By comparing the genomes of malaria parasites that affect chimpanzees and those that affect humans, researchers discovered that it is the difference in the parasites’ surface proteins that determine which host it will infect.
Out of a genome of approximately 5,500 genes, researchers found that most genes have directly equivalent counterparts between the human and primate parasites. However, portions of the P. falciparum genome that differed most profoundly from the P. reichenowi parasite that infects chimpanzees were found to encode proteins that help the parasite to bind to and invade red blood cells, which is where the parasite grows and multiplies. “Discovering that the key differences lie in genes responsible for red blood cell invasion reassures us that we’ve been looking in the right place,” says Dr Thomas Otto, first author at the Wellcome Trust Sanger Institute. “Researchers have identified surface proteins as promising vaccine candidates already; and our finding adds more support, showing that it is the difference in the parasites’ surface proteins that determine which host it will infect.”
This is the first time that an essentially complete genome has been produced for a malaria parasite that infects such a close relative of humans. It provides the first systematic view of the differences between parasites that infect humans and those that infect our close relatives. Human malaria emerged from the Great Apes, so this comparison using chimpanzee malaria is the closest that scientists have come to a full catalogue of the changes associated with parasites switching from our primate relatives into humans.