Genetically engineered mosquitoes will try to eradicate malaria

Malaria claims about three million lives a year; A gene that prevents the Anopheles mosquito from transmitting the parasite may eliminate it

by Tamara Traubman

Malaria research is developing: scientists, who are trying to develop means to fight the disease - from which millions of people die every year - have created, using genetic engineering methods, a mosquito that is unable to transmit the parasite that causes the disease. The researchers admit that the development is in the initial stages, but it gives rise to hope that in the future scientists will be able to eradicate the disease, or significantly reduce the number of people infected with it.

Malaria has almost completely disappeared in industrialized countries, but in developing countries it remains a source of great suffering. According to the latest estimates, 300 million to 500 million people contract the disease every year - mainly in Africa - and about three million people die as a result of it each year. The alarming spread of the disease is mainly due to the failure of the plans to exterminate the malaria mosquito, the Anopheles, using pesticides, and due to the resistance to the existing drugs that the parasite has developed.

Humans become infected with the malaria parasite in a circular infection route: Anopheles mosquitoes suck the blood of an infected mammal and digest its blood. Then, the malaria parasite moves from the mosquito's digestive tract to its salivary glands. Thus, when the infected mosquito bites a person, the parasite will pass into his blood.

The idea of ​​the research team was to block the passage of the parasite from the digestive system to the mosquito's salivary glands. The head of the research team, Prof. Marcelo Jacobs-Lorna from Case Western Reserve University in Cleveland, said in a telephone interview that this way the parasite can indeed infect the mosquito, but not pass to humans. According to Jacob-Lorna, if such genetically engineered mosquitoes are released into the wild, they may multiply, gradually take over the habitats of the normal mosquitoes, and replace them.

Last year, Jacobs-Lorna and his colleagues discovered a molecule called SM1 that prevents the malaria parasite from passing from the digestive tract to the mosquito's salivary gland, and the researchers inserted the gene responsible for producing this molecule into the mosquito. Their research is published in the current issue of the scientific journal ".Nature".

In a series of experiments, Jacobs-Lorna and his colleagues showed that the probability that the parasite would be found in the salivary glands of transgenic mosquitoes, which fed on the blood of infected mice, decreased by 80%. With the exception of a few cases, these mosquitoes failed to transmit the malaria parasite to another mouse.

In a commentary article accompanying the publication of the study, Dr. Gareth List from the European Laboratory for Molecular Biology in Germany wrote that the new development was made possible thanks to the many achievements in malaria research in recent years, including the decoding of a draft genome of the Anopheles mosquito that was published a few months ago. "This is new and exciting work, and represents a new era in malaria research," he said.

However, Gareth pointed out that there is still a long way to go before the development is completed. According to him, Jacobs-Lorna used a parasite that causes malaria in rodents, "and it is not clear if (the same molecule) is also effective against human parasites." In addition, List said, before releasing the engineered mosquito into the wild, one must make sure that it will not cause ecological damage.

Jacobs-Lorna believes that if the molecule used in the current study is not effective against the parasite that causes disease in humans, other effective molecules similar to it will be found. "In the meantime", he says, "this is a proof of principle: from a scientific point of view it is possible to engineer a mosquito that will not transmit malaria".

To the possible obstacles listed, Jacobs-Lorna adds the resistance that the parasite may develop against the molecule, which makes it difficult for it to reach the salivary glands.
"To address this concern, it will be important to implant more than one gene in the mosquito, so that each gene will inhibit the development of the parasite through a different mechanism." According to him, he and his colleagues have already begun to try to identify such genes.

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