Analysis Identifies Common Genetic Core for Trio of Parasites

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Scientists have successfully sequenced the genomes of three deadly parasites that together threaten half a billion people annually around the globe. According to reports published in the current issue of the journal Science, the parasites responsible for African sleeping sickness, Chagas's disease and leishmaniasis--illnesses with very different symptoms--share a core of a few thousand genes. Scientists hope that the results will prove useful for identifying novel drug or vaccine targets.

The three parasites, which are passed on to humans through very different vectors, are from the family Trypanosomatidae and look similar under a microscope. In addition, the new genetic analyses identified 6,200 core genes that the so-called TriTryps share, which represent about 70 percent of their total DNA. But the international research teams also identified important ways in which they differ and discovered that the genes unique to each organism are mostly located near the ends of chromosomes. "Thanks to these studies, scientists are now much closer than they were five years ago to developing effective drugs against these terrible diseases, " remarks Najib El-Sayed of the Institute for Genomic Research in Rockville, Md. For therapeutic purposes, the scientists say their focus will be on genes that are similar for all three, but different from human genes.

The results indicate that T. brucei, which causes sleeping sickness, has the least overall metabolic capacity, whereas leishmania major has the greatest. The Chagas's disease parasite T. cruzi, meanwhile, has some 1,300 genes that may help it better evade a host's immune system. "Now that the genes of parasites are mapped out, it's much easier to identify genes that are critical for parasite survival," explains co-author Peter J. Myler of the Seattle Biomedical Research Institute. "Genes encoding proteins that are involved in critical biological processes often serve as drug targets."

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