E-Mail karger@karger.com Short Report Eur Neurol 2014;72:271–272 DOI: 10.1159/000364904 Aquaporin-1 Antibody in Neuromyelitis Optica Patients Erdem Tüzün a John Tzartos c Esme Ekizoğlu a Christos Stergiou c Paraskevi Zisimopoulou c Arzu Çoban a Erkingül Shugaiv a Recai Türkoğlu b Murat Kürtüncü a Betül Baykan a Socrates Tzartos c a Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, b Department of Neurology, Haydarpasa Numune Education and Research Hospital, Istanbul, Turkey; c Hellenic Pasteur Institute, Athens, Greece agnostic biomarker [1]. However, in sev- eral NMO cohorts more than 40% of NMO patients have been found Aqp-4 antibody negative [2, 3], prompting a search for oth- er antibodies. Aqp-1 has aroused interest as a potential autoantigen in NMO since it is one of the major water channels of the cen- tral nervous system (CNS), is abundantly expressed by astrocytes and some NMO le- sions might show reduced Aqp-1 expres- sion [4–7]. In this study, Aqp-1 and Aqp-4 antibody measurements were conducted in sera of NMO patients and controls. Materials and Methods Thirty consecutive NMO patients ful- filling Wingerchuk’s revised diagnostic cri- teria [1], 29 relapsing remitting multiple sclerosis (MS) patients fulfilling revised McDonald criteria [8], 29 idiopathic intra- cranial hypertension (IIH) patients fulfill- ing the modified diagnostic criteria [9] and 30 healthy individuals were included. Pa- tients gave informed consent, which was approved by the local medical research eth- ics committee. All sera were collected dur- ing an attack prior to treatment with ste- roids, immediately centrifuged, stored in aliquots at −70  °  C. Antibodies to the extracellular region of Aqp-4 were measured by cell-based assay utilizing HEK cells transfected with Aqp-4 Key Words Aquaporin-1 · Aquaporin-4 · Neuromyelitis optica · Antibody · Autoimmunity Abstract Background/Methods: To find out the prev- alence of aquaporin-antibody (Aqp-Ab) and characterize Aqp-Ab associated clinical fea- tures in NMO, Aqp-1 and Aqp-4-Abs were examined using radioimmunoprecipitation and cell-based assays, respectively. Results: Aqp-4 and Aqp-1-Abs were detected in 20/30 and 8/30 NMO patients, respectively. One patient was Aqp-1-Ab single-positive, 13 patients were Aqp-4-Ab single-positive, 7 patients were Aqp-4/Aqp-1-Ab double-posi- tive and 9 patients were seronegative. All double-positive patients had optic neuritis during the first attack. Only 2/29 MS patients and none of the control idiopathic intracra- nial hypertension patients were Aqp-1-Ab positive. Conclusion: Aqp-1-Ab is usually de- tected in Aqp-4-Ab positive NMO patients and might be involved in optic neuritis pathogenesis. © 2014 S. Karger AG, Basel Introduction Aquaporin-4 (Aqp-4) antibody has long been described in neuromyelitis opti- ca (NMO) and been utilized as a useful di- Received: March 17, 2014 Accepted: May 25, 2014 Published online: September 27, 2014 Erdem Tüzün, MD Department of Neurology, Istanbul Faculty of Medicine Istanbul University TR–34390 Çapa, Istanbul (Turkey) E-Mail drerdem  @  yahoo.com © 2014 S. Karger AG, Basel 0014–3022/14/0726–0271$39.50/0 www.karger.com/ene DNA. Aqp-1 antibodies were detected by radioimmunoprecepitation assay (RIPA). All sera that were detected positive in RIPA were further analyzed with ELISA with Aqp-1 synthetic peptides to ensure that the antibodies against Aqp-1 bind to the extra- cellular domain of the protein [4]. Only sera with antibodies to the extracellular side of Aqp-1 were considered positive. Results Aqp-4 antibody was detected in 20 NMO patients and none of the MS patients, whereas Aqp-1 antibody was detected in 8 NMO and 2 MS patients. IIH patients and healthy controls were seronegative for both antibodies. Only one NMO patient was Aqp-1 antibody single positive (Aqp-1+), 7 NMO patients were Aqp-1 and Aqp-4 an- tibody double positive (Aqp-1+/Aqp-4+), 13 NMO patients were Aqp-4 antibody sin- gle positive (Aqp-4+) and 9 NMO patients were seronegative (SN) for both antibodies. Aqp-4+ positive patients had higher EDSS scores than Aqp-1+/Aqp-4+ and SN patients and both Aqp-1+/Aqp-4+ and Aqp-4+ patients had higher attack num- bers than SN patients. Double-positive pa- tients had a significantly higher rate of op- tic neuritis during the first attack than SN patients. Other parameters were compa- rable among groups (table 1). Retrospec- Downloaded by: Istanbul Universitesi 194.27.138.2 - 10/9/2014 8:19:04 AM