October 16, 2007 - By Mitzi Baker
Seeing children in Africa die from cerebral malaria made an impression on pediatric infectious disease specialist Sharon Fei-Hsien Chen, MD. While serving in Uganda and Kenya a few years ago, she was faced repeatedly with parents of a sick baby coming to the hospital only to find out there was nothing that 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, who is an instructor in pediatric infectious diseases at the School of Medicine.
Once blood cells infected with malaria parasites adhere to the capillaries of the brain, that causes 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 the stranglehold that malaria has over most of the tropical world. With the Stanford-LPCH Vaccine Program, Chen is helping to test an experimental malaria vaccine. They are looking for healthy adults to enroll in a study testing the safety of the vaccine.
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.
'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 the principal investigator of the trial at Stanford. When an infected mosquito bites a human, it releases early-stage parasites into the victim's blood. In only a few minutes, the parasites have migrated 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,' Dekker said. 'So that's a real challenge.'
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. 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 the malaria vaccine, or a placebo injection containing no vaccine. A blood sample will be taken at 10 of the visits. After the 16 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 clinic visit and $60 for each regularly scheduled non-vaccination clinic visit that they complete.
'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 Medicine integrates research, medical education and health care at its three institutions - Stanford University School of Medicine, Stanford Health Care (formerly Stanford Hospital & Clinics), and Lucile Packard Children's Hospital Stanford. For more information, please visit the Office of Communication & Public Affairs site at http://mednews.stanford.edu.