Researchers in the Department of Microbiology, Immunology and Pathology (MIP) have discovered how a mosquito’s response to an invading virus such as dengue prevents the arthropod from becoming ill, but doesn’t completely eliminate the virus, allowing it to spread. The discovery is a step toward finding a way to prevent mosquitoes from spreading the virus to new victims.
Dengue fever and dengue hemorrhagic fever are major global public health burdens, with up to 100 million cases occurring annually, yet no vaccines or specific preventive medicines are currently available.
"The mosquitoes that transmit dengue viruses have a defense response known as RNA interference," said Dr. Carol Blair, a Professor in MIP’s Arthropod-borne and Infectious Diseases Laboratory, College of Veterinary Medicine and Biomedical Sciences. "For years, researchers have wondered how mosquitoes can contract the virus but not become ill. Our research shows that mosquitoes do put up a defense against the virus, but don't completely eliminate the virus. The virus multiplies within a mosquito's salivary glands, allowing it to transmit the virus to the next host it feeds on.
"Finding a way to interrupt the growth of the dengue virus within the mosquito before it is transmitted would be a significant weapon. This new research suggests that the virus has evolved a way to get around the mosquito’s defense system. Finding out how the virus evades the mosquito's response is an important next step in research that aims to fight disease by interrupting the growth of dengue virus within the mosquito before it can be transmitted."
Various types of RNA exist in cells and arboviruses, like dengue, carry their genetic information in an RNA molecule. RNA interference is an evolutionarily ancient antiviral defense used by mosquitoes and other invertebrates to specifically destroy the RNA of many invading arthropod-borne viruses.
The Colorado State team of researchers recently proved that ramping up the RNA response in the mosquito did kill the dengue virus pathogen. In a paper published Feb. 13, 2009, in the public access journal PLoS Pathogens, they show that RNA interference - the defense response - is initiated within mosquitoes immediately after they take in blood containing dengue virus and that impairing the mosquito's response increases the transmission of the virus.