FIG 3.

Inhibition of erythrocyte and reticulocyte binding and P. vivax invasion ability by antibodies. (A and B) Inhibition of PvDBPII binding by antibodies against PvDBPII (A) and inhibition of PvMSP1P-19 binding by antibodies against PvMSP1P-19 (B). Upper panels, confocal microscopy images show PvDBPII and PvMSP1P-19 expression on the surface of COS-7 cells; this expression was confirmed by GFP and specific antibody recognition using antibodies against PvDBPII and antibodies against PvMSP1P-19, respectively. Lower panels, data are shown as the mean ± SD of the binding inhibition measured in three independent experiments. Significant differences in the effects of PI sera and those of other antibodies were calculated using Student's t test: single asterisks, P < 0.05; double asterisks, P < 0.01; triple asterisks, P < 0.001. (C) Inhibitory activity of serial dilutions of sera from P. vivax-infected patients (ROK+) or from uninfected persons (ROK−) on binding to erythrocytes and reticulocytes. Significant differences in the effects of ROK− and ROK+ sera were calculated using Student's t test: single asterisks, P < 0.05; double asterisks, P < 0.01; triple asterisks, P < 0.001. (D) The vivax parasite invasion inhibition efficacy was confirmed in invasion inhibition assays. The data are presented as the mean ± SD of the invasion inhibition rate obtained with preimmune sera (PI) (n = 7), anti-2C3 antibody (murine anti-Fy6) (n = 7), anti-PvMSP1-19 sera (n = 7), anti-PvMSP1P-19 sera (n = 7), and anti-PvDBPII sera (n = 5). Significant differences between PI sera and anti-2C3, anti-PvMSP1-19, anti-PvMSP1P-19, and anti-PvDBPII immunized sera were calculated using one-way ANOVA with Tukey's posttest: single asterisks, P < 0.05; double asterisks, P < 0.01; triple asterisks, P < 0.001.