Newswise — Scientists have created a chicken egg that could potentially provide safety for individuals with allergies to egg whites. Allergies to chicken eggs are highly prevalent among kids, standing as one of the most frequently encountered allergies. While the majority of children overcome this allergy by the age of 16, a portion of them continue to experience egg allergies throughout their adult lives. Egg white allergies can lead to diverse symptoms, such as nausea, abdominal pain, respiratory difficulties, skin rashes, and edema. Additionally, specific flu vaccines may be unsuitable for individuals with egg white allergies.
Using gene editing techniques, scientists have generated an egg devoid of the protein responsible for triggering egg white allergies. This particular protein, known as ovomucoid, constitutes roughly 11% of the total protein content found in egg whites.
A scientific paper published in April 2023 in the journal Food and Chemical Toxicology provides an in-depth analysis of the food safety characteristics of the genetically modified egg known as the OVM-knockout.
"Ensuring the safety of OVM-knockout chicken eggs for consumption necessitates a thorough evaluation. Our study focused on investigating the presence or absence of mutant protein expression, vector sequence insertion, and potential off-target effects in chickens modified with OVM knockout using platinum transcription activator-like effector nucleases (TALENs)," stated Ryo Ezaki, an assistant professor at the Graduate School of Integrated Sciences for Life at Hiroshima University in Hiroshima, Japan. TALENs are a type of restriction enzymes that can identify specific DNA sequences and cleave or fragment them.
To develop the OVM-knockout eggs, the researchers focused on detecting and eliminating the ovomucoid protein within the egg whites. They employed engineered TALENs to target a specific RNA segment called exon 1, responsible for encoding particular proteins. The resulting eggs underwent rigorous testing to ensure the absence of ovomucoid protein, mutant ovomucoid protein, and any unintended off-target effects.
The eggs exhibited the intended frameshift mutation, which occurs when nucleotide bases are inserted or deleted within a gene. Notably, none of the eggs expressed mature ovomucoid proteins. The researchers employed anti-ovomucoid and anti-mutant ovomucoid antibodies to identify any remnants of the protein, but no evidence of ovomucoid was found. This signifies that the presence of mutant ovomucoids does not give rise to new allergens, a crucial aspect in determining the safety profile of the eggs.
Unlike some other gene editing tools, such as CRISPR, which can sometimes result in off-target mutagenesis effects causing unintended mutations, the analysis of the altered egg whites through whole genome sequencing revealed that the observed mutations were not concentrated within the protein-coding regions. This suggests that any mutations that occurred were likely not off-target effects associated with the gene editing process.
"Eggs laid by homozygous OVM-knockout hens displayed no apparent abnormalities," Ezaki explained. "The albumen, or egg white, was devoid of both the mature OVM protein and the OVM-truncated variant." He further noted that any potential off-target effects resulting from TALEN use in OVM-knockout chickens were localized within intergenic and intron regions, rather than protein-coding regions. Moreover, the plasmid vectors employed for genome editing purposes were only transiently present and did not integrate into the edited chickens' genome.
These findings underscore the significance of safety evaluations and highlight that the eggs laid by these OVM-knockout chickens offer a solution to the allergy issue in both food and vaccines.
Moving forward, researchers will persist in conducting thorough assessments of the safety profile of OVM-knockout eggs. Since even small amounts of ovomucoid can trigger severe allergic reactions in highly sensitive individuals, additional immunological and clinical studies are required to ascertain the safety of OVM-knockout eggs. Presently, researchers have established that OVM-knockout eggs exhibit reduced allergenicity compared to standard eggs, making them suitable for incorporation into heat-processed foods that can be consumed by individuals with egg allergies.
Ezaki stated, "The next stage of research will involve evaluating the physical characteristics and suitability of OVM-knockout eggs for various food processing methods, as well as confirming their effectiveness through clinical trials." He further emphasized their commitment to conducting further research aimed at the practical implementation of eggs with reduced allergenicity.
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Other contributors include Tetsushi Sakuma, Mei Matsuzaki, Takashi Yamamoto, and Hiroyuki Horiuchi of the Graduate School of Integrated Sciences for Life at Hiroshima University and Daisuke Kodama, Ryou Sasahara, and Taichi Shiraogawa from the R&D Division of the Institute of Technology Solution at Kewpie Corporation in Tokyo Japan.
The Japan Society for the Promotion of Science KAKENHI (19H03107, 19K22286) and JST COI Grant Number JPMJPF 2010 supported this research.
About Hiroshima University
Since its foundation in 1949, Hiroshima University has striven to become one of the most prominent and comprehensive universities in Japan for the promotion and development of scholarship and education. Consisting of 12 schools for undergraduate level and 5 graduate schools, ranging from natural sciences to humanities and social sciences, the university has grown into one of the most distinguished comprehensive research universities in Japan. English website: https://www.hiroshima-u.ac.jp/en
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