Table 2.

Infectivity bioassay of organs from RML-inoculated mice

Donor*	Time p.i., days	Organ†	Death, days	n/nt‡	Titer§
Prnp+/+	14	Brain	>300	0/4
	14	Spleen	163 ± 4	4/4	7
	14	Thymus	200 ± 24	4/4	3.5
	14	Liver	250	1/4	≈1
	180	Brain	150 ± 4	4/4	8
	180	Spleen	168 ± 5	4/4	6.5
	180	Thymus	189 ± 23	4/4	4.5
	180	Liver	>300	0/4
Prnp0/0	14	Brain	>300	0/4
	14	Spleen	>300	0/3¶
	14	Thymus	295	1/4	≈1
	14	Liver	247 ± 52	2/4	≈1.5
	180	Brain	>300	0/4
	180	Spleen	>300	0/4
	180	Thymus	>300	0/4
	180	Liver	240	1/4	≈1
	365	Brain	>300	0/4
	365	Spleen	>300	0/4
	365	Thymus	>300	0/3¶
	365	Liver	>300	0/3¶
Tg33/lck (hemi)	14	Brain	>300	0/4
	14	Spleen	195 ± 41	2/4	≈1.5
	14	Thymus	189	1/4	≈1
	180	Brain	>300	0/4
	180	Spleen	>300	0/4
	180	Thymus	>300	0/3¶
	365	Brain	>300	0/4
	365	Spleen	222	1/4	≈1
	365	Thymus	>300	0/4
Tg01/alb (hemi)	14	Brain	>300	0/4
	14	Spleen	>300	0/4
	14	Liver	>300	0/4
	180	Brain	>300	0/4
	180	Spleen	>300	0/4
	180	Liver	>300	0/4
	365	Brain	>300	0/4
	365	Spleen	>300	0/4
	365	Liver	>300	0/4
Tg94/IRF (hemi)	14	Brain	>300	0/4
	14	Spleen	163 ± 12	4/4	7
	180	Brain	>300	0/4
	180	Spleen	160 ± 6	4/4	7
	365	Brain‖	66 ± 2	4/4	7
	365	Spleen‖	86 ± 5	4/4	5
	365	Thymus‖	81 ± 8	4/4	5.5

^*hemi, hemizygous for the transgene. 

^†Ten percent organ homogenates in 0.32 M sucrose were diluted 10-fold in PBS/5% BSA and 30 μl of the 1% homogenate was inoculated i.c. into CD-1 mice. 

^‡Number of mice with scrapie/total number of mice inoculated. 

^§Infectivity levels (log LD₅₀/ml 10% homogenate) were determined by the incubation time method using standard curves for CD-1 (1) or Tg20 (15) mice. Limit of detection: ≈1 log LD₅₀/ml 10% homogenate. 

^¶One mouse died of intercurrent disease. 

^‖Assayed in Tg20 mice.