1
|
Liu W, Zhao W, Bai X, Jin S, Li Y, Qiu C, Pan L, Ding D, Xu Y, Zhou Z, Chen S. High antitumor activity of Sortase A-generated anti-CD20 antibody fragment drug conjugates. Eur J Pharm Sci 2019; 134:81-92. [DOI: 10.1016/j.ejps.2019.04.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 03/27/2019] [Accepted: 04/11/2019] [Indexed: 12/29/2022]
|
2
|
Heterogeneity of auto-antibodies against nAChR in myasthenic serum and their pathogenic roles in experimental autoimmune myasthenia gravis. J Neuroimmunol 2018; 320:64-75. [PMID: 29759142 DOI: 10.1016/j.jneuroim.2018.04.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/23/2018] [Accepted: 04/23/2018] [Indexed: 11/20/2022]
Abstract
Many myasthenia gravis (MG) patients have auto-antibodies against the nicotinic acetylcholine receptor (nAChR), and monoclonal antibodies against the main immunogenic region (MIR) of nAChR can induce experimental autoimmune MG (EAMG). We investigated whether Fab fragment of MIR antibody (Fab35) could block the pathogenicity of polyclonal antibodies. Fab35 partially inhibited nAChR downmodulation, blocked EAMG serum-induced binding of polyclonal antibodies and complement deposition in vitro. Moreover, Fab35 did not ameliorate the EAMG serum-induced EAMG phenotype in rats. These results suggested that the EAMG serum possessed several different pathogenic antibodies that might be sufficient to induce the EAMG phenotype.
Collapse
|
3
|
Song C, Xu Z, Miao J, Xu J, Wu X, Zhang F, Lin H, Li Z, Kaminski HJ. Protective effect of scFv-DAF fusion protein on the complement attack to acetylcholine receptor: a possible option for treatment of myasthenia gravis. Muscle Nerve 2012; 45:668-675. [PMID: 22499093 DOI: 10.1002/mus.23247] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
INTRODUCTION Autoantibody-induced complement activation, which causes disruption of the postsynaptic membrane, is recognized as a key pathogenic factor in myasthenia gravis (MG). Therefore, specific targeting of complement inhibitors to the site of complement activation is a potential therapeutic strategy for treatment of MG. METHODS We assessed expression of single-chain antibody fragment-decay accelerating factor (scFv-DAF), comprising a single-chain fragment scFv1956 based on the rat complement inhibitor DAF in prokaryotic systems, and studied its inhibitory effect on complement deposition in vitro. RESULTS The recombinant conjugate scFv-DAF completely retained the wild-type binding activity of scFv1956 to AChR and inhibited complement activation of DAF in vitro. CONCLUSIONS We found that scFv-DAF could bind specifically to TE671 cells, and it is significantly more potent at inhibiting complement deposition than the untargeted parent molecule DAF. scFv-DAF may be a candidate for in vivo protection of the AChR in MG.
Collapse
Affiliation(s)
- Chen Song
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Zhikai Xu
- Department of Microbiology, Fourth Military Medical University, Xi'an, China
| | - Jianting Miao
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Jiang Xu
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Xingan Wu
- Department of Microbiology, Fourth Military Medical University, Xi'an, China
| | - Fanglin Zhang
- Department of Microbiology, Fourth Military Medical University, Xi'an, China
| | - Hong Lin
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Zhuyi Li
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Henry J Kaminski
- Department of Neurology, George Washington University, 2150 Pennsylvania Avenue NW, Suite 7-406, Washington, DC 20037, USA
| |
Collapse
|
4
|
Chen Y, Zhu X, Zhang X, Liu B, Huang L. Nanoparticles modified with tumor-targeting scFv deliver siRNA and miRNA for cancer therapy. Mol Ther 2010; 18:1650-6. [PMID: 20606648 DOI: 10.1038/mt.2010.136] [Citation(s) in RCA: 385] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Targeted delivery of RNA-based therapeutics for cancer therapy remains a challenge. We have developed a LPH (liposome-polycation-hyaluronic acid) nanoparticle formulation modified with tumor-targeting single-chain antibody fragment (scFv) for systemic delivery of small interfering RNA (siRNA) and microRNA (miRNA) into experimental lung metastasis of murine B16F10 melanoma. The siRNAs delivered by the scFv targeted nanoparticles efficiently downregulated the target genes (c-Myc/MDM2/VEGF) in the lung metastasis. Two daily intravenous injections of the combined siRNAs in the GC4-targeted nanoparticles significantly reduced the tumor load in the lung. miRNA-34a (miR-34a) induced apoptosis, inhibited survivin expression, and downregulated MAPK pathway in B16F10 cells. miR-34a delivered by the GC4-targeted nanoparticles significantly downregulated the survivin expression in the metastatic tumor and reduced tumor load in the lung. When miR-34a and siRNAs were co-formulated in GC4-targeted nanoparticles, an enhanced anticancer effect was observed.
