Early Detection of Abnormal Prion Protein in Genetic Human Prion Diseases Now Possible Using Real-Time QUIC Assay

Kazunori Sano,Katsuya Satoh,Matthias Schmitz,Noriyuki Nishida,Hiroyuki Murai,Ryuichiro Atarashi,Hiroshi Takashima,Mari Yoshida,Yong-Sun Kim,Nobuo Sanjo,Hidehiro Mizusawa,Inga Zerr,Yasushi Iwasaki

doi:10.1371/journal.pone.0054915

Abstract

IntroductionThe definitive diagnosis of genetic prion diseases (gPrD) requires pathological confirmation. To date, diagnosis has relied upon the finding of the biomarkers 14-3-3 protein and total tau (t-tau) protein in the cerebrospinal fluid (CSF), but many researchers have reported that these markers are not sufficiently elevated in gPrD, especially in Gerstmann-Sträussler-Scheinker syndrome (GSS). We recently developed a new in vitro amplification technology, designated “real-time quaking-induced conversion (RT-QUIC)”, to detect the abnormal form of prion protein in CSF from sporadic Creutzfeldt-Jakob disease (sCJD) patients. In the present study, we aimed to investigate the presence of biomarkers and evaluate RT-QUIC assay in patients with gPrD, as the utility of RT-QUIC as a diagnostic tool in gPrD has yet to be determined.Method/Principal Findings56 CSF samples were obtained from gPrD patients, including 20 cases of GSS with P102L mutation, 12 cases of fatal familial insomnia (FFI; D178N), and 24 cases of genetic CJD (gCJD), comprising 22 cases with E200K mutation and 2 with V203I mutation. We subjected all CSF samples to RT-QUIC assay, analyzed 14-3-3 protein by Western blotting, and measured t-tau protein using an ELISA kit. The detection sensitivities of RT-QUIC were as follows: GSS (78%), FFI (100%), gCJD E200K (87%), and gCJD V203I (100%). On the other hand the detection sensitivities of biomarkers were considerably lower: GSS (11%), FFI (0%), gCJD E200K (73%), and gCJD V203I (67%). Thus, RT-QUIC had a much higher detection sensitivity compared with testing for biomarkers, especially in patients with GSS and FFI.Conclusion/SignificanceRT-QUIC assay is more sensitive than testing for biomarkers in gPrD patients. RT-QUIC method would thus be useful as a diagnostic tool when the patient or the patient's family does not agree to genetic testing, or to confirm the diagnosis in the presence of a positive result for genetic testing.

Highlights

The definitive diagnosis of genetic prion diseases requires pathological confirmation
The real-time quaking-induced conversion (RT-QUIC) in vitro PrPSc amplification assay for diagnosis of prion disease has shown 84% sensitivity and 100% specificity in cerebrospinal fluid (CSF) samples from sporadic CJD patients
To determine the value of RT-QUIC in genetic prion disease diagnosis, we analyzed a total of 56 CSF samples from patients with various genetic forms of human prion disease (Table 1)

Summary

Introduction

The definitive diagnosis of genetic prion diseases (gPrD) requires pathological confirmation. Diagnosis has relied upon the finding of the biomarkers 14-3-3 protein and total tau (t-tau) protein in the cerebrospinal fluid (CSF), but many researchers have reported that these markers are not sufficiently elevated in gPrD, especially in GerstmannStraussler-Scheinker syndrome (GSS). We recently developed a new in vitro amplification technology, designated ‘‘real-time quaking-induced conversion (RT-QUIC)’’, to detect the abnormal form of prion protein in CSF from sporadic CreutzfeldtJakob disease (sCJD) patients. Prion diseases (PrD) are fatal neurodegenerative disorders characterized by the accumulation of abnormal prion protein (PrPSc) in the CNS. The genetic form of human PrD (gPrD) is caused by mutations in the prion protein gene (PRNP), and is classified into genetic CJD (gCJD), Gerstmann-Straussler-Scheinker syndrome (GSS), and fatal familial insomnia (FFI).

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