Figure 1.

Neutralization capacity of whey protein isolate (WPI) solutions. Defined pure TcdA orTcdB solution could be diluted to a factor of 10⁻⁵ (10⁻⁷) on HT29 human colorectal adenocarcinoma cells (or chinese hamster ovary (CHO) cells) to still show cytotoxic activity (cell detachment). This material was used as control. The same toxin solutions were preincubated with anti-CD-WPI for 1 h before determining the remaining cytotoxic activity. The neutralization capacity represented the reduction of the TcdA or TcdB cytotoxicity compared to the effect of the pure toxin exposed exclusively to the buffer. (A) shows the neutralization capacity for different concentrations of dissolved WPI powder (weight per volume). Accordingly, percentages of WPI were chosen to define WPI 100 and WPI 1000, and their neutralization capacities were verified, as indicated in (B) and (C). Control-WPI was prepared from cows before immunization and WPI 10,000 was obtained from the colostrum of immunized cows. Control-WPI, WPI 100, WPI 1000 and WPI 10,000 were used in the hamster protection experiment.