Collapse
Affiliation(s)
- Yunching Chen
- Division of Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | | | | | | | | |
Collapse
|
5
|
Lagoumintzis G, Zisimopoulou P, Kordas G, Lazaridis K, Poulas K, Tzartos SJ. Recent approaches to the development of antigen-specific immunotherapies for myasthenia gravis. Autoimmunity 2010; 43:436-45. [DOI: 10.3109/08916930903518099] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
6
|
Gattenlöhner S, Jörißen H, Huhn M, Vincent A, Beeson D, Tzartos S, Mamalaki A, Etschmann B, Muller-Hermelink HK, Koscielniak E, Barth S, Marx A. A human recombinant autoantibody-based immunotoxin specific for the fetal acetylcholine receptor inhibits rhabdomyosarcoma growth in vitro and in a murine transplantation model. J Biomed Biotechnol 2010; 2010:187621. [PMID: 20204062 PMCID: PMC2829619 DOI: 10.1155/2010/187621] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 11/18/2009] [Indexed: 11/28/2022] Open
Abstract
Rhabdomyosarcoma (RMS) is the most common malignant soft tissue tumor in children and is highly resistant to all forms of treatment currently available once metastasis or relapse has commenced. As it has recently been determined that the acetylcholine receptor (AChR) gamma-subunit, which defines the fetal AChR (fAChR) isoform, is almost exclusively expressed in RMS post partum, we recombinantly fused a single chain variable fragment (scFv) derived from a fully human anti-fAChR Fab-fragment to Pseudomonas exotoxin A to generate an anti-fAChR immunotoxin (scFv35-ETA). While scFv35-ETA had no damaging effect on fAChR-negative control cell lines, it killed human embryonic and alveolar RMS cell lines in vitro and delayed RMS development in a murine transplantation model. These results indicate that scFv35-ETA may be a valuable new therapeutic tool as well as a relevant step towards the development of a fully human immunotoxin directed against RMS. Moreover, as approximately 20% of metastatic malignant melanomas (MMs) display rhabdoid features including the expression of fAChR, the immunotoxin we developed may also prove to be of significant use in the treatment of these more common and most often fatal neoplasms.
