The New Strategy to Stop the Zika Virus: Gene Drives and CRISPR Technology

Active primarily in Mexico, Brazil, and other parts of South America, the Zika virus has made headlines for months since cases first popped up in April 2015. It could be linked to a spike in cases of microcephaly, a disease causing children to be born with shrunken heads. Efforts to slow or reverse the spread of the illness have been long underway. While a vaccine will take quite some time to synthesize, Brazil has taken more direct measures to stop Zika and has dispatched over 200,000 soldiers to travel door-to-door inspecting residences for mosquito breeding nests.

Yet, there is an alternative to these conventional measures, and researchers may have found it. The MIT Technology Review recently published an article titled, “We Have the Technology to Destroy All Zika Mosquitoes” that outlines CRISPR technology and the gene drives that can eliminate the Zika virus.

 

CRISPR Technology and Gene Drives

The proposed solution is called a gene drive and is made possible by CRISPR technology, otherwise known as, “clustered regularly-interspaced short palindromic repeats.” A gene drive will allow a team of biologists to create a gene to do whatever they want. A team can implant it in a population and ensure that the gene is passed on.

That last component is key. We’ve been able to manipulate genes for some time, but normally in genetics, only about half of the second generation will be born with the desired gene. Then, because anything we create will not be essential to survival, the engineered genes will soon be phase out due to natural selection. CRISPR allows us to trump this trend, and with its use, nearly every member of the second generation, and each subsequent generation, will continue to spread the engineered gene. After a few lifecycles, entire populations of creatures can be modified to our designs.

 

With that in mind, the plan is simple.

  • Using this technology, we can alter the genes of a small population of mosquitoes in a lab to make them unsuitable hosts for the Zika virus, and as a result, they cannot pass the disease by biting humans.
  • We then release the altered group of mosquitoes into the wild to breed with the natural population.
  • In a few generations, the gene that we have implanted into the population will have spread, and the Zika virus will wane as viable hosts disappear.

 

Alternatively, there is the option to destroy the mosquitoes entirely.

  • Instead of a gene to block the Zika virus, the population is implanted with a gene that only permits the mosquitoes to produce male offspring.
  • Once released, the combination of a large influx of males to a local population and a short lifespan will quickly deplete the female population in just a few generations.
  • With these mosquitoes gone, the vehicle spreading the Zika virus will also cease to exist.

 

The article from the MIT Technology Review quotes Dr. Kevin Esvelt, an Assistant Professor and researcher at MIT, stating that this technology could be ready to be deployed in as little as two years.  

 

Caveats, Concerns, and Disapproval

Gene drives can be a powerful weapon against pestilence, but there are risks. Strategies like this purport to interfere with the genetic makeup of whole populations by manipulating genes. There’s bound to be a few caveats.

 

Unforeseen Damage to the Ecosystem: Ecosystems are densely intertwined. Even though the Aedes Aegypti, the species of mosquitoes carrying the virus, is an invasive species not originally from South America, it could still have a rippling impact on the rest of the South and Central American ecosystem that we cannot predict.

 

However, scientists are split on this issue:

“I don’t think the entire ecosystem is going to collapse if you removed an invasive [species], but there is a lot of interconnectedness between species, especially in the tropics,”
— Todd Kuiken, Environmental Scientist
Woodrow Wilson Center

 

“These mosquitoes truly have little value…People in favor of eradication are going to be able to plead their case.”
— Zach Adelman, Entomologist
Virginia Tech University

 

Cross Species Contamination: Mutation is a phenomenon that just happens in genetics and biology. It cannot be predicted, and it cannot be prevented. If genes that we introduce mutate into something else or the mosquitoes become able to infect other animals, it could have sweeping consequences. Can we guarantee that our efforts can be contained to one species of mosquito?

Reversal Drives: Scientists concerned with cross species contamination and an accidental release of a gene drive are calling for the development of companion “reversal drives.” Functioning on the same principles, these drives will work to undo the effects of a gene drive. At this point, “reversal drives” are theoretical.

 

Future Potential for CRISPR Technology

A panel of the National Academy of Sciences in Washington, D.C., is set to release a report in May on the responsible uses of the technology, but even still, these recommendations are far from legislation. The potential for gene drives is near limitless, and a national discussion will need to be held to determine what we are and are not ready to pursue. That being said, this could be the beginning of some amazing things.

 

  • Malaria-Proof Mosquitoes: One of the goals powering the development of gene drives is the creation of malaria-proof mosquitoes. The exact same principles used to create mosquitoes unable to host the Zika virus can be applied to malaria. It could finally eradicate the horrific illness. 
  • Eliminate Invasive Species: Forcing the invasive population to only breed males could quickly eliminate an invasive species before it takes hold of an ecosystem and disrupts the balance. 
  • Yeast and Ethanol: Alter the genes of yeast cells, so they consume plant matter instead of sugar and produce ethanol instead of alcohol. If perfected, this could eliminate our dependence on fossil fuels. 
  • Agriculture: Wheat can be rendered invulnerable to funguses or pests can be made more vulnerable to pesticides. We can produce more food in more extreme climates.

 

“Everything is possible with CRISPR…I’m not kidding.”
Hugo Bellen, Geneticist, Baylor College of Medicine

 

For Further Reading

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