Lesion Profiling at Primary Isolation in RIII Mice is Insufficient in Distinguishing BSE from Classical Scrapie

Abstract

Primary isolation of bovine spongiform encephalopathy (BSE) in RIII mice generates a lesion profile believed to be reproducible and distinct from that produced by classical scrapie. This profile, which is characterized by peaks at gray matter areas 1, 4 and 7 (dorsal medulla, hypothalamus and septal nuclei), is used to diagnose BSE on primary isolation. The aim of this study was to investigate whether the BSE agent could be present in sheep diagnosed with classical scrapie, using lesion profiles in RIII mice as a discriminatory method. Sixty-two positive scrapie field cases were collected from individual farms between 1996 and 1999 and bioassayed in RIII mice. Fifty-five of these isolates transmitted successfully to at least one mouse. Of the 31 that produced adequate data to allow lesion profile analysis, 10 showed a consistent profile with peaks at brain areas 1, 4 and 7. All inocula for this subgroup were derived from sheep of genotype ARQ/ARQ. While the 1-4-7-scrapie profile exhibited similarities to BSE in RIII mice at primary isolation, it was distinguishable based on histopathology, immunohistochemistry and cluster analysis. We conclude that caution should be taken to distinguish this profile from BSE and that additional parameters should be considered to reach a final diagnosis.

Variability in disease phenotypes within a single PRNP genotype suggests the existence of multiple natural sheep scrapie strains within Europe

“…To explain strain diversity of prions the prion-only hypothesis postulates that, in the absence of a nucleic acid, the conformation of the abnormally folded, infectious form of the prion protein (PrP sc ) codes for strainspecific information (Wille et al, 2002). Following inoculation and serial passage of different sheep scrapie isolates, around 20 scrapie strains (Bruce, 2003) have been isolated and characterized by their relative incubation periods and pattern of brain vacuolation in different inbred lines of mice (Fraser, 1976), and more recently by the immunohistochemical (IHC) pattern of disease-associated PrP (PrP d ) accumulation in the brain (Beck et al, 2010). However, the significance of mouse-adapted scrapie strains remains obscure, since the disease phenotype arising from the In 2006, a working group was established under the auspices of the Network of Excellence Neuroprion with the aim of standardizing criteria and methods for the definition and characterization of sheep scrapie strains in the natural host.…”

Highly Sensitive Detection of Small Ruminant Bovine Spongiform Encephalopathy within Transmissible Spongiform Encephalopathy Mixes by Serial Protein Misfolding Cyclic Amplification

“…1A), but densitometry of these lanes to generate an SHa31/P4 ratio suggested that this method distinguished only the samples containing up to 80% BSE agent from scrapie agent (data not presented). In addition to dual-antibody staining, measurement of the glycoform ratios of the monoglycan and diglycan PrP Sc species can also be used to discriminate prion strains (19,20). Densitometry of the Western blot signals for the monoglycan and diglycan PrP Sc species within brain mixes provided data that were plotted on a scatter plot, which demonstrated that isolates of BSE and scrapie were clearly differentiated from each other (Fig.…”

Scientific Opinion on a request for a review of a scientific publication concerning the zoonotic potential of ovine scrapie prions

“…However, the lack of susceptibility of conventional mouse models to most of the sCJD isolates (Bruce et al, 1997;Hill et al, 1997) and to several scrapie isolates (Bruce et al, 1997;Beck et al, 2010b), has limited the usefulness of this approach for investigating the potential similarities of small ruminant and human TSE agents.…”