Host iron status and erythropoietic response to iron supplementation determines susceptibility to the RBC stage of falciparum malaria during pregnancy

Anaemia and malaria are both common in pregnant women in Sub-Saharan Africa. Previous evidence has shown that iron supplementation may increase malaria risk. In this observational cohort study, we evaluated P. falciparum pathogenesis in vitro in RBCs from pregnant women during their 2nd and 3rd trimesters. RBCs were collected and assayed before (n = 327), 14 days (n = 82), 49 days (n = 112) and 84 days (n = 115) after iron supplementation (60 mg iron as ferrous fumarate daily). P. falciparum erythrocytic stage growth in vitro is reduced in anaemic pregnant women at baseline, but increased during supplementation. The elevated growth rates parallel increases in circulating CD71-positive reticulocytes and other markers of young RBCs. We conclude that Plasmodium growth in vitro is associated with elevated erythropoiesis, an obligate step towards erythroid recovery in response to supplementation. Our findings support current World Health Organization recommendations that iron supplementation be given in combination with malaria prevention and treatment services in malaria endemic areas.

Preferential invasion by Plasmodium merozoites and the self-regulation of parasite burden

The preferential invasion of particular red blood cell (RBC) age classes may offer a mechanism by which certain species of Plasmodia regulate their population growth. Asexual reproduction of the parasite within RBCs exponentially increases the number of circulating parasites; limiting this explosion in parasite density may be key to providing sufficient time for the parasite to reproduce, and for the host to develop a specific immune response. It is critical that the role of preferential invasion in infection is properly understood to model the within-host dynamics of different Plasmodia species. We develop a simulation model to show that limiting the range of RBC age classes available for invasion is a credible mechanism for restricting parasite density, one which is equally as important as the maximum parasite replication rate and the duration of the erythrocytic cycle. Different species of Plasmodia that regularly infect humans exhibit different preferences for RBC invasion, with all species except P. falciparum appearing to exhibit a combination of characteristics which are able to self-regulate parasite density.

Erythrocyte changes in preeclampsia: relationship between maternal and cord blood erythrocyte damage

Our aim was to evaluate red blood cell (RBC) changes in normal and preeclamptic cases, and to assess the relationship between maternal and umbilical cord blood (UCB) changes. We evaluated markers of RBC damage: membrane bound hemoglobin (MBH) and band 3 profile - high molecular weight aggregates (HMWSAg), monomer and proteolytic fragments. RBCs are marked for removal by a rise in MBH and in HMWAg. Preeclamptic mothers had significantly higher MBH, RBC count, hemoglobin, hematocrit, reticulocytes and reticulocyte production index (RPI). In UCB from newborns of preeclamptic mothers, we found similar HMWAg, RBC count, hemoglobin and hematocrit; significantly higher MBH, mean cell hemoglobin concentration, mean cell volume, RPI and reticulocyte count. Maternal MBH and HMWAg values were positively and significantly correlated with MBH and HMWAg values in UCB, in normal as well as in preeclamptic pregnancies; in preeclampsia, a significant positive correlation between UCB and maternal bilirubin, and between RPI and proteinuria were found. We conclude that markers of RBC damage/production are altered in preeclampsia, in both UCB and maternal circulation. Our data show similarities between UCB and maternal RBC changes, as suggested by the correlations of markers of RBC damage.