[Generation of A/Chicken/Shanghai/F/98 (H9N2) avian influenza virus from eight plasmids]

Eight-plasmid system was used for the generation of Avian influenza virus (AIV) strain A/Chicken/Shanghai/F/98 (H9N2) which was isolated in China in 1998. In this plasmid-based expression system, viral cDNA was inserted beteen the RNA polymerase I (pol I) promoter and terminator sequences. The entire pol I transcription unit was flanked by an RNA polymerase II (pol II) promoter and a poly (A) site. Twenty-four hours after the transfection of eight expression plasmid into cos1 cells, the supernatant and cos1 cells transfected were inoculated into the allantoic cavity of 10-day-old specific-pothgen-free (SPF) chicken eggs. The HA titer was determined after passage of the rescued virus in chicken eggs, and as high as that of the parental wild-type virus.