PRNP and scrapie: In this study, we used two of such models, the TgShp XI line (expressing ovine ARQ PrPC)41 and the Tg338 line (expressing ovine VRQ PrPC)42 to study the variability of prion strains and substrains present in the tissues of ten naturally scrapie-infected sheep coming from different outbreaks of the disease within the Spain-France-Andorra transboundary territory.