Collapse
Affiliation(s)
- S. Gattenlöhner
- Institute of Pathology, University of Würzburg, 97080 Würzburg, Germany
| | - H. Jörißen
- Department of Pharmaceutical Product Development, Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstraße 6, 52074 Aachen, Germany
| | - M. Huhn
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, University of Oxford, OX3 9DU Oxford, UK
| | - A. Vincent
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, University of Oxford, OX3 9DU Oxford, UK
| | - D. Beeson
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, University of Oxford, OX3 9DU Oxford, UK
| | - S. Tzartos
- Hellenic Pasteur Institute, 127, Vas. Sofias Avenue 11521, Athens, Greece
| | - A. Mamalaki
- Hellenic Pasteur Institute, 127, Vas. Sofias Avenue 11521, Athens, Greece
| | - B. Etschmann
- Institute of Pathology, University of Würzburg, 97080 Würzburg, Germany
| | | | - E. Koscielniak
- Department of Pediatric Oncology, Olga Hospital, 70176 Stuttgart, Germany
| | - S. Barth
- Department of Pharmaceutical Product Development, Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstraße 6, 52074 Aachen, Germany
- Department of Experimental Medicine and Immunotherapy, Helmholtz-Institute for Biomedical Engineering, University Hospital RWTH Aachen, Pauwelsstraße 20, 52074 Aachen, Germany
| | - A. Marx
- Institute of Pathology, University of Würzburg, 97080 Würzburg, Germany
- Institute of Pathology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68135 Mannheim, Greece
| |
Collapse
|
7
|
Demirtzoglou FJ, Papadopoulos S, Zografos G. Cytolytic and Cytotoxic Activity of a Human Natural Killer Cell Line Genetically Modified to Specifically Recognize HER-2/neu Overexpressing Tumor Cells. Immunopharmacol Immunotoxicol 2008; 28:571-90. [PMID: 17190735 DOI: 10.1080/08923970601066971] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
NK92 cells genetically engineered to recognize the HER-2/neu oncoprotein have been previously reported to lyse HER-2/neu positive tumor cell lines through direct cell to cell contact. In the present study we have transduced NK92 cells with a chimeric receptor gene composed of the HER-/neu specific scFv (FRP5) antibody fragment, joined to the peptide CD8 hinge region and the signaling CD3 zeta chain. NK92 cells expressing this chimeric receptor (NK92.HER-2/neu/zeta) specifically recognized and lysed HER-2/neu overexpressing tumor cell lines both in vitro and in preclinical tumor models in vivo. More important we demonstrate that NK92.HER-2/neu/zeta cells constitutively secrete high levels of soluble scFv which mediate strong tumor cytostatic effects by directly binding on cell surface HER-2/neu. Our data uncover an additional mechanism through which NK92.HER-2/neu/zeta cells mediate antitumor effects and further support their use in cell based therapeutics for the treatment of HER-2/neu expressing cancers.
Collapse
MESH Headings
- Animals
- Antibodies, Monoclonal/biosynthesis
- Antibodies, Monoclonal/genetics
- Blotting, Western
- CD3 Complex/genetics
- Cell Line, Tumor
- Cell Proliferation
- Cell Survival
- Exotoxins/genetics
- Female
- Fluorescent Antibody Technique
- Humans
- Killer Cells, Natural/physiology
- Mice
- Mice, SCID
- Neoplasms/metabolism
- Neoplasms/pathology
- Organisms, Genetically Modified
- Receptor, ErbB-2/biosynthesis
- Receptor, ErbB-2/genetics
- Recombinant Fusion Proteins/genetics
- Single-Chain Antibodies
- T-Lymphocytes, Cytotoxic/physiology
- Transduction, Genetic
Collapse
Affiliation(s)
- F J Demirtzoglou
- Cancer Immunology and Immunotherapy Center, Saint Savas Cancer Hospital, Athens, Greece.
