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 35S 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.
"The selective genes of antibiotic and herbicide resistance were extensively used to select transgenic plant systems expressing HBsAg (Mason et al., 1992; Rukavtsova et al., 2003). However, such transgenic plants have considerable potential biological and environmental hazards. "
[Show abstract][Hide abstract] ABSTRACT: Transgenic potato plants expressing the gene of hepatitis B surface antigen (HBsAg) under the control of the double promoter of 35S RNA of cauliflower mosaic virus (CaMV 35SS) and the promoter of patatin gene of potato tubers have been obtained. Biochemical analysis of the plants was performed. The amount of HBsAg in leaves, microtubers, and tubers of transgenic potatoes growing in vitro and in vivo was 0.005-0.035% of the total soluble protein. HBsAg content reached 1 microg/g in potato tubers and was maximal in plants expressing the HBsAg gene under the control of CaMV 35SS promoter. In transgenic plants expressing HBsAg gene under the control of tuber-specific patatin promoter, HBsAg was found only in microtubers and tubers and was absent in leaves. Western blot analysis of HBsAg eluted from immunoaffinity protein A-Sepharose matrix has been performed. The molecular weight of HBsAg peptide was approximately 24 kD, which is in agreement with the size of the major protein of the envelope of hepatitis B virus. Using gel filtration, it was determined that the product of HBsAg gene expression in potato plants is converted into high-molecular-weight multimeric particles. Therefore, as well as in recombinant HBsAg-yeast cells, assembling of HBsAg monomers into immunogenic aggregates takes place in HBsAg-transgenic potato, which can be used as a source of recombinant vaccine against hepatitis B virus.
[Show abstract][Hide abstract] ABSTRACT: The idea of an oral vaccine administered as a portion of plant tissue requires a high level of antigen production. An improved protocol for the induction of transgenic yellow lupin calli or tumours, reaching 44% of transformation rate, is presented here. It has been developed by using the nptII marker gene and the uidA reporter gene as well as various Agrobacterium strains and plant explants. This method of seedling and hypocotyl transformation was applied to raise calli or tumours producing a small surface antigen of Hepatitis B Virus (S-HBsAg). Lupin tissue lines were long-term cultured on selection media maintaining the growth rate and high expression level of the native form of S-HBs, up to 6 microg per g of fresh tissue.
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