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Baculovirus per os infectivity factors form a complex on the surface of occlusion-derived virus

Ke Peng1, Monique M van Oers, Zhihong Hu

  • 1Laboratory of Virology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.

Journal of Virology
|July 9, 2010
PubMed

Insights

Per os infectivity factors (PIFs) PIF1, PIF2, and PIF3 form a stable complex on baculovirus occlusion-derived virus (ODV) surfaces. This PIF complex, along with P74, is crucial for oral infection of insect larvae.

Area of Science:

  • Virology
  • Insect Pathology
  • Molecular Biology

Background:

  • Baculoviruses are essential insect pathogens.
  • Oral infectivity of baculovirus occlusion-derived virus (ODV) in insect larvae depends on five conserved per os infectivity factors (PIFs): PIF1, PIF2, PIF3, PIF4, and P74.
  • PIF1, PIF2, and P74 were previously thought to mediate virus binding to insect midgut cells.

Purpose of the Study:

  • To investigate the interactions between PIF1, PIF2, PIF3, and P74.
  • To determine the structural organization of these factors on the ODV surface.
  • To elucidate their role in baculovirus oral infection.

Main Methods:

  • Genetic deletion and reinsertion of PIF genes in Autographa californica multinucleocapsid nucleopolyhedrovirus (AcMNPV).
  • Biochemical analysis of protein complex stability (SDS-PAGE, beta-mercaptoethanol, heat treatment).
  • Coimmunoprecipitation assays to confirm protein interactions.
  • Electron microscopy to visualize protein localization on ODV.

Main Results:

  • PIF1, PIF2, and PIF3 form a stable complex on the ODV surface, resistant to harsh conditions.
  • The PIF1-PIF2-PIF3 complex formation is dependent on the presence of all three genes.
  • Coimmunoprecipitation confirmed PIF1, PIF2, PIF3, and P74 interactions, though P74 is not essential for PIF complex formation.
  • Electron microscopy revealed PIF1 and PIF2 are surface-localized on ODV.

Conclusions:

  • PIF1, PIF2, PIF3, and P74 constitute an evolutionarily conserved complex on the ODV surface.
  • This complex plays a critical role in the initial stages of baculovirus oral infection.
  • The findings provide new insights into the molecular mechanisms of baculovirus entry into insect hosts.

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