Fig. 8: Protection against live Streptococcus pneumoniae infection by intranasal vaccination.
A Experimental schedule of lethal challenge with live S. pneumoniae. Determination of the protective immune response against lethal challenge with S. pneumonia WU2 (B) or D39 (C) strain. Groups of mice were intranasally (I.N.) vaccinated with PBS, 6.5 μg of FlaB-tPspA, or 14.5 μg of FPB NC three times at two-week intervals. Two weeks after the last immunization, the immunized mice were I.N. challenged with a 1.9 x LD50 of live S. pneumoniae WU2 (n = 9 biological replicates) or a 1.7 x LD50 of live S. pneumoniae D39 (n = 10 biological replicates) separately. After the challenge, the survival rate was monitored. Statistical differences were analyzed by the log-rank (Mantel-Cox) test. D Determination of pneumococcal colony-forming units (CFU) in lung tissue, bronchoalveolar lavage fluid (BAL-F), and blood samples. Two weeks after the final immunization, mice were intranasally challenged with live S. pneumoniae WU2 (0.6 × 108 CFU/mouse; 0.6×LD50). Seventy-two hours post-challenge, pneumococcal CFU was quantified in lung tissue, BAL-F, and blood samples (n = 4 biological replicates). Data are presented as mean values ± SEM. Statistical differences were analyzed using one-way ANOVA. Statistical significance: *P < 0.05; **P < 0.01; ****P < 0.0001; ns = not significant. Source data are provided as a Source Data file. Detail P values are provided in the Source Data file.
