Quantification and Standardization of Allergens

This chapter talks about natural or recombinant proteins or glycoproteins used in the diagnosis and/or treatment of immunoglobulin E (IgE)-mediated allergic disease. The purpose of allergen standardization is to ensure that the extracts are well characterized in terms of allergen content and that variation between lots is minimized even among different manufacturers. In the United States, the use of a biological model of allergen standardization has permitted the assignment of bioequivalent allergen units (BAU) for most standardized allergens. Although skin testing is an essential component of the allergen standardization program, it is not intended for routine use in the testing of manufactured lots of extracts prior to release. For the Hymenoptera venom allergens, the potency determination is also based on the content of the known principal allergens within the extract, hyaluronidase and phospholipase, which is determined by enzyme activity. Individual allergens may be measured and detected by various approaches using monospecific antisera or antibodies. Assay designs using these antisera include the radial immunodiffusion (RID) assay, crossed immunoelectrophoresis/ crossed radioimmunoelectrophoresis (CIE/CRIE), and enzyme-linked immunosorbent assay (ELISA) variants (direct, two-site, and competition). Each of the assays utilizes monospecific antisera or antibodies to detect and quantify the specified allergen. The identity of an allergen extract may be verified by visualizing the separated allergen proteins on the basis of their size and isoelectric points.