Submitted to: Journal of Allergy Clinical Immunology
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2004
Publication Date: 2/1/2005
Citation: Kopper, R.A., West, C.M., Helm, R.M. 2005. Physiological digestion of peanut proteins in the swine model of food allergy. Journal of Allergy Clinical Immunology. S115(2):133. Interpretive Summary: One characteristic for food allergens includes the stability of proteins to digestion by enzymes found in the gut. However, the laboratory methods used in most studies do not take into account the physiological digestion of a food in the digestive tract. To get a better understanding of the physiological digestion of peanut allergens, a peanut meal was fed to young pigs and the stomach and small intestine contents were sampled at different time points following the meal. The results determined that digestion of peanut allergens by the laboratory methods and the digestion in the intestine of the piglets were similar. However, digestion within a complex food matrix or meal may interfere more with the enzymatic digestion of the allergens in the digestive tract. These results are important to designing future studies on the effects of different diets on food allergies.
Technical Abstract: Rationale: The physiological digestion of peanut protein/allergens has not been critically evaluated. To compare the physiological digestion of peanut proteins/allergens to in vitro pepsin digestion, piglets were administered a peanut meal followed by periodic sampling and analysis of digesta. Methods: Pepsin digestion was used as an in vitro measure of peanut allergen stability. Analysis was performed on gastrointestinal contents collected from piglets fasted overnight and fed a 20 gram bolus of peanut meal. Digesta was sampled beginning at initial feeding and at intervals to 6 hrs. pH was monitored and the GI contents analyzed by SDS-PAGE/immunoblot analysis using serum IgE from peanut-sensitive individuals. Results: Peanut meal neutralized the stomach contents to a pH of approximately 7.0, which was acidified by HCl secretion within 30 minutes. Acidification to pH 2-4, resulted in active pepsin digestion of soluble protein in the stomach. Soluble intact protein/allergens, representative of peanut extracts, were rapidly degraded to pepsin-resistant peptides in the stomach followed by complete hydrolysis of these fragments in the small intestine. Particulate material was evident in both the stomach and small intestine that could contribute to continued release of peanut proteins. Conclusions: Pepsin digestion or simulated digestion resembles true physiological digestion only during intervals of optimal digestive conditions. Gastric pH and continued enzymatic digestion in the gut may play a more prominent role when assessing major and minor allergens within the context of a food matrix or meal and during the sensitization phase of IgE-mediated allergy.