Scientists have used CRISPR gene editing to collapse the population of malaria-carrying mosquitoes in what could be an important turning point in the fight against the deadly disease.
A research team led by Andrea Crisanti from Imperial College London targeted the doublesex gene to spread specific genetic traits over several generations of a malaria-carrying mosquito species. Using what amounts to a genetic time bomb, scientists are able to essentially eliminate females from reproducing within seven to 11 generations. According to the findings, which were published in the journal Nature Biotechnology, this is the first time an insect population has been wiped out by manipulating its gene drive.
The idea of eradicating a disease-carrying mosquito population through gene editing is a game-changer in the battle against malaria, which kills around one million people per year, mostly in sub-Saharan Africa.
“It is estimated in the best-case scenario that with available technology and significant increase in funding, it will take another 30 to 40 years to eradicate malaria,” Crisanti told Newsweek. “Gene drive may significantly expedite the achievement of this objective.”
What’s particularly promising about the latest research is that previous attempts to use gene drives to make mosquitoes resistant to malaria have resulted in spontaneous mutations. The new experiment—in which 150 genetically edited male mosquitoes were introduced into a caged population of 450 non-altered male and female mosquitoes—did not result in any such resistance over the generations.
Despite the promise of this new breakthrough, a variety of questions still need to be answered. First and foremost is whether or not introducing genetically modified mosquitoes into a population native to the wild would yield the same results seen in a controlled lab environment. Crisianti said in a press release announcing the findings that she didn’t expect that to happen for another five to 10 years.
Another important question is what effect a population collapse would have on the larger food web.
“Past experience has demonstrated that eliminating a few mosquito species from the environment does not cause ecological havoc,” Crisianti told Newsweek. Nevertheless, there’s no precedent for this type of species-wide genetic manipulation, which is leading to caution from the researchers as well as observers.
“There are some unique dimensions to this that put us in uncharted territory,” Jennifer Kuzma, co-director of the Genetic Engineering and Society Center at North Carolina State University, told Wired. “We don’t have opportunities to learn from limited tests, that take into account different cultural and geographic landscapes, and I don’t think we’ve really grappled with these questions yet.”
Next Steps with CRISPR Research
Researchers are already attempting to address concerns. Crisanti’s research has received support from the Bill and Melinda Gates Foundation, which is spearheading the Target Malaria project. In addition to their research into genetically edited mosquitoes, Target Malaria scientists were recently granted permission to introduce a strain of genetically altered Anopheles gambiae mosquitoes into the wild of Burkina Faso. The 10,000 male mosquitoes they are releasing have been engineered with a “sterile male mutation” that prevents them from reproducing.
Although this population is small enough that it won’t have a significant impact on the fight against malaria, Target Malaria sees it as an important trust-building exercise with the local communities, as well as proof to regulators that they’re capable of tracking their research in the wild. Future experiments could include the release of a genetically edited mosquito known as the “X-shredder” that produces almost exclusively male offspring.
A lot more research into the effects of genetically modified mosquitoes needs to be conducted before we see the wide-scale use of these techniques to battle malaria and other diseases spread by mosquitoes. But it is clear that Crisianti and Target Malaria will be careful in how they proceed and present their game-changing research.
“At some point the science will be ready,” Target Malaria engagement manager Delphine Thizy told Wired. “Then it will be a matter of public acceptance and regulatory frameworks that will need to catch up.”