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Title: Autographa californica multiple nucleopolyhedrovirus ODV-E56 is a per os infectivity factor, but is not essential for binding and fusion of occlusion-derived virus to the host midgut

Author
item Harrison, Robert - Bob
item Sparks, Wendy
item BONNING, BRYONY - Iowa State University

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2010
Publication Date: 1/5/2011
Citation: Harrison, R.L., Sparks, W.O., Bonning, B. 2011. Autographa californica multiple nucleopolyhedrovirus ODV-E56 is a per os infectivity factor, but is not essential for binding and fusion of occlusion-derived virus to the host midgut. Virology. 409:69-76.

Interpretive Summary: Insect pests cause billions of dollars of damage to crops each year. The use of chemical insecticides to control insect pests can have negative ecological, environmental, and health consequences. Baculoviruses are a group of insect viruses that can be used to infect and kill insect pests without the problems of chemical insecticides. A more complete understanding of how baculoviruses kill insect pests is necessary for improving their scope and performance as biopesticides. In this study, a baculovirus protein required by baculoviruses to infect and kill insects was studied, and the way that this protein enables baculoviruses to infect insects was determined. The information in this study contributes to the knowledge of how baculoviruses kill insect pests that is needed in order to identify or develop baculovirus strains with enhanced insecticidal activity. Baculoviruses have a wide range of applications in addition to their use as biopesticides, and this study will be of interest to scientists in academia, government, and industry who work with this group of viruses.

Technical Abstract: The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) occlusion-derived virus (ODV) envelope protein ODV-E56 is essential for oral infection of neonate Heliothis virescens larvae. Here, we present a more detailed study of ODV-E56 function. Bioassays with recombinant clones of AcMNPV lacking a functional odv-e56 gene confirmed that ODV-E56 was required for infectivity of both polyhedra and purified ODV. Binding and fusion assays showed that mutant ODV lacking ODV-E56 bound and fused at levels similar to wild-type ODV. Fluorescent microscopy of midguts from larvae inoculated with ODV-E56-positive and –negative viruses indicated that ODV-E56 was required for infection of the midgut epithelium. Purified ODV-E56 bound to several proteins in midgut-derived brush border membrane vesicles, but failed to rescue infectivity of ODV-E56-negative viruses in trans. These results indicate that ODV-E56 is a per os infectivity factor (PIF5) required for primary midgut infection at a step occurring after virion binding and fusion.