We've seen genetic engineering used in various ways in an attempt to combat the spread of malaria by mosquitoes, including rendering the insects flightless, altering their sense of smell, making them infertile, and making them unable to spread the disease. Now another approach has been added to the list with scientists at the University of California developing a CRISPR/Cas9 technique that could stop entire mosquito populations from transmitting the malaria parasite to humans.
By bringingtogether two research teams with different areas of expertise, the researcherswere able to make three modifications to the Anopheles stephensi mosquito, a species that spreads malariawidely throughout urban India. Theoretically, the technique could render largeregions free from malaria-spreading mosquitos in a single season.
First, the researchers implantedgenes that release antibodies against the malarial parasite that usually findsa welcome host in the mosquito. Mosquitoes that carry the altered genes arethen rendered immune to the parasite, which means they can't pass it on tohumans.
Next, theresearchers created a set of genetic modifications known as a "gene drive." Thismeant that when a genetically modified mosquito mated with a wild mosquito, thegene drive would copy and paste both itself and the malaria-resistant genesinto the inheritable chromosomes of the wild mosquito.
This enabled the resistant genes to spread through the mosquito population much morequickly, because having both parents (instead of just one) carry the gene forimmunity almost doubled the chance of passing it on to their offspring.
Just in caseall this isn't sci-fi enough for you, the team also inserted a protein that gavethe offspring of modified mosquitos (wait for it….) eyes that glow red under fluorescent lights. The use of fluorescent proteins is commonly used in genetic engineering research, with the researchers saying it made the genetically modified mosquitoes easier to identify.
The twoteams came together after biologists Valentino Gantz and Ethan Bier of theUniversity of California, San Diego, announced that they had implanted a genedrive into the Drosophilia fruit fly that was successfully inherited by 95percent of the fruit fly's offspring.
Given thatmolecular biologist Anthony James from the University of California, Irvine,had recently engineered mosquitos that were immune to malaria, it made sensefor the two teams to work together to see if they could make the immunityinheritable.
The resultsof their collaboration, so far, are impressive, with. 99.5 percent of the offspringof the modified mosquitos successfully inheriting the mutation.
Theresearchers have stressed that further research is needed before they can even thinkabout conducting field trials. And theydon't suggest that their technique alone would eradicate malaria. However, alongwith existing preventative strategies, it could play a major role in helpingmake malaria eradication more sustainable.
It'scertainly quite a different approach to the idea of dramatically reducing or eliminating malaria-spreading mosquito species, which is open to problems suchas creating a "hole" in the eco-system, allowing new malaria-infected mosquito species to simplymigrate into those areas.
"Incontrast, our much more flexible system only prevents mosquitoes from carryingmalaria but can be used to do no harm to the mosquito. So it should generatethe least amount of ecological damage," Bier said.
According tothe latest UN World Heath Organization estimates, released in September 2015,there were 214 million cases of malaria in 2015 resulting in 438 000 deaths.
The team's researchwas published in the Proceedings of the National Academy of Sciences.
Source: University of California
