Tick sucks large amount of host blood during its life cycle. Host IgG in blood can pass through tick midgut into haemolymph, and still retain its activity. To protect ticks from damage of host immune response, Immunoglobulin G binding proteins (IGBPs) in tick body can bind with host IgG, then IgG was excreted out. As key moleculars in ticks, IGBPs were regard as the anti-tick vaccine candidate. Rhipicephalus haemaphysaloides are dominant ticks in South China. RH-IGBP was found in its salivary gland, and identified as vaccine antigen. For more details about its bio-function, we constructed the recombinant Bacmid-IGBP, which was expressed successfully by Baculovirus Expression Vector Systems. Then, We detected the recombinant protein by indirect immunofluorescence ( IF A) and Western-blot, and found that its molecular weight was 23 kDa, agreed with what we predicted. We used the purified protein to bind with mammal animals (Rabbit, Pig, Dog, Goat, Mouse, Bovine) and Human IgG, and Rabbit IgG F (abr) 2 and Fc fragment with ELISA. The results suggested that RH-IGBP can bind with IgG from rabbit and pig obviously, and the main recognition site is IgG F (abr) 2 fragment. The results revealed the function mechanism of IGBP preliminarily.%蜱吸食宿主大量血液,其中宿主血液中IgG分子能穿过蜱肠道,进入血淋巴,且能保持其活性.为逃避宿主免疫攻击,蜱唾液腺分泌一种免疫球蛋白结合蛋白(Immunoglobulin G binding protein,IGBP),与蜱体内的宿主IgG结合,抑制宿主IgG对蜱的损害,是蜱唾液腺重要的功能分子,也是抗蜱疫苗候选分子.镰形扇头蜱是我国南方的优势蜱种,其唾液腺免疫球蛋白结合蛋白(RH-IGBP)被鉴定为抗蜱免疫保护性抗原,为进一步了解其生物学功能,本研究应用杆状病毒表达系统,构建出重组杆粒Bacmid-IGBP,并在昆虫细胞中表达出真核重组蛋白RH-IGBP,经免疫荧光实验鉴定和Western blot分析,重组蛋白大小为23kDa,与预期一致.重组蛋白经纯化,利用ELISA方法,研究重组蛋白与不同哺乳动物宿主(兔、猪、牛羊、鼠、犬)和人的IgG结合能力,发现RH-IGBP与不同宿主IgG结合能力不同,与兔、猪的IgG有明显结合能力.对来自兔源IgG不同酶切片段F(ab′)2 和Fc与RH-IGBP结合特性分析表明,蜱IgG结合蛋白主要识别部位是IgG的F(ab′)2片段.这些结果初步揭示了蜱IgG结合蛋白的作用机制和特点.
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