Special Issue "Recombinant Immunotoxins"

Quicklinks

A special issue of Antibodies (ISSN 2073-4468).

Deadline for manuscript submissions: closed (30 November 2012)

Special Issue Editors

Guest Editor
Prof. Dr. Itai Benhar (Website)

Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
Phone: 972-3-6407511
Interests: monoclonal antibodies; recombinant antibodies; bispecific antibodies; antibody selection strategies; phage display; antibody humanization; targeted phage nanomedicines; antibody based biosensors; analysis of antibody repertoires by next-generation sequencing and proteomic approaches; protease-activated toxins; cytotoxic enzymes
Guest Editor
Prof. Dr. Stefan Barth (Website)

Fraunhofer IME-MB, Forckenbeckstr. 6, 52074 Aachen, Germany
Interests: monoclonal antibodies; recombinant antibody formats; phage display; immunization strategies; EBV transformation; antibody selection strategies; humanization strategies; cell surface antigens: CD7, CD25, CD30, CD33, CD38, CD64, C123, c-kit receptor; EGF receptor; cytotoxic enzymes

Special Issue Information

Dear Colleagues,

Immunotoxins comprise a field in targeted cancer therapeutics. These chimeric proteins are a form of biological guided missiles that combine a disease-specific targeting moiety with a potent effector molecule. The targeting moiety is mostly a monoclonal antibody or a recombinant antibody based fragment that confers target specificity to the immunotoxin. The effector domain is in most cases a potent protein toxin of bacterial or plant origin. Notwithstanding, immunotoxins targeted by non-antibody molecules do exist as well as immunotoxins where the effector domain is derived from a human enzyme including RNAses, proteases or kinases. Following binding to the target cells, the immunotoxin undergoes internalization, intracellular processing and trafficking and eventually causes cell death by either catalytically inhibiting a vital process and/or by activating a cell-death cascade. Over the 25 some years of their evolution, immunotoxins have been engineered to better fit to their purpose, improving on specificity and reducing undesirable properties such as untoward toxicities and immunogenicity. Many immunotoxins have undergone clinical evaluation, some showing promise and progressing to advanced clinical trials. This special issue of “Antibodies” will review recent developments as reported by experts in this exciting field. Covered topics will include target selection, toxin selection, targeting moiety selection and engineering, disease models and preclinical studies, clinical studies as well as adverse effects.

Prof. Dr. Itai Benhar
Prof. Dr. Dr. Stefan Barth
Guest Editors

Keywords

  • pseudomonas exotoxin
  • diphtheria toxin
  • ricin
  • Saporin
  • other RIPs
  • human enzymes
  • RNAses
  • immunotoxin targets
  • IgGs
  • antibody fragments
  • non-antibody-based disease models and preclinical studies
  • clinical studies
  • adverse effects

Published Papers (9 papers)

View options order results:
result details:
Displaying articles 1-9
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Dissecting the Entry Route of Saporin-based a-CD7 Immunotoxins in Human T-Cell Acute Lymphoblastic Leukaemia Cells
Antibodies 2013, 2(1), 50-65; doi:10.3390/antib2010050
Received: 26 November 2012 / Revised: 31 December 2012 / Accepted: 7 January 2013 / Published: 16 January 2013
PDF Full-text (457 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Elucidating the intracellular fate(s) of targeted toxins is of fundamental importance for their optimal use as anticancer drugs, since the biochemical targets of their enzymatic activity reside in the cell cytoplasm, as in the case of the plant ribosome inactivating proteins (RIP) [...] Read more.
Elucidating the intracellular fate(s) of targeted toxins is of fundamental importance for their optimal use as anticancer drugs, since the biochemical targets of their enzymatic activity reside in the cell cytoplasm, as in the case of the plant ribosome inactivating proteins (RIP) saporin, ricin and of bacterial toxins. In this paper, we compared the cell surface binding and cytotoxic properties of the model RIP ricin to an immunotoxin constructed with a monoclonal antibody directed against the human T-cell marker CD7 covalently linked to saporin (CD7-SAP). Our results indicate that, despite the fact that internalization takes place via an apparently common entry route leading to the Golgi complex, surprisingly, the addition of an endoplasmic reticulum retrieval C-terminal signal (KDEL) to CD7-SAP does not potentiate its cytotoxicity. In addition, while ricin toxicity is clearly reduced by Brefeldin A under conditions where this fungal metabolite causes Golgi stack disruption, we paradoxically observed a potentiating effect by Brefeldin A on CD7-SAP cytotoxicity suggesting that this inhibitor interferes with retrograde route(s) other than the well established Trans-Golgi Network-ER retrograde route. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)
Figures

