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COMPARISON OF SUBCUTANEOUS AND ORAL ROUTES OF EXPOSURE FOR EVALUATING ALLERGENICITY OF FOOD EXTRACTS
Citation:
BOWMAN, C. AND M. K. SELGRADE. COMPARISON OF SUBCUTANEOUS AND ORAL ROUTES OF EXPOSURE FOR EVALUATING ALLERGENICITY OF FOOD EXTRACTS. Presented at 45th Annual Society of Toxicology Meeting 2006, San Diego, CA, March 05 - 09, 2006.
Description:
Evaluation of the potential for food allergenicity of any given protein is limited by the lack of an appropriate animal model. In this study we examined the intrinsic allergenicity of foods known to be allergenic (peanut, egg) or non-allergenic (spinach) by exposing mice either subcutaneously or orally with or without cholera toxin (CT) as an oral adjuvant. C3H/HeJ mice were subcutaneously (s.c.) injected (60 ug total protein) or orally gavaged (1 mg total protein) with commercially prepared, acetone-defatted extracts of raw or roasted peanut, egg white, or spinach. Levels of extract-specific serum IgG and IgE were measured. Injection of all food extracts elicited 2 to 4-fold increases in extract-specific IgE and 3 to 9-fold increases in IgG compared to controls. Although all food extracts caused similar increases in antibody levels after s.c. injection, we observed differences among extracts in their ability to elicit responses when given orally with CT as an adjuvant. Exposure to raw or roasted peanut resulted in significantly elevated IgG and IgE responses. However, neither IgG nor IgE responses in animals orally exposed to egg white or spinach with CT were significantly higher than those of controls. Not surprisingly, oral exposure to food extracts in the absence of CT did not elicit food-specific antibody responses. The differences observed among antigens using the oral route of exposure correlate with the differences in digestibility observed in vitro for these antigens, i.e. spinach is more digestible than egg, while egg is more digestible than peanut. Digestibility has been implicated as an important factor in allergenicity. Our data suggest that intrinsic differences in allergenicity among peanut, egg and spinach antigens cannot be distinguished by subcutaneous injection. However, oral administration of proteins, which includes digestion, while overcoming oral tolerance with an adjuvant (in this case cholera toxin) may allow us to evaluate the potential allergenicity of proteins using a more relevant route of exposure. (This abstract does not reflect EPA policy).