning to develop a novel prediction model of relapse in patients with NMOSD and compare the performance with the conventional Cox-PH model.MethodsThis retrospective cohort study included patients with NMOSD with AQP4-ab in 10 study centers. In this study, 1,135 treatment episodes from 358 patients in Huashan Hospital were employed as the training set while 213 treatment episodes from 92 patients in nine other research centers as the validation set. We compared five models with added variables of gender, AQP4-ab titer, previous attack under the same therapy, EDSS score at treatment initiation, maintenance therapy, age at treatment initiation, disease duration, the phenotype of the most recent attack, and annualized relapse rate (ARR) of the most recent year by concordance index (C-index): conventional Cox-PH, random survival forest (RSF), LogisticHazard, DeepHit, and DeepSurv.ResultsWhen including all variables, RSF outperformed the C-index in the training set (0.739), followed by DeepHit (0.737), LogisticHazard (0.722), DeepSurv (0.698), and Cox-PH (0.679) models. As for the validation set, the C-index of LogisticHazard outperformed the other models (0.718), followed by DeepHit (0.704), DeepSurv (0.698), RSF (0.685), and Cox-PH (0.651) models. Maintenance therapy was calculated to be the most important variable for relapse prediction.ConclusionThis study confirmed the superiority of deep learning to design a prediction model of relapse in patients with AQP4-ab-positive NMOSD, with the LogisticHazard model showing the best predictive power in validation.

Project description:Neuromyelitis optica (NMO) is an inflammatory disease caused by the aquaporin (AQP)-4-antibody. Pathological studies on NMO have revealed extensive astrocytic damage, as evidenced by the loss of AQP4 and glial fibrillary acidic protein (GFAP), specifically in perivascular regions with immunoglobulin and complement depositions, although other pathological patterns, such as a loss of AQP4 without astrocyte destruction and clasmatodendrosis, have also been observed. Previous studies have shown that complement-dependent antibody-mediated astrocyte lysis is likely a major pathomechanism in NMO. However, there are also data to suggest antibody-mediated astrocyte dysfunction in the absence of complement. Thus, the importance of complement inhibitory proteins in complement-dependent AQP4-antibody-mediated astrocyte lysis in NMO is unclear. In most of the previous studies, the complement and target cells (astrocytes or AQP4-transfected cells) were derived from different species; however, the complement inhibitory proteins that are expressed on the cell surface cannot protect themselves against complement-dependent cytolysis unless the complements and complement inhibitory proteins are from the same species. To resolve these issues, we studied human astrocytes in primary culture treated with AQP4-antibody in the presence or absence of human complement and examined the effect of complement inhibitory proteins using small interfering RNA (siRNA).Purified IgG (10 mg/mL) was obtained from 5 patients with AQP4-antibody-positive NMO, 3 patients with multiple sclerosis (MS), and 3 healthy controls. Confluent human astrocytes transfected with Venus-M1-AQP4-cDNA were incubated with IgG (5% volume). After washing, we cultured the cells with human complements with or without heat inactivation. We observed time-lapse morphological and immunohistochemical changes using a fluorescence microscope. We also evaluated cytotoxicity using a propidium iodide (PI) kit and the lactate dehydrogenase (LDH) assay.AQP4-antibody alone caused clustering and degradation followed by endocytosis of membraneous AQP4, thereby resulting in decreased cellular adherence and the shrinkage of astrocytic processes. However, these changes were partially reversed by the removal of IgG in culture. In contrast, following the application of AQP4-antibody and non-heated human complements, the cell bodies and nuclei started to swell. At 3 h, most of the astrocytes had lost mobility and adherence and were eventually destroyed or had swollen and were then destroyed. In addition, the remaining adherent cells were mostly PI-positive, indicating necrosis. Astrocyte lysis caused by rabbit complement occurred much faster than did cell lysis with human complement. However, the cell lysis was significantly enhanced by the transfection of astrocytes with siRNA against human CD55 and CD59, which are major complement inhibitory proteins on the astrocyte membrane. AQP4-antibody-negative IgG in MS or control did not induce such changes.Taken together, these findings suggest that both complement-dependent and complement-independent AQP4-antibody-mediated astrocytopathies may operate in NMO, potentially contributing to diverse pathological patterns. Our results also suggest that the effect of complement inhibitory proteins should be considered when evaluating AQP4-antibody-mediated cytotoxicity in AQP4-expressing cells.