家蚕胸腺素对蚕体抗核型多角体病毒感染能力的影响

Effect of Thymosin on Antiviral Ability of Silkworm Against Bombyx mori Nucleopolyhedrovirus

胸腺素（THY）在动物进化过程中高度保守,并在许多生命活动中发挥重要作用。将家蚕核型多角体病毒（Bm NPV）感染家蚕5龄幼虫后,分别提取蚕体及不同组织的RNA和蛋白质,检测Bm THY基因的转录及蛋白质表达的变化,并探究利用重组胸腺素r Bm THY增强家蚕抗病毒能力的可行性。qRT-PCR检测结果表明,感染Bm NPV后的家蚕5龄幼虫,其血淋巴、脂肪体、丝腺和气管中的Bm THY基因mRNA转录水平不同程度上调,而马氏管、中肠和头部组织中Bm THY基因mRNA转录水平则呈下调趋势;Western blotting检测家蚕5龄幼虫感染Bm NPV后72 h,蚕体内Bm THY蛋白的表达水平下降42.3%。家蚕5龄幼虫接种Bm NPV后,分别添食质量浓度为340μg/m L（高剂量）、34μg/m L（中剂量）和3.4μg/m L（低剂量）的r Bm THY溶液,调查3组幼虫的发病率为43.8%、54.0%和57.6%,而对照组幼虫分发病率为62.2%。研究结果初步证明Bm NPV感染可降低蚕体及部分组织中Bm THY的基因转录与蛋白质表达水平,高剂量r Bm THY添食处理可以在一定程度上提高家蚕抗Bm NPV病毒感染的能力。

Abstract Thymosin （THY） is highly conserved during animal evolution and plays an important role in many life activities. After being infected by Bombyx mori nuclopolyhedrovirus （BmNPV）, silkworm larvae of 5th instar were used to extract RNAs and proteins from various larval body and various tissues for measuring changes of BmTHY gene transcription and protein expres- sion, so as to explore the feasibility of using recombinant silkworm thymosin （rBmTHY） to enhance the antiviral ability of silk- worm. The results of qRT-PCR showed that BmTHY transcription in hemolymph, fat body, silk gland and trachea of the 5th in- star larvae infected with BmNPV was up-regulated in different degrees, while that in Malpighian tubule, midgut and head tissues was down-regulated. Western blotting showed that the expression of BmTHY in larval body decreased by 42. 3% at 72 h after BmNPV infection. After BmNPV inoculation, the 5th instar larvae were administered with rBmTHY solution at concentrationof 340 μg/mL （high dose）, 34 μg/mL （middle dose） and 3. 4 μg/mL （low dose ）. Disease incidence of the above three treatment groups was 43. 8%, 54. 0% and 57. 6% respectively, while that of the control group was 62. 2%. These results showed that BmNPV infection could reduce the transcription and protein expression of BmTHY in larval body and in certain larval tissues of silkworm, and high dose rBmTHY treatment could improve antiviral ability of silkworm larvae against BmNPV to certain extent.