Abstract
In most of the world, Dengue virus (DENV) is mainly transmitted by the mosquito Aedes aegypti while in Europe, Aedes albopictus is responsible for human DENV cases since 2010. Identifying mutations that make DENV more competent for transmission by Ae. albopictus will help to predict emergence of epidemic strains. Ten serial passages in vivo in Ae. albopictus led to select DENV-1 strains with greater infectivity for this vector in vivo and in cultured mosquito cells. These changes were mediated by multiple adaptive mutations in the virus genome, including a mutation at position 10,418 in the DENV 3′UTR within an RNA stem-loop structure involved in subgenomic flavivirus RNA production. Using reverse genetics, we showed that the 10,418 mutation alone does not confer a detectable increase in transmission efficiency in vivo. These results reveal the complex adaptive landscape of DENV transmission by mosquitoes and emphasize the role of epistasis in shaping evolutionary trajectories of DENV variants.
Highlights
In most of the world, Dengue virus (DENV) is mainly transmitted by the mosquito Aedes aegypti while in Europe, Aedes albopictus is responsible for human DENV cases since 2010
To run experimental selection of DENV-1 to Ae. albopictus, we chose mosquitoes from Nice which were collected in the site of the first local cases of dengue in Europe, and exhibited low infection rates and transmission efficiencies
In human cells (Fig. 5c), viral titers remained between 2 and 3 Log[10] from 0 to 72 hpi. These results indicate that the adaptive mutations after serial passaging of DENV-1 1806 in Ae. albopictus mosquitoes increase the replication rate in mosquito cells at 24 hpi, that is recovered at 48 hpi
Summary
In most of the world, Dengue virus (DENV) is mainly transmitted by the mosquito Aedes aegypti while in Europe, Aedes albopictus is responsible for human DENV cases since 2010. Ten serial passages in vivo in Ae. albopictus led to select DENV-1 strains with greater infectivity for this vector in vivo and in cultured mosquito cells These changes were mediated by multiple adaptive mutations in the virus genome, including a mutation at position 10,418 in the DENV 3′UTR within an RNA stem-loop structure involved in subgenomic flavivirus RNA production. Dengue was not an uncommon disease in Europe: the last record of a dengue outbreak in the twentieth century was in Athens, Greece, in 1927–19285 This outbreak was unusual by the number of cases (~ 1 million) and the importance of severe clinical symptoms (e.g. hemorrhagic manifestations) leading to deaths (~ 1000). Ae. aegypti occupies preferentially urban environments while Ae. albopictus colonizes vegetated and rural habitats These features distinguish them in the transmission of arboviruses in human-mosquito cycles[18]. This mutation increased the infectivity of CHIKV in Ae. albopictus[36,37]
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