The Latest Research on RT-QuIC Assays—A Literature Review

Abstract

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.

Detection of Prions in Brain Homogenates and CSF Samples Using a Second-Generation RT-QuIC Assay: A Useful Tool for Retrospective Analysis of Archived Samples

“…Freshly prepared sCJD VV2 BH showed positivity both in RT-QuIC and western blot. The RT-QuIC assay of 92 post-mortem archival BH samples showed 97.4% sensitivity and 100% specificity, comparable to previously published results [12]. Our data suggest that BHs originally prepared for definitive post-mortem diagnosis and frozen for several years are generally suitable for RT-QuIC retrospective studies; however, the presence of one negative sample confirmed that long-term storage of BH, in the form of detergent lysate, may occasionally lead to a loss of RT-QuIC seeding activity.…”

“…The sensitivity and specificity of the method are respectable. According to various studies, they range from 73% to 97% and from 99% to 100%, respectively [12]; however, the sensitivity is not 100% and there have been several cases of CJD or genetic forms of prion diseases that were not detected as positive in various studies [13,14]. The reason why these cases were not reliably detected is not completely understood.…”

“…An improved version of the RT-QuIC assay, represented as the second-generation RT-QuIC assay, has recently been described, and is characterized by increased speed and high sensitivity [8][9][10][11]. The RT-QuIC method is able to detect the presence of a femtogram of PrP Sc in a CSF or nasal brushing sample, allowing for diagnosis of the disease at its beginning [12,13]. This opens the possibility of early administration of treatment, which may be ineffective when administrated later (i.e., when severe neurological symptoms have already appeared).…”

Neurochemical Markers of Traumatic Brain Injury: Relevance to Acute Diagnostics, Disease Monitoring, and Neuropsychiatric Outcome Prediction

“…Currently, there are no reliable fluid assays to quantify TDP-43 or -synuclein inclusions in individuals with TBI. With advances in the detection of misfolded seeds of α-synuclein in biofluids using real-time quaking-induced conversion or protein misfolding cyclic amplification (similar technologies to qualitatively detect trace amounts of diffusible misfolded α-synuclein, through its ability to induce aggregation of added recombinant αsynuclein in CSF over time, using thioflavin T fluorescence), brain -synuclein pathology can be reliably detected in lumbar CSF from patients with Parkinson's disease and other synucleinopathies (83). While so-called real-time-induced has been used to quantify TDP-43 in CSF of patients with amyotrophic lateral sclerosis and frontotemporal dementia (84), this…”

Neuropathology and molecular diagnosis of Synucleinopathies

“…Nevertheless, there are still some obstacles that need to be overcome in order for RT-QuIC to be a routine screening technique. First, the methods of these seeding assays, including a defined purification protocol for the substrate and sampling sites of peripheral tissues, must be standardized [ 260 , 261 ]. Second, the majority of studies lack autopsy-confirmed diagnosis.…”