In-depth phylogenetic analysis of the hemagglutinin gene of influenza A(H3N2) viruses circulating during the 2016-2017 season revealed egg-adaptive mutations of vaccine strains

• Published in: Expert review of vaccines Vol. 19; no. 1; p. 115
• Main Authors: Galli, Cristina, Orsi, Andrea, Pariani, Elena, Lai, Piero Luigi, Guarona, Giulia, Pellegrinelli, Laura, Ebranati, Erika, Icardi, Giancarlo, Panatto, Donatella
• Format: Journal Article
• Language: English
• Published: England 02.01.2020
• Subjects: Amino Acid Substitution; Eggs; Epitopes - immunology; Hemagglutinin Glycoproteins, Influenza Virus - genetics; Hemagglutinin Glycoproteins, Influenza Virus - immunology; Humans; Influenza A Virus, H3N2 Subtype - genetics; Influenza A Virus, H3N2 Subtype - immunology; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza, Human - immunology; Influenza, Human - prevention & control; Influenza, Human - virology; Mutation; Phylogeny; influenza A(H3N2) virus; influenza vaccine; Cell-derived vaccine; egg-derived vaccine; egg-adaptive mutations; virus evolution
• ISSN: 1744-8395
• DOI: 10.1080/14760584.2020.1709827

: The authors conducted an in-depth phylogenetic analysis of the hemagglutinin (HA) gene of A(H3N2) identified during the 2016-2017 season to compare the circulating strains with both the egg-derived and cell-derived 2016-2017 candidate vaccine virus (CVV). : 162 HA1 sequences of H3N2 viruses identified during the 2016-2017 season were phylogenetically analyzed and compared with egg-/cell-derived CVV. The predicted vaccine efficacy (pVE) of egg-/cell-derived CVV against field strains was quantified by P model. : All H3N2 belonged to 3C.2a genetic clade, most (80.2%) to 3C.2a1 sub-clade. Several H3N2 variants circulated in the 2016-2017 season. HA sequences of field H3N2 strains displayed greater identity with cell-derived CVV than with egg-derived CVV. The amino acid substitutions in positions 160 and 194 identified in egg-derived CVV affected the pVE, which was lower for egg-derived CVV than for cell-derived CVV. : The results suggested that reduced vaccine effectiveness observed in 2016-2017 season was probably due to changes in the HA of vaccine strains acquired upon adaptation in eggs, which are the basis of most manufacturing systems currently used globally. Egg-free vaccine manufacturing systems would be advisable to improve the effectiveness of influenza vaccines.