Altered Subpopulations of Red Blood Cells and Post-treatment Anemia in Malaria.

In acute malaria, the bulk of erythrocyte loss occurs after therapy, with a nadir of hemoglobin generally observed 3-7 days after treatment. The fine mechanisms leading to this early post-treatment anemia are still elusive. We explored pathological changes in RBC subpopulations by quantifying biochemical and mechanical alterations during severe malaria treated with artemisinin derivatives, a drug family that induce "pitting" in the spleen. In this study, the hemoglobin concentration dropped by 1.93 G/dl during therapy. During the same period, iRBC accounting for 6.12% of all RBC before therapy (BT) were replaced by pitted-RBC, accounting for 5.33% of RBC after therapy (AT). RBC loss was thus of 15.9%, of which only a minor part was due to the loss of iRBC or pitted-RBC. When comparing RBC BT and AT to normal controls, lipidomics revealed an increase in the cholesterol/phosphatidylethanolamine ratio (0.17 versus 0.24, < 0.001) and cholesterol/phosphatidylinositol ratio (0.36 versus 0.67, = 0.001). Using ektacytometry, we observed a reduced deformability of circulating RBC, similar BT and AT, compared to health control donors. The mean Elongation Index at 1.69Pa was 0.24 BT and 0.23 AT vs. 0.28 in controls ( < 0.0001). At 30Pa EI was 0.56 BT and 0.56 AT vs. 0.60 in controls ( < 0.001). The retention rate (rr) of RBC subpopulations in spleen-mimetic microsphere layers was higher for iRBC (rr = 20% = 0.0033) and pitted-RBC (rr = 19%, = 0.0031) than for healthy RBC (0.12%). Somewhat surprisingly, the post-treatment anemia in malaria results from the elimination of RBC that were never infected.