A vaccine against one of the world's leading killers could one day be manufactured by livestock, researchers report. According to a study released today by the Proceedings of the National Academy of Sciences, scientists have developed mice that secrete malaria vaccine proteins into their milk. The purified experimental vaccine protected 80 percent of monkeys subsequently exposed to a lethal dose of the malarial parasite.

Anthony Stowers and Louis Miller of the National Institute of Allergy and Infectious Disease and their colleagues created two mouse strains, each genetically engineered to produce large quantities of a surface protein worn by the malarial parasite Plasmodium falciparum. To ensure that the proteins would come out in the animals' milk, the team designed the so-called transgenes that make these proteins to switch on in the cells that line the mammary glands. Subsequent tests aimed at evaluating the ability of the proteins to stave off malaria yielded dramatic results: whereas only one of five vaccinated monkeys succumbed to the scourge, seven out of eight unvaccinated ones had to receive treatment for virulent malaria.

Looking forward, the researchers hope to produce similar results using larger animals such as goatsa goal that preliminary results indicate is achievable. "A vaccine must not only be effective, it must be cheap to manufacture if it is to be used in those countries hardest hit by malaria," Stowers comments. "Using transgenic animals to achieve both ends is an exciting possibility. If it works, a herd of several goats could conceivably produce enough vaccine for all of Africa."