Antibody-independent identification of bovine milk-derived peptides in breast-milk

Exclusively breast-fed infants can exhibit clear signs of IgE or non IgE-mediated cow’s milk allergy. The definite characterization of dietary cow’s milk proteins (CMP) that survive the maternal digestive tract to be absorbed into the bloodstream and secreted into breast milk remains missing. The aim of this study was to assess the occurrence of CMP-derived peptides in breast milk, using antibody-independent methods. Using high performance liquid chromatography-high resolution mass spectrometry in blinded assays, we identified 11 cow’s milk-derived peptides, including two β-lactoglobulin (2 out 6 samples) and one αs1-casein (1 out 6 samples) fragments, in breast milk from mothers receiving a cup of bovine milk daily. The β-lactoglobulin (β-Lg) fragments, namely f42-54 and f42-57, were absent in milk from mothers who observed a strict dairy-free diet (6 samples). In contrast, neither intact nor hydrolyzed β-Lg was detected by Western blot or competitive ELISA tests. CMP-derived peptides rather than intact CMP may sensitize or elicit allergic responses in the neonate through mother’s milk. Immunologically active peptides from the maternal diet could be involved in priming the newborn’s immune system to drive tolerogenic response in neonates and infants.