Figure 5.

ELISA measurements of serum IgG and mucosal IgA responses in immunized and control mice (n = 13 per group) and protection against S. pneumoniae challenge. (A) Total serum IgG specific for PspA, No immune responses were detected to PspA in mice immunized with the S. Typhimurium vaccine strain with the vector control plasmid, χ9241(pYA3493) (reciprocal titer <1:100); (B) anti-S. Typhimurium LPS serum IgG; (C) ratio of reciprocal anti-PspA IgG2a/IgG1 titers; (D) mucosal anti-PspA IgA. No anti-PspA IgG was detected in serum from mice immunized with the S. Typhimurium vaccine strain with the vector control plasmid, χ9241(pYA3493) (reciprocal titer <1:50). The data represent reciprocal antibody titers (mean ± SEM) in pooled sera or vaginal washes from mice orally immunized with attenuated Salmonella carrying either pYA4088 (PspA) or pYA3493 (control) and boosted 5 weeks later. * P < 0.01; ** P < 0.001 compared to mice immunized with χ9241(pYA4088). (E) Protection in orally immunized BALB/c mice challenged i.p. with 4×10⁴ CFU of S. pneumoniae WU2–9 weeks after the first immunization. All vaccine groups were significantly different from the χ9241(pYA3493) control (P < 0.01), P values were determined using the log-rank test. There was no significant difference in protection among the other groups.