Article

Antibody to aquaporin-4 in the long-term course of neuromyelitis optica

Neurosciences Group, Weatherall Institute of Molecular Medicine, and Department of Neurology, John Radcliffe Hospital, University of Oxford, UK.
Brain (Impact Factor: 10.23). 11/2008; 131(Pt 11):3072-80. DOI: 10.1093/brain/awn240
Source: PubMed

ABSTRACT Neuromyelitis optica (NMO) is a severe inflammatory CNS disorder of putative autoimmune aetiology, which predominantly affects the spinal cord and optic nerves. Recently, a highly specific serum reactivity to CNS microvessels, subpia and Virchow-Robin spaces was described in patients with NMO [called NMO-IgG (NMO-immunoglobulin G)]. Subsequently, aquaporin-4 (AQP4), the most abundant water channel in the CNS, was identified as its target antigen. Strong support for a pathogenic role of the antibody would come from studies demonstrating a correlation between AQP4-Ab (AQP4-antibody) titres and the clinical course of disease. In this study, we determined AQP4-Ab serum levels in 96 samples from eight NMO-IgG positive patients (median follow-up 62 months) in a newly developed fluorescence-based immunoprecipitation assay employing recombinant human AQP4. We found that AQP4-Ab serum levels correlate with clinical disease activity, with relapses being preceded by an up to 3-fold increase in AQP4-Ab titres, which was not paralleled by a rise in other serum autoantibodies in one patient. Moreover, AQP4-Ab titres were found to correlate with CD19 cell counts during therapy with rituximab. Treatment with immunosuppressants such as rituximab, azathioprine and cyclophosphamide resulted in a marked reduction in antibody levels and relapse rates. Our results demonstrate a strong relationship between AQP4-Abs and clinical state, and support the hypothesis that these antibodies are involved in the pathogenesis of NMO.

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    ABSTRACT: Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the CNS with severe involvement of the optic nerve and spinal cord. Highly specific serum IgG autoantibodies (NMO-IgG) that react with aquaporin-4 (AQP4), the most abundant CNS water channel protein, are found in patients with NMO. However, in vivo evidence combining the results of AQP4 antibody serum levels and brain pathology is lacking. We report a patient with NMO whose AQP4 antibody levels decreased simultaneously with clinical deterioration caused by the development of a tumor-like brain lesion. In the seminecrotic biopsied brain lesion, there was activated complement complex, whereas only very scattered immunoreactivity to AQP4 protein was detectable. The decrease in serum AQP4 antibody levels and the loss of AQP4 in the tumor-like lesion could represent a "serum antibody-consuming effect" during lesion formation.This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License, where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially.
    Journal of Neuropathology and Experimental Neurology 02/2015; DOI:10.1097/NEN.0000000000000173 · 4.37 Impact Factor
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    ABSTRACT: Identification of aquaporin-4 antibodies in neuromyelitis optica is highly important to provide early diagnosis for starting pathogenetic treatment, and for differential diagnosis in neuromyelitis optica spectrum disorders. In this paper, we review current methods of detection of aquaporin-4 antibodies. We present our data on the identification of aquaporin-4 antibodies by ELISA with antigen-presenting cells and evaluate the diagnostic value of this method. Aquaporin-4 antibodies were detected in 83.33% of patients with neuromyelitis optica, in 6.67% of patients with longitudinally extensive transverse myelitis, and in 100% of patients with systemic lupus erythematosus with longitudinally extensive transverse myelitis. The assay sensitivity was 83% in neuromyelitis optica and 24% in neuromyelitis optica spectrum disorders; the specificity was 100%.
    Neurochemical Journal 07/2014; 8(3):214-220. DOI:10.1134/S181971241403012X · 0.19 Impact Factor
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    ABSTRACT: Background Neuromyelitis optica (NMO) is a severe demyelinating disorder of the central nervous system (CNS) associated with the presence of an autoimmune antibody response (AQP4-IgG) against the water channel aquaporin-4 (AQP4). It remains unclear whether pathologic AQP4-IgG in the CNS is produced entirely by peripheral plasma cells or is generated in part by infiltrating B cells. To determine the overlap of AQP4-IgG idiotypes between the CNS and periphery, we compared the immunoglobulin G (IgG) transcriptome of cerebrospinal fluid (CSF) plasmablasts with the CSF and serum IgG proteomes in 7 AQP4-seropositive NMO patients following exacerbation.MethodsCSF variable region Ig heavy- (VH) and light-chain (VL) transcriptome libraries were generated for each patient from CSF plasmablasts by single cell sorting, reverse transcriptase polymerase chain reaction (RT-PCR), and DNA sequencing. Recombinant antibodies were generated from clonally expanded, paired VH and VL sequences and tested for AQP4-reactivity by cell-binding assay. CSF and serum IgG fractions were searched for sequences that matched their respective CSF IgG transcriptome. Matching peptides within the same patient¿s CSF and serum IgG proteomes were also identified.ResultsIn each NMO patient, we recovered CSF IgG VH and VL sequences that matched germline-mutated IgG protein sequences from the patient¿s CSF and serum IgG proteomes. Although a modest variation was observed between patients, the overlap between the transcriptome and proteome sequences was found primarily, but not exclusively, within the CSF. More than 50% of the CSF IgG transcriptome sequences were exclusively found in the CSF IgG proteome, whereas 28% were found in both the CSF and blood IgG proteome, and 18% were found exclusively in the blood proteome. A comparable distribution was noted when only AQP4-specific IgG clones were considered. Similarly, on average, only 50% of the CSF IgG proteome matched corresponding peptide sequences in the serum.Conclusions During NMO exacerbations, a substantial fraction of the intrathecal Ig proteome is generated by an intrathecal B cell population composed of both novel and peripherally-derived clones. Intrathecal CSF B cell clones may contribute to NMO disease exacerbation and lesion formation and may be an important target for preventative therapies.
    Journal of Neuroinflammation 01/2015; 12(1):19. DOI:10.1186/s12974-015-0240-9 · 4.90 Impact Factor

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