Classical scrapie and Atypical/Nor98 scrapie isolates endpoint titration and infectious titre in ovine PrP transgenic mice (tg338).

Incubation periods are expressed in days (mean +/−SD) except in cases where less than 3 animals were positive (*) for which individual incubation periods are presented. Each mouse received 20 µl intracerebrally. The Langlade scrapie isolate homogenate (12.5% weight/volume) was prepared with posterior brainstem from case 10 (Figure 3 and Table 2). These data were already used in a previous publication [32]. The PG127 isolate homogenate (10% weight/volume) was prepared using posterior brainstem from case 13 (Figure 3 and Table 2). ND: not done.For the 5 Atypical/Nor98 cases a 10% weight/volume homogenate was used. Case 1: cerebral cortex. Case 8: cerebellum. Case 9: cerebral cortex. Case 14 cerebellum. Case 15 cerebellum (Figure 3, supplemental Figure S2 and Table 1). Cases 14 and 15 are Atypical/Nor98 field cases independent from those presented in Tables 1 and 2 and were titrated (10% weight/volume homogenate) in different premises than the other isolates. Infectious titre (number of ID50 IC in tg338 per gram of tissues) were determined from this endpoint titration using the Spearman-Karber's approach (for example see Figure 4A, 4B).