Rapid and ultra-sensitive quantitation of disease-associated α-synuclein seeds in brain and cerebrospinal fluid by αSyn RT-QuIC

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 a-synuclein (alpha Syn(D)) that are sufficiently sensitive, specific, and practical for analysis of accessible diagnostic specimens. Two recent alpha Syn(D) seed amplification tests have provided the first prototypes for ultrasensitive and specific detection of alpha Syn(D) in patients' cerebrospinal fluid. These prototypic assays require 5-13 days to perform. Here, we describe an improved alpha-synuclein real time quaking-induced conversion (alpha Syn 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 alpha Syn(D) seeding activity in cerebrospinal fluid samples, and detection in as little as 0.2 mu L. These results confirm that alpha Syn(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.