Separation of antigens and antibodies by immunoaffinity chromatography

Immunoaffinity chromatography for the preparation of equine tetanus immunoglobulin F(ab')2 for enhanced safety and efficacy

Typically, the antigen-specific antibodies constitute a small fraction-often estimated to be around 2-10 %-of the total IgG in the serum after immunization. This low percentage necessitates the use of purification techniques to enrich the antigen-specific antibodies for therapeutic or research purposes. This study introduces an affinity chromatography column using NHS-activated Sepharose as a matrix and the tetanus toxin subunit C, TeNT-Hc-C869A, as a ligand, enabling the purification of polyclonal antibodies with high specificity. This process improves antitoxin purity to over 95 %, effectively neutralizes the tetanus toxin, and removes inactive antibodies and other impurities, thereby reducing the risk of allergic reactions caused by heterologous proteins. This method offers promising advancements for tetanus prevention and treatment. The developed affinity column is applicable for purifying equine plasma, enzymatically digested equine tetanus F(ab')₂, and human immunoglobulins targeting the tetanus toxin. Following purification, the specific activities of these preparations increased by factors of 5, 5, and 30, respectively, enhancing their clinical safety profiles. The affinity matrix exhibits durability, high loading capacity, and non-toxicity, supporting its scalability. This streamlined, cost-effective preparation process highlights the column's potential for broad applications in the biopharmaceutical field.

Production and characterization of pertussis toxin specific monoclonal and polyclonal antibodies: Implication for toxin purification and detection

BACKGROUND

Pertussis is a pulmonary disease caused by the gram-negative bacteria Bordetella pertussis (BP) with a high fatality rate among newborns and young children. Pertussis toxin (PT) is essential for pertussis pathogenesis as well as production of acellular pertussis vaccines (aPV). Traditional PT purification procedures are laborious and yield low purity and recovery rates. Also, due to the low production levels of PT by BP and the difficulties of purification, an appropriate immunoassay is needed to monitor PT concentrations upstream and downstream of the production process. This study investigates production and application of monoclonal and polyclonal antibodies for efficient PT purification and quantification.

METHODS

Rabbits and mice were immunized with native PT to produce polyclonal and monoclonal antibodies (MAbs). The MAbs were selected based on affinity, isotype and specificity, as determined by enzyme-linked immunosorbent assay (ELISA) and immunoblotting. The native PT antigen was purified using an immunoaffinity column. The purity and recovery rates of native PT were analyzed by ELISA, SDS-PAGE, and immunoblotting. Additionally, monoclonal and polyclonal antibodies were used to establish an ELISA assay for measurement of PT concentration.

RESULTS

A highly pure PT with recovery rates of around 74 ± 4.9 % was obtained following purification by immunoaffinity column, using polyclonal antibodies. Furthermore, the designed ELISA demonstrated suitable reactivity for measurement of the PT antigen.

CONCLUSION

Our results indicate suitability of the produced monoclonal and polyclonal anti-PT antibodies for purification and monitoring of PT by immunoaffinity chromatography and ELISA, respectively. The immunoaffinity method offers an efficient replacement for PT purification in the context of developing aPV.

Microbial lipases: advances in production, purification, biochemical characterization, and multifaceted applications in industry and medicine

Lipases are biocatalysts of significant industrial and medical relevance, owing to their ability to hydrolyze lipid substrates and catalyze esterification reactions under mild conditions. This review provides a comprehensive overview of microbial lipases' production, purification, and biochemical properties. It explores optimized fermentation strategies to enhance enzyme yield, including using agro-industrial residues as substrates. The challenges associated with purification techniques such as ultrafiltration, chromatography, and precipitation are discussed, alongside methods to improve enzyme stability and specificity. Additionally, the review addresses the growing importance of genetic engineering approaches for improving lipase characteristics, such as activity, stability, and specificity.Additionally, this review highlights the diverse applications of microbial lipases in industries, including food, pharmaceuticals, biofuels, and cosmetics. The enzyme's role in bioremediation, biodegradation, and the synthesis of bioactive compounds is analyzed, emphasizing its potential in sustainable and eco-friendly technologies. The biocatalytic properties of lipases make them ideal candidates for the green chemistry initiatives in these industries. In the biomedical domain, lipase has shown promise in drug delivery systems, anti-obesity treatments, and diagnostics.This review provides insights into the strategic development of microbes as microbial cell factories for the sustainable production of lipases, paving the way for future research and industrial innovations in enzyme technology.

