In addition, scientists have made excellent progress in using plants as vaccine-manufacturing and delivery systems. They have used tobacco, potatoes, tomatoes and bananas to produce experimental vaccines against infectious diseases, including cholera, a number of microbes that cause food poisoning and diarrhea (e.g., E. coli and the Norwalk virus), hepatitis B and the bacterium that causes dental cavities. A cancer "vaccine" (which is therapeutic and not preventative) to non-Hodgkin's lymphoma has also been produced in plants.
Since most proteins cannot be chemically synthesized, there are very few options for protein production for pharmaceutical purposes: mammalian and microbial cell cultures and plants. More than $500 million and five years are required to build a facility for mammalian cell cultures. Using plants to produce therapeutic proteins lowers facility and production costs associated with plant-made pharmaceuticals.
One of the companies developing plant-produced antibodies estimates that this production method is 25 to 100 times less expensive than cell-fermentation methods. Standard fermentation methods can produce 5 to 10 kilograms of a therapeutic antibody per year, while this company reports that it can produce 10,000 kilograms of monoclonal antibodies per year. Using plants as factories to produce therapeutic proteins also enables researchers to develop novel and complex molecular forms that could not normally be grown in mammalian cell cultures.
Because protein-producing plants require relatively little capital investment, and the costs of production and maintenance are minimal, they may provide the only economically viable option for independent production of therapeutic proteins in underdeveloped countries.