Genetic kingdom: reaping the bounties of our biotech future.

Today's biotechnology includes the use of genetically modified animals in medicine; in the production of special foods, human drugs, and medical devices; in the development of animal and industrial products; and in insect-based pest and disease control. Bioengineered animals are now commonly used for the exploration of medical questions that cannot be readily studied otherwise, such as the mechanisms of both normal physiology and disease in humans and animals. Special pigs, for example, are often used to model human disease, because the size and function of their organs are similar to those of humans. One example is a pig strain bioengineered to test retinitis pigmentosa, a progressive disease that begins with night blindness, and affects between 100,000 and 400,000 people in the U.S. The pig model is intended to help develop drugs to slow the onset and progression of the disease.

Other bioengineered laboratory models include rodents, to study how reborn errors cause disease. Insects and fish are also employed to study disease or population dynamics. Drosophila melanogaster, the common fruit fly some of us remember from our college days, is often bioengineered as a model for developmental studies. Transgenic zebrafish and Amazon mollies are used to study effects of ultraviolet irradiation on melanomas.

More familiar--and controversial--is the use of bioengineered animals to produce certain foods and medical products. Cows can be genetically engineered to make several kinds of specialized milk. They can produce milk with lower levels of a protein that may make the milk more suitable for up to 6 percent of U.S. infants and others allergic to regular cow milk. They can also produce milk that's more digestible for people who are lactose intolerant; milk that has more naturally occurring antimicrobial enzymes, which increase the milk's shelf life; and milk with altered proteins such as caseins, or with lower water content, which facilitates cheese production. Fish can also be modified to make them more nutritious. One example is the modification of rainbow trout to increase the amount of their omega-3 fatty acids, which can help prevent heart attacks. Within the next few years, we're likely to see many more such products.

Genetic engineering can also develop animals capable of producing therapeutic proteins. In general, these proteins will be produced in the milk of cows, sheep, or goats; in chicken eggs; in the semen of swine; or in blood of various large farm species. The advantage of producing these proteins in animals--rather than in cell or tissue cultures, plants, or microorganisms--is significant. The proteins are better adapted to human use, and the yields are higher. In addition, the post-development costs are lower, because raising a herd of dairy cows is cheaper than building and maintaining a bioreactor facility.

The production of the protein alpha-1-antitrypsin in sheep's milk is a good example. This is a human blood protein used to treat hereditary emphysema, cystic fibrosis, and chronic obstructive pulmonary disease, believed to affect more than 200,000 people in the U.S. and Europe. This product is already in clinical trials in Europe. Bioengineered animals could also be useful as a source of transplant organs and for medical products such as spider silk made from goat's milk for sturdy sutures, as replacement tendons, or even for bulletproof vests. Genetic engineering of animals is also being used to create faster-growing, bigger, nutrition-enhanced, or disease-resistant salmon, shellfish, pigs, and many other animals. Several approaches are being investigated to modify mosquitoes so they can't spread malaria or certain fevers. There are also ...