A team of New Zealand-based geneticists has published
a study revealing how it engineered a calf to produce
hypoallergenic milk that allergy-afflicted infants could safely
drink for the first time.
The study, published
in the journal of the Proceedings of the National Academy of
Science, demonstrates how a cow can be genetically engineered
to lack the milk-building beta-lactoglobulin (BLG) protein which is the cause of an
allergy affecting 1.5 per cent of all
"Since the protein is not produced in human
milk, it's not surprising that this protein may be recognised as a
foreign protein in infants and cause allergies," Stefan Wagner, lead
author on the case and molecular biologist at AgResearch,
The team, based in Hamilton, began experimenting with
RNA interference techniques back in 2006, targeting the molecules
responsible for controlling genes that generate proteins. At that
time the test subjects were mice genetically engineered to carry
the BLG protein present in sheep's milk. They discovered that by
introducing two strands of a specific microRNA, the
protein-production in sheep's milk could be stalled and reduced by
96 per cent. The researchers carried out the same process on cow
proteins and injected this new DNA encoding into a cell nucleus.
The nucleus was then transferred into a cow's egg cell which was
fertilised and implanted into another cow.
Around 60 embryos were treated and
implanted in this way, and one female calf (named Daisy)
producing beta-lactoglobulin-free milk was born -- the
immediately apparent side-effect: Daisy was born without a tail.
Other milk protein levels were also higher than normal,
including casein proteins which enhance cheese yields but
also contribute to other allergies.
The team will have to wait until the calf reaches
adulthood to study the effects of the genetic breeding (lactation
was artificially stimulated prematurely using hormones). Until
then, they must refrain from sampling both the milk expressed by
the calf and the cheese they made from it -- according to Wagner,
New Zealand law forbids it.
"We must restrict our research to scientific
analysis," he told Nature. "The current climate for
animal biotech is not very good, and therefore, we are nowhere near
getting this to the consumer."
The find, though surrounded by a few questions marks
over the increase in casein proteins, provides a model for one
day creating disease-resistant animals producing vast quantities of
genetic milk, Wagner hopes.