Identification of probable pectinesterase as a major allergen of pollen of the Asian white birch (Betula platyphylla) in northern China.

Background: Pollen of the Asian white birch (Betula platyphylla) is a major source of allergens in spring in northern China, yet little research on its pollen allergens has been done so far.

Objective: To analyze the B. platyphylla pollen allergen profile of patients from northern China and to identify the major pollen allergens in this patient cohort.

Methods: Sera from 35 Chinese patients with birch pollinosis were collected for this study. The IgE-binding proteins in B. platyphylla pollen extract were analyzed by IgE immunoblots. A novel major allergen was purified by cation exchange chromatography and affinity chromatography. Its IgE reactivity was evaluated by ELISA. The protein was excised from a 2D electrophoresis gel and subjected to ESI-QUAD-TOF.

Results: In our study cohort, the prevalence of IgE specific for Bet v 1 was 68.8% (n = 22/32) as measured by ImmunoCAP. In immunoblots, two major bands at around 17 kDa and 70 kDa were detected by IgE from 68.5% (24/35) and 65.7% (23/35) of sera, respectively. The 17 kDa band was identified as Bet v 1 by a monoclonal antibody to Bet v 1 and inhibition experiments with recombinant Bet v 1. The 70 kDa band was a polymorphic glycoprotein and 7 isoforms were found. The protein was identified as probably pectinesterase with a molecular weight of 66 kDa and a PI of 5.7.

Conclusions: A 66 kDa protein, probably belonging to pectinesterase family, was identified as a novel major allergen of B. platyphylla pollen in patients from northern China.