Ichnoviruses are a group of insect viruses that are obligate symbionts with several parasitoid wasps in the family Ichneumonidae. The most studied ichnovirus has been that associated with the parasitoid Campoletis sonorensis. CsIV virions are injected with an egg and ovarian proteins into the lepidopteran host of the wasp where viral products function to alter host physiology. To date, there have been three gene families described within CsIV due to similarities in sequence, protein structure, and function. These include the cys-motif, rep, and vinnexin gene families. Sequence analysis of the completed genome identified another putative gene family within CsIV characterized by protein sequences that carry similarity to the ankyrin repeat domains of the Drosophila dorsal/NF-kb transcription factor inhibitor cactus, a member of the Ik-b gene family. Seven cactus-related open reading frames of approximately 500-bp were identified within the CsIV genome. Northern blot and RT-PCR analyses of these viral genes (v-Ikb) have indicated that at least five of the seven v-Ikb genes are expressed in Heliothis virescens hosts by four hours post-parasitization. Preliminary data from antibodies raised against two of the v-Ikb genes suggest that the proteins localize to the hemocyte cytoplasm by 48 hours post-parasitization. It is hypothesized that v-Ikb proteins from CsIV may be functioning to suppress dorsal/NF-kb-dependent signaling during the immune response of parasitized H. virescens larvae. Investigations are underway to better understand this novel gene family in CsIV.
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