1
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Gaetani ML, Pinto IC, Li M, O'Connor P, Giorgi-Coll S, Tyreman M, Rumary KL, Schouten JA, Davis P, Dixon AM. Towards detection of structurally-diverse glycated epitopes in native proteins: Single-chain antibody directed to non-A1c epitope in human haemoglobin. Mol Immunol 2024; 166:16-28. [PMID: 38181455 DOI: 10.1016/j.molimm.2023.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/15/2023] [Accepted: 12/18/2023] [Indexed: 01/07/2024]
Abstract
Over 500 million people worldwide are affected by diabetes mellitus, a chronic disease that leads to high blood glucose levels and causes severe side effects. The predominant biological marker for diagnosis of diabetes is glycated haemoglobin (GHb). In human blood the predominant reducing sugar, glucose, irreversibly conjugates onto accessible amine groups within Hb. Most methods for diagnosis and monitoring of diabetes selectively detect N-terminal glycation at Val-1 on the β-globin chain, but not glycation at other sites. Detection of other glycated epitopes of GHb has the potential to provide new information on the extent, duration and timing of elevated glucose, facilitating personalised diagnosis and intelligent diabetic control. In this work, a new anti-GHb Fab antibody (Fab-1) specific for haemoglobin A1c (HbA1c) with nanomolar affinity was discovered via epitope-directed immunisation and phage display. A single chain variable fragment (scFv) antibody derived from Fab-1 retained affinity and specificity for HbA1c, and affinity was enhanced tenfold upon addition of an enhanced green fluorescent protein tag. Both the scFv and Fab-1 recognised an epitope within HbA1c that was distinct from β-Val-1, and our data suggest that this epitope may include glycation at Lys-66 in the β-globin chain. To our knowledge, this is the first report of an scFv/Fab anti-glycated epitope antibody that recognises a non-A1c epitope in GHb, and confirms that fructosamine attached to different, discrete glycation sites within the same protein can be resolved from one another by immunoassay.
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Affiliation(s)
- Miss Lucia Gaetani
- Medical Research Council Doctoral Training Programme, Warwick Medical School, UK
| | - Isabel Campos Pinto
- iBET, Bayer Satellite Lab, Av. República, Quinta do Marquês, Edifício iBET/ITQB, Oeiras 2780-157, Portugal
| | - Meng Li
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
| | - Peter O'Connor
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
| | | | - Matthew Tyreman
- Global Access Diagnostics, Thurleigh, Bedfordshire MK44 2YA, UK
| | | | | | - Paul Davis
- Global Access Diagnostics, Thurleigh, Bedfordshire MK44 2YA, UK
| | - Ann M Dixon
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
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2
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Slay RM, Cook R, Hendricks K, Boucher D, Merchlinsky M. Pre- and Postlicensure Animal Efficacy Studies Comparing Anthrax Antitoxins. Clin Infect Dis 2022; 75:S441-S450. [PMID: 36251555 PMCID: PMC9649416 DOI: 10.1093/cid/ciac593] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND The deliberate use of Bacillus anthracis spores is believed by the US government to be a high bioweapons threat. The first line of defense following potential exposure to B. anthracis spores would be postexposure prophylaxis with antimicrobials that have activity against B. anthracis. Additional therapies to address the effects of toxins may be needed in systemically ill individuals. Over the last 2 decades, the United States government (USG) collaborated with the private sector to develop, test, and stockpile 3 antitoxins: anthrax immunoglobulin intravenous (AIGIV), raxibacumab, and obiltoxaximab. All 3 products target protective antigen, a protein factor common to the 2 exotoxins released by B. anthracis, and hamper or block the toxins' effects and prevent or reduce pathogenesis. These antitoxins were approved for licensure by the United States Food and Drug Administration based on animal efficacy studies compared to placebo. METHODS We describe USG-sponsored pre- and postlicensure studies that compared efficacy of 3 antitoxins in a New Zealand White rabbit model of inhalation anthrax; survival following a lethal aerosolized dose of B. anthracis spores was the key measure of effectiveness. To model therapeutic intervention, intravenous treatments were started following onset of antigenemia. RESULTS In pre- and postlicensure studies, all 3 antitoxins were superior to placebo; in the postlicensure study, raxibacumab and obiltoxaximab were superior to AIGIV, but neither was superior to the other. CONCLUSIONS These data illustrate the relative therapeutic benefit of the 3 antitoxins and provide a rationale to prioritize their deployment.
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Affiliation(s)
- Raymond M Slay
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Rachel Cook
- Oak Ridge Institute for Science and Education, CDC Fellowship Program, Division of High-Consequence Pathogens and Pathology, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Katherine Hendricks
- Division of High-Consequence Pathogens and Pathology, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - David Boucher
- Office of the Assistant Secretary for Preparedness and Response, Biomedical Advanced Research and Development Authority, Washington, District of Columbia, USA
| | - Michael Merchlinsky
- Office of the Assistant Secretary for Preparedness and Response, Biomedical Advanced Research and Development Authority, Washington, District of Columbia, USA
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3
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Wang H, Chen D, Lu H. Anti-bacterial monoclonal antibodies: next generation therapy against superbugs. Appl Microbiol Biotechnol 2022; 106:3957-3972. [PMID: 35648146 DOI: 10.1007/s00253-022-11989-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 05/12/2022] [Accepted: 05/16/2022] [Indexed: 12/19/2022]
Abstract
Prior to the nineteenth century, infectious disease was one of the leading causes of death. Human life expectancy has roughly doubled over the past century as a result of the development of antibiotics and vaccines. However, the emergence of antibiotic-resistant superbugs brings new challenges. The side effects of broad-spectrum antibiotics, such as causing antimicrobial resistance and destroying the normal flora, often limit their applications. Furthermore, the development of new antibiotics has lagged far behind the emergence and spread of antibiotic resistance. On the other hand, the genome complexity of bacteria makes it difficult to create effective vaccines. Therefore, novel therapeutic agents in supplement to antibiotics and vaccines are urgently needed to improve the treatment of infections. In recent years, monoclonal antibodies (mAbs) have achieved remarkable clinical success in a variety of fields. In the treatment of infectious diseases, mAbs can play functions through multiple mechanisms, including toxins neutralization, virulence factors inhibition, complement-mediated killing activity, and opsonic phagocytosis. Toxins and bacterial surface components are good targets to generate antibodies against. The U.S. FDA has approved three monoclonal antibody drugs, and there are numerous candidates in the preclinical or clinical trial stages. This article reviews recent advances in the research and development of anti-bacterial monoclonal antibody drugs in order to provide a valuable reference for future studies in this area. KEY POINTS: • Novel drugs against antibiotic-resistant superbugs are urgently required • Monoclonal antibodies can treat bacterial infections through multiple mechanisms • There are many anti-bacterial monoclonal antibodies developed in recent years and some candidates have entered the preclinical or clinical stages of development.
