A novel real-time ultrasonic method for prion protein detection using plasminogen as a capture molecule

Changes in the ultrasonic parameters suggested that three processes occurred during the incubation: binding, protein-protein network formation and precipitation and that these processes occurred in a concentration dependent manner. Conversely, when homogenates from normal sheep were similarly examined, no evidence for the occurrence of these processes was found indicating the specificity of the interaction between the plasminogen coated beads and PrPSc.These results indicate firstly, that the plasminogen coated beads binded selectively to PrPSc and secondly, that a HR-US system can discriminate between scrapie affected and non-affected samples and thus has potential as a tool for the rapid diagnosis for prion diseases. This approach has the significant advantage of not requiring a proteinase K pre-digestion step, which is routinely used in current PrPSc detection assays.Prion diseases such as CJD in humans, BSE in cattle and scrapie in sheep are a group of neurodegenerative disorders, which are characterised by the accumulation in the central nervous system of the protease resistant form (PrPSc) of a host-coded membrane glycoprotein (PrPc) [1]. The transformation of PrPc into PrPSc implies a conformational change from a mainly alpha helical form into a beta sheet rich structure [2,3]. This conformational difference is responsible for the distinct physicochemical properties of both isoforms. While PrPc exist as a monomer and it is rapidly degraded by proteinase K (PK), the infectious isoform PrPSc, forms detergent-insoluble aggregates and displays a higher resistance to degradation with PK [4,5].Most currently used diagnostic techniques are based on the immunological detection of PrPSc using antibodies specific to the prion protein. As antibodies used on current validated assays are not able to differentiate between PrPSc and PrPc, these diagnostic procedures rely on the elimination of PrPc by PK digestion, PrPSc remaining due to its PK resistance. However, the use o