Scientists create OVM-knockout egg, allergy-free and safe for all

Ovomucoid accounts for 11% of all protein contained in egg whites and plays a role in protecting the embryo in the egg from harmful microbes. 

“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),” said Ryo Ezako, an assistant professor at the Graduate School of Integrated Sciences for Life at Hiroshima University, Japan.

How did they do it?

To detect and isolate the ovomucoid protein, researchers engineered TALENs to target exon 1, a vital region of the gene that contains information for protein translation and gene regulation.

The eggs produced were then tested for the absence of ovomucoid protein, its mutant proteins, and other off-target effects.

The team observed that these engineered eggs exhibited frameshift mutation – mutation created by inserting or deleting nucleotide bases in a gene as desired.

Further testing using anti-ovomucoid and anti-mutant ovomucoid antibodies confirmed the lack of any traces of the allergen protein, confirming the eggs to be safe.

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

The research, supported by the Japan Society for the Promotion of Science KAKENHI, will continue to verify the safety profile of allergy-free eggs. Ovomucoid is potent, with tiny traces setting off reactions. Although it is determined at this phase that OVM-knockout eggs are less allergenic than standard eggs and are safe for use in heat-processed foods without any threat of triggering allergies, the team will further analyze their physical properties and processing suitability and confirm efficacy through clinical trials.

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

Study Abstract:

Among the major egg allergens, ovomucoid (OVM) is very stable against heat and digestive enzymes, making it difficult to remove physiochemically and inactivate allergens. However, recent genome editing technology has made it possible to generate OVM-knockout chicken eggs. To use this OVM-knockout chicken egg as food, it is important to evaluate its safety as food. Therefore, 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 TALENs. The eggs laid by homozygous OVM-knockout hens showed no evident abnormalities, and immunoblotting showed that the albumen contained neither the mature OVM nor the OVM truncated variant. Whole genome sequencing (WGS) revealed that the potential TALEN-induced off-target effects in OVM-knockout chickens were localized in the intergenic and intron regions. The WGS information confirmed that 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 evaluation and reveal that the eggs laid by this OVM knockout chicken solve the allergy problem in food and vaccines.