Table 1. PrP^res detection in Protein Misfolding Cyclic Amplification (PMCA) reactions seeded with white blood cells from ARQ/ARQ sheep orally inoculated with BSE agent, collected at different time points of the incubation period.

	0 mpi				2 mpi				6 mpi				12 mpi				16 mpi				20 mpi
	R2	R3	R4	R5	R2	R3	R4	R5	R2	R3	R4	R5	R2	R3	R4	R5	R2	R3	R4	R5	R2	R3	R4	R5
Sheep 1	-	-	-	-	-	-	-	-	-	-	-	-	-	2	4	4	3	4	4	4	4	4	4	4
Sheep 2	-	-	-	-	-	-	-	-	2	3	4	4	2	4	4	4	3	4	4	4	4	4	4	4
Sheep 3	-	-	-	-	-	-	-	-	-	2	4	4	1	4	4	4	4	4	4	4	4	4	4	4
Sheep 4	-	-	-	-	-	-	-	-	-	-	-	-	-	3	4	4	4	4	4	4	4	4	4	4

Four TSE free ARQ/ARQ sheep were orally challenged (before the age of 6 months) with 5 g of brain from BSE affected sheep. Blood was collected in these animals at 0, 2, 6, 12, 16 and 20 (clinical onset) months post inoculation (mpi). White blood cells (WBC) were obtained by osmotic lysis of the red blood cells. WBCs were then homogenized in PMCA buffer and homogenates were used to seed PMCA reactions in which the brain of transgenic mice that expressed the ARQ variant of the ovine PrP was used as substrate. Each sample was used to seed 4 independent reactions (two different runs onto 2 different sonicators). Five successive PMCA amplification rounds (R) were applied. After each amplification round, the number of PrP^res positive replicates (as assessed by Western blot) is indicated in the table. (-) indicated that all 4 replicates were negative.

(mpi): months post inoculation.