Plasmodium falciparum population dynamics in a cohort of pregnant women in Senegal

The dynamics of P. falciparum genotypes during pregnancy in 32 women in relation to VAR2CSA polymorphism and immunity was determined. The polymorphism of the msp2 gene and five microsatellites was analysed in consecutive parasite isolates, and the DBL5ε + Interdomain 5 (Id5) part of the var2csa gene of the corresponding samples was cloned and sequenced to measure variation.In primigravidae, the multiplicity of infection in the placenta was associated with occurrence of low birth weight babies. Some parasite genotypes were able to persist over several weeks and, still be present in the placenta at delivery particularly when the host anti-VAR2CSA antibody level was low. Comparison of diversity among genotyping markers confirmed that some PAM parasites may harbour more than one var2csa gene copy in their genome.Host immunity to VAR2CSA influences the parasite dynamics during pregnancy, suggesting that the acquisition of protective immunity requires pre-exposure to a limited number of parasite variants. Presence of highly conserved residues in surface-exposed areas of the VAR2CSA immunodominant DBL5ε domain, suggest its potential in inducing antibodies with broad reactivity.In sub-Saharan Africa, 25 million pregnant women are at risk of Plasmodium falciparum infection every year[1,2]. Plasmodium falciparum isolates infecting pregnant women are special in that parasites are able to sequester in vivo in the intervillous space and bind in vitro to chondroitin sulphate A (CSA) [3,4]. This placental accumulation of infected red blood cells (IRBCs) is associated with the low birth weight of the newborn [5].The parasite ligand involved in this interaction between the IRBCs and CSA is a specific PfEMP1 variant named VAR2CSA [6-8]. Serum samples from exposed pregnant women specifically recognize CSA-binding infected erythrocytes, independently of their geographic origin and are able to inhibit binding to CSA in vitro. This suggests that the antigenic targets specifying placental