Enzyme-linked immunosorbent assays for α-synuclein with species and multimeric state specificities

Abnormal intracellular deposition of aggregated α-synuclein is the characteristic feature of a number of neurological disorders, including Parkinson's disease (PD). Although α-synuclein is typically known as a cytosolic protein, a small amount is secreted by exocytosis in both monomeric and aggregated forms. The extracellular forms of α-synuclein in human body fluids, such as cerebrospinal fluid (CSF) and blood plasma, might be a diagnostic target for PD and related diseases. Here, we characterized a new set of monoclonal antibodies against α-synuclein, and using different combinations of antibodies, we established ELISA systems to specifically detect human α-synuclein, mouse and human α-synuclein together, and multimeric forms of α-synuclein in biological samples. By employing the Tyramide signal amplification method, the sensitivity of the assay was significantly improved to detect a concentration as low as ∼12.5 pg/ml. These assays might be useful tools for quantitative analysis of α-synuclein in various forms and with high sensitivity in diverse biological samples.