Richland, WA (7/16/99)- A genetically modified version of the tobacco
plant appears to offer the promise of a new method for manufacturing therapeutic
proteins that is both cheaper and safer than current methods.
Researchers
at the US Department of Energy's Pacific Northwest National used genetic engineering
techniques to splice human genes for blood clotting factors into tobacco plants.
Plants were created that produced two essential human blood coagulation factors,
factor VIII, and factor XIII, as well as thrombin.
Left- The evil
weed produces human blood proteins
Factor VIII is used to treat hemophilia, a genetic disease in which patients
do not produce the factor and are at risk of bleeding complications. Factor
XIII and thrombin are clotting enzymes essential for wound healing.
Factor VIII is currently one of the most expensive medical treatments there
is. The two available versions are made either by recombinant biotechnology
or by human or porcine cell culture, both of which are painstaking and costly.
The recombinant version was developed after viral contamination of cell-derived
factors wreaked havoc among patients with hemophilia. Some 80 percent of hemophiliacs
over the age of 10 were infected with HIV from receiving blood products prior
to the development of the recombinant version of Factor VIII and better blood
screening programs.
Using genetically engineered plants to produce human blood proteins eliminates
the possibility of transmitting diseases, notes Brian Hooker, a biochemical
engineer at Pacific Northwest, adding:
"In addition to the obvious health benefits, we expect the cost of synthesizing
blood factors in transgenic or genetically modified plants to be 10 times
cheaper than current methods. And, unlike human blood donors or mammalian
cells, plants provide a stable production source and yield much higher amounts
of the desired blood factors."
Tuberous Bioreactors
The Pacific Northwest researchers are using similar techniques to produce
valuable industrial enzymes in non-edible portions of common agricultural
crops. They have already produced potato plants that produce cellulases in
the vines of the plant, as well as the edible tubers that end up as french
fries.
Cellulase is an enzyme used to break down plant material and is used in a
wide variety of applications, from food processing to ethanol production.
The researchers isolated the cellulase-producing genes from bacteria and fungi.
They then spliced the genes into the potato genome in such a way that the
resulting transgenic plant would produce the enzymes in the foliage but not
the roots of the plant.
"The process can be adapted to create additional enzymes such as lipases
and proteases used in pharmaceuticals, specialty chemical and industrial products,"
said Dr. Hooker..
Using plants as bioreactors would be cheaper and easier than labor-intensive
industrial fermentation processes now used to make cellulase and other enzyme
products. In addition, farmers would stand to benefit from growing such two-for-one
crops, he added.
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