Chicken eggs are one of the most common food allergens, especially among children. Many people outgrow their egg allergy, but for those who don’t, avoiding eggs and all of the products that contain them can be a lifetime challenge. Adding to the difficulty: Some vaccines are produced using chicken embryos and contain egg proteins as a result, and they can’t be administered to people with egg allergies. But genetic modification could offer a solution.
Using a targeted gene-editing enzyme to knock out specific protein-coding DNA sequences, scientists can produce a safer chicken egg far less likely to trigger an allergic reaction, according to a recent study published in the journal Food and Chemical Toxicology.
Not only do the edited eggs lack an important allergen, they also seem to be without any unintended, potentially harmful related byproducts. In other words: knocking out the allergy-causing gene doesn’t appear to create additional, dangerous mutations. The modified chicken eggs are safe to eat, say the study scientists.
Past research has demonstrated that genetic engineering could create eggs without ovomucoid protein — the dominant allergen in chicken egg whites that doesn’t go away with heat or cooking. Yet the question of unintended consequences and off-target effects has lingered. It’s possible that some egg genetic modifications might get rid of known allergens but inadvertently produce new ones. Not so with the new research method. The April study builds on previous work by showing it’s possible to make an egg that’s likely both safe for those with known allergies and also unlikely to create others — a more perfect version of what’s often already called the perfect food.
To make their safer egg, the scientists used an enzyme known as TALEN (transcription activator-like effector nuclease). It’s similar to CRISPR in that it snips and edits genetic code according to set markers. However, TALEN is more precise and specific than its CRISPR counterpart — enabling the researchers to minimise the chances of off-target effects.
The biologists injected chicken embryos with the mutating TALEN enzyme, pre-set to excise the genes that code for ovomucoid. Once those embryos grew up and hatched into chickens, the scientists then bred those birds to get homozygous hens with two sets of the mutant gene. These chickens laid eggs lacking any detectable ovomucoid or related proteins, according to follow-up tests.
“The eggs laid by homozygous [ovomucoid]-knockout hens showed no evident abnormalities,” said Ryo Ezaki, the lead study researcher and a biologist at Hiroshima University in Japan, in a press release. “These results indicate the importance of safety evaluations and reveal that the eggs laid by this OVM knockout chicken solve the allergy problem in food and vaccine.”
Though the new research is promising, Ezaki and co. intend to keep conducting further safety tests on their edited eggs. Just a minuscule amount of ovomucoid can cause a reaction for those severely allergic, so more thorough assessment is needed to truly guarantee that none of the problem protein is persisting. Likely, the next step will be clinical trials involving people.