Table 2.

Prion titers in spleens of transgenic and control mice

Mouse line	Weeks after inoculation	Indicator mice succumbing to scrapie (unrelated causes)*	Days to terminal disease	Titer‡
Prnp+/+	2	4/4	74  ± 2	6.2
	4	4/4	73  ± 2	6.3
	8	4/4	66  ± 1	7.1
Prnp+/0	2	8/8	76  ± 3	6.0
	4	8/8	75  ± 2	6.1
	8	7 (1)/8	75  ± 2	6.1
Prnp0/0	2	1/8	129, >200	<1.5
	4	0/8	>200	<1.5
	8	0/8	>200	<1.5
TgN306 hemizygous	2	0/4	>200	<1.5
	4	0/4	>200	<1.5
	8	0/4	>200	<1.5
TgN306 homozygous	2	0 (1)/8	>200	<1.5
	4	0/8	>200	<1.5
	8	0/8	>200	<1.5
TgN431 hemizygous	2	6 (2)/8†	99  ± 9	2.7§
	4	1/8	121, >200	<1.5
	8	1/8	185, >200	<1.5

^*Tissue homogenates pooled from two animals were transmitted to four indicator mice. 

^† Individual spleen homogenates of TgN431 mice were transmitted to four indicator mice. 

^‡ Wherever all indicator animals of a group contracted scrapie, titers [logarithm ID₅₀ units/10% (vol/vol) homogenate] were calculated by the incubation time method (30) by using the relation y = 14.37 − 0.11x, where y is the ID₅₀ and x is the incubation time (in days) to terminal disease. 

^§ Titers in spleens of TgN431 mice were calculated by using the relation y = 11.45 − 0.088x.