Antiviral RNAi response in the mosquito vector Culex quinquefasciatus

Culex spp. mosquitoes are important vectors of viruses, such as West Nile virus, Eastern equine encephalitis virus and Rift valley fever virus. However, the interactions with their innate antiviral immunity, especially RNA interference (RNAi), are not well known. Most research on RNAi pathways in mosquitoes is focused on the tropical mosquito vectorvector mosquito Aedes aegypti. Here, we identified Cx. quinquefasciatus RNAi-related transcripts based on their homology to Ae. aegypti and investigated the production of arbovirus-specific small RNAs. Furthermore, by silencing the identified transcripts, we investigated the antiviral role of the different RNAi-related transcripts for two different arboviruses: Semliki forest virus (SFV) and Bunyamwera orthobunyavirus (BUNV). Our results showed an expansion of Ago2 and Piwi6 in Cx. quinquefasciatus compared to Ae. aegypti. While silencing of Ago2a and Ago2b increased BUNV replication, only Ago2b was antiviral against SFV. Our results suggest differences in the function of Cx. quinquefasciatus and Ae. aegypti RNAi genes, and highlighted the virus-specific function of these genes in Cx. quinquefasciatus.