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Li Y, Yang HS, Klasse PJ, Zhao Z. The significance of antigen-antibody-binding avidity in clinical diagnosis. Crit Rev Clin Lab Sci 2024:1-15. [PMID: 39041650 DOI: 10.1080/10408363.2024.2379286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Accepted: 07/09/2024] [Indexed: 07/24/2024]
Abstract
Immunoglobulin G (IgG) and immunoglobulin M (IgM) testing are commonly used to determine infection status. Typically, the detection of IgM indicates an acute or recent infection, while the presence of IgG alone suggests a chronic or past infection. However, relying solely on IgG and IgM antibody positivity may not be sufficient to differentiate acute from chronic infections. This limitation arises from several factors. The prolonged presence of IgM can complicate diagnostic interpretations, and false positive IgM results often arise from antibody cross-reactivity with various antigens. Additionally, IgM may remain undetectable in prematurely collected samples or in individuals who are immunocompromised, further complicating accurate diagnosis. As a result, additional diagnostic tools are required to confirm infection status. Avidity is a measure of the strength of the binding between an antigen and antibody. Avidity-based assays have been developed for various infectious agents, including toxoplasma, cytomegalovirus (CMV), SARS-CoV-2, and avian influenza, and are promising tools in clinical diagnostics. By measuring the strength of antibody binding, they offer critical insights into the maturity of the immune response. These assays are instrumental in distinguishing between acute and chronic or past infections, monitoring disease progression, and guiding treatment decisions. The development of automated platforms has optimized the testing process by enhancing efficiency and minimizing the risk of manual errors. Additionally, the recent advent of real-time biosensor immunoassays, including the label-free immunoassays (LFIA), has further amplified the capabilities of these assays. These advances have expanded the clinical applications of avidity-based assays, making them useful tools for the diagnosis and management of various infectious diseases. This review is structured around several key aspects of IgG avidity in clinical diagnosis, including: (i) a detailed exposition of the IgG affinity maturation process; (ii) a thorough discussion of the IgG avidity assays, including the recently emerged biosensor-based approaches; and (iii) an examination of the applications of IgG avidity in clinical diagnosis. This review is intended to contribute toward the development of enhanced diagnostic tools through critical assessment of the present landscape of avidity-based testing, which allows us to identify the existing knowledge gaps and highlight areas for future investigation.
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Affiliation(s)
- Yaxin Li
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, USA
| | - He S Yang
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, USA
| | - P J Klasse
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA
| | - Zhen Zhao
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, USA
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Fischer J, Kaufmann JO, Weller MG. Simple Determination of Affinity Constants of Antibodies by Competitive Immunoassays. Methods Protoc 2024; 7:49. [PMID: 38921828 PMCID: PMC11206456 DOI: 10.3390/mps7030049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 06/06/2024] [Accepted: 06/07/2024] [Indexed: 06/27/2024] Open
Abstract
The affinity constant, also known as the equilibrium constant, binding constant, equilibrium association constant, or the reciprocal value, the equilibrium dissociation constant (Kd), can be considered as one of the most important characteristics for any antibody-antigen pair. Many methods based on different technologies have been proposed and used to determine this value. However, since a very large number of publications and commercial datasheets do not include this information, significant obstacles in performing such measurements seem to exist. In other cases where such data are reported, the results have often proved to be unreliable. This situation may indicate that most of the technologies available today require a high level of expertise and effort that does not seem to be available in many laboratories. In this paper, we present a simple approach based on standard immunoassay technology that is easy and quick to perform. It relies on the effect that the molar IC50 approaches the Kd value in the case of infinitely small concentrations of the reagent concentrations. A two-dimensional dilution of the reagents leads to an asymptotic convergence to Kd. The approach has some similarity to the well-known checkerboard titration used for the optimization of immunoassays. A well-known antibody against the FLAG peptide, clone M2, was used as a model system and the results were compared with other methods. This approach could be used in any case where a competitive assay is available or can be developed. The determination of an affinity constant should belong to the crucial parameters in any quality control of antibody-related products and assays and should be mandatory in papers using immunochemical protocols.
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Affiliation(s)
- Janina Fischer
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Strasse 11, 12489 Berlin, Germany
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Jan Ole Kaufmann
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Strasse 11, 12489 Berlin, Germany
- Charité—Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Michael G. Weller
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Strasse 11, 12489 Berlin, Germany
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
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Affinity of anti-spike antibodies to three major SARS-CoV-2 variants in recipients of three major vaccines. COMMUNICATIONS MEDICINE 2022; 2:109. [PMID: 36034646 PMCID: PMC9403978 DOI: 10.1038/s43856-022-00174-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 08/15/2022] [Indexed: 12/29/2022] Open
Abstract
Background Measuring anti-viral antibody affinity in blood plasma or serum is a rational quantitative approach to assess humoral immune response and acquired protection. Three common vaccines against SARS-CoV-2—Comirnaty developed by Pfizer/BioNTech, Spikevax developed by Moderna/NIAID, and Jcovden (previously Janssen COVID-19 Vaccine) developed by Johnson & Johnson/Janssen (J&J)—induce antibodies to a variety of immunogenic epitopes including the epitopes located in the ACE2 receptor-binding domain (RBD) of the spike protein. Blocking RBD with antibodies interferes with the binding of the virus to ACE2 thus protecting against infection. Methods We perform measurements in the serum of the recipients of Pfizer, Moderna, and J&J vaccines, and we compare the apparent affinities of vaccine-induced antibodies against the RBD of the ancestral SARS-CoV-2 virus and the Delta and Omicron variants. We use our recently published method to determine the apparent affinity of anti-spike protein antibodies directly in human serum. This involves probing antibody-antigen equilibria with a small number of antigen-coated magnetic microparticles and imaging them on a fluorescence microscope. Results Recipients of two-dose Pfizer and Moderna vaccines, as well as recipients of the single-dose J&J vaccine, develop high-affinity antibodies toward RBD derived from ancestral SARS-CoV-2. Affinities of these antibodies to Delta-RBD are approximately 10 times weaker, and even more drastically reduced (∼1000-fold) toward Omicron-RBD. Conclusions Vaccine-induced antibodies against ancestral SARS-CoV-2 RBD demonstrate ~10-fold and ~1000-fold weaker affinities toward Delta- and Omicron-RBD, respectively. Our approach offers a direct means for evaluating vaccine-induced adaptive immunity and can be helpful in designing or updating vaccines. Vaccination results in the production of proteins called antibodies that can bind viruses. The strength (affinity) of the binding between an antibody and a virus gives an indication of how well vaccination can prevent infection by the virus. Here, we compare the affinity of antibodies towards different types (variants) of SARS-CoV-2 viral protein in the serum of individuals who have been vaccinated with vaccines produced by Pfizer (Comirnaty), Moderna (Spikevax), and Johnson & Johnson (Jcovden). We discovered that all three vaccines generated antibodies that strongly bind the original SARS-CoV-2 virus, but the binding of the Delta variant was ten-times weaker. Moreover, the binding of the antibodies to the Omicron variant was more than a thousand-times weaker. Our findings explain why current vaccines are less efficient at preventing infection by the Delta and Omicron SARS-CoV-2 variants. Macdonald, Schaub et al. measure apparent antibody affinities to the ACE-2 receptor binding domain of the SARS-CoV-2 spike protein in recipients of the Pfizer, Moderna and J&J vaccines. All vaccinated individuals develop high-affinity antibodies, however the affinities are weaker to Delta and Omicron variants compared to ancestral virus.
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Linnik J, Syedbasha M, Hollenstein Y, Halter J, Egli A, Stelling J. Model-based inference of neutralizing antibody avidities against influenza virus. PLoS Pathog 2022; 18:e1010243. [PMID: 35100312 PMCID: PMC8830794 DOI: 10.1371/journal.ppat.1010243] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 02/10/2022] [Accepted: 01/03/2022] [Indexed: 11/23/2022] Open
Abstract
To assess the response to vaccination, quantity (concentration) and quality (avidity) of neutralizing antibodies are the most important parameters. Specifically, an increase in avidity indicates germinal center formation, which is required for establishing long-term protection. For influenza, the classical hemagglutination inhibition (HI) assay, however, quantifies a combination of both, and to separately determine avidity requires high experimental effort. We developed from first principles a biophysical model of hemagglutination inhibition to infer IgG antibody avidities from measured HI titers and IgG concentrations. The model accurately describes the relationship between neutralizing antibody concentration/avidity and HI titer, and explains quantitative aspects of the HI assay, such as robustness to pipetting errors and detection limit. We applied our model to infer avidities against the pandemic 2009 H1N1 influenza virus in vaccinated patients (n = 45) after hematopoietic stem cell transplantation (HSCT) and validated our results with independent avidity measurements using an enzyme-linked immunosorbent assay with urea elution. Avidities inferred by the model correlated with experimentally determined avidities (ρ = 0.54, 95% CI = [0.31, 0.70], P < 10−4). The model predicted that increases in IgG concentration mainly contribute to the observed HI titer increases in HSCT patients and that immunosuppressive treatment is associated with lower baseline avidities. Since our approach requires only easy-to-establish measurements as input, we anticipate that it will help to disentangle causes for poor vaccination outcomes also in larger patient populations. This study demonstrates that biophysical modelling can provide quantitative insights into agglutination assays and complement experimental measurements to refine antibody response analyses. Influenza vaccines are assessed based on the induced antibody response, where antibody quantity (concentration) and antibody binding strength (avidity) determine the potency to neutralize the virus. In addition, an increase in avidity indicates a successful germinal center reaction, which is required for establishing long-term protection. However, the hemagglutination inhibition (HI) assay—traditionally used to assess influenza vaccines—measures a combination of both antibody concentration and avidity, and to separately determine avidity requires high experimental effort. We developed a biophysical model of the HI assay, which enables the inference of antibody avidities from measured HI titers and antibody concentrations. We applied our approach to a vaccinated population of immunocompromised patients after blood stem cell transplantation and validated our results experimentally. The model predicted that vaccination induced an increase in avidity in only a few patients and that patients under immunosuppressive treatment show lower baseline avidities. Since our approach requires only easily measurable data as input, it can facilitate the investigation of vaccine responses in larger populations. This study demonstrates that biophysical modelling can complement experimental data and provide additional details on agglutination experiments and antibody responses.
