Fig. 1.

Models for Plasmodium falciparum survival after artemisinin treatment and isoleucine deprivation. a Upon artemisinin treatment, ring stage parasites exit the cell cycle and enter a programmed state of growth arrest to avoid drug-induced cellular damage, and resume growth once drug levels have subsided. While initial observations appeared to support this model, recent studies of artemisinin-resistant field isolates suggest an alternate model. b Upon withdrawal of extracellular isoleucine in vitro, Plasmodium falciparum initially slows growth, and may exit the cell cycle and arrest at the trophozoite stage prior to DNA replication. Isoleucine-deprived parasites can remain viable for several days and resume growth again upon isoleucine resupplementation