Sensitisation of preruminant calves and piglets to antigenic protein in early weaning diets: control of the systemic antibody responses.

The immune response stimulated by dietary protein was studied in preruminant calves and piglets. Calves receiving dietary soya developed high serum titres of soya-specific IgG which did not decline with prolonged feeding. IgG1 and IgG2 subclasses showed a parallel rise although IgG1 predominated. Levels of antibody evoked by a combination of oral and parenteral sensitisation with soya protein were significantly greater than by parenteral sensitisation alone. These results suggest that the calves failed to develop oral tolerance. Passively acquired maternal soya-specific antibody did not influence the response to oral or parenteral sensitisation with soya. By contrast, piglets weaned onto a soya-containing diet became hyporesponsive to injection with soya protein. Thus, calves and piglets appear to differ in their ability to control adverse immune responses to dietary antigens. This could influence the severity of gastrointestinal disorders associated with early weaning diets.

[Mechanisms implicated in the intestinal allergic reaction to soya proteins in the preruminant calf]. / Mécanismes impliqués dans la réaction allergique intestinale aux protéines de soja chez le veau préruminant.

Studies of intestinal motility in calves given antigenic soya protein or sucrose showed disturbances linked to diarrhoea. Disorders arising from feeding antigenic soya protein were distinct from abnormal motility induced by indigestible carbohydrate. Suppression of the digestive disorders by a drug having anti-allergic properties implied the involvement of an immunological mechanism.

A comparison of the antigenicity of soya-bean-based infant formulas.

1. The antigenicity of four soya-bean-based infant formulas (Prosobee powder, Prosobee liquid concentrate (Mead Johnson, Uxbridge, Middx), Wysoy (Wyeth, Maidenhead, Berks) and Formula S (Cow and Gate, Trowbridge, Wilts] was measured by enzyme-linked immunosorbent assays (ELISAs) specific for glycinin and beta-conglycinin. Results were compared with in vivo assessments of antigenicity using guinea-pigs, rabbits and calves. 2. The levels of antigenic glycinin and beta-conglycinin in Wysoy and Formula S were below the limits of detection of the ELISA. Both these proteins were detected in Prosobee powder and Prosobee liquid concentrate with the highest levels, especially for glycinin, being present in Prosobee powder. 3. Wysoy was sufficiently antigenic to evoke a soya-bean-specific serum antibody response in rabbits injected with this formula emulsified in complete Freunds adjuvant. A significantly greater response was obtained when rabbits were similarly injected with Prosobee powder. 4. The formulas varied in their ability to sensitize guinea-pigs for both anaphylaxis and antibody production when given orally, although the differences were not statistically significant. Prosobee powder appeared to be the most antigenic and Formula S the least, with Prosobee liquid concentrate and Wysoy being intermediate. 5. Similar variations in antigenicity were observed when Prosobee powder, Wysoy and Formula S were fed to soya-bean-sensitive calves. These formulas were all capable of provoking intestinal disturbances (seen as increased ileal flow-rate, decreased small intestinal transit time and decreased nitrogen absorption) but the most severe reactions were seen when Prosobee powder was fed and the least with Formula S. 6. Thus the four soya-bean-based infant formulas showed considerable differences in antigenicity. In vivo studies using guinea-pigs, rabbits and calves were in good agreement and broadly correlated with the immunochemical assessment of antigenicity. However, the in vitro and in vivo results did not correspond exactly and levels of glycinin and beta-conglycinin below the limit of detection by ELISA could evoke an immune response in the different animal species. We believe that these variations in antigenicity of different commercial products prepared from isolated soya-bean protein may be important when interpreting the results from studies of the development of allergy in infants given soya-bean-based formulas.

Reduction in the antigenicity of whey proteins by heat treatment: a possible strategy for producing a hypoallergenic infant milk formula.

Residual antigenic protein in heat-denatured cow's milk whey and in two commercial infant milk formulas was determined using enzyme-linked immunosorbent assays specific for beta-lactoglobulin, alpha-lactalbumin, bovine serum albumin, bovine IgG1 and alpha-casein. This immunochemical assessment of antigenicity was related to the capacity of the preparations to sensitize immunologically when fed to guinea-pigs for 2 weeks. Antibody production was measured and the susceptibility of the animals to systemic anaphylaxis was assessed by injecting them intravenously with heated or unheated milk proteins. Whey protein that had been heated at 100 degrees or 115 degrees for 30 min was extensively denatured and, in contrast to pasteurized whey, failed to sensitize guinea-pigs for anaphylaxis. Antibody production was undetected or very low. The proteins in SMA powder and SMA Gold Cap liquid concentrate were less denatured and animals given these formulas prepared according to the maker's instructions produced relatively high levels of antibodies to beta-lactoglobulin and alpha-casein and a majority developed anaphylaxis when injected intravenously with these products. As well as failing to sensitize, whey that had received severe heat treatment did not, in most cases, elicit anaphylaxis when injected into animals that had been sensitized with unheated milk. Discrimination between antibodies of the IgG1 and IgG2 subclasses specific for beta-lactoglobulin showed that IgG1, the principal anaphylactic antibody in guinea-pigs, was preferentially depressed in animals drinking heat-denatured milk preparations. The results suggest that heat denaturation of whey protein may be a logical and simple strategy for producing a hypoallergenic baby milk. Nevertheless, the value of experiments in guinea-pigs for predicting results in man is uncertain and the proposal awaits assessment in clinical trials.

Effects of heat treatment of cow's milk and whey on the nutritional quality and antigenic properties.

Recent experiments in guinea-pigs suggest that heat treatment applied during the manufacture of baby milk formulae reduces the immunological sensitising capacity of the cow's milk proteins. This immunological benefit must be weighed against possible damage that heat treatment may cause to the nutritional quality of the products. Severe heat treatment of skimmed milk (121 degrees C for 20 min) destroyed all the vitamin B12, about 60% of the thiamin and vitamin B6, 70% of the ascorbic acid, and about 30% of the folate. Available lysine was reduced by 21% and lactulose was formed (166 mg/100 ml). Despite extensive denaturation of the whey proteins the milk retained its capacity to sensitize guinea-pigs for systemic anaphylaxis when administered orally. Animals drinking heated milk also produced circulating antibodies to beta-lactoglobulin and casein, although titres were lower than for unheated milk. Unlike skimmed milk, heat-treated diafiltered whey failed to sensitize guinea-pigs orally. It caused the production of trace levels of antibodies in some of the animals, but these were specific for residual casein. We suggest that it may be possible to produce a non-sensitising baby milk without casein based on heat-denatured whey. The nutritional quality could be preserved by removing low molecular weight nutrients before heat treatment and adding back appropriate quantities later.

Immune responses in guinea pigs to dietary protein. I. Induction of tolerance by feeding with ovalbumin.

Introduction of ovalbumin into the diet of guinea pigs initially evoked the production of circulating antibody. With continued feeding, antibody levels declined in animals fed with ovalbumin from 2-4 days or 6-8 weeks of age, but remained constant in guinea pigs commencing the feeding regimen at 5-6 months of age. All animals receiving dietary ovalbumin became hyporesponsive to parenteral injection with ovalbumin in adjuvant, and suppression of IgG1 and IgG2 antibody subclasses was observed. The results demonstrated that delayed hypersensitivity to ovalbumin was more readily suppressed by the feeding regimen than the systemic antibody response.