Rapid and ultra-sensitive quantitation of disease-associated α-synuclein seeds in brain and cerebrospinal fluid by αSyn RT-QuIC
Abstract The diagnosis and treatment of synucleinopathies such as Parkinson disease and dementia with Lewy bodies would be aided by the availability of assays for the pathogenic disease-associated forms of α-synuclein (αSyn D ) that are sufficiently sensitive, specific, and practical for analysis of accessible diagnostic specimens. Two recent αSyn D seed amplification tests have provided the first prototypes for ultrasensitive and specific detection of αSyn D in patients’ cerebrospinal fluid. These prototypic assays require 5–13 days to perform. Here, we describe an improved α-synuclein real time quaking-induced conversion (αSyn RT-QuIC) assay that has similar sensitivity and specificity to the prior assays, but can be performed in 1–2 days with quantitation. Blinded analysis of cerebrospinal fluid from 29 synucleinopathy cases [12 Parkinson’s and 17 dementia with Lewy bodies] and 31 non-synucleinopathy controls, including 16 Alzheimer’s cases, yielded 93% diagnostic sensitivity and 100% specificity for this test so far. End-point dilution analyses allowed quantitation of relative amounts of αSyn D seeding activity in cerebrospinal fluid samples, and detection in as little as 0.2 μL. These results confirm that αSyn D seeding activity is present in cerebrospinal fluid. We also demonstrate that it can be rapidly detected, and quantitated, even in early symptomatic stages of synucleinopathy.