Synthesis and assembly of anthrax lethal factor-cholera toxin B-subunit fusion protein in transgenic potato.

A DNA encoding the 27-kDa domain I of anthrax lethal factor protein (LF), was linked to the carboxyl terminus of the cholera toxin B-subunit (CTB-LF). The CTB-LF fusion gene was transferred into Solanum tuberosum cells by Agrobacterium tumefaciens-mediated in vivo transformation methods and antibiotic-resistant plants were regenerated. The CTB-LF fusion gene was detected in transformed potato leaf genomic DNA by polymerase chain reaction (PCR)-mediated DNA amplification. Immunoblot analysis with anti-CTB and anti-LF primary antibodies verified the synthesis and assembly of biologically active CTB-LF fusion protein oligomers in transformed plant tuber tissues. Furthermore, the binding of CTB-LF fusion protein pentamers to intestinal epithelial cell membrane receptors measured by GM1-ganglioside enzyme-linked immunosorbent assay (GM1-ELISA) indicated that the CTB-LF fusion protein made up approx 0.002% of the total soluble tuber protein. Synthesis of CTB-LF monomers and their assembly into biologically active CTB-LF fusion protein pentamers in potato tuber tissues demonstrates the feasibility of using edible plants for production and delivery of adjuvanted LF protein for CTB-mediated immunostimulation of mucosal immune responses against anthrax toxin.