Analysis of transgenic tobacco plants carrying the gene for the surface antigen of the hepatitis B virus

The plasmids carrying the gene encoding the hepatitis B surface antigen (HBsAg) under the control of 35S RNA single or dual promoters of the cauliflower mosaic virus CaMV 35S were constructed. These constructions were used for obtaining transgenic tobacco plants that synthesize the HBS antigen. The presence of HBsAg in tobacco plant extracts was confirmed by the enzyme-linked immunoassay using antibodies against the native HBs antigen. The antigen amount in plants carrying the HbsAg gene under a single 35 S promoter was 0.0001-0.001 of the total soluble protein whereas the use of a dual 35S promoter increased the antigen synthesis to 0.002-0.05% of the protein. The antigen-synthesizing ability was inherited by the offspring. In the F1 plants, the antigen expression varied in different lines comprising 0.001 to 0.03% of the total soluble protein, which corresponded to the antigen amount in the F0 plants.