Figure 2. Serum antibody response of BALB/c mice following intranasal immunization with S. typhimurium SL3261 expressing P. aeruginosa serogroup O9 and bacterial loads in organs of intranasally immunized BALB/c mice after intranasal lethal challenge with P. aeruginosa PAO9.

Mice were immunized intranasally on day 0 and day 14 with 10⁷ CFU/mouse of the vector control (SL3261 (pLAFR376)) or the vaccine (SL3261 (pLAFRO9)). Sera were collected 2- and 4-weeks post-vaccination, and the data were analyzed by the Mann-Whitney U test. (A) Serum IgM and (B) IgG response to P. aeruginosa PAO9 whole antigen. (C) Survival rates for naïve mice after intranasal challenge with various doses of P. aeruginosa PAO9 (n=4 mice/group). (D) Bacterial load in the nasal wash and lungs, (E) liver and spleens of intranasally immunized mice 24 hours post-challenge with 2 × 10⁷ CFU of PAO9. All samples were plated for viable CFU on Pseudomonas isolation agar (PIA). Each point represents a single mouse.