RESUMEN
Since 2000,most of H5N1 subtype influenza A virus had a unique mutation of NS gene with 15base pair deletion from 263 to 277. In order to investigate the bio-characteristics of this mutation,two different NS recombinants,RWSN-248 and RWSN-m248,were generated via plasmid rescue from A/WSN/33(H1N1) and A/SD/04(H5N1). RWSN-248 had a higher viral titer than RWSN-m248 in MDCK and COS-1 cells that have an IFN response,but they had the similar growth ability in Vero cells that lack an IFN response. Both of two recombinants grew well in embryonated chicken eggs and had the similar viral titer and MDT. The results above revealed that the deletion from 263 to 277 sites of NS gene did not influence viral virulence to but decreased viral anti-IFN ability of H5N1.