Mosquitoes genetically modified to be resistant to Zika

US researchers have used CRISPR gene-editing technology to produce mosquitoes that are unable to replicate Zika virus and therefore cannot infect humans through biting — a novel approach to what the World Health Organization (WHO) has deemed a “public health emergency of international concern”.

Researchers have wrestled with different strategies for controlling the spread of Zika virus, which is transmitted to humans from female mosquito bites. One approach, which has been approved by the US Environmental Protection Agency, will see more than 750 million genetically modified mosquitoes released into the Florida Keys in 2021 and 2022. These ‘suicide mosquitoes’ are genetically altered to produce offspring that die before emerging into adults and therefore cannot bite humans and spread disease.

However, wiping out future generations of mosquitoes may cause environmental complications, such as potentially disrupting food chains. A new study from the University of Missouri and Colorado State University, published in the journal Viruses, offers another option: genetically modifying mosquitoes to be resistant to Zika virus altogether.

“We genetically manipulated these mosquitoes by inserting an artificial gene into their genome that triggers one of the immune pathways in the midgut to recognise and destroy the RNA genome of Zika virus,” said Associate Professor Alexander Franz from the University of Missouri. “By developing these mosquitoes that are resistant to the virus, the disease cycle is interrupted so transmission to humans can no longer take place.”

Assoc Prof Franz added that the genetic modification is inheritable, so future generations of the altered mosquitoes would be resistant to Zika virus as well.

“Public health experts suggest having a toolbox with different approaches available to tackle a virus such as Zika, and unfortunately right now there are limited options,” he said. “There is no vaccine for the Zika virus available and spraying insecticides has become ineffective since the mosquitoes can develop resistance, so we are simply trying to expand the toolbox and provide a solution by genetically modifying the mosquitoes to become Zika-resistant while keeping them alive at the same time.”

Assoc Prof Franz said his research is designed to help prevent another outbreak of Zika virus disease from occurring.

“If you can ever find a way to block the transmission of a pathogen that negatively affects humans, that is good news,” he said. “We have shown this is a viable option for genetically modifying mosquitoes in a lab setting. There would need to be thorough discussions about regulatory compliance to see if this can be a solution out in the field down the road, and who knows when another Zika outbreak might happen in the future, which is why this research is so important.”

Image credit: ©stock.adobe.com/au/tacio philip

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