Table 1.

Analysis of engrafted and control mice after intracerebral and intraocular inoculation

Genotype		Inoculum	Site	Time of analysis, days after inoculation	Scrapie pathology
Host	Graft
Prnpo/o	tg20	RML	i.c.	222–467	17/17
Prnpo/o	wt	RML	i.c.	147–245	3/3
Prnpo/o	tg20	RML	i.o.	147–293	0/5
Prnpo/o	wt	RML	i.o.	238	0/2
Prnpo/o	tg20	Mock- or not inoculated	i.c.	250–473	0/20
Prnpo/o	tg20	Mock- or not inoculated	i.o.	266, 295	0/2
tg20	No graft	RML	i.c.	62–65	4/4
tg20	No graft	RML	i.o.	74,112	2/2
wt	tg20	RML	i.c.	104–148	10/10
wt	tg20	RML	i.o.	187–224	3/3*
tg33	tg20	RML	i.c.	130–218	5/5
tg33	tg20	RML	i.o.	130–218	0/5

Mice were engrafted and inoculated as described in the text. No Prnp^o/o animal inoculated intraocularly and no animal either inoculated with mock inoculum or left untreated developed spongiosis and gliosis (diagnosed by histological and immunohistochemical examination of paraffin sections) or showed accumulation of proteinase-resistant protein within the graft, as determined by histoblot analysis (19, 25). The infectious titer of the graft of one intraocularly inoculated animal was determined by injecting 20 μl of a 10% dilution prepared as described (19) intracerebrally into 2 tg20 indicator mice; no clinical or histopathological signs of scrapie were found after 186 days (the incubation time at end-point dilution is about 110 days; ref. 20). i.c., Intracerebral; i.o., intraocular; wt, wild type. 

^*One animal analyzed 104 days after intraocular inoculation did not show graft pathology.