Regions of re-codonized 3D7-var2csa (PFL0030c) and FCR3-var2csa covering the entire exon 1 were subcloned into the pBAD-TOPO vector, transferred with the V5 and HIS tag to the pAcGP67-A transfer vector (BD Biosciences), produced as recombinant proteins in Baculovirus-infected insect cells, and purified as described (Salanti et al., 2004) . We have previously shown that Baculovirus-produced VAR2CSA constructs are conformationally intact, as they induce production of rabbit antisera reactive with native VAR2CSA on the surface of IEs (Barfod et al., 2006) . The following regions (indicated by encoded amino acids numbers) were produced: -1967, N: 1380-1579, O: 1559-1992, Q: 1776-2131, R: 1965-2666, S: 1981-2336, U: 1981-2524, V: 2147-2666, X: 2210-2666 and Y: 2317-2666 . Different variants of DBL3-X were cloned and produced as described . For the cloning of the chimeric construct composed of 5′ 3D7-VAR2CSA DBL3-X and 3′ FCR3-VAR2CSA DBL3-X, we used the primers 5′: