By Emma Patten-Hitt

NEW YORK (Reuters Health) - Researchers have discovered a protein that appears to be essential for the survival of the parasite that causes sleeping sickness and possibly other disease-causing parasites as well.

The finding could lead to new treatments for diseases that collectively kill over one million people a year, according to researcher Dr. Kenneth Stuart from the University of Washington in Seattle.

Sleeping sickness is caused by the parasite Trypanosoma brucei, which is spread by the tsetse fly in Africa. The disease results in fever, chills and headaches, followed by weakness, excessive sleepiness and, sometimes, death.

The discovery is reported in the February 15th issue of Sciencexpress, a publication of the journal Science.

The protein is involved in a process called RNA editing. The process allows the parasite to switch between two different ways of using energy, which is essential for its survival once it infects its host. By targeting this process, researchers hope to develop drugs that will kill the parasites.

``These are the first experiments that have definitively identified this machinery,'' Stuart told Reuters Health. ``The existence of RNA editing was not anticipated, because we could not understand why there would be a process like this,'' he said. ''It was also surprising that it would be essential in the infective stage (when the parasite infects humans or animals),'' he added.

The process may occur in a whole group of parasites, according to Stuart, not only the African trypanosomes (such as T. brucei), but other parasites including the one that causes Chagas' disease, which results in fever and enlargement of the lymph nodes, and a group of parasites that cause leishmaniasis--a disease spread by bloodsucking sandflies.

RNA editing is unlikely to take place in a similar form in humans, however.

``Parasites diverged from the lineage that led to humans a very long time ago, and so it is possible that these genes were retained, but that they became modified through evolution,'' Stuart said.

The drugs currently on the market to treat these parasitic diseases are highly toxic and not very effective, Stuart noted. ''We will be looking for the possibility that these could be targets for chemotherapy,'' he said.

SOURCE: Sciencexpress 2001;1126:1-3.