Enhanced-Transient Expression of Hepatitis C Virus Core Protein in Nicotiana tabacum, a Protein With Potential Clinical Applications

Mohammadzadeh, Sara; Khabiri, Alireza; Roohvand, Farzin; Memarnejadian, Arash; Salmanian, Ali Hatef; Ajdary, Soheila; Ehsani, Parastoo

Plants have an extensive potential to provide safe and inexpensive sources of biopharmaceutical and vaccination proteins (18) . Currently, several plant-derived viral proteins such as hepatitis B surface antigen (19) and Norwalk virus capsid protein (20) are in vaccination clinical trials. Recently, invention of transgenic tobacco plants expressing HCVcp stably at T0 and T1 generations (21) or directing the expression of its 143-amino acid Nterminal in tobacco chloroplasts (22) were reported. Although these prior reports proved the proper antigenic structure of the plant-derived HCVcp for diagnostic purposes and indicated its full functionality to react with poly/monoclonal anti-core antibodies and HCV-infected human sera, however, both studies addressed only the transgenic (stable) tobacco plant generation for HCVcp. However, transient expression in plants, compared with transgenic plant generation, is currently the method of choice due to several advantages like the simplicity and feasibility of rapid protein expression, omitting tissue culture and regeneration costs and ease of large scale industrial plans (23) (24) (25) . An important example of transient expression in plants is the production of seasonal influenza vaccines in tobacco (26) . The success in efficient plant transient expression, however, depends on several factors such as: codon-optimization of the heterologous gene according to the plant-codon adaptation index (27, 28) , selection of the proper expression vector (29, 30) , and efficient inhibition of the gene silencing phenomenon which suppresses the expression of foreign genes in plants (31) . While at present knowledge and techniques for the abovementioned parameters are being improved, providing novel data on transient expression process for the regionally-adapted plant hosts in general, and overcoming the plant-based gene silencing phenomenon in specific, is of high importance.