Mosquito-borne flaviviruses (MBFVs) are a global public health burden. MBFVs have several unique 3'UTR structures that inhibit the host RNA decay machinery to produce subgenomic flaviviral RNAs (sfRNAs). Number of sfRNA species and their relative quantities are dependent on the 3'UTR tertiary structures and can vary between tissues. Two recent in vivo studies demonstrated that sfRNA enhances mosquito transmission, resulting in increased infection rate of saliva. Transmission efficiency is determined by the immune response. First evidence points to sfRNA interference with the Toll and RNAi immune pathways. However, a more complex picture that includes flexibility in sfRNA production and interaction with immune-related proteins remains to be explored.
Keywords: Xrn1; flavivirus; innate immunity; mosquitoes; sfRNA; transmission.