Antibody Purification Using Membrane Adsorbers - A membrane adsorber in retention mode can be used efficiently in a commercial antibody manufacturing process. - BioPharm International

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Antibody Purification Using Membrane Adsorbers
A membrane adsorber in retention mode can be used efficiently in a commercial antibody manufacturing process.


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Affinity Chromatography Step


Figure 1. Teleukin elution profile after the affinity chromatography step, based on absorbance at 280 nm
The initial step in the purification train is a standard Protein A affinity chromatography separation carried out by loading the filtered culture medium from the bioreactor onto a column pre-equilibrated with phosphate-buffered saline (PBS). The medium is loaded overnight at room temperature under conditions that allow a contact time of approximately 30 s. The column is then washed through with an acetate saline buffer at pH 5.0, and the antibody is eluted with an acetate saline buffer at pH 3.0. The eluted product is adjusted to pH 6.0 and diluted to a final conductivity of 8.0 mSi/cm before loading onto the Q/S dual adsorber. As shown by the elution profile in Figure 1, it is possible to recover up to 90% of the product in this step at a >90% purity.

The Polishing Step: A Q/S Dual Adsorber System


Figure 2. The Q/S dual adsorber system operating in series during the polishing step
The polishing step is carried out using two Sartobind ion exchange adsorbers, a 7-mL Sartobind Q for the AEX step, and a 70-mL Sartobind S for the CEX step. These are arranged in series on an Amersham Akta Pilot (GE Healthcare, Uppsala, Sweden) as shown in Figure 2. However, for washing and elution, the two adsorbers can be operated independently, as shown in Figure 3. The two operational modes are selected by the operator using the Unicorn 4.12 management software (GE Healthcare).


Figure 3. The Q/S dual adsorption system operating in independent mode to facilitate elution from the Sartobind S adsorber. It is also possible to operate the Sartobind Q adsorber independently (not shown).
Before loading, the system is set to the "in series" mode and the adsorbers are washed through with 1 M NaCl and then sanitized in place with 1 M NaOH. After this treatment, the system is washed with 50 mM NaCl in pH 6.0 acetate/EDTA buffer (F2 buffer A). After washing and sanitizing, the eluate from the affinity purification can be loaded onto the Sartobind Q adsorber at a rate of up to 150 mL/min, a process that can take up to 40 min for a maximum 6 L of feed (or up to 500 mg of antibody), although greater amounts can be processed by splitting into multiple batches. In the "in series" mode, the flow-through containing the antibody elutes from the Sartobind Q step directly into the Sartobind S adsorber, wherein the target antibody binds to the sorbent. The system is then washed with 10 volumes of loading buffer before the operator switches it to the independent mode, allowing the Sartobind S adsorber to be washed with another 15 volumes of buffer at a flow rate of 350 mL/min before elution.


Figure 4. Teleukin elution profile after the affinity chromatography step, based on absorbance at 280 nm
Salt gradient elution is carried out in independent mode at 350 mL/min using a continuous gradient from F2 buffer A (50 mM NaCl, conductivity 8.0–8.5 mS/cm) to F2 buffer B (like buffer A but 1 mM NaCl, conductivity 86.0–87.0 mS/cm), which goes from 0% to 100% F2 buffer B in 20 volumes. This step takes from 40 to 60 min and has a yield of up to 95%. A typical elution profile is shown in Figure 4.


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