Cysteine peptidases vaccine potential.

Mice were immunized 1x (a) or 2x (b–e) with 10 (a–d) or 20 (e) µg active (a–e) or inactive (d,e) cysteine peptidase/mouse/injection, alone (a–e) or in a mixture (d,e), and exposed 15 days later to 120 (a–c) or 140 (d,e) S. mansoni cercariae. Columns represent mean worm burden in 7–14 mice/group, and vertical bars denote SD about the mean. P values and percent reduction in worm burden as compared to control mice are shown above the columns of the test groups. Differences in mean worm burden between mice immunized with active and inactive cysteine peptidases (d,e) are highly significant (P<0.0001).