FIGURE 5.

Long-term antibody response of immunized mice. rTcdB-specific IgG (1:20,000 dilution) (A) and IgA (1: 1,000 dilution) (B) titers from the serum of immunized mice were determined by ELISA. NP₂₀₀, NP₃₅₀, NP₅₀₀, NP₇₅₀: injection with NP-rTcdBs with the corresponding size in nanometers; Al+rTcdB: injection with 20 μg purified rTcdB mixed with Alum. All data are presented as mean ± standard deviations and statistical comparisons among groups were analyzed by Student’s t-test and ANOVA (n = 5, ^∗∗P ≤ 0.01, ^∗∗∗p ≤ 0.001, ^∗∗∗∗p ≤ 0.0001). NS, not significant. All data are representative of at least three independent experiments.