Mutations in the fusion protein heptad repeat domains of human metapneumovirus impact on the formation of syncytia

J Gen Virol. 2017 Jun;98(6):1174-1180. doi: 10.1099/jgv.0.000796. Epub 2017 Jun 14.


Human metapneumovirus (HMPV) is an important cause of respiratory tract infections. The mechanism by which its fusion (F) protein is responsible for variable cytopathic effects in vitro remains unknown. We aligned the F sequences of the poorly fusogenic B2/CAN98-75 strain and the hyperfusogenic A1/C-85473 strain and identified divergent residues located in the two functional heptad repeats domains (HRA and HRB). We generated recombinant viruses by inserting the mutations N135T-G139N-T143K-K166E-E167D in HRA and/or K479R-N482S in HRB, corresponding to swapped sequences from C-85473, into CAN98-75 background and investigated their impact on in vitro phenotype and fusogenicity. We demonstrated that the five HRA mutations enhanced the fusogenicity of the recombinant rCAN98-75 virus, almost restoring the phenotype of the wild-type rC-85473 strain, whereas HRB substitutions alone had no significant effect on cell-cell fusion. Altogether, our results support the importance of the HRA domain for an HMPV-triggered fusion mechanism and identify key residues that modulate syncytium formation.

MeSH terms

  • Animals
  • Cell Fusion*
  • Cell Line
  • DNA Mutational Analysis
  • Epithelial Cells / physiology
  • Epithelial Cells / virology
  • Giant Cells / virology*
  • Macaca mulatta
  • Metapneumovirus / genetics
  • Metapneumovirus / growth & development*
  • Models, Molecular
  • Mutant Proteins / chemistry
  • Mutant Proteins / genetics
  • Mutant Proteins / metabolism*
  • Mutation*
  • Protein Conformation
  • Protein Domains
  • Recombination, Genetic
  • Reverse Genetics
  • Viral Fusion Proteins / chemistry
  • Viral Fusion Proteins / genetics
  • Viral Fusion Proteins / metabolism*


  • Mutant Proteins
  • Viral Fusion Proteins