Search

Enzyme-linked immunosorbent assay (ELISA) is the most convenient method of monitoring the occurrence of IgE antibodies specific for novel proteins in genetically modified (GM) foods. The levels of IgE specific for a recombinant protein, Cry1Ab, were determined using an ELISA method. A soluble form of the Cry1Ab protein purified from pCold1 vector-transformed Escherichia coli pTf16/BL21 was used as the ELISA coating antigen, and 1M NaCl was used as the washing buffer to remove IgE non-specifically bound to the coated antigen. Sera from 44 patients allergic to major food allergens were obtained, diluted 20-fold, tested, and found no identifiable IgE above background levels. We also tested sera from patients with corn allergy against whole extracts of non-GM and GM-corn (MON 810) using immunoblotting. The staining patterns were similar for the two types of corn. These results indicate that significant levels of IgE antibodies specific to Cry1Ab were not found in the sera of Japanese patients with food allergies.

Subchronic animal feeding studies to examine the effect on the immune system of genetically modified corn CBH351, which contains the Cry9C protein derived from Bacillus thuringiensis subspecies tolworthi, were conducted in female BN rats and B10A mice. The studies were designed to compare the effect of a line of genetically modified corn CBH351 (GM corn) with that of isoline corn (non-GM corn). Heat-treated corn meal was incorporated into the diets of the rats and mice at a concentration of 50%. The study duration was 13 weeks. Growth, food intake, and organ weights of the thymus, spleen, and liver were compared between animals fed the non-GM and GM lines. The histological findings in thymus, spleen, mesenteric lymph nodes, Peyer's patches, small intestines, liver, kidney, and bone marrow, and the presence of Cry9C-specific IgE, IgG, IgG1 and IgA antibodies in serum were also compared. The results showed no significant differences in growth, feeding value, or the histological findings in immunity-related organs between the animals fed the GM and non-GM lines. Production of Cry9 C-specific IgE and IgA was not detected in the serum of either group. Production of Cry9C-specific IgG and IgG1 was slightly increased in the 50% GM groups of BN rats. No Cry9C-specific IgG or IgG1 was detected in the serum of BN rats fed the diet containing 5% GM-corn In conclusion, no immunotoxic activity was detected in the GM-corn-fed rats and mice in this subchronic dietary study.

We performed experiments on in vitro digestion of newly expressed proteins by SGF (simulated gastric fluid) and SIF (simulated intestinal fluid) to assess the allergenicity of food components derived from biotechnological modification. For newly expressed proteins, we chose CP4-EPSPS (5-enolpyruvylshikimate-3-phosphate synthase from Agrobacterium sp. strain CP4) and Cry1Ab derived from Bacillus thuringiensis subsp. kurstaki strain HD-1. The former is expressed in GM-soybeans and the latter is expressed in GM-corns. Firstly, we examined the digestibility of purified CP4-EPSPS and Cry1Ab by SGF. Both proteins were rapidly digested within 60 sec. After preheating, the digestibility by SGF was slightly increased. Secondly, CP4-EPSPS in GM-soybean extracts and Cry1Ab in GM-corn extracts were digested by SGF. The digestion time of both proteins by SGF was almost the same as that of the purified proteins. Thirdly, the digestibility of CP4-EPSPS and Cry1Ab by SIF was examined. The digestion time of these proteins was 240 min or more. However, digestibility of these proteins by SIF was dramatically increased by preheating, and the digestion time was less than 5 sec. Fourthly, CP4-EPSPS in GM-soybean extracts and Cry1Ab in GM-corn extracts were digested by SIF. Digestion time of both proteins by SIF was almost the same as that of the purified proteins. From these results, we concluded that the digestibility of both CP4-EPSPS and Cry1Ab by SGF and SIF was increased by preheating. Therefore, we suggest that the allergenicity of both proteins should be extremely low because of the easy digestibility of these proteins by SGF and also by SIF with preheating.