Safety Assessment of the Neomycin Phosphotransferase II (NPTII) Protein

Abstract

Two approaches were used to assess the safety of the NPTII protein for human consumption using purified E. coli produced NPTII protein that was shown to be chemically and functionally equivalent to the NPTII protein produced in genetically engineered cotton seed, potato tubers and tomato fruit. The NPTII protein was shown, as expected, to degrade rapidly under simulated mammalian digestive conditions. An acute mouse gavage study confirmed that the NPTII protein caused no deleterious effects when administered by gavage at a cumulative target dosage of up to 5000 mg/kg of body weight. This dosage correlates to at least a million fold safety factor relative to the average daily consumption of potato or tomato, assuming all the potatoes or tomatoes consumed contained the NPTII protein. These results, along with previously published information, confirm that ingestion of genetically engineered plants expressing the NPTII protein poses no safety concerns.

Protein digestibility and relevance to allergenicity.

“…Available data suggest that stability to digestion may not be a universal, defining characteristic of food allergens. Part of the difficulty in interpreting data from in vitro pepsin digestion assays is that different labs utilize different assay conditions (pH, enzyme/protein ratios, detection methods; Fu 2002;Fuchs et al 1993;Noteborn et al 1995;Reed et al 1996). The workshop participants agreed there was a need to harmonize assay conditions for measurement of protein digestion and for a consensus on the most appropriate approach to data interpretation.…”

“…Some studies of effects of proteolytic digestion on allergenicity have used comparatively low ratios (by weight) of enzyme:protein, ranging from 0.1 to 0.01 (Asselin et al 1989;Marquez and Lajolo 1981;Maynard et al 1997;Watanabe et al 1990). However, in vitro digestion assays for the purposes of safety assessment tend to employ higher ratios ranging from 25 to 5,000 (Fu 2002;Fuchs et al 1993;Noteborn et al 1995;Reed et al 1996).…”

The release of genetically modified crops into the environment

“…As indicated above, many concerns have focused on antibiotic resistance genes and their potential to compromise human or veterinary therapy. Previously, detailed risk assessments have been given for the kanamycin resistance gene nptII, still the most popular selectable marker gene for plant transformation (Fuchs et al, 1993;Gay, 2001;Nap et al, 1992). For the detailed considerations, we refer to these papers.…”

Expression and molecular analysis of DsRed and fluorescent genes in tobacco (Nicotiana tabacum L.) / Izražanje in molekulska analiza DsRed in gfp fluorescentnih genov pri tobaku (nicotiana tabacum L.)

“…DNA transfer between transgenic plants and other organisms is unlikely. NptII gene does not signify any risk to human and animal health (Fuchs et al, 1993). Nevertheless, the complete removal of the selection gene is desirable because selection genes are no longer required after selection.…”