Importance of viral genomic composition in modulating glycoprotein content on the surface of influenza virus particles

Despite progress in our knowledge of the internal organisation of influenza virus particles, little is known about the determinants of their morphology and, more particularly, of the actual abundance of structural proteins at the virion level. To address these issues, we used cryo-EM to focus on viral (and host) factors that might account for observed differences in virion morphology and characteristics such as size, shape and glycoprotein (GP) spike density. Twelve recombinant viruses were characterised in terms of their morphology, neuraminidase activity and virus growth. The genomic composition was shown to be important in determining the GP spike density. In particular, polymerase gene segments and especially PB1/PB2 were shown to have a prominent influence in addition to that for HA in determining GP spike density, a feature consistent with a functional link between these virus components important for virus fitness.

Research Highlights
► Cryo-EM and reverse genetics as tools to investigate determinants of influenza morphology.
► Surface GP density influenced by both the virus subtype and the mode of production.
► Viral genomic composition not the only determinant of viral size and shape...
► ...but important in determining surface GP density and possibly HA/NA ratio.
► PB1/PB2 and HA gene segments strongly influence surface GP spike density.