Antibodies to Escherichia coli-Expressed C-Terminal Domains of Plasmodium falciparum Variant Surface Antigen 2-Chondroitin Sulfate A (VAR2CSA) Inhibit Binding of CSA-Adherent Parasites to Placental Tissue

Placental malaria (PM) is characterized by infected erythrocytes (IEs) that selectively bind to chondroitin sulfate A (CSA) and sequester in placental tissue. Variant surface antigen 2-CSA (VAR2CSA), a Plasmodium falciparum erythrocyte membrane pro-tein 1 (PfEMP1) protein family member, is expressed on the surface of placental IEs andmediates adherence to CSA on the sur-face of syncytiotrophoblasts. This transmembrane protein contains 6 Duffy binding-like (DBL) domains which might contribute to the specific adhesive properties of IEs. Here, we use laboratory isolate 3D7 VAR2CSADBL domains expressed in Escherichia coli to generate antibodies specific for this protein. Flow cytometry results showed that antibodies generated against DBL4, DBL5, DBL6, and tandem double domains of DBL4-DBL5 and DBL5-DBL6 all bind to placental parasite isolates and to lab strains selected for CSA binding but do not bind to children’s parasites. Antisera to DBL4 and to DBL5 inhibit maternal IE binding to placental tissue in a manner comparable to that for plasma collected frommultigravid women. These antibodies also inhibit binding to CSA of several field isolates derived from pregnant women, while antibodies to double domains do not en-hance the functional immune response. These data support DBL4 and DBL5 as vaccine candidates for pregnancy malaria and demonstrate that E. coli is a feasible tool for the large-scale manufacture of a vaccine based on these VAR2CSA domains. Pregnancy malaria (PM) results when Plasmodium falciparum-infected erythrocytes (IEs) sequester in intervillous spaces, leading to severe clinical sequelae for the mother and her fetus. Malaria infection during pregnancy is related to both materna