Intravenous administration in sheep and intracerebral challenge in tg338 mice of blood derived products prepared from PG127 scrapie infected sheep.

Four scrapie-susceptible VRQ/VRQ sheep (identified as D4, D5, D6 and D7) were orally challenged with 1 g of sheep scrapie strain PG127 infected brain homogenate containing 106.7 IC ID50/g as measured by IC inoculation of tg338 mice Scrapie incubation periods were 226 dpi, 238 dpi, 228 dpi and 242 dpi, respectively. Blood was collected at 217 dpi, i.e few days (D4) to three weeks (D7) before clinical onset. Plasma and white blood cells (WBC) were prepared from 500 mL of whole blood. Half of the WBC preparation from each animal was fixed with paraformaldehyde (PFA 2% final concentration). Whole Blood, plasma and both fresh and fixed WBCs (re-suspended in 5% glucose), each corresponding to 200 mL of whole blood, were administered intravenously to VRQ/VRQ TSE free recipients. In addition, Plasma volume equivalent to 20 mL of whole blood was also intravenously administered to sheep. Recipients were euthanized when symptomatic with scrapie. 450 dpi (or 380 dpi for the 20 mL plasma) recipients that were still alive and apparently healthy were euthanized. Incubation periods in recipients are presented in days post inoculation (dpi). All recipient sheep were tested for the presence of abnormal PrP deposition in brain and various lymphoid tissues by immunohistochemistry.NA: not assessed.