Identification of the human beta-casein C-terminal fragments that specifically bind to purified antibodies to bovine beta-lactoglobnlin

The presence of foreign proteins in human milk after the ingestion of bovin e dairy products is thought to be one of the possible causes of allergic se nsitization in exclusively breast-fed predisposed infants. The immunologic determination of bovine beta-lactoglobulin (LC) concentration in human milk has been reported by several researchers, but the results are conflicting. Moreover, a strong cross-reactivity between antibodies to bovine beta-LG a nd human milk proteins and peptides was reported, throwing doubt on the rel iability of radioimmunoassay and enzyme-linked immunosorbent assay detectio n and quantification assays for bovine beta-LG in human milk. Thus, the goa l of this study was to isolate human milk peptides with a molecular mass gr eater than or equal to 1,000 Da cross-reactive with antibodies to bovine be ta-LG in order to identify possible common epitopes between human and bovin e milk proteins. The proteins were first isolated by affinity chromatograph y with purified polyclonal antibodies to bovine beta-LG, followed by gel fi ltration fast phase liquid chromatography and reverse phase-high performanc e liquid chromatography purification of the components specifically bound i n the affinity separation step. Affinity-bound peptides were identified by determining their amino acid sequence. All the sequenced peptides belonged to the C-terminal part of human beta-casein, which confirms the cross-react ivity of human milk proteins and peptides with antibodies to bovine beta-LG and allows the identification of possible common epitopes between the two proteins No bovine beta-LG peptides with a molecular mass greater than or e qual to 1,000 Da were found in our milk samples from healthy mothers on a d iet rich in bovine milk and dairy products. (J. Nutr. Biochem. 11:332-337, 2000) (C) Elsevier Science Inc. 2000. All rights reserved.