The Use of Real-Time Quaking-Induced Conversion for the Diagnosis of Human Prion Diseases

Abstract

Prion diseases are rapidly progressive, invariably fatal, transmissible neurodegenerative disorders associated with the accumulation of the amyloidogenic form of the prion protein in the central nervous system (CNS). In humans, prion diseases are highly heterogeneous both clinically and neuropathologically. Prion diseases are challenging to diagnose as many other neurologic disorders share the same symptoms, especially at clinical onset. Definitive diagnosis requires brain autopsy to identify the accumulation of the pathological prion protein, which is the only specific disease biomarker. Although brain post-mortem investigation remains the gold standard for diagnosis, antemortem clinical, instrumental, and laboratory tests showing variable sensitivities and specificity, being surrogate disease biomarkers, have been progressively introduced in clinical practice to reach a diagnosis. More recently, the ultrasensitive Real-Time Quaking-Induced Conversion (RT-QuIC) assay, exploiting, for the first time, the detection of misfolded prion protein through an amplification strategy, has highly improved the “in-vitam” diagnostic process, reaching in cerebrospinal fluid (CSF) and olfactory mucosa (OM) around 96% sensitivity and close to 100% specificity. RT-QuIC also improved the detection of the pathologic prion protein in several peripheral tissues, possibly even before the clinical onset of the disease. The latter aspect is of great interest for the early and even preclinical diagnosis in subjects at genetic risk of developing the disease, who will likely be the main target population in future clinical trials. This review presents an overview of the current knowledge and future perspectives on using RT-QuIC to diagnose human prion diseases.

Αnti-prion effects of anthocyanins

“…(5) Quaking induces fragmentation of the PrP Sc fibrils. (6) The process is repeated [ 83 , 91 , 92 ]. (B) Aggregation of recPrP C in RT-QuIC was assessed in the CSF from twelve different CJD patients.…”

Characterisation of RT-QuIC negative cases from the UK National CJD Research and Surveillance programme

“…reviewing the effect of different recombinant prion protein substrates on VV1 and MM2C identified similar findings. Interestingly they also found that there was increased sensitivity in the improved QuIC (IQ-CSF) compared to the prior protocol QuIC (PQ-CSF) in those with MM2C (70% vs 40%) but this was found not to be the case in those with VV1 [ 25 , 26 ]. The reduced PrP sc seeding efficiency in these subtypes may correlate with the atypically long durations when compared to the other variants of sporadic CJD with a median duration of 3–5 months.…”

Automated microscopic measurement of fibrinaloid microclots and their degradation by nattokinase, the main natto protease

“…As with prions and other amyloid forms of proteins [98,107], that are often highly resistant to proteolysis (e.g. [108,109]), the existence of these ‘fibrinaloid’ microclots implies their comparative resistance to normal fibrinolysis [110,111], with their precise structures [112] being affected by other small and macromolecules and ions that they may have bound [97,103,113-119]. The varieties of stable macrostates into which a given amyloidogenic sequence can fold (even under the same conditions [120,121]) are referred to as different ‘strains’ [122-132] or ‘polymorphisms’ [133-144], and in some cases are sufficiently stable (i.e.…”