tva受体基因插入/缺失突变致宿主抗A亚群禽白血病病毒感染的机制研究

Avian leukosis subgroup A is an immunosuppressive neoplastic infectious disease caused by avian leukosis viruses subgroup A (ALV-A), which causes tremendous economic losses in the poultry industry. Studies have indicated that genetic mutations of the tva receptor gene cause host genetic resistance to infection by ALV-A in recent years. In our previous studies, two genetic mutations with GCCC insertion and ACCTCC deletion within the exon 1 of tva receptor gene were found in Chinese local chickens, respectively. However, whether these two genetic mutations confer the host resistance to infection by ALV-A, as well as its mechanism, are not clear. To illuminate the mechanism of the host genetic resistance to infection by ALV-A resulted from the insertion/deletion mutations within tva receptor gene, our project is to investigate the effect of insertion/deletion mutation in tva receptor gene on the expression of Tva receptor protein and the binding affinity between ALV-A envelope glycoprotein and Tva receptor protein, and further to verify whether host genetic resistance to infection by ALV-A was caused by insertion/deletion mutation in tva receptor gene in vitro and in vivo. The results of this project will confer an important theoretical and practical significance on the prevention and resistance breeding for avian leukosis subgroup A.

A亚群禽白血病是由ALV-A引起的一种免疫抑制性肿瘤性传染病，给养禽业造成重大的经济损失。近年来有研究表明，tva受体基因的遗传突变引起宿主对ALV-A的感染产生遗传抗性。我们前期研究发现：地方鸡种tva基因外显子1第304-305碱基位置发生GCCC插入突变和第318-323碱基位置发生ACCTCC缺失突变，但其是否致宿主抗ALV-A的感染及作用机制尚不清楚。基于这些研究基础，本项目将深入研究tva基因插入/缺失突变对Tva受体蛋白表达的影响机制，探讨tva基因插入/缺失突变对ALV-A囊膜蛋白与Tva受体蛋白亲合力的影响，并在体外、体内验证tva基因插入/缺失突变是否致宿主抗ALV-A的感染，从分子水平上阐明tva基因插入/缺失突变致宿主抗ALV-A感染的作用机制。本项目的研究结果对A亚群禽白血病的防控和抗病育种有重要的理论和实践意义。

本项目深入研究了tva受体基因插入（tva304-305insGCCC，tvar8）和缺失（tva318-323delACCTCC，tvar9）突变致宿主抗A亚群禽白血病病毒（ALV-A）感染的作用机制。（1）研究了tva受体基因插入/缺失突变对ALV-A囊膜蛋白与宿主受体蛋白亲合力的影响，发现tva304-305insGCCC突变导致ALV-A囊膜蛋白SUA与Tvar8受体蛋白的亲合力缺失，tva318-323delACCTCC突变降低了SUA与Tvar9受体蛋白的亲合力；（2）研究了tva受体基因插入/缺失突变对宿主体外感染ALV-A的影响，发现tva304-305insGCCC突变致使宿主细胞对ALV-A报告病毒RCASBP(A)-EGFP和ALV-A野毒的感染产生完全抗性，tva318-323delACCTCC突变致使宿主细胞对RCASBP(A)-EGFP病毒和ALV-A野毒的易感性降低而产生遗传抗性，并明确了tva304-305insGCCC和tva318-323delACCTCC突变为导致宿主细胞抗ALV-A感染的致因突变。（3）研究了tva受体基因插入/缺失突变对宿主体内感染ALV-A的影响，ALV-A体内攻毒试验结果表明tva304-305insGCCC和tva318-323delACCTCC突变导致宿主抗ALV-A的感染。研究成果很好地阐明了tva304-305insGCCC、tva318-323delACCTCC突变致宿主抗ALV-A的作用机制。此外，发现中国鸡种tvb受体基因存在两种插入突变：tvb cDNA序列第291-292碱基之间插入AG (c.291_292insAG，tvbr4)，第359-360碱基之间插入A (c.359_360insA，tvbr5)，研究发现tvbr4和tvbr5突变均引起tvb基因移码突变，导致tvb基因发生提前终止编码子从而表达截断的Tvb受体蛋白，显著降低了Tvb受体与ALV-B/D/E囊膜蛋白的亲和力，致使宿主对ALV-B/D/E的感染产生遗传抗性。相关研究成果在Journal of Virology和Oncotarget等国际知名期刊发表SCI论文2篇；申请国家发明专利5件，已获得授权专利2件；培育硕士研究生2人。本项目研究成果可为实现禽白血病抗病育种以控制禽白血病提供理论依据和技术支撑。