Production of protein biopharmaceuticals in transgenic plants offers several advantages over traditional sources. For example, correct posttranslational processing has been demonstrated for proteins expressed in plants (Kusnadi et al. 1998), which does not occur in bacteria or yeast. Plant systems also offer low production cost, provide high storage stability, lack animal and human pathogens, and have the potential for virtually unlimited scale-up either in suspension culture or at the greenhouse or field scale (Kusnadi et al. 1998, Fischer et al. 2000).
Recombinant antibodies are among the key biopharma-ceutical agents that have been expressed in plants. Although few details on isolation of functional proteins from plant sources have been published, affinity chromatography using protein A or protein G has been used in the process (Fischer et al. 2000). Disadvantages of this method include high cost and ligand leaching (Gagnon 1996). We report here on a method for the purification of a recombinant antibody from corn seed using UNOsphere S support in the capture step and CHT ceramic hydroxyapatite in the polishing step. This process is efficient and scalable, and it avoids the use of protein A or G.