PAN substitutions A37S, A37S/I61T and A37S/V63I attenuate the replication of H7N7 influenza A virus by impairing the polymerase and endonuclease activities

J Gen Virol. 2017 Mar;98(3):364-373. doi: 10.1099/jgv.0.000717. Epub 2017 Apr 1.

Abstract

Substitutions in the PA N-terminus (PAN) of influenza A viruses are associated with viral pathogenicity. During our previous study, which identified PAN-V63I and -A37S/I61T/V63I/V100A substitutions as virulence determinants, we observed a severe decrease in virus growth and transcription/replication capacity posed by PAN-A37S/V100A substitution. To further delineate the significance of substitutions at these positions, we generated mutant H7N7 viruses bearing the substitutions PAN-A37S, -A37S/I61T, -A37S/V63I, -V100A, -I61T/V100A and -V63I/V100A by reverse genetics. Our results showed that all mutant viruses except PAN-V100A showed a significantly reduced growth capability in infected cells. At the same time, the PAN-A37S, -A37S/I61T and -A37S/V63I mutant viruses displayed decreased viral transcription and replication by diminishing virus RNA synthesis activity. Biochemical assays indicated that the substitutions PAN-A37S, -A37S/I61T and -A37S/V63I suppressed the polymerase and endonuclease activities when compared with those of the wild-type. Together, our results demonstrated that the PAN-A37S, -A37S/I61T and -A37S/V63I substitutions contributed to a decreased pathogenicity of avian H7N7 influenza A virus.

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Birds
  • Dogs
  • Influenza A Virus, H7N7 Subtype / genetics
  • Influenza A Virus, H7N7 Subtype / growth & development
  • Influenza A Virus, H7N7 Subtype / pathogenicity*
  • Influenza in Birds / virology*
  • Madin Darby Canine Kidney Cells
  • Protein Domains
  • RNA, Viral / genetics
  • RNA-Dependent RNA Polymerase / genetics
  • RNA-Dependent RNA Polymerase / metabolism*
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*
  • Virulence / genetics
  • Virulence Factors / genetics
  • Virulence Factors / metabolism*
  • Virus Replication / genetics

Substances

  • PA protein, influenza viruses
  • RNA, Viral
  • Viral Proteins
  • Virulence Factors
  • RNA-Dependent RNA Polymerase