Investigation of the Allergenicity of β-Lactoglobulin and Its Cleavage Fragments

Abstract

Fragments of β-lactoglobulin were produced by proteolytic cleavage with trypsin, and chemical cleavage with cyanogen bromide, followed by gel filtration on Sephadex G-50. The antigenicity and allergenicity of the products were studied, before and after reductive cleavage by treatment with 2-mercaptoethanol. The former was determined by inhibition ELISA using IgG anti-β-lactoglobulin raised in rabbits, whilst the latter was determined by inhibition ELISA and mast cell challenge, using respectively the sera and peritoneal cells of rats experimentally sensitised to β-lactoglobulin. The findings raise interesting points about the structural basis of allergenicity in relation to antigenicity.

Permeability of milk protein antigens across the intestinal epithelium in vitro

“…In every case (3-Lg, antigens appeared to be the most resistant to degradation and the best able to cross the intestinal mucosa. These observations coincide with the idea that P-Lg is the main factor responsible for milk protein sensitization via the oral route (Huang et al, 1985;Koritz et al, 1987). Further studies are required to determine the mechanism that controls this intestinal permeability to food protein antigens.…”

“…For this reason, it is important to know the proportion of antigenic protein that remains present during digestion by gastrointestinal enzymes and during their intestinal transepithelial passage. For a study of this kind, milk protein antigens appeared to be a good model since they are known to induce anaphylactic sensitization in some subjects (Baird et aL, 1987;Changin ef al., 1981;Huang et al, 1985;Pearson et al, 1983; and are easily available in a pure form (Mercier et aL, 1968).…”

Microwave-assisted digestion of β-lactoglobulin by pronase, α-chymotrypsin and pepsin

“…This protein seems to be resistant to gastric digestion and apparently remains intact after passing through the stomach (Yvon, Van Hille, Pelissier, Guilloteau, & Toullec, 1984), and thus its aminoacid components may be nutritionally unavailable for infants. The b-Lg is considered also to be one of the main allergens in bovine milk (Huang, Coleman, & Stanworth, 1985;Otani, 1987;Okamoto, Hayashi, Enomoto, Kaminogawa, & Yamauchi, 1991;Se´lo, Negroni, Creminon, Yvon, Peltre, & Wal, 1998).…”

Processing Foods Free from Dairy Proteins

“…Immunoreactivity of native and denaturated β -Lg has also been studied, and the results showed that cleavage of the intrachain disulfi de bonds within the β -Lg molecule and consequently the loss of the conformation of the molecule had little or no effect on its immunoreactivity, suggesting that linear epitopes are mainly implicated [76,77] . Treatment of the protein at 90 ° C for 15 minutes, on the other hand, signifi cantly reduced IgE -binding capacity.…”