Abstract
The diversity of goat scrapie strains in Europe has recently been studied using bioassays in a wide collection of rodent models, resulting in the classification of classical scrapie into four different categories. However, the sole use of the first passage does not lead to isolate adaptation and identification of the strains involved and might therefore lead to misclassification of some scrapie isolates. Therefore, this work reports the complete transmission study of a wide collection of goat transmissible spongiform encephalopathy (TSE) isolates by intracranial inoculation in two transgenic mouse lines overexpressing either small ruminant (TgGoat-ARQ) or bovine (TgBov) PrPC. To compare scrapie strains in sheep and goats, sheep scrapie isolates from different European countries were also included in the study. Once the species barrier phenomenon was overcome, an accurate classification of the isolates was attained. Thus, the use of just two rodent models allowed us to fully differentiate at least four different classical scrapie strains in small ruminants and to identify isolates containing mixtures of strains. This work reinforces the idea that classical scrapie in small ruminants is a prion disease caused by multiple different prion strains and not by a single strain, as is the case for epidemic classical bovine spongiform encephalopathy (BSE-C). In addition, the clear dissimilarity between the different scrapie strains and BSE-C does not support the idea that classical scrapie is the origin of epidemic BSE-C.
Highlights
Prion diseases, or transmissible spongiform encephalopathies (TSEs), are a group of fatal neurodegenerative diseases that affect animals and humans
The group includes several disorders with different origins and epidemiology, all of which are molecularly based on the conversion of the host-encoded cellular prion protein (Cellular prion protein (PrPC)) into a disease-associated isoform (PrPSc), which is considered to be the main component of the prion agent [1]. Disease abnormally misfolded prion protein (PrPSc) self-catalyses its formation by recruiting PrPC into aggregates that transform PrPC into PrPSc [2]
Transmission of goat TSE isolates in TgGoat‐ARQ mice As previously observed in the prion field [30] and reported for this subset of goat TSE isolates [44], the efficiency of prion transmission relies on the PrP sequence identity between the donor and host species
Summary
Transmissible spongiform encephalopathies (TSEs), are a group of fatal neurodegenerative diseases that affect animals and humans. TSEs have been reported in animal species in the human food chain, such as small and wild ruminants, Scrapie affecting sheep, goats and mouflons [6] has been circulating in Europe for centuries [7] and is exceptionally well transmitted horizontally within herds due to the accumulation of infectious prions in peripheral tissues and biological fluids [8,9,10,11,12,13,14,15,16,17,18,19] as well as the high persistence of the agent in the environment [20, 21]. As a consequence of the BSE-C epidemic, active surveillance for TSEs in small ruminants was enhanced in Europe This increase in active surveillance resulted in the identification of several different disease phenotypes, which points to the existence of different scrapie prion strains [24,25,26,27,28,29]. The causative strain is biochemically characterized by a low molecular weight internal proteinase-K resistant PrPSc (PrPres) fragment of 8 kDa [32]
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