FIG 4.

Bmem-encoded neutralizing Ab is durable and protects against in vivo challenge with TcdB. (A) Six months after the initial immunization (4 months after booster), mice from the experiment whose results are shown in Fig. 1 were bled again, and neutralization assays were repeated. Statistical significance was determined by ANOVA and is indicated by asterisks: **, P = 0.01 to 0.001; ***, P < 0.001. (B) Mice were then challenged i.v. with TcdB1 (20 ng/g of body weight). The graph shows survival of naive mice (n = 5) and those immunized with 25 μg (n = 9), 50 μg (n = 10), or 100 μg (n = 10) of Imject-adsorbed CTD1. (C) Naive B6 mice were transferred (i.p. route) with 400 μl of serum from naive or immunized donor mice. After 24 h, mice were challenged with TcdB1 (20 ng/g of body weight). The graph depicts percent survival over time. Three mice per group were used. Statistical significance in panels B and C was determined by Kaplan-Meier analysis with log rank test, and P values comparing immunized or serum-transferred groups to naive controls are shown.