The major peanut allergen, Ara h 2, is resistant to digestion and forms a digestion-resistant peptide (DRP-Ara h 2), which includes previously identified IgE-binding epitopes. The levels of intact peanut protein and/or DRP-Ara h 2 in human serum, saliva, and breast milk were monitored using a competitive inhibition ELISA with a limit of quantitation (LOQ) of 100 ng DRP-Ara h 2/ml body fluid.
The first study monitored levels of both intact peanut protein and DRP-Ara h 2 in serum and saliva of 10 healthy, non-allergic subjects who consumed capsules containing 25 gm of roasted peanut flour (12.75 gm protein). Levels of intact peanut proteins and DRP-Ara h 2 were measured over 24 hours in serum and saliva using a commercial peanut ELISA and an optimized competitive inhibition ELISA, respectively. Intact peanut protein was not found in sera or saliva over the course of the study whereas DRP-Ara h 2 was detected in both body fluids. Peak levels of 248 ng DRP-Ara h 2/ml of serum and 4890 ng/ml of saliva were detected over the time course of this study. Demonstration of the stability and distribution of digestion-resistant peanut allergens in human body fluids over an extended period of time may provide insight into potential risks posed by exposure to allergenic proteins in saliva.
The second study monitored the levels of intact peanut protein and DRP-Ara h 2 in breast milk taken at baseline and 7 days after the start of a low-allergen or control diet. Thirty-eight subjects (20 low-allergen diets and 18 control diets) were included in the study. No intact peanut proteins were detected in samples at baseline or on Day 7. An average of 1050 ng DRP-Ara h 2/ml breast milk was detected in 35 of 38 subjects at baseline. DRP-Ara h 2 was detected in all breast milk samples on Day 7 from subjects on the low-allergen diet. DRP-Ara h 2 present in breast milk could lead to sensitization of exclusively breastfed infants.
