Cross-reactivity between mammalian proteins

Background: Cross-reactivity between food allergens occurs when they share part of their amino acid sequence, or when their three-dimensional molecular structure causes them to have a similar capacity to bind specific antibodies. Objectives: To review data from our laboratory on cross-reactivity between mammalian proteins (milk and meat allergens). Methods: Studies used immunoelectrophoresis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis/polyacrylamide gel electrophoresis and immunoblotting), and animal monoclonal antibodies. Results: The findings suggest that animal monoclonal antibodies specific for cow's milk proteins are able to recognize the major part of milk proteins from mammals bred in Mediterranean countries (sheep, goat, and buffalo); weak cross-reactivity was observed with milk proteins from mares and donkeys. None of the antibodies used in our studies reacted with proteins from an exotic mammalian species: the camel. Similar cross-reactions were found with human circulating immunoglobulin E from children allergic to milk. With regard to beef allergy, monoclonal antibodies specific for bovine serum albumin cross-reacted only with ovine serum albumin, whereas the number of sera from allergic children able to recognize other mammalian serum albumins depended directly on the closeness of phylogenetic relationship between animal species and inversely on the percent identity with human serum albumin in the main epitopic sequence. Conclusion: An area of heterogeneity between animal and human species in a critical amino acid sequence (epitope) of an allergen can determine the degree of immunogenic activity.