Recombinant antibody expression and Protein A/G purification
Materials Required
Principle
Recombinant antibody expression produces antibody chains from cloned antibody genes in mammalian cells, commonly HEK293-derived cells, so that secreted IgG or Fc-fusion antibodies can be collected from culture supernatant[1][2][3]. Protein A/G purification is affinity chromatography in which immobilized Protein A, Protein G, or Protein A/G binds the antibody Fc region; nonbound culture components are washed away, and bound antibody is recovered by changing buffer conditions, commonly acidic elution followed by neutralization[4][5].
MCE has not independently verified the accuracy of these methods. They are for reference only.
Experimental Materials
• Use mammalian expression plasmids encoding matched antibody heavy and light chains, HEK293 or HEK293-6E suspension/adherent cells, serum-containing or serum-free culture medium as reported for the chosen expression system, PEI for DNA delivery when following PEI-based methods, PBS or equivalent neutral buffer for column equilibration/washing, acidic elution buffer for antibody recovery, and neutralization buffer immediately after elution[1][2][3][4].
• Use Protein A, Protein G, or Protein A/G immobilized chromatography resin to capture IgG or Fc-containing recombinant antibodies, selecting the ligand according to antibody species and subclass because Protein A and Protein G differ in subclass and species binding profiles[4][5].
• Use sterile mammalian cell-culture vessels or shake flasks, a CO2 incubator or CO2 orbital shaker, centrifugation equipment for supernatant clarification, chromatography columns or an FPLC system for Protein A/G capture, and SDS-PAGE or comparable protein-analysis equipment to assess purity and antibody size[1][3][4].
• Use Protein A, Protein G, or Protein A/G immobilized chromatography resin to capture IgG or Fc-containing recombinant antibodies, selecting the ligand according to antibody species and subclass because Protein A and Protein G differ in subclass and species binding profiles[4][5].
• Use sterile mammalian cell-culture vessels or shake flasks, a CO2 incubator or CO2 orbital shaker, centrifugation equipment for supernatant clarification, chromatography columns or an FPLC system for Protein A/G capture, and SDS-PAGE or comparable protein-analysis equipment to assess purity and antibody size[1][3][4].
Experimental Procedure
• Prepare expression plasmid DNA encoding antibody heavy and light chains, maintain HEK293-derived cells under the culture format used for the selected expression system, and confirm that cells are suitable for transfection before antibody production[1][2][3].
• For PEI-based expression, prepare DNA and PEI under the conditions reported for the selected HEK293 protocol rather than substituting unsupported ratios[1][2][3].
• Transfect HEK293-derived cells with antibody-expression plasmids and culture them to allow secretion of recombinant antibody into the medium; published HEK293 protocols report harvest windows within several days after transfection, and optimized HEK293-6E work reported 5-8 day production periods depending on feeding strategy[1][2].
• Clarify the culture supernatant by centrifugation or equivalent removal of cells and debris before loading onto Protein A/G resin, because affinity chromatography is applied to soluble antibody-containing material[3][4].
• Equilibrate the Protein A, Protein G, or Protein A/G column in neutral binding buffer, load clarified supernatant under binding conditions, wash away unbound material, elute bound antibody by changing buffer conditions that disrupt Fc-ligand binding, and neutralize acidic fractions after collection[4][5].
• Analyze eluted fractions by SDS-PAGE or another protein-quality method; one HEK293-6E scFv-Fc study reported Protein A purification and desalting giving >98% purity for scFv-Fc antibodies under its conditions[1].
• Assess expression by measuring antibody in culture supernatant or purified fractions and assess purification by comparing load, flow-through, wash, and elution fractions by SDS-PAGE or another validated protein assay[1][3][4].
• Include a nontransfected or mock-transfected culture as a negative process control, retain an aliquot of starting supernatant to evaluate capture efficiency, and use repeated productions when comparing vectors, constructs, or culture conditions because published optimization studies used replicate productions to compare antibody-expression conditions[1].
• For PEI-based expression, prepare DNA and PEI under the conditions reported for the selected HEK293 protocol rather than substituting unsupported ratios[1][2][3].
• Transfect HEK293-derived cells with antibody-expression plasmids and culture them to allow secretion of recombinant antibody into the medium; published HEK293 protocols report harvest windows within several days after transfection, and optimized HEK293-6E work reported 5-8 day production periods depending on feeding strategy[1][2].
• Clarify the culture supernatant by centrifugation or equivalent removal of cells and debris before loading onto Protein A/G resin, because affinity chromatography is applied to soluble antibody-containing material[3][4].
• Equilibrate the Protein A, Protein G, or Protein A/G column in neutral binding buffer, load clarified supernatant under binding conditions, wash away unbound material, elute bound antibody by changing buffer conditions that disrupt Fc-ligand binding, and neutralize acidic fractions after collection[4][5].
• Analyze eluted fractions by SDS-PAGE or another protein-quality method; one HEK293-6E scFv-Fc study reported Protein A purification and desalting giving >98% purity for scFv-Fc antibodies under its conditions[1].
• Assess expression by measuring antibody in culture supernatant or purified fractions and assess purification by comparing load, flow-through, wash, and elution fractions by SDS-PAGE or another validated protein assay[1][3][4].
• Include a nontransfected or mock-transfected culture as a negative process control, retain an aliquot of starting supernatant to evaluate capture efficiency, and use repeated productions when comparing vectors, constructs, or culture conditions because published optimization studies used replicate productions to compare antibody-expression conditions[1].
Troubleshooting
Problem: Low recombinant antibody yield.
• Possible Cause: Expression vector, host-cell format, culture density, or feeding conditions are not optimal for the antibody format.• Literature-supported Solution: Use a reported HEK293-derived expression workflow and optimize vector/culture conditions within literature-supported ranges; HEK293-6E suspension culture with optimized vectors and fed-batch supplementation produced substantially higher scFv-Fc yields than adherent HEK293T in the cited study[1][2].
Problem: Poor Protein A/G capture.
• Possible Cause: The antibody subclass or species is poorly matched to the selected Fc-binding ligand.• Literature-supported Solution: Select Protein A, Protein G, or Protein A/G according to known species/subclass binding behavior rather than assuming universal capture[4][5].
Problem: Low purity after capture.
• Possible Cause: Nonbound or weakly bound host-cell proteins remain after insufficient washing or the feed stream contains impurities not removed by single-step capture.• Literature-supported Solution: Analyze load, wash, and elution fractions and adjust the affinity-chromatography workflow using literature-supported wash/elution conditions; affinity chromatography depends on selective ligand binding followed by washing and desorption, and Protein A capture may require polishing depending on product-quality needs[4][5].
References:
- [1]. Jäger V, et al. High level transient production of recombinant antibodies and antibody fusion proteins in HEK293 cells. BMC Biotechnol. 2013;13:52. [Content Brief]
- [2]. L’Abbé D, et al. Transient Gene Expression in Suspension HEK293-EBNA1 Cells. Methods Mol Biol. 2018;1850:1-16. [Content Brief]
- [3]. Elgundi Z, et al. Laboratory Scale Production and Purification of a Therapeutic Antibody. J Vis Exp. 2017;(119):e55153. [Content Brief]
- [4]. Grodzki AC, et al. Antibody purification: affinity chromatography - protein A and protein G Sepharose. Methods Mol Biol. 2010;588:33-41. [Content Brief]
- [5]. Hober S, et al. Protein A chromatography for antibody purification. J Chromatogr B Analyt Technol Biomed Life Sci. 2007;848(1):40-47. [Content Brief]
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