TY - JOUR T1 - Neurofilament light oligomers in neurodegenerative diseases: quantification by homogeneous immunoassay in cerebrospinal fluid JF - BMJ Neurology Open JO - BMJ Neurol Open DO - 10.1136/bmjno-2022-000395 VL - 5 IS - 1 SP - e000395 AU - Francisco J. Meda AU - Kathryn Knowles AU - Imogen J. Swift AU - Aitana Sogorb-Esteve AU - Jonathan D. Rohrer AU - Anna Dittrich AU - Ingmar Skoog AU - Silke Kern AU - Bruno Becker AU - Kaj Blennow AU - Ulf Andreasson AU - Hlin Kvartsberg AU - Henrik Zetterberg Y1 - 2023/02/01 UR - http://neurologyopen.bmj.com/content/5/1/e000395.abstract N2 - Background Neurofilament light (NfL) is a widely used biomarker for neurodegeneration. NfL is prone to oligomerisation, but available assays do not reveal the exact molecular nature of the protein variant measured. The objective of this study was to develop a homogeneous ELISA capable of quantifying oligomeric NfL (oNfL) in cerebrospinal fluid (CSF).Methods A homogeneous ELISA, based on the same capture and detection antibody (NfL21), was developed and used to quantify oNfL in samples from patients with behavioural variant frontotemporal dementia (bvFTD, n=28), non-fluent variant primary progressive aphasia (nfvPPA, n=23), semantic variant PPA (svPPA, n=10), Alzheimer’s disease (AD, n=20) and healthy controls (n=20). The nature of NfL in CSF, and the recombinant protein calibrator, was also characterised by size exclusion chromatography (SEC).Results CSF concentration of oNfL was significantly higher in nfvPPA (p<0.0001) and svPPA patients (p<0.05) compared with controls. CSF oNfL concentration was also significantly higher in nfvPPA compared with bvFTD (p<0.001) and AD (p<0.01) patients. SEC data showed a peak fraction compatible with a full-length dimer (~135 kDa) in the in-house calibrator. For CSF, the peak was found in a fraction of lower molecular weight (~53 kDa), suggesting dimerisation of NfL fragments.Conclusions The homogeneous ELISA and SEC data suggest that most of the NfL in both the calibrator and human CSF is present as a dimer. In CSF, the dimer appears to be truncated. Further studies are needed to determine its precise molecular composition.All data relevant to the study are included in the article or uploaded as online supplemental information. ER -