Skin test diagnosis of grass pollen allergy with a recombinant hybrid molecule.

BACKGROUND: A recombinant hybrid molecule (HM) consisting of 4 major allergens from timothy grass (Phl p 1, 2, 5, and 6) was expressed in Escherichia coli, purified, and characterized regarding its immunologic properties. OBJECTIVE: We sought to determine whether the recombinant HM can be used for the diagnosis of grass pollen allergy by means of skin testing. METHODS: Skin prick testing was performed in 32 patients with grass pollen allergy and in 9 control individuals by using increasing concentrations (4, 12, 36, and 108 mug/mL) of the HM and using commercial grass pollen extract. Specific IgE reactivities against the HM, grass pollen extract, and a panel of purified grass pollen allergens (recombinant Phl p 1, 2, 5, 6, 7, 12, and 13 and natural Phl p 4) were measured by means of ELISA, and timothy grass pollen-specific IgE levels were determined by using ImmunoCAP. RESULTS: Grass pollen allergy was diagnosed in all patients by means of skin testing with the HM. No false-positive skin test responses were obtained in the control individuals. There was an excellent correlation between IgE levels obtained with the HM and natural grass pollen extract measured by means of ELISA (r = 0.98, P < .0001) and by means of ImmunoCAP (r = 0.98, P < .0001). CONCLUSIONS: The recombinant HM permitted accurate and specific in vivo diagnosis of grass pollen allergy in all tested patients. It can be considered a well-defined tool for the diagnosis and perhaps for immunotherapy of grass pollen allergy. CLINICAL IMPLICATIONS: A recombinant HM can replace traditional allergen extracts for skin test-based diagnosis of grass pollen allergy.