Reactivities of immunoglobulin E and immunoglobulin G subclasses identified by isoelectric focusing-immunoprint in allergic patients

Immunological identification and characterization of individual food allergens

Food allergies of type-I-allergy are immunoglobulin E (IgE) mediated and caused by certain proteins or glycoproteins, which are called food allergens. An analytical marker of allergens is the IgE-reactivity to these substances. Normally food allergens are minor components in allergenic source material, which consist of a huge number of chemical different substances. Thus allergen extraction, separation and immunological detection methods are described which identify and characterize individual food allergens by a minimum of manipulation. Favoured separation methods of allergenic extracts are electrophoretic ones allowing the combination of highly resolved protein separations with immunological detection methods subsumed by the term immunoblotting. These techniques are a useful basis to characterize allergens by chemical methods. Once the primary protein structure of a food allergen is established, the way is cleared for the identification of epitopes. Epitopes are immunological detectable parts of a protein or glycoprotein generating the interface between chemical structure and immune-system. The nature of epitopes may differ, for instance, can be conformational, continuous, or built up by glycoconjugates, which determine the stability of food allergens, especially in the case of food processing. Progress in identification and characterization of food allergens will improve diagnostics and therapy of food allergy.

[Food allergy: identifying and characterizing peanut allergens with patient sera and monoclonal antibodies]

The purpose of this study is to improve the diagnosis of peanut allergy. In order to standardize test substances for in vivo and in vitro diagnostic, the type I allergy-associated single components of peanuts have been identified and characterized with the aid of patients' sera and monoclonal antibodies. For allergen detection IEF-immunoprint-, SDS-PAGE-immunoblot- and 2-D electrophoresis-techniques have been used. A comparison of control sera and patients' sera showed that both contained peanut specific IgG-, IgA- and IgM-antibodies. In contrast, peanut-specific IgE-antibodies were only detectable with patients' sera. In IEF-immunoprint the most intensive IgE-bindings showed up in pl-range from pH 5.5 to 7.5. In SDS-PAGE-immunoblot major allergens could be identified at molecular weight ranges of 17, 30, 48 to 66 and 116 kD. Raising monoclonal antibodies against IgE-reactive components from peanut extract resulted in eight antibody-producing hybridoma cell lines, named PN-a to PN-h. ELISA-inhibition tests revealed common epitopes of monoclonal antibodies and patients' antibodies. Moreover, the monoclonal antibodies were tested to see whether they can be used for detection of hidden peanut allergens.

Epitope analysis of the allergen ovalbumin (Gal d II) with monoclonal antibodies and patients' IgE

Ovalbumin (OVA) is a major allergen (Gal d II) of hen egg white and is often the cause of hypersensitivity reactions to food. Further knowledge of the antigenic and allergenic epitopes of allergens will provide better treatment of this disease. To analyse these epitopes we produced a panel of monoclonal antibodies (mAbs) against native OVA. The initial information about the epitopes was obtained with the binding patterns of these mAbs in IEF-immunoprints and western blots of OVA under reducing and non-reducing conditions. It was possible to demonstrate that the different conformations of OVA exhibit different epitopes, and that there are other epitopes which are shared by each conformation. Seven different, although sometimes overlapping epitopes, could be determined on native OVA; four different epitopes on denaturated non-reduced OVA by means of immunoblots of the intact molecule. The number of epitopes which could be differentiated by the mAbs was increased by the use of peptide blots after CNBr fragmentation of the molecule. IgE binding to different OVA conformations and to CNBr-fragments of OVA was also detectable and appears in the same regions as the reactivity of some mAbs. Western blots of OVA and CNBr-peptides demonstrate that some antigenic/allergenic binding sites seem at least partly to be continuous epitopes. The identification of the CNBr-fragments was performed by a microsequence analysis of blotted CNBr-fragments after a 2-dimensional electrophoresis. IgE was found to bind the two largest CNBr-fragments (residues 41-172 and 301-385), but not the fragment corresponding to residues 173-196. A number of monoclonal antibodies also reacted with the two large fragments, especially with fragment 301-385, and some bind also to shorter peptides, such as fragment 173-196, which were not reactive to patients' IgE. Most of the monoclonal antibodies and patients' IgE bind to the fragments 41-172 and 301-385 in 2D-PAGE blots suggesting that these fragments are involved in an immunogenic structure.