| | | | | |
Collapse
|
8
|
Gritzapis AD, Mamalaki A, Kretsovali A, Papamatheakis J, Belimezi M, Perez SA, Baxevanis CN, Papamichail M. Redirecting mouse T hybridoma against human breast and ovarian carcinomas: in vivo activity against HER-2/neu expressing cancer cells. Br J Cancer 2003; 88:1292-300. [PMID: 12698199 PMCID: PMC2747561 DOI: 10.1038/sj.bjc.6600888] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Chimeric receptors comprising of the T-cell receptor-zeta cytoplasmic signalling chain fused to an extracellular ligand-binding domain of a single-chain antibody (scFv) have served as effective tools for redirecting cytotoxic T lymphocytes (CTL) against tumour cells. In this report, we constructed a chimeric scFv/zeta gene composed of the variable regions of an HER-2/neu-specific monoclonal antibody (MAb) joined to the TCR-zeta chain. The scFv(anti-HER-2/neu)/zeta chimeric gene was successfully expressed as a functional surface receptor in the MD.45 CTL hybridoma (MD.45-HER/zeta). More importantly, the scFv(anti-HER-2/neu)/zeta receptor was functionally active, since it triggered cytokine secretion by the MD.45-HER/zeta cells upon recognition of HER-2/neu-positive (+) tumour cell lines, or primary tumour cells from patients with HER-2/neu(+) cancers. The MD.45-HER/zeta-transduced cells also lysed HER-2/neu(+) target cells in vitro with high specificity. We tested the antitumour efficacy of scFv(anti-HER-2/neu)/zeta expressing MD.45 cells in severe combined immunodeficiency disease mice/human and murine tumour models. The adoptively transferred MD.45-HER/zeta cells both slowed significantly the growth of human FM3 melanoma or murine ALC leukaemic cells both transfected to express HER-2/neu. Our data demonstrate the feasibility of redirecting MD.45 CTL with the scFv(anti-HER-2/neu)/zeta chimeric receptor to respond specifically against HER-2/neu expressing tumour cells in vitro and in vivo. Moreover, they make it likely that T cells transduced with the same chimeric gene might be utilised in the treatment of patients with HER-2/neu(+) tumours.
Collapse
Affiliation(s)
- A D Gritzapis
- Saint Savas Cancer Hospital, Cancer Immunology and Immunotherapy Center, 171 Alexandras Ave, 11522 Athens, Greece
| | - A Mamalaki
- Department of Biochemistry, Hellenic Pasteur Institute, Athens, Greece
| | - A Kretsovali
- Foundation for Research and Technology, Institute of Molecular Biology and Biotechnology, Heraklion, Crete
| | - J Papamatheakis
- Foundation for Research and Technology, Institute of Molecular Biology and Biotechnology, Heraklion, Crete
| | - M Belimezi
- Department of Biochemistry, Hellenic Pasteur Institute, Athens, Greece
| | - S A Perez
- Saint Savas Cancer Hospital, Cancer Immunology and Immunotherapy Center, 171 Alexandras Ave, 11522 Athens, Greece
| | - C N Baxevanis
- Saint Savas Cancer Hospital, Cancer Immunology and Immunotherapy Center, 171 Alexandras Ave, 11522 Athens, Greece
- Saint Savas Cancer Hospital, Cancer Immunology and Immunotherapy Center, 171 Alexandras Ave, 11522 Athens, Greece. E-mail:
| | - M Papamichail
- Saint Savas Cancer Hospital, Cancer Immunology and Immunotherapy Center, 171 Alexandras Ave, 11522 Athens, Greece
| |
Collapse
|
9
|
Trakas N, Tzartos SJ. Conjugation of acetylcholine receptor-protecting Fab fragments with polyethylene glycol results in a prolonged half-life in the circulation and reduced immunogenicity. J Neuroimmunol 2001; 120:42-9. [PMID: 11694318 DOI: 10.1016/s0165-5728(01)00405-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Antibodies to the acetylcholine receptor (AChR) cause AChR loss, resulting in the disease, myasthenia gravis (MG). The majority of the pathogenic antibodies seem to be directed against the main immunogenic region (MIR) of the AChR. In contrast to the intact antibodies, Fab fragments of anti-AChR antibodies are not themselves pathogenic and such fragments of anti-MIR monoclonal antibodies (mAbs) protect the AChR in vitro and in vivo against the pathogenic antibodies. However, Fab fragments have a very short in vivo half-life and are immunogenic, obstacles which must be overcome before their clinical use can be envisaged. We investigated the effect of conjugating Fab fragments to polyethylene glycol (PEG), a method known to increase the in vivo half-life and reduce the immunogenicity of proteins. When the Fab' fragments of two rat anti-MIR mAbs (nos. 35 and 195) were conjugated to methoxy-PEG-maleimide, the conjugates retained about 10% of their AChR binding activity and efficiently protected the AChR against the binding and modulating activity of myasthenic antibodies. Their in vivo half-life in rats was approximately 15 times longer than that of the unconjugated Fab' fragment and they were much less immunogenic in mice. This work represents an important step towards the clinical use of AChR-protective anti-MIR Fabs, but further improvements are needed before their clinical use is attempted.
