Skip to main content
. Author manuscript; available in PMC: 2018 Sep 11.
Published in final edited form as: Curr Top Microbiol Immunol. 2009;333:165–176. doi: 10.1007/978-3-540-92165-3_8

Figure 2.

Figure 2

Schematic diagram of a 4-plasmid-based reverse genetic approach to generate vaccine seed viruses. A Pol I plasmid that synthesizes modified HA and NA gene segments is prepared from the circulating wild-type strains. Another Pol I plasmid that synthesizes the other six gene segments is prepared from a backbone virus that grows well in eggs or in cell culture. Two plasmids, expressing polymerase proteins or NP, respectively, are also prepared. Thus, a total of 4 plasmids are used to generate the vaccine seed viruses, with higher efficiency than other current systems, which can contain more than 8 plasmids.