Related Experiment Video
Updated: Jun 15, 2025
Real-time Quaking-induced Conversion Assay for Detection of CWD Prions in Fecal Material
Published on: September 29, 2017
Longitudinal detection of prion infection in preclinical sheep blood samples compared using 3 assays
Charlotte M Thomas1, M Khalid F Salamat1, Florian Almela2
1The Roslin Institute, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Edinburgh, United Kingdom.
Abstract:
Variant Creutzfeldt-Jakob disease (vCJD) is a devastating disease caused by transmission of bovine spongiform encephalopathy to humans. Although vCJD cases are now rare, evidence from appendix surveys suggests that a small proportion of the United Kingdom population may be infected without showing signs of disease. These "silent" carriers could present a risk of iatrogenic vCJD transmission through medical procedures or blood/organ donation, and currently there are no validated tests to identify infected asymptomatic individuals using easily accessible samples. To address this issue, we evaluated the performance of 3 blood-based assays in a blinded study, using longitudinal sample series from a well-established large animal model of vCJD. The assays rely on amplification of misfolded prion protein (PrPSc; a marker of prion infection) and include real-time quaking-induced conversion (RT-QuIC), and 2 versions of protein misfolding cyclic amplification (PMCA). Although diagnostic sensitivity was higher for both PMCA assays (100%) than RT-QuIC (61%), all 3 assays detected prion infection in blood samples collected 26 months before the onset of clinical signs and gave no false-positive results. Parallel estimation of blood prion infectivity titers in a sensitive transgenic mouse line showed positive correlation of infectivity with PrPSc detection by the assays, suggesting that they are suitable for detection of asymptomatic vCJD infection in the human population. This study represents, to our knowledge, the largest comparison to date of preclinical prion detection in blood samples from a relevant animal model. The outcomes will guide efforts to improve early detection of prion disease and reduce infection risks in humans.
Insights
New blood tests can detect prion infection, the cause of variant Creutzfeldt-Jakob disease (vCJD), in asymptomatic individuals up to 26 months before clinical signs appear. This breakthrough aids in preventing disease transmission through medical procedures and donations.
Area of Science:
- Neuroscience
- Infectious Diseases
- Biochemistry
Background:
- Variant Creutzfeldt-Jakob disease (vCJD) is a fatal neurodegenerative disorder linked to prion protein (PrPSc) transmission.
- Asymptomatic carriers pose a risk for iatrogenic vCJD transmission via medical procedures and donations.
- Current diagnostic methods lack validated blood tests for detecting preclinical vCJD.
Purpose of the Study:
- To evaluate the performance of three blood-based prion detection assays in a large animal model of vCJD.
- To assess the capability of these assays in identifying asymptomatic prion infection.
- To determine the potential of these assays for early vCJD detection and risk reduction.
Main Methods:
- A blinded study was conducted using longitudinal blood samples from a well-established large animal model of vCJD.
- Three assays were evaluated: real-time quaking-induced conversion (RT-QuIC) and two versions of protein misfolding cyclic amplification (PMCA).
- Assay performance was compared against prion infectivity titers measured in a transgenic mouse model.
Main Results:
- Protein misfolding cyclic amplification (PMCA) assays demonstrated 100% diagnostic sensitivity, while real-time quaking-induced conversion (RT-QuIC) showed 61% sensitivity.
- All three assays successfully detected prion infection in blood samples taken 26 months prior to the onset of clinical signs.
- No false-positive results were observed across the evaluated assays.
- Prion detection correlated positively with blood prion infectivity titers.
Conclusions:
- The evaluated blood-based assays, particularly PMCA, show promise for detecting asymptomatic prion infection in vCJD.
- These assays can identify infection significantly before clinical manifestation, offering a window for intervention.
- The findings support the development of strategies to mitigate iatrogenic transmission risks and improve early diagnosis of prion diseases.
