Evidence of Hop Japanese pollinosis in Korea: IgE sensitization and identification of allergenic components

Abstract

Background: Hop Japanese (Hop J) pollens are abundant in the air of Korea during the autumn season. Their significance as a source of allergic sensitization is still unclear.

Objectives: We sought to detect the sensitization rate to Hop J pollen as an inhalant allergen and to identify its allergenic components.

Method: We carried out skin prick tests with Hop J pollen extract in 1287 patients with respiratory allergy who visited our hospital over the course of 1 year. The serum-specific IgE antibody to Hop J pollen antigen was detected by ELISA, and its binding specificity was confirmed by the ELISA inhibition test. To confirm the respiratory sensitization, bronchoprovocation tests were performed in 16 asthmatic patients sensitive to this pollen. To characterize allergenic components, Hop J pollen extract was analyzed by means of sodium dodecylsulfate-polyacrylamide gel electrophoresis followed by IgE immunoblotting.

Results: A positive result on the skin prick test (> or = 2+ of the antigen to histamine ratio) was noted in 79 (6.1%) patients. The serum-specific IgE antibody was detected in 18 (41.9%) patients among 43 positive reactors tested. The ELISA inhibition test with the addition of Hop J pollen extract showed a dose-dependent response. Minimal inhibitions were noted with addition of ragweed and mugwort pollen extracts. Nine asthmatic patients showed significant bronchoconstriction after inhalation of the Hop J pollen extract (five early and four dual asthmatic responders), and all of them had high specific IgE binding. Immunoblot analysis revealed 12 IgE-binding components ranging from 13 to 89 kd. Three bands (13 kd, 74 kd, and 80 kd) were bound to the IgE among the sera tested from more than 50% of the patients.

Conclusion: We believe that the Hop J pollen should be considered as a relevant allergen during the autumn season and thus included in skin test batteries in Korea. Some patients diagnosed as having "intrinsic" asthma or rhinitis might be sensitized to this pollen and other previously unknown allergens.