Imaging liver-stage malaria parasites.

Plasmodium parasites, the causative agents of malaria, first invade and develop within hepatocytes before infecting red blood cells and causing symptomatic disease. Because of the low infection rates in vitro and in vivo, the liver stage of Plasmodium infection is not very amenable to biochemical assays, but the large size of the parasite at this stage in comparison with Plasmodium blood stages makes it accessible to microscopic analysis. A variety of imaging techniques has been used to this aim, ranging from electron microscopy to widefield epifluorescence and laser scanning confocal microscopy. High-speed live video microscopy of fluorescent parasites in particular has radically changed our view on key events in Plasmodium liver-stage development. This includes the fate of motile sporozoites inoculated by Anopheles mosquitoes as well as the transport of merozoites within merosomes from the liver tissue into the blood vessel. It is safe to predict that in the near future the application of the latest microscopy techniques in Plasmodium research will bring important insights and allow us spectacular views of parasites during their development in the liver.