http://www.mdpi.com/journal/antibodies Latest open access articles published in Antibodies at http://www.mdpi.com/journal/antibodies http://www.mdpi.com/2073-4468/2/2/338 Using genetic engineering a humanized Fab fragment with specificity for CD19 was fused to a disulfide-stabilized single-chain antibody (dsFv) recognizing CD5. This format should show reduced immunogenicity and improved tissue penetration. The specificity of bsAb FabCD19xdsFvCD5 binding to target cells was verified by flow cytometry on B and T lymphoma cell lines. Binding affinities of both arms were compared with the bivalent parental antibodies against CD19 and CD5 by binding competition assay. Redirected lysis of B lymphoma cells by preactivated PBMC from healthy donors was demonstrated in a chromium-release assay. A clear dose-response relationship could be established in the range from 1 ng/mL to 10 mg/mL bsAb. To evaluate the in vivo efficacy of bsAb FabCD19xdsFvCD5, NOD/SCID mice were intravenously injected with luciferase transfected Raji lymphoma cells together with pre-activated PBMC. Mice received five injections of therapeutic bsAb or control antibodies. While in the control groups all mice died within 40 to 50 days, 40% of bsAb treated animals survived longer than 60 days. Antibodies 2013-05-14 2 2 Article 10.3390/antib2020338 338 352 2073-4468 2013-05-14 doi: 10.3390/antib2020338 Sandra Lüttgau Dorothée Deppe Saskia Meyer Regina Fertig Hossein Panjideh Martin Lipp Oliver Schmetzer Antonio Pezzutto Frank Breitling Gerhard Moldenhauer http://www.mdpi.com/2073-4468/2/2/321 We previously demonstrated that the Fc receptor γ-chain Y58(C-terminal tyrosine) is highly susceptible to dephosphorylation; a mechanism that controls the extent of Syk activation and the downstream signaling in mast cells. Here, we explored the importance of the γ-chain Y47 (N-terminal tyrosine) in mast cell signaling. We generated a highly sensitive and versatile phospho-specific antibody that recognized the phosphorylated Y47 in various species. Using this antibody, we found that mutation of the FcεRIβ Y219 to phenylalanine caused a loss in the phosphorylation of the γ-chain Y47, consistent with the previously described role of Y219 in Lyn association with FcεRIβ and subsequent FcεRIγ phosphorylation. These conditions also diminished the tyrosine phosphorylation of Syk and LAT1 but, surprisingly, not the phosphorylation of Akt at T308. Mutation of Y47 or Y58 of the γ-chain also caused a marked inhibition of Syk and LAT1 phosphorylation, but only the latter mutant showed a reduction in Akt phosphorylation. These findings show that the full phosphorylation of Syk and LAT1 requires the FcεRIβ Y219 and both Y47 and Y58 of the γ-chain. However, T308 phosphorylation of Akt is largely independent of FcεRIγ Y47 phosphorylation and of the Lyn-binding site (Y219) on the FcεRIβ. Antibodies 2013-05-13 2 2 Article 10.3390/antib2020321 321 337 2073-4468 2013-05-13 doi: 10.3390/antib2020321 Ryo Suzuki Sarah Leach Barbara Dema Juan Rivera http://www.mdpi.com/2073-4468/2/2/306 Many human diseases are caused by mutant or abnormal protein functions that are largely confined to the inside of cells, rather than being displayed on the abnormal cell surface. Furthermore, many of the functional consequences of aberrant proteins, such as in cancer cells, are due to protein–protein interactions (PPIs). Developing reagents that can specifically interfere with PPI is an important goal for both therapeutic use and as reagents to interrogate the functional importance of PPI. Antibody fragments can be used for inhibiting PPI. Our recent technology development has provided a set of simple protocols that allow development of single antibody variable (V) region domains that can function inside the reducing environment of the cell. The heavy chain variable region (VH) segments mainly used in this technology are based on a designer framework that folds inside cells without the need for the intra-chain disulphide bond and can be used as drug surrogates to determine on-target effects (target validation) and as templates for small molecule drug development. In