Is Plant Pharming a good way to make Cheaper Medicines?
All organisms, under normal condition, make proteins in their body only in required amounts that is in the amounts they require the proteins for life. This means that making a ton of proteins and purifying them, without losing its function, is difficult under ordinary conditions. So scientists use organisms like bacteria and yeast to make the protein in large amounts and purify them economically, in large amounts.
Growing bacteria and yeast for such processes require them to be grown in big tanks that contains thousands of liters of growth media, and then processed for protein purification. This is a delicate process because they should be kept from other contaminating microorganisms so that the proteins purified are without dangerous contaminants. So scientists developed an even simpler way of doing that make these proteins in plants or animals that can be grow without too much trouble.
The process of expressing pharmaceutical proteins in plants or animals for mass production is called pharming. This involves genetic techniques for expressing the protein that is required in these plants or animals. This is achieved using transgenic technology where the gene that codes for the protein is transferred to these organisms. Transgenic animals or plants are then grown, and proteins are purified from them. One of the advantages of using higher organisms, like plants and animals, for producing biologicals is that they have developed systems that chemically modify proteins just the way humans cells do. They can deal with large amounts of proteins that are made in them under pharming condition as well.
When animals are used for pharming, proteins are made in such a way that they accumulate in milk. It is possible to make them accumulate in blood or other body fluids, but milk offer several advantages over them. Scientists have developed protein purification techniques that can purify these proteins from milk. The first drug produced this way was ATryn, an antithrombin protein, and it was approved for marketing in European Union and US in 2006 and 2009 respectively.
Plants that are used in pharming include both algae that need to be grown in large bioreactors, and higher plants like rice, maize, potato and flax. The lower algae are engineered such that they secrete the protein of interest into the growth medium from which it can be purified. Plant cells that are isolated and used in culture in laboratories, like tissue cultured carrot cells, can also be used for this purpose. However, using plants as biopharmaceutical factories are controversial because of their transgenic nature.
Transgenic plants, especially farm crops, are thought to be unsuitable for cultivation outside controlled conditions, especially if they can cross-pollinate natural plants that are grown for food. This will cause the foreign protein, which is a physiologically active drug, to be expressed in food. That is a dangerous condition - unlike transgenic proteins expressed in a drought or pest resistant plant, a therapeutic protein might have adverse effects on normal individuals who feed on it. However, plants like rice and flax offer the advantage that they are self-pollinating plants that can be grown under isolation and still be propagated.
Plants offer several advantages over animals when used for pharming because they resemble humans in the way they process the proteins they make. This means that proteins they make can function as drugs in humans as well. Furthermore, viruses and bacteria that infect plants are different from human infectious pathogens and are less likely to affect human health. This offers far more safety since many viruses and bacteria that infect humans can grow in animals as well, making animal products potentially dangerous.
The therapeutic need of biologicals is increasing exponentially and is expected to reach 100 billion by 2020. These include hormones, cytokines and vaccines that are used for treatment of diseases ranging from common infections to cancers. Using yeast and bacterial systems alone will not supply this requirement and will not be economically unviable. Pharming is perhaps the best choice here since it is more economical compared to other alternatives and, more importantly, the protein production can be scaled up as required.
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Edited by: Rajesh Bihani ( Find me on Google+ )