The Adaptation Of Influenza B Virus Cold-adapted Strains In Vero Cells And Genetic Research

Influenza virus can cause respiratory disease. It’s highly contagious, mainly through air droplets which suddenly occurred within a short period and spread rapidly. Annual flu pandemic or localized outbreaks can cause very high morbidity and mortality and threaten human health bring huge economic losses. At present,although a small number of antiviral drugs has some effect at present but still influenza can not be controlled effectively. Therefore, the most economical and effective way to prevent and control of pandemic influenza is influenza vaccine. Influenza B viruses are an important component of the vaccine. Live attenuated influenza virus vaccine(LAIV) vaccination which is similar to influenza virus natural infection process and immunization is better than inactivated vaccines(IV). It can induce longer-lasting mucosal immunity, humoral and cellular immune responses. For other types of influenza viruses it also have a certain cross-protection. LAIV is now production with chicken embryos which has many defects and limitations. So using mammalian cells in vitro to prepare influenza virus vaccine is a better choice. Vero cell(African green kidney cells)line are highly recommended by WHO for manufacture of biological products which can be used fermenter to achieve large-scale production. But commercialized LAIV based on mammalian cells is not appear yet.In this research we use B/Yunnan/23/2011ca as parent strain which is already get Vero cell adapted feature(Va). After passing35generations with improved culture conditions, we get a strain of influenza B viruses which HA titer can be maintained at1:512and have temperature sensitivity(ts) feature, cold-adapted(ca) feature in the condition of25℃.After series of biological characteristics detection we do gene analysis for HA, NA, M1, NS, NP segments. We find after pass35generation, virus’ HA, NA protein amino acid has no changes and some genetic locus may control Va, ts, ca features at M1, NS, NP. This research laid the foundation for use of comparative genomics and reverse genetics to clarify the mechanism of va, ts, ca features.