Figure 4.

Characterization of schistosome surface calpain activity. (A) Calpain activity measured in 1000 live schistosomula in the presence ( + ) or absence (−) of 3 mM Ca²⁺. Calpain activity detected in 1,000 living schistosomula (B) or individual male worms (C) in the presence or absence of the calpain inhibitors (E64c, calpastatin and PD150606, as indicated). Parasites were pre-incubated with inhibitor for 20 min before the addition of substrate. All activity data are presented as relative fluorescence units (RFU, mean+/−SD, n ≥ 3) where fluorescence is generated following substrate cleavage and is measured at excitation/emission 320/480. (D) Analysis of schistosomula viability after incubation in the presence of inhibitor (E64c or E64d, 100 µM) for 1, 2 or 7 days (as indicated). Data are shown relative to day 0, control parasite viability, set at 100%.