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Prion protein (PrP) is present at extremely low levels in the blood of animals and its detection is complicated by the poor sensitivity of current standard methodologies. Interesting results have been obtained with recent advanced technologies that are able to detect minute amounts of the pathological PrP (PrPSc), but their efficiency is reduced by various factors present in blood. In this study, we were able to extract cellular PrP (PrPC) from plasma-derived exosomes by a simple, fast method without the use of differential ultracentrifugation and to visualize it by Western blotting, reducing the presence of most plasma proteins. This result confirms that blood is capable of releasing PrP in association with exosomes and could be useful to better study its role in the pathogenesis of transmissible spongiform encephalopathies.

The aim of this study was to analyse the SPRN genes of goats from several scrapie outbreaks in order to detect polymorphisms and to look for association with scrapie occurrence, by an unmatched case-control study. A region of the caprine SPRN gene encompassing the entire ORF and a fragment of the 3'UTR revealed a total of 11 mutations: 10 single-nucleotide polymorphisms and one indel polymorphism. Only two non-synonymous mutations occurring at very low incidence were identified. A significant association with scrapie positivity in the central nervous system was found for an indel polymorphism (602_606insCTCCC) in the 3'UTR. Bioinformatics analyses suggest that this indel may modulate scrapie susceptibility via a microRNA-mediated post-transcriptional mechanism. This is the first study to demonstrate an association between the SPRN gene and goat scrapie. The identified indel may serve as a genetic target other than PRNP to predict disease risk in future genetics-based scrapie-control approaches in goats.

To evaluate further the reactivity of prion-specific monoclonal antibodies containing the 89-112 or 136-158 prion protein (PrP) polypeptides, immunoprecipitations were performed on brain extracts from Italian bovines, sheep and goats with transmissible spongiform encephalopathies. No binding of IgG 89-112 or IgG 136-158 to PrP in normal brain extracts was detected. Conversely, both reagents immunoprecipitated PrP from bovine and bovine amyloidotic spongiform encephalopathies, and from typical and atypical scrapie brain extracts. The immunoprecipitated PrP bands mirrored the Western blot (WB) profile of the different prion strains, indicating universal affinity of two independent PrP regions for disease-associated PrP conformers regardless of species source and strain properties. Immunoprecipitation with motif-grafted antibodies increased the sensitivity of conventional detection methods based on centrifugation followed by WB, which was confirmed by assay of diluted samples using both methods. These reagents or derivative molecules may thus find broad applications in prion detection and research.

An accidental intra- and interspecies transmission of scrapie occurred in Italy in 1997 and 1998 following exposure to a vaccine against Mycoplasma agalactiae. PrP(Sc) in affected sheep and goats, collected from a single flock exposed to vaccination 2 years earlier, was molecularly typed. In five animals with iatrogenic scrapie, a PrP(Sc) type with a 20 kDa core fragment was found in all areas of the brain investigated. In three sheep and one goat, this isoform co-occurred with a fully glycosylated isoform that had a protease-resistant backbone of 17 kDa, whereas in two sheep and four goats, the two PrP(Sc) types were detected in different regions of the brain. In sheep with natural field scrapie, a PrP(Sc) type with physico-chemical properties indistinguishable from the 20 kDa isoform was found. The present results suggest the co-presence of two prion strains in mammary gland and brain homogenates used for vaccination.