December 5, 2023

Egg allergy is one of the most common allergies in children and can be triggered by a variety of foods, even vaccines. Now, researchers have used genome editing techniques to develop an egg that is safe for allergy sufferers to eat.

Allergies are caused by the immune system overreacting to the proteins in eggs. A person can be allergic to either the egg white or the yolk, but an allergy to the egg white is more common. Often, but not always, children outgrow their egg allergies by the time they reach puberty.

Symptoms of an egg allergy vary from person to person, but typically include skin irritation or hives, nasal congestion, runny nose and sneezing, stomach cramps, nausea and vomiting, and difficulty breathing. The worst-case scenario is anaphylaxis, a severe, life-threatening allergic reaction that requires immediate medical attention.

A surprising number of foods contain eggs, powdered or dried, including breadcrumbs and pastes, Caesar salad dressing, crepes and waffles, ice cream, candy, meatloaf and meatballs, marshmallows and marzipan. Additionally, most flu vaccines are produced using egg-based technology.

Now, researchers at Hiroshima University have used the genome-editing technology TALENs to develop an egg free of the troublesome ovomucoid (OVM), which makes up about 11 percent of all proteins in egg whites.

Transcription activator-like effector nucleases (TALENs) are artificial enzymes designed to cleave DNA at specific sequences, thereby breaking its double strands. Once the strand breaks, the cell activates repair mechanisms that reconnect the two sides of the break.

Other gene-editing techniques, such as CRISPR, can have “off-target” effects, meaning that the editing process triggers new mutations. In this case, the problem with off-target effects is the possibility of producing mutated variants of the OVM protein that could still cause allergic reactions.

The researchers designed TALENs to knock out a section of the hen’s RNA called exon 1, which encodes a specific protein. OVM knockout eggs laid by hens were tested for the presence of OVM protein, mutant OVM protein, and any other off-target effects.

The eggs were found to have no obvious abnormalities and contained no traces of OVM or protein mutation variants. While whole-genome sequencing of the altered eggs revealed mutations that suggested off-target effects, they did not affect protein-coding regions.

“These results demonstrate the importance of safety assessment and suggest that eggs laid by this OVM knockout chicken address allergy concerns in food and vaccines,” said Ryo Ezaki, first author of the study.

Knowing that even the smallest amount of OVM can trigger an allergic reaction in some people, and until further testing confirms that the eggs are not allergenic, the researchers are confident that they are less allergenic than regular eggs.

“The next phase of research will be to evaluate the physical properties and processing suitability of OVM knockout eggs, and to confirm their efficacy through clinical trials,” Ezaki said. “We will continue to conduct further research into the practical application of hypoallergenic eggs.”

The study was published in the journal Food and Chemical Toxicology.

source: Hiroshima University