Activated Cross-linked Agarose for the Rapid Development of Affinity Chromatography Resins - Antibody Capture as a Case Study
August 16th, 2019
In this procedure, a DsRed-based epitope ligand is immobilized to produce a highly selective affinity resin for the capture of monoclonal antibodies from crude plant extracts or cell culture supernatants, as an alternative to Protein A.
Monoclonal antibodies dominate the biopharmaceutical market and are typically purified by Protein A chromatography. The according resin is a major cost driver during production affecting the price of antibody-based therapeutics. Here we describe a new affinity ligand based on the fluorescent protein that is read as a carrier for the linear epitope of HIV neutralizing antibody 2F5.
In general our method allows the fast generation of affinity chromatography resins which can be used for the capture of monoclonal antibodies. We demonstrated this capability by capturing antibody 2F5 from crude plant extract. We optimized the capture conditions and solution buffer in order to improve the dynamic binding capacity and the resin reusability.
Our resin allows generally looser conditions than Protein A and has the potential to reduce purification costs of monoclonal antibodies. Furthermore, the resin can easily be adapted to other antibodies which bind to linear epitopes. To begin this procedure, adjust the concentration of the prepared affinity ligand solution so that is in the range of 5 to 15 grams per liter as defined by the design of experiments.
Store the solution on ice until the coupling reaction is ready. Next, fill one two milliliter syringe with the DFE solution. And prepare an adapter to mount the syringes on NHS-activated cross-link agarose columns with a bed volume of one milliliter.
For every 10 columns used for coupling, prepare 30 milliliters of deactivation solution, 30 milliliters of low pH solution, and one milliliter of storage solution. Then prepare 20 milliliters of one millimolar hydrochloric acid in a tube. And incubate it on ice for at least 20 minutes.
Prepare a precision scale to monitor the flow through fractions for all steps during the coupling reaction. After this, open a sealed NHS-activated crosslinked agarose column. Apply a drop of buffer onto the adapter inlet, to prevent air from entering the column.
Mount the syringe adapter at the column inlet. Wash the column with six milliliters of ice cold one millimolar hydrochloric acid, at a flow rate less that one milliliter per minute. Using a two milliliter syringe, immediately inject 1.5 milliliters of DFE solution at a flow rate less than one milliliter per minute.
And collect the flow through fraction on a precision scale for subsequent analysis. Seal the column at both ends and incubate for 15 to 45 minutes, at 22 degrees Celsius. Next inject six milliliters of the activation solution, followed by six milliliters of low pH solution, at a flow rate less than one milliliter per minute, remove non covalently bound ligands from the resin.
Inject six milliliters of the activation solution, and incubate the column for 15 minutes. After this, inject six milliliters of low pH solution into the column. Followed by six milliliters of the activation solution.
Then inject another six milliliters of low pH solution into the column. Inject two milliliters of storage solution into the column, and store it at four degrees Celsius. First prepare 100 milliliters of either the clarified plant extract containing 2F5, or the supernatant for the preferred cell based expression system, which also contains 2F5.
Next prepare the equilibration buffer, and the high iron X strength illusion buffer, as outlined in the text protocol. Flush the chromatography system with the buffers. Mount a DFE affinity column on the chromatography system.
And equilibrate with five CV of equilibration buffer, at a flow rate of one milliliter per minute. Monitor the UV absorbance at 280 nanometers. Then load 80 milliliters of either the clarified plant extract, or the supernatant onto the column at a flow rate of 5 milliliters per minute.
To guarantee a contact time of two minutes. Collect the flow through samples in two milliliter fractions or breakthrough curve reconstruction. Store the flow through samples at four degrees Celsius, if immediate sample analysis is not possible.
After this wash the column with 6CV of equilibration buffer. Collect a sample at the beginning, middle and end of the wash. Dilute the MAB2F5 with five volumes of high ionic strength illusion buffer.
Collect the DFE fraction when the UV signal at 280 nanometer has increased to five milli absorbance units above the baseline. Optimize the illusion buffer for each epitope-antibody pair, as outlined in the text protocol. The fusion protein DFE is expressed in transgenic tobacco plants, grown in a greenhouse.
The overall recovery of DFE is 23.5 milligrams per kilogram. With a purity of over 90%The absolute amount of DFE immobilized on the resin increases with the mass of DFE injected into the column, and plateaus at around 15 grams per liter, whereas the coupling yield declines continuously as more DFE is injected. The DFE molecules are seen to retain their red florescence, even after coupling.
The color intensity corresponds to the total amount of immobilized DFE. Therefore column color can be used as a simple quality control parameter to estimate the coupling efficiency, and column quality. The recombinant 2F5 antibody is transiently produced in Nicotiana benthamiana plants grown in a phytotron.