Functionalization of Mesoporous Silica with a G-A-Mismatched dsDNA Chain for Efficient Identification and Selective Capturing of the MutY Protein

MUTYH adenine DNA glycosylase and its homologous protein (collectively MutY) are typical DNA glycosylases with a [4Fe4S] cluster and a helix-hairpin-helix (HhH) motif in its structure. In the present work, the binding behaviors of the MutY protein to dsDNA containing different base mismatches were investigated. The type and distribution of base mismatch in the dsDNA chain were found to influence the DNA-protein binding interaction greatly. The [4Fe4S] cluster of the MutY protein is able to identify a G-A mismatch in the dsDNA chain specifically by monitoring the anomalies of charge transport in the dsDNA chain, allowing the entrance of the identified dsDNA chain into the internal cavity of the MutY protein and the strong DNA-protein binding at the HhH motif of the protein through multiple H-bonds. The dsDNA chain with a centrally located G-A mismatch is thus functionalized on mesoporous silica (MSN) via amination reaction, and the obtained dsDNA(G-A)@MSN is used as a powerful sorbent for the selective capturing of the MutY protein from complex samples. By using 0.5% NH3·H2O (m/v) as a stripping reagent, efficient isolation of the MutY protein from different cell lines and bacteria is achieved and the recovered MutY protein is demonstrated to maintain favorable DNA adenine glycosylase activity.

Molecular docking and inhibition studies of vulpinic, carnosic and usnic acids on polyol pathway enzymes

Aldose reductase (AR) and sorbitol dehydrogenase (SDH) are important enzymes of the polyol pathway. In the current study, inhibitory effects of vulpinic acid (VA) carnosic acid (CA) and usnic acid (UA) on purified AR and SDH enzymes were determined. These enzymes inhibition could be essential to prevent diabetic complications. AR and SDH enzymes were purified from sheep kidney. Then, VA, CA and UA were tested in various concentrations against these enzymes activity in vitro. K_I values were found to be as 1.46 ± 0.04, 5.13 ± 0.25 and 11.71 ± 0.27 μΜ for VA, CA and UA, respectively, for AR. K_I constants were found to be as 15.32 ± 0.34, 145.60 ± 2.17 and 213.40 ± 2.64 μΜ VA, CA and UA, respectively, for SDH. These findings indicate that VA, CA and UA could be useful in the treatment of diabetic complications.Communicated by Ramaswamy H. Sarma.

Evaluation of the Cardiovascular Effects of Coriandrum sativum and Citrus limon to Treat Arsenic-Induced Endothelial Damage and Hypertension in Rats

Based on the vernacular reputation of Coriandrum sativum and Citrus limon to treat hypertension, this study was designed to explore the cardiovascular effects of C. sativum (CS) and C. limon (CL) on arsenic-induced hypertension and endothelial damage. Hypertension was induced by arsenic (100 ppm) in drinking water. The crude methanolic extracts of CS and CL were tested for in vivo and in vitro activities using Power Lab. High performance liquid chromatography analysis of CS and CL showed the presence of phenolic compounds. In anesthetized rats, CS (50 mg) and CL (10 mg) showed a marked decrease in blood pressure of 51% and 35%, respectively. Similarly, ascorbic acid (10 mg) also showed a decreased blood pressure (41%). The CS and CL caused complete relaxation (0.003−5 mg/mL) against phenylephrine (1µM) and high K+ (80 mM)-induced contraction. The CS and CL, independently and in combination, exhibited marked (p < 0.001) attenuation in the blood pressure of the arsenic-induced hypertensive rats when compared with the controls. The beneficial effects of the CS and CL were also observed on lipid peroxidation and eNOS. These data suggest that CS and CL possess significant antihypertensive activity, possibly mediated via endothelium protection, and anti-oxidant effects. Thus, this study provides a rationale for the medicinal use of CS and CL in hypertension and also against arsenic-induced cardiovascular complications.

