The parasitoid wasp Cotesia congregata injects a polydnavirus, venom, and eggs into its lepidopteran host, the tobacco hornworm, Manduca sexta. Polydnaviruses (PDV’s) are responsible for suppressing the immune system of the host and allowing the juvenile parasitoids to develop without being encapsulated by host hemocytes mobilized by the immune system. Previous work identified a gene in the Cotesia rubecula PDV (CrV1) that is responsible for actin depolymerization of host hemocyte cells 4-8 hours post-parasitization. This type of inactivation in hemocytes of parasitized M. sexta leads to cellular disruption and apoptosis.
In this study the CrV1 homolog was identified and temporal expression of the CrV1 homolog has been found to begin as soon as four hours post-parasitization and persist for the duration of parasitism, with maximum expression occurring at twenty-four hours. During this experiment M. sexta immune response was characterized by staining with FITC-labeled phalloidin, which binds filamentous actin. This technique was successfully used to observe hemocyte disruption in parasitized and virus-injected hosts compared with nonparasitized control hosts. Parasitized host hemocytes displayed blebbing, actin depolymerization, and overall cell disruption. Using CrV1 antibodies, we CrV1-homolog gene products to host hemocyte cells. This supports our hypothesis that viral gene products are responsible for impaired immune response by the host.
Species 1: Hymenoptera Braconidae Cotesia congregata
Species 2: Lepidoptera Sphingidae Manduca sexta (tobacco hornworm)
Keywords: parasitism, polydnavirus
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