Abstract: Objective To screen and establish the optimal expression strategy of influenza virus H1N1 A/Nebraska/14/2019 HA, and lay a foundation for the development of protein vaccines. Methods The recombinant baculovirus of HA full-length, different C-terminal mutants of the extra cellular regions and co-expressing HA/M1 were constructed respectively. After 80 hours of infection in insect cells, the culture supernatant was collected, and the expression of recombinant antigen was identified by Western blot. Hemagglutination test indirectly analyzes its immunogenic. Then, HA/M1 protein was expressed in large quantities, and the physicochemical properties, hemagglutination activity and stability were analyzed after Core700 purification. Results The two C-terminal mutants of the extra cellular region of HA were all expressed in the form of trimers, but the expression supernatants had no hemagglutination activity; the full-length HA trimers had good hemagglutination activity, but they were membrane proteins thus were difficult to be purified. M1/HA co-expression supernatant also had hemagglutination activity. Electron microscopy of expression product purified by Core700 showed virus-like particles (VLPs) of 80 nm~150 nm. The hemagglutination titer of HA-M1-VLP reached 26 and was stable for three months at 4 ℃ as shown by light scattering. Conclusions HA-M1-VLP is easy to express and to be purified. The product has good stability, and hemagglutination activity, so can be used for the research of influenza virus protein vaccine.

Key words: H1N1, hemagglutinin (HA), matrix protein(M1), virus-like particle (VLP)