RNA structure duplications in the dengue virus genome facilitates host adaptation.

VILLORDO S *; FILOMATORI C * EQUAL CONTRIBUTION TO THIS WORK; GAMARNIK A

Belèm

Encuentro; Fourth Pan-American Dengue Network Meeting; 2014

Pan American Dengue Research Network(Pan-Dengue Net)

Dengue virus cycles in nature between humans and mosquitoes, however, it is still unclear how the virus adapts to use different cellular machineries for replication and overcome different types of antiviral responses. RNA viruses in general have high capacity to adapt to different environments due to the genetic diversity of viral populations. Using dengue virus, we recently found specific RNA sequences in the viral 3'UTR that are essential for viral replication in mosquito cells but dispensable for replication in mammalian cells. These studies provided direct evidence for host-specific functions of viral RNA elements and raised the question whether viral RNA structures are under specific selective pressures during host adaptation. To further these studies, we evaluated how RNA cis-acting elements evolve under single-host selective pressures in mosquito and mammalian cells and during host switch. Deep sequencing of dengue virus populations subjected to host adaptation showed a strong selection of different mutations in the viral 3'UTR in each host, while cis-acting elements present at the 5' end of the genome remained unchanged. Secondary RNA structure analysis showed that viruses selected in mosquito cells contained mutations mapping to a single stem-loop structure, which was found to be duplicated in mosquito-borne flaviviruses. Using recombinant viruses and evaluation of fitness parameters, we found that RNA duplication is required to tolerate mosquito-adaptive mutations for replication in mammalian cells. Our findings provide a novel model supporting the role of RNA duplications for efficient dengue virus replication in multiple hosts.