Dose of Radiation May Knock out Malaria

These parasites, in turn, are being used to create a new type of vaccine that shows promise of being more effective than current malaria vaccines.

The new vaccine is different from previous approaches, which have typically depended on proteins derived from only part of the parasite Plasmodium falciparum, the most lethal family of parasite that causes malaria. Using vaccines based on whole living parasites had been on researchers' minds for several decades, after they discovered that volunteers built up high levels of protection to malaria after being exposed to mosquitoes containing live, radiation-weakened parasites. But manufacturing technology only recently has been developed to the point where it is possible to effectively extract weakened parasites from their mosquito carriers to make a vaccine.

With their knowledge of measuring radiation doses for industrial processes such as medical equipment sterilization, researchers from the U.S. National Institute of Standards and Technology (NIST; Gaithersburg, MD, USA) have been providing their expertise for several years to biotech firm Sanaria, Inc. (Rockville, MD, USA), which is creating the new vaccine. In the manufacturing process, live mosquitoes containing the parasite are exposed to gamma rays. To ensure that the parasites are sufficiently weakened for the vaccine, yet remain alive; they must be exposed to a radiation dose of at least 150 Gy, but not much more. Coincidentally, this is also the dose used to delay sprouting in potatoes and onions.

One critical design issue is ensuring a relatively uniform radiation dose regardless of where the mosquito is in the chamber. Using radiation-sensitive test materials inside the chamber as well as sophisticated measuring equipment, NIST researchers mapped out the radiation dose at different parts of the chamber. They first found there was a variation in dose within the chamber, but by suggesting that the manufacturer change the position of the chamber relative to the radiation source they were able to considerably reduce this variation. This not only increases the speed of the process, but more significantly, improves the quality of the process. To be safe for human trials, all mosquitoes in the chamber must get their minimum dose of 150 Gy.

The vaccine is currently being manufactured for the anticipated human clinical trials. NIST researchers will continue to be active in the manufacturing process by doing regularly scheduled quality-assurance tests that ensure the desired dose is being delivered to the mosquitoes.


Related Links:
National Institute of Standards and Technology
Sanaria