An endogenous viral element of Aedes albopictus is translated and limits cognate virus

BACKGROUND: The genomes of Aedes spp. mosquitoes host hundreds of non-retroviral endogenous viral elements (nrEVEs). The majority of nrEVEs are confined in piRNA clusters and produce P-element-induced wimpy testis-interacting RNAs (piRNAs), which were shown to be antiviral. Whether this is a universal mechanism or some nrEVEs have been exapted for antiviral functions as transcribed RNA or translated proteins remains unknown. RESULTS: We identified 20 nrEVEs located outside piRNA clusters and encompassing complete viral open reading frame in the genome of the Asian tiger mosquito Aedes albopictus. By integrating in vivo and in vitro experimental approaches using Aag2 cells, we provide evidence suggesting that one nrEVE, designated Flavi24, is translated in adult mosquitoes and contributes to controlling cognate viral infection. CONCLUSION: Our results expand the functions of Ae. albopictus nrEVEs suggesting they can regulate host-virus interactions through various mechanisms.