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Point mutations in the paramyxovirus F protein that enhance fusion activity shift the mechanism of

John B Johnson1, Anthony P Schmitt, Griffith D Parks

  • 1Department of Microbiology and Immunology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA.

Journal of Virology
|June 21, 2013
PubMed

Insights

Enhanced fusion activity in Parainfluenza virus 5 (PIV5) F protein increases antibody binding and susceptibility to complement-mediated neutralization by shifting complement activation pathways.

Area of Science:

  • Virology
  • Immunology
  • Structural Biology

Background:

  • Parainfluenza virus 5 (PIV5) is typically neutralized by the alternative complement pathway (AP) in normal human serum (NHS).
  • The role of PIV5 F protein fusion activity in complement activation and neutralization remains unclear.

Purpose of the Study:

  • To investigate the relationship between PIV5 F protein fusion activity, complement pathway activation, and virus neutralization.
  • To determine how enhanced fusion activity impacts PIV5 susceptibility to antibody-mediated neutralization.

Main Methods:

  • Generation of recombinant PIV5 with enhanced fusion activity via point mutations (G3A, S443P) in the F protein.
  • Assessment of virus neutralization by normal human serum (NHS) and heat-inactivated (HI) serum.
  • Analysis of complement component deposition (C4, factor B) on virions.
  • Evaluation of antibody-mediated neutralization using purified antibodies and electron microscopy for antibody deposition.

Main Results:

  • Mutant PIV5 viruses (G3A, S443P) with enhanced fusion activity were neutralized by both NHS and HI serum, unlike wild-type (WT) PIV5.
  • Hyperfusogenic mutants activated the classical/lectin complement pathways (C4 activation) and were neutralized by factor B-depleted serum but not C4-depleted serum.
  • Purified human antibodies effectively neutralized G3A and S443P viruses, with greater antibody deposition observed on mutant virions compared to WT PIV5.

Conclusions:

  • Single amino acid changes enhancing PIV5 F protein fusion activity shift complement activation mechanisms.
  • Enhanced fusion activity increases PIV5 susceptibility to antibody-mediated neutralization due to improved antibody binding.
  • Presents models for how paramyxovirus F protein fusion activity influences antibody-mediated neutralization.

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