Evaluating the Digestion, Absorption, and Transport of Food Allergens

Digestion of food ingredients into useful nutritional components involves complex enzymatic reactions in the digestive tract of humans or for fermented foods, in culture. Microbial enzymes are involved in fermentation, while mammalian enzymes and microbial enzymes are involved in digestion in vivo. The degradation of allergenic proteins into peptides and eventually to free amino acids alters the structure and immunoreactivity of the proteins. This dissertation explores several aspects of allergen digestion. To investigate microbial digestion of milk proteins by means of fermentation, a retail survey of cow’s milk cheeses was performed. Different varieties of cheese are manufactured using diverse microflora and specific ripening conditions that encourage additional proteolysis. Therefore, it was hypothesized that different varieties of cheese would exhibit different patterns of proteolysis and therefore would produce different results when tested by commercial milk enzyme-linked immunosorbent assay (ELISA) kits. ELISA results can be used to semi-quantitatively monitor proteolytic degradation in cheeses due to fermentation. Like microbial digestion during fermentation, gastrointestinal digestion also hydrolyzes allergens into peptides. Peptic and tryptic digestion of a specific peanut allergen, Ara h 2, has been documented to reveal core digestion resistant peptides (DRPs) of approximately 10 and 12 kDa. These digestion-resistant peptides represent a novel target that can be used for monitoring the absorption of allergens across the gut epithelial barrier and the transport and circulation of these allergenic peptides. The uptake and distribution of DRP-Ara h 2 in sera was monitored in sensitized and non-sensitized germ-free C3H/HeN mice at three time points after oral gavage with Ara h 2. The circulation of DRP-Ara h 2 in sera was also monitored over time in three catheterized weaning-age piglets to evaluate transit across the intestinal epithelium in a monogastric animal model. The absorption of DRP-Ara h 2 into the sera and liver as detected by ELISA appeared to be time-dependent. However, differences in uptake and distribution of DRP-Ara h 2 between sensitized and non-sensitized mice were not observed. Future studies with increased challenge doses may demonstrate that sensitization status affects the rate of antigen absorption