Characteristic parameters of various prion strains in C57BL/6 and <i>Tg</i>a<i>20</i> mice.

+Mice were inoculated with 20 µl of 1% brain homogenate and euthanized when they showed pronounced clinical signs, rather than at terminal stage of disease. The average incubation period for ME7 in C57BL/6 mice is shorter than the 155–160 days described in some other studies [24], [48], [49]. This might be due to variations in the criteria for euthanasia, the number of passages of the strain and/or variations between different C57BL/6 mouse lines. †Because of the very short symptomatic period in Tga20 mice, all mice in a group were killed on the same day. #By endpoint titration in C57BL/6 mice (6 mice per group, 22L and ME7; 5 mice per group, RML) [50]. The inocula were homogenates of brains from terminally sick C57BL/6 mice infected with 22L, ME7 or 301C, or from terminally sick CD1 mice infected with RML.