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Affiliation(s)
- Hui Wang
- Engineering Research Center of Cell and Therapeutic Antibody, Ministry of Education, School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China
- School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China
| | - Daijie Chen
- School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China
| | - Huili Lu
- Engineering Research Center of Cell and Therapeutic Antibody, Ministry of Education, School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.
- School of Pharmacy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.
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4
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Abstract
![]()
The paradigm of antivirulence
therapy dictates that bacterial pathogens
are specifically disarmed but not killed by neutralizing their virulence
factors. Clearance of the invading pathogen by the immune system is
promoted. As compared to antibiotics, the pathogen-selective antivirulence
drugs hold promise to minimize collateral damage to the beneficial
microbiome. Also, selective pressure for resistance is expected to
be lower because bacterial viability is not directly affected. Antivirulence
drugs are being developed for stand-alone prophylactic and therapeutic
treatments but also for combinatorial use with antibiotics. This Review
focuses on drug modalities that target bacterial exotoxins after the
secretion or release-upon-lysis. Exotoxins have a significant and
sometimes the primary role as the disease-causing virulence factor,
and thereby they are attractive targets for drug development. We describe
the key pre-clinical and clinical trial data that have led to the
approval of currently used exotoxin-targeted drugs, namely the monoclonal
antibodies bezlotoxumab (toxin B/TcdB, Clostridioides difficile), raxibacumab (anthrax toxin, Bacillus anthracis), and obiltoxaximab (anthrax toxin, Bacillus anthracis), but also to challenges with some of the promising leads. We also
highlight the recent developments in pre-clinical research sector
to develop exotoxin-targeted drug modalities, i.e., monoclonal antibodies,
antibody fragments, antibody mimetics, receptor analogs, neutralizing
scaffolds, dominant-negative mutants, and small molecules. We describe
how these exotoxin-targeted drug modalities work with high-resolution
structural knowledge and highlight their advantages and disadvantages
as antibiotic alternatives.
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Affiliation(s)
- Moona Sakari
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
| | - Arttu Laisi
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
| | - Arto T. Pulliainen
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
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5
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Burdette LA, Wong HT, Tullman-Ercek D. An optimized growth medium for increased recombinant protein secretion titer via the type III secretion system. Microb Cell Fact 2021; 20:44. [PMID: 33588857 PMCID: PMC7885374 DOI: 10.1186/s12934-021-01536-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/02/2021] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Protein secretion in bacteria is an attractive strategy for heterologous protein production because it retains the high titers and tractability of bacterial hosts while simplifying downstream processing. Traditional intracellular production strategies require cell lysis and separation of the protein product from the chemically similar cellular contents, often a multi-step process that can include an expensive refolding step. The type III secretion system of Salmonella enterica Typhimurium transports proteins from the cytoplasm to the extracellular environment in a single step and is thus a promising solution for protein secretion in bacteria. Product titer is sensitive to extracellular environmental conditions, however, and T3SS regulation is integrated with essential cellular functions. Instead of attempting to untangle a complex web of regulatory input, we took an "outside-in" approach to elucidate the effect of growth medium components on secretion titer. RESULTS We dissected the individual and combined effects of carbon sources, buffers, and salts in a rich nutrient base on secretion titer. Carbon sources alone decreased secretion titer, secretion titer increased with salt concentration, and the combination of a carbon source, buffer, and high salt concentration had a synergistic effect on secretion titer. Transcriptional activity measured by flow cytometry showed that medium composition affected secretion system activity, and prolonged secretion system activation correlated strongly with increased secretion titer. We found that an optimal combination of glycerol, phosphate, and sodium chloride provided at least a fourfold increase in secretion titer for a variety of proteins. Further, the increase in secretion titer provided by the optimized medium was additive with strain enhancements. CONCLUSIONS We leveraged the sensitivity of the type III secretion system to the extracellular environment to increase heterologous protein secretion titer. Our results suggest that maximizing secretion titer via the type III secretion system is not as simple as maximizing secreted protein expression-one must also optimize secretion system activity. This work advances the type III secretion system as a platform for heterologous protein secretion in bacteria and will form a basis for future engineering efforts.
