This is the VOA Special English Health Report
Malaria control efforts currently depend on things like chemically treated bed nets and spraying against mosquitoes. But scientists keep trying to find other ways to prevent the disease.
A number of vaccines remains under development. Most contain genetically engineered versions of a few proteins from the Plasmodium parasite. Plasmodium is the organism that causes malaria. Those modified proteins are designed to get the body’s defenses to launch an immune response against the Plasmodium. But the parasite contains thousands of proteins.
Another experimental vaccine includes a deactivated version of the entire parasite. Robert Seder is a researcher at the National Institute of Allergy and Infectious Diseases, near Washington. “So instead of picking out one or two or three genes, you have the potential for what we call breadth — generating an immune response that would be broad rather than narrower.”
Radiation is used to weaken the parasite so it cannot make sick people or get spread by a mosquito. To make the vaccine, scientists use the parasite at a time in its growth when the organism is called a sporozoite.
This idea has been known since the nineteen sixties. But Mr. Seder says a discovery by a researcher at a vaccine company cleared the way for progress.
“The major breakthrough here was that my collaborator, Stephen Hoffman at Sanaria, developed a method where he could isolate the sporozoites and purify them so that they could administer it as a vaccine to humans. And no one thought that was possible.”
But no one knew either if the weakened sporozoites would activate the immune system to protect against malaria. So researchers tested it on volunteers and found that it was safe. But it was not very effective. Only two out of forty-four volunteers were protected when bitten by malaria-infected mosquitoes.
To find out why, the researchers tested the vaccine on laboratory animals. They decided that the problem was the way the vaccine had been given to the volunteers. It was injected into the skin, to simulate the bite of a mosquito. Mr. Seder says it would have been more effective if it had been given directly into the blood.
However, vaccines are generally given by mouth or injected into the skin or muscle. Having to inject it into the blood could make vaccination programs more difficult if the vaccine is approved for general use.
For now, more testing is needed. A report on the testing appeared in the journal Science.
For VOA Special English, I’m Carolyn Presutti.
Words in This Story
malaria – n. a disease that you can get from the bite of a particular type of mosquito causes periods of fever and makes you shiver and feel very cold. It is common in many hotter parts of the world.
parasites – n. an animal or plant that lives on or in another animal or plant of a different type and feeds from it
defense – n. the ability to protect against attack or harm, or something used to protect against attack or harm
immune response – n. the reaction within the body that is caused by antigens and results in the production of antibodies that can fight disease by killing the bacteria or viruses that cause it
experimental – adj. relating to tests, especially scientific ones
radiation – n. a form of energy that comes from a nuclear reaction and that can be very dangerous to health
breakthrough – n. an important discovery or event that helps to improve a situation or provide an answer to a problem
collaborator – n. a person who works together with others for a special purpose
simulate – v. to create conditions or processes similar to something that exists
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