MDCK-SIAT2,6-UF cells [10, 11], which overexpress influenza virus α2,6-linked sialic acid receptors, were used for the isolation of influenza viruses. The cells were propagated as monolayers at 37 °C and 5% CO2 in Advanced Dulbecco’s Modified Eagle’s Medium (Invitrogen Corp., Carlsbad, CA, USA) supplemented with 2 mM L-Alanyl-L-Glutamine (GlutaMAX, Invitrogen Corp.), antibiotics (50 μg/mL penicillin, 50 μg/mL streptomycin, 100 μg/mL neomycin (Invitrogen Corp.)), and 10% (v/v) low IgG, heat-inactivated gamma-irradiated fetal bovine serum (HyClone, Logan, Utah).