not in Young Polydnaviruses are genetic symbionts of wasp endoparasitoids belonging to the hymenopteran families Ichneumonidae (ichnoviruses) and Braconidae (bracoviruses). They exist as proviruses integrated in the wasp's chromosomal genome, which then excise and undergo replication during the stage of adult development of the wasp. During wasp oviposition into their caterpillar host, the fully formed virus particles are injected along the parasitoid's eggs into the host hemocoel, where the eggs hatch and undergo larval development. The primary function of the polydnavirus is to trigger host immunosuppression so that host hemocytes are prevented from encapsulating the parasitoid's eggs and/or larvae. Polydnavirus transcripts are expressed following parasitization and alter host hemocyte adhesive properties that prevents encapsulation; in some species, viral gene expression triggers host hemocyte apoptosis, thereby rendering the host immunosuppressed. This review summarizes the major ! features of polydnaviruses and provides a global view of their functions in the lepidopteran hosts of the parasitoid wasps that carry them both as integrated viral sequences in their genome and as free virus to function physiologically in host regulation following parasitization of the host. BR Documentation. Publications. Evolution. Associations. Parasites diseases and disorders. Parasites. Insect parasites. Hosts. Insect hosts. Diseases and disorders. Microbial diseases. Lepidoptera (Insecta): Host; Braconidae (Ichneumonoidea): Parasite; Ichneumonidae (Ichneumonoidea): Parasite. Braconidae, Ichneumonidae: Literature review, Evolution, Associations, Polydnaviruses (virus), Biology, function and coevolutionary strategies, review, Lepidopteran hosts; Lepidoptera: Literature review, Hymenopteran parasitoids, viral symbiont biology, function and coevolution, Hymenopteran parasites, Braconidae and Ichneumonidae, Parasitoid viral symbiont biology, function and coevolutionary strategies, review, Viral diseases, Polydnaviruses, Biology, function and coevolution with hymenopteran parasitoids. ST Insecta, Hymenoptera, Apocrita, Terebrantia, Ichneumonoidea. Arthropods; Hymenopterans; Insects; Invertebrates; Lepidopterans. none2006