Dengue virus, DENV, belongs to a genus flavivirus. DENV are segregated into 4 serotypes: DENV1-4 (though, in 2013, one study suggested the existence of 5th serotype). Each DENV serotype induces serotype-specific immune protection but strangely can cross-enhance clinical severity of other DENV serotype-induced infection.
New study in journal Science tried to decipher the mystery of DENV immune response. Using antigenic cartography derived from the large set of DENV isolates and immunofocus reduction neutralization assays the study revealed that proportion of DENV within serotype have greater antigenic resemblance to DENV of a different serotype than to some DENV of the same serotype.
First, the authors created DENV antigenic cartography from samples derived from African green monkey after viral challenge. Note that (1) DENV3-4 sera (open circles) are clustered more tightly to corresponding viruses, compared to DENV1-2 sera and (2) proportion of viral isolates (closed circles) are more close to virus from other serotypes than to its own.
Next, the authors created DENV antigenic cartography from healthy volunteers vaccinated with monovalent DENV vaccines or from samples of DENV natural infection in humans. Please note that here too vaccination with DENV1-2 induced less tight map compared to DENV3-4 vaccination or natural infection.
In summary, these DENV data revealed that segregation of DENV isolates into distinct serotypes may not adequately explain DENV immune response. It also showed that unlike natural infection, DENV vaccine produced less-focused immune response, especially for DENV1 and DENV2.