Malaria vaccine tests under way.

Malaria vaccine tests under way

Human trials of a genetically engineered vaccine for malaria have just begun. "It was the most benign immunization I ever received," said researcher J.D. Chulay two days after being injected.

The vaccine consists of a protein characteristic of the malaria sporozoite, the form in which the disease-causing microorganism is carried by mosquitoes to infect new hosts. "The vaccine we are testing is probably the purest vaccine ever given to humans or animals," Chulay says. "So far [nine days after the first volunteers received injections], blood tests show the vaccine to be benign."

Chulay and his colleagues at Walter Reed Army Hospital in Washington, D.C., plan to do safety tests on 20 to 40 normal volunteers. If those trials go well, the investigators will then proceed to tests of efficacy.

Procedures to deliberately infect volunteers with malaria and then cure the disease were recently demonstrated by the Walter Reed scientists and scientists at the Unversity of Maryland Center for Vaccine Development in Baltimore, in collaboration with Ruth S. Nussenzweig at New York University in New York City. The methods are similar to those used to evaluate antimalarial drugs. Mosquitoes infected with drug-sensitive malaria parasites are placed in a container, which is then attached to the volunteer's arm. After being bitten by five infected mosquitoes, the volunteer is hospitalized and monitored for malarial infection. The disease can be cured rapidly if it is treated as soon as parasites are detected. Both research teams report success in infecting volunteers, and then in curing the illness, which may include headache and fever, in less than two days. In future tests, the scientists plan to "challenge" volunteers, by exposing them to malaria-carrying mosquitoes, at different times after vaccination.