Scrapie agent from different genotypes of sheep show different seeding activity with elk recombinant prion proteins in RT-QuIC

Authors: Hwang, Soyoun; Greenlee, Justin; Vance, Natalie; Nicholson, Eric

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2018
Publication Date: 12/20/2018
Citation: Hwang, S., Greenlee, J.J., Vance, N.M., Nicholson, E.M. 2018. Source genotype influence on cross species transmission of transmissible spongiform encephalopathies evaluated by RT-QuIC. PLoS One. 13(12):e0209106. https://doi.org/10.1371/journal.pone.0209106.
DOI: https://doi.org/10.1371/journal.pone.0209106

Interpretive Summary: The prion protein (PrP) is normal protein that can change its shape into an abnormal structure knowing as PrPSc that is the causative agent of transmissible spongiform encephalopathies, diseases that affect the central nervous system. This conversion of normal PrP to a PrPSc like structure can be conducted in laboratory settings using a misfolding amplification process known as real-time quaking induced conversion (RT-QuIC). RT-QuIC uses recombinant prion protein to detect minute amounts of PrPSc in tissue samples of a diseased host. RT-QuIC can be used for the detection of prions and for strain discrimination in a variety of biological tissues from humans and animals. We evaluated how different genotypes of PrPSc from TSE affected sheep can seed the fibril formation differently in RT-QuIC using the PrP of 2 different sequences normally occurring in elk. We also inoculated transgenic mice expressing elk prion with scrapie from different genotypes of sheep to compare with our RT-QuIC results, and the bioassays support the RT-QuIC results showing significantly shorter incubation period for inoculum from VRQ/VRQ sheep when compared to inoculum from ARQ/ARQ sheep. Therefore, we conclude that genotypic background of both source and recipient can strongly influence susceptibility, thus not only the genotype of the recipient animal but also the genotype of the animal used as a source of the inoculum should be considered in the study of prion transmission.

Technical Abstract: Scrapie is a naturally occurring transmissible spongiform encephalopathy of sheep and goats. This fatal neurodegenerative disease is caused by misfolding of the cellular prion protein to the pathogenic ß-rich conformers (PrPSc) that accumulates into higher order structures in the brain and other tissues. This conversion has been used for in vitro assays including serial protein misfolding amplification and real-time quaking induced conversion (RT-QuIC). RT-QuIC can be used for the detection of prions and for strain discrimination in a variety of biological tissues from humans and animals. In this study, we evaluated how different genotypes of PrPSc from sheep scrapie influence the fibril formation in vitro using RT-QuIC. We found that reaction mixtures seeded with genotype VRQ/VRQ sheep brains have better conversion efficiency with 132M elk substrate compared to reactions seeded with brains from sheep with the ARQ/ARQ genotype no matter which strain of scrapie was used to seed the reactions. We also inoculated transgenic mice expressing M132 elk PRNP (Tg12) with scrapie from different genotypes of sheep to compare with our RT-QuIC results. The bioassays support the data showing a significantly shorter incubation period for inoculum from VRQ/VRQ sheep when compared to inoculum from ARQ/ARQ sheep. Thus, we conclude that the genotype of both source and recipient can strongly influence transmission.