Detection of aquaporin-4 antibody status of Thai patients with neuromyelitis optica spectrum disorders using a recombinant Escherichia coli aquaporin-4 enzyme-linked immunosorbent assay

Abstract

© 2014 Japanese Society for Neuroimmunology. Objectives Neuromyelitis optica (NMO) is a severe inflammatory demyelinating disease of the central nervous system. Detection of a highly specific autoantibody to aquaporin-4 (AQP4) in the serum has been used as a diagnostic marker for NMO. The aim of the present study was to evaluate and validate the enzyme-linked immunosorbent assay (ELISA) for detecting AQP4 antibody using recombinant AQP4 antigen expressed on Escherichia coli, and assessing its usefulness in diagnosis of NMO among Thai patients. Methods Sera of the 57 patients who attended the neurology service at Siriraj Hospital and were suspected to have central nervous system demyelinating diseases were tested, along with the sera of normal subjects. AQP4 with a green fluorescent tag was expressed on E. coli BL21 DE3 pLysS. Assessment of the AQP4 antibody was carried out using ELISA, and the obtained data were compared with pre- and post-fixed cell-based indirect immunofluorescence assay (CBA-kit and Sendai method cell-based assay), and tissue-based indirect immunofluorescence assay. Results Recombinant AQP4 proteins were successfully expressed in the E. coli. Crude lysates of E. coli expressing full length AQP4 were used as antigens for the patients' sera in the ELISA. The sensitivity and specificity of the ELISA were 96.7% and 92.3%, respectively, and they were highly correlated (kappa coefficient, 0.894) compared with the Sendai method cell-based assay. Conclusions The detection of AQP4 antibodies with ELISA using recombinant E. coli AQP4 antigen provides highly sensitive and specific diagnoses for Thai spectrum disorders patients. This method should be used as an economically viable alternative routine screening test for patients whose clinical symptoms suggest NMO.