Transfusion of VRQ/VRQ sheep with blood spiked with decreasing amounts of PG127 infected sheep brain homogenate.

200 mL of whole blood was collected from each of 12 TSE Free VRQ/VRQ cheviot sheep. Whole blood pouches were spiked with decreasing amounts of sheep scrapie strain PG127 brain homogenate containing 106.6 ID50/g as measured by IC inoculation in tg338 mice. Each spiked blood was then transfused back into the sheep of origin. Two sheep were challenged at each dose (indicated as number of ID50 IC in tg338). Sheep were observed until they developed clinical signs or reached 750 days post inoculation when they were euthanized. All recipients were tested for presence of abnormal PrP (PrPSc) deposition in brain and various lymphoid tissues by immunohistochemistry. Results confirmed the clinical diagnosis. Incubation periods in recipients are presented as days post inoculation (dpi).