J Clin Neurol.  2016 Jan;12(1):101-106. 10.3988/jcn.2016.12.1.101.

Real-Time Quaking-Induced Conversion Analysis for the Diagnosis of Sporadic Creutzfeldt-Jakob Disease in Korea

• Park JH
• Choi YG
• Lee YJ
• Park SJ
• Choi HS
• Choi KC
• Choi EK
• Kim YS

• KMID: 2364926
• DOI: http://doi.org/10.3988/jcn.2016.12.1.101

Abstract

BACKGROUND AND PURPOSE
The level of 14-3-3 protein in the cerebrospinal fluid (CSF) is increased in Creutzfeldt-Jakob disease (CJD) patients, which has led to it being used as a clinical biomarker for the ante-mortem diagnosis of human prion diseases. However, the specificity of the 14-3-3 protein is less reliable for CJD diagnosis. Newly developed assays including real-time quaking-induced conversion (RT-QuIC) have made it possible to detect the PrPSc-like abnormal prion isoform with a high sensitivity in animal and human specimens that might contain a minute amount of PrP(Sc) due to in vitro prion replication.
METHODS
This study applied a highly sensitive RT-QuIC assay using recombinant human PrP to detect PrP(Sc) in the CSF of 81 patients with sporadic CJD (sCJD) in Korea.
RESULTS
RT-QuIC analysis of the CSF samples based on the expression levels of 14-3-3 and total tau proteins revealed positivity in 62 of 81 sCJD patients (sensitivity of 76.5%) but no positive results in the 100 non-CJD patients.
CONCLUSIONS
The sensitivity of the RT-QuIC in this study was similar to that in some previous reports, and the specificity of RT-QuIC was higher than that of 14-3-3 in CSF, suggesting that RT-QuIC analysis can complement the weakness of the specificity of 14-3-3 for the diagnosis of sCJD. These results indicate that RT-QuIC might be very useful for the rapid and specific diagnosis of sCJD and provide a practical novel method for the ante-mortem diagnosis of human prion diseases.

Keyword

Creutzfeldt-Jakob disease; cerebrospinal fluid; RT-QuIC; 14-3-3; total tau protein

MeSH Terms

14-3-3 Proteins
Animals
Cerebrospinal Fluid
Complement System Proteins
Creutzfeldt-Jakob Syndrome*
Diagnosis*
Humans
Korea*
Prion Diseases
Sensitivity and Specificity
tau Proteins
14-3-3 Proteins
Complement System Proteins
tau Proteins

Figure

• 

  Fig. 1 Detection limit of RT-QuIC using the brain homogenate (BH) of a sCJD patient as prion seeds. The colored curves indicate the kinetics of ThT fluorescence in an individual reaction seeded with 10% sCJD BH (w/v) at dilutions ranging from 10-6 to 10-11. The indicated dilutions (10-6 to 10-8) of normal human BH were used as negative controls. ThT fluorescence (y-axis) was measured in relative fluorescence units (rfu; i.e., relative to normal control BH), and the average fluorescence for each quadruplicate sample was monitored for 10 min (one cycle; x-axis). An rfu value of 400 for the normal human BH was considered as the baseline. The graphs are representative of three independent experiments. CJD: Creutzfeldt-Jakob disease, RT-QuIC: real-time quaking-induced conversion, sCJD: sporadic CJD, ThT: thioflavin T.

• 

  Fig. 2 Kinetics of RT-QuIC analysis using the CSF of sCJD patients. The four representative CSF samples of the patients with sCJD for the RT-QuIC reaction (A: four positive reactions of ThT fluorescence in the quadruplicate samples, B: three positive reactions in the quadruplicate samples, C: two positive reactions, D: one positive reaction) and the negative control (E-H: A-CSF). Each colored curve represents the kinetics of the ThT fluorescence (four colors for the quadruplicate samples). The graphs are representative of three independent experiments. A-CSF: artificial CSF, CSF: cerebrospinal fluid, RT-QuIC: real-time quaking-induced conversion, sCJD: sporadic CJD, ThT: thioflavin T.

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