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Affiliation(s)
- Janina Linnik
- Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
- Swiss Institute for Bioinformatics, Basel, Switzerland
| | | | | | - Jörg Halter
- Division of Hematology, University Hospital Basel, Basel, Switzerland
| | - Adrian Egli
- Department of Biomedicine, University of Basel, Basel, Switzerland
- Division of Clinical Bacteriology and Mycology, University Hospital Basel, Basel, Switzerland
- * E-mail: (AE); (JS)
| | - Jörg Stelling
- Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
- Swiss Institute for Bioinformatics, Basel, Switzerland
- * E-mail: (AE); (JS)
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Affinity of anti-spike antibodies in SARS-CoV-2 patient plasma and its effect on COVID-19 antibody assays. EBioMedicine 2021; 75:103796. [PMID: 34971970 PMCID: PMC8714467 DOI: 10.1016/j.ebiom.2021.103796] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 12/15/2021] [Accepted: 12/16/2021] [Indexed: 12/23/2022] Open
Abstract
Background Measuring anti-spike protein antibodies in human plasma or serum is commonly used to determine prior exposure to SARS-CoV-2 infection and to assess the anti-viral protection capacity. According to the mass-action law, a lesser concentration of tightly binding antibody can produce the same quantity of antibody-antigen complexes as higher concentrations of lower affinity antibody. Thus, measurements of antibody levels reflect both affinity and concentration. These two fundamental parameters cannot be disentangled in clinical immunoassays, and so produce a bias which depends on the assay format. Methods To determine the apparent affinity of anti-spike protein antibodies, a small number of antigen-coated magnetic microparticles were imaged by fluorescence microscopy after probing antigen-antibody equilibria directly in patient plasma. Direct and indirect anti-SARS-CoV-2 immunoassays were used to measure antibody levels in the blood of infected and immunised individuals. Findings We observed affinity maturation of antibodies in convalescent and vaccinated individuals, showing that higher affinities are achieved much faster by vaccination. We demonstrate that direct and indirect immunoassays for measuring anti-spike protein antibodies depend differently on antibody affinity which, in turn, affects accurate interpretation of the results. Interpretation Direct immunoassays show substantial antibody affinity dependence. This makes them useful for identifying past SARS-CoV-2 exposure. Indirect immunoassays provide more accurate quantifications of anti-viral antibody levels. Funding The authors are all full-time employees of Abbott Laboratories. Abbott Laboratories provided all operating funds. No external funding sources were used in this study.
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Toraño A, Moreno I, Infantes JA, Domínguez M. Development of a competitive inhibition kinetic ELISA to determine the inhibition constant (K i) of monoclonal antibodies. J Immunol Methods 2021; 493:113042. [PMID: 33757841 DOI: 10.1016/j.jim.2021.113042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 03/15/2021] [Accepted: 03/16/2021] [Indexed: 10/21/2022]
Abstract
Antibody-antigen interactions are mediated by the same molecular recognition mechanisms as those of an enzyme and its substrate. On this basis, we developed a competitive inhibition kinetic ELISA to measure monoclonal antibody (mAb) inhibition constants. Serially diluted samples of ligand (mAb) and inhibitor (soluble antigen) were incubated to equilibrium in ELISA plates coated with a fixed concentration of antigen (receptor). Plates were washed, and bound mAb measured with antiglobulin-peroxidase. Initial velocity data of receptor-bound mAb at various ligand and inhibitor concentrations were analyzed with enzyme linear competitive inhibition methods by non-linear regression (NLR), linear transformations (Cornish-Bowden, Lineweaver-Burk, Hanes-Woolf, Dixon, Cortés [1/i0.5 vs. Vi/Vmax], Ascenzi [Ks/Vmax/Ks,0/Vmax vs. [I]]) and NLR IC50 plots, to derive mAb inhibition constants (Ki). We obtained similar mAb Ki and Kd values by ELISA and surface plasmon resonance, which confirmed the accuracy of the ELISA method. This competitive inhibition ELISA is a simple (it requires no labeling or prior knowledge of antibody concentration), sensitive (it detects Ki values in the low nanomolar range by conventional colorimetry), and reproducible method with which to calculate mAb inhibition constants.
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Affiliation(s)
- Alfredo Toraño
- Unidad de Inmunología Microbiana, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid 28220, Spain.
| | - Inmaculada Moreno
- Unidad de Inmunología Microbiana, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid 28220, Spain
| | - José Antonio Infantes
- Unidad de Inmunología Microbiana, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid 28220, Spain
| | - Mercedes Domínguez
- Unidad de Inmunología Microbiana, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid 28220, Spain
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Samokhvalov AV, Safenkova IV, Eremin SA, Zherdev AV, Dzantiev BB. Measurement of (Aptamer–Small Target) KD Using the Competition between Fluorescently Labeled and Unlabeled Targets and the Detection of Fluorescence Anisotropy. Anal Chem 2018; 90:9189-9198. [DOI: 10.1021/acs.analchem.8b01699] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Alexey V. Samokhvalov
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
| | - Irina V. Safenkova
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
| | - Sergei A. Eremin
- Faculty of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991, Russia
| | - Anatoly V. Zherdev
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
| | - Boris B. Dzantiev
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow 119071, Russia
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A rapid solution-based method for determining the affinity of heroin hapten-induced antibodies to heroin, its metabolites, and other opioids. Anal Bioanal Chem 2018; 410:3885-3903. [PMID: 29675707 PMCID: PMC5956019 DOI: 10.1007/s00216-018-1060-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 03/27/2018] [Accepted: 04/03/2018] [Indexed: 11/15/2022]
Abstract
We describe for the first time a method that utilizes microscale thermophoresis (MST) technology to determine polyclonal antibody affinities to small molecules. Using a novel type of heterologous MST, we have accurately measured a solution-based binding affinity of serum antibodies to heroin which was previously impossible with other currently available methods. Moreover, this mismatch approach (i.e., using a cross-reactive hapten tracer) has never been reported in the literature. When compared with equilibrium dialysis combined with ultra-performance liquid chromatography/tandem mass spectrometry (ED-UPLC/MS/MS), this novel MST method yields similar binding affinity values for polyclonal antibodies to the major heroin metabolites 6-AM and morphine. Additionally, we herein report the method of synthesis of this novel cross-reactive hapten, MorHap-acetamide—a useful analog for the study of heroin hapten–antibody interactions. Using heterologous MST, we were able to determine the affinities, down to nanomolar accuracies, of polyclonal antibodies to various abused opioids. While optimizing this method, we further discovered that heroin is protected from serum esterase degradation by the presence of these antibodies in a concentration-dependent manner. Lastly, using affinity data for a number of structurally different opioids, we were able to dissect the moieties that are crucial to antibody binding. The novel MST method that is presented herein can be extended to the analysis of any ligand that is prone to degradation and can be applied not only to the development of vaccines to substances of abuse but also to the analysis of small molecule/protein interactions in the presence of serum. Strategy for the determination of hapten-induced antibody affinities using Microscale thermophoresis ![]()
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Addi C, Murschel F, De Crescenzo G. Design and Use of Chimeric Proteins Containing a Collagen-Binding Domain for Wound Healing and Bone Regeneration. TISSUE ENGINEERING PART B-REVIEWS 2016; 23:163-182. [PMID: 27824290 DOI: 10.1089/ten.teb.2016.0280] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Collagen-based biomaterials are widely used in the field of tissue engineering; they can be loaded with biomolecules such as growth factors (GFs) to modulate the biological response of the host and thus improve its potential for regeneration. Recombinant chimeric GFs fused to a collagen-binding domain (CBD) have been reported to improve their bioavailability and the host response, especially when combined with an appropriate collagen-based biomaterial. This review first provides an extensive description of the various CBDs that have been fused to proteins, with a focus on the need for accurate characterization of their interaction with collagen. The second part of the review highlights the benefits of various CBD/GF fusion proteins that have been designed for wound healing and bone regeneration.
