Antigenicity for Humans of Cow Milk Caseins, Casein Hydrolysate and Casein Hydrolysate Fractions

Nentwich I . , Szépfalusi Zs. , Kunz C. , Spuergin P. , Urbanek R.: Antigenicity for Humans of Cow Milk Caseins, Casein Hydrolysate and Casein Hydrolysate Fractions. Acta Vet. Brno 2004, 73: 291-298. Cow milk casein consists of several fractions each of which have different structure and differing antigenicity. The aim of the study was to investigate the capacity of cow milk casein, casein fractions, casein hydrolysate and its fractions to bind human IgG antibodies (antigenicity). Whole cow milk, bovine casein, α-casein native and dephosphorylated, βand κ-casein, further a casein hydrolysate and its fractions were incubated in a IgG-ELISA assay with sera from five patients with cow milk intolerance and a pooled control serum from milk drinking healthy individuals. In healthy controls, predominantly β-caseins, both commercial and chromatographically separated, contained the strongest antigenic epitopes. In milk intolerant infants, however, κ -casein along with β-caseins was the strongest antigen. The antigenicity of the casein hydrolysate compared to nonhydrolysed casein was reduced down to 18.5 and 41.8% measured with patient and control sera, respectively. There were traces of intact protein in the hydrolysate. Antigenicity of the casein hydrolysate fractions reached only 24 to 44% of the antigenicity of the whole hydrolysate. Although their antigenicity roughly correlated with their molecular weight, only negligible differences among particular fractions were found. Cow milk beta-casein is the strongest antigen in healthy controls while kappa-casein possesses the high antigenicity in the milk intolerant individuals. For milk intolerant individuals, the tested casein hydrolysate was approximately 5 times less antigenic compared to whole casein. Antigenicity of the hydrolysate fractions were lower than that of the whole hydrolysate. Identification of cow milk caseins and its fractions with the highest bindnig capacity for human IgG antibodies is important for manufacturing of antigen-reduced formulas based on casein hydrolysates. Cow milk, caseins, infants, IgG, protein hydrolysates Cow milk proteins belong to the strongest antigens in human diet. Caseins, representing about 80% of all cow milk proteins (Eigel et al. 1984), have a fibrilar structure consisting of mainly sequential epitopes able to bind to specific IgG antibodies. Antigenic reactivity of a protein refers to its capacity to bind specifically to the functional binding sites or paratopes of certain immunoglobulin molecules (van Regenmortel 1988). This is different among proteins due to the manifold quality and quantity of their specific epitopes. Using heat treatment and/or enzymatic hydrolysis, a reduction of the binding capacity of the proteins can be achieved. To study antigenicity of cow milk proteins and protein fragments sera from immunized animals on one hand and from sensitized human individuals on the other hand, can be used (Otani 1989; Otani et al. 1989). Comparing antigenicity of casein hydrolysate to that of raw casein gives information on the efficacy of hydrolysis performed. Assessment ACTA VET. BRNO 2004, 73: 291-298 Address for correspondence: MUDr. Ivo Nentwich, Ph.D. c/o Prof. MUDr. J. Lokaj, CSc. Institute of Clinical Immunology and Allergology Faculty of Medicine, Masaryk University Brno Pekafiská 53, CZ-656 91 Brno, Czech Republic Phone: + 420 543 183 126 Fax: + 420 543 183 143 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm