A/Nanjing/108/2009 (H1N1), a pandemic (H1N1) 2009 virus, was isolated from a swab sample of an outpatient febrile child at the Nanjing Children's Hospital during the pandemic in 2009, Nanjing, China. The sampling procedure was performed in accordance with the rules set by the Institutional Review Board at the Hospital. The eight genomic segments of this virus have been fully sequenced and the raw data are deposited at Genbank under accession numbers JQ173100 through JQ173107. The virus was grown in 9-day-old embryonating chicken eggs; virus allantoic fluid (VAF) was harvested 48 hrs after inoculation, then titrated with standard haemagglutination tests (HA) and plaque assays in MDCK cells for HA and infectious viral titers, respectively [24] . For viral infection, the 3D/4 cells were trypsinized, resuspended in RPMI 1640 medium containing 10% FBS, and plated on 6-cm tissue culture plates at 5610 6 cells per plate 12 hrs before infection. The cells were infected with H1N1pdm inocula in VAF at a multiplicity of infection (MOI) of 1. After 1 hr of adsorption, the virus inocula were discarded and 3 ml of serum-free RPMI 1640 medium containing TPCK-trypsin (1 mg/ml, Sigma) was added. The cells were incubated at 37uC and 5% CO 2 for various time points before cell lysates or total RNA extraction were prepared.