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Updated: Mar 30, 2026
Assessing Transmissible Spongiform Encephalopathy Species Barriers with an In Vitro Prion Protein Conversion Assay
Published on: March 10, 2015
Infectivity-associated PrP(Sc) and disease duration-associated PrP(Sc) of mouse BSE prions
Kohtaro Miyazawa1, Hiroyuki Okada1, Kentaro Masujin1
1a Influenza and Prion Disease Research Center; National Institute of Animal Health ; Tsukuba , Ibaraki , Japan.
Abstract:
Disease-related prion protein (PrP(Sc)), which is a structural isoform of the host-encoded cellular prion protein, is thought to be a causative agent of transmissible spongiform encephalopathies. However, the specific role of PrP(Sc) in prion pathogenesis and its relationship to infectivity remain controversial. A time-course study of prion-affected mice was conducted, which showed that the prion infectivity was not simply proportional to the amount of PrP(Sc) in the brain. Centrifugation (20,000 ×g) of the brain homogenate showed that most of the PrP(Sc) was precipitated into the pellet, and the supernatant contained only a slight amount of PrP(Sc). Interestingly, mice inoculated with the obtained supernatant showed incubation periods that were approximately 15 d longer than those of mice inoculated with the crude homogenate even though both inocula contained almost the same infectivity. Our results suggest that a small population of fine PrP(Sc) may be responsible for prion infectivity and that large, aggregated PrP(Sc) may contribute to determining prion disease duration.
Insights
Prion infectivity is not solely determined by the amount of disease-related prion protein (PrP(Sc)). Smaller PrP(Sc) aggregates appear crucial for prion infectivity, while larger aggregates may influence disease duration.
Area of Science:
- Neuroscience
- Molecular Biology
- Infectious Diseases
Background:
- Transmissible spongiform encephalopathies are linked to disease-related prion protein (PrP(Sc)), a misfolded isoform of cellular prion protein.
- The precise role of PrP(Sc) in prion pathogenesis and its correlation with infectivity remain subjects of debate.
Purpose of the Study:
- To investigate the relationship between PrP(Sc) levels, prion infectivity, and disease progression in a mouse model.
- To elucidate the specific roles of different PrP(Sc) aggregate sizes in prion disease.
Main Methods:
- A time-course study was performed on prion-affected mice.
- Brain homogenates underwent centrifugation (20,000 ×g) to separate PrP(Sc) aggregates.
- Mice were inoculated with either crude homogenate or supernatant containing smaller PrP(Sc) particles.
Main Results:
- Prion infectivity did not directly correlate with the total amount of PrP(Sc) in the brain.
- Supernatant, containing less PrP(Sc), exhibited similar infectivity to crude homogenate but longer incubation periods.
- Larger PrP(Sc) aggregates were found in the pellet, while smaller, fine PrP(Sc) were present in the supernatant.
Conclusions:
- A small population of fine PrP(Sc) may be primarily responsible for prion infectivity.
- Larger, aggregated forms of PrP(Sc) might play a role in determining the duration of prion disease.
