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Sunday, 31 December, 2000, 00:09 GMT
Scientists 'block malaria'
Red blood cells
Malaria infects the red blood cells
Scientists are developing a technique that could prevent the spread of malaria infection around the body of a patient who had contracted the parasite.

They believe it could be possible to trap infectious malaria particles and keep them imprisoned until they deteriorate and no longer pose a threat.

The technique involves preventing the infectious particles from bursting out of their protective sacs.

Research suggests this can be achieved by blocking the activity of an enzyme called protease.

Malaria afflicts as many as 500 million people world-wide and is responsible for the death of two million children each year.

Malaria parasites initially infect the red blood cells.

Once inside a cell, they envelop themselves in a portion of the blood cell membrane, which forms a protective sac called the parasitophorous vacuolar membrane (PVM).

The parasites then reproduce to form clusters of infectious merozoites.

These merozoites eventually burst out of the cell and infect the bloodstream.

Dr Daniel Goldberg and his colleagues at the Washington University School of Medicine have been investigating this process.

Red blood cells

The scientists treated cultures of red blood cells infected with malaria parasites with a drug called E64 that specifically blocks the activity of certain proteases.

They found this blocked the release of the merozoites into the bloodstream. Instead, closer analysis showed that they had been trapped within the PVM.

Dr Goldberg said: "We concluded that this protease inhibitor treatment seemed to block the parasites at a particular stage in the exit process.

"In the E64-treated cultures, we found that the merozoites could still get out of the red blood cell, but they couldn't get out of the sacs.

"This told us that there are two steps in the process by which these parasites exit the host red blood cell, and that the second step requires a protease."

The researchers once the protease inhibitor was removed, the malaria particles regained the ability to cause infection.

Dr Goldberg said further work was needed to identify the specific proteases involved in rupturing the red blood cells.

This would potentially enable scientists to develop drugs to stop the parasites getting out of their sacs and multiplying.

Malaria kills up to two million people each year. Over 90% of deaths are in Africa and two-thirds are among children.

The mosquito-borne disease causes high fever, muscle stiffness and sweating. It is the most prevalent tropical disease in the world.

More than 40% of the world's population live in countries where malaria is endemic.

Drugs are used to treat victims but climate change, social instability and increased resistance to pesticides and treatments have hampered the battle against the illness.

The research is published in the Proceedings of the National Academy of Sciences.

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