Current status on: Biopharming: crops for the production of Therapeutic & Pharmaceutical proteins
Biopharming, also known as molecular farming, is the production of pharmacologically active substances, either induced or increased through the application of genetic engineering. The first instance of artificial gene expression in an organism to produce a pharmaceutical product was the synthesis of insulin in the bacterium E. coli (Goeddel et al., 1979). This type of biotechnology has since moved from microbial cell cultures to applications in eukaryotic organisms, such as plants and animals. The first genetically modified (GM) plants to be used for biopharming were tobacco and tomato plants which produced human serum albumin (Sijmons et al., 1990). Since those early breakthroughs, a wide range of plant-derived pharmaceutical and therapeutic proteins have been produced, including antibodies, subunit vaccines, human blood products, hormones and growth regulators (Twyman et al., 2003). There have been advances in methodology also; plant cell cultures and plants as ‘bioreactors’ have been used as techniques to more efficiently extract the protein product and modification of genes controlling storage and secretion shows potential for more effective extraction. Biopharming has a very valid use as a humanitarian tool, with Golden Rice having the potential to save millions of people at risk of blindness due to lack of dietary vitamin A and the concept of vaccines produced in food crops that can simply be consumed directly. Many products have been developed without ever reaching the market and numerous companies have gone bankrupt in pursuit of economical biopharming, for example, Biolex Therapeutics (Bagley, 2012)and Large Scale Biology Corp (Bloomburg, n.d.). As GM technology becomes increasingly prevalent throughout the world and pressures to reduce the use of conventional chemical-based methods in agriculture and other forms of industry, it’s applicability to the production of pharmaceutical & therapeutic proteins is bound to increase. However, as with all emerging GM based technologies, there are groups opposed to biopharming who hold considerable power in determining how widespread the concept could potentially become.
Certain strains of the bacterium Vibrio cholera cause cholera, an infection in the small intestines. A study in 2010 (Renuga et al., 2010) attempted to produce an edible cholera vaccine through recombinant genes inserted into banana callus cultures. The gene encoding cholera toxin subunit B (CT-B) was cloned using Escherichia coli-derived vector PRK2013. Following amplification using PCR, the CT-B gene was inserted into the plant transformation vector (plasmid) PGA 643 to create the plasmid PCAMBIA. This plasmid was inserted into the bacterium Agrobacterium tumefaciens and from here, into a banana callus culture. The callus was maintained and differentiated into plantlets, thus producing bananas expressing recombinant CT-B antigens. Using bananas as a medium for delivering vaccines was selected because the fruit is edible in its raw form and can the plant can be grown in a number of developing countries where cholera is prevalent like Haiti and regions of East Africa (WHO, 2012). There are plant-derived vaccines that are in the stages of clinical trials. Non-Hodgkin’s lymphoma is a variety of blood disease that occurs when B or T lymphocytes become cancerous. Tobacco plants have been genetically engineered to produce single-chain variable region (scFv) vaccines to treat lymphoma. Conventional methods of lymphoma vaccine production involve creating hybrid cell lines with a patient’s tumour cells and screening for tumour-specific immunoglobulins to then produce antibodies which are coupled to various proteins before they are administered to the patient. This method is difficult and time consuming and a more efficient and cheaper plant-based technique was developed in the late nineties (McCormick et al., 1999)...
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