this review, we discuss our work on single domains as intracellular antibodies and where this work might in the future. Antibodies 2013-05-02 2 2 Review 10.3390/antib2020306 306 320 2073-4468 2013-05-02 doi: 10.3390/antib2020306 Jia Zeng Jing Zhang Tomoyuki Tanaka Terence Rabbitts http://www.mdpi.com/2073-4468/2/2/270 Photodynamic therapy (PDT) is a clinically-approved but rather under-exploited treatment modality for cancer and pre-cancerous superficial lesions. It utilises a cold laser or LED to activate a photochemical reaction between a light activated drug (photosensitiser-drug) and oxygen to generate cytotoxic oxygen species. These free radical species damage cellular components leading to cell death. Despite its benefits, the complexity, limited potency and side effects of PDT have led to poor general usage. However, the research area is very active with an increasing understanding of PDT-related cell biology, photophysics and significant progress in molecular targeting of disease. Monoclonal antibody therapy is maturing and the next wave of antibody therapies includes antibody-drug conjugates (ADCs), which promise to be more potent and curable. These developments could lift antibody-directed phototherapy (ADP) to success. ADP promises to increase specificity and potency and improve drug pharmacokinetics, thus delivering better PDT drugs whilst retaining its other benefits. Whole antibody conjugates with first generation ADP-drugs displayed problems with aggregation, poor pharmacokinetics and loss of immuno-reactivity. However, these early ADP-drugs still showed improved selectivity and potency. Improved PS-drug chemistry and a variety of conjugation strategies have led to improved ADP-drugs with retained antibody and PS-drug function. More recently, recombinant antibody fragments have been used to deliver ADP-drugs with superior drug loading, more favourable pharmacokinetics, enhanced potency and target cell selectivity. These improvements offer a promise of better quality PDT drugs. Antibodies 2013-04-25 2 2 Review 10.3390/antib2020270 270 305 2073-4468 2013-04-25 doi: 10.3390/antib2020270 Hayley Pye Ioanna Stamati Gokhan Yahioglu M. Butt Mahendra Deonarain http://www.mdpi.com/2073-4468/2/2/236 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. Antibodies 2013-04-19 2 2 Review 10.3390/antib2020236 236 269 2073-4468 2013-04-19 doi: 10.3390/antib2020236 Monika Słomińska-Wojewódzka Kirsten Sandvig http://www.mdpi.com/2073-4468/2/2/209 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. Antibodies 2013-04-17 2 2 Review 10.3390/antib2020209 209 235 2073-4468 2013-04-17 doi: 10.3390/antib2020209 Hendrik Fuchs Christopher Bachran David Flavell http://www.mdpi.com/2073-4468/2/2/193 Single chain variable domain (Fv) fragments (scFv) are powerful tools in research and clinical settings, owing to better pharmacokinetic properties compared to the parent monoclonal antibodies and the relative ease of producing them in large quantities, at low cost. Though they offer several advantages, they suffer from lower binding affinity and rapid clearance from circulation, which limits their therapeutic potential. However, these fragments can be genetically modified to enhance desirable properties, such as multivalency, high target retention and slower blood clearance, and as such, a variety of scFv formats have been generated. ScFvs can be administered by systemic injection for diagnostic and therapeutic purposes. They can be expressed in vivo through viral vectors in instances where large infection rates and sustenance of high levels of the antibody is required. ScFvs have found applications as tools for in vivo loss-of-function studies and inactivation of specific protein domains, diagnostic imaging, tumor therapy and treatment for neurodegenerative and infectious diseases. This review will focus on their in vivo applications. Antibodies 2013-04-11 2 2 Review 10.3390/antib2020193 193 208 2073-4468 2013-04-11 doi: 10.3390/antib2020193 Philippe Monnier Robin Vigouroux Nardos Tassew http://www.mdpi.com/2073-4468/2/2/168 Avian influenza A virus comprises sixteen hemagglutinin (HA) and nine neuraminidase (NA) subtypes (N1–N9). To isolate llama single-domain antibody fragments (VHHs) against all N subtypes, four llamas were immunized with mixtures of influenza viruses. Selections using influenza virus yielded predominantly VHHs binding to the highly immunogenic HA and nucleoprotein. However, selection using enzymatically active recombinant NA (rNA) protein enabled us to isolate NA binding VHHs. Some isolated VHHs cross-reacted to other N subtypes. These were subsequently used for the capture of N subtypes that could not be produced as recombinant protein (rN6) or were enzymatically inactive (rN1, rN5) in phage display selection, yielding novel VHHs. In total we isolated 188 NA binding VHHs, 64 of which were expressed in yeast. Most VHHs specifically recognize a single N subtype, but some VHHs cross-react with other N-subtypes. At least one VHH bound to all N subtypes, except N4, identifying a conserved antigenic site. Thus, this work (1) describes methods for isolating NA binding VHHs, (2) illustrates the suitability of llama immunization with multiple antigens for retrieving many binders against different antigens and (3) describes 64 novel NA binding VHHs, including a broadly reactive VHH, which can be used in various assays for influenza virus subtyping, detection or serology. Antibodies 2013-04-10 2 2 Article 10.3390/antib2020168 168 192 2073-4468 2013-04-10 doi: 10.3390/antib2020168 Michiel Harmsen Juliette Blokker Sylvia Pritz-Verschuren Willem Bartelink Herman van der Burg Guus Koch http://www.mdpi.com/2073-4468/2/1/152 To obtain thermostable immunoreagents specific for the spore form of Bacillus anthracis two llamas were immunized with a combination of six different recombinant proteins. These proteins BclA, gerQ, SODA1, SOD15, BxpB and the protein p5303 have all been shown as components of the B. anthracis spore and could potentially serve as targets for the detection of spores in multiplexed biosensors. Peripheral blood lymphocytes were used to construct a phage display library from which single domain antibodies (sdAbs) targeting each of the proteins were isolated. Unique sdAbs exhibiting nanomolar or better affinities for the recombinant proteins were obtained and most of the isolated sdAbs retained their ability to bind antigen after cycles of heating as determined by enzyme linked immunosorbent assay (ELISA). SdAbs targeting the BclA and gerQ proteins were able to successfully detect bacterial spores, whether broken or intact, using a direct ELISA; the sdAbs were specific, showing binding only to B. anthracis spores and not to other Bacillus species. Additionally, SODA1 and p5303 binding sdAbs detected spores in sandwich assays serving as both captures and tracers. Used in combination, sdAbs targeting B. anthracis proteins could be integrated into emerging biosensors to improve specificity in multiplex assays. Antibodies 2013-03-15 2 1 Article 10.3390/antib2010152 152 167 2073-4468 2013-03-15 doi: 10.3390/antib2010152 Scott Walper P. Lee George Anderson Ellen Goldman http://www.mdpi.com/2073-4468/2/1/130 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. Antibodies 2013-02-27 2 1 Review 10.3390/antib2010130 130 151 2073-4468 2013-02-27 doi: 10.3390/antib2010130 Pranav Oberoi Robert Jabulowsky Winfried Wels http://www.mdpi.com/2073-4468/2/1/113 Monoclonal antibody (MAb) based therapies have achieved considerable success in oncology, primarily when used in combination with cytotoxic drugs. Antibody drug conjugates (ADCs) are a class of therapeutics that harness the antigen-selectivity of MAbs to deliver highly potent cytotoxic drugs to antigen-expressing tumor cells. The use of MAb directed delivery can confer a therapeutic index to highly potent cytotoxic drugs, increasing both the efficacy and safety of therapy. Although simple in concept, to achieve the design goal of improved therapeutic efficacy and reduced toxicity, each of the components of an ADC; the MAb, linker and drug need to considered in the context of the targeted antigen, the selectivity of antigen expression and the biology of the tumor type on which the target