Stanford Researchers Seek Volunteers For Malaria Vaccine Study

Main Category: Tropical Diseases
Also Included In: Immune System / Vaccines
Article Date: 18 Oct 2007 - 4:00 PDT

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Seeing children in Africa die from cerebral malaria made a lasting impression on pediatric infectious disease specialist Sharon Fei-Hsien Chen, MD. While serving in Uganda and Kenya several years ago, she often saw parents bring a sick child to the hospital only to find out that nothing could save their child.

"The doctors tell them, 'You can stay here, or you can go home, but there is nothing we can do,'" said Chen, an instructor in pediatric infectious diseases at the Stanford University School of Medicine.

Once blood cells infected with malaria parasites adhere to the capillaries of the brain, the result is swelling that kills brain cells, bringing convulsions, coma and death. "You see even just a couple of those cases and it gives you good motivation to find a vaccine," Chen said.

Chen is part of an ambitious effort to thwart malaria's stranglehold over most of the tropical world. With the Stanford-Lucile Packard Children's Hospital Vaccine Program, Chen is helping to test an experimental malaria vaccine. They are looking for healthy adults to enroll in a study to test the vaccine's safety.

According to the World Health Organization, each year more than 500 million people become severely ill with the disease and a million of them die.

Although the disease is preventable and can be treated with drugs, preventive measures such as mosquito netting are often unavailable or used incorrectly. In addition, resistance to malaria drugs, as well as mosquito resistance to insecticides, is increasing.

"One of the difficulties in developing a malaria vaccine is that the malaria parasite has a very complicated life cycle," said Cornelia Dekker, MD, professor of pediatrics and principal investigator of the Stanford trial. When an infected mosquito bites a human, it releases early-stage parasites into the victim's blood. In only a few minutes, the parasites migrate to the liver, where they transform into later-stage parasites that invade red blood cells and cause disease.

Each feeding mosquito's salivary glands can contain more than 100,000 parasites. The vaccine that Dekker and her team are testing is designed to halt these parasites in the blood before they get into the liver. "That amount of circulation time is just a couple of minutes, so that's a real challenge," Dekker said.

Nearly 100 groups worldwide are working on a malaria vaccine. What is different about this one is that its antigen, derived from the part of the parasite that triggers the immune response, is carried in a viral package.

The experimental malaria vaccine uses a type of adenovirus that does not usually infect humans, so people receiving the vaccine should not have any immune response to the virus packaging. Dekker also emphasized that people cannot get malaria from the vaccine. "This antigen is just a teeny little part of the early-stage parasite," she said.

The vaccine is produced by Crucell, a company located in the Netherlands. Favorable studies in mice and large animals led the National Institutes of Health to sponsor human testing of the vaccine, first at Vanderbilt University and now at Stanford.

The study is looking to enroll healthy volunteers ages 18 to 45 who are willing to receive three injections of the malaria vaccine into the upper arm muscle. Volunteers will make 16 clinic visits at Stanford Hospital over seven to eight months.

Participants will be given three injections of one of four doses of the malaria vaccine, or a placebo injection that contains no vaccine. A blood sample will be taken at 10 of the clinic visits. After the 16 clinic visits are completed, participants may be contacted once a year by telephone for an additional four years for safety follow-up.

Participants will receive $30 reimbursement for each regularly scheduled non-vaccination clinic visit and $60 for each vaccination visit that they complete.

Interested volunteers can contact the Stanford-LPCH Vaccine Program at (650) 498-7284, or e-mail Vaccines_Program@stanford.edu or visit the Web site at http://vaccines.stanford.edu/clinical_trials.html.

"We are trying to get a special kind of volunteer in a sense," said Dekker. "We are thinking that this might be an attractive trial for some people because, for whatever reason, control of malaria is something that is near and dear to their hearts."

Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu.

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