Atypical Scrapie Isolates Involve a Uniform Prion Species with a Complex Molecular Signature

Abstract

The pathobiology of atypical scrapie, a prion disease affecting sheep and goats, is still poorly understood. In a previous study, we demonstrated that atypical scrapie affecting small ruminants in Switzerland differs in the neuroanatomical distribution of the pathological prion protein (PrPd). To investigate whether these differences depend on host-related vs. pathogen-related factors, we transmitted atypical scrapie to transgenic mice over-expressing the ovine prion protein (tg338). The clinical, neuropathological, and molecular phenotype of tg338 mice is similar between mice carrying the Swiss atypical scrapie isolates and the Nor98, an atypical scrapie isolate from Norway. Together with published data, our results suggest that atypical scrapie is caused by a uniform type of prion, and that the observed phenotypic differences in small ruminants are likely host-dependant. Strikingly, by using a refined SDS-PAGE technique, we established that the prominent proteinase K-resistant prion protein fragment in atypical scrapie consists of two separate, unglycosylated peptides with molecular masses of roughly 5 and 8 kDa. These findings show similarities to those for other prion diseases in animals and humans, and lay the groundwork for future comparative research.

Small Ruminant Nor98 Prions Share Biochemical Features with Human Gerstmann-Sträussler-Scheinker Disease and Variably Protease-Sensitive Prionopathy

“…In line with the finding that a single prion strain has been isolated from Nor98 cases [47], [53], [76] and with previous observations by CSSA [58], we found homogenous biochemical properties by PrP res typing of several Nor98 isolates, irrespectively from the species and the PrP genotype. In the present and previous studies [54], [55] using harsh PK conditions, the biochemical signature of Nor98 was a strongly PK resistant PrP res with ragged N and C termini, at variance with the findings obtained with mild PK protocols [51].…”

“…The most distinguishing biochemical feature of Nor98 was a low MW PrP res fragment [36], although studies which used a mild PK protocol also described variable amounts of higher MW, partially glycosylated PrP res fragments [52], [53], [57].…”

Strain Typing of Classical Scrapie by Transgenic Mouse Bioassay Using Protein Misfolding Cyclic Amplification to Replace Primary Passage

“…It is possible that TSEs that reportedly comprise of a single agent, such as bovine spongiform encephalopathy [20] or atypical scrapie [33] may be easier to faithfully replicate via in-vitro amplification methods. TSE strains are known to exist as numerous distinct disease entities, more than one of which can co-exist in a single host [9], [10], [24], [34].…”

Transmission of atypical scrapie to homozygous ARQ sheep

“…Atypical scrapie has been experimentally transmitted to homozygous AHQ sheep by intracerebral [45, 46] and peroral challenge [47], and by the intracerebral route to mice of the ovinized transgenic lines tg338, which overexpresses VRQ PrP [14, 15, 23], and TgOvPrP4, which expresses the AL 141 RQ form [1]. In Japan, the classical scrapie-susceptible ARQ/ARQ and ARQ/VRQ PRNP genotypes predominate among Suffolk sheep [33].…”