Department of Microbiology, Vidyasagar University, Paschim Medinipur, India.
Division of Plant Biology, Bose Institute, Kolkata, India.
Sci Rep. 2020 Nov 19;10(1):20177. doi: 10.1038/s41598-020-77247-z.
Sunflower pollen was reported to contain respiratory allergens responsible for occupational allergy and pollinosis. The present study describes the comprehensive characterization of a major sunflower allergen Hel a 6. Natural Hel a 6 was purified from sunflower pollen by anion exchange and gel filtration chromatography. Hel a 6 reacted with IgE-antibodies from 57% of 39 sunflower-sensitized patient sera suggesting it to be a major allergen. The patients were of Indian origin and suffering from pollinosis and allergic rhinitis. Hel a 6 exhibited allergenic activity by stimulating mediator release from basophils. Monomeric Hel a 6 displayed pectate lyase activity. The effect of various physicochemical parameters such as temperature, pH, and calcium ion on the functional activity of Hel a 6 revealed a stable nature of the protein. Hel a 6 was folded, and its melting curve showed reversible denaturation in which it refolded back to its native conformation from a denatured state. Hel a 6 displayed a high degree of sequence conservation with the pectate lyase allergens from related taxonomic families such as Amb a 1 (67%) and Art v 6 (57%). The IgE-cross reactivity was observed between Hel a 6 and its ragweed and mugwort homologs. The cross-reactivity was further substantiated by the mediator release when Hel a 6-sensitized effector cells were cross-stimulated with Art v 6 and Amb a 1. Several putative B cell epitopes were predicted and mapped on these 3 allergens. Two antigenic regions were found to be commonly shared by these 3 allergens, which could be crucial for cross-reactivity. In conclusion, Hel a 6 serves as a candidate molecule for diagnosis and immunotherapy for weed allergy.
向日葵花粉被报道含有引起职业性过敏和花粉症的呼吸过敏原。本研究描述了一种主要的向日葵过敏原 Hel a 6 的全面表征。天然 Hel a 6 通过阴离子交换和凝胶过滤色谱从向日葵花粉中纯化而来。Hel a 6 与 39 名向日葵过敏患者血清中的 IgE 抗体反应，提示其为主要过敏原。这些患者来自印度，患有花粉症和过敏性鼻炎。Hel a 6 通过刺激嗜碱性粒细胞释放介质来表现出过敏活性。单体 Hel a 6 显示果胶裂解酶活性。各种物理化学参数（如温度、pH 值和钙离子）对 Hel a 6 功能活性的影响表明该蛋白性质稳定。Hel a 6 折叠，其熔化曲线显示出可逆变性，其中它从变性状态重新折叠回其天然构象。Hel a 6 与相关分类群的果胶裂解酶过敏原（如 Amb a 1（67%）和 Art v 6（57%））具有高度的序列保守性。在 Hel a 6 与其豚草和艾蒿同源物之间观察到 IgE 交叉反应性。当 Hel a 6 致敏效应细胞与 Art v 6 和 Amb a 1 交叉刺激时，观察到介质释放，进一步证实了这种交叉反应性。预测并映射了这 3 种过敏原上的几个潜在 B 细胞表位。发现这 3 种过敏原共有两个抗原区域，这可能对交叉反应性至关重要。总之，Hel a 6 可作为杂草过敏症诊断和免疫治疗的候选分子。
