New Zealand agricultural scientists have learnt that the calves of a cow modified to have less allergenic milk also have less allergenic milk.
A post on Sciblogs (here) by Dr Grant Jacobs, a Dunedin-based computational biologist, drew AgScience’s attention to the research. He was commenting on an article in the New Zealand Herald, headed GE cow’s offspring show ‘super-milk’ potential.
The research raises hopes of developing a variety of cattle that will produce milk that can be drunk by people with one type of milk allergy.
Dr Jacobs explains that milk allergy is not lactose tolerance.
A number of us are allergic to milk, in a similar way that a number of us are allergic to other types of foods.
β-lactoglobulin is regarded as the main allergen in milk.* (β is the Greek letter, beta; you’ll also see it written beta-lactoglobin.) β-lactoglobulins is considered an important allergen in part because there’s no β-lactoglobulin in human milk.
Around 2-3% of children are allergic to milk. Those with milk allergy can show any of the symptoms of allergy; skin, gastric and breathing problems, including, in rare cases, acute allergic reaction (anaphylaxis).
Usually kids grow out of the allergy, but they carry a higher risk of eczema, egg allergy or allergic asthma in adulthood.
One way to tackle this allergy might be a little prevention: to breed cows that don’t make β-lactoglobulin – without this protein, the allergy problem isn’t there.
The New Zealand researchers blocked the gene that makes β-lactoglobulin.
This way you get just the thing you’re wanting, Dr Jacobs says, and you can try it out on a small scale using a small research team.
One of the great values of genetic engineering is that it enables small teams to do stuff that might otherwise need very large-scale projects.
A catch with the technique they’ve chosen to use, known as RNAi, is that you want to know if the offspring also doesn’t make the protein – is it inherited?
That’s the latest news – they’ve succeeded at that, as you can read in Jamie’s report.
There’s still a long way to go, says Dr Jacobs, “but less-allergenic milk might give an option to those who have developed milk allergy”.
He offers a thought for opponents: if those that don’t want to use milk from cows that were bred to make modified milk, they don’t have to — but there’s no need to block that option for others that do want to.
And he says he would like to learn to what extent the caseins in low β-lactoglobulin milk provokes allergic reactions.
Presumably this milk would be for those allergic to β-lactoglobulin, but not those allergic to caseins.
One line of research suggests that people are allergic to β-lactoglobulin when it lacks iron.** β-lactoglobulins can bind a number of organic molecules, including siderophores. One thing siderophores can do is strongly bind iron. Research has shown that when the β-lactoglobulin protein carries an iron, by holding onto siderophore binding iron it triggers an immune response (e.g. inflammation).
The more widely-known lactose intolerance is because as adults many of us can’t break down & absorb the lactose sugar in milk. It’s more common in non-European people. Since humans starting drinking milk, we’ve started to produce lactase, the enzyme that breaks down lactose, as adults — adaptive evolution in humans as a result of farming! Adapting to produce lactase as an adult has happened several times independently in different parts of the world.
Dr Jacobs reminds us of his earlier discussion in an article about tracking disease and human migration through genetics.