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Affiliation(s)
- Cyril Addi
- Biomedical Science and Technology Research Group, Bio-P2 Research Unit , Department of Chemical Engineering, École Polytechnique de Montréal, Montréal, Canada
| | - Frederic Murschel
- Biomedical Science and Technology Research Group, Bio-P2 Research Unit , Department of Chemical Engineering, École Polytechnique de Montréal, Montréal, Canada
| | - Gregory De Crescenzo
- Biomedical Science and Technology Research Group, Bio-P2 Research Unit , Department of Chemical Engineering, École Polytechnique de Montréal, Montréal, Canada
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10
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Klasse PJ. How to assess the binding strength of antibodies elicited by vaccination against HIV and other viruses. Expert Rev Vaccines 2016; 15:295-311. [PMID: 26641943 DOI: 10.1586/14760584.2016.1128831] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Vaccines that protect against viral infections generally induce neutralizing antibodies. When vaccines are evaluated, the need arises to assess the affinity maturation of the antibody responses. Binding titers of polyclonal sera depend not only on the affinities of the constituent antibodies but also on their individual concentrations, which are difficult to ascertain. Therefore an assay based on chaotrope disruption of antibody-antigen complexes was designed for measuring binding strength. This assay works well with many viral antigens but gives differential results depending on the conformational dependence of epitopes on complex antigens such as the envelope glycoprotein of HIV-1. Kinetic binding assays might offer alternatives, since they can measure average off-rate constants for polyclonal antibodies in a serum. Here, potentials and fallacies of these techniques are discussed.
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Affiliation(s)
- P J Klasse
- a Department of Microbiology and Immunology, Weill Cornell Medical College , Cornell University , New York , NY , USA
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11
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What Do Chaotrope-Based Avidity Assays for Antibodies to HIV-1 Envelope Glycoproteins Measure? J Virol 2015; 89:5981-95. [PMID: 25810537 DOI: 10.1128/jvi.00320-15] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 03/16/2015] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED When HIV-1 vaccine candidates that include soluble envelope glycoproteins (Env) are tested in humans and other species, the resulting antibody responses to Env are sifted for correlates of protection or risk. One frequently used assay measures the reduction in antibody binding to Env antigens by an added chaotrope (such as thiocyanate). Based on that assay, an avidity index was devised for assessing the affinity maturation of antibodies of unknown concentration in polyclonal sera. Since a high avidity index was linked to protection in animal models of HIV-1 infection, it has become a criterion for evaluating antibody responses to vaccine candidates. But what does the assay measure and what does an avidity index mean? Here, we have used a panel of monoclonal antibodies to well-defined epitopes on Env (gp120, gp41, and SOSIP.664 trimers) to explore how the chaotrope acts. We conclude that the chaotrope sensitivity of antibody binding to Env depends on several properties of the epitopes (continuity versus tertiary- and quaternary-structural dependence) and that the avidity index has no simple relationship to antibody affinity for functional Env spikes on virions. We show that the binding of broadly neutralizing antibodies against quaternary-structural epitopes is particularly sensitive to chaotrope treatment, whereas antibody binding to epitopes in variable loops and to nonneutralization epitopes in gp41 is generally resistant. As a result of such biases, the avidity index may at best be a mere surrogate for undefined antibody or other immune responses that correlate weakly with protection. IMPORTANCE An effective HIV-1 vaccine is an important goal. Such a vaccine will probably need to induce antibodies that neutralize typically transmitted variants of HIV-1, preventing them from infecting target cells. Vaccine candidates have so far failed to induce such antibody responses, although some do protect weakly against infection in animals and, possibly, humans. In the search for responses associated with protection, an avidity assay based on chemical disruption is often used to measure the strength of antibody binding. We have analyzed this assay mechanistically and found that the epitope specificity of an antibody has a greater influence on the outcome than does its affinity. As a result, the avidity assay is biased toward the detection of some antibody specificities while disfavoring others. We conclude that the assay may yield merely indirect correlations with weak protection, specifically when Env vaccination has failed to induce broad neutralizing responses.
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Kuhne M, Dippong M, Flemig S, Hoffmann K, Petsch K, Schenk JA, Kunte HJ, Schneider RJ. Comparative characterization of mAb producing hapten-specific hybridoma cells by flow cytometric analysis and ELISA. J Immunol Methods 2014; 413:45-56. [DOI: 10.1016/j.jim.2014.07.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 07/13/2014] [Accepted: 07/14/2014] [Indexed: 01/20/2023]
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13
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Torres OB, Jalah R, Rice KC, Li F, Antoline JFG, Iyer MR, Jacobson AE, Boutaghou MN, Alving CR, Matyas GR. Characterization and optimization of heroin hapten-BSA conjugates: method development for the synthesis of reproducible hapten-based vaccines. Anal Bioanal Chem 2014; 406:5927-37. [PMID: 25084736 PMCID: PMC4156789 DOI: 10.1007/s00216-014-8035-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/07/2014] [Accepted: 07/14/2014] [Indexed: 01/20/2023]
Abstract
A potential new treatment for drug addiction is immunization with vaccines that induce antibodies that can abrogate the addictive effects of the drug of abuse. One of the challenges in the development of a vaccine against drugs of abuse is the availability of an optimum procedure that gives reproducible and high yielding hapten-protein conjugates. In this study, a heroin/morphine surrogate hapten (MorHap) was coupled to bovine serum albumin (BSA) using maleimide-thiol chemistry. MorHap-BSA conjugates with 3, 5, 10, 15, 22, 28, and 34 haptens were obtained using different linker and hapten ratios. Using this optimized procedure, MorHap-BSA conjugates were synthesized with highly reproducible results and in high yields. The number of haptens attached to BSA was compared by 2,4,6-trinitrobenzenesulfonic acid (TNBS) assay, modified Ellman's test and matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Among the three methods, MALDI-TOF MS discriminated subtle differences in hapten density. The effect of hapten density on enzyme-linked immunosorbent assay (ELISA) performance was evaluated with seven MorHap-BSA conjugates of varying hapten densities, which were used as coating antigens. The highest antibody binding was obtained with MorHap-BSA conjugates containing 3-5 haptens. This is the first report that rigorously analyzes, optimizes and characterizes the conjugation of haptens to proteins that can be used for vaccines against drugs of abuse. The effect of hapten density on the ELISA detection of antibodies against haptens demonstrates the importance of careful characterization of the hapten density by the analytical techniques described.
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Affiliation(s)
- Oscar B. Torres
- Laboratory of Adjuvant and Antigen Research, US Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910 USA
- US Military HIV Research Program, Henry M. Jackson Foundation for the Advancement of Military Medicine, 6720A Rockledge Drive, Bethesda, MD 20817 USA
| | - Rashmi Jalah
- Laboratory of Adjuvant and Antigen Research, US Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910 USA
- US Military HIV Research Program, Henry M. Jackson Foundation for the Advancement of Military Medicine, 6720A Rockledge Drive, Bethesda, MD 20817 USA
| | - Kenner C. Rice
- Department of Health and Human Services, Drug Design and Synthesis Section, Chemical Biology Research Branch, National Institute on Drug Abuse, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
| | - Fuying Li
- Department of Health and Human Services, Drug Design and Synthesis Section, Chemical Biology Research Branch, National Institute on Drug Abuse, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
| | - Joshua F. G. Antoline
- Department of Health and Human Services, Drug Design and Synthesis Section, Chemical Biology Research Branch, National Institute on Drug Abuse, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
| | - Malliga R. Iyer
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
| | - Arthur E. Jacobson
- Department of Health and Human Services, Drug Design and Synthesis Section, Chemical Biology Research Branch, National Institute on Drug Abuse, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 9800 Medical Drive, Bethesda, MD 20892-9415 USA
| | | | - Carl R. Alving
- Laboratory of Adjuvant and Antigen Research, US Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910 USA
| | - Gary R. Matyas
- Laboratory of Adjuvant and Antigen Research, US Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910 USA
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Day ES, Capili AD, Borysenko CW, Zafari M, Whitty A. Determining the affinity and stoichiometry of interactions between unmodified proteins in solution using Biacore. Anal Biochem 2013; 440:96-107. [PMID: 23711722 DOI: 10.1016/j.ab.2013.05.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 05/03/2013] [Accepted: 05/10/2013] [Indexed: 11/30/2022]
Abstract
We describe a general Biacore method for measuring equilibrium binding affinities and stoichiometries for interactions between unmodified proteins and their unmodified ligands free in solution. Mixtures of protein and ligand are preequilibrated at different ratios in solution and then analyzed by Biacore using a sensor chip surface that detects only unbound analyte. Performing the Biacore analysis under mass transport limited conditions allows the concentration of unbound analyte to be determined from the initial velocity of binding. Plots of initial velocity versus the concentration of the varied binding partner are fitted to a quadratic binding equation to give the affinity and stoichiometry of binding. We demonstrate the method using soluble Her2 extracellular domain binding to monovalent, bivalent, and trivalent forms of an anti-Her2 antibody. The affinity we measured agrees with that obtained from conventional Biacore kinetic analysis, and the stoichiometries for the resulting 1:1, 1:2, and 1:3 complexes were confirmed by gel filtration with in-line light scattering. The method is applicable over an affinity range of approximately 100 pM to 1 μM and is particularly useful when there is concern that covalently modifying one or the other binding partner might affect its binding properties or where multivalency might otherwise complicate a quantitative analysis of binding.
