(612b) Continuous Purification of a Viral Vaccine Using Aqueous Two-Phase Extraction and Tangential Flow Filtration

Quick and reliable production of vaccines can have life-saving implications for patients. Continuous manufacturing, which is beginning to gain favor in the pharmaceutical industry, propels this quick and reliable production by enabling high product throughput for a smaller manufacturing footprint, reducing contamination risk during the production process, and increasing consistency of the product. However, traditional purification steps such as bind-and-elute affinity chromatography are difficult to adapt for continuous processing.

We have constructed a continuously-processing purification system for virus-based vaccines which leverages tangential flow filtration (TFF) for concentration and formulation as well as multiple aqueous two-phase extractions (ATPE) for purification. ATPE provides a more cost-effective and environmentally-friendly purification alternative to liquid chromatography, while being highly compatible with continuous manufacturing. ATPE is here composed of semi-miscible polyethylene glycol (PEG) polymer and citrate salt solutions. By leveraging hydrophobic and electrostatic interactions between the viral product and the ATPE components, the partitioning behavior of the viral product can be adjusted. The process begins by concentrating clarified cell culture material with a single-pass TFF. Next, during the first stage of ATPE, salting-out by high citrate concentrations and the amphiphilicity of the PEG-rich phase drive the virus into the PEG-rich phase, while the cell culture impurities remain in the citrate phase. However, the PEG solution is highly viscous so the product must be back-extracted into citrate solution to allow for further processing. Therefore, the virus-laden PEG is harvested for a second stage of ATPE, where low component concentrations coax the virus into a fresh citrate solution. From there, the purified product is formulated using a second single-pass TFF.

Using porcine parvovirus as a vaccine model, continuous recoveries so far correspond with batch experiments. Recoveries may further be improved by using an osmolyte additive to increase virus recovery during forward extraction. At this scale, from start to finish, the purification process is estimated to process 30 mL of concentrated PPV feedstock per hour. In future development, the concentration factor, fouling behavior, and a non-disruptive cleaning method will be determined for the TFFs. An interface sensing mechanism will also be developed to provide feedback for system control. This continuous purification framework presents a strategy for more efficient vaccine manufacturing at a lower cost compared to traditional methods, which could reduce cost and increase access to patients in need of therapies.