Molecular analysis of Irish sheep scrapie cases

Different strains of transmissible spongiform encephalopathies in humans and rodent models are associated with the accumulation of PrP(Sc) of distinct molecular characteristics. These characteristics include glycosylation profiles, fragment sizes and long-term resistance of PrP(Sc) to proteinase K. The first objective of this study was to determine the applicability of these criteria to characterize and differentiate sheep scrapie PrP(Sc) and bovine spongiform encephalopathy (BSE) PrP(Sc). PrP(Sc) in sheep scrapie samples from Ireland had clearly distinct molecular characteristics to PrP(Sc) in cattle BSE samples using a monoclonal antibody (MAb P4) directed to position 89-104 of ovine PrP using either brain homogenates or semi-purified scrapie-associated fibrils. Similar glycoprofiles were found when analysing scrapie PrP(Sc) in six different CNS regions (thoracic spinal cord, thalamus, basal ganglia, mediobasal hypothalamus, medulla oblongata and cortex). While the long-term resistance results using a different monoclonal antibody (raised to ruminant PrP positions 145-163; MAb L42) were similar to the results obtained with MAb P4, different glycotyping results were obtained. Given the variation in glycosylation patterns using different antibodies, we conclude that standardization of methodology and antibodies is crucial to the applicability of molecular analysis of ruminant BSE and scrapie samples.