Figure 6. Passive mAb protection in mice against TcdA toxin challenge. (A) Passive protection experiments were conducted with individual mAb 2C7, 5D8 and 4A4 and negative controls PBS and mouse Ig isotype control matching mAb . * indicates a statistically significant difference (p < 0.05) compared with the negative controls (PBS or isotype Ig control groups). (B) Passive protection experiments were conducted with individual mAb 4A4 or a mixture of two mAb 4A+5D8 or 4A4+2C7, in addition to the Ig isotype control. ** indicates a statistically significant difference (p < 0.05) compared with the mAb 4A4 alone group. There were 24 Balb/C mice in 4A4 group and 8 mice/group in other groups.