Plasmodium falciparum:Heterologous Synthesis of the Transmission-Blocking Vaccine Candidate Pfs48/45 in Recombinant Vaccinia Virus-Infected Cells

Milek, R. L. B., DeVries, A. A. F., Roeffen, W. F. G., Stunnenberg, H., Rottier, P. J. M., and Konings, R. N. H. 1998.Plasmodium falciparum: Heterologous synthesis of the transmission-blocking vaccine candidate Pfs48/45 in recombinant vaccinia virus-infected cells.Experimental Parasitology90, 165–174. With the aim of developing transmission-blocking vaccines based on the sexual stage-specific surface antigen Pfs48/45 of the human malaria parasitePlasmodium falciparum, the gene encoding Pfs48/45 was incorporated into the genome of a recombinant vaccinia virus. In virus-infected mammalian tissue culture cells, recombinant Pfs48/45 antigen (rPfs48/45) is posttranslational modified to produce a highly N-glycosylated polypeptide. The rPfs48/45 protein was radiolabeled with ethanolamine, consisting of a further posttranslational modification in the form of a glycosylphosphatidylinositol anchor at its carboxy-terminal end. The rPfs48/45 was not detected on the surface of the infected cells; instead, it remained within the secretion pathway of mammalian cells irrespective of the duration of infection or culture temperature. Studies with monoclonal antibodies specific for disulfide band-dependent epitopes of Pfs48/45 revealed that recombinant Pfs48/45 is not folded in its authentic conformation even if N-glycosylation was chemically inhibited. Infection of mice and rabbits with recombinant virus elicited Pfs48/45-specific antibodies; however, the antisera failed to block parasite transmission in a standard mosquito membrane-feeding assay.