Biology

Malaria-resistant mosquitoes engineered using CRISPR

The gene-editing tool CRISPR/Cas9 has been used to engineer malaria-resistant mosquitoes
The gene-editing tool CRISPR/Cas9 has been used to engineer malaria-resistant mosquitoes
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The gene-editing tool CRISPR/Cas9 has been used to engineer malaria-resistant mosquitoes
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The gene-editing tool CRISPR/Cas9 has been used to engineer malaria-resistant mosquitoes

Swatting at mosquitoes is a great start, but if we really want to cut down on the hundreds of millions of malaria cases they cause every year, we're going to need some more effective weapons. Now, researchers from Johns Hopkins have used the CRISPR/Cas9 gene editing tool to engineer mosquitoes that are highly resistant to the malaria parasite, by deleting one specific gene.

According to the latest report from the World Health Organization, there were 216 million cases of malaria in 2016, resulting in 445,000 deaths. Female Anopheles gambiae mosquitoes are the primary culprit, and over the last few years scientists have engaged in all kinds of genetic warfare against the parasites and the insects that spread them.

In 2011, a UC Irvine team modified mosquitoes so that females of the species couldn't fly. They would die where they hatched, while the males would fly off, mature and mate with wild females which would unknowingly pass the deadly mutation down to their offspring. Other genetic tweaking turned the insects' immune systems against the malaria parasite, made mosquitoes unable to sniff out humans, or crippled larvae by silencing crucial development genes.

The new study, conducted by researchers at Johns Hopkins Bloomberg School of Public Health, targeted a gene called FREP1. This gene encodes for a specific immune protein that, for reasons not fully understood, helps the malaria parasite survive in the mosquito's gut. By snipping out FREP1 using the genetic scissors of CRISPR/Cas9, the team was able to reduce the likelihood of the malaria parasite surviving long enough to mature to the stage where it can harm humans.

"Our study shows that we can use this new CRISPR/Cas9 gene-editing technology to render mosquitoes malaria-resistant by removing a so-called host factor gene," says George Dimopoulos, senior author of the study. "The resistance to malaria parasites that's achieved by deleting FREP1 is remarkably potent."

The technique was able to reduce the number of mosquitoes infected with malaria, and the researchers also found no trace in the bugs' saliva glands of sporozoites – the stage of the parasite that is transferred to humans through the bite.

The genetic edit wasn't perfectly neat though. The team found that the engineered mosquitoes developed more slowly than their natural counterparts, were less likely to feed on blood and laid fewer eggs that were less viable. If the modified mozzies were released into the wild in this state, natural selection could wipe them out before they got the job done.

"We're now making mosquitoes in which FREP1 will be inactivated only in the adult gut," says Dimopoulos. "We predict that when we do that, the mosquito won't suffer the same fitness costs."

Once those kinks are ironed out, the genetically-modified mosquitoes could be released into the wild to spread their malaria resistance through the natural population. The researchers think that this could be a viable strategy, since the gene edits they've performed don't impact the insects' ability to survive and breed.

"If you could successfully replace ordinary, wild-type mosquitoes with these modified mosquitoes, it's likely that there would be a significant impact on malaria transmission," says Dimopoulos.

The research was published in the journal PLoS Pathogens.

Source: Johns Hopkins

4 comments
xs400
So the idea is not to eliminate the pest that keeps biting people and making them miserable, but only to keep people alive so they can continue be victims. Of course, someone will say that eliminating the mosquito would be bad for nature/environment because...
Brian M
The big danger is the unknown impact on what it will do to the mosquito/parasite relationship. Could the malaria parasite evolve/mutate into something we can't combat. i.e. Like bacteria can become resistant to antibiotics Could be a great idea or a disaster - great care required!
Marlen
The reason simply killing all mosquitoes is not a great idea is do to the 'cascade' effect. Similar to how DDT infected insects which where then eaten by ducks which where then eaten by Peregrine falcon ... thus resulting in fragile eggs and the near eradication of the Peregrine falcon. If you eliminate mosquitoes it _will_ have a cascade effect. What that effect is I don't have a definite answer but I predict it will go something like this: No mosquitoes == all species that feed on mosquitoes as a primary food source will starve and become extinct. No mosquito eaters == no species that feed on those species. and so on. This will probably eventually have a direct effect on the plant life in the surrounding area. When the plant life is effected ... it will effect humans.
Nik
From another NA article; https://newatlas.com/crispr-gene-editing-causes-mutations/49762/ ''In examining the entire genome from the CRISPR-treated mice, they found that the tool had successfully corrected the specific gene they were targeting, but it also potentially caused a great deal of other genetic changes. In two CRISPR-treated animals, more than 100 large gene deletions or insertions and over 1,500 single-nucleotide mutations were identified.'' The parable of ''Pandora's box'' comes to mind, amongst others. Blindly hacking genomes around could also produce some highly undesirable mutations in the mosquitoes, that could potentially produce an entirely new threat to humans. Similar perhaps to the 'killer bees' debacle.
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