Red cell age and susceptibility to malaria during pregnancy

Increased susceptibility to malaria in pregnancy is well recognized, and has generally been assumed to be due to hormonal changes resulting in altered immunity. Based on previous work demonstrating enhanced parasite growth in young normal and thalassemic red blood cells, we hypothesized that in pregnancy increased malaria susceptibility may be due, in part, to the increase in the population of young red cells.

FC27 strain of Plasmodium falciparum was cultured in the red cells and sera from healthy primigravida pregnant (n=9) and non-pregnant (n=9) women. Red cells from both pregnant and non-pregnant women were each placed in three cultures containing the sera from pregnant, non-pregnant and pooled control samples. Cultures were set up in triplicate and incubated for 144 hours. Parasite development and growth were assessed by slide microscopy.

At 96 hours the median parasite growth in cells from pregnant samples (5.7%) was significantly better than that in the non-pregnant cells (4.8%) (p=0.01). There was no significant difference in parasite growth in cultures with pregnant and non-pregnant sera. As expected, there were significant differences in parameters measuring red cell age between the cells from pregnant and nonpregnant samples: median red cell creatine (11.09 mg/dl) versus (6.90 mg/dl) (p=0.004) and median reticulocyte count (2.3%) versus (1.4%) (p=0.0006).

These preliminary results are consistent with the hypothesis that an increased population of young red cells may contribute to increased malaria susceptibility during pregnancy.