New Tool Against Spread of Dengue Fever Created

Aedes aegypti mosquito - primary
vector for the spread of Dengue
fever; © PHIL

Anthony James, a vector biologist at University of California, Irvine, is one of a team of researchers who injected DNA into mosquito embryos, creating the first stable transgenic mosquito resistant to Type 2 dengue fever virus, the most prevalent strain of the disease. The mosquitoes that survived the procedure also remained fertile and were able to reproduce, a key factor for any future strategies that may involve replacing mosquito populations with their genetically modified counterparts. “These results are very exciting because they provide us a genetic tool we can use to control mosquito-borne diseases such as dengue fever,” James said.

In the study, the researchers exploited a vulnerability of the dengue virus to make the mosquitoes resistant to infection. This vulnerability occurs when the virus replicates and its single strand of RNA briefly becomes double–stranded. At this point, the virus is vulnerable because of a naturally occurring protein called dicer-2. This protein acts like scissors on the double strand, chopping it up and rendering its genetic material useless. The researchers found a way to control and speed up the process. They accomplished this by cloning a section of the virus’ RNA and injected two inverse copies of it into mosquito embryos. The copies formed a double-stranded RNA, which, as expected, bound with dicer-2 and was chopped up. The virus never had the opportunity to replicate.

James and his colleagues performed tests on a family of mosquitoes descended from one of the original embryos that survived the procedure. They found that the vast majority of that family was highly resistant to dengue infection. They also were able to detect the engineered RNA in the mosquitoes, a sign that the genetic alteration had been successful and passed down through reproduction.; Source: University of California, Irvine