Kewpie and Hiroshima University have removed ovomucoid in chicken egg by genome editing. They succeeded in completely eliminating the obomucoid epitope by placing a deletion just behind the translation start point and causing a frameshift. They have also succeeded in suppressing off-target cleavage by using the TALEN technology of Platinum Bio.
The obomucoid accounts for 11% of the protein in egg whites. It is known to remain immunogenic even after heating. Therefore, “egg white” and “ovomucoid” are examined as separate items in allergy tests. This is because people who are allergic only to egg white can eat heated eggs, but those who are allergic to ovomucoid cannot .
Two strains were created using two major chicken breeds, the yellow-spotted Plymouth Rock and the Rhode Island Red. The macular Plymouth Rock breed had a 16-nucleotide defect and the Rhode Island Red breed had a 10-nucleotide defect, both of which resulted in a frameshift that prevented normal obomucoid production. The deletion also hit the signal peptide, and since the signal peptide was also mutated, the mutated protein does not accumulate in the chicken eggs. Whole genome analysis also confirmed that no off-target cleavage occurred.
Regarding future development plans, vaccines produced with chicken eggs is being considered. Research on ovomucoid-eliminated eggs has been ongoing since 2013, and has been selected as a “full-scale type” with a large budget under the Japan Science and Technology Agency’s COI-NEXT (Co-Creation Opportunity Formation Support Program) from 2022.