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Navy Medicine Scientists Begin Malaria Vaccine Trials

Navy NewsStand

Story Number: NNS090704-19
Release Date: 7/4/2009 5:45:00 PM

By Mass Communication Specialist 1st Class(SW) Arthur N. De La Cruz, Navy Medicine Support Command Public Affairs

SILVER SPRING, Md. (NNS) -- Naval Medical Research Center (NMRC) began testing a new malaria preventive vaccine May 25-26 at its Bethesda location at the National Naval Medical Center.

The first immunizations for the new PfSPZ (Plasmodium falciparum Sporozoite) vaccine will be administered to male and non-pregnant female volunteers who provide written informed consent and meet the enrollment criteria, according to Capt. Judith E. Epstein, M.D., NMRC's Clinical Trials Team, U.S. Military Malaria Vaccine Program director.

The trial is primarily funded by PATH Malaria Vaccine Initiative (MVI), a branch of the Bill and Melinda Gates Foundation. Additional support is also provided by the Military Infectious Diseases Research Program (MIDRP).

The milestone trial takes place 66 years after the U.S. military began its campaign against malaria in the Pacific theatre during WWII.

Though advancements have been made in combating malaria, the success of these trials will result in a more effective weapon in the war against malaria.

"Historically, malaria has been the largest cause of military casualties during deployments to tropical areas," said Capt. Tom Richie, M.D., director of NMRC's Malaria Program. "Malaria took a heavy toll in lives and lost man-hours in WWII and the conflicts in Korea and Vietnam, and there is ongoing exposure to malaria in Iraq."

The vaccine is based on human studies that began in the early 1970s during which irradiated, malaria-infected mosquitoes fed on volunteers. Although the parasites injected by these mosquitoes are able to invade the livers of these volunteers, irradiation makes the parasites unable to mature, multiply or colonize red blood cells and cause the clinical illness malaria. The volunteers in these studies, having been immunized by the bites of the radiation-attenuate parasites, were protected against malaria infection when non-irradiated, highly infectious mosquitoes were allowed to feed on them.

The biotechnology company Sanaria, which serves as the sponsor for the trial, has now developed an irradiated sporozoite vaccine that meets criteria required by the Food and Drug Administration (FDA) and can be delivered by needle and syringe rather than by mosquito bite.

This biotechnology breakthrough now makes the irradiated sporozoite vaccine practical for general use.

Because this is the first time the vaccine is being tested in people, the initial trial is being conducted as a dose-escalation trial, testing three different doses of the vaccine to identify any possible side effects and to determine the effectiveness of different dosages of the vaccine for preventing malaria.

"We're building up to higher doses for safety reasons because this is the first time we're introducing it to humans," said Epstein.

Volunteers will be given doses of the vaccine four times, one month apart. Group One volunteers will receive a low dose of the vaccine, Group Two volunteers will receive a medium dose of the vaccine, and Group Three candidates will receive the highest dose.

After the immunizations, volunteers will be monitored for vaccine immunogenicity - the ability of the vaccine to activate the human immune system - and any possible side effects. Conclusions from the monitoring period must be submitted to a safety monitoring committee – a local group of experts in the field – and the Food and Drug Administration, which will determine the safety of proceeding with the testing.

Three weeks after the fourth dose, immunized volunteers, along with non-immunized volunteers, or controls, will be challenged by being exposed to mosquitoes infected with a strain of malaria that is sensitive to chloroquine. This way the investigators can tell whether the vaccine actually prevented the volunteers from developing malaria infection.

Once data has been collected and submitted to the safety monitoring committee from Group One, Two and Three, Group Four volunteers will then receive the vaccine at the highest dose. After the fourth dose, however, these volunteers will be monitored over the next six months to ensure the radiation-attenuated sporozoites comprising the vaccine cannot cause malaria illness in the vaccinated recipients.

If the vaccine is effective in less than 80 percent of any of the first three groups, Group Four volunteers will then receive a fifth and sixth dose before being challenged. This will give the investigators the opportunity to see whether the additional "booster" doses increase the effectiveness of the vaccine.

If the vaccine is effective in 80 percent or better of the immunized volunteers in Groups One, Two and Three, Group Four will not receive the fifth and sixth doses, since the vaccine would have achieved its target effectiveness with just four doses.

Group One and Three will be tested at NMRC, and Groups Two and Four will be tested at the University of Maryland.

For more news from Navy Medicine Support Command, visit www.navy.mil/local/nmsc/.