PrPSc accumulation in myocytes from sheep incubating natural scrapie

Because variant Creutzfeldt-Jakob disease (vCJD) in humans probably results from consumption of products contaminated with tissue from animals with bovine spongiform encephalopathy, whether infectious prion protein is present in ruminant muscles is a crucial question. Here we show that experimentally and naturally scrapie-affected sheep accumulate the prion protein PrPSc in a myocyte subset. In naturally infected sheep, PrPSc is detectable in muscle several months before clinical disease onset. The relative amounts of PrPSc suggest a 5,000-fold lower infectivity for muscle as compared to brain.