Egg allergies are one of the most common allergies in children and can be triggered by a wide range of food products, even vaccines. Now, researchers have used genome editing technology to develop a chicken egg that may be safe for allergy sufferers to eat.
The allergy is caused by the immune system’s overreaction to the protein found in eggs. A person can be allergic to the white or the yolk, but allergies to egg whites are more common. Usually, but not always, children outgrow their egg allergy before adolescence.
The symptoms of egg allergy vary from person to person but commonly include skin inflammation or hives, nasal congestion, runny nose and sneezing, stomach cramps, nausea and vomiting, and difficulty breathing. The worst-case scenario is anaphylaxis, a life-threatening, severe allergic reaction that requires immediate medical treatment.
A surprising number of food products contain eggs, egg powder, or dried eggs, including breaded and battered foods, Caesar salad dressing, crepes and waffles, ice cream, candy, meatloaf and meatballs, marshmallows and marzipan. In addition, most flu vaccines are produced using egg-based technology.
Now, researchers from Hiroshima University have used genome editing technology, TALENs, to develop a chicken egg that doesn’t contain the troublesome protein ovomucoid (OVM), which accounts for about 11% of all proteins found in egg white.
Transcription activator-like effector nucleases (TALENs) are artificial enzymes engineered to cut DNA at a specific sequence, breaking its double strands. Once the strands are broken, the cell responds by initiating its repair mechanism so that both sides of the break reconnect.
Other gene editing technology, such as CRISPR, can produce "off-target" effects, meaning the editing process prompts new mutations. In this case, the problem with off-target effects is the potential for creating mutant variants of the OVM protein that could still cause an allergic reaction.
The researchers engineered TALENs to knock out a piece of the hen’s RNA called exon 1, which codes for specific proteins. The OVM-knockout eggs laid by the 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 evident abnormalities and contained no traces of OVM or mutant variants of the protein. While whole genome sequencing of the altered eggs showed mutations, suggesting off-target effects, they did not affect the protein-coding regions.
“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 vaccines,” said Ryo Ezaki, lead author of the study.
Knowing that even the smallest amount of OVM can trigger an allergic reaction in some people, until further testing confirms the eggs are non-allergenic the researchers are confident in saying they are less allergenic than normal 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,” said Ezaki. “We will continue to conduct further research toward the practical application of allergy reduced eggs.”
The study was published in the journal Food and Chemical Toxicology.
Source: Hiroshima University
