Milk and Egg Derived from Different Species Differ in their Reactivity with Allergen Detection Immunoassays

In the United States, milk and egg are regulated as major food allergens per the allergen labeling requirements of the Food, Drug, and Cosmetic (FD&C) Act. Clinical cross-reactivity has been reported between chicken eggs and eggs from other fowl and cow's milk and milk from other ruminant sources. However, there are no published studies on analytical cross-reactivity for commercial immunochemical assays. This study evaluated milk and egg-specific enzyme-linked immunosorbent assay (ELISA) methods, and the xMAP Food allergen Detection Assay (FADA) for their ability to detect and quantify milk proteins from buffalo, goat, sheep, and camel milk, and egg proteins from quail, duck, and ostrich egg. Results showed that the Morinaga milk (Casein) ELISA, the Veratox Total milk ELISA, and the xMAP FADA were able to detect buffalo milk and buffalo milk products with % reactivities of ≥41% compared to cow's milk; however, low-level detection was observed for sheep, goat, and camel milk. Reactivities compared to the cow's milk were 1-17% for goat and sheep milk. Camel milk resulted in either a <LOQ finding or a % reactivity of ≤0.004% compared to cow's milk. Compared to the chicken egg, Morinaga egg (Ovalbumin) ELISA showed % reactivities of 44-50% for quail egg and 22-23% for duck egg. The % reactivities of the Veratox egg ELISA and the xMAP FADA for duck and quail egg were ≤1.1% compared to chicken egg. Both the ELISAs and the xMAP FADA showed very low reactivities with ostrich egg. Western blots inferred that casein from milk and ovalbumin from egg are the major proteins involved in the antibody binding by the ELISAs. This study provided novel information that can be utilized in developing and validating methods to accurately detect and quantify milk and egg from species other than cow and chicken, respectively, in various food products.