A viral lectin encoded in Cotesia plutellae bracovirus and its immunosuppressive effect on host hemocytes
A viral lectin encoded in Cotesia plutellae bracovirus and its immunosuppressive effect on host hemocytes
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DOI：
10.1016/j.cbpa.2008.01.007
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发表时间：
2008-04-01
影响因子：
2.3
通讯作者：
Kim, Yonggyun
中科院分区：
文献类型：
--
作者：
Lee, Sunyoung;Nalini, Madanagopal;Kim, Yonggyun
菜蛾绒茧蜂对小菜蛾的免疫抑制作用为了鉴定免疫抑制因子，将小菜蛾寄生的血淋巴分离成血浆和血细胞组分。当未寄生的血细胞覆盖寄生血浆，他们表现出显着降低细菌结合效力。在这里，我们考虑了一种以前在其他盘绒茧蜂属中发现的病毒凝集素，作为C.小菜蛾寄生根据病毒凝集素基因的保守区序列，从小菜蛾体内克隆了相应的凝集素基因。plutellae。其cDNA长674 bp，编码157个氨基酸，含有一个信号肽（15个残基）和一个糖识别结构域。在其基因组DNA中，开放阅读框被一个内含子（156 bp）分隔。氨基酸序列与C. ruficrus杆状病毒凝集素，属于C型凝集素。Southern杂交分析表明，克隆的凝集素基因位于C. plutellae bracovirus（CpBV）基因组。实时荧光定量RT-PCR和免疫印迹分析表明，CpBV-凝集素显示在寄生的早期表达。重组CpBV凝集素在细菌系统中得到表达，纯化的CpBV凝集素对细菌与非寄生小菜蛾血细胞的结合有明显的抑制作用。在小菜蛾寄生后24 h，CpBV-凝集素特异性免疫染色结果显示，CpBV-凝集素存在于小菜蛾寄生卵表面。24 h龄的卵在体外不被小菜蛾血细胞包裹，相比之下，新产的寄生蜂卵显示没有可检测到的CpBV-凝集素并且容易被包裹。这些结果支持存在一个多脱氧核糖核酸病毒凝集素家族Cotesia相关的杆状病毒，并提出其免疫抑制功能。(C)2008年爱思唯尔公司All rights reserved.
An endoparasitoid wasp, Cotesia plutellae, induces immunosuppression of the host diamondback moth, Plutella Xylostella. To identify an immunosuppressive factor, the parasitized hemolymph of P. xylostella was separated into plasma and hemocyte fractions. When nonparasitized hemocytes were overlaid with parasitized plasma, they showed significant reduction in bacterial binding efficacy. Here, we considered a viral lectin previously known in other Cotesia species as a humoral immunosuppressive candidate in C. plutellae parasitization. Based on consensus regions of the viral lectins, the corresponding lectin gene was cloned from P. xylostella parasitized by C. plutellae. Its cDNA is 674 bp long and encodes 157 amino acid residues containing a signal peptide (15 residues) and one carbohydrate recognition domain. Open reading frame is divided by one intron (156 bp) in its genomic DNA. Amino acid sequence shares 80% homology with that of C. ruficrus bracovirus lectin and is classified into C-type lectin. Southern hybridization analysis indicated that the cloned lectin gene was located at C. plutellae bracovirus (CpBV) genome. Both real-time quantitative RT-PCR and immunoblotting assays indicated that CpBV-lectin showed early expression during the parasitization. A recombinant CpBV-lectin was expressed in a bacterial system and the purified protein significantly inhibited the association between bacteria and hemocytes of nonparasitized P. xylostella. In the parasitized P. xylostella, CpBV-lectin was detected on the surface of parasitoid eggs after 24 h parasitization by its specific immunostaining. The 24 h old eggs were not encapsulated in vitro by hemocytes of P. xylostella, compared to newly laid parasitoid eggs showing no CpBV-lectin detectable and easily encapsulated. These results support an existence of a polydnaviral lectin family among Cotesia-associated bracovirus and propose its immunosuppressive function. (C) 2008 Elsevier Inc. All rights reserved.