The genetic material from a malaria protozoan, a single-celled parasite that causes the debilitating disease, could be the key to a malaria vaccine.
Currently, available vaccines are made from dead or weakened versions of various viruses and bacteria to provide protection against polio, typhoid and other diseases. It has not been possible to provide immunity to conditions caused by parasites such as malaria until now.
In an article published in last week’s Science magazine, researchers at the Naval Medical Research Institute in the US state of Maryland reported that by using the new science of genetic engineering they were able to produce a vaccine for malaria that was not toxic and that produced immune responses in volunteers.
The genetic material used for the vaccine cannot cause the disease but may provide resistance against it.
“The new DNA vaccine technique is that you piggyback the DNA on a cowpox virus, for instance,” said Dr Stefan Hoyer, medical officer for the World Health Organization’s malaria project in Cambodia.
“The cowpox virus infects the cells and then multiplies. It doesn’t cause any harm but it also multiplies the DNA of the parasite. As a result the infected cells produce huge amounts of antigen and that stimulates the immune system very strongly.”
Clinical trials to test whether the induced immunity actually protects against the disease will start next summer. Similar tests already completed in animals indicate that it probably will.
DNA vaccines hold great promise because, not only can they provide protection for diseases for which very little protection is available, but they are also easy to make. They are easy to alter if the disease mutates and they do not need refrigeration.
Potential malaria vaccines have appeared on the horizon before only to disappoint, but the DNA technology has the most potential so far to eradicate malaria as well as other parasitic infections.
“You can compare it to medicine before the discovery of antibiotics and after,” Hoyer said. “With malaria, the tools that we have, the drugs and the nets are relatively less effective tools compared to a vaccine. A vaccine you may need only once.”
An eradication program based on the vaccine, however, will face significant challenges, including delivery. Money will also be needed to pay for the vaccines. The DNA vaccinations should be cheaper than traditional vaccines, but they won’t be free.
“It will be difficult in Cambodia,” said Dr Doung Soucheat, vice director of the National Malaria Center. “I don’t think the international organizations can provide the vaccine free for our people. Also, it will be hard to get the vaccine to the malaria areas because transportation is very difficult.”
There is also the risk that, after being vaccinated, people will discard their mosquito nets. Mosquitoes transmit other diseases including dengue fever and Japanese encephalitis. “Prevention is better than cure,” said Doung Soucheat. “People, when they think that this vaccine can prevent malaria, they will be exposed to the mosquitoes again. They won’t pay attention to the prevention of mosquito bites.”
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