Table 4. Tg338 mice intracerebral inoculation with VRQ/VRQ sheep white blood cells homogenates.

Donor	Specimen	Total inoculated volume (equivalent whole blood)	Number of positive mice	ID50 per mL of whole blood
D1	WBC neat	9.8 mL	6/6
	WBC 1/10	980 µL	4/6	19.4 (5.5–67.8)
	WBC 1/100	98 µL	2/6
	WBC 1/1000	9.8 µL	0/6
D2	WBC neat	9.6 mL	6/6
	WBC 1/10	960 µL	4/6	13.5 (4.3–41.6)
	WBC 1/100	96 µL	1/6
	WBC 1/1000	9.6 µL	0/6
D3	WBC neat	9,2 mL	6/6
	WBC 1/10	920 µL	3/6	6.5 (2.5–16.7)
	WBC 1/100	92 µL	0/6
C1	WBC neat	9.7 mL	0/6	-

Blood was collected from three TSE free VRQ/VRQ donor sheep that had been orally challenged with PG127 scrapie (D1, D2, D3) and one TSE free VRQ/VRQ control sheep (C1). The date of collection from the infected animals was 210 days post inoculation. Donor sheep developed clinical signs within two to five weeks following blood collection. They were euthanized at 227 days, 256 days, 221 days respectively White blood cells (WBC) were prepared from whole blood and homogenised in 5% glucose solution. Successive 1/10 dilutions of WBC homogenates were inoculated intra-cerebrally to tg338 mice (n = 6). The equivalent volume of whole blood inoculated in mice is indicated. Mice were euthanized when they showed clinical signs of infection or after 250 dpi. Mice were considered infected when abnormal PrP depositions were detected in brain. Infectious titer was estimated by the Spearman-Karber method [19]. Infectious titer is expressed as number of ID₅₀ per mL of whole blood. For each samples, the most likely value and (in parentheses) the lower and upper value of the 95% confidence interval are reported.