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Title: The occlusion-derived virus envelope protein ODV-E56 is required for optimal oral infectivity but is not essential for virus binding and fusion

Author
item SPARKS, WENDY - Iowa State University
item BONNING, BRYONY - Iowa State University
item Harrison, Robert - Bob

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/2/2010
Publication Date: 7/11/2010
Citation: Sparks, W.0., Bonning, B., Harrison, R.L. 2010. The occlusion-derived virus envelope protein ODV-E56 is required for optimal oral infectivity but is not essential for virus binding and fusion. Meeting Abstract. 43:43.

Interpretive Summary:

Technical Abstract: The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) odv-e56 gene encodes an occlusion-derived virus (ODV)-specific envelope protein, ODV-E56. To determine the role of ODV-E56 in oral infectivity, we produced recombinant EGFP-expressing AcMNPV clones (Ac69GFP-e56lacZ and AcIEGFP-e56lacZ) in which ODV-E56 protein synthesis had been eliminated by insertion of a beta-galactosidase expression cassette into the odv-e56 open reading frame in either orientation. The odv-e56 recombinant viruses exhibited no obvious alterations in polyhedra production and morphogenesis or in the production of infectious budded virus in cell culture. In bioassays using three lepidopteran host species (Heliothis virescens, Helicoverpa zea, and Ostrinia nubilalis), the oral infectivities of the odv-e56 mutant viruses Ac69GFP-e56lacZ and AcIEGFP-e56lacZ were profoundly impaired compared to those of wild-type and control recombinant viruses. Oral infectivity against all three species was fully restored by marker-rescue of the odv-e56 mutant viruses with either the AcMNPV or the Rachiplusia ou MNPV odv-e56 gene. An in vivo fluorescence dequenching assay for virus binding and fusion indicated that odv-e56 mutant viruses bound and fused to midgut epithelial cells at the same level as wild-type virus. Fluorescent microscopy of infected midguts, however, indicated that odv-e56 negative viruses were unable to productively infect midgut cells. These results suggest that ODV-E56 is required for viral infection of the midgut epithelium at a step following virion binding and fusion.