Although the basic biology of the malaria parasite was described more than a century ago, scientists today still struggle to understand its insidious details. An estimated 300 to 500 million people suffer from malaria, making it one of the most devastating diseases known. Research reported today in the Proceedings of the National Academy of Sciences adds an important new piece to the puzzle, revealing a potential mechanism whereby the parasites, having multiplied in their host's red blood cells, break free in order to invade more red blood cells.
While inside a red blood cell, the malaria parasite produces so-called "merozoites," which go on to infect other cells. Suspecting that protein-degrading enzymes, or proteases, might play a role in rupturing the blood cells and freeing the merozoites, researchers from Washington University studied the effects of a protease-blocking drug dubbed E64 on merozoite escape. Although the red blood cell membrane gave way, the drug appeared to thwart the rupture of a second membrane, which encases clusters of merozoites. The team thus proposes that parasite release is a two-step process in which encased clusters of merozoites exit the blood cells, and subsequently escape from their own membrane by way of a protein-degrading mechanism. Although understanding the exact mechanism will require further study, the findings may eventually offer anti-malarial drug developers a new target.