Posted on 10/11/2012 at 09:05:17 AM by Student BloggerBy Sylvia Ley
A recent publication by New Zealand researchers has gained media attention. TIME published an article called, “Researchers Genetically Modify a Cow to Produce Low-Allergy Milk” (1). The term “low-allergy” milk attracted my attention enough to look for the original paper published in The Proceedings of the National Academy of Science (2).
About 2-3% of infants are allergic to cow's milk protein during the first year of life. Cow's milk contains the protein called beta-lactoglobulin (BLG). The BLG protein, which is not present in human milk, is known to cause allergic reactions. Researchers led by Dr. Goetz Laible from AgResearch reported that they have genetically engineered a calf named Daisy who produces BLG-free milk.
Before Daisy, Dr. Laible and colleagues tested the process in a cheaper mouse model. Because a mouse does not naturally express the BLG protein, a mouse was engineered to produce the sheep BLG protein in mouse milk. Two microRNAs were then introduced into the mouse to knock-down the expression of the BLG protein employing a RNA interference technique. This resulted in 96% reduction of the BLG protein in mouse milk. They then produced a female transgenic calf engineered to express the same two microRNAs targeting the BLG protein. The transgenic calf, Daisy, was then hormonally induced to lactate. After assessed by a number of different techniques (i.e. the Coomassie blue staining, Western, and HPLC), Daisy's milk was determined to contain no detectable BLG. Researchers also reported that the milk had altered protein composition to compensate for missing BLG. The whey-to-casein ratio in Daisy's milk was 4:96 compared to 21:79 in wild-type normal cow's milk.
The implication of such a drastic whey-to-casein ratio change will need further investigations before human infant consumption. It also raises other safety concerns including whether composition of other bioactive components in milk was altered through the process. Although the BLG protein was not detected in this paper, further investigation is needed to confirm whether Daisy's milk is hypoallergenic to human. Another question to consider is whether this procedure will lead to cost-effective ways to supply hypoallergenic milk. Will Daisy continue to produce BLG-free milk? Can she live a healthy long lactating life? Also, this genetically modified animal product will have to be approved by food safety regulatory bodies before reaching consumers. After Daisy's milk passes this long process, her milk will have to compete with hydrolyzed whey protein formula and soy formula that are currently marketed to infants with cow's milk allergy, when mother's breastmilk is not available.
This is an interesting research finding which will likely have an impact on future agricultural and food research work. As for application for human consumption, it seems to have a long way to go before this milk reaches human infant formula shelves in our grocery stores.