Malaria's sweet spot

Science News,  Sept 29, 2007  

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A sugar molecule in the guts of mosquitoes is crucial in spreading the malaria parasite from person to insect to person, scientists have discovered.

After a mosquito takes blood from an infected person, parasites in that blood must bind to the inner wall of the insect's gut and then pass through it. Sugar molecules called chondroitin glycosaminoglycans cover the cells that form the wall's surface, and these molecules give the parasite a place to grab on, the research shows.

The scientists injected laboratory mosquitoes with a molecule that blocked production of these sugars. The treatment reduced by about 95 percent the number of malaria parasites that passed through the wall, the team reports online and in an upcoming Proceedings of the National Academy of Sciences.

"What is new in our work is that we found some transmission-blocking [molecules] that are not derived from the parasite itself but from the mosquito,' says lead scientist Marcelo Jacobs-Lorena of Johns Hopkins University in Baltimore.

If scientists find the protein on the parasite that binds to the sugars in the mosquito's gut, they could perhaps design a vaccine for that protein, Jacobs-Lorena says. People inoculated with such a vaccine would remain vulnerable to malaria, but their immune systems would produce antibodies that biting mosquitoes would ingest, which would then block transmission of the parasite.--P.B.

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