TABLE 2.
Serum bactericidal activity of murine antisera raised against rMIP proteinsa
| Delivery vehicle | Protein for immunization | Reciprocal SBA titer (50% endpoint) against: |
|||
|---|---|---|---|---|---|
| MC58 (I) | MC168 (I) | MC90 (II) | MC54 (III) | ||
| Saline solution | N-term His Full rMIP | <4 | <4 | 64 | <4 |
| N-term His Truncated rMIP | <4 | <4 | 64 (16, 64) | 4 | |
| C-term His Full rMIP | <4 | <4 | 64 (32, 64) | <4 | |
| C-term His Truncated rMIP | <4 | <4 | 64 (32, 64) | <4 | |
| N-term His Full rMIP (LP) | 128 (64, 128) | 256 (64, 512) | 256 (128, 256) | 128 (64, 256) | |
| Liposomes | N-Term His Full rMIP | <4 | <4 | 128 | 512 |
| N-term His Truncated rMIP | <4 | <4 | 128 (64, 256) | 512 | |
| C-term His Full rMIP | 128 (64, 256) | 512 | 256 | 256 (256, 512) | |
| C-term His Truncated rMIP | 128 (128, 256) | 256 (128, 256) | 512 (128, 512) | 512 (128, 512) | |
| N-term His Full rMIP (LP) | 256 (256, 512) | 256 (128, 512) | 256 | 256 (128, 256) | |
| Controls | Saline solution only | <4 | <4 | <4 | <4 |
| Liposomes only | <4 | <4 | 64 (32, 64) | <4 | |
| Normal mouse serum | 8 | 8 | 64 (32, 64) | 8 | |
Antisera were tested against the homologous strains expressing type I MIP protein (MC58 and MC168) and against heterologous strains expressing type II (MC90) and type III (MC54) MIP proteins. The titers are expressed as the reciprocal of the highest dilution at which 50% killing was observed, using baby rabbit complement (5%, vol/vol) as an exogenous source. The titer for mice immunized with native LOS-replete MC58 OM was 20,000 (internal positive control). Data are the median values, with the range of values in parentheses, for SBA from between a minimum of 3 and a maximum of 11 independent measurements of bactericidal activity of all pooled serum samples. Single values denote that the SBA titers from the independent experiments were identical. Sera from sham-immunized mice showed no significant bactericidal activity (<4 to 64, depending on the strain tested).