Figure 3

In vitro neutralization of the hemolytic activity of the alpha toxin of C. perfringens. Supernatants of C. perfringens (+contr.) were either left untreated or were pre-incubated with serum from calves immunized with native alpha toxin (rCpa), the non-toxic C-terminal fragment of alpha toxin (Cpa_247–370) or the adjuvant QuilA. They were then spotted on sheep blood agar and incubated overnight at 37 °C. Neutralization of alpha toxin activity results in absence of an outer zone of hemolysis. +, no neutralization of toxin activity; −, complete neutralization of toxin activity. Representative pictures of one out of three independent experiments.