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Updated: May 13, 2026
Procedures for Identifying Infectious Prions After Passage Through the Digestive System of an Avian Species
Published on: November 6, 2013
Strain typing of classical scrapie by transgenic mouse bioassay using protein misfolding cyclic amplification to
Katy E Beck1, Leigh Thorne, Richard Lockey
1Transmissible Spongiform Encephalopathy Department, Animal Health and Veterinary Laboratories Agency, Addlestone, Surrey, United Kingdom.
Abstract:
According to traditional murine bioassay methodology, prions must be serially passaged within a new host before a stable phenotype, and therefore a strain, can be assigned. Prions often transmit with difficulty from one species to another; a property termed the transmission barrier. Transgenic mouse lines that over express prion protein (PrP) genes of different species can circumvent the transmission barrier but serial passages may still be required, particularly if unknown strains are encountered. Here we sought to investigate whether protein misfolding cyclic amplification (PMCA), an in-vitro method of PrP(Sc) replication, could be used to replace serial passage of VRQ/VRQ classical scrapie isolates undergoing strain typing in ovine transgenic tg338 mice. Two classical scrapie field isolates that do not readily transmit to wild-type mice underwent bioassay in tg338 mice pre- and post- PMCA and the phenotype of disease in inoculated mice was compared. For one of the sources investigated, the PMCA product gave rise to the same disease phenotypes in tg338 mice as traditional bioassay, as indicated by lesion profile, IHC analysis and Western blot, whilst the second source produced phenotypic characteristics which were not identical with those that arose through traditional bioassay. These data show that differences in the efficiency of PMCA as a strain-typing tool may vary between ovine classical scrapie isolates and therefore suggest that the ability of PMCA to replace serial passage of classical scrapie in tg338 mice may depend on the strain present in the initial source.
Insights
Protein misfolding cyclic amplification (PMCA) shows promise for prion strain typing, but its effectiveness varies. Further research is needed to determine if PMCA can fully replace traditional prion bioassays in specific cases.
Area of Science:
- Neuroscience
- Molecular Biology
- Veterinary Pathology
Background:
- Prion strain typing traditionally requires serial passage in vivo, a lengthy process.
- The transmission barrier complicates interspecies prion disease studies.
- Transgenic mouse models can overcome some transmission barriers but may still need serial passages.
Purpose of the Study:
- To evaluate if protein misfolding cyclic amplification (PMCA) can replace serial passage for prion strain typing.
- To compare PMCA-derived prion phenotypes with traditional bioassay results in ovine transgenic mice.
Main Methods:
- Two classical scrapie isolates were subjected to PMCA.
- Prions were bioassayed in ovine transgenic tg338 mice before and after PMCA.
- Disease phenotypes were analyzed using lesion profiles, immunohistochemistry (IHC), and Western blot.
Main Results:
- PMCA successfully replicated prions from ovine scrapie isolates.
- For one isolate, PMCA-generated prions produced identical disease phenotypes to traditional bioassay in tg338 mice.
- The second isolate yielded different phenotypic characteristics after PMCA compared to traditional bioassay.
Conclusions:
- PMCA's efficiency as a prion strain-typing tool can vary depending on the specific ovine classical scrapie isolate.
- The utility of PMCA in replacing serial passage for classical scrapie strain typing in tg338 mice may be strain-dependent.
