Oral immunization of BALB/c mice with PspA-expressing Salmonella strains confers protection against S. pneumoniae challenge
| Vaccine straina | PspA expressionb | No. of challenged mice | No. of days to death (no. of mice)c | Protection rate (%) |
|---|---|---|---|---|
| BSG | NA | 10 | 2 (8), 3 (2) | 0 |
| χ9373(pYA3493) | − | 7 | 2 (7) | 0 |
| χ9402(pYA3493) | − | 7 | 2 (5), 3 (2) | 0 |
| χ9373(pYA4088) | + | 15 | 2 (7), 3 (1), 4 (2), >15 (5) | 33 |
| χ9402(pYA4088) | + | 15 | 2 (6), 3 (2), >15 (7) | 47d |
↵a Mice were orally immunized with a single dose of the indicated vaccine strains.
↵b +, PspA expressed; −, PspA not expressed; NA, not applicable.
↵c Eight weeks after the primary oral immunization, mice were challenged in two experiments with approximately 2 × 104 CFU of S. pneumoniae WU2. Both experiments gave similar results, and the data have been pooled for presentation and analysis.
↵d Compared with χ9402(pYA3493)-immunized mice, the P value was <0.05.