B-083 Novel High Affinity Monoclonal Antibodies for Specific Detection of Neurofilament Light Protein in Serum and Cerebrospinal Fluid

Abstract Background Neurofilaments are very important protein components of axons, and they maintain the function of nervous system. Cerebrospinal fluid (CSF) and serum neurofilament levels elevate due to damages in nervous system making neurofilaments promising biomarkers for neural diseases and injuries, such as Alzheimer’s disease, traumatic brain injury and Multiple sclerosis. Based on their size, neurofilaments are divided in groups: Neurofilament light (NfL), neurofilament medium (NfM), neurofilament heavy (NfH), α-internexin, and peripherin. Of these, NfL is considered to be the most promising biomarker since it is the most abundant form of neurofilaments. Methods We have developed four mouse monoclonal antibodies against human NfL. These antibodies, designated as Anti-h NfL 12601, 12603, 12604 or 12605, were tested as pairs in sandwich fluorescence-based immunoassay (FIA) with NfL spiked serum and buffer to determine linear measuring ranges and the matrix effect. Furthermore, the ability of the antibodies to measure NfL in clinical samples was tested in sandwich FIA by testing 10 CSF samples in the range of 0 to 5 083 pg/mL. The antibodies were also compared against commercially available reference antibodies in FIA. Kinetic parameters were determined with bio-layer interferometry (BLI). Results In sandwich FIA, the widest linear measuring range of 10 to 40 960 pg/mL of recombinant human NfL spiked in normal serum was achieved with antibody pair 12603 and 12604. In contrast, the commercial reference antibody pair achieved a linear measuring range of 2560 to 40 960 pg/mL. Matrix effect caused by serum was negligible. With clinical samples, the best correlation with the reference method (NF-light CSF ELISA from Uman Diagnostics) with a coefficient of correlation of 0.986 was achieved with antibody pair 12604 and 12601. This pair also showed a good correlation with the commercial reference pair with a coefficient of correlation of 0.984. In kinetics measurements, none of four antibodies showed dissociation indicating very high affinity. The fastest association of 4.0 × 105 1/Ms was achieved with antibody 12605. Conclusion These results demonstrate that the newly developed mouse monoclonal NfL antibodies are promising tools for development of diagnostic immunoassays measuring NfL levels in human serum and CSF samples. Comparison against commercial reference antibodies indicates that higher NfL detection sensitivity and wider detection ranges can be achieved with antibody pairs developed in this study. Additionally, the kinetic measurement results forecast these antibodies to be suitable for fast reaction kinetic assay formats, such as lateral flow assays, which might become a key resolution in acute neural injury diagnostics.