Scientists have successfully eradicated a population of malaria-carrying mosquitoes by using a radical form of genetic engineering to make females infertile – in the most advanced and largest ever test of using technology to combat the disease.
Like bringing fresh hope in the fight against one of the world’s biggest killers, the study lays the groundwork for further trials of gene-drive technology that could mean self-destructing mosquitoes within 10 years. the wild are released.
“This is a very exciting development,” said Dr Thomas Price, a senior lecturer in evolution, ecology and behavior at the University of Liverpool, who was not involved in the research. “There are still a lot of ethical and regulatory questions that need to be answered. But none of these really matter if it is impossible to build gene stations that are effective in the field. This is an important step in that. reach. ”
Despite the reduction of malaria in recent decades, there were still 229m cases of the disease in 2019, and 409,000 deaths.
Dr Drew Hammond, at Imperial College London, who led the new study, said: “Genedrift is a self-sustaining and fast-acting technology that can work alongside existing tools such as bed nets, insecticides and vaccines, and can change a game in eliminating malaria. ”
The aim of the development is to circumvent natural selection by including a set of genetic instructions that will spread rapidly through a population and pass on a certain trait – in this case infertility – much faster than could be achieved by conventional selective breeding.
The idea was first coined in 2003, but hit a roadblock when scientists discovered that their gene stations disappeared after several generations, as they introduced mutations that prevented them from spreading further. Instead of giving up, Hammond and his colleagues began looking for a better purpose to insert their gene station.
Some areas of DNA are highly conserved, which means that any mutation is likely to seriously harm their owner. Choosing one of these areas can enable gene stations for longer.
The scientists identified a crucial sex destiny gene called double sex, which is identical about individual Anopheles gambiae mosquitoes, a species responsible for most of the transmission of malaria in sub-Saharan Africa. Female mosquitoes that the gene drives in this gene are unable to produce offspring.
In 2018, Hammond’s team used the double sex drive to destroy a population of about 600 In gambiae mosquitoes housed in a small cage. Within seven to 11 generations, no more offspring were produced.
The same year, field trials were launched in Burkina Faso by the Target Malaria research consortium, including the Imperial team. This included the release of genetically modified, sterile, male mosquitoes into the wild, to test whether they could survive, and continue to be tracked – an essential step towards final field trials of gene-driven organisms, which have not yet taken place.
The new study, published in Nature communication, is another stepping stone to that goal. Hammond and his colleagues questioned whether the same gene station they tried to spread in 2018 would cause the same population to collapse in closer to the real circumstances. Such testing has been marked by the World Health Organization as a critical step before gene-drive technologies can be tested in the wild.
The scientists released relatively small numbers of modified mosquitoes in much larger indoor cages, which contain hundreds of wild-type mosquitoes of different ages, at a research facility near Siena, central Italy. The cages were designed to entice the mosquitoes to complex behaviors for mating, resting, foraging and laying eggs that would be impossible in small cages.
The researchers monitored how quickly the gene distribution spread, and looked at the 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, which within a year caused a crash of that entire population, without further human input. It is completely self-sustaining,” Hammond said. , who is also employed by the Johns Hopkins Malaria Research Institute, in Baltimore, USA.
Hammond stressed, however, that more extensive testing of gene stations and environmental risk evaluations were needed before larger field trials could take place. These may include the release of non-sterile genetically modified mosquitoes, to investigate whether they would mate with wild mosquitoes, and to what extent.
Such field trials could begin within the next few years. Assuming they were successful, Hammond said he could imagine that “within 10 years we would have a limited release of mosquitoes that run with genes on our field test site, probably in Burkina Faso”.