AntiviralWolbachiastrains associate withAedes aegyptiendoplasmic reticulum membranes and disturb host cell lipid distribution to restrict dengue virus replication

Abstract

AbstractThe insect endosymbiotic bacteriumWolbachia pipientisis being utilised as a biocontrol tool to reduce the incidence ofAedes aegypti-transmitted viral diseases like dengue. However, the precise mechanisms underpinningWolbachia’s antiviral activity are not well defined. Here we generated a panel ofAe. aegypti-derived cell lines infected with antiviral strainswMel andwAlbB or the non-antiviral strainwPip to understand host cell morphological changes specifically induced by antiviral strains. Antiviral strains were frequently found to be entirely wrapped by the host endoplasmic reticulum (ER) membrane, whilewPip bacteria clustered separately in the host cell cytoplasm. ER-derived lipid droplets (LDs) increased in volume inwMel-andwAlbB-infected cell lines and mosquito tissues compared to cells infected withwPip orWolbachia-free controls. Inhibition of fatty acid synthase (required for triacylglycerol biosynthesis) reduced LD formation and significantly restored ER-associated dengue virus replication in cells occupied bywMel. Together, this suggests that antiviralWolbachiastrains may specifically alter the lipid composition of the ER to preclude the establishment of DENV replication complexes. DefiningWolbachia’s antiviral mechanisms will support the application and longevity of this effective biocontrol tool that is already being used at scale.ImportanceAedes aegyptitransmits a range of important human pathogenic viruses like dengue. However, infection ofAe. aegyptiwith the insect endosymbiotic bacterium,Wolbachia, reduces the risk of mosquito to human viral transmission.Wolbachiais being utilized at field sites across more than 13 countries to reduce the incidence of viruses like dengue, but it is not well understood howWolbachiainduces its antiviral effects. To examine this at the subcellular level, we compared how different strains ofWolbachiawith varying antiviral strengths, associate with and modify host cell structures. Strongly antiviral strains were found to specifically associate with the host endoplasmic reticulum and induce striking impacts on host cell lipid distribution. InhibitingWolbachia-induced lipid redistribution partially restored dengue virus replication demonstrating this is a contributing role forWolbachia’s antiviral activity. These findings provide new insights into how antiviralWolbachiastrains associate with and modifyAe. aegyptihost cells.