Researchers Investigate Dengue Virus Transmission

NMSU biology professor Kathryn Hanley was honored by New Mexico State University during a Scholarly Excellence Rally held Nov. 13. Hanley’s project was awarded $400,000 by the National Institute of Allergy and Infectious Diseases, one of the National Institutes of Health, to further research into dengue virus transmission. NMSU photo by Darren Phillips

With 400 million people infected annually across 100 countries, dengue virus poses a significant global health threat. To further research into dengue virus transmission, a project within the New Mexico State University Department of Biology has been awarded $400,000 by the National Institute of Allergy and Infectious Diseases, one of the National Institutes of Health.

The research project, “Mechanisms of Competitive Displacement by Lineages of Mosquito-Borne Dengue Virus,” was recognized by the university at a Scholarly Excellence Rally held Nov. 13. The event honored Kathryn Hanley, NMSU associate professor of biology and project principal investigator.

“There are no vaccines yet for dengue virus, and there are no drugs to treat dengue infections,” Hanley says. “My lab attempts to understand the forces that shape dengue virus transmission, because in the absence of any method of control it is really important to be able to predict what lineages of dengue are going to be transmitted, and how transmission is going to change in the future.”

Certain strains of dengue virus, the agent of dengue fever, can progress into a severe infection called dengue hemorrhagic fever, which kills about 5 percent of the people who develop it, Hanley explains.

“We’ve found that the strains that are most likely to cause hemorrhagic fever are the strains that are actually most likely to invade areas, take over and displace other strains that didn’t cause such severe disease,” she says. “This is part of the reason that we see rates of hemorrhagic fever going up.”

The NIH grant funds research aimed at understanding the mechanism for this process, by working to uncover why there are differences among strains in their ability to infect and be transmitted by mosquitoes, and why the strains that cause hemorrhagic fever tend to be more infectious for mosquitoes.

To tackle this, Hanley and her team are investigating at the molecular level – specifically, they are focused on the interaction of these strains with the mosquito immune system.

“If you had asked me 20 years ago whether insects had any immune system worth talking about, I would have told you no,” Hanley said. “Insect immunology, invertebrate immunology, has really come a huge way, very recently.”

Turns out, the insect immune system is fairly sophisticated. In order to capture all of the elements that shape transmission, particularly for insect-transmitted viruses like dengue, researchers have to understand both the insect-virus and human-virus interaction.

Part of this interaction is the cycle of infection between humans and mosquitoes. Essentially, Hanley explained, the mosquito becomes infected with dengue after feeding on an individual with the virus. If the mosquito then feeds on a healthy individual, the virus can be transmitted and the individual can develop dengue fever.

Understanding this process, and why particular strains of dengue are more infectious to mosquitoes, is important to developing ways to contain the spread of these strains.

“We’re hoping that if we can understand the factors that influence dengue transmission, we can better predict when particularly nasty outbreaks of dengue are going to happen,” Hanley said. “This knowledge will also lead to, eventually, new ways to either control virus transmission or develop antiviral drugs.”

While a separate focus from the grant project, a goal of Hanley’s lab is to identify drugs that may be useful in treating dengue virus infections.

For the NIH research, Hanley works in collaboration with NMSU biology professors John Xu and Immo Hansen, as well as Bill Messer at Oregon Health & Science University.

Hanley is currently the chair of the American Committee on Arthropod-Borne Viruses, with this research fitting into the organization’s aim to better understand and control arthropod-borne virus transmission.

While Hanley’s team primarily works with dengue virus, the systems developed through these studies can be generalized to apply to arthropod-borne viruses on a broader scale, making the research relevant to West Nile virus, as well as chikungunya and Zika viruses, which are both currently moving up from South America.

Source: New Mexico State University (NMSU)