TABLE 3.

Prion infectivity in the mesenteric lymph nodes of mice after oral inoculation of RML 5.0 prions^a

Mice	Diseaseb	Incubationc	Titerd
Wild type, day 375	4/4	91 ± 1	4.3
	4/4	99 ± 2	2.8
Mean			3.5
Wild type, day 525	4/4	63 ± 2	9.4
	4/4	60 ± 1	10.0
Mean			9.7
tga20	4/4	110 ± 10	2.1
	4/4	100 ± 12	2.6
Mean			2.4

^aTwenty-microliter volumes of 1% (wt/vol) mesenteric lymph nodes prepared from orally inoculated tga20 mice that had succumbed to terminal prion disease or wild-type mice euthanized 375 or 525 days after oral inoculation were inoculated by the i.c. route into tga20 mice. Inoculated mice were monitored daily for clinical signs of mouse prion disease. Mice were euthanized at the point of neurological disease and dysfunction.

^bNumber of mice succumbing to terminal disease/number of mice in each group.

^cMean time to terminal disease (in days) ± standard deviation.

^dPrion titers were calculated according to the formula y = −0.184x +9.42, where y is the log₁₀ dilution of stock RML 5.0 infectivity and x is incubation time (in days). Prion titers are given as log₁₀LD₅₀ per gram of tissue.