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Malaria vaccine, which injects live parasites into patients shows remarkable success

By Catholic Online (NEWS CONSORTIUM)
August 9th, 2013
Catholic Online (www.catholic.org)

A new malaria vaccine which is being developed in the U.S. has protected 12 out of 15 patients from the disease. When administered in high doses, the vaccine has shown promising results in early stage clinical trials. The vaccine's method is highly unique as it involves injecting live but weakened malaria-causing parasites directly into patients to trigger immunity.

LOS ANGELES, CA (Catholic Online) - According to lead author Dr. Robert Seder, "We were excited and thrilled by the result, but it is important that we repeat it, extend it and do it in larger numbers." Seder is affiliated with the Vaccine Research Center at the National Institutes of Health in Maryland.

It's a longstanding notion that exposure to mosquitoes treated with radiation can protect against malaria. Studies have proven, however that it takes more than 1,000 bites from the insects over time to build up a high level of immunity, making it an impractical method of widespread protection.

A U.S. biotech company called Sanaria has taken lab-grown mosquitoes, irradiated them and then extracted the malaria-causing parasite (Plasmodium falciparum), all under sterile conditions. The still-living if weakened parasites are then counted and placed in vials, where they can then be injected directly into a patient's bloodstream.

This vaccine candidate is called PfSPZ. Researchers then looked at a group of 57 volunteers for the trial vaccine, none of whom had had malaria before.

Forty of the 57 received different doses of the vaccine, while 17 did not. The test subject were then all exposed to the malaria-carrying mosquitoes. Researchers then discovered that for the participants not given vaccine, coupled with those given low doses, almost all became infected with malaria.

For the small group given the highest dosage, only three of the 15 patients became infected after exposure to malaria.

"Based on the history, we knew dose was important because you needed 1,000 mosquito bites to get protection - this validates that," Seder says.

"It allows us in future studies to increase the dose and alter the schedule of the vaccine to further optimize it. The next critical questions will be whether the vaccine is durable over a long period of time and can the vaccine protect against other strains of malaria."

The fact that the vaccine had to be injected into the bloodstream rather than into or under the skin made delivery more difficult.

"They are clearly very early stage trials in small numbers of volunteers, but without question we are extremely encouraged by the results," Dr. Ashley Birkett, from the Path Malaria Vaccine Initiative, said.

According to the latest figures from the World Health Organization, there were an estimated 219 million cases of malaria in 2010 and an estimated 660,000 deaths.

Malaria kills about 600,000 people annually and infects more than 200 million.

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