TABLE 2.
Oral immunization with rPspA-expressing S. enterica serovar Typhimurium χ8501(pYA3494) vaccine protects BALB/c mice against challenge with virulent S. pneumoniae strain WU2
| Vaccinea | rPspA expressionb | Protectionc (% alive) | Days to death |
|---|---|---|---|
| 5, 5 | |||
| χ8501(pYA3494) | + | 60* | |
| >21, >21, >21 | |||
| χ8501(pYA3493) | − | 0 | 1, 2, 2, 3, 3 |
| None (unimmunized) | NA | 0 | 1, 2, 2, 2, 3 |
a
Mice were orally immunized a total of two times at 10-week intervals with ∼109 CFU of indicated vaccine strain per dose.
b
+, rPspA expressed; −, rPspA not expressed; NA, not applicable.
c
Five weeks after the last immunization, mice (five mice per group) were challenged intraperitoneally with approximately 4.8 × 103 CFU of virulent S. pneumoniae WU2. The LD50 of WU2 by intraperitoneal infection in unimmunized BALB/c mice was <102 (data not shown). Mortality was monitored for 3 weeks after pneumococcal challenge. Significance was determined by chi-square analysis. ∗, P < 0.05.