Malaria during pregnancy: parasites, antibodies and chondroitin sulphate A.

CSA-binding forms of P. falciparum appear uncommonly in non-pregnant hosts but are selected by the human placenta for growth. Parasites are presumably selected by adherence to CSA within the vascular compartment of the placenta, allowing IRBCs to sequester and multiply to high density. Chondroitin sulphate appears on the surface of placental syncytiotrophoblasts, and CSA is a component of PGs found in the placenta [42], but the identification of the CSA-containing PG(s) mediating IRBC adhesion in vivo requires further study. Anti-adhesion antibodies against CSA-binding parasites are associated with protection from maternal malaria, but these antibodies develop only over successive pregnancies, accounting for the susceptibility of primigravidas to infection. PfCSA-L, the parasite ligand mediating adhesion to CSA, has not yet been identified but is known to be antigenically conserved among isolates from around the world. An anti-adhesion vaccine delivered to women before first pregnancy could confer protection from maternal malaria and might be globally effective.