Effect of host cell attributes on invasion efficiency. (A) P vivax invasion efficiency, determined from 1200 target cells (n = 3 isolates), was not significantly associated with the presence of fetal Hb (stained in green). The bottom right inset shows a P vivax (nucleus stained with Dapi blue) in a newly invaded RBCs devoid (top micrograph) or containing fetal Hb. (B) The P vivax invasion efficiency (n = 5 isolates) was not affected by the ABO blood group of the reticulocytes used in the invasion assay. Invasion efficiencies were significantly associated with the particular isolate used (isolates M388 and W143 consistently invaded the distinct target cell preparation at a higher efficiency than that observed for isolates M126, M413, and M114).