Abstract
Human is the host of Hepatitis delta virus (HDV), which can cause severe acute liver inflammation or chronic liver diseases. Currently there is no effective vaccine or diagnostic reagent for HDV due to the lack of a proper method to efficiently produce HDV proteins. To this end, the baculovirus/ mammalian cell system was explored as a useful tool to produce HDV proteins with proper post-translational modification. In this study, we first focused on the production of large hepatitis delta antigen (L-HDAg) to be a promising vaccine candidate against HDV. The recombinant baculovirus which expresses his-tagged L-HDAg(L-HDAgH) transduced the BHK cells with efficiencies higher than 90%. The expression level was significantly higher than that could be obtained by plasmid transfection and was further enhanced 3-fold to □19 □g/106 cells by the addition of 10 mM sodium butyrate. Importantly, the expressed L-HDAgH was localized to the cell nucleus and correctly isoprenylated. Moreover, L-HDAgH can be partially purified by denaturing Ni2+ chelate affinity chromatography. In addition, we also employed the baculovirus/ mammalian cell system to produce and characterize hepatitis delta virus-like particles (HDV VLP). After selecting the suitable virus for VLP production, we found that the relative baculovirus dosage, and hence the relative expression levels of L-HDAg and HBsAg, profoundly influenced the properties of HDV VLP. The higher MOT ratio of GD/GS2 increased the relative amounts of L-HDAg to HBsAg within the cells, thus leading to the incorporation of more L-HDAg into the HDV VLP. This, in turn, caused larger VLP size, higher density and larger weight ratio of L-HDAg/HBsAg in the particles. In summary, this study demonstrated that the baculovirus/ mammalian system provides a suitable way to produce proteins and VLP and apply on HDV research.