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Science  20 Jul 2001:
Vol. 293, Issue 5529, pp. 395
DOI: 10.1126/science.293.5529.395a

Bovine spongiform encephalopathy (BSE, commonly referred to as “mad cow disease”) is thought to involve the transmission of a pathological conformation of an endogenous prion protein, which exists in cellular (PrPC) and scrapie-inducing (PrPSc) forms. How a single host can harbor multiple strains of this infectious agent is unclear. In the intact animal, this question is complicated by the fact that each strain may manifest itself in a different type of cell and that strain variations then might be intermingled with differential protein processing.

Birkett et al. have described the propagation of strain-specific characteristics within a single scrapie-susceptible cell line. Treatment of a scrapie-infected mouse cell line with the drug pentosan sulfate eliminated traces of the pre-existing PrPSc. Subsequent infection with a second strain of scrapie (with distinct biochemical properties and a different disease incubation time when transmitted to mice) yielded a cell line that exhibited characteristics of the newly introduced scrapie strain, rather than that of the original. This finding begs the question as to precisely how strain specificity can be maintained within a single cell type, but the development of this model system should allow researchers to pose detailed questions about prion strain variation. — SMH

EMBO J.20, 3351 (2001).

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