We were thrilled to host Dr. Andrea Rayat for our recent CTGCT Science Talks webinar. Dr. Rayat, an Associate Professor in bioseparations and downstream processing at University College London, delivered an insightful presentation titled, “Making Viral Vectors Happy for Enhanced Functional Vector Recovery During Bioprocessing”. Her talk explored the critical challenges in downstream processing and offered fundamental strategies for improving yields in cell and gene therapy manufacturing.
Dr. Rayat framed her approach around what she calls the “VIPs of bioprocessing”. This helpful mnemonic encourages engineers to consider every element impacting the process:
- Product Variants (e.g., functional vs. non-functional vectors)
- Process Impurities
- The Product
- The Process itself (noting that some steps are necessary for process requirements, not just purification)
A key theme of the presentation was the importance of developing robust scale-down models. Dr. Rayat’s group at UCL specializes in “ultra scale-down” methodologies, which allow them to predict large-scale manufacturing performance using only millilitres of material. This approach is vital because, as she noted, bench-scale and large-scale manufacturing environments behave differently, especially regarding factors like pumps and fluid dynamics.
The presentation honed in on Tangential Flow Filtration (TFF), which Dr. Rayat identified as the “workhorse” of lentiviral vector (LV) processing. While antibody manufacturing relies heavily on chromatography, LV processing uses membrane filters in nearly every step. This makes understanding and optimizing TFF operations, like volume reduction (ultrafiltration, or UF) and buffer exchange (diafiltration, or DF), essential for improving overall recovery.
Dr. Rayat’s talk challenged a common industry assumption: that lentiviral vectors are highly sensitive to shear. She shared research from her group demonstrating that LVs are far more robust than often believed. Even when exposed to very high shear rates, the functional titre of the vectors remained stable. This finding suggests that poor recovery is often incorrectly blamed on shear when the true culprit may be the process conditions.
So, how do you make a viral vector “happy”? Dr. Rayat explained that LVs are not sensitive to shear if they are in a stable environment. The group observed that LVs “just don’t like to be concentrated in spent media”. Therefore, moving the vectors into a more stable buffer via diafiltration before concentrating them is critical for maintaining functionality. This understanding allows for more aggressive process optimization, such as using higher shear in TFF, which can improve productivity without sacrificing the product.
Dr. Rayat’s talk was a powerful reminder to “understand first the operating parameters of your process”. By questioning assumptions and applying bioprocess fundamentals, her group has been able to consistently achieve high-recovery rates. We extend a sincere thank you to Dr. Andrea Rayat for her fantastic presentation and to all our partners who attended and participated in the engaging Q&A session.