Effect of heat denaturation on beta-lactoglobulin-induced gastrointestinal sensitization in rats: Denatured βLG induces a more intensive local immunologic response than native βLG

Abstract

Beta-lactoglobulin (betaLG) is one of the first foreign antigens encountered by a newborn child, and it is the major allergen causing cow's milk allergy. Heat denaturation causes changes to the protein structure, but the significance of heat-induced changes for immunogenicity or allergenicity is not known. To clarify how heat denaturation affects allergenicity and immunogenicity, we immunized Hooded-Lister rat pups with intra-peritoneal injections of native or heat-denatured betaLG at days 43 and 62 after birth. The animals were then fed native and denatured milk products twice weekly from 73 to 101 days of age with a feeding tube, after which they were allowed cheese and milk ad libitum, until they were killed on day 131. Total immunoglobulin (Ig)E and betaLG-specific IgG1 and IgG2a levels were determined from serum samples. Spontaneous interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) production was measured from duodenal specimens, and specimens of gastrointestinal mucosae were studied for the presence of inflammatory cells. The rats immunized with native betaLG had higher levels of total serum IgE than the unimmunized controls or the rats immunized with heat-denatured betaLG, while heat-denatured betaLG induced a significantly more intensive mononuclear inflammatory cell and eosinophil infiltration in the gastroduodenal mucosa. The betaLG-specific IgG antibody and IL-4 and IFN-gamma responses were similar in the two groups of immunized animals. Hence, denaturation modifies the immunogenic and allergenic properties of betaLG. Heat-denatured betaLG induces a more intensive local reaction in the gastrointestinal mucosa, while there is some evidence for enhanced systemic allergic sensitization by native betaLG.

Antigenic response of bovine β-lactoglobulin influenced by ultra-high pressure treatment and temperature

“…Enhanced particle formation may be responsible for the decline in antigenity of sweet whey (>50°C at 600 MPa for 10 min) and skim milk (>25°C). In addition, in analogy to heat treatment (Davis & Williams, 1998;Fritsché, 2003;Kleber et al, 2004;Rytkönen et al, 2002) modification of epitopes by the Maillard reaction at elevated temperature during pressure treatment may lead to destruction of linear epitopes with the consequence of a reduced antigenic response.…”

“…Another method to modify the antigenic response is the application of thermal treatment (Davis & Williams, 1998;Ehn, van Beresteijn, Robben, & Schmidt, 2004;Fritsché, 2003;Hóst & Samuelsen, 1988;Kilshaw, Heppell, & Ford, 1982;Kleber, Krause, Illgner, & Hinrichs, 2004;Mc Laughlan, Anderson, Widdowson, & Coombs, 1981;Ratner, Dworetzky, Oguri, & Aschheim, 1958;Rytkönen et al, 2002). Thermally treated β-lg showed a remarkable increase in antigenity when heated up to 90°C, which is due to the unfolding and the exposure of formerly hidden epitopes.…”

“…Above 90°C, the antigenic response decreased, owing to the loss of the conformational epitopes and to the masking of the sequential epitopes in the course of the aggregation and the thermally induced protein modification, e.g. the formation of glycosides in Maillard reaction (Davis & Williams, 1998;Fritsché, 2003;Rytkönen et al, 2002).…”

Decrease in the Allergenicity of Japanese Cedar Pollen Allergen by Treatment with Positive and Negative Cluster Ions

“…Based on this evidence, we anticipated that ion treatment might be capable of lowering practical allergen levels to less than the threshold values eliciting allergic symptoms or sensitizations, because subtractive downmodulation of IgE-binding activity of ion-treated allergens would be dominant among three possibilities of their biochemical alterations, i.e. (1) inactivation or destruction of epitope structures, (2) formation of new epitopes, or (3) improved access of previously hidden epitopes [36,37,38,39,40]. …”

Processing Foods Free from Dairy Proteins

“…In contrast to these fi ndings, Kleber et al [79] reported that heat -induced denaturation (90 ° C) increased the allergenicity of β -Lg, by exposing formerly hidden antigenic sites. They further reported that heating above 90 ° C decreased the antigenic response of β -Lg, owing to the loss of the conformational epitopes and to the masking of the sequential epitopes in the course of aggregation and thermally induced protein modifi cation (e.g., the formation of glycosides by Maillard reaction) [80,81] . The results are, therefore, quite confl icting but may be explained by the extent of aggregation or unfolding of the proteins upon heat treatment.…”