Researchers at the National Institutes of Health have developed an experimental vaccine that could, theoretically, eliminate malaria from entire geographic regions, by eradicating the malaria parasite from an area's mosquitoes.

The vaccine, so far tested only in mice, would prompt the immune system of a person who receives it to eliminate the parasite from the digestive tract of a malaria-carrying mosquito, after the mosquito has fed upon the blood of the vaccinated individual. The vaccine would not prevent or limit malarial disease in the person who received it.

An article describing this work was published on the Web site of "Proceedings of the National Academy of Sciences". The vaccine was developed with conjugate technology, which joins or "conjugates" molecules the immune system has great difficulty recognizing to molecules the immune system can recognize easily. Primed by the conjugate vaccine, the immune system begins making antibodies immune proteins that target specific molecules. The antibodies then eliminate molecules the immune system would fail to detect.

"With conjugate technology, NIH researchers have developed effective vaccines against such scourges as Haemophilus influenzae type B meningitis and typhoid fever," said Elias A Zerhouni, MD, director of the National Institutes of Health. "The experimental malaria vaccine shows great promise for combating a terrible disease that exacts a devastating toll on the world's children."

The vaccine was developed by researchers in the National Institute of Child Health and Human Development's Laboratory of Developmental and Molecular Immunity, in partnership with researchers in the Malaria Vaccine Development Branch of the National Institute of Allergy and Infectious Diseases (NIAID), and the Biotechnology Unit of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Some of the Plasmodium cells, however, transform into gametocytes -- the sexual forms of the parasite that are equivalent to sperm and eggs. Fertilization takes place in the mosquito gut, after which the parasite imbeds itself in the gut lining. There, it passes through discrete stages, before migrating to the insect's salivary glands, where it is passed on to the next host through a mosquito bite.