Defective viral genomes from chikungunya virus are broad-spectrum antivirals and prevent virus dissemination in mosquitoes

Defective viral genomes (DVGs) are truncated and/or rearranged viral genomes produced during virus replication. Described in many RNA virus families, some of them have interfering activity on their parental virus and/or strong immunostimulatory potential, and are being considered in antiviral approaches. Chikungunya virus (CHIKV) is an alphavirus transmitted by Aedes spp. that infected millions of humans in the last 15 years. Here, we describe the DVGs arising during CHIKV infection in vitro in mammalian and mosquito cells, and in vivo in experimentally infected Aedes aegypti mosquitoes. We combined experimental and computational approaches to select DVG candidates most likely to have inhibitory activity and showed that, indeed, they strongly interfere with CHIKV replication both in mammalian and mosquito cells. We further demonstrated that some DVGs present broad-spectrum activity, inhibiting several CHIKV strains and other alphaviruses. Finally, we showed that pre-treating Aedes aegypti with DVGs prevented viral dissemination in vivo. Author summary Defective viral genomes (DVGs) are produced during virus replication. On their own they cannot replicate, but some of them can compete with wild-type virus for viral and/or cellular resources. For chikungunya virus, interference by DVGs has not been described. Here, we use a new approach based on experimental evolution and computational analysis to characterize all DVGs generated in a virus population and identify those with the highest antiviral potential. We confirm their antiviral activity in both mammalian and mosquito host environments and show that some can broadly interfere with other strains or related alphaviruses. Finally, we show that DVGs can inhibit virus dissemination in mosquitoes.