Figure 4. Binding to pneumococcal surface, complement deposition and passive protection elicited by anti-PspA5 antibodies.

Sera from BALB/c mice immunized with PspA5 (dotted black lines), PspA5-wP (solid black lines) or PspA5-wP_low (solid dark gray lines) were tested for the ability to bind to the pneumococcal surface (A) and to mediate C3 deposition (B). S. pneumoniae ATCC 6303(PspA5) was incubated with 2% (A) or 10% of each group serum (B). Sera from non-immunized animals (gray areas) and immunized with wP (solid light gray lines) or wP_low (dotted light gray lines) were used as control. The median fluorescence of bacteria is shown for each sample. Data are representative of two independent experiments. Naïve mice were inoculated trough the intraperitoneal route with a 1∶100 dilution of each serum 2 h before pneumococcal challenge. Survival was monitored until 10 days after challenge (C). ***P<0.001 when compared with control groups and P = 0.004 when compared with mice vaccinated with PspA5 by Fisher exact test. Data were composed with two independent experiments.