Genetically modified eggs for allergy sufferers
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Genetically modified chickens lay eggs that do not contain the protein ovomucoid. The eggs can therefore also be eaten by people with a food allergy.
Hiroshima (Japan). Chicken eggs are one of the main causes of allergic reactions in humans. Symptoms of food allergy include itching of the oral mucosa, redness, wheals, and swelling of the skin that appear within minutes to an hour after eating. In exceptional cases, anaphylactic shock with circulatory arrest and shortness of breath can also occur.
Researchers at Hiroshima University led by Ryo Ezaki have now developed a chicken egg that can be safely eaten by people with an allergy to protein. According to their publication in the specialist magazine Food and Chemical Toxicology To do this, they used genetic engineering to remove the proteins from the egg that trigger the food allergy. In conventional eggs, the problematic protein ovomucoid makes up about eleven percent of the proteins found in the albumen.
“In order to use OVM-knockout chicken eggs as food, it is important to assess their food safety. In this study, we examined the presence or absence of mutant protein expression, insertion of vector sequences, and off-target effects in chickens knocked out with OVM by platinum transcription activator-like effector nucleases (TALENs).”
Removed protein ovomucoid from eggs
In order to create the OVM-knockout eggs, the researchers needed to identify and remove the ovomucoid protein in the egg whites. TALENs were designed to target a piece of RNA called exon 1, which encodes specific proteins. The eggs produced in this way were then tested to ensure that no ovomucoid protein, mutant ovomucoid protein, or other undesirable side effects were present.
The eggs had the targeted frameshift mutation, a mutation created by the insertion or deletion of nucleotide bases in a gene, and none of them expressed mature ovomucoid proteins. Anti-Ovomucoid and Anti-Mutant Ovomucoid antibodies were used to search for traces of the protein, but no ovomucoid could be detected in the eggs. This means that mutated ovomucoids could not create new allergens. This is a significant advance in determining the safety profile of the eggs.
Hens show no abnormalities
Eggs laid by OVM-knockout hens showed no obvious abnormalities, according to Ezaki. Neither the mature OVM nor the truncated OVM variant were contained in the albumen. Possible off-target effects induced by TALEN in OVM-knockout chickens could be restricted to the intergenic and intron regions.
The plasmid vectors used for genome editing were transient and did not integrate into the genome of the engineered chickens. These findings highlight the importance of safety assessments and show that the eggs laid by these OVM-knockout hens could solve the allergy problem in food and vaccines.
Safety profile of OVM knockout eggs
Going forward, the researchers plan to continue to validate the safety profile of the OVM-knockout eggs. Due to the fact that some people are very allergic to this particular protein, even small amounts of ovomucoid can trigger a reaction. Additional immunological and clinical studies are necessary for a final safety determination of the OVM knockout eggs. So far, scientists have found that OVM knockout eggs are less allergenic than regular eggs and are safe to use in heat-treated foods that can be consumed by egg-allergic patients.
Ezaki explained that the next phase of research involves evaluating the physical properties and processing suitability of OVM knockout eggs, and their effectiveness needs to be confirmed by clinical trials. He reiterated the researchers’ commitment to continue further investigations towards a practical application of allergy-reduced eggs.
Food and Chemical Toxicology, doi: 10.1016/j.fct.2023.113703