FIG. 3.

Serum IgG response to toxin A or B in prechallenge samples. Sera from hamsters either primed (a) or boosted (b) by various mucosal routes with C. difficile culture filtrate toxoid were analyzed by indirect ELISA. Samples in panel a were diluted to 1:50,000 or 1:10,000 for anti-toxin A (solid bars) or B (hatched bars) responses, respectively. Samples in panel b were diluted to 1:12,500 or 1:8,000 for anti-toxin A (solid-bars) or B (hatched bars) responses, respectively. Each bar represents the mean and standard deviation for five animals. OD 405, optical density at 405 nm. See Table 1 for a description of the immunization regimens used.