Protein Engineering: Advances in Phage Display for Basic Science and Medical Research

Functional Protein Engineering became the hallmark in biomolecule manipulation in the new millennium, building on and surpassing the underlying structural DNA manipulation and recombination techniques developed and employed in the last decades of 20th century. Because of their prominence in almost all biological processes, proteins represent extremely important targets for engineering enhanced or altered properties that can lead to improvements exploitable in healthcare, medicine, research, biotechnology, and industry. Synthetic protein structures and functions can now be designed on a computer and/or evolved using molecular display or directed evolution methods in the laboratory. This review will focus on the recent trends in protein engineering and the impact of this technology on recent progress in science, cancer- and immunotherapies, with the emphasis on the current achievements in basic protein research using synthetic antibody (sABs) produced by phage display pipeline in the Kossiakoff laboratory at the University of Chicago (KossLab). Finally, engineering of the highly specific binding modules, such as variants of Streptococcal protein G with ultra-high orthogonal affinity for natural and engineered antibody scaffolds, and their possible applications as a plug-and-play platform for research and immunotherapy will be described.

Antibody Purification Using Affinity Chromatography

Antibodies are an integral part of many biological assays and biotherapeutics. However, the sources from which antibodies are derived frequently contain other contaminants which may interfere with assays or cause adverse reactions if administered in vivo. Therefore, a means of isolating these antibodies from their source at high levels of purity is critical. Affinity chromatography is currently one of the most widely applied methods for the purification of antibodies. This method relies on specific and reversible, interactions between antibody structures, or recombinant tags fused to these structures, and ligands immobilized on solid support matrices, generally within a column. Herein, common chromatographic methods applied to antibody purification are described. These include the purification of IgG, and its recombinant forms, through protein A, protein G and immobilized metal affinity chromatography.

Temperature responsive smart polymer for enabling affinity enrichment of current coronavirus (SARS-CoV-2) to improve its diagnostic sensitivity

The current commercially available SARS-CoV-2 diagnostic approaches including nucleic acid molecular assaying using polymerase chain reaction (PCR) have many limitations and drawbacks. SARS-CoV-2 diagnostic strategies were reported to have a high false-negative rate and low sensitivity due to low viral antibodies or antigenic load in the specimens, that is why even PCR test is recommended to be repeated to overcome this problem. Thus, in anticipation of COVID-19 current wave and the upcoming waves, we should have an accurate and rapid diagnostic tool to control this pandemic. In this study, we developed a novel preanalytical strategy to be used for SARS-CoV-2 specimen enrichment to avoid misdiagnosis. This method depends on the immuno-affinity trapping of the viral target followed by in situ thermal precipitation and enrichment. We designed, synthesized, and characterized a thermal-responsive polymer poly (N-isopropylacrylamide-co-2-hydroxyisopropylacrylamide-co-strained alkyne isopropylacrylamide) followed by decoration with SARS-CoV-2 antibody. Different investigations approved the successful synthesis of the polymeric antibody conjugate. This conjugate was shown to enrich recombinant SARS-CoV-2 nucleocapsid protein samples to about 6 folds. This developed system succeeded in avoiding the misdiagnosis of low viral load specimens using the lateral flow immunoassay test. The strength of this work is that, to the best of our knowledge, this report may be the first to functionalize SARS-CoV-2 antibody to a thermo-responsive polymer for increasing its screening sensitivity during the current pandemic.

Protein L—More Than Just an Affinity Ligand

In the past 30 years, highly specific drugs, known as antibodies, have conquered the biopharmaceutical market. In addition to monoclonal antibodies (mAbs), antibody fragments are successfully applied. However, recombinant production faces challenges. Process analytical tools for monitoring and controlling production processes are scarce and time-intensive. In the downstream process (DSP), affinity ligands are established as the primary and most important step, while the application of other methods is challenging. The use of these affinity ligands as monitoring tools would enable a platform technology to monitor process steps in the USP and DSP. In this review, we highlight the current applications of affinity ligands (proteins A, G, and L) and discuss further applications as process analytical tools.

