FIG 5.

EhMSP-1 vaccination facilitates lysis of E. histolytica trophozoites through activation of the classical complement cascade. (A) Kinetics of amebic lysis via the classical complement cascade following in vitro exposure to polyclonal IgG from immunized and nonimmunized animals. Amebae were preincubated with purified IgG (5 μg/ml) from either immune or nonimmune animals, followed by addition of normal hamster serum and evaluation of cell lysis at the indicated times. Heat-inactivated serum and EGTA, which inhibits the classical complement cascade, served as additional controls for specificity. Conditions: [circf], immune IgG plus normal human serum; [squlo], nonimmune IgG plus normal human serum; [trif], immune IgG plus normal human serum plus EGTA; [itrio], nonimmune IgG plus normal human serum plus EGTA; [diaf], immune IgG plus inactivated serum; [circo], nonimmune IgG plus inactivated serum; [diao], only amebae plus inactivated serum. *, P < 0.05 versus nonimmune IgG plus normal serum (n = 3, mean and SEM). (B) Dose effect of purified IgG from EhMSP-1-vaccinated animals on amebic lysis. Amebic trophozoites were preincubated with purified IgG from immunized (immune) and control (nonimmune) animals at either 5 μg/ml or the indicated concentration. Cell lysis was measured 30 min following addition of normal human serum. Incubation in the presence of EGTA or heat-inactivated serum served as an additional control for specificity. P was <0.001 for *** and #, and P was <0.05 for ** versus nonimmune IgG control in each case (n = 3, mean and SEM).