TABLE 4.
Antibody production and survival from anthrax spore challenge after booster immunization with 1 μg of PAa
| Day postboosting | % survivalb (no. of live animals/total) | Time to death for each animal (MTD for group) | Anti-PA Ab titerc (GMT ± SD) | Neutralizing Ab titerc (GMT ± SD) |
|---|---|---|---|---|
| 0 | 0 (0/12) | 2, 2, 3, 3, 2, 3, 3, 3, 2, 2, 3, 2 (2.5) | 25 ± 1 | <50 ± 1 |
| 2 | 29 (2/7) | 4, 4, 4, 3, 4 (3.75) | 54 ± 1 | <50 ± 1 |
| 4 | 33 (3/9) | 3, 3, 4, 3, 5, 4 (3.75) | 50 ± 1 | <50 ± 1 |
| 6 | 65 (11/17) | 4, 5, 6, 7, 3, 4 (4.8) | 171 ± 5.2 | 93 ± 6.6 |
| 8 | 90 (9/10) | 5 | 617 ± 3.3 | 259 ± 5.0 |
| 12 | 100 (10/10) | 1,467 ± 3.0 | 951 ± 3.4 |
a
Three months after the primary immunization with 1 μg of PA, guinea pigs were boosted with 1 μg of PA vaccine on days 12, 8, 6, 4, 2, and 0 (see text).
b
At day zero, animals from all groups were challenged with 40 LD50 of B. anthracis Vollum spores. A control group of 10 unimmunized animals which received the same challenge died, with a MTD of 2.5 days.
c
Parallel groups (each with 10 immunized guinea pigs) were used for Ab titer determination.