新型重组AAV5/5载体及包装系统

A novel packaging system of recombinant AAV5/5 vector

摘要:

本研究组建了一种可用于规模化生产的以重组单纯疱疹病毒为辅助病毒的AAV5/5载体包装系统。首先，将5型腺相关病毒 (AAV5) 的rep和cap基因插入I型单纯疱疹病毒 (HSV-1) 基因组非必需基因UL2中，获得重组病毒rHSV1-rep5cap5。其次，构建一种携带AAV5 ITR的通用型载体质粒pAAV5neo，将报告基因EGFP插入pAAV5neo中，得到pAAV5neo-EGFP质粒。将pAAV5neo-EGFP质粒导入BHK-21细胞，用G418选择培养，挑选出表达EGFP并在重组病毒rHSV1-rep5cap5感染下能高效产生rAAV5/5-EGFP的单克隆载体细胞株C020。用rHSV1-rep5cap5感染C020细胞制备rAAV5/5-EGFP，用“氯仿处理-聚乙二醇/氯化钠-氯仿抽提”方法粗纯化rAAV5/5-EGFP。用100 kDa分子量截流超滤方法进一步纯化和浓缩，获得高纯度的rAAV5-EGFP。SDS-PAGE电泳分析可见3条特征性外壳蛋白带。电镜分析显示病毒颗粒以实心颗粒为主。用rAAV5/5-EGFP病毒按1×105 vg/cell感染体外培养的HEK293细胞，可见30％细胞呈现绿色荧光。本研究提出了一种高效AAV5/5载体生产系统和纯化方法，为重组AAV5载体的进一步应用提供了基础。

Abstract:

We developed a scalable AAV5/5 vector packaging system by using replication competent recombinant herpes simplex type 1 virus as helper virus. The fragment containing rep and cap genes of AAV5 was inserted into the non-necessary gene (UL2) of HSV1 genome, resulting in the helper virus rHSV1-rep5cap5. An AAV5/5 vector pAAV5neo carrying two AAV5 ITRs was constructed by inserting a neo gene expression cassette into the plasmid backbone of pAV5CMV-GFP. pAAV5neo-EGFP was constructed by inserting EGFP gene into pAAV5neo. BHK21 cell was transfected with pAAV5neo-EGFP and cultured in the presence of G418. EGFP expression positive monoclonal cells were picked up, and one that produced rAAV5/5-EGFP with the highest efficiency under the help of rHSV1-rep5cap5 was chosen as the production cell line named as C020. rAAV5/5-EGFP was produced by infecting C020 cells with rHSV1-rep5cap5, and crudely purified by our previous method of ‘chloroform treatment- PEG8000/NaCl precipitation- chloroform extract’. rAAV5/5-EGFP preparation with high purity was obtained by ultrafiltration with molecular weight cut-off value of 100 kDa. SDS-PAGE stained with Coomassie brilliant blue R250 showed clearly specific pattern of three bands of AAV capsid proteins. rAAV5/5-EGFP was also assayed using negative stain transmission electron microscopy and the majority of the virus particles were found solid. About 30% green fluorescent cells could be seen after infecting HEK293 cells with rAAV5/5-EGFP 24 h at 1×105 vg/cell. In conclusion, we have established an efficient AAV5/5 vector production system and could produce recombinant AAV5/5 virus in large amounts for gene therapy research.