Starlink genetically modified corn and allergenicity in an individual

Abstract

To the Editor: Sutton et al1.Sutton S.A Assaad A.H Steinmetz C Rothenberg M.E A negative double-blind, placebo-controlled challenge to genetically modified corn.J Allergy Clin Immunol. 2003; 112: 1011-1012Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar have proposed that the double-blind, placebo-controlled food challenge (DBPCFC) approach is the ultimate proof of the true allergenicity of Starlink or other transgenic proteins. However, the conclusions based on this approach to the genetically modified corn Starlink containing the Cry9C gene, as arrived at by Sutton et al,1.Sutton S.A Assaad A.H Steinmetz C Rothenberg M.E A negative double-blind, placebo-controlled challenge to genetically modified corn.J Allergy Clin Immunol. 2003; 112: 1011-1012Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar need critical evaluation. The patient investigated by Sutton et al1.Sutton S.A Assaad A.H Steinmetz C Rothenberg M.E A negative double-blind, placebo-controlled challenge to genetically modified corn.J Allergy Clin Immunol. 2003; 112: 1011-1012Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar had complained of 3 allergic reactions after consumption of processed foods containing the transgenic corn at different time periods. However, when the DBPCFC test was conducted with the raw Starlink corn sample that was powdered and placed in a gelatin capsule, the patient did not have any symptoms. Similar observations were also seen in the skin prick test performed on the patient with the same corn specimen extract. A factor that needs to be considered here is the influence of the food matrix. It is relevant to point out that the patient in question had originally consumed processed corn products while he experienced the reactions. The effect of other ingredients or food additives present in the processed corn products on the properties of the Cry9C protein needs to be examined because Martin-Orue et al2.Martin-Orue S.M O'Donnell A.G Arino J Netherwood T Gilbert H.J Mathers J.C Degradation of transgenic DNA from genetically modified soya and maize in human intestinal simulations.Br J Nutr. 2002; 87: 533-542Crossref PubMed Google Scholar had earlier raised the possible influence of food matrices, which are the components of the human diet, on the extent of transgenic DNA degradation and also the ability to form complexes with proteins, including digestive enzymes. The inconsistencies in the results of the Cry9C analysis also need to be considered. When the patient had submitted the corn chip samples for analysis to the US Food and Drug Administration (FDA), they were found to be positive for the Cry9C DNA but not the Cry9C protein. However, analysis of the corn specimen by the patient showed positive results for the Cry9C protein. It is not clear from the observations of Sutton et al1.Sutton S.A Assaad A.H Steinmetz C Rothenberg M.E A negative double-blind, placebo-controlled challenge to genetically modified corn.J Allergy Clin Immunol. 2003; 112: 1011-1012Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar whether the corn specimen used for the DBPCFC study was positive for the Cry9C DNA, the Cry9C protein, or both. According to the ELISA test developed by the Centers for Disease Control and Prevention and the FDA, the blood sample of the patient did not have IgE antibodies directed against the Cry9C protein. While developing the method, the FDA used the recombinant Cry9C protein expressed in Escherichia coli and not the plant-derived protein as the antigen. According to Kuiper et al3.Kuiper H.A Kleter G.A Noteborn H.P.J.M Kok E.J Assessment of the food safety issues related to genetically modified foods.Plant J. 2001; 27: 503-528Crossref PubMed Scopus (435) Google Scholar the epitopes present on Cry9C in maize might not be present in the nonglycosylated E coli–derived protein. They also recognized that a specific goat antiserum against Cry9C was included in the ELISA because of the nonavailability of human serum containing the IgE antibody to Cry9C, which could have resulted in a lack of specificity shown by the ELISA test for human anti-Cry9C IgE. Perhaps a comparative study of the IgE binding could have been carried out with ELISA by using both the microbially derived and the plant-derived Cry9C proteins. Thus the scientific community has to rigorously investigate many of these concerns before concluding unequivocally that the transgenic proteins in Starlink corn are not allergenic, and such unequivocal evidence could be used as a model for proving the safety of genetically modified foods.