FIGURE 5.

Antiserum neutralization of toxin after B2′B3 domains of TcdB₀₁₂ and TcdB₀₂₇ are exchanged. The graphs represent the percentage of viable CHO cells after treatment for 24 h with different forms of TcdB. Measurement of cell viability was accomplished by a colorimetric reaction using WST-8 dye. TcdB neutralization was performed by preincubating the toxin for 30 min with a 1:100 dilution of prebleed serum or antiserum against B2′B3₀₁₂ (αB2′B3₀₁₂). Data are presented as mean (n = 3) ± S.D. (error bars). Asterisks indicate significant differences between TcdB₀₁₂ and TcdB₀₂₇/B2′B3₀₁₂. *, p < 0.05; **, p < 0.005.