Thursday, May 26

Mosquitoes Genetic Engineering Test ‘May Be a Game Changer’ in Malaria Elimination | Malaria


Scientists have successfully eliminated a population of malaria-transmitting mosquitoes by using a radical form of genetic engineering to render females infertile, in the most advanced and largest test of using technology to combat the disease.

In addition to bringing new hope in the fight against one of the world’s biggest killers, the study lays the groundwork for new trials of gene drive technology that could mean the release of self-destructive mosquitoes into the wild within 10 years.

“This is a very exciting development,” said Dr Thomas Price, senior lecturer in evolution, ecology and behavior at the University of Liverpool, who was not involved in the research. “There are still many ethical and regulatory questions that need to be answered. But none of them really matter if it is impossible to build gene drives that are effective in the field. This is an important step towards achieving it. “

Despite the reduction in malaria in recent decades, there were still 229 million cases of the disease in 2019 and 409,000 deaths.

Dr Drew Hammond of Imperial College London, who led the new research, said: “Gene drive is a fast-acting, self-sustaining technology that can work alongside existing tools like mosquito nets, insecticides and vaccines, and could change the rules. of the game in achieving the elimination of malaria “.

The development aims to circumvent natural selection by incorporating a set of genetic instructions that will spread rapidly through a population and transmit a particular trait, in this case infertility, much faster than could be achieved through conventional selective breeding. .

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The idea was first floated in 2003, but hit a roadblock when scientists discovered that its gene drives disappeared after several generations because they introduced mutations that prevented them from spreading further. Rather than give up, Hammond and his colleagues began searching for a better target to insert their genetic drive.

Some areas of the DNA are highly conserved, which means that any mutation is likely to seriously harm its owner. Choosing one of these areas could allow gene drives to survive longer.

Scientists identified a crucial sex determination gene called double sex, which is identical in each individual Anopheles gambiae mosquitoes, a species responsible for the majority of malaria transmission in sub-Saharan Africa. Female mosquitoes carrying the The genetic drives of this gene are unable to produce offspring.

In 2018, Hammond’s team used the double sex genetic drive to destroy a population of around 600 A gambiae mosquitoes housed in a small cage. Within seven to 11 generations no more offspring were produced.

The same year, the Target Malaria research consortium, which includes the Imperial team, launched field trials in Burkina Faso. This involved the release of sterile male mosquitoes, genetically modified in the wild, to test whether they could survive and continue to be tracked, an essential step towards eventual field trials of gene drive organisms, which have yet to be carried out.

The new research, published in Communications from nature, is another springboard towards that goal. Hammond and his colleagues tested whether the same genetic drive they tested in 2018 would spread and cause the same population collapse under conditions closer to the real world. The World Health Organization has identified this type of testing as a critical step before gene drive technologies can be tested in the wild.

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The scientists released relatively small numbers of modified mosquitoes into much larger indoor cages that house hundreds of wild-type mosquitoes of different ages, at a research facility near Siena in central Italy. The cages were designed to attract mosquitoes to complex mating, resting, foraging, and egg-laying behaviors that would be impossible in small cages.

The researchers tracked how quickly the genetic drive spread and looked at its impact on female fertility and population decline.

“This is something that has never been achieved before: a single release of gene drive in a simulated field population, causing that entire population to collapse within a year, without further human involvement. It’s completely self-sufficient, ”said Hammond, who is also an employee of the Johns Hopkins Malaria Research Institute in Baltimore, USA.

However, Hammond emphasized that more comprehensive gene drive tests and environmental risk assessments were needed before larger field trials could be carried out. These could involve the release of non-sterile genetically modified mosquitoes, to investigate whether and to what extent they would mate with wild mosquitoes.

These field trials could begin in the next few years. Assuming they were successful, Hammond said he could imagine that “within 10 years we would have a limited release of gene drive mosquitoes at our field test site, probably in Burkina Faso.”


www.theguardian.com

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