The consortium of laboratories worldwide that are studying the differences among dengue viruses has shown that while the long-held view that there are four genetically-distinct types of the virus holds, far more important are the differences in their antigenic properties - the 'coats' that the viruses wear that help our immune systems identify them.
Researchers from the Dengue Antigenic Cartography Consortium analyzed 47 strains of dengue virus with 148 samples taken from both humans and primates to see whether they indeed fit into four distinct types.
The researchers found a significant amount of antigenic difference within each dengue serotype - in fact, the amount of difference within each serotype was of a similar order to that between the different types.
This implies that an individual infected with one type may not be protected against antigenically different viruses of the same type, and that in some cases the individual may be protected against some antigenically similar strains of a different type.
Researcher Leah Katzelnick said that they were surprised at how much variation they saw not only between the existing four known types of dengue, but also within each type, which means that hypotheses that put antigenic differences at the center of dengue epidemiology are now back on the table.
Characterizing the global variation of dengue viruses will be important for understanding where current vaccines will be protective. In the future, it may assist us in determining which strain to include in vaccination programs and to follow the virus as it evolves, say the researchers. The study appears in the Journal Science