Collapse
MESH Headings
- Animals
- Antibodies, Monoclonal/pharmacology
- Autoantibodies/chemistry
- Autoantibodies/immunology
- Binding, Competitive/drug effects
- Binding, Competitive/immunology
- Half-Life
- Immunoglobulin Fab Fragments/chemistry
- Immunoglobulin Fab Fragments/immunology
- Immunoglobulin Fab Fragments/pharmacology
- Mice
- Mice, Inbred BALB C
- Myasthenia Gravis/drug therapy
- Myasthenia Gravis/immunology
- Myasthenia Gravis/physiopathology
- Neuroprotective Agents/chemical synthesis
- Neuroprotective Agents/metabolism
- Polyethylene Glycols/chemical synthesis
- Polyethylene Glycols/metabolism
- Receptors, Cholinergic/drug effects
- Receptors, Cholinergic/immunology
- Receptors, Cholinergic/metabolism
- Tumor Cells, Cultured/drug effects
- Tumor Cells, Cultured/immunology
- Tumor Cells, Cultured/metabolism
- Vaccines, Synthetic/chemistry
- Vaccines, Synthetic/immunology
- Vaccines, Synthetic/pharmacology
Collapse
Affiliation(s)
- N Trakas
- Department of Biochemistry, Hellenic Pasteur Institute, 127 Vas. Sofias Avenue, Athens 115 21, Greece
| | | |
Collapse
|
10
|
Affiliation(s)
- V N Krasnykh
- Departments of Medicine, Pathology, and Surgery, Division of Human Gene Therapy and Gene Therapy Center, University of Alabama at Birmingham, 1824 Sixth Avenue South, Birmingham, Alabama 35294, USA.
| | | | | |
Collapse
|
11
|
Papanastasiou D, Poulas K, Kokla A, Tzartos SJ. Prevention of passively transferred experimental autoimmune myasthenia gravis by Fab fragments of monoclonal antibodies directed against the main immunogenic region of the acetylcholine receptor. J Neuroimmunol 2000; 104:124-32. [PMID: 10713351 DOI: 10.1016/s0165-5728(99)00259-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The muscle acetylcholine receptor loss, responsible for the clinical symptoms of myasthenia gravis, is due mainly to mechanisms dependent on the bivalent character of the anti-receptor antibodies. In cell culture, univalent Fab fragments of monoclonal antibodies (mAbs) directed against the main immunogenic region (MIR) of the acetylcholine receptor are able to protect the receptor against the action of the intact antibodies. To investigate the potential therapeutic use of this approach, we examined the ability of the Fab fragment of anti-MIR mAb195 (Fab195) to protect the receptor in vivo against two anti-MIR mAbs. Because of the rapid clearance of Fab fragments from the circulation, Lewis rats were treated repeatedly with Fab195. The Fab fragment significantly protected muscle receptors against antibody-mediated loss and was very efficient in providing protection against clinical symptoms when its administration was commenced before, simultaneously with, or 2 h after, mAb injection. Twenty-four hours after mAb injection, the protected rats only showed mild myasthenic symptoms, whereas those which only received intact antibodies were moribund or dead. These results suggest that, once modified to ensure their low immunogenicity and a long half-life, anti-MIR Fab fragments might be useful in the specific immunotherapy of myasthenia gravis.
