WASHINGTON (AP) - A vaccine made from the milk of genetically engineered mice has been shown to prevent monkeys from developing malaria. The same vaccine produced in goat's milk could protect millions from malaria, a major killer of African children, scientists say.

Researchers at the National Institute of Allergy and Infectious Diseases said Monday that the study was a laboratory experiment to prove that a vaccine against malaria could be made cheaply by changing the genes of milk producing animals.

Obtaining malaria vaccine from milk could be a key step in controlling malaria in the poorer countries where the mosquito-borne infection hits the hardest, said Anthony Stowers, a NIAID malaria researcher and the first author of the study appearing this week in the Proceedings of the National Academy of Sciences.

"A herd of several goats could conceivably produce enough vaccine for all of Africa," Stowers said.

Dr. Philip J. Rosenthal, a malaria expert at the University of California, San Francisco, said the NIAID study is "an important advance" toward a cheap malaria vaccine, but the study still leaves many unanswered questions about the vaccine itself.

"What makes this study important is not the vaccine part, but the fact they have produced this antigen (a protein that can be used as a vaccine) in milk," said Rosenthal. "That is very impressive."

In the study, Stowers and his colleagues inserted into the DNA of mice embryos some genes that would cause the animals' mammary glands to later produce a protein known to block the spread of malaria parasites in the blood.

The embryos were put into the wombs of mother mice, carried to term and were born. When the young animals reached adulthood, the females among them were allowed to lactate. The researchers recovered this milk with small syringe-like breast pumps and used standard lab techniques to purify the anti-malaria proteins.

These vaccine proteins were then injected into six small Aotus monkeys. Seven other monkeys were injected with a placebo protein.

Later, all the monkeys were injected with a killer concentration of the Plasmodium falciparum malaria parasite.

Stowers said that five of the six monkeys injected with the milk-produced vaccine did not develop malaria. The one monkey that got sick with the disease was treated and recovered.

Among the control animals, all became sick with malaria, but recovered after treatment

Stowers said that the genetic manipulation technique has now been done on a herd of goats and preliminary tests show that they, too, will produce the malaria vaccine in their milk. He said the goats are expected to begin natural lactation this summer.

"It looks like the ...(vaccine production) level is as good as we got with mice," he said.

When the goats start naturally producing milk in June, Stowers said the researchers will purify the vaccine and then test it against malaria in monkeys. If it works, he said the group hopes to start human trials using the goat-produced vaccine in 2003.

If the technique works, Stowers said it would make it possible for a small herd of goats to make enough vaccine to rescue a whole generation of African children from malaria.

"A single gallon of goat milk could produce 40,000 doses of vaccine," he said.

Right now, about 300 Africans, aged birth to five, die every hour from the disease. It is estimated that up to 500 million Africans are infected with malaria annually and up to two million, mostly children, die.

"In addition to the death it causes, malaria is a huge burden on the budgets of the some of the poorest countries of the world," said Stowers.

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