An immunoassay that distinguishes real neuromyelitis optica signals from a labeling detected in patients receiving natalizumab

Evaluation of aquaporins in the cerebrospinal fluid in patients with idiopathic normal pressure hydrocephalus

Brain aquaporin 1 (AQP1) and AQP4 are involved in cerebrospinal fluid (CSF) homeostasis and might participate in the origin of hydrocephalus. Studies have shown alterations of perivascular AQP4 expression in idiopathic normal pressure hydrocephalus (iNPH) and Alzheimer's disease (AD). Due to the overlapping of clinical signs between iNPH and certain neurological conditions, mainly AD, specific biomarkers might improve the diagnostic accuracy for iNPH. The goal of the present study was to analyze and quantify the presence of AQP1 and AQP4 in the CSF of patients with iNPH and AD to determine whether these proteins can be used as biomarkers of iNPH. We examined AQP1 and AQP4 protein levels in the CSF of 179 participants (88 women) classified into 5 groups: possible iNPH (81 participants), hydrocephalus associated with other neurological disorders (13 participants), AD (41 participants), non-AD dementia (32 participants) and healthy controls (12 participants). We recorded each participant's demographic and clinical variables and indicated, when available in the clinical history, the record of cardiovascular and respiratory complications. An ELISA showed virtually no AQP content in the CSF. Information on the vascular risk factors (available for 61 patients) confirmed some type of vascular risk factor in 86% of the patients with possible iNPH and 58% of the patients with AD. In conclusion, the ELISA analysis showed insufficient sensitivity to detect the presence of AQP1 and AQP4 in CSF, ruling out the possible use of these proteins as biomarkers for diagnosing iNPH.

Predictive Value of Serum Antibodies and Point Mutations of AQP4, AQP1 and MOG in A Cohort of Spanish Patients with Neuromyelitis Optica Spectrum Disorders

The detection of IgG aquaporin-4 antibodies in the serum of patients with Neuromyelitis optica (NMO) has dramatically improved the diagnosis of this disease and its distinction from multiple sclerosis. Recently, a group of patients have been described who have an NMO spectrum disorder (NMOsd) and who are seronegative for AQP4 antibodies but positive for IgG aquaporin-1 (AQP1) or myelin oligodendrocyte glycoprotein (MOG) antibodies. The purpose of this study was to determine whether AQP1 and MOG could be considered new biomarkers of this disease; and if point mutations in the gDNA of AQP4, AQP1 and MOG genes could be associated with the etiology of NMOsd. We evaluated the diagnostic capability of ELISA and cell-based assays (CBA), and analyzed their reliability, specificity, and sensitivity in detecting antibodies against these three proteins. The results showed that both assays can recognize these antigen proteins under appropriate conditions, but only anti-AQP4 antibodies, and not AQP1 or MOG, appears to be a clear biomarker for NMOsd. CBA is the best method for detecting these antibodies; and serum levels of AQP4 antibodies do not correlate with the progression of this disease. So far, the sequencing analysis has not revealed a genetic basis for the etiology of NMOsd, but a more extensive analysis is required before definitive conclusions can be drawn.

Neuromyelitis Optica: Review and Utility of Testing Aquaporin-4 Antibody in Typical Optic Neuritis

Neuromyelitis optica (NMO) is an autoimmune, inflammatory demyelinating disorder often leading to severe vision impairment and disability. The discovery of a diagnostic biomarker, the aquaporin-4 antibody (AQP4-IgG), transformed the clinical diagnosis and treatment of NMO and broadened the spectrum of disease [NMO spectrum disorders (NMOSD)]. Though the antibody is highly sensitive and specific to NMOSD, routine testing in patients with typical optic neuritis is considered controversial. This article will provide a brief review of NMOSD and highlight the pros and cons of routine testing in typical optic neuritis.

Neuromyelitis optica and neuromyelitis optica spectrum disorders

PURPOSE OF REVIEW

The discovery of highly specific auto-antibodies directed against the water channel aquaporin 4 was a quantum leap in the definition, classification and management of neuromyelitis optica (NMO). Herein, we propose an update on epidemiological, clinical and therapeutic advances in the field, underlining unmet needs.

RECENT FINDINGS

Large-scale epidemiological studies have recently provided a more precise evaluation of NMO prevalence and a better stratification regarding ethnicity and sex. New criteria have been proposed for so-called NMO spectrum disorders (NMOSD) and their relevance is currently being assessed. The identification of a new clinical entity associated to antibodies against myelin oligodendrocyte glycoprotein questions the border of NMOSD.

