Les densovirus : une « massive attaque » chez les arthropodes.

Densoviruses (DVs) are parvoviruses of arthropods and causative agents of natural epizootics in insects and crustaceans populations. Structurally simple, these small DNA viruses, display a large diversity of genomic sequences, structures and organizations. Such diversity, together with the diversity of their invertebrate hosts, from shrimps to mosquitoes and recently including sea stars, suggests that DVs are largely unknown and ubiquitous in the environment.

Densovirus crosses the insect midgut by transcytosis and disturbs the epithelial barrier function.

Densoviruses are parvoviruses that can be lethal for insects of different orders at larval stages. Although the horizontal transmission mechanisms are poorly known, densoviral pathogenesis usually starts with the ingestion of contaminated food by the host. Depending on the virus, this leads to replication restricted to the midgut or excluding it.

Four amino acids of an insect densovirus capsid determine midgut tropism and virulence.

Densoviruses are insect parvoviruses that are orally infectious for Lepidoptera. To assess the mechanisms underlying their specificity and their virulence, we investigated the role of eight candidate residues in the densovirus capsid. We showed that the substitutions of four amino acids were associated with decreased virulence due to a decreased ability to cross the host midgut epithelium, without an effect on viral replication in other tissues.

Pathogenesis of Junonia coenia densovirus in Spodoptera frugiperda: a route of infection that leads to hypoxia.

To evaluate densovirus potential against lepidopteran pests and their capacity to invade new hosts, we have characterised in vivo the infection and pathogenesis of the Junonia coenia densovirus (JcDNV) in the noctuid pest Spodoptera frugiperda. Here we show that infection starts with the ingestion of viral particles that cross the midgut epithelium without replicating. By quantitative PCR we established the kinetic and the route of infection, from virus ingestion to replication in visceral tracheae and hemocytes.