After decades of disappointment, U.S. and European scientists have created a synthetic vaccine that offered some protection against malaria in a small pilot test. The preliminary findings, reported in today's issue of the New England Journal of Medicine, represent significant progress toward a vaccine against a disease that kills about 2 million people a year, mainly in poor regions of Africa, Asia, and South America.
A team of scientists from the Walter Reed Army Institute of Research and the drug company SmithKline Beecham (SB) injected three different formulations of the vaccine into 46 volunteers, some of whom then received a second and third injection. Of the original volunteers, 22 agreed to be bitten by mosquitoes carrying the malaria parasite Plasmodium falciparum, as did six "control" subjects who had received no immunization. All the controls came down with malaria. Two versions of the vaccine triggered an immune response, but only one was strongly protective: 60 days after the vaccination, six of seven subjects in this group remained uninfected.
"These are very encouraging results," says Lee Hall, a parasitologist at the National Institutes of Health. "It's a significant achievement," he says, because the volunteers were protected against the same strain of falciparum that was used to create the synthetic antigen in the vaccine, a scientifically persuasive outcome. Earlier attempts to create a vaccine ended in frustration or produced mixed results that remain controversial.
The main ingredient in the new vaccine is an artificial version of a protein found on the surface of the infectious stage (the sporozoite) of falciparum, the most lethal of four types of malaria parasite. To boost the immune system response, SB scientists added other ingredients to the sporozoite concoction, including a hepatitis virus protein.
Despite the favorable lab test, "there's a lot of work to be done yet," says SB spokesperson Rick Koenig. Researchers must now determine how long the immunity created by this vaccine lasts and whether the same technique can be used to protect against other parasite strains.