The capture of 2F5 from the crude plant extract, is tested using affinity columns, coupled with approximately seven milligrams of purified DFE. A magnesium chloride concentration of 1.25 molar is sufficient to elute 2F5 from the DFE affinity resin with a recovery close to 100%and a purity of approximately 97%which is comparable to Protein A resins. The DBC of the DFE affinity resin at 10%2F5 breakthrough, declines linearly over the course of the 25 cycles, to about 15%of the initial value.
We used a design of experiments approach to optimize the coupling capacity of our affinity ligand. These conditions can be fine tuned for other ligands in the future. Our method uses florescent protein to thread a sub carrier protein for the product specific ligand.
At the same time just add functions as a visual quality indicator of the mobilization procedure, providing an immediate and intuitive feedback to the operator.
Overview
This study presents a novel DsRed-based affinity resin for the selective capture of monoclonal antibodies from crude plant extracts or cell culture supernatants. The method aims to reduce purification costs compared to traditional Protein A chromatography.
Key Study Components
Area of Science
- Biotechnology
- Protein purification
- Monoclonal antibodies
Background
- Monoclonal antibodies are crucial in biopharmaceuticals.
- Protein A chromatography is a common but costly purification method.
- New methods are needed to lower production costs.
- Fluorescent proteins can be utilized for affinity chromatography.
Purpose of Study
- To develop an alternative affinity resin for monoclonal antibody purification.
- To optimize capture conditions for improved binding capacity.
- To demonstrate the resin's adaptability for various antibodies.
Methods Used
- Preparation of a DsRed-based affinity ligand solution.
- Coupling the ligand to NHS-activated agarose columns.
- Testing the resin with clarified plant extracts containing antibodies.
- Monitoring UV absorbance during purification steps.
Main Results
- The new resin allows for efficient capture of antibodies with high purity.
- Recovery rates of nearly 100% were achieved for the tested antibodies.
- The resin demonstrated better reusability compared to Protein A.
- Coupling efficiency can be visually monitored through fluorescence.
Conclusions
- The DsRed-based resin is a promising alternative for antibody purification.
- It can potentially lower costs in biopharmaceutical production.
- Future adaptations for other antibodies are feasible.
Frequently Asked Questions
Executive Industry Relevance
Protein A chromatography remains a major cost driver in monoclonal antibody purification, impacting the affordability of biologics. This method presents a cost-effective alternative using a DsRed-based affinity ligand immobilized on activated cross-linked agarose, enabling selective capture of antibodies with linear epitopes from crude extracts. The approach supports early-stage target validation and assay development by providing a reusable, visually quantifiable resin system that reduces reliance on expensive ligands.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses through selective capture of epitope-specific antibodies from complex mixtures.
- Operational Value: Supports biological de-risking by validating target engagement using a linear epitope ligand expressed in plant systems.
Screening & Assay Development
- Scientific Value: Provides a standardized affinity matrix for quantitative measurement of antibody binding in crude extracts.
- Operational Value: Enables assay standardization and reproducibility through fluorescence-based coupling efficiency monitoring.
Translational & Preclinical Research
- Scientific Value: Facilitates translational biomarker alignment by allowing purification of functional antibodies from disease-relevant expression systems.
- Operational Value: Supports predictive confidence in lead identification through consistent recovery and purity across multiple cycles.
Pipeline & Workflow Integration
The method fits within the discovery continuum from early target validation to lead identification, offering a platform for rapid resin generation applicable to multiple antibody targets with linear epitopes.
- Discovery Biology: Supports hypothesis testing and pathway clarification by enabling isolation of specific antibodies from complex biological samples.
- Screening: Delivers assay readiness and quantitative outputs via UV absorbance monitoring and fluorescence-coupled ligand quantification.
- Analytics: Provides measurable readouts such as dynamic binding capacity and recovery rates to compare purification conditions.
- Translational Research: Connects discovery to preclinical continuity by producing purified antibodies suitable for functional validation.
- Enterprise Reuse: Establishes a reusable capability for rapid adaptation to new antibody targets through ligand exchange.
Operational & Enterprise Impact
- Scientific Value: Predictive confidence in target validation, reduction of mechanistic ambiguity in antibody-ligand interactions.
- Operational Value: Standardization, reproducibility, and scalability of resin production using design-of-experiments optimization.
- Strategic Value: Better go/no-go decisions, capital efficiency, and reduced late-stage biological risk through early purification feasibility.
- Portfolio Impact: Risk-adjusted prioritization and advancement decisions based on achievable purity and recovery metrics.
Implementation Considerations
- Requires expertise in protein expression, purification, and conjugation chemistry.
- Needs instrumentation for flow-controlled coupling, UV monitoring, and fraction collection.
- Demands cross-team standardization of ligand concentration, buffer conditions, and coupling timelines.
- Involves adaptation considerations for different epitope-antibody pairs, particularly in optimizing elution buffers.
- Includes practical limitations such as ligand leaching over cycles and declining dynamic binding capacity with reuse.