Open AccessArticle Species-Dependent Functionality of the Human Cytolytic Fusion Proteins Granzyme B-H22(scFv) and H22(scFv)-Angiogenin in Macrophages
Antibodies 2013, 2(1), 9-18; doi:10.3390/antib2010009
Received: 5 December 2012 / Revised: 4 January 2013 / Accepted: 8 January 2013 / Published: 11 January 2013
Cited by 8 | PDF Full-text (1742 KB) | HTML Full-text | XML Full-text
Abstract
Human cytolytic fusion proteins (hCFPs) are comprised of a specific cell-surface-binding moiety and an effector molecule of human origin. In contrast to common immunotoxins, including bacterial or plant toxins, they are considered not to be immunogenic. Two examples for human pro-apoptotic effector [...] Read more.
Human cytolytic fusion proteins (hCFPs) are comprised of a specific cell-surface-binding moiety and an effector molecule of human origin. In contrast to common immunotoxins, including bacterial or plant toxins, they are considered not to be immunogenic. Two examples for human pro-apoptotic effector proteins are the serine protease Granzyme B and the RNase Angiogenin. Pre-clinical testing of functionality in in vitro and in vivo studies is essential for therapeutics. Establishing relevant animal models that have predictive value for therapeutic success is a great challenge in biomedical research. In this study, we investigated the species-dependent cytotoxic activity of two hCFPs prior to their application in a murine inflammation model. We found that in vitro and ex vivo either hCFP was able to kill human cells only, leaving murine cells unaffected. In contrast, no species-dependency was found for the bacterial Pseudomonas exotoxin A based immunotoxin H22(scFv)-ETA’. This species-dependent functioning has to be carefully considered when performing pre-clinical studies in animal models. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)