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Affiliation(s)
- Lisa Ann Burdette
- Department of Chemical and Biomolecular Engineering, University of California-Berkeley, Berkeley, USA
- Present Address: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208 USA
| | - Han Teng Wong
- Present Address: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208 USA
- Department of Plant and Microbial Biology, University of California-Berkeley, Berkeley, USA
- Present Address: Institute of Molecular and Cell Biology, 61 Biopolis Way, Singapore, 138673 Singapore
| | - Danielle Tullman-Ercek
- Present Address: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208 USA
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6
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Nishiguchi A, Numoto N, Ito N, Azuma T, Oda M. Three-dimensional structure of a high affinity anti-(4-hydroxy-3-nitrophenyl)acetyl antibody possessing a glycine residue at position 95 of the heavy chain. Mol Immunol 2019; 114:545-552. [DOI: 10.1016/j.molimm.2019.09.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/23/2019] [Accepted: 09/02/2019] [Indexed: 10/26/2022]
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7
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Attachment of flagellin enhances the immunostimulatory activity of a hemagglutinin-ferritin nano-cage. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2019; 17:223-235. [DOI: 10.1016/j.nano.2019.01.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 10/31/2018] [Accepted: 01/11/2019] [Indexed: 12/15/2022]
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8
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Mishra S, Manish M. Studies on computational grafting of malarial epitopes in serum albumin. Comput Biol Med 2018; 102:126-131. [PMID: 30268977 DOI: 10.1016/j.compbiomed.2018.09.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 09/22/2018] [Accepted: 09/23/2018] [Indexed: 11/19/2022]
Abstract
BACKGROUND Antigens (or their epitopes)-carrier protein combinations are extensively utilized for vaccine development strategies. Chemical conjugation methods are cumbersome with limited conjugation sites. Computational protein modelling methods can evaluate every position of a carrier protein for conjugation via epitope grafting in a reasonable time frame as compared to wet experimental techniques. Graftibility of positions can be estimated by the presence of native atomic contacts in resulting chimeric antigen. METHODOLOGY Five epitopes were selected, and computational grafting at each position was performed in three templates of serum albumin. Protein modelling algorithms such as segment matching and satisfaction of spatial restraints were employed for computational grafting. Contact-based protein discriminatory function was used to evaluate the chimeric proteins having native atomic contacts. RESULTS On the evaluation of approximately 1 million distinct protein modelling simulations, region around the 450th position of serum albumin was observed to be suitable for epitope grafting. CONCLUSION Computational protein modelling tools may be used to design a chimeric antigen. The approach may overcome the limitations associated with chemical conjugation and furthermore harness the potential of custom gene synthesis/recombinant protein production.
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Affiliation(s)
- Smriti Mishra
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, 110067, India.
| | - Manish Manish
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, 110067, India; ICMR-National Institute of Malaria Research, Dwarka, Sector-8, New Delhi, 110077, India.
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9
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Acquaye-Seedah E, Huang Y, Sutherland JN, DiVenere AM, Maynard JA. Humanised monoclonal antibodies neutralise pertussis toxin by receptor blockade and reduced retrograde trafficking. Cell Microbiol 2018; 20:e12948. [PMID: 30152075 PMCID: PMC6519169 DOI: 10.1111/cmi.12948] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 08/02/2018] [Accepted: 08/20/2018] [Indexed: 12/12/2022]
Abstract
Pertussis toxin (PTx) is a major protective antigen produced by Bordetella pertussis that is included in all current acellular vaccines. Of several well‐characterized monoclonal antibodies binding this toxin, the humanised hu1B7 and hu11E6 antibodies are highly protective in multiple in vitro and in vivo assays. In this study, we determine the molecular mechanisms of protection mediated by these antibodies. Neither antibody directly binds the B. pertussis bacterium nor supports antibody‐dependent complement cytotoxicity. Both antibodies, either individually or as a cocktail, form multivalent complexes with soluble PTx that bind the FcγRIIb receptor more tightly than antibody alone, suggesting that the antibodies may accelerate PTx clearance via immune complex formation. However, a receptor binding assay and cellular imaging indicate that the main mechanism used by hu11E6 is competitive inhibition of PTx binding to its cellular receptor. In contrast, the main hu1B7 neutralising mechanism appears to be inhibition of PTx internalisation and retrograde trafficking. We assessed the effects of hu1B7 on PTx retrograde trafficking in CHO‐K1 cells using quantitative immunofluorescence microscopy. In the absence of hu1B7 or after incubation with an isotype control antibody, PTx colocalizes to organelles in a manner consistent with retrograde transport. However, after preincubation with hu1B7, PTx appears restricted to the membrane surface with colocalization to organelles associated with retrograde transport significantly reduced. Together, these data support a model whereby hu11E6 and hu1B7 interfere with PTx receptor binding and PTx retrograde trafficking, respectively.
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Affiliation(s)
- Edith Acquaye-Seedah
- Department of Biochemistry, The University of Texas at Austin, Austin, Texas.,Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas
| | - Yimin Huang
- Department of Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas.,Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas
| | - Jamie N Sutherland
- Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas
| | - Andrea M DiVenere
- Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas
| | - Jennifer A Maynard
- Department of Biochemistry, The University of Texas at Austin, Austin, Texas.,Department of Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas.,Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas
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10
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Entzminger KC, Hyun JM, Pantazes RJ, Patterson-Orazem AC, Qerqez AN, Frye ZP, Hughes RA, Ellington AD, Lieberman RL, Maranas CD, Maynard JA. De novo design of antibody complementarity determining regions binding a FLAG tetra-peptide. Sci Rep 2017; 7:10295. [PMID: 28860479 PMCID: PMC5579192 DOI: 10.1038/s41598-017-10737-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 08/14/2017] [Indexed: 12/30/2022] Open
Abstract
Computational antibody engineering efforts to date have focused on improving binding affinities or biophysical characteristics. De novo design of antibodies binding specific epitopes could greatly accelerate discovery of therapeutics as compared to conventional immunization or synthetic library selection strategies. Here, we employed de novo complementarity determining region (CDR) design to engineer targeted antibody-antigen interactions using previously described in silico methods. CDRs predicted to bind the minimal FLAG peptide (Asp-Tyr-Lys-Asp) were grafted onto a single-chain variable fragment (scFv) acceptor framework. Fifty scFvs comprised of designed heavy and light or just heavy chain CDRs were synthesized and screened for peptide binding by phage ELISA. Roughly half of the designs resulted in detectable scFv expression. Four antibodies, designed entirely in silico, bound the minimal FLAG sequence with high specificity and sensitivity. When reformatted as soluble antigen-binding fragments (Fab), these clones expressed well, were predominantly monomeric and retained peptide specificity. In both formats, the antibodies bind the peptide only when present at the amino-terminus of a carrier protein and even conservative peptide amino acid substitutions resulted in a complete loss of binding. These results support in silico CDR design of antibody specificity as an emerging antibody engineering strategy.