Mass Spectrometry-Based Methods for Immunoglobulin G N-Glycosylation Analysis

Mass spectrometry and its hyphenated techniques enabled by the improvements in liquid chromatography, capillary electrophoresis, novel ionization, and fragmentation modes are truly a cornerstone of robust and reliable protein glycosylation analysis. Boost in immunoglobulin G (IgG) glycan and glycopeptide profiling demands for both applied biomedical and research applications has brought many new advances in the field in terms of technical innovations, sample preparation, improved throughput, and confidence in glycan structural characterization. This chapter summarizes mass spectrometry basics, focusing on IgG and monoclonal antibody N-glycosylation analysis on several complexity levels. Different approaches, including antibody enrichment, glycan release, labeling, and glycopeptide preparation and purification, are covered and illustrated with recent breakthroughs and examples from the literature omitting excessive theoretical frameworks. Finally, selected highly popular methodologies in IgG glycoanalytics such as liquid chromatography-mass spectrometry and matrix-assisted laser desorption ionization are discussed more thoroughly yet in simple terms making this text a practical starting point either for the beginner in the field or an experienced clinician trying to make sense out of the IgG glycomic or glycoproteomic dataset.

Characteristics of Immunoglobulin M Type Antibodies of Different Origins from the Immunologic and Clinical Viewpoints and Their Application in Controlling Antibody-Mediated Allograft Rejection

Antibody-mediated allograft rejection (AMR) hinders patient prognosis after organ transplantation. Current studies concerning AMR have mainly focused on the diagnostic value of immunoglobulin G (IgG)-type donor-specific antihuman leukocyte antigen antibodies (DSAs), primarily because of their antigen specificity, whereas the clinical significance of immunoglobulin M (IgM)-type DSAs has not been thoroughly investigated in the context of organ transplantation because of their nonspecificity against antigens. Although consensus regarding the clinical significance and role of IgM antibodies is not clear, as discussed in this review, recent findings strongly suggest that they also have a huge potential in novel diagnostic as well as therapeutic application for the prevention of AMR. Most serum IgM antibodies are known to comprise natural antibodies with low affinity toward antigens, and this is derived from B-1 cells (innate B cells). However, some of the serum IgM-type antibodies reportedly also produced by B-2 cells (conventional B cells). The latter are known to have a high affinity for donor-specific antigens. In this review, we initially discuss how IgM-type antibodies of different origins participate in the pathology of various diseases, directly or through cell surface receptors, complement activation, or cytokine production. Then, we discuss the clinical applicability of B-1 and B-2 cell-derived IgM-type antibodies for controlling AMR with reference to the involvement of IgM antibodies in various pathological conditions.

Aptamer-Based Affinity Chromatography for Protein Extraction and Purification

Aptamers are oligonucleotide molecules able to recognize very specifically proteins. Among the possible applications, aptamers have been used for affinity chromatography with effective results and advantages over most advanced protein separation technologies. This chapter first discusses the context of the affinity chromatography with aptamer ligands. With the adaptation of SELEX, the chemical modifications of aptamers to comply with the covalent coupling and the separation process are then extensively presented. A focus is then made about the most important applications for protein separation with real-life examples and the comparison with immunoaffinity chromatography. In spite of well-advanced demonstrations and the extraordinary potential developments, a significant optimization work is still due to deserve large-scale applications with all necessary validations. Graphical Abstract Aptamer-protein complexes by X-ray crystallography.

Poly(Hydroxyethyl Methacrylate) Immunoaffinity Cryogel Column for the Purification of Human Immunoglobulin M

Human immunoglobulin M (hIgM) antibodies are considered as hopeful tools for diseases therapy. Therefore, chromatography approaches are used to purify hIgM with a single step. In this study, we prepared a poly(hydroxyethyl methacrylate) based immunoaffinity p(HEMA-I) cryogel column by using cyanamide to immobilize antihuman immunoglobulin on the p(HEMA) cryogel for purification of hIgM in aqueous solution and artificial human plasma. The characterization of the p(HEMA) cryogel column was performed by using a scanning electron microscope (SEM), micro-computerized tomography (µ-CT), Fourier transform infrared spectroscopy (FTIR), swelling degree and macro-porosity. Further, the optimizations of various parameters were performed such as, pH, ionic strength, temperature and concentration of hIgM in aqueous solutions. In addition, the Langmuir adsorption model was supported by experimental results. Maximum adsorbed amount of hIgM corresponded to 11.1 mg/g at pH 5.75 [morpholino ethanesulfonic acid (MES buffer)]. Our results indicated that the p(HEMA-I) cryogel column can be reused at least 10 times without significant loss in adsorption capacity. As a natural source, artificial human plasma was selected for hIgM adsorption and the purity of hIgM was evaluated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Accurately cleavable goat β-lactoglobulin signal peptide efficiently guided translation of a recombinant human plasminogen activator in transgenic rabbit mammary gland