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15
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The impact of antibody/epitope affinity strength on the sensitivity of electrochemical immunosensors for detecting small molecules. Anal Bioanal Chem 2013; 405:3889-98. [PMID: 23440393 DOI: 10.1007/s00216-013-6782-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Revised: 01/01/2013] [Accepted: 01/23/2013] [Indexed: 10/27/2022]
Abstract
A displacement immunoassay involves having a labelled analogue of the analyte (the epitope) already bound to the antibody. The presence of the analyte causes a competition for antibodies, and some of the antibodies dissociates from the epitope so that it can bind with the analyte. Herein, the influence of the affinity of the surface-bound epitope for the antibody on the sensitivity and selectivity of a displacement immunosensor is explored both theoretically and experimentally. An electrochemical immunosensor described previously, where the dissociation of antibodies from an electrode surface causes an increase in current from surface-bound ferrocene species, is used for this purpose. As expected, the ease and effectiveness of the bound antibody being displaced is inversely related to the affinity of the antibody to the surface-bound epitope relative to the analyte in solution as expected. However, if the affinity constant is too low, selectivity and/or sensitivity are compromised. Experimental results are qualitatively compared with a simple mass-action model.
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16
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Identification and discrimination of snake venoms from Egyptian elapids. Toxicon 2012; 63:88-97. [PMID: 23220490 DOI: 10.1016/j.toxicon.2012.11.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2012] [Revised: 11/22/2012] [Accepted: 11/27/2012] [Indexed: 11/21/2022]
Abstract
The avidity to the corresponding antigens is often higher than to the cross-reactive antigens. This was demonstrated with the highly cross-reactive elapid Egyptian snake venoms Naja haje (Nh), Naja nigricollis (Nn) and Walterinnesia aegyptia (Wa), and used for the differentiation among the three species in a simple ELISA-based assay. A three-step immuno-affinity protocol was followed and the titer and avidity of the different antibody (Ab) preparations were assessed and evaluated. The advantages offered by the avidity power of the venom specific antibodies (VS-Abs) obtained after one step purification, outweigh the specificity of the species-specific antibodies (SS-Abs) obtained after further purification. The efficiency of the VS-Abs as special immunodiagnostics was validated using 16 venom samples collected from individual snakes of different size and age at different time intervals. The avidities of the VS-Abs to the homologous venoms were 2.53 ± 0.4, 2.66 ± 0.31 and 2.8 ± 0.06 for Nh, Nn and Wa venoms respectively; whereas the avidity of the same Abs to the heterologous venoms could hardly exceed 1. Venom concentrations in the range between 10-1250 ng/well were detected with almost the same efficiency, an extra advantage that could be added to the assay to assure equal sensitivity allover the mentioned venom concentration range.
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Editorial on the manuscript entitled “Impact of Troponin I-Autoantibodies in Chronic Dilated and Ischemic Cardiomyopathy” by Andreas O. Doesch and co-workers. Basic Res Cardiol 2010; 106:1-4. [DOI: 10.1007/s00395-010-0140-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 12/06/2010] [Indexed: 01/22/2023]
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18
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Herbst SM, Klegerman ME, Kim H, Qi J, Shelat H, Wassler M, Moody MR, Yang CM, Ge X, Zou Y, Kopechek JA, Clubb FJ, Kraemer DC, Huang S, Holland CK, McPherson DD, Geng YJ. Delivery of stem cells to porcine arterial wall with echogenic liposomes conjugated to antibodies against CD34 and intercellular adhesion molecule-1. Mol Pharm 2010; 7:3-11. [PMID: 19719324 DOI: 10.1021/mp900116r] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In atherosclerosis, the loss of vascular stem cells via apoptosis impairs the capacity of the vascular wall to repair or regenerate the tissue damaged by atherogenic factors. Recruitment of exogenous stem cells to the plaque tissue may repopulate vascular cells and help repair the arterial tissue. Ultrasound-enhanced liposomal targeting may provide a feasible method for stem cell delivery into atheroma. Bifunctional echogenic immunoliposomes (BF-ELIP) were generated by covalently coupling two antibodies to liposomes; the first one specific for CD34 antigens on the surface of stem cells and the second directed against the intercellular adhesion molecule-1 (ICAM-1) antigens on the inflammatory endothelium covering atheroma. CD34+ stem cells from adult bone marrow were incubated on the ICAM-1-expressing endothelium of the aorta of swine fed high cholesterol diets, which was preloaded with BF-ELIP. Significantly increased stem cell adherence and penetration were detected in particular in the aortic segments treated with 1 MHz low-amplitude continuous wave ultrasound. Fluorescence and scanning electron microscopy confirmed the presence of BF-ELIP-bound CD34+ cells in the intimal compartment of the atheromatous arterial wall. Ultrasound treatment increased the number of endothelial cell progenitors migrating into the intima. Thus, under ultrasound enhancement, BF-ELIP bound CD34+ stem cells selectively bind to the ICAM-1 expressing endothelium of atherosclerotic lesions.
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Affiliation(s)
- Stephanie M Herbst
- Division of Cardiology, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas, USA
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19
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Ablation of the complementarity-determining region H3 apex of the anti-HIV-1 broadly neutralizing antibody 2F5 abrogates neutralizing capacity without affecting core epitope binding. J Virol 2010; 84:4136-47. [PMID: 20147404 DOI: 10.1128/jvi.02357-09] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The identification and characterization of broadly neutralizing antibodies (bnAbs) against HIV-1 has formed a major research focus, with the ultimate goal to help in the design of an effective AIDS vaccine. One of these bnAbs, 2F5, has been extensively characterized, and residues at the apex of its unusually long complementarity-determining region (CDR) H3 loop have been shown to be crucial for neutralization. Structural studies, however, have revealed that the (100)TLFGVPI(100F) apex residues of the CDR H3 loop do not interact directly with residues of its core gp41 epitope. In an attempt to gain better insight into the functional role of this element, we have recombinantly expressed native 2F5 Fab and two mutants in which either the apical Phe100B(H) residue was changed to an alanine or the CDR H3 residues (100)TLFGVPI(100F) were replaced by a Ser-Gly dipeptide linker. Isothermal titration calorimetry (ITC) and competitive-binding enzyme-linked immunosorbent assays (ELISAs) rendered strikingly similar affinity constants (K(d) [dissociation constant] of approximately 20 nM) for linear peptide epitope binding by 2F5 Fabs, independent of the presence or absence of the apex residues. Ablation of the CDR H3 apex residues, however, abolished the cell-cell fusion inhibition and pseudovirus neutralization capacities of 2F5 Fab. We report competitive ELISA data that suggest a role of 2F5 CDR H3 apex residues in mediating weak hydrophobic interactions with residues located at the C terminus of the gp41 membrane proximal external region and/or membrane components in the context of core epitope binding. The present data therefore imply an extended 2F5 paratope that includes weak secondary interactions that are crucial for neutralization of Env-mediated fusion.
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Klegerman ME, Wassler M, Huang SL, Zou Y, Kim H, Shelat HS, Holland CK, Geng YJ, McPherson DD. Liposomal modular complexes for simultaneous targeted delivery of bioactive gases and therapeutics. J Control Release 2009; 142:326-31. [PMID: 19903503 DOI: 10.1016/j.jconrel.2009.10.037] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 10/20/2009] [Accepted: 10/31/2009] [Indexed: 11/26/2022]
Abstract
Intrinsically echogenic liposomes (ELIP) can be adapted to encapsulate nitric oxide to facilitate ultrasound-enhanced delivery of therapeutic agents to atherosclerotic plaques. However, the NO loading of targeted ELIP caused a 93% decrease of antibody (Ab) immunoreactivity. The following hypothesis was tested: biotin/avidin-mediated coupling of NO-ELIP and Ab-conjugated ELIP will enable co-delivery of bioactive gases and ELIP that can encapsulate other agents without loss of targeting efficiency. Complex formation was initiated by addition of excess streptavidin to equal proportions of biotinylated Ab-ELIP and NO-ELIP. Fluorescence deconvolution microscopy, Coulter Multisizer 3 analysis and flow cytometry demonstrated that the ELIP coupling procedure formed mixed aggregates of >or=10 liposomes within 1 min. Intravascular ultrasound imaging and ELISA showed that echogenicity and targeting efficiency were completely and 69-99% retained, respectively. When complexed to NO-ELIP, ELIP bifunctionally targeted to both CD34 and ICAM-1 (BF-ELIP) increased human mononuclear cell migration through human coronary artery endothelial cell monolayers in transwell plates 4-fold relative to a nonspecific IgG-ELIP control and 2-fold relative to BF-ELIP alone. It was concluded that this novel multi-functional conjugation methodology provides a platform technology for site-specific co-delivery of bioactive gases and other agents.
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Affiliation(s)
- Melvin E Klegerman
- Division of Cardiology, Department of Internal Medicine, University of Texas Health Science Center, 6431 Fannin Street, MSB 1.246, Houston, Texas 77030, USA.
