In vitro infection of Wolbachia in insect cell lines

Abstract

Bacteria of the genus Wolbachia are intracellular symbionts that are found in a broad range of insects and cause a variety of reproductive alterations, including male killing, parthenogenesis, feminization and cytoplasmic incompatibility. Although Wolbachia has not been cultured outside its host cells, it can be co-cultured with insect cell lines in vitro, and this technique would facilitate studies on Wolbachia. In this study, we inoculated five Wolbachia strains into two insect cell lines to examine the ability of the cell lines to harbor different infections. The Wolbachia strains used were wKue, derived from Ephestia kuehniella, wCauA and wCauB, from Cadra cautella, and wMel and wMelPop, from Drosophila melanogaster. The cell lines used were Sf9 of Spodoptera frugiperda (Lepidoptera) and AeAl2 of Aedes albopictus (Diptera). Immunofluorescence staining with an antibody against Wolbachia surface protein showed that wCauA was successfully maintained in both AeAl2 and Sf9 cells and that wCauB and wKue were maintained in AeAl2 cells. The infection levels, determined by real-time quantitative PCR targeting the Wolbachia 16S rRNA gene, varied among different infections.