The densovirus of Junonia coenia DNV has two strategies to cross the insect midgut barrier

Abstract

Densoviruses (DNV) are lethal for several insects, including agronomical pests and diseasevectors, at larval stages. As a model, we studied the Junonia coenia Densovirus (Jc DNV) infection of the Lepidopteran pest, Spodoptera frugiperda. The larvae get infected by the oral route, ingesting viral particles-contaminated food. We show that JcDNV cross the insect intestine (midgut) without replicating and reach the underlying target-tissues. To understand the early step of infection, we first analysed the JcDNV entry in midgut cells. Using primary midgut cell cultures we show that JcDNV was unable to enter stem- nor differentiated goblet cells. Columnar cells only exhibit virus particles at both apical (microvilli) and basolateral membranes. We next developed a midgut ex vivo assay to measure the transepithelial resistance during the JcDNV passage. Using a Ussing chamber, we show that a significant decrease of the paracellular electrical resistance is observed from 10 to 30 minutes post infection, suggesting an opening of the intercellular junctions. The corrresponding confocal analysis of whole mount midguts show that at 10 min, JcDNV is localised within endocytic-like vesicles while at 30 minutes, JcDNV display a paracellular localisation. Both mechanisms are currently under study to better characterise JcDNV strategies to cross midgut epithelium