Early detection of abnormal prion protein in genetic human prion diseases now possible using real-time QUIC assay.
BACKGROUND
The 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.


RESULTS
56 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.


CONCLUSIONS
RT-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.
Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Kazunori
K
Sano
Katsuya
K
Satoh
Ryuichiro
R
Atarashi
Hiroshi
H
Takashima
Yasushi
Y
Iwasaki
Mari
M
Yoshida
Nobuo
N
Sanjo
Hiroyuki
H
Murai
Hidehiro
H
Mizusawa
Matthias
M
Schmitz
Inga
I
Zerr
Yong-Sun
YS
Kim
Noriyuki
N
Nishida
D048948:14-3-3 Proteins / Q000134:cerebrospinal fluid; D000328:Adult; D000368:Aged; D015415:Biomarkers; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017096:Prion Diseases / Q000175:diagnosis*; D011328:Prions / Q000134:cerebrospinal fluid*; D011994:Recombinant Proteins; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods; D016875:tau Proteins / Q000134:cerebrospinal fluid
D048948:14-3-3 Proteins; D015415:Biomarkers; D011328:Prions; D011994:Recombinant Proteins; D016875:tau Proteins