Figure 1

Surface reactivity and inhibitory capacity of serum specific for DBL domains of VAR2CSA from 3D7 and HB3. A and B: Sera from three rats immunized with the same recombinant protein were pooled and tested in FACS. The surface reactivity was measured using 10 μl serum in a total volume of 100 μl against 2 × 10⁵ late trophozoite and schizont-infected erythrocytes (IE). To measure the level of rat IgG bound to the surface of the IE 1 μl rabbit anti-rat IgG-FITC was used in a total volume of 100 μl and the mean fluorescence intensity of 5000 cells was analysed and shown in white bars. The assays were performed twice with similar results. C & D: For inhibition of IE binding to CSPG, 15 μl of rat serum in a total volume of 120 μl were tested in triplicate wells of 96 well Falcon plates coated with 2 μg/ml CSPG. Serum pools and tritium labelled parasites (2 × 10⁵) were added simultaneously to the wells and incubated for 2 hours. Hereafter the plate was washed using a pipetting robot and the remaining cells were harvested on a filter plate and counted using scintillation. The mean percentage of binding is shown relative to binding in wells without inhibitor. Error bars are standard deviations of triplicate measurements. The assays were performed twice with similar results. In both types of assays serum from rats immunized with FCR3 var1-DBL3γ and 3D7 PF08_0141-DBL2 β were used as negative controls.