Real-time quaking-induced conversion: a highly sensitive assay for prion detection

Abstract

We recently developed a new in vitro amplification technology, designated "real-time quaking-induced conversion (RT-QUIC)", for detection of the abnormal form of prion protein (PrPSc) in easily accessible specimens such as cerebrospinal fluid (CSF). After assessment of more than 200 CSF specimens from Japanese and Australian patients, we found no instance of a false positive, and more than 80% accuracy for the correct diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD). Furthermore, the RT-QUIC can be applied to other prion diseases, including scrapie, chronic wasting disease (CWD), and bovine spongiform encephalopathy (BSE), and is able to quantify prion seeding activity when combined with an end-point dilution of samples. These results indicate that the RT-QUIC, with its high sensitivity and specificity, will be of great use as an early, rapid and specific assay for prion diseases.

Figure 1

Hypothetical models for the inverse correlation between rPrP-sen concentration and fibril formation in a denaturant-free buffer with shaking in the absence (A) or presence of host-derived PrP^Sc (B). Homogeneous partial-unfolding of rPrP-sen is induced in the presence of denaturant or at low pH, leading to an increase of oligomer formation. In contrast, a heterogeneous denaturation status of rPrP-sen is presumed to be inversely proportional to the concentration in a denaturant-free buffer with shaking, resulting in a reduction of oligomer formation. It remains to be determined whether native-folded rPrP-sen can bind to PrP^Sc or rPrP-res polymers.