It has previously been reported that disease-associated
prion protein (
PrP(d)) derived from natural
scrapie and from sheep infected experimentally with
bovine spongiform encephalopathy (BSE) differed in respect of their immunohistochemical and immunoblotting properties. For BSE, however, these initial observations were restricted to orally challenged sheep of the ARQ/ARQ PrP genotype. Here, extended examinations were performed on 28 sheep that developed neurological signs after BSE experimental
infection by one of three routes. Intracerebrally infected ARQ/ARQ sheep showed more widespread and abundant accumulations of
PrP(d) in tissues of the lymphoreticular system (LRS) than VRQ/VRQ animals, whereas no peripheral
PrP(d) was detected in ARR/ARR sheep. The intensity and dissemination of
PrP(d) accumulation in LRS tissues were less than those found previously in orally dosed sheep. AHQ/AHQ sheep challenged orally and ARQ/AHQ and ARQ/ARQ animals infected intravenously showed similar LRS-tissue
PrP(d) distributions and levels to those of ARQ/ARQ sheep infected intracerebrally. The patterns of intra- and extracellular immunoreactivity to different PrP
antibodies in brain and LRS tissues and the immunoblotting characteristics of
PrP(res) from brain samples remained constant, irrespective of the route of inoculation and the PrP genotype, and were the same as described previously for ARQ/ARQ sheep dosed orally with BSE. These results suggest that the intracellular truncation of BSE
PrP(d) and the
proteinase K cleavage site of BSE
PrP(res) are not altered by PrP genotype or by route of inoculation and that, therefore, screening tests based on these properties can be applied to identify potential sheep BSE cases occurring naturally.