Fig 2. Effects of sera from hamsters vaccinated with the rIgl-1 (A) and C-Igl (B) on the adherence of CHO cells to E. histolytica. Trophozoites were pretreated with 1:1,000, 1:100, 1:10 diluted pooled sera from immunized hamsters and were then incubated with CHO cells. The number of trophozoites with at least three adherent CHO cells was scored by examining at least 300 trophozoites. Adherence was expressed as the percentage of adherence seen in phosphate-buffered saline -treated controls. Error bars represent the standard deviations of the means calculated from three independent replicates. *P < 0.001; **P < 0.001. (C) Complement-mediated lysis of E. histolytica by the sera from hamsters vaccinated with C-Igl.

Trophozoites were incubated with different dilutions of serum from C-Igl immunized or sham-immunized hamsters and different dilutions of guinea pigs’ complement or heat-inactivated hamster serum (without complement). EGTA, which inhibits the classical complement cascade, served as additional controls for specificity. Cell lysis was measured 60 min after incubation. Heat-inactivated serum was used as a control. Error bars represent the standard deviations of the means calculated from four independent replicates. *P < 0.05; **P < 0.001 (vs. sham-immune control).