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21
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Klegerman ME, Huang S, Parikh D, Martinez J, Demos SM, Onyuksel HA, McPherson DD. Lipid contribution to the affinity of antigen association with specific antibodies conjugated to liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1703-16. [PMID: 17509522 PMCID: PMC2039706 DOI: 10.1016/j.bbamem.2007.04.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2006] [Revised: 02/09/2007] [Accepted: 04/09/2007] [Indexed: 10/23/2022]
Abstract
Immunoliposomes, directed to clinically relevant cell-surface molecules with antibodies, antibody fragments or peptides, are used for site-specific diagnostic evaluation or delivery of therapeutic agents. We have developed intrinsically echogenic liposomes (ELIP) covalently linked to fibrin(ogen)-specific antibodies and Fab fragments for ultrasonic imaging of atherosclerotic plaques. In order to determine the effect of liposomal conjugation on the molecular dynamics of fibrinogen binding, we studied the thermodynamic characteristics of unconjugated and ELIP-conjugated antibody molecules. Utilizing radioimmunoassay and enzyme-linked immunosorbent assay protocols, binding affinities were derived from data obtained at three temperatures. The thermodynamic functions DeltaH(o) , DeltaG(o) and DeltaS(o) were determined from van't Hoff plots and equations of state. The resultant functions indicated that both specific and nonspecific associations of antibody molecules with fibrinogen occurred through a variety of molecular interactions, including hydrophophic, ionic and hydrogen bonding mechanisms. ELIP conjugation of antibodies and Fab fragments introduced a characteristic change in both DeltaH(o) and DeltaS(o) of association, which corresponded to a variable contribution to binding by phospholipid gel-liquid crystal phase transitions. These observations suggest that a reciprocal energy transduction, affecting the strength of antibody-antigen binding, may be a singular characteristic of immunoliposomes, having utility for optimization and further development of the technology.
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Affiliation(s)
- Melvin E Klegerman
- Division of Cardiology, Department of Internal Medicine, University of Texas Health Science Center - Houston, 6431 Fannin Street, MSB 1.246, Houston, TX 77030, USA.
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22
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Analytical magnetic techniques in biology. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0075-7535(06)32008-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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23
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Zhang H, Williams PS, Zborowski M, Chalmers JJ. Binding affinities/avidities of antibody-antigen interactions: quantification and scale-up implications. Biotechnol Bioeng 2006; 95:812-29. [PMID: 16937410 DOI: 10.1002/bit.21024] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Bioaffinity interactions have been, and continue to be, successfully adapted from nature for use in separation and detection applications. It has been previously reported that the magnetophoretic mobility of labeled cells show a saturation type phenomenon as a function of the concentration of the free antibody-magnetic nanoparticle conjugate which is consistent with other reports of antibody-fluorophore binding. Starting with the standard antibody-antigen relationship, a model was developed which takes into consideration multi-valence interactions, and various attributes of flow cytometry (FCM) and cell tracking velocimetry (CTV) measurements to determine both the apparent dissociation constant and the antibody-binding capacity (ABC) of a cell. This model was then evaluated on peripheral blood lymphocytes (PBLs) labeled with anti CD3 antibodies conjugated to FITC, PE, or DM (magnetic nanoparticles). Reasonable agreements between the model and the experiments were obtained. In addition, estimates of the limitation of the number of magnetic nanoparticles that can bind to a cell as a result of steric hinderance was consistent with measured values of magnetophoretic mobility. Finally, a scale-up model was proposed and tested which predicts the amount of antibody conjugates needed to achieve a given level of saturation as the total number of cells reaches 10(10), the number of cells needed for certain clinical applications, such as T-cell depletions for mismatched bone marrow transplants.
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Affiliation(s)
- Huading Zhang
- Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 W 19th Ave., Columbus, Ohio 43210, USA
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24
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Skrabana R, Skrabanova-Khuebachova M, Kontsek P, Novak M. Alzheimer’s-disease-associated conformation of intrinsically disordered tau protein studied by intrinsically disordered protein liquid-phase competitive enzyme-linked immunosorbent assay. Anal Biochem 2006; 359:230-7. [PMID: 17081491 DOI: 10.1016/j.ab.2006.09.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2006] [Revised: 09/27/2006] [Accepted: 09/28/2006] [Indexed: 10/24/2022]
Abstract
Tau protein, the major constituent of paired helical filaments in Alzheimer's disease, belongs to the intrinsically disordered proteins (IDPs). IDPs are an emerging group in the protein kingdom characterized by the absence of a rigid three-dimensional structure. Disordered proteins usually acquire a "functional fold" upon binding to their interaction partner(s). This property of IDPs implies the need for innovative approaches to measure their binding affinity. We have mapped and measured the Alzheimer's-disease-associated epitope on intrinsically disordered tau protein with a novel two-step sandwich competitive enzyme-linked immunosorbent assay (ELISA). This approach allowed us to determine the binding affinity of disordered tau protein in liquid phase without any disturbance to the competitive equilibrium and without any need for covalent or noncovalent modification of tau protein. Furthermore, the global fitting method, used for the reconstruction of tau binding curves, significantly improved the assay readout. The proposed novel competitive ELISA allowed us to determine the changes in the standard Gibbs energy of binding, thus enabling measurement of tau protein conformation in the core of paired helical filaments. IDP competitive ELISA results showed, for the first time, that the tau protein C terminus of the Alzheimer's-disease-derived paired helical filaments core subunit adopts beta-turn type I' fold and is accessible from solution.
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Affiliation(s)
- Rostislav Skrabana
- Institute of Neuroimmunology, Slovak Academy of Sciences, Dubravska cesta 9, 845 10 Bratislava, Slovakia
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Dubois M, Delaunay V, Delestre L, Ezan E. Validation of an ELISA for determination of antibodies induced in monkeys against Epi-hNE4, a recombinant protein inhibitor of human neutrophil elastase. J Pharm Biomed Anal 2006; 43:1423-9. [PMID: 17118611 DOI: 10.1016/j.jpba.2006.10.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 10/09/2006] [Accepted: 10/17/2006] [Indexed: 10/23/2022]
Abstract
The engineered protein inhibitor of human neutrophil elastase, Epi-hNE4, is being developed for the treatment of cystic fibrosis. Like many recombinant proteins, Epi-hNE4 may induce antibodies in pre-clinical species and in humans. The aim of this report was to validate an ELISA to assess its immunogenicity in monkeys. We have designed and optimized a classical ELISA in which Epi-hNE4 was coated directly on microtitre plates and the antibodies were detected using a secondary antibody labelled with peroxidase. We report implementation of the recent recommendations proposed for the validation of immunogenicity assessment. The cut-off point was determined by means of statistical analysis of negative samples. Linearity, reproducibility, stability and specificity were estimated using quality control samples obtained from a pool of positive samples. The method was applied to monkeys given Epi-hNE4 by inhalation. A confirmation test and a neutralization assay were developed in order to further assess positive samples. In conclusion, we present here one of the first examples of validation in application of recent recommendations [A.R. Mire-Sluis, Y.C. Barrett, V. Devanarayan, E. Koren, H. Liu, M. Maia, T. Parish, G. Scott, G. Shankar, E. Shores, S.J. Swanson, G. Taniguchi, D. Wierda, L.A. Zuckerman, J. Immunol. Methods 289 (2004) 1-16].
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Affiliation(s)
- Mathieu Dubois
- CEA, Service de Pharmacologie et d'Immunologie, CE Saclay, 91191 Gif-sur Yvette, France
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26
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Uram JD, Mayer M. Estimation of solid phase affinity constants using resistive-pulses from functionalized nanoparticles. Biosens Bioelectron 2006; 22:1556-60. [PMID: 16889953 DOI: 10.1016/j.bios.2006.06.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 06/15/2006] [Accepted: 06/23/2006] [Indexed: 11/21/2022]
Abstract
This paper describes a method for estimating the solid phase affinity constant of antibodies by using resistive-pulse (Coulter counting) data from spherical nanoparticles that expose antigens. We developed this technique by analyzing data published recently by Saleh, O.A., Sohn, L.L., 2003a. Proc. Natl. Acad. Sci. U.S.A. 100, 820-824. These authors used resistive-pulse sensing to detect an increase in the diameter of streptavidin-functionalized colloids due to the binding of monoclonal anti-streptavidin antibodies. Based on further analysis of their data, we were able to determine the number of antibodies bound to the colloids at various antibody concentrations. This information made it possible to estimate the solid phase affinity constant of the interaction by fitting the data with binding isotherms that describe the binding equilibrium between antibody and antigen. We calculated a value of 2.6x10(8)+/-0.8x10(8) M-1 which is in agreement with the specifications of the supplier of the antibody.
