A single NS2 mutation of K86R promotes PR8 vaccine donor virus growth in Vero cells

- A Vero-adapted influenza A virus was obtained by recombination of PR8 with WSN.
- A single mutation of NS2K86R promotes the PR8 virus growth in Vero cells.
- Later steps in the virus replication cycle were accelerated by NS2K86R mutation.
- NS2K86R does not increase PR8 virulence in either mice or embryonated eggs.
- PR8-NS2K86R virus could serve as a promising vaccine donor strain in Vero cells.

Vaccination is the most effective way to prevent and control infection by influenza viruses, and a cell-culture-based vaccine production system is preferred as the future choice for the large-scale production of influenza vaccines. As one of the WHO-recommended cell lines for producing influenza vaccines, Vero cells do not efficiently support the growth of the current influenza A virus vaccine donor strain, the A/Puerto Rico/8/1934 (PR8) virus. In this study, a single mutation of K86R in the NS2 protein can sufficiently render the high-yielding property to the PR8 virus in Vero cells. Further analysis showed that the later steps in the virus replication cycle were accelerated by NS2K86R mutation, which may relate to an enhanced interaction between NS2K86R and the components of host factor F1Fo-ATPase, FoB and F1β. Because the NS2K86R mutation does not increase PR8 virulence in either mice or embryonated eggs, the PR8-NS2K86R virus could serve as a promising vaccine donor strain in Vero cells.