Table 4. Infectivity of RML strain-infected brain homogenates at different times after inoculation, determined by mouse bioassay and SC assay
|
Mouse bioassay |
SC assay |
|||
|
Sample no., days postinoculation |
Dilution |
Sick/ |
Incubation time, days ± SD |
SC units |
|
19, A1 |
10-2 |
4/5 |
97 ± 9 |
26 ± 19 |
|
|
10-3 |
3/5 |
96 ± 7 |
7 ± 6 |
|
19, A3 |
10-2 |
n.d. |
n.d. |
10 ± 8 |
|
|
10-3 |
n.d. |
n.d. |
18 ± 24 |
|
25, B1 |
10-2 |
0/4 |
>140 |
11 ± 4 |
|
|
10-3 |
0/4 |
>140 |
4 ± 3 |
|
|
10-4 |
0/5 |
>140 |
n.d. |
|
25, B3 |
10-2 |
n.d. |
n.d. |
6 ± 3 |
|
|
10-3 |
n.d. |
n.d. |
4 ± 1 |
|
41, C1 |
10-2 |
1/5 |
107 |
11 ± 7 |
|
|
10-3 |
0/4 |
>140 |
7 ± 5 |
|
|
10-4 |
0/5 |
>140 |
5 ± 2 |
|
41, C3 |
10-2 |
0/5 |
>140 |
6 ± 2 |
|
|
10-3 |
0/3 |
>140 |
18 ± 17 |
|
|
10-4 |
0/4 |
>140 |
8 ± 4 |
|
61, D1 |
10-2 |
n.d. |
n.d. |
486 ± 53 |
|
|
10-3 |
5/5 |
73 ± 2 |
381 ± 42 |
|
|
10-4 |
5/5 |
77 ± 6 |
103 ± 21 |
|
|
10-5 |
4/5 |
107 ± 6 |
n.d. |
|
|
10-6 |
4/5 |
91 ± 8 |
n.d. |
|
61, D3 |
10-2 |
n.d |
n.d |
471 ± 71 |
|
|
10-3 |
n.d |
n.d |
553 ± 70 |
|
|
10-4 |
n.d |
n.d |
235 ± 21 |
|
140, E1 |
10-3 |
3/3 |
56 ± 5 |
859 ± 136 |
|
|
10-4 |
n.d |
n.d |
858 ±208 |
|
|
10-5 |
5/5 |
84 ± 2 |
n.d. |
|
|
10-6 |
4/5 |
85 ± 3 |
n.d. |
|
|
10-7 |
4/5 |
103 ± 19 |
n.d. |
|
|
10-8 |
1/5 |
107 |
n.d. |
|
140, E3 |
10-3 |
n.d. |
n.d. |
998 ± 190 |
|
|
10-4 |
n.d |
n.d |
778 ± 91 |
n.d., Not determined. CD1 mice were inoculated i.c. with 30 m l of RML strain I2424 (10-2, ~7.5 ´ 104 LD50 units). After 19, 25, 41, and 61 days, mice were culled; mice inoculated similarly were culled 140 days after infection as positive controls. Brain homogenates were prepared as described in Materials and Methods, and mouse bioassays were performed as described in Table 1. The background values for the SC assay (noninfected N2aPD88 cells) were 9 ± 5 and were not subtracted. Values characteristic for infectious samples are in bold.