Component-resolved diagnosis (CRD) of type I allergy with recombinant grass and tree pollen allergens by skin testing

The diagnosis of Type I allergy is based on the measurement of allergen-specific IgE antibodies and on provocation with allergens, most frequently conducted by skin testing. Both forms of diagnosis are currently performed with allergen extracts that are difficult to standardize regarding their allergen contents, and which contain additional undefined nonallergenic components. We report the expression in Escherichia coli and purification of some of the most relevant timothy grass- and birch pollen allergens. Recombinant timothy grass- (rPhl p 1, rPhl p 2, rPhl p 5) and birch pollen (rBet v 1, rBet v 2) allergens were purified and used for the measurement of allergen-specific IgE and IgG subclass responses as well as for skin prick testing in 55 pollen allergic patients and 10 nonatopic individuals. Results obtained showed that the recombinant allergens allowed in vivo allergy diagnosis in 52 of 54 of the grass pollen and in 35 of 36 of the birch pollen allergic patients. Positive skin reactions were observed almost exclusively in patients containing detectable allergen-specific IgE antibodies but not in the nonatopic group; however, sensitivity to a given allergen as measured by skin reactivity was weakly correlated with the levels of allergen-specific IgE. Our results demonstrate that recombinant allergens can be used for component-resolved skin test diagnosis (CRD) of the patients' allergen sensitization profile, whereas allergen extracts at best allow to identify allergen-containing sources. CRD may thus represent the basis for novel forms of patient-tailored immunotherapy.