In vitro and in vivo characterization of Neodiprion abietis (Hymenoptera: Diprionidae) nucleopolyhedrovirus infection and pathology




Whittome, Beatrixe H.

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This work describes the pathology of the baculovirus native to the balsam fir sawfly, Neodiprion abieris nucleopolyhedrovirus (NeabNPV), both in vitro and in vivo. In vitro techniques were initially established through the characterization of Lambdina fiscellaria lugubrosa NPV (LafiNPV-W) in Malacosoma disstria (forest tent caterpillar) and Choristoneura fumiferana (eastern spruce budworm) tissue cultures. The results showed that host cell selection is important for the accurate characterization of viral pathology M. disstria cells infected by LafiNPV-W supported a biased production of extracellular viral progeny and aberrant LafiNPV-W occlusion bodies. C. fumiferana cells, on the other hand, supported production of both the extracellular and occluded phenotypes. The pathology of NeabNPV was studied in vitro using the C. fumiferana cell line and three cell lines derived from the closely related red-headed pine saw-fly, N lecontei. All three sawfly cell lines were non-permissive to NeabNPV, while C. fumiferana was semipermissive and enabled preliminary characterization of early pathology, including early viral gene transcription. Due to only partial success in characterizing NeabNPV infection in vitro, pathology was examined within the native larval host, N. abietis. The first step in characterizing NeabNPV infection in vivo was to define the morphology and ultrastructure of the gut of uninfected N. abietis larvae. The sawfly alimentary canal consisted of cuticle lined foregut and hindgut, which adjoined to an elongated midgut. The epithelial tissue of the midgut was composed of regenerative and digestive columnar cells; the latter possessed a complex ultrastructure that reflexed the cells function in nutrient absorption and digestive enzyme secretion. NeabNPV pathology was only detected in the midgut epithelial cells. A time course of NeabNPV infection enabled the identification of several key cytopathic effects and the correlation of gene expression with specific phases of viral infection. These analyses revealed both differences and similarities between the process of infection and pathology induced by NeabNPV and lepidopteran NPVs and may serve as a different model for baculovirus infection of nonlepidopteran.



baculoviruses, Balsam fir, diseases and pests