Safety assessment of cre recombinase.
Cre recombinase, when used as a tool in agricultural biotechnology, can precisely excise DNA sequences that may be useful in the introduction of a new trait but are not needed in the commercial product. Although the cre genetic material would not be present in the final product, the present studies were performed to assess the safety of Cre recombinase to provide confirmatory evidence of the safe use of Cre-lox technology in agricultural biotechnology. Cre recombinase shares no relevant sequence similarity to known allergens or toxins. When Cre recombinase was exposed to a pH 1.2 solution of simulated gastric fluid lacking pepsin, CD spectroscopy showed that there was a loss of secondary structure and that the protein was no longer active in a functional assay. Cre recombinase was degraded rapidly when exposed to pepsin in a standardized gastric digestion model; therefore, Cre recombinase would not survive the harsh gastric environment. When orally administered to mice as an acute dosage of 53 mg/kg of body weight, no treatment-related adverse findings were observed. These data support the conclusion that human and animal dietary exposure to Cre recombinase pose no known safety concerns; consistent with the fact that bacteriophage P1, the source of the cre gene and expressed protein, is commonly encountered in the environment and in normal enteric bacteria without reports of adverse consequences.