CSU leads push to engineer virus-resistant mosquitoes

FORT COLLINS, COLO. — A study led by Colorado State University (CSU) researcher Ken Olson shows that mosquitoes can be genetically engineered to be weapons against infectious diseases.

The study engineered the insects to be resistant to dengue fever virus. While the fever infects 100-million people each year, the finding has broad impact to other important mosquito-transmitted diseases for veterinary medicine.

Researchers triggered a naturally occurring anti-viral pathway in the mosquitoes, the university explains. Triggering the pathway, called RNA interference, allowed the researchers to reduce or prevent the mosquitoes' ability to transmit the virus. The insects were made resistant to the virus, of which there are four types.

"The research results of this study offer promising results for halting the spread of this disease by disarming mosquito's ability to contract and transmit the dengue type-2 virus, a cause of dengue fever," Olson says. "It demonstrates that it's feasible to develop a mosquito that won't transmit the disease to people by genetically triggering their RNA interference pathway."

CSU researcher Dr. Alexander Franz manipulated the DNA of mosquito embryos by introducing the DNA of a dengue-resistant gene into the embryo. The mosquito was engineered so that it expressed an effector molecule in the mosquito's gut as the mosquito took in blood containing virus.

This effector molecule turned on the RNA interference pathway in gut cells making the cells inhospitable to dengue virus replication. The resulting mosquitoes were resistant to the virus and also were fertile, which lends hope to researchers that they could be introduced into wild mosquito populations and have a widespread impact on the spread of the disease.

During the study, not all of the genetically engineered mosquitoes showed 100-percent resistance to the virus, the university says.

"We could potentially replace wild repopulations of mosquitoes with similarly engineered mosquitoes over time, as the wild populations breed with the resistant strains," Olson explains. "For this purpose, the engineered mosquitoes would need to reach 100-percent resistance to the virus."

The control technique could be applied to other vector-borne diseases, such as malaria.

This research, supported by the National Institutes of Health, was performed in collaboration with researchers at the University of California-Irvine.