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Affiliation(s)
- Kevin C Entzminger
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
| | - Jeong-Min Hyun
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
| | - Robert J Pantazes
- Department of Chemical Engineering, Auburn University, Auburn, AL, 36849, USA
| | | | - Ahlam N Qerqez
- Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712, USA
| | - Zach P Frye
- Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712, USA
| | - Randall A Hughes
- Applied Research Laboratories, University of Texas at Austin, Austin, TX, 78712, USA
| | - Andrew D Ellington
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA
| | - Raquel L Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Costas D Maranas
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, PA, 16802, USA
| | - Jennifer A Maynard
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, 78712, USA. .,Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
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11
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Lino CA, Caldeira JC, Peabody DS. Display of single-chain variable fragments on bacteriophage MS2 virus-like particles. J Nanobiotechnology 2017; 15:13. [PMID: 28193211 PMCID: PMC5307822 DOI: 10.1186/s12951-016-0240-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 12/03/2016] [Indexed: 11/11/2022] Open
Abstract
Background Virus-like particles (VLPs) of the RNA bacteriophage MS2 have many potential applications in biotechnology. MS2 VLPs provide a platform for peptide display and affinity selection (i.e. biopanning). They are also under investigation as vehicles for targeted drug delivery, using display of receptor-specific peptides or nucleic acid aptamers to direct their binding to specific cell-surface receptors. However, there are few molecules more suited to the precise targeting and binding of a cellular receptor than antibodies. Results Here we describe a strategy for display of four different functional single-chain variable fragments (scFvs) on the surface of the MS2 VLP. Each scFv is validated both for its presence on the surface of the VLP and for its ability to bind its cognate antigen. Conclusions This work demonstrates the suitability of the MS2 VLP platform to display genetically fused scFvs, allowing for many potential applications of these VLPs and paving the way for future work with libraries of scFvs displayed in a similar manner on the VLP surface. These libraries can then be biopanned and novel scFv binders to targets can be readily discovered.
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Affiliation(s)
- Christopher A Lino
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM, USA.
| | - Jerri C Caldeira
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM, USA
| | - David S Peabody
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM, USA
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12
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Metcalf KJ, Bevington JL, Rosales SL, Burdette LA, Valdivia E, Tullman-Ercek D. Proteins adopt functionally active conformations after type III secretion. Microb Cell Fact 2016; 15:213. [PMID: 28010734 PMCID: PMC5180411 DOI: 10.1186/s12934-016-0606-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/25/2016] [Indexed: 11/17/2022] Open
Abstract
Background Bacterial production of natively folded heterologous proteins by secretion to the extracellular space can improve protein production by simplifying purification and enabling continuous processing. In a typical bacterial protein production process, the protein of interest accumulates in the cytoplasm of the cell, requiring cellular lysis and extensive purification to separate the desired protein from other cellular constituents. The type III secretion system of Gram-negative bacteria is used to secrete proteins from the cytosol to the extracellular space in one step, but proteins must unfold during translocation, necessitating the folding of secreted proteins in the extracellular space for an efficient production process. We evaluated type III secretion as a protein production strategy by characterizing and quantifying the extent of correct folding after secretion. Results We probed correct folding by assaying the function after secretion of two enzymes—beta-lactamase and alkaline phosphatase—and one single-chain variable fragment of an antibody. Secreted proteins are correctly folded and functional after unfolding, secretion, and refolding in the extracellular space. Furthermore, structural and chemical features required for protein function, such as multimerization and disulfide bond formation, are evident in the secreted protein samples. Finally, the concentration of NaCl in the culture media affects the folding efficiency of secreted proteins in a protein-specific manner. Conclusions In the extracellular space, secreted proteins are able to fold to active conformations, which entails post-translational modifications including: folding, multimerization, acquisition of metal ion cofactors, and formation of disulfide bonds. Further, different proteins have different propensities to refold in the extracellular space and are sensitive to the chemical environment in the extracellular space. Our results reveal strategies to control the secretion and correct folding of diverse target proteins during bacterial cell culture. Electronic supplementary material The online version of this article (doi:10.1186/s12934-016-0606-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kevin James Metcalf
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA.,Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - James Lea Bevington
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA
| | - Sandy Lisette Rosales
- Department of Nutritional Science and Toxicology, University of California, Berkeley, CA, 94720, USA
| | - Lisa Ann Burdette
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA.,Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Elias Valdivia
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA.
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13
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Mamillapalli S, Miyagi M, Bann JG. Stability of domain 4 of the anthrax toxin protective antigen and the effect of the VWA domain of CMG2 on stability. Protein Sci 2016; 26:355-364. [PMID: 27874231 DOI: 10.1002/pro.3087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Revised: 11/14/2016] [Accepted: 11/15/2016] [Indexed: 01/04/2023]
Abstract
The major immunogenic component of the current anthrax vaccine, anthrax vaccine adsorbed (AVA) is protective antigen (PA). We have shown recently that the thermodynamic stability of PA can be significantly improved by binding to the Von-Willebrand factor A (VWA) domain of capillary morphogenesis protein 2 (CMG2), and improvements in thermodynamic stability may improve storage and long-term stability of PA for use as a vaccine. In order to understand the origin of this increase in stability, we have isolated the receptor binding domain of PA, domain 4 (D4), and have studied the effect of the addition of CMG2 on thermodynamic stability. We are able to determine a binding affinity between D4 and CMG2 (∼300 nM), which is significantly weaker than that between full-length PA and CMG2 (170-300 pM). Unlike full-length PA, we observe very little change in stability of D4 on binding to CMG2, using either fluorescence or 19 F-NMR experiments. Because in previous experiments we could observe a stabilization of both domain 4 and domain 2, the mechanism of stabilization of PA by CMG2 is likely to involve a mutual stabilization of these two domains.
