FIG. 2.

PsaA-, PspA-, PspC-, and PdB-specific nasal antibody responses during pneumococcal carriage. Groups of five BALB/c mice were intranasally challenged with ≈7.5 × 10⁶ CFU of Streptococcus pneumoniae EF3030 in 15 μl of Ringer's solution. Nasal wash samples were collected 28 days postinfection, and S. pneumoniae PsaA-, PspA-, PspC-, and PdB-specific antibody titers were measured by ELISA that was capable of detecting >20 pg/ml of IgA or IgG antibodies. The data presented are the mean antibody concentrations ± standard error of the mean of three separate experiments with infected mice. Naïve mice displayed responses that were below the detection limit of the ELISA and are not shown. Asterisks indicate significant differences (P < 0.05) between the maximum and next highest antigen-specific IgA or IgG antibody levels in infected mice.