FIG. 2.

Characterization of plasma OP-Tb activity with anti-OP-Tb IgY. (A) OP-Tb activity-neutralizing activity of anti-OP-Tb IgY. Week 13 anti-OP-Tb IgY was tested at various concentrations for inhibitory activity against the OP-Tb-catalyzed hydrolysis of Cbz-Arg-Arg-AMC (5 μM) in 50 mM Tris-HCl, pH 8, at 37°C. (Inset) Generation of inhibitory antibodies over the immunization period. Antibodies harvested at various times after the primary immunization were tested for their ability to inhibit OP-Tb activity against Cbz-Arg-Arg-AMC. Antibodies were tested at an assay concentration of 250 μg · ml⁻¹, and their effect was compared to the effect of preimmune (control) antibodies at the same assay concentration. Arrows indicate booster immunizations. Values are means ± standard deviations (n = 3). (B) Kinetics of OP-Tb release into the plasma of infected rodents. Blood from T. b. brucei-infected rats was drawn daily and evaluated for Cbz-Arg-Arg-AMC-hydrolyzing activity and parasitemia. Activity is represented as picomoles of AMC released per minute per milliliter of whole blood in the presence of preimmune control (■) and week 13 anti-OP-Tb IgY (□) at 250 μg · ml⁻¹. While the data here are depicted for a single animal, they are representative of the trend observed in two other animals.