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Affiliation(s)
| | - Masaru Miyagi
- Case Center for Proteomics and Bioinformatics, Department of Pharmacology and Department of Opthamology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, 44106
| | - James G Bann
- Department of Chemistry, Wichita State University, Wichita, Kansas, 67260
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14
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Schiele F, van Ryn J, Litzenburger T, Ritter M, Seeliger D, Nar H. Structure-guided residence time optimization of a dabigatran reversal agent. MAbs 2016; 7:871-80. [PMID: 26047352 DOI: 10.1080/19420862.2015.1057364] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Novel oral anticoagulants are effective and safe alternatives to vitamin-K antagonists for anticoagulation therapy. However, anticoagulation therapy in general is associated with an elevated risk of bleeding. Idarucizumab is a reversal agent for the direct thrombin inhibitor, dabigatran etexilate (Pradaxa®) and is currently in Phase 3 studies. Here, we report data on the antibody fragment aDabi-Fab2, a putative backup molecule for idarucizumab. Although aDabi-Fab2 completely reversed effects of dabigatran in a rat model in vivo, we observed significantly reduced duration of action compared to idarucizumab. Rational protein engineering, based on the X-ray structure of aDabi-Fab2, led to the identification of mutant Y103W. The mutant had optimized shape complementarity to dabigatran while maintaining an energetically favored hydrogen bond. It displayed increased affinity for dabigatran, mainly driven by a slower off-rate. Interestingly, the increased residence time translated into longer duration of action in vivo. It was thus possible to further enhance the efficacy of aDabi-Fab2 based on rational design, giving it the potential to serve as a back-up candidate for idarucizumab.
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Affiliation(s)
- Felix Schiele
- a New Biological Entities Discovery; Boehringer Ingelheim GmbH & Co. KG ; Biberach , Germany
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15
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Wycoff K, Maclean J, Belle A, Yu L, Tran Y, Roy C, Hayden F. Anti-infective immunoadhesins from plants. PLANT BIOTECHNOLOGY JOURNAL 2015; 13:1078-93. [PMID: 26242703 PMCID: PMC4749143 DOI: 10.1111/pbi.12441] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 06/24/2015] [Accepted: 06/27/2015] [Indexed: 05/22/2023]
Abstract
Immunoadhesins are recombinant proteins that combine the ligand-binding region of a receptor or adhesion molecule with immunoglobulin constant domains. All FDA-approved immunoadhesins are designed to modulate the interaction of a human receptor with its normal ligand, such as Etanercept (Enbrel(®) ), which interferes with the binding of tumour necrosis factor (TNF) to the TNF-alpha receptor and is used to treat inflammatory diseases such as rheumatoid arthritis. Like antibodies, immunoadhesins have long circulating half-lives, are readily purified by affinity-based methods and have the avidity advantages conferred by bivalency. Immunoadhesins that incorporate normal cellular receptors for viruses or bacterial toxins hold great, but as yet unrealized, potential for treating infectious disease. As decoy receptors, immunoadhesins have potential advantages over pathogen-targeted monoclonal antibodies. Planet Biotechnology has specialized in developing anti-infective immunoadhesins using plant expression systems. An immunoadhesin incorporating the cellular receptor for anthrax toxin, CMG2, potently blocks toxin activity in vitro and protects animals against inhalational anthrax. An immunoadhesin based on the receptor for human rhinovirus, ICAM-1, potently blocks infection of human cells by one of the major causes of the common cold. An immunoadhesin targeting the MERS coronavirus is in an early stage of development. We describe here the unique challenges involved in designing and developing immunoadhesins targeting infectious diseases in the hope of inspiring further research into this promising class of drugs.
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Affiliation(s)
| | | | | | - Lloyd Yu
- Planet Biotechnology Inc., Hayward, CA, USA
| | - Y Tran
- Planet Biotechnology Inc., Hayward, CA, USA
| | - Chad Roy
- Tulane National Primate Research Center, Covington, LA, USA
| | - Frederick Hayden
- University of Virginia School of Medicine, Charlottesville, VA, USA
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16
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Efficacy of ETI-204 monoclonal antibody as an adjunct therapy in a New Zealand white rabbit partial survival model for inhalational anthrax. Antimicrob Agents Chemother 2015; 59:2206-14. [PMID: 25645849 DOI: 10.1128/aac.04593-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inhalational anthrax is characterized by extensive bacteremia and toxemia as well as nonspecific to mild flu-like symptoms, until the onset of hypotension, shock, and mortality. Without treatment, the mortality rate approaches 100%. Antibiotic treatment is not always effective, and alternative treatments are needed, such as monotherapy for antibiotic-resistant inhalational anthrax or as an adjunct therapy in combination with antibiotics. The Bacillus anthracis antitoxin monoclonal antibody (MAb) ETI-204 is a high-affinity chimeric deimmunized antibody which targets the anthrax toxin protective antigen (PA). In this study, a partial protection New Zealand White (NZW) rabbit model was used to evaluate the protective efficacy of the adjunct therapy with the MAb. Following detection of PA in the blood, NZW rabbits were administered either an antibiotic (doxycycline) alone or the antibiotic in conjunction with ETI-204. Survival was evaluated to compare the efficacy of the combination adjunct therapy with that of an antibiotic alone in treating inhalational anthrax. Overall, the results from this study indicate that a subtherapeutic regimen consisting of an antibiotic in combination with an anti-PA MAb results in increased survival compared to the antibiotic alone and would provide an effective therapeutic strategy against symptomatic anthrax in nonvaccinated individuals.