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Affiliation(s)
- Jeffrey D Uram
- Department of Biomedical Engineering University of Michigan, Ann Arbor, MI 48109, USA
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27
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Lord MS, Cousins BG, Doherty PJ, Whitelock JM, Simmons A, Williams RL, Milthorpe BK. The effect of silica nanoparticulate coatings on serum protein adsorption and cellular response. Biomaterials 2006; 27:4856-62. [PMID: 16757021 DOI: 10.1016/j.biomaterials.2006.05.037] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Accepted: 05/24/2006] [Indexed: 01/16/2023]
Abstract
Serum protein adsorption on colloidal silica surfaces was investigated using a quartz crystal microbalance with dissipation (QCM-D) monitoring. The amount of serum proteins adsorbed on colloidal silica-coated surfaces was not significantly different from the control silica surfaces, with the exception of 21nm colloidal silica which experienced significantly less (P<0.05) fibrinogen adsorption compared with control silica. The adhesion and proliferation of human endothelial cells (C11STH) on nano-scale colloidal silica surfaces were significantly reduced compared with control silica surfaces, suggesting that the conformation of adsorbed proteins on the colloidal silica surfaces plays a role in modulating the amount of cell binding. Fibronectin is one of the main extracellular matrix proteins involved in endothelial cell attachment to biomaterial surfaces. There was reduced binding of a monoclonal anti-fibronectin antibody, that reacted specifically with the cell-binding fragment, to fibronectin-coated colloidal silica surfaces compared with control silica surfaces. This suggests that the fibronectin adsorbed on the colloidal silica-coated surfaces was conformationally changed compared with control silica reducing the availability of the cell-binding domain of fibronectin.
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Affiliation(s)
- M S Lord
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia
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28
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Abstract
Multivalent interactions play a critical role in a variety of biological processes on both molecular and cellular levels. We have used molecular force spectroscopy to investigate the strength of multiple parallel peptide-antibody bonds using a system that allowed us to determine the rupture forces and the number of ruptured bonds independently. In our experiments the interacting molecules were attached to the surfaces of the probe and sample of the atomic force microscope with flexible polymer tethers, and the unique mechanical signatures of the tethers determined the number of ruptured bonds. We show that the rupture forces increase with the number of interacting molecules and that the measured forces obey the predictions of a Markovian model for the strength of multiple parallel bonds. We also discuss the implications of our results to the interpretation of force spectroscopy measurements in multiple bond systems.
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Affiliation(s)
- Todd Sulchek
- Physical Biosciences Institute, Chemistry and Materials Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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Segelmark M, Hellmark T, Wieslander J. The prognostic significance in Goodpasture's disease of specificity, titre and affinity of anti-glomerular-basement-membrane antibodies. NEPHRON. CLINICAL PRACTICE 2003; 94:c59-68. [PMID: 12902632 DOI: 10.1159/000072022] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2002] [Accepted: 03/31/2003] [Indexed: 11/19/2022]
Abstract
BACKGROUND The nephrotoxic potential of anti-glomerular-basement-membrane (GBM) antibodies has been demonstrated in numerous animal experiments. However, it is not known to what extent the properties of circulating anti-GBM antibodies in human disease reflect the severity of the disease and predict the outcome. METHODS Clinical data were collected for 79 Swedish patients for whom a positive result had previously been obtained with anti-GBM ELISA. In stored sera from the patients, we measured antibody concentration, specificity and affinity together with antineutrophil cytoplasmic antibodies and alpha(1)-antitrypsin phenotype. RESULTS Six months after diagnosis, 27 (34%) were dead, 32 (41%) were on dialysis treatment and only 20 (25%) were alive with a functioning native kidney. The best predictor for renal survival was renal function at diagnosis. In patients who were not dialysis dependent at diagnosis however, renal survival was associated with a lower concentration of anti-GBM antibodies, a lower proportion of antibodies specific for the immunodominant epitope and the histological severity of the renal lesion. The only factor that correlated with patient survival was age. CONCLUSIONS Immunochemical properties of autoantibodies do not affect patient survival in anti-GBM disease but seem to be a factor in renal survival in patients detected before renal damage is too advanced.
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Helg A, Mueller MS, Joss A, Pöltl-Frank F, Stuart F, Robinson JA, Pluschke G. Comparison of analytical methods for the evaluation of antibody responses against epitopes of polymorphic protein antigens. J Immunol Methods 2003; 276:19-31. [PMID: 12738356 DOI: 10.1016/s0022-1759(03)00075-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Surface exposed protein antigens of the malaria parasite Plasmodium falciparum frequently harbor multiple dimorphic amino acid positions. These are associated with parasite immune evasion and represent a major obstacle for subunit vaccine design. Here, we have analyzed the flexibility of the humoral immune response against a semiconserved sequence (YX(44)LFX(47)KEKMX(52)L) of the key malaria blood stage vaccine candidate merozoite surface protein-1 (MSP-1). Monoclonal antibodies (mAbs) raised against one of the six described natural sequence variants of MSP-1(43-53) were analyzed for cross-reactivity with the other allelic forms, which differ in one to three positions from the immunizing sequence. Enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) spectroscopy demonstrated marked differences in mAb binding avidity to the variant sequences and isothermal titration calorimetry (ITC) provided evidence for a very low affinity of some of the interactions. In immunofluorescence analysis (IFA) and Western blotting analysis, the mAbs nevertheless stained all analyzed parasite clones expressing MSP-1(43-53) variant sequences. When used for the evaluation of humoral immune responses in clinical malaria vaccine trials, these two commonly used methods may thus not be suitable to distinguish biologically functional high affinity antibody responses from irrelevant low-affinity cross-reactivities.
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Affiliation(s)
- A Helg
- Swiss Tropical Institute, Socinstrasse 57, CH 4002, Basel, Switzerland
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31
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Sanny CG, Price JA. Analysis of antibody-antigen interactions in mixtures containing reactive and nonreactive components using size-exclusion high-performance (pressure) liquid chromatography. Anal Biochem 2001; 295:57-65. [PMID: 11476545 DOI: 10.1006/abio.2001.5204] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Analysis of antibody-antigen interactions using size-exclusion high-performance (pressure) liquid chromatography was applied to a polyvalent system composed of both reactive and nonreactive components. Mixtures containing varying concentrations of antivenin (Crotalidae) polyvalent (equine origin) and either Crotalus atrox (Western diamondback rattlesnake) venom (CV) or isolated C. atrox phospholipase A2 (PLA2) were separated using a Bio-Sil SEC 250-5 size-exclusion column (300 x 7.8 mm). Major regions containing high-molecular-weight aggregates, antivenin IgG, and CV components or PLA2 could be identified from the elution profiles. Changes in elution profile areas could be modeled by equations derived from the law of mass action that included values for the maximum fraction of reactivity, antigen valence, apparent binding constants, profile area proportionality constants, and nonreactive profile area. The analysis was simple, fast, and readily interpretable and may be applicable to a variety of situations in which stable antigen-antibody complexes are formed in the presence of nonreactive components.
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Affiliation(s)
- C G Sanny
- Oklahoma State University College of Osteopathic Medicine, 1111 West 17th Street, Tulsa, Oklahoma 74107, USA
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Jethwa HS, Clarke SH, Itoh-Lindstrom Y, Falk RJ, Jennette JC, Nachman PH. Restriction in V kappa gene use and antigen selection in anti-myeloperoxidase response in mice. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:3890-7. [PMID: 11034396 DOI: 10.4049/jimmunol.165.7.3890] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Anti-neutrophil cytoplasmic Abs, directed primarily toward myeloperoxidase (MPO) and proteinase 3, are detected in the majority of patients with distinct forms of small vessel vasculitides and pauci-immune necrotizing glomerulonephritis. However, the origin of these autoantibodies remains unknown. We studied the V region gene use in murine anti-MPO Abs derived from Spontaneous Crescentic Glomerulonephritis/Kinjoh mice. A total of 13 anti-MPO-producing hybridomas were generated from four unimmunized mice. Ten of the 13 hybridomas (corresponding to 3 of 4 clones) expressed Vkappa1C but differed in their use of VH genes. The remaining three hybridomas expressed a Vkappa5 gene. Anti-MPO hybridomas from individual mice were derived from single clones as deduced by sequence similarity and splice-site identity. We found a statistically significant bias of amino acid replacement mutations to the complementarity-determining regions (CDR) in the Vkappa1C-expressing hybridomas. Intriguingly, all 10 Vkappa1C hybridomas share a lysine to glutamate mutation in the CDR1. To determine the effects of somatic V gene mutations on binding to MPO, we generated an anti-MPO Ab with an unmutated Vkappa1C L chain and compared its ability to bind MPO with its mutated counterpart. The mutated hybridoma-derived Ab has a 4.75-fold higher avidity for MPO than the unmutated Ab. These results suggest that: 1) the L chain plays a dominant role in determining Ab specificity to MPO, 2) the anti-MPO Ab response is oligoclonal, consistent with Ag selection, and 3) MPO is a driving Ag in the murine anti-MPO Ab response.
