Expression of Hepatitis B Surface Antigen in Transgenic Banana Plants and NT- I Cell Line of Tobacco

Hepatitis B is one of the alarming diseases globally. There are about 350 million chronic carriers in the world and it is estimated that 75-100 million of them will die of liver cirrhosis and/or hepatocellular carcinoma. Treatment is expensive and cure rates are not impressive. The advent of recombinant DNA technology resulted in the development of rDNA vaccine using yeast as an expression system. The expense of this vaccine prevented its inclusion in mass immunization programmes, especially in the developing countries. Plant based production of vaccines, preferably in edible parts like fruits, may enable the development of cost effective and more acceptable delicious vaccines. In order to develop edible vaccine for Hepatitis B, researchers world wide, have endeavored to express the surface antigen (HBsAg) of this virus in plants and they could successfully demonstrate the proper folding and immunogenicty of plant derived HBsAg. In our laboratory, Hepatitis B virus ‘s’ gene coding for surface antigen was cloned into plant expression vectors, with and without endoplasmic reticulum retention signal. Transformed NT-I cell lines of tobacco and banana plants were obtained and analyzed for the integration of the transgene by PCR and expression levels were assayed by ELISA. Western blot analysis confirmed the presence of 24 kDa band specific to HBsAg in the transformed tobacco cells. HBsAg was expressed both as intracellular and secreted forms in transformed NT-I cells. This is the first report on the secretion of HBsAg particles by plant cells into the cell culture medium and expression in banana plants.