Review

Jump to: Research

Open AccessReview Human Cytolytic Fusion Proteins: Modified Versions of Human Granzyme B and Angiogenin Have the Potential to Replace Bacterial Toxins in Targeted Therapies against CD64+ Diseases
Antibodies 2014, 3(1), 92-115; doi:10.3390/antib3010092
Received: 19 November 2013 / Revised: 23 January 2014 / Accepted: 28 January 2014 / Published: 19 February 2014
Cited by 1 | PDF Full-text (430 KB) | HTML Full-text | XML Full-text
Abstract
Targeted therapies for the treatment of cancer, but also inflammation and autoimmune diseases will reduce major side effects accompanied with conventional treatment modalities. The immunotoxin concept uses bacterial or plant toxins, coupled to antibodies or natural ligands targeting cancer cells. Initially, immunotoxins [...] Read more.
Targeted therapies for the treatment of cancer, but also inflammation and autoimmune diseases will reduce major side effects accompanied with conventional treatment modalities. The immunotoxin concept uses bacterial or plant toxins, coupled to antibodies or natural ligands targeting cancer cells. Initially, immunotoxins suffered from drawbacks like nonspecific cytotoxicity. Even the third generation of immunotoxins comprised of truncated antibodies and modified effector molecules experienced clinical set-backs due to immune responses. Long-term treatment of cancer and non-life-threatening chronic inflammatory diseases requires their complete ‘humanization’. This lead to evaluating human cytolytic fusion proteins (hCFPs), based on human apoptosis-inducing proteins. Lacking an endogenous translocation domain dramatically reduces the cell-death inducing capacity of such proteins. Here, we report on optimizing hCFPs, based on the anti-CD64 single chain variable fragment H22(scFv), specifically eliminating CD64+ macrophages and malignant progenitor cells. We replaced the bacterial toxin in H22(scFv)-ETA' with the pro-apoptotic human granzyme B or angiogenin. Translocation was promoted by a sophisticated adapter containing a membrane transfer peptide (MTD) flanked by endosomal and cytosolic cleavable peptides, thus achieving in vitro cytotoxic activity comparable to bacterial immunotoxins. We demonstrate for the first time that optimized hCFPs, based on granzyme B or angiogenin, can compete with classical ETA-based immunotoxins. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)
Open AccessReview T-Cell Receptor-Like Antibodies: Targeting the Intracellular Proteome Therapeutic Potential and Clinical Applications
Antibodies 2013, 2(3), 517-534; doi:10.3390/antib2030517
Received: 15 August 2013 / Revised: 22 August 2013 / Accepted: 22 August 2013 / Published: 17 September 2013
Cited by 2 | PDF Full-text (215 KB) | HTML Full-text | XML Full-text
Abstract
Major histocompatibility complex (MHC) class I molecules are key in the immune response against malignant cells by shaping the T-cell repertoire and presenting peptides from endogenous antigens to CD8+ cytotoxic T cells. Because of their unique specificity, MHC-peptide complexes are a desirable [...] Read more.
Major histocompatibility complex (MHC) class I molecules are key in the immune response against malignant cells by shaping the T-cell repertoire and presenting peptides from endogenous antigens to CD8+ cytotoxic T cells. Because of their unique specificity, MHC-peptide complexes are a desirable target for novel immunotherapeutic approaches. These complexes can be targeted by recombinant T-cell receptors (TCRs). However, most TCRs produced thus far have affinities which are too low for target detection under normal assay conditions, and limited stability (due to their generation in a single-chain version). Developing high-affinity soluble antibody molecules endowed with a TCR-like specificity toward tumor epitopes, termed TCR-like antibodies, addresses the low affinity of TCRs. These TCR-like antibodies are being developed as a new immunotherapeutic class for targeting tumor cells and mediating their specific killing. In addition, these antibodies are valuable research reagents enabling the study of human class I peptide-MHC ligand-presentation and TCR–peptide–MHC interactions. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)
Open AccessReview Ricin and Ricin-Containing Immunotoxins: Insights into Intracellular Transport and Mechanism of action in Vitro
Antibodies 2013, 2(2), 236-269; doi:10.3390/antib2020236
Received: 27 December 2012 / Revised: 8 April 2013 / Accepted: 11 April 2013 / Published: 19 April 2013
Cited by 6 | PDF Full-text (337 KB) | HTML Full-text | XML Full-text
Abstract
Ricin is a type II ribosome inactivating protein (RIP) isolated from castor beans. Its high toxicity classifies it as a possible biological weapon. On the other hand, ricin linked to specific monoclonal antibodies or used in other conjugates has powerful medical applications. [...] Read more.
Ricin is a type II ribosome inactivating protein (RIP) isolated from castor beans. Its high toxicity classifies it as a possible biological weapon. On the other hand, ricin linked to specific monoclonal antibodies or used in other conjugates has powerful medical applications. Ricin consists of an A-chain (RTA) that damages ribosomes and inhibits protein synthesis, and a B-chain that plays a role in binding and cellular uptake. A number of recent studies have demonstrated that ricin-induced inhibition of protein synthesis is not the only mechanism responsible for cell death. It turns out that ricin is able to induce apoptosis in different cell lines and multiple organs in animals. However, the molecular link between protein synthesis inhibition and ricin-dependent triggering of apoptotic cell death is unclear. This review describes the intracellular transport of ricin and ricin-based immunotoxins and their mechanism of action in different non-malignant and cancer cell lines. Moreover, various ricin-containing immunotoxins, their composition, medical applications and side-effects will be described and discussed. Understanding the mechanism of action of ricin-based immunotoxins will facilitate construction of effectively acting immunotoxins that can be used in the clinic for cancer treatment. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)
Open AccessReview Diving through Membranes: Molecular Cunning to Enforce the Endosomal Escape of Antibody-Targeted Anti-Tumor Toxins
Antibodies 2013, 2(2), 209-235; doi:10.3390/antib2020209
Received: 4 March 2013 / Revised: 27 March 2013 / Accepted: 5 April 2013 / Published: 17 April 2013
Cited by 7 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
Membranes are vital barriers by which cells control the flux of molecules and energy between their exterior and interior and also between their various intracellular compartments. While numerous transport systems exist for ions and small molecules, the cytosolic uptake of larger biological [...] Read more.
Membranes are vital barriers by which cells control the flux of molecules and energy between their exterior and interior and also between their various intracellular compartments. While numerous transport systems exist for ions and small molecules, the cytosolic uptake of larger biological molecules and in particular antibody-targeted drugs, is a big challenge. Inducing leakage of the plasma membrane is unfavorable since the target cell specificity mediated by the antibody would likely be lost in this case. After binding and internalization, the antibody drug conjugates reach the endosomes. Thus, enforcing the endosomal escape of anti-tumor toxins without affecting the integrity of other cellular membranes is of paramount importance. Different strategies have been developed in the last decades to overcome endosomal accumulation and subsequent lysosomal degradation of targeted protein-based drugs. In this review we summarize the various efforts made to establish efficient techniques to disrupt the endosomal membrane barrier including the use of molecular ferries such as cell penetrating peptides or viral membrane fusion proteins, endosomal leakage inducing molecules such as saponins or monensin and physicochemical methods as represented by photochemical internalization. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)
Figures

