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. 2015 Jun 29;212(12):1939–1948. doi: 10.1093/infdis/jiv341

Figure 4.

Figure 4.

Antibody responses and survival of mice after Streptococcus pneumoniae challenge. Mice were mock-immunized with medium or immunized with the PR8/PB2–green fluorescent protein (GFP) or PR8/PB2–pneumococcal surface protein A (PspA) virus 3 times at 2-week intervals. A. B, PspA-specific antibodies raised by the immunized mice were detected by means of an enzyme-linked immunosorbent assay with PspA as an antigen. Immunoglobulin (Ig) G titers in serum (A), IgG and IgA titers in bronchoalveolar lavage fluid (BALF) (B, left panel), and nasal wash samples (B, right panel) from mice intranasally mock-immunized with medium or immunized with the PR8/PB2-GFP or PR8/PB2-PspA virus were measured. Values are expressed as the mean (standard deviation [SD]) reciprocal log2 titer of 6 samples. *P < .05. C, Two weeks after the final vaccination, mice were intranasally challenged with 3-fold 50% mouse lethal dose of WU2 strain. Survival was monitored in 10 mice for 10 days after challenge. †P < .01.