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This article is from the In-Depth Report A Guide to Malaria

Lending a Helping Arm: Volunteers Risk Malaria to Test Vaccine

Volunteers in Seattle chance getting the disease in a bid to defeat it
anopheles-gambiae



CDC/JIM GATHANY

Researchers announced today that they are building a new facility dedicated to finding an effective vaccine against malaria, a potentially deadly disease spread by mosquitoes that annually strikes some 500 million worldwide and kills as many as one million people, mostly children in Africa. The debilitating disease was eradicated in the U.S. in 1949 (by spraying mosquitoes with the now-banned pesticide DDT) and is now only seen in this country infecting tourists, soldiers and others who contracted it in endemic regions. But over the next few years, volunteers—many, students from the University of Washington in Seattle—will risk getting the disease in the name of finding a vaccine designed to protect African children.

The PATH Malaria Vaccine Initiative (MVI) and the Seattle Biomedical Research Institute (SBRI) are teaming up to build a new facility planned to open in two years where the safety and efficacy of potential vaccines will be tested. Paid volunteers will be injected with the most promising versions and then bitten by mosquitoes carrying a  strain of malaria that can be treated with existing drugs in case the vaccine fails.

"One of the problems we have in development of malaria vaccines is to inform the decision on new vaccine candidates prior to moving to clinical trials in children in Africa," says Christian Loucq, PATH MVI director. "In Seattle, for whatever reason, there is a community here that is very prone to participating in clinical trials."

Loucq admits that some people may develop malarial symptoms, because not all of the trial shots will work. But he notes that they will be treated with existing remedies "as soon as we see parasites in the red blood cells." He also points out that new techniques, such as screening for the DNA of the malaria parasite, make detection possible before volunteers suffer the high fever, chills and vomiting associated with the disease.

Several promising vaccines will face early trials once the facility opens, including some being developed at SBRI that target the malaria-causing (Plasmodium falciparum) parasite after it invades the human liver. These vaccines fuse a molecule from a recognizable pathogen onto a protein on the surface of P. falciparum to train the human immune system to attack the parasite when it breaks out into the bloodstream.

Other promising vaccines will continue testing in the interim, such as GlaxoSmithKline's so-called RTS,S/AS02A, which employs a hepatitis B antigen. Clinical trials in Africa have shown that it protects roughly 30 percent of men and children from malaria infection, and larger, more comprehensive trials are planned. The vaccine could be available as soon as 2011 if all goes well.

But PATH MVI is hoping to achieve more. Twenty four out of 26 people bitten by mosquitoes carrying irradiated parasites proved protected from malaria infection in recent trials and a vaccine harvested from such mosquitoes salivary glands by Sanaria, Inc., is set to enter the next phase of testing with different dosages and inoculations later this year*.

"It is possible we will combine that [Sanaria vaccine] with protein-based vaccines as a prime boost. There are lots of things we are going to be in a position to test here in Seattle and later on in Africa," Loucq says. "Our target in 2025 is to have something with at least 80 to 85 percent efficacy."

*Correction: The original version of this sentence implied that the Sanaria vaccine had already proven its protective effect.

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