Table 3.
Titration of scrapie infectivity in spleens of Tg94/IRF mice inoculated i.p.
| Time after i.p. inoculation, weeks | Days to disease in indicator mice (n/n0) at log dilution*
|
Titer† | |||||
|---|---|---|---|---|---|---|---|
| 0 | −1 | −2 | −3 | −4 | −5 | ||
| 2 | 73 ± 1 (4/4) | — (0/4) | ND | ND | ND | ND | 2 |
| 4 | ND | 79 ± 5 (4/4) | 84 ± 6 (2/2) | 104 ± 2 (3/4) | 121 ± 4 (3/4) | — (0/4) | 6 |
| 8 | ND | 78 ± 4 (4/4) | ND | 103 ± 13 (4/4) | 110 (1/4) | 118 (1/4) | 5 |
| 12 | ND | 71 ± 0 (4/4) | ND | 94 ± 7 (4/4) | 111 ± 11 (4/4) | — (0/4) | 6 |
Homozygous Tg94/IRF mice were inoculated i.p. with 3.5 log LD50 i.c. units of RML prions. At the times indicated, mice were killed and the titer in the spleen was determined by endpoint titration in Tg20 mice. The numbers in the table indicate days elapsed to appearance of symptoms and the fraction (n/n0) of mice falling sick. ND, not done.
*
Serial 10-fold dilutions of 10% spleen homogenates were prepared in PBS/5% BSA and 30 μl was inoculated i.c. into Tg20 mice.
†
log LD50 units/ml 10% homogenate. Calculated by multiplying the LD50 units at the endpoint dilution with 33× dilution factor.