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Researchers Develop Experimental Malaria Vaccine In Mice

May 3, 1991

WASHINGTON (AP) _ A vaccine based on two key proteins in the malaria parasite has been found to give total protection for laboratory mice and may be an important step toward a more effective human vaccine.

Researchers at the Naval Medical Research Institute and the National Institutes of Health report today in the journal Science that a vaccine that combines two types of protein carried by the malaria sporozoite prompted the mouse immune system to make powerful antibodies against the disease.

The researchers said in Science that earlier vaccines, based only on a protein called CS, which is on the outer surface of the malaria sporozoite, has provided only marginal protection when used in human vaccines.

Though the CS-based vaccine triggers some antibody production by the immune system, these are not enough to give complete immunity to the disease.

In laboratory experiments with mice, the researchers combined the CS protein with one called SSP2 which is also part of the sporozoite.

A vaccine including the two proteins was then injected into mice and the lab animals were then exposed to malaria.

″Complete protection was demonstrated after immunization. ...″ the researchers said in Science, even though the mice were exposed to high levels of the malaria parasite.

″The studies identify the components and provide a compelling rationale for the development″ of a human malaria vaccine, the authors said.

Malaria, which affects about 300 million people in the world annually, is carried by the Anopheles mosquito. When an infected mosquito takes blood from a victim, it introduces into the bloodstream the malaria sporozoite, a one- celled parasite. The parasite multiplies in the liver and then erupts back into the blood stream with millions of new parasites. The disease can cause chills, fever, headache, anemia and, in severe cases, death.

The disease occurs mostly in tropical areas, where the mosquito is most common. Malaria is treated by a number of drugs, such as chloroquine and quinine, but some forms of the disease are resistant.

Co-authors of the study were Srisin Khusmith, Yupin Charonvit, Martha Sedegah, Richard L. Beaudoin and Stephen L. Hoffman of the Naval Medical Research Institute, and Sanjai Kumar of NIH.

Science, which published the study, is the journal of the American Association for the Advancement of Science.

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