Preclinical test for prion diseases.
Tonsillar samples were taken from ten 9.5- to 10-month-old lambs, born and maintained on a farm infected with scrapie. None of the sheep showed clinical signs of the disease. However, extensive PrPSc (an altered protein associated with prion encephalopathies) immunostaining was found in these biopsies from 6 susceptible sheep with the genotype PrPVQ/VQ. PrPSc was not detected in the other sheep which were of the resistant genotype PrPVQ/AR. It is concluded that screening tonsillar tissue for PrPSc by immunohistochemistry offers a potential method of preclinical diagnosis of scrapie in sheep.