38th Annual Meeting of the Society for Invertebrate Pathology

Parasitoid polydnaviruses (PDVs) have potent biological effects on insect hosts. These viruses induce disruption of host immune function and development. In highly co-evolved host-parasitoid systems, expression of PDV genes in host hemocytes induces their apoptosis and prevents encapsulation of the parasitoid egg. In refractory hosts, expression of PDV genes is suppressed, and the parasitoid is avidly encapsulated. In tobacco hornworm larvae parasitized by italicCotesia congregataitalic, production of six CcPDV encoded transcripts begins as early as 30 min post-oviposition in host fat body and hemocytes. Antibodies to the virally encoded protein CrV1 bind to the hemocyte surface as well as to foci in the cytoplasm of the apoptotic cells.Chelonine wasp PDV genes are expressed in synchrony with appearance of symptoms of developmental derangements in the host caterpillar. Thus, the endocrine as well as the immune system serves as a target for PDV activity. Polydnavirus receptors have yet to be isolated in host endocrine glands but likely exist. The ‘essence’ of a parasitoid is that its presence causes developmental arrest of the host in the larval or pupal stage prior to adult eclosion. The PDVs of many parasitoids have been shown to induce this type of arrest when injected into nonparasitized ‘surrogate’ hosts.