Dishearteningly diverse. malaria parasites invade red blood cells.
fighters malaria have bad news this week. A new analysis reveals that the microorganisms responsible for the disease have much greater genetic variability than previously realized, which means they might have more laps than researchers thought to escape to drugs and vaccines.
Plasmodium falciparum , the single-celled parasite that most deadly cause of four different types of malaria, gave researchers struggling since the 1970s, when it developed chloroquine resistance "wonder drug." There are ten years, scientists have found that large populations of the parasite died off between 3000 and 5000 in the last few years, creating a "bottleneck" that reduces the genetic variability of the species This led to the hope that new effective drugs could be easily developed -.. and the objections of some malaria researchers thought that the pathogen was more complex to cut through the controversy, parasitologist Xin-zhuan Su of the National Institute of allergy and infectious diseases in Bethesda, Maryland, took another look at the bug genes.
Su and his colleagues sequenced 204 genes in each of the five Plasmodium isolates from around the world - the largest survey yet. In the July 18 issue of Nature , they report that 118 genes showed at least a difference when the isolates were compared. Using these genetic differences to rebuild the Plasmodium family tree, the team believes that isolates branched off from the other there are between 100,000 and 180,000 years. Su stressed that this more accurate value for Plasmodium "age corresponds to the first explosion of the human population, where the increasing number of armed dramatically helped the parasite to diversify its genome.
In another study in the same issue, Su and his team hotspots of genetic variation on chromosome 14 of Plasmodium in 87 different isolates compared, some of them sensitive to chloroquine and other resistant to chloroquine. They found that mutations occurred most often in the gene that allows Plasmodium to pump chloroquine on itself. The remaining mutations can be grouped into four related items, suggesting that Plasmodium won the chloroquine resistance four times, once in each set genetically distinct.
The results are "bad news," says geneticist Andrew Clark populations of Cornell University in Ithaca, New York. The extent of genetic variability and Plasmodium "The history" makes you think, 'Whoa - these guys will be able to adapt quickly enough to new drugs, "Clark said these results. confirm that vaccines should target multiple aspects of parasite infection at the same time, parasitologist adds Thomas Richie of the Naval medical research Center in Silver Spring, Maryland.
Related Sites
malaria Xin-zhuan Su Genetics Section
NIAID malaria information from the World health Organization
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