Distribution of abnormal prion protein in a sheep affected with L-type bovine spongiform encephalopathy.

Summary To investigate the topographical distribution and patterns of deposition of immunolabelled abnormal prion protein (PrP Sc ), interspecies transmission of atypical L-type bovine spongiform encephalopathy (BSE) to Cheviot ewes (ARQ/ARQ genotype) was performed. L-type BSE was successfully transmitted via the intracerebral route to a ewe, with an incubation period of 1,562 days. Minimal vacuolar change was detected in the basal ganglia, thalamus and brainstem, and PrP Sc accumulated throughout the brain. The L-type BSE-affected sheep was characterized by conspicuous fine particulate deposits in the neuropil, particulate and/or granular intraneuronal and intraglial deposits, and the absence of PrP Sc plaques or stellate deposits. In addition, immunohistochemical and western blot analyses revealed that PrP Sc accumulation was present in peripheral nervous tissues (including the trigeminal ganglia and dorsal root ganglion) and adrenal glands, but was absent in lymphoid tissues. These results suggest that L-type BSE has distinct and distinguishable characteristics as well as PrP Sc tissue tropism in sheep.