昆虫刺蛰引起的过敏反应是医学上的一个重要的病症，除了导致红肿、瘙痒等症状外，全身性过敏反应的发生甚至可能导致病人死亡。刺蛰的昆虫主要是昆虫纲膜翅目的成员，包括胡蜂、黄蜂等。但也有部分昆虫包括牛虻、斑虻、猎蝽等，会导致过敏性反应。长期以来，世界多个实验室都对牛虻和胡蜂导致的过敏反应进行了研究，并提出了胡蜂牛虻过敏交叉反应综合症的存在，但一直没有找到直接的医学证据。

近期，中国科学院昆明动物研究所赖仞研究员领导的研究团队从牛虻唾液腺中分离和识别了两个天然的过敏原分子Tab a 1和Tab a 2，并收集了37例牛虻叮咬过敏病人的血清，和3例胡蜂过敏病人的血清，检测了这两个分子与病人血清IgE的结合情况。研究发现，Tab a 1和Tab a 2与病人血清IgE反应呈现出80-90％的阳性率，并且可以剂量依赖的方式竞争性抑制病人血清IgE与牛虻唾液腺总蛋白的结合。

这是世界上从牛虻唾液腺中首次鉴定出天然过敏原的首次报道，该研究结果为胡蜂牛虻过敏综合症提供了直接的证据，对昆虫刺蛰过敏性反应的诊断和治疗具有重要的意义。

原文出处：

Allergy DOI:10.1111/j.1398-9995.2010.02435.x

Purification and characterization of two new allergens from the salivary glands of the horsefly, Tabanusyao
D. Ma 1,2*, Y. Li 1,2*, J. Dong 3*, S. An 2,4 , Y. Wang 1,2 , C. Liu 1,2 , X. Yang 1,2 , H. Yang 1,2 , X. Xu 1 , D. Lin 3 & R. Lai 1

1 Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China ;   2 Graduate School of the Chinese Academy of Sciences, Beijing, China ;   3 School of Life Science and Technology, China Pharmaceutical University, Nanjing, China ;   4 School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China

Background: Horsefly bite can cause allergic reactions in humans. There is no information about allergenic horsefly proteins.

Objectives: The current work aims to purify and characterize IgE-binding proteins from horsefly salivary glands.

Methods: Two IgE-binding proteins, Tab a 1 and Tab a 2 with molecular weight of 26 and 35 kd, respectively, were purified and characterized from 60 000 pairs of horsefly salivary glands of Tabanus yao, respectively. Their primary sequences were determined by Edman degradation and cDNA cloning. Their allergenicity was examined using enzyme-linked immunosorbent assay (ELISA), ELISA inhibition tests, and immunoblots.

Results: Immunoblotting demonstrated IgE binding by 32 and 34 of 37 (86.5% and 91.8%) subjects' sera to Tab a 1 and Tab a 2, respectively. They were identified as an antigen 5-related (Ag 5) protein and hyaluronidase, respectively. ELISA inhibitions of serum IgE reactivity to the horsefly salivary gland extract (SGE) using purified Tab a 1 and Tab a 2 were significant (about 45%). In addition, these proteins showed some IgE-binding capacity to sera of subjects with wasp sting allergy.

Conclusions: We have first identified and characterized two IgE-binding proteins, Tab a 1, an Ag 5-like protein and Tab a 2, a hyaluronidase, from the horsefly salivary glands. They appear to be of importance for the allergic reactions induced by horsefly bite. These allergens are thus not only found in stinging but also found in hematophagous insects. These results also provided support for the presence of the so-called wasp-horsefly syndrome (WHS).