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17
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Grada Z, Hegde M, Byrd T, Shaffer DR, Ghazi A, Brawley VS, Corder A, Schönfeld K, Koch J, Dotti G, Heslop HE, Gottschalk S, Wels WS, Baker ML, Ahmed N. TanCAR: A Novel Bispecific Chimeric Antigen Receptor for Cancer Immunotherapy. MOLECULAR THERAPY. NUCLEIC ACIDS 2013; 2:e105. [PMID: 23839099 PMCID: PMC3731887 DOI: 10.1038/mtna.2013.32] [Citation(s) in RCA: 338] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 04/16/2013] [Indexed: 12/16/2022]
Abstract
Targeted T cells are emerging as effective non-toxic therapies for cancer. Multiple elements, however, contribute to the overall pathogenesis of cancer through both distinct and redundant mechanisms. Hence, targeting multiple cancer-specific markers simultaneously could result in better therapeutic efficacy. We created a functional chimeric antigen receptor-the TanCAR, a novel artificial molecule that mediates bispecific activation and targeting of T cells. We demonstrate the feasibility of cumulative integration of structure and docking simulation data using computational tools to interrogate the design and predict the functionality of such a complex bispecific molecule. Our prototype TanCAR induced distinct T cell reactivity against each of two tumor restricted antigens, and produced synergistic enhancement of effector functions when both antigens were simultaneously encountered. Furthermore, the TanCAR preserved the cytolytic ability of T cells upon loss of one of the target molecules and better controlled established experimental tumors by recognition of both targets in an animal disease model. This proof-of-concept approach can be used to increase the specificity of effector cells for malignant versus normal target cells, to offset antigen escape or to allow for targeting the tumor and its microenvironment.Molecular Therapy-Nucleic Acids (2013) 2, e105; doi:10.1038/mtna.2013.32; published online 9 July 2013.
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Affiliation(s)
- Zakaria Grada
- 1] Center for Cell and Gene Therapy, Baylor College of Medicine, Texas Children's Hospital and The Methodist Hospital, Houston, Texas, USA [2] Texas Children's Cancer and Hematology Centers, Baylor College of Medicine, Houston, Texas, USA [3] Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
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18
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Xu J, Tack D, Hughes RA, Ellington AD, Gray JJ. Structure-based non-canonical amino acid design to covalently crosslink an antibody-antigen complex. J Struct Biol 2013; 185:215-22. [PMID: 23680795 DOI: 10.1016/j.jsb.2013.05.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 04/04/2013] [Accepted: 05/02/2013] [Indexed: 10/26/2022]
Abstract
Engineering antibodies to utilize non-canonical amino acids (NCAA) should greatly expand the utility of an already important biological reagent. In particular, introducing crosslinking reagents into antibody complementarity determining regions (CDRs) should provide a means to covalently crosslink residues at the antibody-antigen interface. Unfortunately, finding the optimum position for crosslinking two proteins is often a matter of iterative guessing, even when the interface is known in atomic detail. Computer-aided antibody design can potentially greatly restrict the number of variants that must be explored in order to identify successful crosslinking sites. We have therefore used Rosetta to guide the introduction of an oxidizable crosslinking NCAA, l-3,4-dihydroxyphenylalanine (l-DOPA), into the CDRs of the anti-protective antigen scFv antibody M18, and have measured crosslinking to its cognate antigen, domain 4 of the anthrax protective antigen. Computed crosslinking distance, solvent accessibility, and interface energetics were three factors considered that could impact the efficiency of l-DOPA-mediated crosslinking. In the end, 10 variants were synthesized, and crosslinking efficiencies were generally 10% or higher, with the best variant crosslinking to 52% of the available antigen. The results suggest that computational analysis can be used in a pipeline for engineering crosslinking antibodies. The rules learned from l-DOPA crosslinking of antibodies may also be generalizable to the formation of other crosslinked interfaces and complexes.
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Affiliation(s)
- Jianqing Xu
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Drew Tack
- Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - Randall A Hughes
- Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA; Applied Research Laboratories, The University of Texas at Austin, Austin, TX 78758, USA
| | - Andrew D Ellington
- Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA; Applied Research Laboratories, The University of Texas at Austin, Austin, TX 78758, USA.
| | - Jeffrey J Gray
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
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19
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Robinson JA. Max Bergmann lecture protein epitope mimetics in the age of structural vaccinology. J Pept Sci 2013; 19:127-40. [PMID: 23349031 PMCID: PMC3592999 DOI: 10.1002/psc.2482] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 12/18/2012] [Indexed: 11/09/2022]
Abstract
This review highlights the growing importance of protein epitope mimetics in the discovery of new biologically active molecules and their potential applications in drug and vaccine research. The focus is on folded β-hairpin mimetics, which are designed to mimic β-hairpin motifs in biologically important peptides and proteins. An ever-growing number of protein crystal structures reveal how β-hairpin motifs often play key roles in protein-protein and protein-nucleic acid interactions. This review illustrates how using protein structures as a starting point for small-molecule mimetic design can provide novel ligands as protein-protein interaction inhibitors, as protease inhibitors, and as ligands for chemokine receptors and folded RNA targets, as well as novel antibiotics to combat the growing health threat posed by the emergence of antibiotic-resistant bacteria. The β-hairpin antibiotics are shown to target a β-barrel outer membrane protein (LptD) in Pseudomonas sp., which is essential for the biogenesis of the outer cell membrane. Another exciting prospect is that protein epitope mimetics will be of increasing importance in synthetic vaccine design, in the emerging field of structural vaccinology. Crystal structures of protective antibodies bound to their pathogen-derived epitopes provide an ideal starting point for the design of synthetic epitope mimetics. The mimetics can be delivered to the immune system in a highly immunogenic format on the surface of synthetic virus-like particles. The scientific challenges in molecular design remain great, but the potential significance of success in this area is even greater.
