Characterizaiton of virus-like particles prepared by Bac-to-Bac system co-expressing HA and M1 protein of highly pathogenic avian influenza H5N1

Abstract

Objective To express and characterize the virus-like particles(VLPs) of H5 subtype containing of hemagglutinin(HA) and matrix 1(M1) protein by using Baculovirus-insect cells. Methods Full length genes encoding HA protein from the A/Indonesia/05/2005(H5N1) strain and the M1 protein from the A/Anhui/01/2005(H5N1) strain were cloned into a baculovirus expression vector to construct pFBD-M1-HA.The expression of HA and M1 proteins were detected by Western blot and indirect immunofluorescence after the transfection of Spodoptra frugiperda (Sf9) insect cells with recombinant baculovirus. Purified VLPs were analyzed by SDS-PAGE and visualized with transmission electron microscope. The biological activity of purified VLPs was detected by hemagglutination test. Results The HA and M1 proteins of H5 subtype expressed by baculovirus-insect cells could be self-assembled into the functional mature VLPs. The hemagglutination titer of VLPs was as high as 1024 HAU/50 μl. Conclusion The H5 subtype VLPs as prepared in this study would pave a way for the development of a candidate recombinant A (H5) vaccine. Key words: Influenza virus; H5N1; Virus like particles(VLPs); Baculovirus expression system