Preparation of Vero Cell-Adapted Influenza H1N1 Virus Strain by Reassortment

Objective To prepare Vero cell-adapted influenza H1N1 virus strain by reassortment and lay a foundation of production of influenza vaccine using Vero cells as a substrate.Methods SPF chick embryo and Vero cells were co-infected with Vero cell-adapted influenza virus strain A / Yunnan / 1 / 2005Va(H3N2)and strain A / Caledonia / 20 / 99(H1N1)recommend by WHO for production of influenza vaccine in the Northern Hemisphere during 2007～2008.The reassortants were screened with antibody against strain A / Yunnan / 1 / 2005Va(H3N2)subcultured in Vero cells for 12 passages and identified for subtype by HI test and RT-PCR.The viruses before and after reassortment were cultured in a large quantity in chick embryos and Vero cells respectively, and inactivated with formaldehyde.ICR mice were immunized with the prepared inactivated influenza vaccines to observe the im-munogenicities.Results A Vero cell-adapted influenza H1N1 virus strain was obtained, of which the HI titer was maintained at 512 after subculture for 9 passages, and the immunogenicity showed no significant difference with that before reassortment.Conclusion The Vero cell-adapted epidemic strain of influenza virus may be obtained by reassortment of Vero cell-adapted and epidemic strains.