highly significantP < 0.0001
In contrast, tg a 20 +/+;TK+ mice treated with GCV showed a median incubation time of 50 dpi, with a highly significant acceleration of progression compared with PBS-treated tg a 20 +/+;TK+ mice (7 d; P < 0.0001; Fig. 2 A ); under no other conditions were tg a 20 mice reported to develop scrapie so rapidly.