Replication is the key barrier during the dual-host adaptation of mosquito-borne flaviviruses

Mosquito-borne flaviviruses (MBFs) adapt to a dual-host transmission circle between mosquitoes and vertebrates. Dual-host affiliated insect-specific flaviviruses (dISFs), discovered from mosquitoes, are phylogenetically similar to MBFs but do not infect vertebrates. Thus, dISF-MBF chimeras could be an ideal model to study the dual-host adaptation of MBFs. Using the pseudoinfectious reporter virus particle and reverse genetics systems, we found dISFs entered vertebrate cells as efficiently as the MBFs but failed to initiate replication. Exchange of the untranslational regions (UTRs) of Donggang virus (DONV), a dISF, with those from Zika virus (ZIKV) rescued DONV replication in vertebrate cells, and critical secondary RNA structures were further mapped. Essential UTR-binding host factors were screened for ZIKV replication in vertebrate cells, displaying different binding patterns. Therefore, our data demonstrate a post entry cross-species transmission mechanism of MBFs, while UTR-host interaction is critical for dual-host adaptation.

Automated summary

Mosquito-borne flaviviruses (MBFs) adapt to transmission between mosquitoes and vertebrates. In this study, a model using chimeras of dual-host affiliated insect-specific flaviviruses (dISFs) and MBFs was developed to study the dual-host adaptation of MBFs. The researchers found that the dISFs could enter vertebrate cells as efficiently as MBFs but failed to replicate. However, when certain regions of the dISF were replaced with those from Zika virus (ZIKV), replication in vertebrate cells was rescued. This study also identified essential host factors that interact with specific regions of the virus genome.