Molecular Behaviors of “CH1641-Like” Sheep Scrapie Isolates in Ovine Transgenic Mice (TgOvPrP4)

Abstract

Molecular analyses of the protease-resistant prion protein (PrPres) from a few natural scrapie isolates showed by Western blotting some partial similarities with those observed in experimental ovine bovine spongiform encephalopathy (BSE). They showed a low apparent molecular mass of unglycosylated PrPres, although diglycosylated PrPres was less abundant than in ovine BSE. The prototype of such cases is the CH1641 experimental scrapie isolate. We analyzed PrPres molecular features from three French natural “CH1641-like” isolates, in comparison with CH1641 and BSE, after transmission of the disease in ovine transgenic mice (TgOvPrP4). One of these isolates (TR316211) behaved like the CH1641 isolate, with PrPres features in mice similar to those in the sheep brain. From two other isolates (O100 and O104), two distinct PrPres phenotypes were identified in mouse brains, with either high (h-type) or low (l-type) apparent molecular masses of unglycosylated PrPres, the latter being similar to that observed with CH1641, TR316211, or BSE. Both phenotypes could be found in variable proportions in the brains of the individual mice. In contrast with BSE, l-type PrPres from “CH1641-like” isolates showed lower levels of diglycosylated PrPres. From one of these cases (O104), a second passage in mice was performed for two mice with distinct PrPres profiles. This showed a partial selection of the l-type phenotype in mice infected with a mouse brain with predominant l-type PrPres, and it was accompanied by a significant increase in the proportions of the diglycosylated band. These results are discussed in relation to the diversity of scrapie and BSE strains.

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

“…Differences in WB glycoprofiles, antibody reactivity and degree of resistance to proteinase K digestion have been reported to provide discrimination between classical scrapie, experimental ovine BSE, CH1641 and CH1641-like isolates (Stack et al, 2002;Baron & Biacabe, 2007;Langeveld & Jeffrey, unpublished observations), and Nor98/atypical scrapie Benestad et al, 2008). In addition, differences in pathological phenotypes, both in terms of vacuolar and, particularly, PrP d profiles in the brain, have been observed between cases of TSEs, either natural or experimentally induced, in the natural sheep host.…”

Prion agent diversity and species barrier

“…Some exhibited features similar to CH1641 (∼19 kDa PrP res signature). In other, ∼21 kDa forms predominated and there was a mixture of both [6,9]. It is noteworthy that similar strain typing studies are currently being pursued with the newly developed bank vole model ([140] What is the state of knowledge about the cross-species potential of sheep scrapie, besides rodents?…”

The bank vole (Myodes glareolus) as a sensitive bioassay for sheep scrapie

“…These mouse models were shown to abrogate the species barrier when challenged with scrapie, and allowed the transmission of scrapie isolates with different PrP genotypes, irrespective of the homology with the transgene used in the mouse, in that both ARQ and VRQ transgenic models allowed the transmission of scrapie isolates from either ARQ-or VRQ-bearing sheep (Vilotte et al, 2001;Beringue et al, 2006;Baron & Biacabe, 2007). The efficiency of transmission, however, was reported to be highly variable depending on the isolate, with incubation times ranging from less than 100 days for a VRQ/VRQ isolate (Vilotte et al, 2001) up to 2 years for some ARQ/ ARQ isolates (Beringue et al, 2006).…”