SUMMARY

The concept of NMOSD is opening a new era in clinical practice, allowing an easier and more homogeneous diagnosis and an increase in newly identified cases. This will facilitate clinical studies and support new therapeutic trial. Future researches should focus on the position of seronegative NMOSD and myelin oligodendrocyte glycoprotein-IgG disorders in the field and on promising strategies, including the immune tolerisation approaches, to eventually cure NMO.

Aquaporin-4 antibodies in patients treated with natalizumab for suspected MS

Objective:

To evaluate (1) the frequency of aquaporin-4 antibody (AQP4-ab)-seropositive cases among patients treated with natalizumab (NAT) and previously diagnosed with MS (MS^NAT) in a nationwide cohort, (2) the clinical course of NAT-treated AQP4-ab–seropositive neuromyelitis optica spectrum disorder (NMOSD) patients (NMO^NAT), (3) AQP4-ab titers in NMO^NAT and AQP4-ab–seropositive NMOSD treated with other immunotherapies (NMO^IT), and (4) immune mechanisms influencing disease activity in NMO^NAT.

Methods:

MS^NAT serum samples were retrospectively screened with a cell-based assay for AQP4-IgG and titers determined by ELISA. The annualized relapse rate (ARR) and disability progression were assessed. Serum levels of proinflammatory cytokines (interleukin [IL]-1β, IL-4, IL-6, IL-8, IL-10, IL-17, IL-21, and interferon [IFN]-γ) and the chemokine CXCL-10 of NMO^NAT patients identified in this (n = 4) and a previous study (n = 5) were measured by cytometric bead array and ELISA.

Results:

Of the 1,183 MS^NAT patients (851 female, median 9 NAT infusions), only 4 (0.33%; 3 female, 1 male) had AQP4-IgG. Of these, 2 fulfilled the 2006 NMO criteria and all met the 2015 NMOSD criteria. The ARR was higher in NMO^NAT vs MS^NAT (p = 0.0182). All 4 NMO^NAT patients had relapses and 2 had an increase of disability. AQP4-ab titers were higher in NMO^NAT (n = 9) vs NMO^IT (n = 13; p = 0.0059). IL-8, IL-1β, and IFN-γ serum levels were significantly higher, and CXCL-10 was significantly lower in NMO^NAT vs NMO^IT.

Conclusions:

Misdiagnosis of NMOSD with MS is rare. NAT was not able to control disease activity in NMO^NAT patients, who had higher serum levels of AQP4-IgG and proinflammatory cytokines than patients with NMOSD treated with other immunotherapies.

Comparative Analysis for the Presence of IgG Anti-Aquaporin-1 in Patients with NMO-Spectrum Disorders

Detection of IgG anti-Aquaporin-4 (AQP4) in serum of patients with Neuromyelitis optica syndrome disorders (NMOSD) has improved diagnosis of these processes and differentiation from Multiple sclerosis (MS). Recent findings also claim that a subgroup of patients with NMOSD, serum negative for IgG-anti-AQP4, present antibodies anti-AQP1 instead. Explore the presence of IgG-anti-AQP1 using a previously developed cell-based assay (CBA) highly sensitive to IgG-anti-AQP4. Serum of 205 patients diagnosed as NMOSD (8), multiple sclerosis (94), optic neuritis (39), idiopathic myelitis (29), other idiopathic demyelinating disorders of the central nervous system (9), other neurological diseases (18) and healthy controls (8), were used in a CBA over fixed HEK cells transfected with hAQP1-EGFP or hM23-AQP4-EGFP, treated with Triton X-100 and untreated. ELISA was also performed. Analysis of serum with our CBA indicated absence of anti-AQP1 antibodies, whereas in cells pretreated with detergent, noisy signal made reliable detection impossible. ELISA showed positive results in few serums. The low number of NMOSD serums included in our study reduces its power to conclude the specificity of AQP1 antibodies as new biomarkers of NMOSD. Our study does not sustain detection of anti-AQP1 in serum of NMOSD patients but further experiments are expected.

False positivity of anti aquaporin-4 antibodies in natalizumab-treated patients

BACKGROUND

Neuromyelitis optica spectrum disorders (NMOSD) represent a differential diagnosis of multiple sclerosis (MS). Detection of anti-aquaporin-4 antibodies (AQP4-Ab) is the strongest argument to confirm NMOSD. Diagnosing NMOSD is a major concern because specific MS disease modifying drugs can lead to neurological worsening.

OBJECTIVE

To report the case of two natalizumab (NTZ) treated patients who presented a false positive result for AQP4-Ab.

METHODS

A retrospective analysis of NTZ-treated patients who were tested positive for AQP4-Ab in our MS center.

RESULTS

Two patients treated by NTZ presented a false positive result.

CONCLUSIONS

Clinicians should be aware of potential technical issues in detecting AQP4-Ab in NTZ-treated patients leading to false positive results.