By painstakingly silencing genes one at a time, scientists at Duke University Medical Center have identified dozens of proteins the dengue fever virus depends upon to grow and spread among mosquitoes and humans.
The research, appearing in the April 23 issue of the journal Nature , opens the door to new ways to potentially prevent or treat the disease, which infects millions of people around the globe every year.
Dengue fever is a mosquito-borne illness that can cause debilitating sickness and death. According to the World Health Organization, almost half the people in the world are vulnerable to the dengue virus. Public health officials are worried because dengue appears to be popping up in places where it has rarely appeared before and there is some concern that current epidemics are may be fueled by global warming.
"Dengue is a nasty disease, and right now, there is no treatment for it and no way to prevent it," says Mariano Garcia-Blanco, M.D., Ph.D., professor of molecular genetics and microbiology at Duke University Medical Center and senior author of the study. "But if we can find a weakness in the virus, we can design a strategy to fight it. This study has helped us identify some gaps in dengue's armor."
Garcia-Blanco, who is also professor of emerging infectious diseases at the Duke-NUS Graduate Medical School in Singapore, used RNA interference (RNAi) to unlock dengue's secrets. RNA interference is a normal biological process cells use to turn gene expression on or off depending upon which gene products, or proteins, are needed at any given moment. "That very same system proved to be the perfect investigative tool for our study," says Garcia-Blanco.
Garcia-Blanco and colleagues in Duke's RNAi facility were able to knock down gene function in fruit fly cells infected with a strain of the dengue virus known as DENV-2. Silencing one gene at a time (there were about 14,000 of them) allowed researchers to pinpoint which genes, or host factors, were essential to viral growth and which ones were not. They used fruit flies as a model because the genetic tools needed for the same work in mosquitoes have not been developed yet.
The process yielded 116 host factors that appeared to be important to successful dengue infection in fruit flies. In testing several of these host factors in mosquitoes at Johns Hopkins University, researchers subsequently discovered that at least one – and possibly a second – was necessary for dengue infection to occur in the insects.