New Zealand agricultural scientists have learnt that the calves of a cow modified to have less allergenic milk also have less allergenic milk, raising hopes of developing a variety of cattle that those will one type of milk allergy can drink.
Jamie Morton writing in the New Zealand Herald has the story, GE cow’s offspring show ‘super-milk’ potential.
For those reading Jamie’s piece, ‘hypo-allergenic’ simply mean less allergenic. Hypo- is a Greek prefix scientists use to mean under or less. Hyper- is the enlarging counterpart.
Milk allergy is not lactose tolerance. Apparently confusing the two is a fairly common mistake.
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.
What the New Zealand researchers did was to block the gene that makes β-lactoglobulin – this way you get just the thing you’re wanting, 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.
You’ll also see in his report that this work started with a study in mice! It’s often most practical to test the initial ideas on animals that have shorter life cycles, are less costly to breed, and which you can more easily control their environment (including what they are fed).
There’s still a long way to go, but less-allergenic milk might give an option to those who have developed milk allergy.
A thought here for those opposed to GM: 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.
One thing I’d like to learn is 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. I’ve previously touched on how it arose among in North Africa, probably through camel milk, in an article about tracking disease and human migration through genetics.
Remember glass milk bottles?!
Source: Wikimedia Commons, GNU Free Documentation License.
* Caseins in milk can also cause allergic responses. Caseins are found in the solid part of the milk, the curd. β-lactoglobulin is found in the liquid part, the whey. Some people are allergic to one of these, a few to both. If you’re allergic to cow’s milk, you’ll likely be allergic to other animal’s milk too. There are also a few people who are allergic to cow’s milk that are also allergic to soy milk. (Source: Mayo Clinic.)
** The Major Cow Milk Allergen Bos d 5 Manipulates T-Helper Cells Depending on Its Load with Siderophore-Bound Iron
Roth-Walter et al., PLOS ONE, August 12, 2014.