antigen is expressed. The characteristics of targets, MAbs, linkers and drugs being used in ADC design are discussed. Antibodies 2013-02-27 2 1 Review 10.3390/antib2010113 113 129 2073-4468 2013-02-27 doi: 10.3390/antib2010113 Pamela Trail http://www.mdpi.com/2073-4468/2/1/93 An immune phage library derived from mice, hyperimmunized with morphine-conjugated BSA, was used to isolate a single-chain Fv (scFv) clone, M86, with binding activity to morphine-conjugated thyroglobulin (morphine-C-Tg) but not to codeine-, cocaine-, or ketamine-conjugated Tg. Surface plasmon resonance analysis using a morphine-C-Tg-coupled CM5 sensor chip showed that the Kd value was 1.26 × 10−8 M. To analyze its binding activity to free morphine and related compounds, we performed a competitive ELISA with M86 and morphine-C-Tg in the absence or presence of varying doses of free morphine and related compounds. IC50 values for opium, morphine, codeine, and heroin were 257 ng/mL, 36.4, 7.3, and 7.4 nM, respectively. Ketamine and cocaine exhibited no competitive binding activity to M86. Thus, we established a phage library-derived scFv, M86, which recognized not only free morphine and codeine as opium components but also heroin. This characteristic of M86 may be useful for developing therapeutic reagents for opiate addiction and as a free morphine-specific antibody probe. Antibodies 2013-02-07 2 1 Article 10.3390/antib2010093 93 112 2073-4468 2013-02-07 doi: 10.3390/antib2010093 Miho Matsukizono Mariko Kamegawa Koichi Tanaka Shinya Kohra Koji Arizono Yuta Hamazoe Kazuhisa Sugimura http://www.mdpi.com/2073-4468/2/1/82 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. Antibodies 2013-01-28 2 1 Review 10.3390/antib2010082 82 92 2073-4468 2013-01-28 doi: 10.3390/antib2010082 Nate Waldron Daniel Vallera http://www.mdpi.com/2073-4468/2/1/66 The single variable new antigen receptor domain antibody fragments (VNARs) derived from shark immunoglobulin new antigen receptor antibodies (IgNARs) represent some of the smallest known immunoglobulin-based protein scaffolds. As single domains, they demonstrate favorable size and cryptic epitope recognition properties, making them attractive in diagnosis and therapy of numerous disease states. Here, we examine the stability of VNAR domains with a focus on a family of VNARs specific for apical membrane antigen 1 (AMA-1) from Plasmodium falciparum. The VNARs are compared to traditional monoclonal antibodies (mAbs) in liquid, lyophilized and immobilized nitrocellulose formats. When maintained in various formats at 45 °C, VNARs have improved stability compared to mAbs for periods of up to four weeks. Using circular dichroism spectroscopy we demonstrate that VNAR domains are able to refold following heating to 80 °C. We also demonstrate that VNAR domains are stable during incubation under potential in vivo conditions such as stomach acid, but not to the protease rich environment of murine stomach scrapings. Taken together, our results demonstrate the suitability of shark VNAR domains for various diagnostic platforms and related applications. Antibodies 2013-01-25 2 1 Article 10.3390/antib2010066 66 81 2073-4468 2013-01-25 doi: 10.3390/antib2010066 Katherine Griffiths Olan Dolezal Kathy Parisi Julie Angerosa Con Dogovski Miles Barraclough Abdulmonem Sanalla Joanne Casey Iveth González Matthew Perugini Stewart Nuttall Michael Foley http://www.mdpi.com/2073-4468/2/1/50 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. Antibodies 2013-01-16 2 1 Article 10.3390/antib2010050 50 65 2073-4468 2013-01-16 doi: 10.3390/antib2010050 Francesco Giansanti Valeria Giordani Riccardo Vago David Flavell Sopsamorn Flavell Maria Fabbrini Rodolfo Ippoliti http://www.mdpi.com/2073-4468/2/1/19 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. Antibodies 2013-01-16 2 1 Review 10.3390/antib2010019 19 49 2073-4468 2013-01-16 doi: 10.3390/antib2010019 Grit Hehmann-Titt Sonja Schiffer Nina Berges Georg Melmer Stefan Barth http://www.mdpi.com/2073-4468/2/1/9 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. Antibodies 2013-01-11 2 1 Article 10.3390/antib2010009 9 18 2073-4468 