The recombinant allergen-based concept of component-resolved diagnostics and immunotherapy (CRD and CRIT)

Current forms of allergy diagnosis and specific immunotherapy are performed with allergen extracts. Allergen extracts contain a variety of allergenic and nonallergenic components and their allergen content is often cumbersome to standardize. If used for diagnostic purposes, positive reactions to a given allergen extract will thus provide the information that an allergic subject is sensitized against extract components, but without identifying them. Likewise, extract-based immunotherapy cannot be adapted to the individual patient's sensitization pattern. Here we review progress in the field of molecular allergen characterization by recombinant DNA technology, leading to novel forms of component-resolved diagnostics (CRD) and immunotherapy (CRIT) based on recombinant allergens. Several studies have demonstrated advantages of recombinant allergen-based diagnosis. Using recombinant allergens in in vitro diagnostic devices, a patient's individual IgE reactivity profile can be quantitatively established. The presence of IgE to cross-reactive allergen components can thus be determined and used to predict clinically relevant sensitization to allergen sources which contain immunologically related allergens. Moreover it has been demonstrated that cocktails of recombinant allergens, matching the IgE epitope complexity present in natural allergen extracts, can be assembled. Component-resolved diagnosis will thus allow the precise selection of those molecules for specific immunotherapy to which a patient is actually sensitized. Recently, several recombinant hypoallergenic allergen derivatives have been developed for immunotherapy. The progress in allergen research achieved by the use of recombinant DNA technology holds promise that component-resolved diagnosis and immunotherapy may help refine the procedures of allergy diagnosis and immunotherapy in the coming decade and beyond.