Evaluation of the allergenic relationship between Humulus japonicus and Humulus lupulus pollen allergens

Abstract

Purpose: Humulus japonicus pollen (Hop J) is a major cause of inhalant allergy in autumn of the Far East countries, and its allergenic potency has been increasing with climate changes. Allergen immunotherapy has been considered in Hop J-sensitized allergic patients: however, Hop J allergen extracts for immunotherapy are not commercially available. We speculate that Humulus lupulus pollen (Hop L) belonged to the same genus may share cross-reacting allergens with Hop J and evaluated allergenic relationships between these 2 pollens. Methods: Thirteen patients with allergic rhinitis and/or asthma sensitive to Hop J pollens were enrolled in Ajou University Hospital, Suwon, Korea. Hop J pollens were collected locally and lyophilized extracts were prepared, while lyophilized Hop L extracts were provided by Lofarma S.p.A. IgE-ELISA/enzyme-linked immunosorbent assay (ELISA) inhibition tests, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and IgE-immunoblot/immunoblot inhibition analysis using sera from the enrolled subjects were performed. Results: All patients had high serum specific IgE to both Hop J and Hop L extracts by ELISA, but no significant correlation was found between these 2 extracts. ELISA inhibition tests showed significant dose-dependent inhibitions on IgE-bindings to Hop L with serial additions of Hop J extracts in a dose-dependent manner, while minimal inhibitions of IgE binding to Hop J were noted with additions of Hop L. IgE-immunoblot analysis demonstrated that the major allergenic component of Hop J at 12 kDa was inhibited by Hop J, while no inhibitions were noted by Hop L extracts on IgE-immunoblot inhibition analysis. Conclusion: These findings suggest that there may not be a significant cross-allergenicity between Hop J and Hop L.