Figure 4.

Reverse genetics approaches to generate influenza vaccines: For the development of reverse genetics, influenza vRNAs are cloned into the eight bi-directional plasmids. Transfection of the eight ambisense plasmids into permissible FDA-approved for vaccine production cell lines leads to the rescue of the recombinant influenza viruses containing the six internal genome segments from the high-growth virus (A) or from the MDV (B) and two genome segments (the HA and NA encoding segments) from WHO candidate strain for their use as IIV (A) or LAIV (B), respectively. Because the viruses are derived entirely from DNA, no selection system is needed to isolate the desired reassortant. The rescued viruses can be amplified and used as seed viruses for vaccine production.