The 2nd sialic acid-binding site of influenza A virus neuraminidase is an important determinant of the hemagglutinin-neuraminidase-receptor balance

PLoS Pathog. 2019 Jun 10;15(6):e1007860. doi: 10.1371/journal.ppat.1007860. eCollection 2019 Jun.

Abstract

Influenza A virus (IAV) neuraminidase (NA) receptor-destroying activity and hemagglutinin (HA) receptor-binding affinity need to be balanced with the host receptor repertoire for optimal viral fitness. NAs of avian, but not human viruses, contain a functional 2nd sialic acid (SIA)-binding site (2SBS) adjacent to the catalytic site, which contributes to sialidase activity against multivalent substrates. The receptor-binding specificity and potentially crucial contribution of the 2SBS to the HA-NA balance of virus particles is, however, poorly characterized. Here, we elucidated the receptor-binding specificity of the 2SBS of N2 NA and established an important role for this site in the virion HA-NA-receptor balance. NAs of H2N2/1957 pandemic virus with or without a functional 2SBS and viruses containing this NA were analysed. Avian-like N2, with a restored 2SBS due to an amino acid substitution at position 367, was more active than human N2 on multivalent substrates containing α2,3-linked SIAs, corresponding with the pronounced binding-specificity of avian-like N2 for these receptors. When introduced into human viruses, avian-like N2 gave rise to altered plaque morphology and decreased replication compared to human N2. An opposite replication phenotype was observed when N2 was combined with avian-like HA. Specific bio-layer interferometry assays revealed a clear effect of the 2SBS on the dynamic interaction of virus particles with receptors. The absence or presence of a functional 2SBS affected virion-receptor binding and receptor cleavage required for particle movement on a receptor-coated surface and subsequent NA-dependent self-elution. The contribution of the 2SBS to virus-receptor interactions depended on the receptor-binding properties of HA and the identity of the receptors used. We conclude that the 2SBS is an important and underappreciated determinant of the HA-NA-receptor balance. The rapid loss of a functional 2SBS in pandemic viruses may have served to balance the novel host receptor-repertoire and altered receptor-binding properties of the corresponding HA protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Chlorocebus aethiops
  • Dogs
  • Humans
  • Influenza A Virus, H2N2 Subtype* / chemistry
  • Influenza A Virus, H2N2 Subtype* / genetics
  • Influenza A Virus, H2N2 Subtype* / metabolism
  • Influenza A Virus, H3N2 Subtype* / chemistry
  • Influenza A Virus, H3N2 Subtype* / genetics
  • Influenza A Virus, H3N2 Subtype* / metabolism
  • Madin Darby Canine Kidney Cells
  • N-Acetylneuraminic Acid / genetics
  • N-Acetylneuraminic Acid / metabolism
  • Neuraminidase* / chemistry
  • Neuraminidase* / genetics
  • Neuraminidase* / metabolism
  • Receptors, Virus* / chemistry
  • Receptors, Virus* / genetics
  • Receptors, Virus* / metabolism
  • Vero Cells
  • Viral Proteins* / chemistry
  • Viral Proteins* / genetics
  • Viral Proteins* / metabolism
  • Virion* / chemistry
  • Virion* / genetics
  • Virion* / metabolism

Substances

  • Receptors, Virus
  • Viral Proteins
  • NA protein, influenza A virus
  • Neuraminidase
  • N-Acetylneuraminic Acid

Grants and funding

W.D. was supported by a personal grant from the Chinese Scholarship Council (file number 201603250057). M.M. was supported by the German Research Foundation (DFG) (SFB 1021, project B02). E.v.d.V. was supported by a grant of the Volkswagen Foundation. C.A.M.d.H. was supported by the Mizutani Foundation for Glycoscience. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.