TABLE 2.

Oral immunization with PspA-expressing Salmonella strains protects BALB/c mice against intraperitoneal challenge with capsular type 3 S. pneumoniae WU2

Vaccine strainaPspA expressionbNo. of challenged miceNo. of days to death (no. of mice)cProtection rate (%)
BSGNA102 (9), 3 (1)0
χ9241(pYA3493)132 (10), 3 (3)0
χ9277(pYA3493)132 (11), 3 (2)0
χ9241(pYA3634)+132 (6), 3 (1), 4 (3), >15 (3)23
χ9277(pYA3634)+132 (3), 3 (1), 4 (2), 5 (1), >15 (6)46d
  • 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. The LD50 of WU2 in nonimmunized BALB/c mice is 2 × 102 (data not shown).

  • d Compared with χ9241(pYA3634)-immunized mice, the P value was 0.06; compared with χ9277(PYA3493)-immunized mice, the P value was <0.01.