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 (αSynD) that are sufficiently sensitive, specific, and practical for analysis of accessible diagnostic specimens. Two recent αSynD seed amplification tests have provided the first prototypes for ultrasensitive and specific detection of αSynD 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 αSynD seeding activity in cerebrospinal fluid samples, and detection in as little as 0.2 μL. These results confirm that αSynD 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.
Highlights
Many neurodegenerative diseases are related to the accumulation of specific misfolded proteins
Rapid detection of αSynD by αSyn Real-Time Quaking-Induced Conversion (RT-QuIC) In developing our αSyn RT-QuIC, we focused primarily on a recombinant 6× histidine-tagged K23Q mutant of αSyn as a soluble recombinant αSyn (rαSyn) substrate for αSynD-induced fibrillization
This latter characteristic, we hypothesized, might improve the sensitivity of an αSyn RT-QuIC assay by enhancing the kinetic distinction between reactions seeded with samples from synucleinopathy cases versus controls
Summary
Many neurodegenerative diseases are related to the accumulation of specific misfolded proteins. These deposits are identified upon post-mortem analysis of brain tissue, allowing definite diagnoses to be made based on specific neuropathological and molecular findings. Early diagnosis can be difficult and Parkinson’s disease (PD), multiple system atrophy (MSA), dementia with Lewy bodies (DLB) [or Lewy body dementia] are called α-synucleinopathies due to the abnormal accumulation of aggregates of a protein called α-synuclein (αSyn) in the brain. In DLB, clinical diagnostic criteria for probable DLB predict αSyn pathology with sensitivity of about 80% [18] but early diagnosis of DLB is less accurate due to the overlapping symptoms with other types of dementia. In patients with AD and diffuse Lewy body pathology, disease duration was shortened [11], indicating that DLB pathology contributes to dementia progression
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