The flavivirus family includes a number of dangerous insect-borne diseases such as dengue, West Nile, yellow fever, tick-borne encephalitis and St. Louis encephalitis. Together, these viruses cause millions of cases of human illness each year (and some are also being studied to counteract potential bioterrorist attacks.)
In this week's issue of Cell, researchers from Purdue University describe the structure of dengue virus.
Dengue fever is a severe flu-like illness that causes high fever, rash and extreme pain in the head, muscles and joints. Dengue haemorrhagic fever is a potentially lethal complication that can cause internal bleeding, vomiting, severe abdominal pain and death.
The dengue virus is transmitted to humans through the bites of infected mosquitoes and is most often found in tropical and sub-tropical regions of the world. Last year, 74 cases of dengue infection were reported in the state of Hawaii. In recent weeks, an outbreak of the infection has left tens of thousands of people ill in Rio de Janeiro, Brazil.
The new studies of the dengue structure used the techniques of cryo-electron microscopy and three-dimensional image reconstruction. The image shows how the major protein -- called "E" for envelope protein -- organizes itself to form a protective shell around the virus.
The protein shell is made up of 60 subunits to form a 20-sided sphere. The shell serves as a cage for the genetic material inside, sheltering it from harm until it is released inside a host cell.
While simple viruses consist of only a protein shell and genetic information, more complex viruses, such as flaviviruses, also contain a lipid bilayer that sits between the protein shell and viral genome.
Kuhn says the three-dimensional reconstruction reveals several unexpected features in the dengue virus architecture: "The organization of the shell protein is very different from what we've seen before and what we might have predicted for this type of virus."
Though vaccines have been developed for dengue, control of the virus by vaccination has proved elusive. The detailed information obtained from a structure opens doors to the possibility of developing new vaccines and antiviral agents.
Because all flaviviruses are closely related, Kuhn says studying the structure of the dengue virus will reveal strategies that can be used to study other viruses in the family.
Related website:
World Health Organization, Dengue virus
[Contact: Michael Rossman, Richard Kuhn]
08-Mar-2002
