NZ researchers develop potentially hypoallergenic milk

New Zealand researchers believe they may have bred the first cow in the world to produce hypoallergenic, high-protein milk. The researchers, from NZ’s AgResearch Ruakura campus, published their work in the current issue of Proceedings of the National Academy of Sciences (PNAS) journal.

“This is tremendously significant,” said AgResearch chief executive Dr Tom Richardson. “PNAS is one of the top journals in the world, and to be published in it reflects the world-leading quality of the science behind this discovery. This will be one of the top-ranking science publications from New Zealand this year.”

The research was instigated when the AgResearch team, led by Dr Goetz Laible, wondered whether it was possible to produce milk that contains less of a particular milk protein known to be allergenic.

“We were successful in greatly reducing the amount of beta-lactoglobulin (BLG), a milk whey protein which is not in human breast milk and which can cause allergic reactions,” says Dr Stefan Wagner, one of the lead authors on the paper. “Two to three per cent of infants are allergic to cow’s milk, and BLG allergies make up a large part of that percentage.”

The researchers first engineered a mouse to produce the sheep form of BLG protein in its milk. They used a technique called RNA interference, in which two microRNAs (short ribonucleic acid molecules) were introduced into the mouse to prevent the expression of the sheep BLG protein - resulting in a 96% reduction in the sheep BLG protein in the mouse’s milk.

The next step was to produce Daisy, a female calf that was genetically engineered to express the same two microRNAs to target the BLG protein that is also a normal constituent of cow’s milk. The researchers then hormonally induced Daisy to lactate and found that the resulting milk had no detectable BLG protein.

Unexpectedly, Daisy’s milk also had more than twice the level of the casein proteins that also normally occur in cow’s milk.

“People have long looked into reducing this enigmatic protein, or completely knocking it out, because there has been no definitive function able to be assigned to it. So, we developed this scientific model to investigate the effect of knocking BLG protein out on the composition and functional properties of milk, and to determine whether the absence of BLG produces cow’s milk that is hypoallergenic,” said Dr Wagner.

“This is the real discovery component to this project, and Daisy provides us with the opportunity to answer a lot of those questions.

“To avoid the delay of two years before a natural lactation, the milk we analysed was from an induced lactation. We only obtained small quantities over a few days for these initial studies. We now want to breed from Daisy and determine the milk composition and yield from a natural lactation. We also want to investigate the origin of Daisy’s taillessness, a rare congenital disease in cows.”

According to Malaghan Institute of Medical Research director Professor Graham le Gros, the research could have a significant impact as it has the potential to reduce milk allergies in children, while avoiding the concerns associated with genetic modification of the milk proteins themselves.