Cas9 in Genetically Modified Food Is Unlikely to Cause Food Allergy

Genome editing has undergone rapid development during the last three years. It is anticipated that genetically modified organisms (GMOs) for food purposes will be widely produced using the clustered regularly interspaced short palindromic repeat/Cas9 (CRISPR)/Cas9 system in the near future. However, the Cas9 gene may then enter the genomes of GMOs for food if the breeding process is not strictly managed, which could lead to the Cas9 protein or associated peptides being produced within these organisms. A variety of peptides could theoretically be produced from the Cas9 gene by using open reading frames different from that of Cas9 in the GMOs. In this study, Cas9 and the peptides potentially encoded by Cas9 genes were studied regarding their immunogenicity, in terms of the digestibility of Cas9 and the homology of the peptides to food allergens. First, the digestibility and thermal stability of Cas9 were studied. Digestibility was tested with natural or heat-denatured Cas9 in simulated gastric fluid in vitro. The two types of Cas9 were digested rapidly. Cas9 was also gradually degraded during heat treatment. Second, the peptides potentially encoded by Cas9 genes were examined for their homology to food allergens. Specifically, an 8-mer exact match search and a sliding 80-mer window search were performed using allergen databases. One of the peptides was found to have homology with a food allergen.