Green Erica A, Fu Qiang, Ndhairo Nelson, Leibiger Thomas M, Wang Yongdan, Lee Yongsuk, Lee Kelvin H, Betenbaugh Michael, Yoon Seongkyu, McNally David J
Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware, USA.
Department of Biomedical Engineering and Biotechnology, University of Massachusetts Lowell, Lowell, Massachusetts, USA.
Biotechnol Bioeng. 2025 Apr 8. doi: 10.1002/bit.28980.
Recombinant adeno associated virus (rAAV) vectors have become popular delivery vehicles for in vivo gene therapies, but demand for rAAVs continues to outpace supply. Platform processes for rAAV production are being developed by many manufacturers, and transient chemical transfection of human embryonic kidney 293 (HEK293) cells is currently the most popular approach. However, the cutting edge nature of rAAV process development encourages manufacturers to keep cell culture media formulations, plasmid sequences, and other details proprietary, which creates hurdles for small companies and academic labs seeking to innovate in this space. To address this problem, we leveraged the resources of an academic-industry consortium (Advanced Mammalian Biomanufacturing Innovation Center, AMBIC) to develop an rAAV production system based on transient transfection of suspension HEK293 cells adapted to an in-house, chemically defined medium. We found that balancing iron and calcium levels in the medium were crucial for maintaining transfection efficiency and minimizing cell aggregation, respectively. A design of experiments approach was used to optimize the transient transfection process for batch rAAV production, and PEI:DNA ratio and cell density at transfection were the parameters with the strongest effects on vector genome (VG) titer. When the optimized transient process was transferred between two university sites, VG titers were within a twofold range. Analytical characterization showed that purified rAAV from the AMBIC process had comparable viral protein molecular weights versus vector derived from commercial processes, but differences in transducing unit (TU) titer were observed between vector preps. The developed media formulation, transient transfection process, and analytics for VG titer, capsid identity, and TU titer constitute a set of workflows that can be adopted by others to study fundamental problems that could improve product yield and quality in the nascent field of rAAV manufacturing.
重组腺相关病毒(rAAV)载体已成为体内基因治疗中常用的递送工具,但对rAAV的需求仍持续超过供应。许多制造商正在开发rAAV生产的平台工艺,目前最常用的方法是对人胚肾293(HEK293)细胞进行瞬时化学转染。然而,rAAV工艺开发的前沿性质促使制造商对细胞培养基配方、质粒序列和其他细节保密,这给寻求在该领域进行创新的小公司和学术实验室带来了障碍。为了解决这个问题,我们利用了一个产学联盟(先进哺乳动物生物制造创新中心,AMBIC)的资源,开发了一种基于悬浮HEK293细胞瞬时转染的rAAV生产系统,该细胞适应于一种内部的、化学成分明确的培养基。我们发现,平衡培养基中的铁和钙水平分别对于维持转染效率和最小化细胞聚集至关重要。采用实验设计方法优化了批量rAAV生产的瞬时转染过程,转染时的PEI:DNA比例和细胞密度是对载体基因组(VG)滴度影响最大的参数。当将优化后的瞬时工艺在两个大学地点之间转移时,VG滴度在两倍范围内。分析表征表明,从AMBIC工艺中纯化的rAAV与商业工艺获得的载体相比,病毒蛋白分子量相当,但不同载体制剂之间的转导单位(TU)滴度存在差异。所开发的培养基配方、瞬时转染工艺以及VG滴度、衣壳鉴定和TU滴度的分析方法构成了一套工作流程,可供其他人采用,以研究可能改善rAAV制造新兴领域产品产量和质量的基本问题。