Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2007
Publication Date: 10/1/2007
Citation: Stevens, W., Vories, E.D., Dunn, D., Rhine, M. 2007. Irrigation to maximize vaccine antigen production in pharmaceutical tobacco. Agronomy Journal. 99(5):1271-1277.
Interpretive Summary: Biotechnology companies have genetically modified plants to produce materials for therapeutic drugs and vaccines. For example, the Chlorogen company inserted a gene into tobacco to produce a protein used in an anthrax vaccine. A greenhouse study was conducted to determine the optimum soil water content for producing the vaccine protein in tobacco leaves, with results showing that irrigating too frequently was as detrimental to vaccine protein production as not watering plants often enough. The results of this study will help to insure that pharmaceutical materials can be produced economically and in sufficient quantities to meet the country's needs.
Technical Abstract: Biotechnology companies have engineered plants to produce recombinant proteins for therapeutic drugs and vaccines. Chlorogen, Inc. located in St. Louis, Missouri, inserted the protective antigen (PA) gene from Bacillus anthracis into tobacco (Nicotiana tabacum) chloroplasts to produce an anthrax vaccine. Protective antigen is the primary immunogen of human vaccines for Anthrax disease in the United States and United Kingdom. The objective of a greenhouse study was to determine the optimum soil water content for producing PA in tobacco leaves. Tests were conducted from December 2004 to March 2005. Transgenic PA tobacco seedlings were transplanted to native soil (fine-loamy, mixed, thermic Typic Argiudolls) in the greenhouse floor. Treatments consisted of soil water potential irrigation thresholds (-20, - 34, -48, and -62 kPa). Soil moisture sensors were buried 10 cm and micro-sprinklers used for irrigation. A ratoon system with two harvests was used. Results showed that irrigating pharmaceutical tobacco too frequently was as detrimental to vaccine protein production as not watering plants often enough. The -34 kPa soil water potential treatment produced the highest leaf yield and PA concentrations. Using ELISA quantification, the -34 kPa irrigation treatment averaged 529 µg PA kg-1 leaf fresh weight for the two harvests. Other treatments averaged 163 to 261 µg PA kg-1 leaf fresh weight.