RNA interference controls arbovirus replication in Culicoides cells

Arboviruses are transmitted to vertebrate hosts by biting arthropod vectors such as mosquitoes, ticks and midges. These viruses replicate in both arthropods and vertebrates and are thus exposed to different antiviral responses in these organisms. RNA interference (RNAi) is a sequence-specific RNA degradation mechanism that has been shown to play a major role in the antiviral response against arboviruses in mosquitoes. Midges (Culicoides spp.) are important vectors of arboviruses, known to transmit pathogens of humans and livestock such as bluetongue virus (Reoviridae), ropouche virus (Bunyaviridae), and likely the recently discovered Schmallenberg virus (Bunyaviridae). In this study we investigated whether Culicoides cells possess an antiviral RNAi response and whether this is effective against arboviruses including those with dsRNA genome such as BTV. Using reporter-gene based assays we established the presence of a functional RNAi response in Culicoides sonorensis derived KC cells is effective in inhibiting BTV infection. Sequencing of small RNAs from KC and Aedes aegypti-derived Aag2 cells infected with BTV or the unrelated Schmallenberg virus resulted in the production of virus-derived small interfering RNAs (viRNAs) of 21 nucleotides, similar to the viRNAs produced during arbovirus infections of mosquitoes. In addition, viRNA profiles strongly suggest that the BTV dsRNA genome is accessible to a Dicer-type nuclease. Thus, we show for the first Powered by Editorial Manager® and Preprint Manager® from Aries Systems Corporation time that midge cells control arbovirus replication by mounting an antiviral RNAi response resembling that of other insect vectors of arboviruses