Animal Pharming - PART 1
Animal Pharming is a portmanteau of the words "farming" and "pharmaceutical" and refers to the use of genetic engineering to insert genes that code for useful pharmaceuticals into host animals that would otherwise not express those genes. More generally, Pharming, refers to using transgenic animals (animals that carry foreign genes in their genome) to produce drugs or other products beneficial to humans. As a consequence, the host animals then make the pharmaceutical product in large quantity, which can then be purified and used as a drug product. Some drug products and nutrients may be able to be delivered directly by eating the plant or drinking the milk. Such technology has the potential to produce large quantities of cheap vaccines, or other important pharmaceutical products such as insulin.
The products of pharming are recombinant proteins or their metabolic products. Drugs made from recombinant proteins potentially have greater efficacy and fewer side effects than small organic molecules (which are often screened as potential drugs) because their action can be more precisely targeted toward the cause of a disease rather than treatment of symptoms. Recombinant proteins are most commonly produced using bacteria or yeast in a bioreactor, but pharming offers the advantage to the producer that it does not require expensive infrastructure, and production capacity can be quickly scaled to meet demand. It is estimated that the expense of producing a recombinant protein drug via pharming will be less than 70% of the current cost. While this idea may not be that new, its implementation is just now beginning to take shape. Numerous companies are springing up all over the world marketing a plethora of these pharmaceutical products. With our current knowledge of what affects embryonic development being limited, the major hurdle to the success of these products is the ethical issues that have arisen through the use of transgenic animals, especially if they are to be used for human consumption.
B. Problems with Bacterial Cell Cultures
Currently, the method of choice for manufacturing many drugs is by laboratory cell culture of bacteria, yeast, or animal cells. There are many drawbacks to this way of mass producing drugs:
1. Cell cultures require constant monitoring and sampling, as cell cultures tend to require precise parameters in order to produce large amounts of protein
2. Expansion is very costly and laborious, as new equipment is required, as is space to store the equipment
3. In order to retain biological activity, many proteins require modifications (addition of sugars, for example), some of which are only performed by mammalian cells.
4. Most cells need to be ruptured (not a trivial procedure if you consider the size of modern bioreactors) to isolate and purify the protein of interest, which is much more difficult than purifying proteins from the blood or milk of an animal.
Even though the initial cost of producing transgenic animals is quite high, using animals as bioreactors is actually a cost efficient alternative to mass produce human pharmaceuticals. One estimate by AviGenics (a private biotech firm, so take these numbers with a grain of salt) states that while modern cell culture costs roughly $100 per gram of protein produced, pharming the same protein cost roughly $2 to $20 per gram if using goat milk, or $0.10 to $0.25 per gram if using poultry eggs. This will mean that the consumer will benefit from receiving pharmaceutical drugs at a fraction of the cost. Therefore, For the biotech company that is producing transgenic animals, and for its investors, the benefits are obvious -- money, and lots of it from pharmaceutical sales. However, pharming can benefit the ordinary person by reducing the cost of pharmaceuticals.
C. Transgenic animal creation
There are many methods available for creating transgenic animals such as: Microinjection, Retrovirus mediated gene transfer, Biolistics etc. Transgenic animals with alterations to the germ line are commonly produced through microinjection Changes to the germ line are heritable from generation to generation within the herd, and this heritability has potential to facilitate long-term productivity gains. For example, fish can be bred for increased expression of a growth hormone, although the industries are currently wary of consumer preferences for gene-modified product. Another example is the recently developed "enviro pig", a pig which had a phytase gene placed in its salivary glands to allow better utilization of phosphorus in feedstuffs.
1. A human gene responsible for producing a desired protein is isolated in a laboratory.
2. An animal is given hormonal treatment to produce a large number of embryos, and the embryos are collected from the oviduct.
3. The human gene is inserted into the fertilized egg via one of the many available methods. In Microinjection, DNA of the pronucleus is injected into the fertilized embryo.
4. The transgenic embryo is placed in a surrogate host which gives birth to the transgenic animal.
5. The offspring is tested for the new gene.
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