ELISA method for Aβ oligomers in cerebrospinal fluid.
A) Schematic drawing of the principle for the method. Left: The Aβo ELISA is based on the use of the same N-terminal anti-Aβ monoclonal antibody twice. The ELISA plate is coated with 82E1 to capture all forms of Aβ, while biotinylated 82E1 is used for detection. A synthetic Aβ dimer, with two N-termini, is used as standard. Middle: Aβos, with several free N-terminals, are detected in the assay. Right: monomeric Aβ will have their epitopes blocked by the capture antibody and are thus not detected by the detection antibody. B) Example of a typical standard curve from the Aβo assay. The standard curve ranges from 200–102,400 fg/mL. The assay has a lower limit of quantification of 200 fg/mL. C) Measurement of synthetic Aβo formation by the Aβo ELISA. Synthetic Aβ1–42 was allowed to aggregate into Aβ oligomers. The signal in the Aβo ELISA was compared with a Thioflavin-T (ThT) assay for aggregated Aβ. The Aβo ELISA detects the formation of synthetic Aβo at an earlier stage than the ThT assay, while following the increase of oligomerization in parallel with the ThT assay after 5 hours.