Immunoglobulin E reactivity and allergenic potency of Morus papyrifera (paper mulberry) Pollen

Background: Paper mulberry (Morus papyrifera) pollen is considered to be one of the most clinically relevant aeroallergens in Pakistan. To date, the allergenicity of the pollen has not been investigated. Objective: To characterize the sensitization profi le of mulberry-allergic patients and the proteins of paper mulberry pollen contributing to pollinosis in the Pakistani population. Methods: Proteins were extracted from mulberry pollen using different protocols. Immunoglobulin (Ig) E binding proteins to mulberry pollen was determined by ImmunoCAP testing and immunoblotting using sera from 29 mulberry pollen-allergic patients with positive skin prick test results to mulberry pollen antigens. The histamine release assay was performed in vitro to determine the allergenic potency of pollen extracts and a partially purifi ed mulberry pollen allergen. The protein was identifi ed using N-terminal sequencing and matrix-assisted laser desorption/ionization-time of fl ight spectrometry (MALDI-TOF/TOF). Results: IgE sensitization to mulberry pollen was confi rmed by positive ImmunoCAP results to pollen from Morus alba (white mulberry) in 23 out of 29 mulberry pollen-allergic patients. A 10-kDa protein from the paper mulberry pollen extract was considered a major allergen, along with additional IgE-reactive proteins. Sera from 79% of the patients reacted to the 10-kDa allergen, which showed substantial capacity to trigger histamine release in 3 out of 4 patients. N-terminal sequencing and MALDI-TOF/TOF yielded an amino acid sequence with no homology to known proteins. Conclusions: Mulberry-allergic patients are sensitized to multiple mulberry pollen allergens. We identifi ed a novel 10-kDa protein that was a major allergen and should be further investigated for diagnostic and therapeutic purposes.