TABLE 3.

Oral immunization of BALB/c mice with PspA-expressing Salmonella strains confers protection against S. pneumoniae challenge

Vaccine strainaPspA expressionbNo. of challenged miceNo. of days to death (no. of mice)cProtection rate (%)
BSGNA102 (8), 3 (2)0
χ9373(pYA3493)72 (7)0
χ9402(pYA3493)72 (5), 3 (2)0
χ9373(pYA4088)+152 (7), 3 (1), 4 (2), >15 (5)33
χ9402(pYA4088)+152 (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.