Collapse
MESH Headings
- Animals
- Antibodies, Monoclonal/pharmacology
- Antibodies, Monoclonal/therapeutic use
- Dose-Response Relationship, Drug
- Female
- Immunoglobulin Fab Fragments/pharmacology
- Immunoglobulin Fab Fragments/therapeutic use
- Immunoglobulin Variable Region/drug effects
- Immunoglobulin Variable Region/immunology
- Myasthenia Gravis, Autoimmune, Experimental/immunology
- Myasthenia Gravis, Autoimmune, Experimental/metabolism
- Myasthenia Gravis, Autoimmune, Experimental/prevention & control
- Rats
- Rats, Inbred Lew
- Receptors, Cholinergic/drug effects
- Receptors, Cholinergic/immunology
- Time Factors
Collapse
Affiliation(s)
- D Papanastasiou
- Department of Biochemistry, Hellenic Pasteur Institute, 127 Vas. Sofias Avenue, Athens, Greece
| | | | | | | |
Collapse
|
12
|
Kontou M, Leonidas DD, Vatzaki EH, Tsantili P, Mamalaki A, Oikonomakos NG, Acharya KR, Tzartos SJ. The crystal structure of the Fab fragment of a rat monoclonal antibody against the main immunogenic region of the human muscle acetylcholine receptor. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:2389-97. [PMID: 10759865 DOI: 10.1046/j.1432-1327.2000.01252.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The crystal structure of the Fab fragment of a rat monoclonal antibody, number 192, with a very high affinity (Kd = 0.05 nM) for the main immunogenic region of the human muscle acetylcholine receptor (AChR), has been determined and refined to 2.4 A resolution by X-ray crystallographic methods. The overall structure is similar to a Fab (NC6.8) from a murine antibody, used as a search model in molecular replacement. Structural comparisons with known antibody structures showed that the conformations of the hypervariable regions H1, H2, L1, L2, L3 of Fab192 adopt the canonical structures 1, 1, 2, 1, and 1, respectively. The surface of the antigen-binding site is relatively planar, as expected for an antibody against a large protein antigen, with an accessible area of 2865 A2. Analysis of the electrostatic surface potential of the antigen-binding site shows that the bottom of the cleft formed in the center of the site appears to be negatively charged. The structure will be useful in the rational design of very high affinity humanized mutants of Fab192, appropriate for therapeutic approaches of the model autoimmune disease myasthenia gravis.
Collapse
Affiliation(s)
- M Kontou
- Department of Biochemistry, Hellenic Pasteur Institute, Athens, Greece
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Abstract
Much progress has been made in the 26 years since initial studies of the first purified acetylcholine receptors (AChRs) led to the discovery that an antibody-mediated autoimmune response to AChRs causes the muscular weakness and fatigability characteristic of myasthenia gravis (MG) and its animal model, experimental autoimmune myasthenia gravis (EAMG). Now, the structure of muscle AChRs is much better known. Monoclonal antibodies to muscle AChRs, developed as model autoantibodies for studies of EAMG, were used for initial purifications of neuronal AChRs, and now many homologous subunits of neuronal nicotinic AChRs have been cloned. There is a basic understanding of the pathological mechanisms by which autoantibodies to AChRs impair neuromuscular transmission. Immunodiagnostic assays for MG are used routinely. Nonspecific approaches to immunosuppressive therapy have been refined. However, fundamental mysteries remain regarding what initiates and sustains the autoimmune response to muscle AChRs and how to specifically suppress this autoimmune response using a practical therapy. Many rare congenital myasthenic syndromes have been elegantly shown to result from mutations in muscle AChRs. These studies have provided insights into AChR structure and function as well as into the pathological mechanisms of these diseases. Evidence has been found for autoimmune responses even to some central nervous system neurotransmitter receptors, but only one neuronal AChR has so far been implicated in an autoimmune disease. Thus far, only two neuronal AChR mutations have been found to be associated with a rare form of epilepsy, but many more neuronal AChR mutations will probably be found to be associated with disease in the years ahead.
Collapse
Affiliation(s)
- J M Lindstrom
- Department of Neuroscience, Medical School of the University of Pennsylvania, Philadelphia, Pennsylvania 19104-6074, USA.
| |
Collapse
|