Abstract
BackgroundThe central premise for the commercialization of diets with hydrolyzed ingredients is that the small-sized digested peptides would be unable to crosslink allergen-specific IgE at the surface of tissue mast cells and induce their degranulation. Evidence for the validity of this concept to diagnose food allergies in dogs and cats is limited, however. Our objectives were to study the recognition of standard and variably hydrolyzed poultry extracts by sera from dogs and cats with elevated chicken-specific serum IgE.ResultsForty sera from dogs and 40 from cats with undetectable, low, medium or high serum levels of chicken-specific IgE were tested by ELISA on plates coated with the positive controls chicken, duck and turkey meat extracts and the negative controls beef meat (dogs) or wheat (cats). Plates were also coated with a non-hydrolyzed chicken meal, and mildly- or extensively-hydrolyzed poultry feather extracts. The frequencies of dogs with positive IgE against the various extracts were: chicken meat: 100%, duck and turkey meats: 97%, beef meat: 3%, non-hydrolyzed chicken meal: 73%, mildly-hydrolyzed poultry feathers: 37% and extensively-hydrolyzed poultry feathers: 0%. For cats, these respective percentages were (with wheat replacing beef as a negative control): 100, 84, 97, 7, 7, 0 and 0%. To detect any allergenic cross-reactivity between poultry meat-based and feather hydrolysate-derived extracts, an IgE ELISA inhibition was also done. Ten canine sera with the highest level of anti-poultry IgE in the previous experiment were incubated overnight with a previously optimized 50 μg amount of each of the extracts used above. We performed ELISA on plates coated with chicken, duck or turkey meats with or without inhibitors. The median inhibition percentages after incubation with the non-hydrolyzed chicken meal were ~22%, with the mildly-hydrolyzed poultry feathers: 14–22%, and those with the extensively-hydrolyzed poultry feathers: 5 to 10%; the last inhibition level was similar to that of the beef meat negative control.ConclusionsAltogether, these results suggest that an extensive—but not partial—hydrolyzation of the poultry feather extract is necessary to prevent the recognition of allergenic epitopes by poultry-specific IgE.
Highlights
The central premise for the commercialization of diets with hydrolyzed ingredients is that the smallsized digested peptides would be unable to crosslink allergen-specific IgE at the surface of tissue mast cells and induce their degranulation
Animal sera Surplus canine and feline sera submitted to Avacta Animal Health (Wetherby, Leeds, UK) by veterinarians for food allergen-specific IgE serological testing were used for this study
Canine sera were selected according to their original levels of serum chicken-specific IgE (IgE reactivities expressed as optical density, Optical density (OD), values at 405 nm, OD405 uncorrected for background) in the Sensitest commercially available ELISA (Avacta)
Summary
The central premise for the commercialization of diets with hydrolyzed ingredients is that the smallsized digested peptides would be unable to crosslink allergen-specific IgE at the surface of tissue mast cells and induce their degranulation. The characterization of some food allergens for dogs [8, 9], as well as our recent serological study [10], revealed the existence of extensive IgE cross-reactivity among allergens of taxonomically-related food groups in this species. Such studies suggest that some of these “novel” ingredients might cross-react with historically fed components, unless the protein source were evolutionarily distant from all those eaten previously. The points raised above should reduce our confidence in being able to perform “accurately-restricted” dietary trials using so-called “novel” food items
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