Development and use of an ELISA test to detect IgE antibody to Cry9c following possible exposure to bioengineered corn.
BACKGROUND
Starlink(TM), a variety of corn genetically engineered to contain the insecticidal protein Cry9c, had not been approved for human consumption because it possessed some characteristics associated with allergenic proteins. However, in the fall of 2000 CRY9C DNA was detected in several corn-containing products, suggesting that Starlink corn had entered the human food supply. Subsequently, consumers, following consumption of corn products, reported a number of adverse health events, possibly consistent with allergic reaction.


METHODS
To investigate the possibility of allergic reactions due to Cry9c in these consumers an ELISA test was developed for the purpose of detecting IgE antibodies to Cry9c and blood samples were taken from a total of 18 people who self-reported allergic reactions. Sera collected prior to the 1996 development of Starlink were used as negative controls.


RESULTS
None of the adverse event sera were found to be reactive with recombinant Cry9c antigen, based on comparison with normal controls. Although a known human positive control serum containing IgE specific for Cry9c was not available, other controls were incorporated into the ELISA protocol, including the use of sera from subjects allergic to other allergens and their homologous antigens (cat, grass, peanut) to validate the IgE detection reagents.


CONCLUSIONS
While the results do not support the likely occurrence of allergic reactions to Cry9c, such reactions cannot be ruled out, nor can the possibility that sera might react with unique glycosylated epitopes of Cry9c that may be expressed in the corn plant/seed.
Raybourne
Richard B
RB
Immunobiology Branch, Food and Drug Administration, Laurel, MD 20708, USA. richard.raybourne@cfsan.fda.gov
Williams
Kristina M
KM
Vogt
Robert
R
Reissman
Dori B
DB
Winterton
Brad S
BS
Rubin
Carol
C
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000009:adverse effects / Q000276:immunology*; D001427:Bacterial Toxins; D004731:Endotoxins / Q000009:adverse effects / Q000276:immunology*; D004781:Environmental Exposure / Q000009:adverse effects; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005512:Food Hypersensitivity / Q000097:blood / Q000209:etiology / Q000276:immunology*; D030841:Food, Genetically Modified / Q000009:adverse effects*; D006460:Hemolysin Proteins; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood*; D030821:Plants, Genetically Modified / Q000009:adverse effects / Q000276:immunology*; D003313:Zea mays / Q000235:genetics / Q000276:immunology*
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D007073:Immunoglobulin E