News: Dengue

March 13, 2006
Washington Post (Anthony James, UC Irvine)

Dengue-Resistant Mosquitoes

IRVINE — Researchers have created a genetically engineered mosquito that could help combat the insect-borne dengue fever virus, a painful and sometimes fatal disease that infects 50 million people a year.

By transforming and cloning genetic material from the virus and then injecting it into embryos of the Aedes aegypti mosquito, researchers at the University of California at Irvine were able to breed a version of the insect that is resistant to the virus. Mosquitoes that survived the procedure were able to reproduce and produce young that were similarly resistant -- and unable to pass the virus on.

Researchers have been working to create genetically modified insects to reduce illness and crop loss but with only modest success. And some fear that releasing modified insects could have unintended, problematic consequences.

Researcher Anthony James said his team's work represents "the first time we have brought all the pieces together to create a stable model that can also reproduce."

In the study, the researchers took advantage of a vulnerability of the virus, which in its life cycle briefly has a double strand of RNA, rather than its usual single strand. At that point, the RNA can be cut by a naturally occurring protein called dicer-2, thereby destroying the genetic material. Once the process is started on the double-stranded RNA, the single-stranded RNA also becomes vulnerable, and the virus's ability to replicate is destroyed.

The treated virus, which was then cloned and injected into mosquito embryos, "inoculated" the mosquitoes with an essentially benign form of the virus.

-- Marc Kaufman