Farmaceutical: A medically valuable compound produced from modified agricultural crops or animals (usually through biotechnology).
Many pharmaceutical drugs in the form of complex proteins require 3D structures that are important for their functions. Animal cells have unique machinery to make special structures. Genetically engineered (transgenic, GMO) animals/animal cells are created so they serve as “bioreactors” to produce these drugs at an industrial scale. Animal products such as milk, egg white, blood, urine, and silkworm cocoons have been used to produce complex drugs that can’t be made by chemical synthesis. The first drug produced by GMO animals, anti-thrombin III from the milk of transgenic goats, prevents the formation of small blood clots that could break loose and plug other vessels (Figure 1). It was approved by the FDA in 2009. Animal cells and simple bacteria, however, have been used to produce protein drugs much earlier than that. For example, Activase® (r-tPA), produced by cells from Chinese hamsters, was approved by the FDA to treat stroke in 2001. The first bacteria-produced drug, Humulin (human insulin) from Eli Lilly has been used by millions if not billions since 1982. Today, many cancer drugs such as monoclonal antibody therapeutics are produced by animal cell cultures after human genes are introduced to these cells. Pharmaceuticals from GMO animals/GMO cells/GMO bacteria will continue to be developed to save lives.
Advances in transgenic technology provide the opportunity either to change the composition of milk or to produce entirely novel proteins in milk (Table 2). The improvement of livestock growth or survivability through the modification of milk composition involves production of transgenic animals that: (1) produce a greater quantity of milk; (2) produce milk of higher nutrient content; or (3) produce milk that contains a beneficial ‘nutriceutical' protein. The major nutrients in milk are protein, fat, and lactose. By elevating any of these components, we can impact the growth and health of the developing offspring. Cattle, sheep, and goats used for meat production can benefit from increased milk yield or composition. In tropical climates, heat-tolerant livestock breeds such as Bos indicus cattle are essential for the expansion of agricultural production. However, Bos indicus cattle breeds do not produce copious quantities of milk. Improvement in milk yield by as little as 2-4 liters per day may have a profound effect on weaning weights in cattle such as the Nelore or Guzerat breeds in Brazil (Figure 2). Similar comparisons can be made with improving weaning weights in meat-type breeds like the Texel sheep and Boer goat. This application of transgenic technology could lead to improved growth and survival of offspring.
| Protein Expressed | Species Where Expressed | Promoter | Reference |
| Lysozyme | goat | Bovine αs1-casein | (Maga et al. 2006) |
| Lysostaphin | cattle | Ovine β-lactoglobulin | (Wall et al. 2005) |
| Bovine β and κ casein | cattle | Bovine β-casein | (Brophy et al. 2003) |
| IGF-I | pig | Bovine α-lactalbumin | (Donovan et al. 2001) |
| α-lactalbumin | pig | Bovine α-lactalbumin | (Bleck et al. 1998) |
| IGF-I | rabbits | Bovine αs1-casein | (Wolf et al. 1997) |
| Lactoferrin | cattle | Bovine αs1-casein | (Krimpenfort et al. 1991) |
| Table 2: Mammary expression of transgenic proteins. | |||
The overexpression of beneficial proteins in milk through the use of transgenic animals may improve growth, development, health, and survivability of the developing offspring. Some factors that have been suggested to have important biological functions in the neonate that are obtained through milk include IGF-I, EGF, TGF-β, and lactoferrin (Grosvenor et al. 1993).
