To assay virus growth kinetics, two isogenic viruses containing eight segments of pH1N1 (A/England/195/09) were grown on either Madin-Darby canine kidney (MDCK) cells (originally sourced from the European cell culture collection) or MucilAir TM human airway epithelial (HAE) cells (Epithelix-Sà rl) at a multiplicity of infection (moi) of 0.01. At 12, 24, 48 and 72 h post-infection (MDCK) or 24, 48, 72, 96 and 120 h post-infection (HAE), viruses were collected from the apical surface and subsequently plaqued on MDCK cells to assay for viral titre.