Milk may do a body good, but transgenic researchers are trying to make it do a body better. A new study shows that goat's milk engineered to be more similar to human breast milk reduces the amount of harmful bacteria in piglet guts. Eventually, such dairy animals might improve the health of children in undeveloped countries.
The World Health Organization estimates that approximately 2 million people a year die from bacterial infections that cause diarrhea and dehydration. Young children in developing countries are at greatest risk. That's because, after a child is weaned, it is no longer exposed to a variety of helpful proteins in mother's milk that fight diarrhea-causing pathogens, such as coliform bacteria. One of these proteins, lysozyme, is present in human breast milk at 1600 to 3000 times the concentration found in cow's or goat's milk. But breastfeeding only goes on for so long, and geneticist James Murray and colleagues at the University of California, Davis, have been working to develop goats that produce more humanlike milk for older children.
In 1999, the researchers engineered a dairy goat to make human lysozyme in the same mammary cells that generate other milk proteins, and at about two-thirds the amount as in human milk. Subsequent work showed that the transgenic milk reduced bacterial growth in laboratory cultures, so the team wanted to know if the same would happen in a real gut. To find out, the researchers fed four 2-week old pigs pasteurized transgenic milk and another group pasteurized regular milk for 16 days. Then the team measured the amount of coliform bacteria in the animals' intestines. The piglets drinking regular milk had, on average, between 100 to 4000 times the amount of coliform bacteria in their guts as did those drinking transgenic milk, the team reports in today's issue of Transgenic Research. Although the experiments still need to be done, Murray believes children would also be protected by the transgenic milk because "pigs are very similar to humans in the kinds of E. coli bacteria they harbor."
"This is the first transgenic [animal] to have true benefit for the consumer," says Bill Muir, a population geneticist and environmental risk assessor of transgenics at Purdue University in West Lafayette, Indiana. Other transgenic animals, such as glow-in-the-dark pet fish or fast-growing salmon, might prove economically valuable, but Murray's goat "addresses the dysentery pathogen taking up residence in the gut." Animal scientist Matt Wheeler at the University of Illinois, Urbana/Champaign, says this demonstration of safety and efficacy is the first step before any scientific review boards or the U.S. Food and Drug Administration will allow human consumption of the milk.