Invasion of enzyme-treated SAO and normal RBCs. Values are invasion of normal enzyme-treated RBCs (□) or SAO enzyme-treated RBCs (▦), expressed as percentage of the invasion into the corresponding untreated RBCs. Treatment was performed with neuraminidase (Nm), trypsin (Tr), neuraminidase plus trypsin (Nm+Tr), or chymotrypsin (ChTr). The values correspond to the average of 3 (3D7-A) or 2 (3D7-B) independent experiments performed with RBCs from 3 different age- and geography-matched SAO-control donor pairs. Error bars represent 95% confidence intervasl. The difference between normal and SAO cells was significant only for invasion of chymotrypsin-treated cells by 3D7-A, using Student t tests.