TABLE 1.
Prion load of spleens in individual FLC-reconstituted mice
| Mice | RML inoculum (log LD50) | Days after inoculation | No. of animals inoculated | Splenic infectivity (log LD50) | No. of indicator animals succumbing to scrapie/no. inoculated (mean incubation time ± SD [days]) |
|---|---|---|---|---|---|
| Prnp+/+→Prnpo/o | 6 | 34 | 2 | 5.5, <1.5a | 4/4 (80.8 ± 9.0), 2/8 (133, 135) |
| 60 | 3 | 5.6, 5.0, 4.3 | 4/4 (80.3 ± 4.5), 4/4 (87.5 ± 9.1), 3/3 (95.7 ± 12.2) | ||
| 90 | 3 | NDb | ND | ||
| 200 | 4 | 5.0, 4.9, 4.0, ND | 4/4 (88.8 ± 8.1), 4/4 (89.3 ± 5.9), 4/4 (101.5 ± 9.0), ND | ||
| Prnp+/+→Prnpo/o | 3 | 34 | 3 | <1.5, <1.5, ND | 0/4, 0/3, ND |
| 60 | 3 | <1.5, <1.5, <1.5 | 0/4, 0/3, 0/3 | ||
| 90 | 3 | ND | ND | ||
| 360 | 5 | ND | ND | ||
| Prnpo/o→Prnp+/+ | 6 | 34 | 3 | 7.1, 6.1, ND | 4/4 (65.8 ± 3.5), 4/4 (77.0 ± 3.8), ND |
| 60 | 2 | 6.6, 6.5 | 3/3 (71.0 ± 11.1), 4/4 (72.3 ± 3.0) | ||
| 90 | 2 | 6.6, 6.1 | 4/4 (69.5 ± 7.9), 3/3 (75.3 ± 5.5) | ||
| 200 | 2 | 7.0, 7.2 | 4/4 (64.8 ± 1.5), 4/4 (62.0 ± 2.3) | ||
| Prnpo/o→Prnp+/+ | 3 | 34 | 3 | <1.5, <1.5, <1.5 | 0/4, 0/4, 0/4 |
| 60 | 2 | ND | ND | ||
| 90 | 2 | ND | ND | ||
| 360 | 2 | <1.5, ND | 0/4, ND | ||
| Prnpo/o→Prnpo/o | 6 | 34 | 3 | <1.5, <1.5,a ND | 0/4, 3/4 (155, 163, 178),c ND |
| 60 | 2 | <1.5, <1.5 | 0/4, 0/4 | ||
| 200 | 2 | ND | ND | ||
| Prnpo/o→Prnpo/o | 3 | 360 | 5 | ND | ND |
| Prnp+/+ | 6 | 34 | 2 | 6.5, 5.3 | 4/4 (69.0 ± 2.0), 3/3 (83.0 ± 6.2) |
| 200 | 3 | ND | ND | ||
| Prnp+/+ | 3 | 34 | 2 | 5.8, 5.8 | 3/3 (77.3 ± 5.9), 4/4 (77.3 ± 4.7) |
| 230 | 3 | ND | ND |
a
If one or more animals survived >180 days, the titer was assumed to be close to the detection limit of the bioassay (<1.5).
b
ND, not determined.
c
The development of scrapie disease in these indicator animals is most likely due to residual inoculum of the primary inoculation.