Hepatitis B surface antigen expression in transgenic tobacco (Nicotiana tabacum) plants using four different expression cassettes

Abstract

Plants can be used as cost effective systems for the production of therapeutic proteins, including recombinant vaccines. Tobacco leaf discs were transformed with four different expression cassettes harboring hepatitis B virus ‘s’ gene encoding surface antigen. The transgenic plants accumulated varied levels of antigen. The transgenic nature of the plants and expression of the antigen was confirmed by PCR and PCR-Southern analysis and reverse transcription (RT)-PCR. The expression levels were determined by ELISA and the maximum expression levels (19.4 ng g⁻¹ F.W. of leaves) was observed in pEFEHBS transformed plants using polyclonal antibodies whereas, monoclonal antibodies based ELISA analysis showed maximum expression (9.5 ng g⁻¹ F.W. of leaves) in pEFEHER transformed plants. The expression levels of pEFEHBS and pEFEHER transformed plants were more in plantlets than those grown in green house. Higher proportion of the particulate form of antigen was observed when it was expressed with a C-terminal ER retention signal. Wounding of the leaves enhanced the HBsAg expression by 3.12-fold in pHBS transformed plants. The expression of HBsAg was also noted in flower buds and seeds of the transgenic plants. This is the first report on the expression of HBsAg in tobacco seeds.