STABLE TRANSFECTION OF MALARIA PARASITE BLOOD STAGES

Genetic manipulation of malaria parasites would revolutionize the stud y of this group of pathogens and have implications for vaccine and dru g development. This report describes the stable, drug-selectable genet ic transformation of the clinically relevant intracellular blood stage s of a malaria parasite. A plasmid transfection vector carrying the ge ne locus that encodes a drug-resistant form of the bifunctional enzyme dihydrofolate reductase-thymidylate synthase from the rodent malaria parasite Plasmodium berghei was constructed. Derivatives of this vecto r were introduced into merozoites of P. berghei by electroporation, an d parasites were selected for successful transformation in the rodent host on the basis of resistance to pyrimethamine. The plasmids were pr esent in a circular, unrearranged form that replicated episomally to a n observed maximum of 15 copies per cell in drug-resistant populations .