Reduction of whey protein allergenicity by processing.
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Animals↗
Biomedical subjects
J C Monti
Publications and source records attributed to J C Monti.
Anti-bovine beta-lactoglobulin antibodies react with a human lactoferrin fragment and bovine beta-lactoglobulin present in human milk.
Human milk samples react against anti-bovine beta-lactoglobulin rabbit antibodies, as measured by a competitive radioimmunoassay. Immunoreactivity was positive even in milk from mothers consuming a diet free of cow's milk. An increase with a diet rich in cow's milk proteins was detected by immunoelectrophoresis. The human milk fraction cross-reacting with anti-bovine beta-lactoglobulin antibodies corresponds to the 20 kDa fragment from the N-terminal end of human lactoferrin. Three regions of this fragment exhibit sequence homology with a sequence contained in cow's beta-lactoglobulin (between residues 124 and 141).
Amino Acid Sequence↗
Trypsin in human milk.
Human milk trypsin was purified by adsorption chromatography on cellulose-bound 4-aminobenzamidine; its molecular weight was about 24,000 daltons. Its concentration determined by a radioimmunoassay varies between 2.9 and 5.6 micrograms/l.
Chromatography, Affinity↗
Allergenicity of whey protein: its modification by tryptic in vitro hydrolysis of the protein.
Enzymatic in vitro hydrolysis was evaluated as a possible treatment to abolish the allergenicity of whey proteins in view of their use in infant formulas. Guinea pigs without prior immunological contact (including fetal life) with cow's milk were fed various preparations of cow's milk proteins. Oral exposure to milk or untreated whey protein led to anaphylactic sensitization of the animals. In contrast, trypsin-hydrolyzed whey protein and a peptide preparation produced from the tryptic hydrolysate by ultrafiltration were devoid of sensitizing capacity by the oral route. The hydrolysate (crude or purified) was also ineffective in triggering local or systemic anaphylaxis in previously sensitized animals.
Anaphylaxis↗
Lysozyme, an abomasal enzyme in the ruminants.
A strong lytic activity against Micrococcus luteus was demonstrated in abomasal secretions from calf, adult cattle, goat and sheep. This bacteriolytic activity was undetectable in other secretions. Bacteriolysis was caused by a glycosidase displaying endo-N-acetylmuramoylhydrolase specificity (EC 3.2.1.17) and was further characterized in the calf. This lysozyme also displayed significant chitinase activity. Immunofluorescence microscopy confirmed the secretion of lysozyme by abomasal gastric glands exclusively. Electrofocusing revealed multiple molecular forms, the predominant one (more than 80%) being characterized by Mr approx. 15,000, pH optimum 5.0, pl 7.5 and remarkable conformational stability. The lytic activity of lysozyme was ionic strength dependent and competitive inhibition was observed with both N-acetyl glucosamine and N-acetyl-muramic acid. Amino-acid analysis demonstrated common characteristics with known lysozymes, i.e. four disulphide bridges, two proline and N-terminal lysine. Structural homology between the three ruminant lysozymes was established by immunological cross-reactivity.
Abomasum↗
Characterization of a thermosensitive protein from human milk whey.
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Amino Acids↗
Partial enzymatic hydrolysis of whey protein by trypsin.
Partial enzymatic hydrolysis of whey protein by trypsin increased solubility of this protein in water. Water-insoluble, heat-denaturated whey protein was solubilized fully by trypsinization. Optimal conditions for the enzyme reaction, established by the pH-stat technique, were: digestion at pH 8.0 and 55 C for approximately 3 h, at an enzyme-substrate ratio of 1 : 100. Under these conditions, 500 mumoles of titratable protons were liberated per g of substrate in the course of the reaction. Digestion at 40 C generated only about 400 mumoles of acid. Predenaturation of the substrate by heat did not improve digestibility. The extent of hydrolysis reached approximately 8% of all peptide bonds in the protein. Fractionation of the digest on Sephadex G-50 showed it was composed of a major fraction of highly water soluble peptides, ranging in molecular weight from approximately 500 to 5000. The gel excluded a minor fraction of larger, aggregated peptides. This aggregate was dissociated in the presence of urea and a reducing agent. All amino acids in the digest, except some lysine and arginine, were peptide bound.
Amino Acids↗
Milk formulae in the prevention of food allergy.
Because food allergy is frequent and severe, all possible means should be used to try to prevent its manifestations or at least to delay them until the child is older and stronger and therefore better able to follow an exclusion diet. The capacity of breast-feeding for preventing food allergy has been challenged in the past, but a consensus seems to be emerging now that breast-feeding can indeed prevent food allergy if it is started at birth and is exclusive for at least 4, and preferably 6, months. In the most "at-risk" babies the breast-feeding mother should try to eliminate the most potent allergens (eggs, fish, soya, nuts, and cow's milk) from her diet. If a substitute or a complement to breast milk is necessary, neither goat's milk nor soy milk formula are adequate. Heat treatment alone will not be sufficient to make cow's milk hypoallergenic. Only a combination of protein hydrolysis and managed heat treatment can make cow's milk hypoallergenic and retain its nutritional value. This nutritional value should be assessed by animal studies and also by studying infant growth. The hypoallergenicity of a formula can be studied in vitro and with animal tests, but only clinical trials on human infants will prove its efficacy.
Breast Feeding↗