Researchers at Hiroshima University have developed a modified chicken egg that they claim “may be safe for people with egg white allergies”.

Using genome editing technology, the scientists have produced an egg called the “OVM-Knockout” that they say does not include ovomucoid, the protein that causes egg white allergies. 

The food safety profile of the modified egg has been examined and the findings were published in Food and Chemical Toxicology in April 2023.

“To use OVM-knockout chicken eggs as food, it is important to evaluate its safety as food,” said Ryo Ezaki, an Assistant Professor at the Graduate School of Integrated Sciences for Life at Hiroshima University in Hiroshima, Japan.

“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),” continued Ezaki.

Providing context, the researchers noted that TALENs are restriction enzymes that recognise specific DNA sequences and break or cut them. To develop the modified eggs, researchers needed to detect and eliminate the ovomucoid protein in the egg whites. TALENs were utilised to target a piece of RNA called exon 1, which codes for specific proteins. The eggs produced from this technique were then tested to ensure there were no ovomucoid protein, mutant ovomucoid protein, or other off-target effects.

The research team claimed that the eggs had the desired frameshift mutation (a mutation created by inserting or deleting nucleotide bases in a gene), and said that none of them expressed mature ovomucoid proteins.

Anti-ovomucoid and anti-mutant ovomucoid antibodies were used to detect any traces of the protein, but there was reportedly no evidence of ovomucoid in the eggs, subsequently meaning that mutant ovomucoids could not create new allergens.

“Other gene editing tools, such as CRISPR, tend to have off-target mutagenesis effects. This means that new mutations are prompted by the gene editing process. However, whole genome sequencing of the altered egg whites showed mutations, which were possibly off-target effects, were not localized to the protein-coding regions,” explained the Hiroshima University researchers.

“The eggs laid by homozygous OVM-knockout hens showed no evident abnormalities. The albumen contained neither the mature OVM nor the OVM-truncated variant,” said Ezaki.

“The potential TALEN-induced off-target effects in OVM-knockout chickens were localized in the intergenic and intron regions. Plasmid vectors used for genome editing were only transiently present and did not integrate into the genome of edited chickens. 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.”

Looking to the future, the researchers have said that they will continue to verify the safety profile of the modified eggs. They have said that this is important as some people are highly allergic to this specific protein, meaning that even small amounts of ovomucoid can cause a reaction.

At present, researchers have determined that the OVM-knockout eggs are “less allergenic than standard eggs and can be safely used 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. We will continue to conduct further research toward the practical application of allergy-reduced eggs,” concluded Ezaki.