Since the World Health Organization classified the Zika virus epidemic as “public health emergency of international concern” in 2016, researchers have been looking for ways to control the spread of the virus, which can cause birth defects and other neurological problems.
In one strategy, which was approved by the United States Environmental Protection Agency, Oxitec plans to begin a two-year pilot project with genetically modified (GM) mosquitoes in the Florida Keys later this year. The male mosquitos have been engineered to contain a self-limiting gene. When they mate with wild-type female Aedes aegypti, the offspring that are produced do not live to maturity, thus naturally suppressing the population. This method is viewed as safer than using insecticides to control mosquito populations and prevent them from biting humans, which is how they transmit diseases like Zika, dengue and yellow fever.
Now a new research study at the University of Missouri is trying another approach: genetically modifying mosquitoes to be resistant to Zika virus altogether.
Alexander Franz, an associate professor in the MU College of Veterinary Medicine, collaborated with researchers at Colorado State University by using CRISPR gene-editing technology to produce mosquitoes that are unable to replicate Zika virus and therefore cannot infect a human through biting. Their work was recently published in the journal Viruses.
“We genetically manipulated these mosquitoes by inserting an artificial gene into their genome that triggers one of the immune pathways in the midgut to recognize and destroy the RNA genome of Zika virus,” Franz said. “By developing these mosquitoes that are resistant to the virus, the disease cycle is interrupted so transmission to humans can no longer take place.”
Franz added that the genetic modification is inheritable, so future generations of the altered mosquitoes would be resistant to Zika virus as well.
“We are interested in strategies for controlling insect vectors like mosquitoes that transmit various viruses affecting human health,” Franz said. “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. There is no vaccine for the Zika virus widely 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.”
Franz’ research is designed to help prevent another outbreak of Zika virus disease from occurring while also addressing concerns that have some have raised about reducing populations of mosquitoes, which are a food source for some animals. This is not necessarily an issue with Aedes aegypti, however, as the species is not native to the United States so local wildlife did not evolve with it as a primary food source.
“If you can ever find a way to block the transmission of a pathogen that negatively affects humans, that is good news,” Franz said. “We have shown this is a viable option for genetically modifying mosquitos 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.”
The study was funded by the National Institutes of Health.
This article was originally published by the University of Missouri.