Plants as Bioreactors: Biopharming and Neutraceuticals

Plant products have long been used in medicine, and now plant biotechnology is entering the medical field in a spectacular way, with the creation of plants which produce proteins of pharmaceutical value or subunit vaccines.
1. Edible Vaccines
Traditionally, attenuated strains of pathogenic organisms have been injected or delivered orally to invoke an immune response. Now it is possible to clone genes encoding immunogenic subunits of pathogen proteins and to express these either in transgenic plants or in plant viruses. Transgenic plants have a permanent capacity to express the vaccine, whereas engineered viruses permit transient production of large quantities of immunogenic protein.The aim of this work is that by eating fresh fruit (e.g. banana) containing an antigen, individuals can develop immunity to the pathogenic organism via the gut immune system.
In some cases human trials are in progress to test the efficiency of this approach for the following diseases and applications: hepatitis B; cholera; E. coli heat-labile enterotoxin; Norwalk virus; rhinovirus; HIV; rabies; antimalHelvetica parasites; immunocontraception (ZP3 zona pellucida protein); and inhibition of late-onset diabetes.
The same approach is being used to engineer plant vaccines for domestic animals and livestock (e.g. parvoviruses such as feline panleukopenia virus, canine virus, mink enteritis virus); swine fever, foot and mouth disease and rabies.
2. Production of Antibodies in Plants
The ‘biopharming’ approach indicated above can also be used to produce either large quantities of antibodies in plants as bioreactors or to deliver pharmacologically active antibodies in food. A good example of the latter is the synthesis in plants of antibodies against the bacterium (Streptococcus mutatis) that causes dental caries in teeth. Extracted antibodies confer protection in human trials.Expressed in an apple, this transgenic apple a day would also keep the dentist away!
3. Plant Neutraceuticals
The concept of using plants as bio-factories to produce pharmaceuticals also extends to the potential production of a wide range of other products. These may be in the health care area (e.g. dermatology, cardiology, human metabolism, endocrinology, respiration, transplantation and oncology),or production of compounds that improve human diet or health (the formation of a new ‘wellness complex’ by food). For example, Prodi Gene and Stauffer seeds are growing maize that produces avidin for use in health diagnostic kits,and Brazzein, a lowcalorie natural sweetener.Other neutraceuticals include overproduction of vitamin A in rice or phytosterols to reduce cholesterol in humans. Clearly, identity preservation and separate storage/transport and handling will be required for such products, as for most high-value transgenic crops.