Life-saving drugs could be genetically produced.
Of the 25,000 hemophiliacs in the United States, nearly 90 percent suffer from forms that are treatable with two costly biological drugs known as blood clotting factors 8 and 9.
What if the nation's entire supply of these blood clotting factors could be produced by one farm animal? And with no more discomfort to the animal than being milked?
While this can't be done yet, the possibility is a lot closer, thanks to ARS scientists at the Beltsville, Maryland, Agricultural Research Center.
Researchers at the center successfully implanted a gene from a mouse into several developing pig embryos. The gene--one that produces whey acidic protein (WAP) in the mouse's milk--has neither beneficial nor harmful effect on the pigs.
But the WAP gene is a useful one for genetic engineering for a couple of reasons. For one thing, it's a gene that pigs don't have; when the protein showed up in the pig's milk, it proved that the mouse gene was in place and had turned on with pregnancy, as it is supposed to do. And the quantity turned out was proportional to the sow's size when compared to the mouse.
Furthermore, by splicing useful genes to the WAP gene, scientists may be able to use it like an on/off switch to produce several biological drugs such as blood clotting factors.
ARS' Robert J. Wall says, "This may be a step toward turning the mammary glands of farm animals into a source for uncontaminated life-saving medicines." Wall is an animal physiologist with the Reproduction Laboratory at the Center.
Presently, most biologicals approved as blood clotting factors for hemophiliacs and anti-blood clotting factors used to treat heart attack victims are derived from human blood. Supplies of human blood are subject to shortages and concerns about accidental contamination with pathogens.
Wall believes that genetically engineered farm animals could provide an alternative and possibly safer source of these medicines.
The next step may be to splice the key parts of the WAP gene to genes that code for a desired drug, such as factor 9, a blood clotting substance used to treat a form of hemophilia known as Von Willebrand's disease.
Wall says, "Based on our results so far, a single lactating pig could produce enough to treat every known hemophiliac in the United States."
Although the biological drugs are high in the researcher's priorities, other bioengineered products may follow once the technology is developed.
Cow's milk could be altered to contain more of certain proteins. "A 20-percent increase in the right type of casein would be worth $200 million annually to U.S. cheese producers," says Wall.
Another milk protein, lactoferrin, binds iron, which bacteria need to grow. Wall says that genetically increasing lactoferrin in milk might help control mastitis, a bacterial infection of cow's udders that costs U.S. dairy farmers $2 billion annually. More lactoferrin in sow's milk might help reduce anemia in piglets, which accounts for about $9 million a year in medication costs.
Many of the world's adults have difficulty digesting the milk sugar lactose. Reduction of this component in milk would increase the market for milk and milk products. A low-lactose milk would also benefit premium ice cream manufacturers; lactose forms unwanted crystals in their frozen products.
The best animals to produce biological drugs may be cows or goats, Wall says, although he personally favors goats because of their shorter gestation times.
Beltsville lab technician Lea Schulman couldn't agree more about the best animals. "Anybody who has tried to milk a huge lactating pig"--and she has firsthand experience--"would readily attest to the futility of trying to maintain a herd of dairy sows." Robert J. Wall is at the USDA-ARS Reproduction Laboratory, Bldg. 200, BARC-East, 10300 Baltimore Ave., Beltsville, MD 20705-2350. Phone (301) 344-2362.
PHOTO : Animal physiologist Vernon Pursel at ARS' Reproduction Laboratory prepares an embryo for microscopic examination before implanting it into an animal. (K-4070-17)
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|Title Annotation:||genetically produced animals as source of medicines|
|Date:||Aug 1, 1991|
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