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Affiliation(s)
- H S Jethwa
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill 27599, USA
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33
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Pokrić B. Precipitation at equivalence and equilibrium: a method for the determination of equilibrium constants of reaction between multideterminant antigen and specific polyclonal antibodies. JOURNAL OF CHEMICAL INFORMATION AND COMPUTER SCIENCES 2000; 40:524-9. [PMID: 10850754 DOI: 10.1021/ci990026d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A theoretical approach for the determination of the equilibrium constant, Ka, of the reaction between a multideterminant antigen (Ag) and specific polyclonal antibodies (Ab) forming the insoluble Ab/Ag immune complex, is derived. The constant can be expressed as a function of the two accessible experimental parameters, the precipitating concentration of the antigen and the Ab/Ag molar ratio. For this purpose Ab/Ag immune complex must be prepared at equivalence, and equilibrium between precipitated and soluble species must be reached. The proposed method is experimentally tested on the system human serum albumin (HSA) and polyclonal rabbit antibodies. The Ab/Ag precipitates are prepared by the direct mixing of biological fluids in which immunoreacting components naturally occur. Previous separation, purification, or labeling of immunoreacting components are not required. The conditions for the precipitation of Ab/Ag complexes at equivalence, the stoichiometric composition or the average number of Ab molecules bound to one Ag molecule, and the solubility of the immunoprecipitating components are determined by a rectangular two-dimensional double immunodiffusion. Since the solubility determined under the conditions of a double immunodiffusion is a result of the interaction of the global diffusion of the precipitating components and particle growth kinetics, it mostly refers to the dynamic conditions. To find the solubility under equilibrium conditions, it is sufficient to determine the minimal factor by which the solutions of both immunoprecipitating components should be diluted so that no precipitate is formed upon their mixing at equivalence. The dilution factor is determined by a measurement of the laser light scattering of the immunoprecipitating systems prepared with serially diluted Ag and Ab solutions.
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Affiliation(s)
- B Pokrić
- Ruder Bosković Institute, Zagreb, Croatia.
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34
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Ricoux R, Chazaud B, Tresca JP, Pontet M. Quality control of coated antibodies: new, rapid determination of binding affinity. Clin Chem Lab Med 2000; 38:239-43. [PMID: 10905761 DOI: 10.1515/cclm.2000.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A procedure is described for the determination of the affinity constant between a fluid-phase biotinylated antigen and a solid-phase monoclonal antibody. This procedure allows evaluation of the efficiency of an antibody as a coated tool for an immunoassay. For this purpose, the biotinylation of the antigen and its further quantitative measurement by streptavidin-peroxidase led to a single reversible interaction, the binding affinity of which greatly determines the quality of the assay. The free and bound fractions of the biotinylated antigen were obtained in wells coated with a low level of immobilized antibodies. At the equilibrium state, the free antigen present in the supernatant of these wells was further transferred to high level antibody coated wells which captured all the free antigen molecules. These molecules were quantified using a standard curve established with known concentrations of biotinylated antigen, also incubated in wells coated with the high level of antibody.
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Affiliation(s)
- R Ricoux
- Laboratoire de Protéines de la Réaction Inflammatoire, Centre Universitaire des Saints-Pères, Université Paris V, France.
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35
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Odenbaugh AL, Helms ED, Iverson BL. An investigation of antibody acyl hydrolysis catalysis using a large set of related haptens. Bioorg Med Chem 2000; 8:413-26. [PMID: 10722164 DOI: 10.1016/s0968-0896(99)00302-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
An aspect of catalytic antibody research that receives little attention in the literature involves hapten systems that fail to elicit antibody catalysts despite a high affinity immune response and hapten designs that resemble those known to elicit catalysts. We have investigated a series of 12 phosphate and phosphonate haptens in a total of three animal systems. Dramatic and reproducible differences were observed in the catalytic activities of polyclonal antibodies elicited by the different haptens. A phosphate hapten with a phenyl ring on the side of the hapten opposite the linker elicited reproducibly high levels of polyclonal antibody catalytic activity. The other 11 haptens, most with benzyl groups on the side of the hapten opposite the linker, elicited immune responses in which catalytic activity was significantly weaker in terms of the level of observed catalytic activity, as well as frequency of elicited catalysts. Our results indicate that subtle features of transition state analogue hapten structure can have a dramatic and reproducible influence over the catalytic activity of elicited antibodies in related haptens. Whatever the explanation, subtle changes in mechanistic features due to altered leaving group ability/location or overall hapten flexibility, the comprehensive data presented here indicate that phenyl or 4-nitrophenyl leaving groups located opposite the hapten linker are to be preferred in order to elicit highly active antibody catalysts for acyl hydrolysis reactions.
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Affiliation(s)
- A L Odenbaugh
- The Department of Chemistry and Biochemistry, The University of Texas at Austin, 78712, USA
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36
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McFarland CD, Jenkins M, Griesser HJ, Chatelier RC, Steele JG, Underwood PA. Albumin-binding surfaces: synthesis and characterization. JOURNAL OF BIOMATERIALS SCIENCE. POLYMER EDITION 1998; 9:1207-25. [PMID: 9860181 DOI: 10.1163/156856298x00730] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The nature of the proteinaceous film deposited on a biomaterial surface following implantation is a key determinant of the subsequent biological response. To achieve selectivity in the formation of this film, monoclonal antibodies have been coupled to a range of solid substrates using avidin-biotin technology. Antibody clones varied in their antigen-binding activity following insertion of biotin groups into lysine residues. Biotinylated antibodies coupled to solid substrates via an immobilized avidin bridge retained their biological activity. During immobilization of avidin a significant proportion of the protein molecules were passively adsorbed rather than covalently attached to the surface. This loosely bound material could be removed by stringent elution procedures which resulted in a surface density of 5.4 pmol avidin cm(-2). Although these conditions would be harsh enough to denature monoclonal antibodies, they did not destroy the biotin-binding activity of the residual surface-coupled avidin, enabling the subsequent immobilization of biotinylated antibodies. The two-step immobilization technique allowed the use of gentle protein modification procedures, reduced the risk of surface-induced denaturation and removed loosely bound material from the surface. The versatility of the technique encourages its application to a wide range of immobilization systems where retention of biological activity is a key requirement.
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Affiliation(s)
- C D McFarland
- Cooperative Research Centre for Cardiac Technology, CSIRO Molecular Science, Sydney Laboratory, North Ryde, NSW, Australia
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37
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Loomans EE, Gribnau TC, Bloemers HP, Schielen WJ. The influence of binding capacity and affinity on the improved performance of N-terminally extended hCG peptides, determined by ELISA-based procedures. J Immunol Methods 1998; 221:119-30. [PMID: 9894903 DOI: 10.1016/s0022-1759(98)00173-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The improvement of peptide-ELISA responses by the use of small synthetic peptides elongated at the N-terminus with an Ata-group or a (Lys)7 extension has been analyzed. For this purpose, binding capacity and affinity were evaluated by specific ELISA procedures. The ELISA experiments on binding capacity, performed with saturating antibody concentrations, revealed a difference of more than three orders of magnitude in binding capacity between the parent peptides and the N-terminally linked peptides, in favor of the latter peptides. Antibody affinity values were determined by a liquid-phase equilibrium method as well as by a solid-phase equilibrium method. N-terminal extension of the peptides had almost no effect on the affinity when equilibrium between the peptide and the antibody was reached in solution. In contrast, solid-phase affinity was greatly enhanced when the N-terminally linked peptides were adsorbed to the polystyrene surface. This enhancement was determined by the N-terminal extension and the peptide amino acid sequence (40 to 600 times higher). Thus, the use of N-terminally extended peptides can greatly increase the performance of a peptide-ELISA through improved surface effects, resulting in higher binding capacity and functional affinity.
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Affiliation(s)
- E E Loomans
- ATO-DLO, Department of Industrial Proteins, Wageningen, The Netherlands
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38
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Abstract
The utilization of computational models in immunology dates from the birth of the science. From the description of antibody-antigen binding to the structural models of receptors, models are utilized to bring fundamental understandings of the processes together with laboratory measurements to uncover implications of these data. In this review, an historical view of the role of computational models in the immunology laboratory is presented, and short mathematical descriptions are given of fundamental assays. In addition, the range of current uses of models is explored -- especially as seen through papers which have appeared in the Journal of Immunological Methods from volume 1 (1971/1972) to volume 208 (1997). Each paper which introduced a new mathematical, statistical, or computer simulation model, or introduced an enhancement to an instrument through a model in those volumes is cited and the type of computational model noted.
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Affiliation(s)
- S J Merrill
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI 53201-1881, USA
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Larsson A. Regression analysis of simulated radio-ligand equilibrium experiments using seven different mathematical models. J Immunol Methods 1997; 206:135-42. [PMID: 9328576 DOI: 10.1016/s0022-1759(97)00100-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The objective of this study was to investigate the conditions for regression analysis of data from equilibrium experiments. One important issue was to recognize that Kd and the binding site concentration (A) are not of equal nature, although both are parameters in the regression analysis. Whereas Kd approximates to a true constant, A is subject to experimental variation due to pipetting errors and in solid-phase experiments also to uneven coating properties. While recognizing that the ideal assumptions for ordinary regression analysis are poorly satisfied, different regression models were evaluated by extensive simulations. It was first established by a 'worst case' investigation that a limited error (8%) in the dependent variable is not critical for the results obtained at curve-fitting to Langmuir's equation. Seven different equations were compared for the calculation of data representing a solid-phase equilibrium experiment with statistical but no systematic errors. All the equations are rearrangements of the law of mass action. In this setting the Scatchrd plot gave the best result, but also the double reciprocal and the Woolf plots worked well in weighted analysis. Langmuir's equation gave the best result of the 4 nonlinear regression models tested. The influence of one type of systematic error was also investigated. This assumed that 10% of the label was positioned on particles other than the functional ligand molecules. This systematic error was amplified, which resulted in a substantial bias. The calculated Kd-values varied slightly with the regression method used and were almost 24% too high in the best methods.
