Mosquito DNA modified to prevent the spread of malaria New Scientist

By changing a gene, malaria mosquitoes die before malaria parasites can develop in their bodies. This could completely stop the spread of the deadly parasite, according to laboratory research and computer modeling.

Due to genetic modification malaria parasites develop less rapidly, and the modification also shortens the life of mosquitoes. As a result, they die before they can transmit the disease.

According to laboratory studies and computer modeling, this could completely stop the spread of the deadly parasite Giorgio Cristoforo, professor of infectious diseases and immunity at Imperial College London and part of the research team. “The combination of these two effects will kill malaria transmission,” he says.

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In order for this approach to work, a so-called gene pressure must be used, which means it is needed genetic modification it spreads in wild mosquito populations. Through this mechanism, all offspring inherit a specific piece of DNA, where usually only half of the offspring inherits the DNA. Due to genetic pressure, that piece of DNA spreads over the entire population, even if the mutation has negative consequences for the mosquito.

captivity

Artificial genetic printing has never been used in nature, although natural versions exist. A CRISPR-based gene pressure has already been successfully tested on captive mosquitoes.

Researchers in Tanzania are now modifying local mosquitoes, in the same way as researchers in London, to see how modification works against local malaria parasites. If these adjustments are successful, the teams will want to work together to conduct field trials. For the time being, they keep the tests inside the walls of the laboratory. “We don’t publish anything,” says Christophides.

The new method is based on the fact that malaria parasites take ten to twelve days to develop inside the mosquito’s body and reach the salivary glands. Only then can mosquito bites infect people. But living in the wild Anopheles Gambiamosquitoes, which can carry malaria, usually only for ten days.

Protein vs Parasite

“So you can interrupt the entire transmission cycle by slowing down parasite development,” says Christophides. To achieve this, his team began working on genetic modification a A. gambiaemosquitoes, causing intestinal cells to secrete two small proteins that have been shown to slow the development of the parasite. One of these proteins comes from African clawed frogs, the other from honey bees.

The team has already shown that it takes a few more days to detect malaria parasites in infected and modified mosquitoes. The genetic change also shortens the mosquito’s lifespan by a few days, says Cristophides. This reduces the chance that a mosquito will survive long enough to become contagious.

Evolution as an obstacle

There are two potential problems with this approach. As gene pressure further spreads the modification, there is a risk that malaria parasites develop resistance to the two proteins. To avoid this, it’s important to spread the change as widely as possible, says Christophides. The faster a parasite population collapses, the less chance there is for resistance to develop through evolution.

Furthermore, it is possible that mosquitoes evolve in such a way that gene pressure no longer works. It should therefore be designed in such a way that this risk remains minimal, says Christophides.

Other research groups are also working on other versions of gene pressure that can wipe out mosquito populations, such as making all female offspring sterile while males remain fertile and spread the genetic pressure.

Kill or be killed

You could also use these two approaches together. Before the gendruk killer, which wipes out the population in one area, followed by genetic pressure that prevents survivors or mosquitoes from other areas from spreading malaria. “We believe they can both contribute something,” says Christophides.

Millions of genetically modified male mosquitoes are already being released in Brazil to reduce the number of wild mosquitoes. These mosquitoes carry a gene that kills all the offspring of the females they mate with. There is still no evidence that this gene persists in nature for long periods of time.

Malaria still kills half a million people every year, mostly children. Last year there was a malaria vaccine approved for the first time. A second may follow shortly, but these vaccines are not yet equally effective in all cases.

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