Human milk proteins may interfere in ELISA measurements of bovine β-lactoglobulin in human milk

It is widely believed that cow's milk proteins ingested by the mother, in particular p-lactoglobulin (β-LG), can pass into breast milk and thus sensitize predisposed infants. However, studies to evaluate bovine β-LG in human milk have given conflicting results. The aim of this study was to analyse the correlation between the amount of cow's milk in the mother's diet and the presence of bovine β-LG in breast milk. Human milk samples from 14 healthy non-atopic women on diets with different cow's milk contents were examined. The total concentration of bovine β-LG or β-LG immuno-like proteins (β-LGIP) was determined by enzyme-linked immunosorbent assay (ELISA). Two separation procedures utilizing ELISA plates and an affinity chromatography column were set up to identify the human whey components recognized by the anti-β-LG antibodies. β-LGIP reactivities of milk from three groups on different diets were not significantly different. After splitting the antigen-antibody complexes, three main protein components, human lactoferrin, human p-casein and human α-lactalbumin, were identified. This study would suggest that, at least in healthy subjects, false-positive results in ELISA determinations of bovine β-LG in human milk might be due to cross-reactions between polyclonal antibodies and different protein antigens.