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Affiliation(s)
- A Larsson
- Department of Immunology, Wenner-Gren Institute, Stockholm University, Sweden
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40
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Mattes MJ. Binding parameters of antibodies reacting with multivalent antigens: functional affinity or pseudo-affinity. J Immunol Methods 1997; 202:97-101. [PMID: 9075776 DOI: 10.1016/s0022-1759(96)00228-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
For antibodies binding bivalently to multivalent antigens, including the cell surface, it has been common to determine the 'functional affinity', even though it is clear that the equations describing true affinity only apply to monovalent interactions. We here summarize evidence that 'functional affinities' are not valid, because they do not accurately describe the interactions that occur. A basic discrepancy is that dissociation, in practice, is generally not a first-order reaction. A more useful approach to compare antibodies is to determine the kinetics of dissociation over a long time period, until near-complete dissociation has occurred.
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41
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Sanny CG, Price JA. Analysis of antibody-antigen interactions using size-exclusion high-performance (pressure) liquid chromatography. Anal Biochem 1997; 246:7-14. [PMID: 9056176 DOI: 10.1006/abio.1996.9995] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The development of methods to measure avidity of anti-sera reacting to antigen in solution using size-exclusion high-performance (pressure) liquid chromatography (SE-HPLC) was initiated using a model system composed of human serum albumin (HSA) and mouse anti-HSA IgG (mIgG). Mixtures containing varying concentrations of mIgG and HSA (mIgG, 0-2.4 microM, and HSA, 3.2 microM; mIgG, 0.80 microM, and HSA, 0-6.3 microM) were incubated for 1 h at 37 degrees C. Mixture components were separated using a Bio-Sil TSK 250 size exclusion column (300 x 7.5 mm) equilibrated with 0.05 m sodium phosphate buffer (pH 6.8) containing 0.1 m sodium sulfate. Four separate peaks containing either HSA, mIgG, an intermediate molecular weight complex (C1) or a high-molecular-weight complex (C2) could be identified from the elution profiles at 280 nm. Plots of peak areas versus initial mIgG or HSA concentrations could be modeled mathematically using equations from the law of mass action. Apparent binding constants (1.1 x 10(7) to 5.2 x 10(7) liters/mol) and stoichiometry of binding are consistent with that reported in the literature.
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Affiliation(s)
- C G Sanny
- Oklahoma State University College of Osteopathic Medicine, 1111 West 17th Street, Tulsa, Oklahoma, 74107, USA
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42
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Determination of kinetic parameters of epitope-paratope interaction based on solid phase binding: An inexpensive alternate to biospecific interaction analysis. J Biosci 1996. [DOI: 10.1007/bf02703142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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43
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Ferreira MU, Katzin AM. The assessment of antibody affinity distribution by thiocyanate elution: a simple dose-response approach. J Immunol Methods 1995; 187:297-305. [PMID: 7499889 DOI: 10.1016/0022-1759(95)00186-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We describe a simple dose-response approach to assess the affinity distribution of polyclonal antibodies. The proportion of antigen-specific antibodies dissociated by increasing concentrations of the mild chaotropic agent ammonium thiocyanate (NH4SCN) was measured by enzyme immunoassay, and the distribution of tolerances to this agent was presented in a histogram form. Such 'tolerance distribution', which is analogous to that described in classical dose-response bioassays, is proposed as a representation of the actual antibody affinity distribution. To test this approach, we assessed affinity maturation patterns of anti-Plasmodium falciparum IgG antibodies in paired sera obtained from 22 malaria patients during the acute infection and convalescence. We obtained patterns of antibody affinity distributions consistent with those previously described in immunization experiments with the aid of more complex laboratory and computational approaches. Therefore, we suggest the thiocyanate elution technique as an alternative method for rapid assessment of affinity distributions of polyclonal antibodies elicited against complex antigens, readily applicable to large number of serum samples.
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Affiliation(s)
- M U Ferreira
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, Brazil
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44
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Loomans EE, Roelen AJ, Van Damme HS, Bloemers HP, Gribnau TC, Schielen WJ. Assessment of the functional affinity constant of monoclonal antibodies using an improved enzyme-linked immunosorbent assay. J Immunol Methods 1995; 184:207-217. [PMID: 7658024 DOI: 10.1016/0022-1759(95)00089-s] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The use of an enzyme-linked immunosorbent assay (ELISA) for the determination of affinity constants implies heterogeneous measurements. Therefore, despite their simplicity, direct solid-phase binding assays are not common. Many investigators have serious, and mostly justified, reservations about the application of solid-phase affinity methods. They refer to problems such as diffusion effects and difficulties in reaching equilibrium due to heterogeneous binding and co-operativity. Accordingly, functional affinity determinations are often described as meaningless. These objections apply to the measurement of the affinity of a monoclonal antibody using the enzyme-linked immunosorbent assay of Beatty et al. (J. Immunol. Methods (1987) 100, 173), which is based on the effect of antibody affinity on the sigmoidal dose response curve. The affinity constant is calculated by mathematical equations, based on the Law of Mass Action and the authors made a number of important assumptions--avoiding the above mentioned problems--in order to justify the use of the Law of Mass Action. By carefully examining these assumptions we have developed an improved ELISA procedure for functional affinity determinations on the basis of a primary coating with the antigen only. the coating conditions were validated by employing gold labelled colloidal particles and physical counting of the bound particles under the scanning electron microscope. Since monovalent binding between human chorionic gonadotropin and its monoclonal antibody could be achieved under equilibrium conditions, the application of the Law of Mass Action and hence of the Beatty formula became possible. We conclude that under these conditions functional affinity determinations are appropriate.
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Affiliation(s)
- E E Loomans
- AKZO NOBEL, Organon Teknika B.V., Chemistry Research Unit, AB Boxtel, Netherlands
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45
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Chargelegue D, Stanley CM, O'Toole CM, Colvin BT, Steward MW. The affinity of IgG antibodies to gag p24 and p17 in HIV-1-infected patients correlates with disease progression. Clin Exp Immunol 1995; 99:175-81. [PMID: 7851008 PMCID: PMC1534313 DOI: 10.1111/j.1365-2249.1995.tb05529.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The affinity of anti-gag antibody was studied for up to 9 years (1984-1993) in sera from 15 HIV-1+ patients with haemophilia. On the basis of their 1993 clinical status patients were divided into two groups: (i) patients who remained asymptomatic (n = 9); and (ii) those who progressed to AIDS between late 1987 and 1993. The affinity constants of antibody for p24 and p17 were determined by a double isotope fluid-phase radioimmunoassay; and the relationships between antibody affinity and titre, patient clinical course, CD4 cell counts and p24 antigenaemia were analysed. The affinity of p24- and p17-specific antibody was up to 100 times greater in asymptomatic patients than in patients who progressed to AIDS. Patients who developed AIDS either lost or failed to develop high-affinity antibodies early in the infection. Asymptomatic patients maintained high-affinity antibodies for several years; however, in some of these patients the affinity of anti-p24 and p17 antibodies subsequently fell later in the study period. The presence of low-affinity antibody and progressive reduction in the titre of specific antibody were earlier predictors of disease onset than CD4 cell counts. The failure to either develop or maintain high affinity gag-specific antibody suggests an early impairment of T helper function in individuals who progressed to AIDS. The presence of antibody of high affinity could be essential in controlling virus replication and the onset of AIDS.
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46
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Tangemann K, Engel J. Demonstration of non-linear detection in ELISA resulting in up to 1000-fold too high affinities of fibrinogen binding to integrin alpha IIb beta 3. FEBS Lett 1995; 358:179-81. [PMID: 7530218 DOI: 10.1016/0014-5793(94)01411-s] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To clarify the question as to why different solid-phase assays yield different results in terms of interaction strength, we used fibrinogen binding to immobilized alpha IIb beta 3 integrin as a test system. A classical 'three step' enzyme-linked (ELISA), a 'two step' biotin enzyme-linked streptavidin and a 'one step' radioligand assay were compared under otherwise identical conditions. Only the last assay yielded binding constants comparable to earlier data by total internal reflection fluorescence microscopy while the other assays yielded apparent binding constants 5- to 1000-fold too high. These effects are explained by non-linearity of detection signals.
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Affiliation(s)
- K Tangemann
- Biozentrum, University of Basel, Switzerland
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47
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Panfili PR, Dill K, Olson JD. Immunochemical detection using the light-addressable potentiometric sensor. Curr Opin Biotechnol 1994; 5:60-4. [PMID: 7764645 DOI: 10.1016/s0958-1669(05)80071-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Rapid, sensitive and flexible assay systems are needed for immunoassays, receptor-ligand binding studies and DNA probe assays. Filtration capture and sensor detection offer several advantages to these areas. Although dependent on the affinity of the specific binders employed, the sensitivity of these techniques can be in the order of 10(-12) M, and total assay time can be less than 15 minutes.
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