Hope for Vaccine Lies in the Parasite Itself
The Plasmodium parasite leads a strange and complicated life, crisscrossing between two "host" species humans and mosquitoes. Within the short span of just a few weeks, the organism cycles through a half dozen radically different sizes and shapes and alternatively makes its home in the human liver, a person's bloodstream, the insect stomach, and a mosquito's spit.
For years scientists knew that the most fruitful way to fight the parasite would be to target the form in which it exists in the bloodstream, since that is where the majority of clinical symptoms occur. Existing drugs, like quinine and artemisinin, both target the parasite in the blood.
About 15 years ago, scientists discovered a potential new source of drug targets in a tiny, factory-like enveloped organelle called an apicoplast that exists within the parasite. It was unlike anything found normally in the human body, which suggested that drugs designed to interfere with it might kill the parasite while essentially leaving people unharmed.
"It was a very exciting discovery," DeRisi said, "but in the years since, the prospect of finding drugs to target it has been frustrating and disappointing in many respects."
In the last decade, the evolutionary history of this strange organelle has unfolded. The apicoplast is the strange remnant of collisions between competing cells far back in evolutionary history. Scientists reason that through the course of evolution, the apicoplast arose from its origin as a standalone bacterium into its current form through a series of at least two endosymbiotic events, in which one cell engulfs and permanently acquires genetic material and cellular machinery of another for its own benefit.
The discovery of this strange organelle in modern Plasmodium immediately suggested that there might be wa
|Contact: Jason Socrates Bardi|
University of California - San Francisco