Gene Drive: Possible Solution for Zika Virus?

Janani Ravikumar
Staff Writer

Zika virus, what started as a relatively unknown mosquito-borne disease in Africa and a few Pacific islands, that occasionally produced very mild symptoms, has become a global emergency. It has quickly spread through South, Central and North America and has links to the neurological birth disorder, microcephaly. Now, scientists everywhere are desperate to find some way to curb this outbreak.

One of the more controversial solutions would be able to completely wipe out the mosquito containing the Zika virus, Technology Review reports. This technology, a “gene drive,” relies on the genome editing tool, CRISPR, to force a genetic change to spread through a population as it reproduces. So far, this technology has only been demonstrated last year in yeast cells, fruit flies and a type of mosquito that transmits malaria. If deployed, this gene drive could theoretically drive Aedes aegypti, the mosquito population responsible for Zika virus, to extinction.

According to Gizmodo, CRISPR is a naturally-occurring defense mechanism found in a wide variety of bacteria. By repeating DNA sequences to match that of the viruses that prey on these bacteria, CRISPR keeps bits of dangerous viruses close so that it can recognize and defend against them. A set of enzymes called Cas, short for CRISPR-associated proteins, precisely snip DNA and slice invading viruses. The genes that encode for Cas are conveniently located near the CRISPR sequences.

“As the CRISPR region fills with virus DNA, it becomes a molecular most-wanted gallery, representing the enemies the microbe has encountered,” said columnist Carl Zimmer in Quanta Magazine. “The microbe can then use this viral DNA to turn Cas enzymes into precision-guided weapons. The microbe copies the genetic material into an RNA molecule. Cas enzymes then take up one of the RNA molecules and cradle it. Together, the viral RNA and Cas enzymes drift through the cell. If they encounter genetic material from a virus that matches the CRISPR RNA, the RNA latches on tightly. The Cas enzymes then chop the DNA in two, preventing the virus from replicating.”

Theoretically, with CRISPR, it should be possible to modify the genomes of any animal, including humans, Gizmodo reports. It could potentially cure any genetic disease, and if the technology becomes more widespread, it could even lead to designer babies.

However, there are some ethical concerns to resorting to a gene drive, according to NPR. Though gene drives could potentially fight other diseases such as malaria, West Nile, dengue fever and lyme disease, they could also upset the delicate balance of an ecosystem, by destroying other species, causing new diseases to to emerge or prompting existing illnesses to spread to new places. In an even scarier worst case scenario, gene drives could also be used as a new tactic for biological warfare.

“If any group or country wanted to develop germ warfare agents, they could use techniques like this,” said New York Medical College cell biologist Stuart Newman, according to NPR. “It would be quite straightforward to make new pathogens this way.”
This technology is still fairly new, and federal agencies may be reluctant to support gene drive research for targeting Zika virus, Stat News reports. The World Health Organization does not fund lab research like this and the Gates Foundation has not yet responded in regards to supporting this research. The Office of the Assistant Secretary for Preparedness and Response deals as well, since its Biomedical Advanced Research and Development Authority has license to work on medical countermeasures but not vector control measures.

“Technologically, we could probably do it in a couple of years,” said Kevin Esvelt, a gene-drive researcher at MIT’s Media Lab. “I’m sure we’ll be able to do it before people can agree if we should.”