Autographa californica multiple nucleopolyhedrovirus AC83 is a per os infectivity factor (PIF) protein required for occlusion-derived virus (ODV) and budded virus nucleocapsid assembly as well as assembly of the PIF complex in ODV envelopes

Muhammad Afzal Javed, Siddhartha Biswas, Leslie G. Willis, Stephanie Harris, Caitlin Pritchard, Monique M. van Oers, B. Cameron Donly, Martin A. Erlandson, Dwayne D. Hegedus, David A. Theilmann*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

44 Citations (Scopus)

Abstract

Baculovirus occlusion-derived virus (ODV) initiates infection of lepidopteran larval hosts by binding to the midgut epithelia, which is mediated by per os infectivity factors (PIFs). Autographa californica multiple nucleopolyhedrovirus (AcMNPV) encodes seven PIF proteins, of which PIF1 to PIF4 form a core complex in ODV envelopes to which PIF0 and PIF6 loosely associate. Deletion of any pif gene results in ODV being unable to bind or enter midgut cells. AC83 also associates with the PIF complex, and this study further analyzed its role in oral infectivity to determine if it is a PIF protein. It had been proposed that AC83 possesses a chitin binding domain that enables transit through the peritrophic matrix; however, no chitin binding activity has ever been demonstrated. AC83 has been reported to be found only in the ODV envelopes, but in contrast, the Orgyia pseudotsugata MNPV AC83 homolog is associated with both ODV nucleocapsids and envelopes. In addition, unlike known pif genes, deletion of ac83 eliminates nucleocapsid formation. We propose a new model for AC83 function and show AC83 is associated with both ODV nucleocapsids and envelopes. We also further define the domain required for nucleocapsid assembly. The cysteine-rich region of AC83 is also shown not to be a chitin binding domain but a zinc finger domain required for the recruitment or assembly of the PIF complex to ODV envelopes. As such, AC83 has all the properties of a PIF protein and should be considered PIF8. In addition, pif7 (ac110) is reported as the 38th baculovirus core gene.

Original languageEnglish
Article numbere02115-16
JournalJournal of Virology
Volume91
Issue number5
DOIs
Publication statusPublished - 2017

Keywords

  • AC83
  • AcMNPV
  • Baculovirus
  • Chitin binding domain
  • Fluorescence microscopy
  • Nucleocapsid assembly
  • Occlusion-derived virus
  • Per os infection
  • PIF
  • PIF complex
  • ZF domain
  • Zinc finger proteins

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