Measuring fg/mL Concentrations of Cytokines in Cerebrospinal Fluid (CSF)

Abstract Measuring low-abundance cytokines in CSF may be useful when studying brain and nervous system disorders. We recently developed novel immunoassays with fg/mL and sub-fg/mL detection limits that enable quantitation of low-abundance biomarkers in CSF. S-PLEXSM assays, utilizing MSD’s MULTI-ARRAY® electrochemiluminescence technology, were developed and analytically characterized and the concentrations of cytokines in CSF were measured using these assays. Assays for the following cytokines were used: IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-17A, IL-21, IFN-γ, GM-CSF, TSLP, and TNF-α. The lower limits of detection achieved for S-PLEX assays for these analytes ranged from ~0.2 fg/mL to ~50 fg/mL. Spike recovery and dilution linearity were between 80% and 120%. Depletion experiments demonstrated specificity for each analyte. Cytokine levels in the majority of apparently healthy CSF samples were measurable for 8 out of the 12 analytes tested. We have developed a next-generation assay format that is 100 to 1,000 times more sensitive than the current limits of standard ELISA technology. This increased sensitivity enables accurate quantitation of cytokine levels in the CSF of apparently healthy donors. These assays will allow for a better understanding of the role these cytokines play in brain and nervous system disorders.