Ex Vivo Maturation Assay for Testing Antimalarial Sensitivity of Rodent Malaria Parasites

Ex vivo assay systems provide a powerful approach to studying human malaria parasite biology and to testing antimalarials. For rodent malaria parasites, short-term in vitro culture and ex vivo antimalarial susceptibility assays are relatively cumbersome, relying on in vivo passage for synchronization, since ring-stage parasites are an essential starting material. Here, we describe a new approach based on the enrichment of ring-stage Plasmodium berghei, P. yoelii, and P. vinckei vinckei using a single-step Percoll gradient. Importantly, we demonstrate that the enriched ring-stage parasites develop synchronously regardless of the parasite strain or species used. Using a flow cytometry assay with Hoechst and ethidium or MitoTracker dye, we show that parasite development is easily and rapidly monitored. Finally, we demonstrate that this approach can be used to screen antimalarial drugs.