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

Abstract

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