Purification of antibodies using elastin like polypeptide based affinity precipitation

Abstract

With the final aim being the development of a continuous affinity precipitation setup for the purification of mAbs, the first part deals with an improvement to the affinity precipitation process. Optimal conditions for the new elution without resolubilization process are identified by carrying out a high-throughput study in batch mode. We successfully obtain high recoveries above 90% for both the mAbs tested.

Low pH conditions were also evaluated for their ability to elute and recover pure mAb from the captured precipitate, again in a continuous fashion. Finally, appropriate cycling of depth filters was carried out to enable continuous operation of mAb capture, washing and elution. The developed continuous process was successful in purifying mAb with a high purity and yield.

Following the development of this novel affinity precipitation process, a lab-scale continuous affinity precipitation system was developed. This setup involves the binding of the mAb to ELP-Z, precipitation of the complex, capture and washing of the precipitates, and removal of the mAb from the ELP-Z precipitates, all in a continuous fashion. This system employs static mixers for efficient mixing during the binding and precipitation steps. The collected information was then employed to select appropriately sized depth filters (2um-0.2um) for the efficient capture and subsequent washing of ELP-Z-mAb precipitates.

Future efforts can be carried out to scale-up the current affinity precipitation setup. The affinity precipitation process can also be extended to protein non-mAb therapeutics. Affinity ligand corresponding to the protein of interest can be identified by either phage display or rational design. The fusion of the ELP with the affinity ligand can be made. The optimization of the process is expected to be similar to the ELPZ-mAb process optimization. Further, research is being carried out by the Cramer and Przybycien to improve upon the proof of concept affinity precipitation setup developed in Chapter 3. In summary, continuous affinity precipitation is a versatile downstream processing technique that can potentially be used to purify a wide variety of therapeutics.

Continuous downstream purification of proteins is a field that is assuming increasing importance in the biotech industry. Affinity precipitation can help the industry in making a transition from the existing batch capture step using affinity chromatography to a continuous capture step. Elastin-like polypeptides with their property of reversible phase transition from soluble to insoluble precipitated state due to change in solution conditions can be used for affinity precipitation. This thesis focuses on the purification of monoclonal antibodies(mAbs) using ELP-Z, which is a fusion of an elastin-like polypeptide and the Z-domain of Protein-A.