Poor expression is the key factor hampering the large-scale application of transgenic animal mammary gland bioreactors. A very different approach would be to evaluate the secretion of recombinant proteins into milk in response to a cleavable signal peptide of highly secreted lactoproteins.We previously reported rabbits harboring mammary gland-specific expression vector containing a fusion cDNA (goat β-lactoglobulin (BLG) signal peptide and recombinant human plasminogen activator (rhPA) coding sequences) expressed rhPA in the milk, but we did not realize the signal peptide contributed to the high rhPA concentration and did not mention it at that time. And the molecular structure and biological characteristics still remain unknown. So, rhPA in the milk was purified and characterized in the present study.rhPA was purified from the milk, and the purity of the recovered product was 98% with no loss of biological activity. Analysis of the N-terminal sequence, C-terminal sequence, and the molecular mass of purified rhPA revealed that they matched the theoretical design requirements. The active systemic anaphylaxis (ASA) reactions of the purified rhPA were negative. Taken together, these results indicated that the goat BLG signal peptide can efficiently mediate rhPA secretion into milk and was accurately cleaved off from rhPA by endogenous rabbit signal peptidase.We have reinforced the importance of a rhPA coding region fused to a cleavable heterologous signal peptide from highly secreted goat BLG to improve recombinant protein expression. It is anticipated that these findings will be widely applied to high-yield production of medically important recombinant proteins.

Purification of plant-derived anti-virus mAb through optimized pH conditions for coupling between protein A and epoxy-activated beads

The main goal of this research was to determine optimum pH conditions for coupling between protein A and epoxy-activated Sepharose beads for purification of monoclonal antibodies (mAbs) expressed in plants. To confirm the effect of pH conditions on purification efficacy, epoxy-activated agarose beads were coupled to protein A under the pH conditions of 8.5, 9.5, 10.5, and 11.5 (8.5R, 9.5R, 10.5R, and 11.5R, respectively). A total of 300 g of fresh leaf tissue of transgenic Arabidopsis expressing human anti-rabies mAb (mAb^P) SO57 were harvested to isolate the total soluble protein (TSP). An equal amount of TSP solution was applied to five resin groups including commercial protein A resin (GR) as a positive control. The modified 8.5R, 9.5R, 10.5R, and 11.5R showed delayed elution timing compared to the GR control resin. Nano-drop analysis showed that the total amount of purified mAb^PSO57 mAbs from 60 g of fresh leaf mass were not significantly different among 8.5R (400 μg), 9.5R (360 μg), 10.5R (380 μg), and GR (350 μg). The 11.5R (25 μg) had the least mAb^PSO57. SDS-PAGE analysis showed that the purity of mAb^PSO57 was not significantly different among the five groups. Rapid fluorescent focus inhibition tests revealed that virus-neutralizing efficacies of purified mAb^PSO57 from all the five different resins including the positive control resin were similar. Taken together, both pH 8.5 and 10.5 coupling conditions with high recovery rate should be optimized for purification of mAb^PSO57 from transgenic Arabidopsis plant, which will eventually reduce down-stream cost required for mAb production using the plant system.

Purification of IgG against ribonucleoprotein by a homemade immunoaffinity chromatography column for rabies diagnosis

Polyclonal or monoclonal antibodies against rabies virus ribonucleoprotein (RNP) conjugated to fluorescein isothiocyanate (FITC) have been employed for Rabies virus (RABV) antigen detection by the direct fluorescent antibody test (DFA). To date, these biomolecules have been purified by traditional methods such as precipitation by ammonium sulfate or ion exchange chromatography followed by ammonium sulfate precipitation, which allows only for partial detection of the protein of interest. In this study, we aimed to purify anti-RNP polyclonal horse IgG antibodies by cation-exchange chromatography in combination with a homemade immunoaffinity chromatography on RNP immobilized (RNP-IAC). Furthermore, to evaluate the accuracy of the prepared anti-RNP IgG fluorescent antibody in diagnostic purposes, DFA was applied for RABV antigen detection in suspected brain samples of different animal species. The combination of these two techniques made it possible to obtain antibodies with high selectivity and purity. Compared with the performance of the traditional method, anti-RNP IgG antibodies purified by RNP-IAC can be obtained from a smaller volume of hyperimmune serum and with greater avidity. Furthermore, the results obtained by DFA analyses revealed that the prepared anti-RNP IgG fluorescent antibody achieved 100% diagnostic specificity and sensitivity for RABV antigen detection. Thus, two-technique chromatographic, including RNP-IAC technology could be appropriate methods for the purification of polyclonal anti-RNP IgG for the use as a diagnostic reagent for rabies.

