Density dependent enhancement effect of Wolbachia and the host RNAi response to a densovirus in Aedes cells

Abstract

The endosymbiotic bacterium Wolbachia pipientis has been shown to restrict a range of RNA viruses in Drosophila melanogaster and transinfected dengue mosquito, Aedes aegypti. Here, we show that Wolbachia infection enhances replication of Aedes albopictus densovirus (AalDNV-1), a single stranded DNA virus, in Aedes cell lines in a density-dependent manner. Analysis of previously produced small RNAs of Aag2 cells showed that Wolbachia-infected cells produced greater proportions of viral derived short interfering RNAs as compared to uninfected cells. Additionally, we found production of viral derived PIWI-like RNAs (vpiRNA) produced in response to AalDNV-1 infection. Nuclear fractions of Aag2 cells produced a primary vpiRNA signature U1 bias whereas the typical \"ping-pong\" signature (U1 - A10) was evident in the cytoplasmic fraction. This is the first report of the density-dependent enhancement of DNA viruses by Wolbachia. Further, we report the generation of vpiRNAs in a DNA virus-host interaction for the first time.