Open AccessReview Selective Induction of Cancer Cell Death by Targeted Granzyme B
Antibodies 2013, 2(1), 130-151; doi:10.3390/antib2010130
Received: 24 December 2012 / Revised: 18 February 2013 / Accepted: 20 February 2013 / Published: 27 February 2013
Cited by 3 | PDF Full-text (759 KB) | HTML Full-text | XML Full-text
Abstract
The potential utility of immunotoxins for cancer therapy has convincingly been demonstrated in clinical studies. Nevertheless, the high immunogenicity of their bacterial toxin domain represents a critical limitation, and has prompted the evaluation of cell-death inducing proteins of human origin as a [...] Read more.
The potential utility of immunotoxins for cancer therapy has convincingly been demonstrated in clinical studies. Nevertheless, the high immunogenicity of their bacterial toxin domain represents a critical limitation, and has prompted the evaluation of cell-death inducing proteins of human origin as a basis for less immunogenic immunotoxin-like molecules. In this review, we focus on the current status and future prospects of targeted fusion proteins for cancer therapy that employ granzyme B (GrB) from cytotoxic lymphocytes as a cytotoxic moiety. Naturally, this serine protease plays a critical role in the immune defense by inducing apoptotic target cell death upon cleavage of intracellular substrates. Advances in understanding of the structure and function of GrB enabled the generation of chimeric fusion proteins that carry a heterologous cell binding domain for recognition of tumor-associated cell surface antigens. These hybrid molecules display high selectivity for cancer cells, with cell killing activities similar to that of corresponding recombinant toxins. Recent findings have helped to understand and circumvent intrinsic cell binding of GrB and susceptibility of the enzyme to inhibition by serpins. This now allows the rational design of optimized GrB derivatives that avoid sequestration by binding to non-target tissues, limit off-target effects, and overcome resistance mechanisms in tumor cells. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)
Open AccessReview An Old Idea Tackling a New Problem: Targeted Toxins Specific for Cancer Stem Cells
Antibodies 2013, 2(1), 82-92; doi:10.3390/antib2010082
Received: 6 December 2012 / Revised: 19 January 2013 / Accepted: 22 January 2013 / Published: 28 January 2013
Cited by 1 | PDF Full-text (169 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Targeting and killing specific cells discriminately has been the goal of targeted therapy dating back to the era of Paul Ehrlich. The discovery of cancer stem cells has caused a paradigm shift within the cancer field and provided an opportunity to use [...] Read more.
Targeting and killing specific cells discriminately has been the goal of targeted therapy dating back to the era of Paul Ehrlich. The discovery of cancer stem cells has caused a paradigm shift within the cancer field and provided an opportunity to use targeted therapies such as targeted toxins to bind and kill these cells selectively. A number of targeted toxins have been developed against recently identified cancer stem cell markers. In this review we discuss the development and current status of these exciting novel drugs and their potential use to combat drug-refractory relapse. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)
Open AccessReview Improving the Therapeutic Potential of Human Granzyme B for Targeted Cancer Therapy
Antibodies 2013, 2(1), 19-49; doi:10.3390/antib2010019
Received: 13 December 2012 / Revised: 4 January 2013 / Accepted: 8 January 2013 / Published: 16 January 2013
Cited by 3 | PDF Full-text (359 KB) | HTML Full-text | XML Full-text
Abstract
Conventional cancer treatments lack specificity and often cause severe side effects. Targeted therapeutic approaches are therefore preferred, including the use of immunotoxins (ITs) that comprise cell-binding and cell death-inducing components to allow the direct and specific delivery of pro-apoptotic agents into malignant [...] Read more.
Conventional cancer treatments lack specificity and often cause severe side effects. Targeted therapeutic approaches are therefore preferred, including the use of immunotoxins (ITs) that comprise cell-binding and cell death-inducing components to allow the direct and specific delivery of pro-apoptotic agents into malignant cells. The first generation of ITs consisted of toxins derived from bacteria or plants, making them immunogenic in humans. The recent development of human cytolytic fusion proteins (hCFP) consisting of human effector enzymes offers the prospect of highly-effective targeted therapies with minimal side effects. One of the most promising candidates is granzyme B (GrB) and this enzyme has already demonstrated its potential for targeted cancer therapy. However, the clinical application of GrB may be limited because it is inactivated by the overexpression in tumors of its specific inhibitor serpin B9 (PI-9). It is also highly charged, which means it can bind non-specifically to the surface of non-target cells. Furthermore, human enzymes generally lack an endogenous translocation domain, thus the endosomal release of GrB following receptor-mediated endocytosis can be inefficient. In this review we provide a detailed overview of these challenges and introduce promising solutions to increase the cytotoxic potency of GrB for clinical applications. Full article
(This article belongs to the Special Issue Recombinant Immunotoxins)

Journal Contact

MDPI AG
Antibodies Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
antibodies@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Antibodies
Back to Top