Preventing an Antigenically Disruptive Mutation in Egg-Based H3N2 Seasonal Influenza Vaccines by Mutational Incompatibility

Cell Host Microbe. 2019 Jun 12;25(6):836-844.e5. doi: 10.1016/j.chom.2019.04.013. Epub 2019 May 28.


Egg-based seasonal influenza vaccines are the major preventive countermeasure against influenza virus. However, their effectiveness can be compromised when antigenic changes arise from egg-adaptive mutations on influenza hemagglutinin (HA). The L194P mutation is commonly observed in egg-based H3N2 vaccine seed strains and significantly alters HA antigenicity. An approach to prevent L194P would therefore be beneficial. We show that emergence of L194P during egg passaging can be impeded by preexistence of a G186V mutation, revealing strong incompatibility between these mutations. X-ray structures illustrate that individual G186V and L194P mutations have opposing effects on the HA receptor-binding site (RBS), and when both G186V and L194P are present, the RBS is severely disrupted. Importantly, wild-type HA antigenicity is maintained with G186V, but not L194P. Our results demonstrate that these epistatic interactions can be used to prevent the emergence of mutations that adversely alter antigenicity during egg adaptation.

Keywords: antigenicity; egg-adaptive mutation; epistasis; hemagglutinin; influenza virus; receptor binding; vaccine.

MeSH terms

  • Adaptation, Biological
  • Animals
  • Antigens, Viral / chemistry
  • Antigens, Viral / genetics
  • Antigens, Viral / immunology
  • Binding Sites
  • Chick Embryo
  • Crystallography, X-Ray
  • Hemagglutinin Glycoproteins, Influenza Virus / chemistry
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics*
  • Hemagglutinin Glycoproteins, Influenza Virus / immunology*
  • Influenza A Virus, H3N2 Subtype / genetics
  • Influenza A Virus, H3N2 Subtype / growth & development*
  • Influenza A Virus, H3N2 Subtype / immunology*
  • Influenza Vaccines / genetics*
  • Influenza Vaccines / immunology*
  • Mutation, Missense*
  • Protein Conformation
  • Technology, Pharmaceutical / methods
  • Virus Cultivation / methods


  • Antigens, Viral
  • Hemagglutinin Glycoproteins, Influenza Virus
  • Influenza Vaccines