Researchers develop allergy-free chicken egg

Scientists from Hiroshima University in Japan have developed a chicken egg that may be safe for people with egg white allergies. One of the most common allergies in children that may be carried into adulthood, egg white allergies can cause a variety of symptoms, including vomiting, stomach cramps, breathing problems, hives and swelling, and some people with egg white allergies are unable to receive certain flu vaccines.

Using genome editing technology, researchers produced an egg without ovomucoid, the protein that causes egg white allergies. It accounts for approximately 11% of all the protein in egg whites.

Research detailing the food safety profile of this modified egg, called the OVM-knockout, was published in Food and Chemical Toxicology.

Ryo Ezaki, assistant professor at the Graduate School of Integrated Sciences for Life at Hiroshima University, said, “To use OVM-knockout chicken eggs as food, it is important to evaluate its safety as food. In this study, we examined the presence or absence of mutant protein expression, vector sequence insertion, and off-target effects in chickens knocked out with OVM by platinum transcription activator-like effector nucleases (TALENs).”

TALENs are restriction enzymes that recognise specific DNA sequences and break or cut them. They were engineered to target a piece of RNA called exon 1, which codes for specific proteins. To develop the OVM-knockout eggs, researchers must detect and eliminate the ovomucoid protein in the egg whites.

The eggs produced from this technique were tested to ensure there was no ovomucoid protein, mutant ovomucoid protein or other off-target effects. The eggs had the desired frameshift mutation and none of them expressed mature ovomucoid proteins. Anti-ovomucoid and anti-mutant ovomucoid antibodies were used to detect traces of the protein, but there was no evidence of it in the eggs. This meant that mutant ovomucoids could not create new allergens, an important step in determining the safety profile of the eggs.

Other gene editing tools, such as CRISPR, have off-target mutagenesis effects, meaning that new mutations are prompted by the gene editing process. However, whole genome sequencing of the altered egg whites showed that mutations, which were possible off-target effects, were not localised to the protein-coding regions.

According to Ezaki, the eggs laid by homozygous OVM-knockout hens showed no evident abnormalities. Any potential TALEN-induced off-target effects were also localised in the intergenic and intron regions and the plasmid vectors used for genome editing did not integrate into the genome of the chickens.

Researchers will continue to verify the safety profile of the eggs, ensuring that they are suitable for people with allergies. Additional immunological and clinical studies need to be performed to further determine their safety. At this time, researchers have determined that the eggs are less allergenic than standard eggs and can be used safely in heat-processed foods that patients with egg allergies can eat.

“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 toward the practical application of allergy-reduced eggs.”

Image credit: iStock.com/krblokhin