TABLE 3.
Ability of anti-NspA MAb AL12 to passively protect infant rats challenged i.p. with different meningococcal B strains
| Experiment no. | Strain (challenge dose per rat in CFU) | MAb pretreatmenta | Dose (μg) per rat | Results of blood culture at 18 h
|
|
|---|---|---|---|---|---|
| No. positive/total | CFU/ml (geometric mean, 103)b | ||||
| 1 | 8047 (2.3 × 103) | Anticapsular | 10 | 2/7 | 0.05 |
| AL12 Anti-NspA | 50 | 0/7 | <0.01 | ||
| AL12 Anti-NspA | 5 | 4/7 | 1.4 | ||
| Irrelevant | 50 | 7/7 | 115 | ||
| PBS-albumin | None | 7/7 | 79 | ||
| 2 | BZ232 (15.0 × 103) | Anticapsular | 50 | 0/5 | <0.01 |
| Anticapsular | 10 | 0/5 | <0.01 | ||
| AL12 Anti-NspA | 50 | 4/5 | 0.2 | ||
| AL12 Anti-NspA | 10 | 4/5 | 0.5 | ||
| Irrelevant | 50 | 5/5 | 11.5 | ||
| PBS-albumin | None | 5/5 | 3.9 | ||
| 3 | M986 (2 × 103) | Anticapsular | 2 | 0/6 | <0.01 |
| AL12 Anti-NspA | 50 | 5/5 | >500 | ||
| AL12 Anti-NspA | 2 | 6/6 | >500 | ||
| Irrelevant | 2 | 5/5 | >500 | ||
In experiments 1 and 2, animals were pretreated with the MAb i.p. at time zero. Two hours later, the animals were challenged i.p. with bacteria. In experiment 3, to increase the sensitivity of the assay, the bacteria and MAb were mixed together immediately before the i.p. challenge. In this experiment, blood was also obtained for culture at 6 h. Results for this time are provided in the text.
For calculation of geometric mean CFU per milliliter, animals with sterile cultures were assigned a value of 10 CFU/ml. The geometric mean CFU per milliliter of animals receiving AL12 were compared to that of the combined group of negative-control animals given irrelevant MAb or PBS-BSA: experiment 1, 50 μg of AL12 versus controls, P < 0.001; 5 μg of AL12 versus controls, P < 0.005; experiment 2, 50 μg of AL12 versus controls, P < 0.01; 10 μg of AL12 versus controls, P < 0.01.