Fig. 1

Experimental Design and Invasion inhibition activity for humAb 099100 to PvDBPII: Cultures were initiated from a cryopreserved stock of P. knowlesi A1.H.1 strain and were maintained in human RBCs at 2% haematocrit. Parasites were enriched for schizonts using a Nycodenz gradient. The schizont preparation was labelled with CellTrace to identify them as donor cells. Donor cells were then mixed with unlabelled recipient cells at a ratio of 1:20 and incubated with/without experimental reagents. A Rows one and two show cultures at time zero hour and at 6 h respectively, indicating new invasion events (orange arrow). After 6 h of culture, samples were stained with Hoechst 33342 for DNA content (Y-axis, and thiazole orange, left-hand panel and Far Red (CellTrace, middle and right panels) to identify rings (red boxes) that represent new invasion events (CT negative, N = 4956 at 6 h) and schizonts (green boxes). Row three shows the blocking of PkPvDBPOR invasion with a camelid nanobody CA111. Row four shows culture containing a negative control humAb 043048 (tetanus toxoid-specific). B The top and bottom rows show 6 h cultures treated with humAb 099100 at the lowest and highest concentration, respectively, of a two-fold dose response. C The full growth inhibition curve of 099100