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Prion diseases, synucleinopathies and tauopathies are neurodegenerative disorders characterized by deposition of abnormal protein aggregates in brain and other tissues. These aggregates consist of misfolded forms of prion, α-synuclein (αSyn), or tau proteins that cause neurodegeneration and represent hallmarks of these disorders. A main challenge in the management of these diseases is the accurate detection and differentiation of these abnormal proteins during the early stages of disease before the onset of severe clinical symptoms. Unfortunately, many clinical manifestations may occur only after neuronal damage is already advanced and definite diagnoses typically require post-mortem neuropathological analysis. Over the last decade, several methods have been developed to increase the sensitivity of prion detection with the aim of finding reliable assays for the accurate diagnosis of prion disorders. Among these, the real-time quaking-induced conversion (RT–QuIC) assay now provides a validated diagnostic tool for human patients, with positive results being accepted as an official criterion for a diagnosis of probable prion disease in multiple countries. In recent years, applications of this approach to the diagnosis of other prion-like disorders, such as synucleinopathies and tauopathies, have been developed. In this review, we summarize the current knowledge on the use of the RT-QuIC assays for human proteopathies.

Prion diseases, synucleinopathies and tauopathies are neurodegenerative disorders characterized by deposition of abnormal protein aggregates in brain and other tissues. These aggregates consist of misfolded forms of prion, α-synuclein (αSyn), or tau proteins that cause neurodegeneration and represent hallmarks of these disorders. A main challenge in the management of these diseases is the accurate detection and differentiation of these abnormal proteins during the early stages of disease before the onset of severe clinical symptoms. Unfortunately, many clinical manifestations may occur only after neuronal damage is already advanced and definite diagnoses typically require post-mortem neuropathological analysis. Over the last decade, several methods have been developed to increase the sensitivity of prion detection with the aim of finding reliable assays for the accurate diagnosis of prion disorders. Among these, the real-time quaking-induced conversion (RT–QuIC) assay now provides a validated diagnostic tool for human patients, with positive results being accepted as an official criterion for a diagnosis of probable prion disease in multiple countries. In recent years, applications of this approach to the diagnosis of other prion-like disorders, such as synucleinopathies and tauopathies, have been developed. In this review, we summarize the current knowledge on the use of the RT-QuIC assays for human proteopathies. [ABSTRACT FROM AUTHOR]

Adult-onset neurodegenerative disorders, like Parkinson's disease (PD) and dementia with Lewy bodies (DLB), that share the accumulation of aggregated α-synuclein (αSynagg) as their hallmark molecular pathology are collectively known as α-synucleinopathies. Diagnosing α-synucleinopathies requires the post-mortem detection of αSynagg in various brain regions. Recent efforts to measure αSynagg in living patients include quantifying αSynagg in different biofluids as a biomarker for PD. We adopted the real-time quaking-induced conversion (RT-QuIC) assay to detect very low levels of αSynagg. We first optimized RT-QuIC for sensitivity, specificity, and reproducibility by using monomeric recombinant human wild-type αSyn as a substrate and αSynagg as the seed. Next, we exposed mouse microglia to αSyn pre-formed fibrils (αSynPFF) for 24 h. RT-QuIC assay revealed that the αSynPFF is taken up rapidly by mouse microglia, within 30 min, and cleared within 24 h. We then evaluated the αSyn RT-QuIC assay for detecting αSynagg in human PD, DLB, and Alzheimer's disease (AD) post-mortem brain homogenates (BH) along with PD and progressive supranuclear palsy (PSP) cerebrospinal fluid (CSF) samples and then determined protein aggregation rate (PAR) for αSynagg. The PD and DLB BH samples not only showed significantly higher αSynagg PAR compared to age-matched healthy controls and AD, but RT-QuIC was also highly reproducible with 94% sensitivity and 100% specificity. Similarly, PD CSF samples demonstrated significantly higher αSynagg PAR compared to age-matched healthy controls, with 100% sensitivity and specificity. Overall, the RT-QuIC assay accurately detects αSynagg seeding activity, offering a potential tool for antemortem diagnosis of α-synucleinopathies and other protein-misfolding disorders. [ABSTRACT FROM AUTHOR]

The misfolding of proteins such as the prion protein, α-synuclein, and tau represents a key initiating event for pathogenesis of most common neurodegenerative disorders, and its presence correlates with infectivity. To date, the diagnosis of these disorders mainly relied on the recognition of clinical symptoms when neurodegeneration was already at an advanced phase. In recent years, several efforts have been made to develop new diagnostic tools for the early diagnosis of prion diseases. The real-time quaking-induced conversion (RT–QuIC) assay, an in vitro assay that can indirectly detect very low amounts of PrPSc aggregates, has provided a very promising tool to improve the early diagnosis of human prion diseases. Over the decade since RT–QuIC was introduced, the diagnosis of not only prion diseases but also synucleinopathies and tauopathies has greatly improved. Therefore, in our study, we summarize the current trends and knowledge of RT–QuIC assays, as well as discuss the diagnosis of neurodegenerative diseases using RT–QuIC assays, which have been updated in recent years.

The misfolding of proteins such as the prion protein, α-synuclein, and tau represents a key initiating event for pathogenesis of most common neurodegenerative disorders, and its presence correlates with infectivity. To date, the diagnosis of these disorders mainly relied on the recognition of clinical symptoms when neurodegeneration was already at an advanced phase. In recent years, several efforts have been made to develop new diagnostic tools for the early diagnosis of prion diseases. The real-time quaking-induced conversion (RT–QuIC) assay, an in vitro assay that can indirectly detect very low amounts of PrPSc aggregates, has provided a very promising tool to improve the early diagnosis of human prion diseases. Over the decade since RT–QuIC was introduced, the diagnosis of not only prion diseases but also synucleinopathies and tauopathies has greatly improved. Therefore, in our study, we summarize the current trends and knowledge of RT–QuIC assays, as well as discuss the diagnosis of neurodegenerative diseases using RT–QuIC assays, which have been updated in recent years. [ABSTRACT FROM AUTHOR]