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Affiliation(s)
- John A Robinson
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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20
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Ramesh B, Sendra VG, Cirino PC, Varadarajan N. Single-cell characterization of autotransporter-mediated Escherichia coli surface display of disulfide bond-containing proteins. J Biol Chem 2012; 287:38580-9. [PMID: 23019324 DOI: 10.1074/jbc.m112.388199] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Autotransporters (ATs) are a family of bacterial proteins containing a C-terminal β-barrel-forming domain that facilitates the translocation of N-terminal passenger domain whose functions range from adhesion to proteolysis. Genetic replacement of the native passenger domain with heterologous proteins is an attractive strategy not only for applications such as biocatalysis, live-cell vaccines, and protein engineering but also for gaining mechanistic insights toward understanding AT translocation. The ability of ATs to efficiently display functional recombinant proteins containing multiple disulfides has remained largely controversial. By employing high-throughput single-cell flow cytometry, we have systematically investigated the ability of the Escherichia coli AT Antigen 43 (Ag43) to display two different recombinant reporter proteins, a single-chain antibody (M18 scFv) that contains two disulfides and chymotrypsin that contains four disulfides, by varying the signal peptide and deleting the different domains of the native protein. Our results indicate that only the C-terminal β-barrel and the threaded α-helix are essential for efficient surface display of functional recombinant proteins containing multiple disulfides. These results imply that there are no inherent constraints for functional translocation and display of disulfide bond-containing proteins mediated by the AT system and should open new avenues for protein display and engineering.
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Affiliation(s)
- Balakrishnan Ramesh
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, USA
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21
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Im H, Sutherland JN, Maynard JA, Oh SH. Nanohole-based surface plasmon resonance instruments with improved spectral resolution quantify a broad range of antibody-ligand binding kinetics. Anal Chem 2012; 84:1941-7. [PMID: 22235895 DOI: 10.1021/ac300070t] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We demonstrate an affordable low-noise surface plasmon resonance (SPR) instrument based on extraordinary optical transmission (EOT) in metallic nanohole arrays and quantify a broad range of antibody-ligand binding kinetics with equilibrium dissociation constants ranging from 200 pM to 40 nM. This nanohole-based SPR instrument is straightforward to construct, align, and operate, since it is built around a standard microscope and a portable fiber-optic spectrometer. The measured refractive index resolution of this platform is 3.1 × 10(-6) without on-chip cooling, which is among the lowest reported for SPR sensors based on EOT. This is accomplished via rapid full-spectrum acquisition in 10 ms followed by frame averaging of the EOT spectra, which is made possible by the production of template-stripped gold nanohole arrays with homogeneous optical properties over centimeter-sized areas. Sequential SPR measurements are performed using a 12-channel microfluidic flow cell after optimizing surface modification protocols and antibody injection conditions to minimize mass-transport artifacts. The immobilization of a model ligand, the protective antigen of anthrax on the gold surface, is monitored in real-time with a signal-to-noise ratio of ~860. Subsequently, real-time binding kinetic curves were measured quantitatively between the antigen and a panel of small, 25 kDa single-chain antibodies at concentrations down to 1 nM. These results indicate that nanohole-based SPR instruments have potential for quantitative antibody screening and as a general-purpose platform for integrating SPR sensors with other bioanalytical tools.
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Affiliation(s)
- Hyungsoon Im
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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22
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O'Hara JM, Yermakova A, Mantis NJ. Immunity to ricin: fundamental insights into toxin-antibody interactions. Curr Top Microbiol Immunol 2012; 357:209-41. [PMID: 22113742 PMCID: PMC4433546 DOI: 10.1007/82_2011_193] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ricin toxin is an extraordinarily potent inducer of cell death and inflammation. Ricin is also a potent provocateur of the humoral immune system, eliciting a mixture of neutralizing, non-neutralizing and even toxin-enhancing antibodies. The characterization of dozens of monoclonal antibodies (mAbs) against the toxin's enzymatic (RTA) and binding (RTB) subunits has begun to reveal fundamental insights into the underlying mechanisms by which antibodies neutralize (or fail to neutralize) ricin in systemic and mucosal compartments. This information has had immediate applications in the design, development and evaluation of ricin subunit vaccines and immunotherapeutics.
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Affiliation(s)
- Joanne M. O'Hara
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, 120 New Scotland Avenue, Albany, NY 12208, USA; Department of Biomedical Sciences, University at Albany School of Public Health, Albany, NY 12201, USA
| | - Anastasiya Yermakova
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, 120 New Scotland Avenue, Albany, NY 12208, USA; Department of Biomedical Sciences, University at Albany School of Public Health, Albany, NY 12201, USA
| | - Nicholas J. Mantis
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, 120 New Scotland Avenue, Albany, NY 12208, USA; Department of Biomedical Sciences, University at Albany School of Public Health, Albany, NY 12201, USA
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23
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In situ gastrointestinal protection against anthrax edema toxin by single-chain antibody fragment producing lactobacilli. BMC Biotechnol 2011; 11:126. [PMID: 22185669 PMCID: PMC3295704 DOI: 10.1186/1472-6750-11-126] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 12/20/2011] [Indexed: 11/10/2022] Open
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24
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Canul-Tec JC, Riaño-Umbarila L, Rudiño-Piñera E, Becerril B, Possani LD, Torres-Larios A. Structural basis of neutralization of the major toxic component from the scorpion Centruroides noxius Hoffmann by a human-derived single-chain antibody fragment. J Biol Chem 2011; 286:20892-900. [PMID: 21489992 PMCID: PMC3121463 DOI: 10.1074/jbc.m111.238410] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 03/30/2011] [Indexed: 11/06/2022] Open
Abstract
It has previously been reported that several single-chain antibody fragments of human origin (scFv) neutralize the effects of two different scorpion venoms through interactions with the primary toxins of Centruroides noxius Hoffmann (Cn2) and Centruroides suffusus suffusus (Css2). Here we present the crystal structure of the complex formed between one scFv (9004G) and the Cn2 toxin, determined in two crystal forms at 2.5 and 1.9 Å resolution. A 15-residue span of the toxin is recognized by the antibody through a cleft formed by residues from five of the complementarity-determining regions of the scFv. Analysis of the interface of the complex reveals three features. First, the epitope of toxin Cn2 overlaps with essential residues for the binding of β-toxins to its Na(+) channel receptor site. Second, the putative recognition of Css2 involves mainly residues that are present in both Cn2 and Css2 toxins. Finally, the effect on the increase of affinity of previously reported key residues during the maturation process of different scFvs can be inferred from the structure. Taken together, these results provide the structural basis that explain the mechanism of the 9004G neutralizing activity and give insight into the process of directed evolution that gave rise to this family of neutralizing scFvs.
