Biotechnology Online

'Pharming' proteins

Biopharming

Biopharming, also known as ‘molecular pharming', uses genetically modified (GM) plants or animals to produce pharmaceutical proteins and chemicals such as vaccines, hormones, blood clotting and thinning agents, and industrial enzymes.

Any GM animal or plant used for pharmaceutical or chemical production must be able to produce the desired compound at high levels, while not endangering its own health. It must also be able to pass this ability to its offspring.

Pharming with animals

Some animals have been genetically modified to produce human proteins in their milk. These animals, such as cows, sheep, pigs, goats, rabbits and mice, act as living pharmaceutical ‘factories' .

The section of human DNA containing the genes for the required protein is injected into the animal embryo. The embryo is then placed into the uterus of a surrogate mother where it develops to full term. The adult GM animal's milk produces the human protein, which is purified for therapeutic use for humans.

This technology was first used in 1987. GM mice produced tissue plasminogen activator, a human protein used to treat blood clots. Other research has included:

• cows that produce
  • human serum albumin, used to maintain fluid balance in the blood
  • lactoferrin, a protein from breast milk that promotes infant growth
• sheep that produce
  • factor VIII and factor IX, essential for blood clotting
  • natural anticoagulants used during heart surgery
  • proteins to treat lung and liver disease
• rabbits that produce
  • human lactoferrin
  • human interleukin-2, a protein essential in the immune response to infection and may be useful in fighting some types of cancer.

Pharming with plants

Researchers have discovered a lot about plant molecular make-up — such as proteins, minerals, sugars and fibres — as well as the genes responsible for these components. Plants can be bred to emphasise certain traits, and to overproduce therapeutically-beneficient compounds .

Plants make relatively cheap pharmaceutical and chemical ‘factories'. In the same way that sugarcane is harvested and refined to produce sugar, compounds produced inside a GM plant are extracted and processed after harvesting. Instead of producing a food or fibre product, the end result could be a medicine, a plastic, or even an additive used in the manufacture of paper. For example, researchers in South Africa and England are developing GM tobacco, bananas and potatoes containing a vaccine for human papilloma virus, which causes cervical cancer.

Tobacco, bananas and sugarcane have several advantages for biopharming over other plants:

• tobacco is a non-food crop, reducing the risk of someone accidentally eating a plant containing pharmaceuticals. In Australia , it is also grown in a highly regulated environment.
• bananas are sterile, so there is no risk of the new gene being transferred to other banana plants through cross-pollination.
• sugarcane produces large amounts of plant material or biomass and can also be grown essentially as a sterile crop.

Commercial production of biopharmed pharmaceuticals is still some time away, although some compounds are already produced in plants for laboratory and diagnostic work. Issues of commercial production that need consideration include:

• the large scale of crops required to produce compounds in sufficient quantity
• ensuring that the plants do not cross-pollinate, potentially transferring modified genes to other plant species. One way to prevent this is by creating sterile male plants.

For more information on molecular farming go to: http://www.molecularfarming.com

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