Diversity of Virus-Like Particles in Parasitoids’ Venom

Publisher Summary This chapter reviews data available on parasitoid wasps' VLPs, mainly on the basis of their structure and composition. This leads to the discussion how to discriminate between virus-resembling VLPs and viruses, and to suggest that some of the VLPs might be cellular secreted vesicles, such as microvesicles and exosomes described in many epithelium and cells, aimed to transfer toxins inside host cells. Finally, it proposes to avoid the misleading name of VLPs for vesicles produced in venom and rather use the term of “venosomes.” During oviposition in their insect hosts, most endoparasitic wasps inject venom and/or ovarian products that will either prevent the egg from being recognized by the host immune system or protect it from the immune response. This response, the encapsulation process, involves both hematopoietic cells that form successive layers around the parasitoid egg, and induction of the humoral melanization process, due to activation of the phenoloxidase cascade. Among components injected by the wasp with its eggs, several immune suppressive proteins have been described that suppress either the cellular or the humoral defenses. In species from specific braconid and ichneumonid groups, viral capsids containing multiple DNA circles (polydnaviruses, PDVs) produced in the ovary fluid are injected into the host and enter host cells.