Applications of Nanomaterials for Immunosensing

In biomedical science among several other growing fields, the detection of specific biological agents or biomolecular markers, from biological samples is crucial for early diagnosis and decision-making in terms of appropriate treatment, influencing survival rates. In this regard, immunosensors are based on specific antibody-antigen interactions, forming a stable immune complex. The antigen-specific detection antibodies (i.e., biomolecular recognition element) are generally immobilized on the nanomaterial surfaces and their interaction with the biomolecular markers or antigens produces a physico-chemical response that modulates the signal readout. Lowering the detection limits for particular biomolecules is one of the key parameters when designing immunosensors. Thus, their design by combining the specificity and versatility of antibodies with the intrinsic properties of nanomaterials offers a plethora of opportunities for clinical diagnosis. In this review, we show a comprehensive set of recent developments in the field of nanoimmunosensors and how they are progressing the detection and validation for a wide range of different biomarkers in multiple diseases and what are some drawbacks and considerations of the uses of such devices and their expansion.

Temperature-Responsive Magnetic Nanoparticles for Enabling Affinity Separation of Extracellular Vesicles

Small magnetic nanoparticles that have surfaces decorated with stimuli-responsive polymers can be reversibly aggregated via a stimulus, such as temperature, to enable efficient and rapid biomarker separation. To fully realize the potential of these particles, the synthesis needs to be highly reproducible and scalable to large quantity. We have developed a new synthesis for temperature-responsive magnetic nanoparticles via an in situ co-precipitation process of Fe2+/Fe3+ salts at room temperature with poly(acrylic acid)- block-poly( N-isopropylacrylamide) diblock co-polymer template, synthesized via the reversible addition-fragmentation chain-transfer polymerization method. These particles were 56% polymer by weight with a 6.5:1 Fe/COOH ratio and demonstrated remarkable stability over a 2 month period. The hydrodynamic diameter remained constant at ∼28 nm with a consistent transition temperature of 34 °C, and the magnetic particle separation efficiency at 40 °C was ≥95% over the 2 month span. These properties were maintained for all large-scale synthesis batches. To demonstrate the practical utility of the stimuli-responsive magnetic nanoparticles, the particles were incorporated into a temperature-responsive binary reagent system and efficiently separated a model protein biomarker (mouse IgG) as well as purified extracellular vesicles derived from a human biofluid, seminal plasma. The ease of using these particles will prove beneficial for various biomedical applications.

DNA aptamer affinity ligands for highly selective purification of human plasma-related proteins from multiple sources

Nucleic acid aptamers are promising ligands for analytical and preparative-scale affinity chromatography applications. However, a full industrial exploitation requires that aptamer-grafted chromatography media provide a number of high technical standards that remained largely untested. Ideally, they should exhibit relatively high binding capacity associated to a very high degree of specificity. In addition, they must be highly resistant to harsh cleaning/sanitization conditions, as well as to prolonged and repeated exposure to biological environment. Here, we present practical examples of aptamer affinity chromatography for the purification of three human therapeutic proteins from various sources: Factor VII, Factor H and Factor IX. In a single chromatographic step, three DNA aptamer ligands enabled the efficient purification of their target protein, with an unprecedented degree of selectivity (from 0.5% to 98% of purity in one step). Furthermore, these aptamers demonstrated a high stability under harsh sanitization conditions (100h soaking in 1M NaOH). These results pave the way toward a wider adoption of aptamer-based affinity ligands in the industrial-scale purification of not only plasma-derived proteins but also of any other protein in general.

