Abstract
ABSTRACTVaccination against anthrax is the most important strategy to combat the disease. This study describes a generation of edible transgenic crop expressing, functional protective antigen (PA). In vitro studies showed that the plant‐expressed antigen is qualitatively similar to recombinant PA. Immunization studies in mouse animal models indicated the generation of PA‐specific neutralizing antibodies and stressed the need for improving expression levels to generate higher antibody titers. Genetic engineering of a plant organelle offers immense scope for increasing levels of antigen expression. An AT‐rich PA gene (pagA) coding for the 83‐kDa PA molecule was thus cloned and expressed in tobacco chloroplasts. Biolistics was used for the transformation of a chloroplast genome under a set of optimized conditions. The expression of the pagA gene with 69% AT content was highly favored by an AT‐rich chloroplast genome. A multifold expression level of functional PA was obtained as compared with the nuclear transgenic tobacco plants. This report describes for the first time a comprehensive study on generating transgenic plants expressing PA, which may serve as a source of an edible vaccine against anthrax. Two important achievements of expressing PA in an edible crop and use of chloroplast technology to enhance the expression levels are discussed here.