Transgenic pea seeds as bioreactors for the production of a single-chain Fv fragment (scFV) antibody used in cancer diagnosis and therapy

Field pea (Pisum sativum L.) appears well suited for the production of high-value molecules such as recombinant antibodies, with well-established agricultural practices world-wide and seeds that are easily stored and distributed. In order to evaluate the suitability of this grain legume for the production of biologically active antibodies, we transformed peas with a cDNA encoding the single-chain Fv fragment scFvT84.66. This scFv is derived from the monoclonal antibody T84.66, which recognises the well-characterised tumour-associated carcinoembryonic antigen. The antibody is useful for in vitro immunodiagnosis and in vivo imaging of human cancers. We expressed scFvT84.66 cDNA under the control of the seed-specific legumin A promoter. We targeted the antibody to the endoplasmic reticulum for better stability and high accumulation. Transgenic plants produced up to 9 μg per gram fresh weight of functional scFvT84.66 in their seeds. The transgene was stably inherited and expressed in the progeny, and the antibody remained active after storage in dried transgenic seeds for two months at room temperature. Our results demonstrate the suitability of grain legume seeds to produce biologically active recombinant antibodies, and the utility of field pea seeds as production vehicles for recombinant pharmaceutical macromolecules.