Differential Small RNA Responses against Co-Infecting Insect-Specific Viruses in Aedes albopictus Mosquitoes

Abstract

The mosquito antiviral response has mainly been studied in the context of arthropod-borne virus (arbovirus) infection in female mosquitoes. However, in nature, both female and male mosquitoes are frequently infected with insect-specific viruses (ISVs). ISVs are capable of infecting the reproductive organs of both sexes and are primarily maintained by vertical transmission. Since the RNA interference (RNAi)-mediated antiviral response plays an important antiviral role in mosquitoes, ISVs constitute a relevant model to study sex-dependent antiviral responses. Using a naturally generated viral stock containing three distinct ISVs, Aedes flavivirus (AEFV), Menghai rhabdovirus (MERV), and Shinobi tetra virus (SHTV), we infected adult Aedes albopictus females and males and generated small RNA libraries from ovaries, testes, and the remainder of the body. Overall, both female and male mosquitoes showed unique small RNA profiles to each co-infecting ISV regardless of the sex or tissue tested. While all three ISVs generated virus-derived siRNAs, only MERV generated virus-derived piRNAs. We also studied the expression of PIWI genes in reproductive tissues and carcasses. In contrast to Piwi5-9, Piwi1-4 were abundantly expressed in ovaries and testes, suggesting that Piwi5-9 are involved in exogenous viral piRNA production. Together, our results show that ISV-infected Aedes albopictus produce viral small RNAs in a virus-specific manner and that male mosquitoes mount a similar small RNA-mediated antiviral response to that of females.

Interactions of the Insect-Specific Palm Creek Virus with Zika and Chikungunya Viruses in Aedes Mosquitoes

“…There is some consideration that the other pathways of the RNAi response could participate in antiviral defence [ 44 , 45 , 46 , 47 ]. Most of the studies demonstrating ISV–arbovirus interference in vitro had been conducted in Ae.…”

Insect-specific viruses regulate vector competence in Aedes aegypti mosquitoes via expression of histone H4

“…All 12 identified viruses, 7 known and 5 new, had RNA genomes, either singlestranded (of positive and negative polarity) or double-stranded (Figure 2b). The small RNA profile observed for the 12 viruses shows clear production of siRNAs (Supplementary Figure 3), which results from the activity of the RNAi pathway during active viral replication in the mosquito host (9,(30)(31)(32)(33)(34). Viruses detected in Aedes mosquitoes were strictly species-specific and often associated with specific was not certified by peer review) is the author/funder.…”

“…Since arboviruses generate as much of an RNAi response as ISVs (9, [31][32][33][34], it is unlikely that this is caused by a bias in detection in our small RNA-based strategy.…”

Understanding the Mechanisms Underlying Host Restriction of Insect-Specific Viruses

“…In addition, the small interfering (siRNA) pathway is considered the main antiviral response in mosquitoes [62]. The production of ISV-derived siRNAs has also been reported in ISV-infected mosquitoes [63][64][65][66]. In this context, both the infected cells and the virus reach a metastable equilibrium and tolerant state (persistent infection) [67].…”