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Affiliation(s)
- Juan Carlos Canul-Tec
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Lidia Riaño-Umbarila
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Enrique Rudiño-Piñera
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Baltazar Becerril
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Lourival D. Possani
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Alfredo Torres-Larios
- the Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Apartado postal 70-243, Mexico City 04510, México
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25
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Vaccination of rhesus macaques with the anthrax vaccine adsorbed vaccine produces a serum antibody response that effectively neutralizes receptor-bound protective antigen in vitro. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2010; 17:1753-62. [PMID: 20739500 DOI: 10.1128/cvi.00174-10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Anthrax toxin (ATx) is composed of the binary exotoxins lethal toxin (LTx) and edema toxin (ETx). They have separate effector proteins (edema factor and lethal factor) but have the same binding protein, protective antigen (PA). PA is the primary immunogen in the current licensed vaccine anthrax vaccine adsorbed (AVA [BioThrax]). AVA confers protective immunity by stimulating production of ATx-neutralizing antibodies, which could block the intoxication process at several steps (binding of PA to the target cell surface, furin cleavage, toxin complex formation, and binding/translocation of ATx into the cell). To evaluate ATx neutralization by anti-AVA antibodies, we developed two low-temperature LTx neutralization activity (TNA) assays that distinguish antibody blocking before and after binding of PA to target cells (noncomplexed [NC] and receptor-bound [RB] TNA assays). These assays were used to investigate anti-PA antibody responses in AVA-vaccinated rhesus macaques (Macaca mulatta) that survived an aerosol challenge with Bacillus anthracis Ames spores. Results showed that macaque anti-AVA sera neutralized LTx in vitro, even when PA was prebound to cells. Neutralization titers in surviving versus nonsurviving animals and between prechallenge and postchallenge activities were highly correlated. These data demonstrate that AVA stimulates a myriad of antibodies that recognize multiple neutralizing epitopes and confirm that change, loss, or occlusion of epitopes after PA is processed from PA83 to PA63 at the cell surface does not significantly affect in vitro neutralizing efficacy. Furthermore, these data support the idea that the full-length PA83 monomer is an appropriate immunogen for inclusion in next-generation anthrax vaccines.
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26
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Anthrax toxin-neutralizing antibody reconfigures the protective antigen heptamer into a supercomplex. Proc Natl Acad Sci U S A 2010; 107:14070-4. [PMID: 20660775 DOI: 10.1073/pnas.1006473107] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The tripartite protein exotoxin secreted by Bacillus anthracis, a major contributor to its virulence and anthrax pathogenesis, consists of binary complexes of the protective antigen (PA) heptamer (PA63h), produced by proteolytic cleavage of PA, together with either lethal factor or edema factor. The mouse monoclonal anti-PA antibody 1G3 was previously shown to be a potent antidote that shares F(C) domain dependency with the human monoclonal antibody MDX-1303 currently under clinical development. Here we demonstrate that 1G3 instigates severe perturbation of the PA63h structure and creates a PA supercomplex as visualized by electron microscopy. This phenotype, produced by the unconventional mode of antibody action, highlights the feasibility for optimization of vaccines based on analogous structural modification of PA63h as an additional strategy for future remedies against anthrax.
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27
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Malik A, Firoz A, Jha V, Sunderasan E, Ahmad S. Modeling the three-dimensional structures of an unbound single-chain variable fragment (scFv) and its hypothetical complex with a Corynespora cassiicola toxin, cassiicolin. J Mol Model 2010; 16:1883-93. [DOI: 10.1007/s00894-010-0680-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 01/26/2010] [Indexed: 02/02/2023]
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28
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Neutralizing monoclonal antibodies directed against defined linear epitopes on domain 4 of anthrax protective antigen. Infect Immun 2009; 77:4859-67. [PMID: 19703971 DOI: 10.1128/iai.00117-09] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The anthrax protective antigen (PA) is the receptor-binding subunit common to lethal toxin (LT) and edema toxin (ET), which are responsible for the high mortality rates associated with inhalational Bacillus anthracis infection. Although recombinant PA (rPA) is likely to be an important constituent of any future anthrax vaccine, evaluation of the efficacies of the various candidate rPA vaccines is currently difficult, because the specific B-cell epitopes involved in toxin neutralization have not been completely defined. In this study, we describe the identification and characterization of two murine monoclonal immunoglobulin G1 antibodies (MAbs), 1-F1 and 2-B12, which recognize distinct linear neutralizing epitopes on domain 4 of PA. 1-F1 recognized a 12-mer peptide corresponding to residues 692 to 703; this epitope maps to a region of domain 4 known to interact with the anthrax toxin receptor CMG-2 and within a conformation-dependent epitope recognized by the well-characterized neutralizing MAb 14B7. As expected, 1-F1 blocked PA's ability to associate with CMG-2 in an in vitro solid-phase binding assay, and it protected murine macrophage cells from intoxication with LT. 2-B12 recognized a 12-mer peptide corresponding to residues 716 to 727, an epitope located immediately adjacent to the core 14B7 binding site and a stretch of amino acids not previously identified as a target of neutralizing antibodies. 2-B12 was as effective as 1-F1 in neutralizing LT in vitro, although it only partially inhibited PA binding to its receptor. Mice passively administered 1-F1 or 2-B12 were partially protected against a lethal challenge with LT. These results advance our fundamental understanding of the mechanisms by which antibodies neutralize anthrax toxin and may have future application in the evaluation of candidate rPA vaccines.
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