Introduction Viruses represent an important class of pathogens, causing serious concern for human health, as

well as important economic losses in crops and animals. Because they replicate inside cells, and rely for the most part on host cell molecular machineries for their replication, viruses pose specific challenges to the immune system. It is therefore interesting to study antiviral immunity in a wide range of organisms, to get a grasp on the palette of different strategies evolved by different animals to fight-off viruses. More specifically, there are several reasons to work on virus-host interaction in invertebrate models. First, the study of antiviral defense mechanisms in genetically tractable invertebrate models such as the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans can provide useful information on the genetic mechanisms operating, some of which may have been conserved through evolution. For example, antiviral apoptosis and viral suppressors of apoptosis were initially characterized while investigating resistance to baculovirus infection in Lepidopteran insects.1 The use of viruses (e.g., baculoviruses) as biological control agents against insect pests is a second reason to investigate virus-host interactions in invertebrates.2 A third motivation is that viral infection of invertebrates can cause important economic losses (e.g., contribution to colony-collapse disorder in honey-bees; infections with White Spot Syndrome virus (WSSV) in shrimp farming).3,4 A fourth and final reason is of course that hematophagous invertebrates such asAedes or Culex mosquitoes can transmit viral diseases (caused by so-called arthropod-borne viruses or arboviruses, e.g., dengue, yellow fever, West-Nile virus) to mammalian hosts.5