Affinity chromatography: A versatile technique for antibody purification

Antibodies continue to be extremely utilized entities in myriad applications including basic research, imaging, targeted delivery, chromatography, diagnostics, and therapeutics. At production stage, antibodies are generally present in complex matrices and most of their intended applications necessitate purification. Antibody purification has always been a major bottleneck in downstream processing of antibodies, due to the need of high quality products and associated high costs. Over the years, extensive research has focused on finding better purification methodologies to overcome this holdup. Among a plethora of different techniques, affinity chromatography is one of the most selective, rapid and easy method for antibody purification. This review aims to provide a detailed overview on affinity chromatography and the components involved in purification. An array of support matrices along with various classes of affinity ligands detailing their underlying working principles, together with the advantages and limitations of each system in purifying different types of antibodies, accompanying recent developments and important practical methodological considerations to optimize purification procedure are discussed.

Mixed-bed affinity chromatography: principles and methods

Mixed-bed chromatography is far from being a well-established technology within the panoply of bioseparation tools. Composed of an assembly of distinct sorbents that are mixed in a single bed, they have been mostly developed in the last decade for the reduction of dynamic concentration range where they allowed discovering many low-copy proteins within very complex proteomes. Other interesting preparative applications of mixed-bed chromatography have since been developed. In this chapter the basic concepts first and then detailed application recipes are described for (1) the reduction of protein dynamic concentration range, (2) the removal of impurity traces at the last stage of a biopurification process, and (3) the selection and use of sorbents as mixed bed in protein purification.

Calcium-sensitive immunoaffinity chromatography: Gentle and highly specific retrieval of a scarce plasma antigen, collectin-LK (CL-LK)

Immunoaffinity chromatography is a powerful fractionation technique that has become indispensable for protein purification and characterization. However, it is difficult to retrieve bound proteins without using harsh or denaturing elution conditions, and the purification of scarce antigens to homogeneity may be impossible due to contamination with abundant antigens. In this study, we purified the scarce, complement-associated plasma protein complex, collectin LK (CL-LK, complex of collectin liver 1 and kidney 1), by immunoaffinity chromatography using a calcium-sensitive anti-collectin-kidney-1 mAb. This antibody was characterized by binding to CL-LK at hypo- and physiological calcium concentrations and dissociated from CK-LK at hyperphysiological concentrations of calcium. We purified CL-LK from plasma to a purity of 41% and a yield of 38%, resulting in a purification factor of more than 88,000 in a single step. To evaluate the efficiency of this new purification scheme, we purified CL-LK using the same calcium-sensitive mAb in combination with acidic elution buffer and by using calcium-dependent anti-CL-K1 mAbs in combination with EDTA elution buffer. We found that calcium-sensitive immunoaffinity chromatography was superior to the traditional immunoaffinity chromatographies and resulted in a nine-fold improvement of the purification factor. The technique is applicable for the purification of proteins in complex mixtures by single-step fractionation without the denaturation of eluted antigens, and it allows for the purification of scarce proteins that would have otherwise been impossible to purify and, hence, to characterize. This technique may also potentially be applied for the purification of proteins that only interact with calcium ions at hyperphysiological concentrations.

Design, synthesis and evaluation of pyridine-based chromatographic adsorbents for antibody purification

The structure-based design and synthesis of four series of adsorbents for antibody purification by affinity chromatography has been investigated. The structures of 10 ligands were based on pyridine compounds that possessed thioalkyl substituents containing a primary amine, which was required for immobilisation of the ligands onto an epoxy-activated matrix (epoxy-Sepharose Fast Flow(®)). These new adsorbents were screened in monoclonal antibody binding assays in order to determine optimal buffer conditions for capture and elution under static and dynamic adsorption conditions. From batch binding measurements, the binding affinities, KD's, were found to be in the range of 3-5μM and the maximum capacities, qm's were between 12 and 30mgmAb/mL resin, depending on the substitution pattern of the thioalkylamine in the N-heterocyclic ring structure of the ligands. The amount of monoclonal antibody bound and eluted under overload conditions was influenced by the concentration of the sample loaded, the flow rate at which the sample was applied and the loading/volume. Further, the ability of these new adsorbents to selectively capture monoclonal antibodies of the class IgG1 from supernatants derived from genetically engineered CHO cells cultured in chemically defined media was investigated, documenting efficient capture and recovery of the mAb.