Recombinant Pfs230, a Plasmodium falciparum gametocyte protein, induces antisera that reduce the infectivity of Plasmodium falciparum to mosquitoes

Six regions of malaria transmission-blocking target antigen, Pfs230, encoding 80% of the 363-kDa protein, were expressed as recombinant proteins in E. coli as fusions with maltose-binding protein (MBP). Antisera generated against amylose-purified recombinant Pfs230 MBP fusion proteins (r230/MBP.A-r230/MBP.F) all recognized the 360-kDa form of parasite-produced Pfs230 by immunoblot. However, only antisera against the four carboxy regions (CF) of Pfs230 and not the two amino regions (A and B) recognized the 310-kDa form of Pfs230, the form expressed on the surface of gametes. The data suggest that the 310-kDa form of Pfs230 arises from the cleavage of 50 kDa from the amino terminus of the 360-kDa form. Furthermore, antisera against r230/MBP.C bound to the surface of intact gametes and significantly reduced (by 71.2-89.8% (rank sum analysis, P < 0.01)) the infectivity of P. falciparum parasites to mosquitoes. This is the first report of a recombinant form of a P. falciparum gametocyte protein capable of inducing antisera that reduce malaria parasite infectivity to mosquitoes.