Malaria has been outsmarting the human immune system for centuries. Now, using real-time imaging to track malaria infections in live mice, researchers have discovered one of the parasite's sneakiest tricks--using dead liver cells to cloak and transport itself back into the bloodstream after leaving the liver.
Robert Mnard, a Howard Hughes Medical Institute (HHMI) international research scholar, and his postdoctoral fellow, Rogerio Amino, at the Institut Pasteur in Paris, filmed the malaria parasite as it transitioned from infecting liver cells to infecting red blood cells. During this stage of the parasite's life cycle, the classic symptoms of malaria high fevers and chills are triggered in people who are infected.
Mnard and Amino collaborated with Volker Heussler at the Bernhard-Nocht Institute for Tropical Medicine in Hamburg, Germany. Their images of the parasite sneaking back into the host's bloodstream--published in advance online in Science Express on August 3, 2006, and scheduled for September 2006 publication in Science--clear up a long-standing puzzle about the malaria parasite's life cycle. The discovery could lead to new ways of treating malaria, a disease that infects 300 million people per year and kills 1 million.
"The parasite has evolved this complex structure. The best image to describe it is the Trojan horse, because it both transports the parasites and camouflages them," said Mnard. Like the ancient Greek warriors who hid inside a giant hollow horse to gain entry to Troy, the malaria parasites wrap themselves in a structure made of liver cell membrane. This membrane cloak enables them to sneak past immune cell sentinels and return to the bloodstream.
The malaria parasite, Plasmodium falciparum, has a complex life cycle. It passes from a mosquito's saliva to a human's blood, and then travels to the liver, where it infects and kills liver cells. After it leaves the liver, the parasite moves back into the
Contact: Jennifer Donovan
Howard Hughes Medical Institute