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THURSDAY, March 25 (HealthDayNews) -- Scientists have discovered four proteins that affect the ability of the parasite that causes malaria to survive in mosquitoes.

The finding could lead to new ways to prevent the mosquito-borne disease, which causes an estimated 2.7 million deaths worldwide each year, the researchers report.

Two of the proteins protect the Plasmodium parasite from being destroyed as it multiplies in a mosquito's gut, say researchers at the European Molecular Biology Laboratory in Heidelberg, Germany. The other two proteins, meanwhile, help the mosquito's immune system kill the parasite.

The discovery helps explain why some mosquito species transmit malaria, while others do not, say reports in two journals, Cell and Science.

There's an admittedly long road ahead before the findings can be put to practical use. But the first steps are being taken, says Mike A. Osta, a European Molecular Biology Laboratory postdoctoral fellow who is lead author of the report in the March 26 issue of Science.

"The experiments we have done have been in rodents" infected with malaria, Osta says. "The next step is to study the effects of the genes for the proteins on human malaria."

Some very basic research is under way, he says.

"At the moment, we are studying how the proteins work," Osta says. "They do not work alone, and so we are studying the proteins they work with."

What happens next will depend on the results of those studies, but some possible applications already are being considered.

"We could produce transgenic mosquitoes with the [proteins that protect the parasite] knocked out and release them into the environment," Osta says. "Or we could use chemical strategies to block or mimic the activity of different proteins."

George Dimopoulos, an assistant professor at the Johns Hopkins School of Public Health's Malaria Institute, says, "It is not going to be easy, but I believe it will be possible in the near future to create a protective mosquito by manipulating the expression levels of the different proteins."

Alister Craig, a scientist at the Liverpool School of Public Health in England and co-author of an accompanying editorial in Science, sees a longer road ahead.

"They've got a huge amount of work to do that could produce a therapy or an intervention in malarial disease," Craig says. He estimates it will take five to 10 years. But he also sees practical problems if the scientists achieve their goals.

"There is the question of whether it would ever be reasonable to release genetically modified mosquitoes," Craig says, citing a potential disruption in the balance of nature, even for a disease "that kills so many people and causes such a great financial burden."

An international study group estimated in 2002 that more than 2 billion people have malaria, and the disease causes 2.7 million deaths each year.

Malaria occurs in more than 100 countries and territories, with more than 40 percent of world's population at risk. Vulnerable areas include much of Central and South America, Africa, the Indian subcontinent, Southeast Asia and the Middle East.

Even if the environmental impact of genetically modified mosquitoes can be settled, says Dimopoulos, "how to spread this phenotype in nature would be a very complicated question."

On the scientific level, he adds, "this can be a breakthrough, the first step in the dissection of the mechanism by which malaria is transmitted."

More information

You can get advice on what to do before, during and after travel to an area where malaria is endemic from the U.S. Centers for Disease Control and Prevention and the World Health Organization.

(SOURCES: Mike A. Osta, postdoctoral fellow, European Molecular Biology Laboratory, Heidelberg, Germany; George Dimopoulos, Ph.D, assistant professor, Johns Hopkins School of Public Health Malaria Institute, Baltimore; Alister Craig, Ph.D., scientist, Liverpool School of Public Health, Liverpool, England; March 5, 2004, Cell; March 26, 2004, Science)

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