2013-01-11 doi: 10.3390/antib2010009 Sonja Schiffer Dmitrij Hristodorov Radoslav Mladenov Eric Aslanian Michael Huhn Rainer Fischer Stefan Barth Theo Thepen http://www.mdpi.com/2073-4468/2/1/1 TATA-box binding protein-associated factor 1 (TAF1), the largest subunit of the transcription factor IID complex, plays an important role in the RNA polymerase II-mediated gene transcription pathway regulating the transcription of a large number of genes related to cell division. The neuron-specific isoform of the TAF1 gene (N-TAF1) may have an essential role in neurons through transcriptional regulation of many neuron-specific genes. The present study reports the preparation and properties of a monoclonal antibody directed against N-TAF1. The monoclonal antibody, 3A-11F, specifically recognized N-TAF1 protein with no reactivity to TAF1 protein, as evidenced by immunocytochemistry and immunoprecipitation using cultured cells expressing recombinant N-TAF1 or TAF1 protein. Immunohistochemistry using 3A-11F showed that N-TAF1-imunoreactivity was detected in the nuclear region of neurons in the rat brain. The 3A-11F monoclonal antibody promises to be a useful tool for determining the expression pattern and biological function of N-TAF1 in the brain. Antibodies 2012-12-21 2 1 Communication 10.3390/antib2010001 1 8 2073-4468 2012-12-21 doi: 10.3390/antib2010001 Satoshi Makino Chiaki Masuda Satoshi Ando Gen Tamiya Ikuo Tooyama http://www.mdpi.com/2073-4468/1/3/294 Importance of herbal medicines have recently increased owing to rising interest in their health benefits. However, medicinal plant extracts are complex mixtures of phytochemicals that act synergistically or additively on specific and/or multiple molecular and cellular targets. Thus, it is difficult to examine the actual pharmacological roles of active compounds in plant extracts. This review describes a new strategy for isolating target compounds from plant extracts using immunoaffinity columns coupled with monoclonal antibodies (mAbs) against natural compounds. Through one-step purification using mAb-coupled immunoaffinity columns, we succeeded in preparing a knockout (KO) extract, which contains all components except the target compound. Furthermore, we investigated the pharmacological effects of the KO extract to reveal the actual effects of a bioactive compound in the crude extract. This approach may help determine the potential function of target compounds in herbal medicines. Antibodies 2012-12-06 1 3 Review 10.3390/antib1030294 294 307 2073-4468 2012-12-06 doi: 10.3390/antib1030294 Takuhiro Uto Nguyen Tung Osamu Morinaga Yukihiro Shoyama http://www.mdpi.com/2073-4468/1/3/284 Scutellariae radix (S. radix) is one of the most important crude drugs used in Kampo medicines (KMs). A part of its pharmaceutical properties is due to flavone glycoside, baicalin (BI). A technique named eastern blotting was developed for the specific and easy identification of BI in the extracts of crude drugs and KMs using anti-BI monoclonal antibody (MAb). BI separated by silica gel thin-layer chromatography (TLC) transferred to a polyethersulfone (PES) membrane was treated with a NaIO4 solution and reacted with bovine serum albumin (BSA) preparing BI-BSA conjugate on the PES membrane. Anti-BI MAb was bound and then antibody labeled with peroxidase directed against anti-BI MAb. Finally, a substrate was added and then BI was detected. As little as 1 mg of BI was still detected on the PES membrane under immunostaining method. Various samples of S. radix and KMs which contain S. radix were qualitatively analyzed, and BI was visually detected by eastern blotting technique. Furthermore, this method was applied for the immunohistochemical study to investigate the distribution of BI in the fresh root of Scutellaria baicalensis using immunoblotting by transferred from fresh root to the PES membrane. Antibodies 2012-11-27 1 3 Article 10.3390/antib1030284 284 293 2073-4468 2012-11-27 doi: 10.3390/antib1030284 Osamu Morinaga Ryo Mukae Takuhiro Uto Yothawathorn Pariyawongsakul Waraporn Putalun Hiroyuki Tanaka Yukihiro Shoyama http://www.mdpi.com/2073-4468/1/3/273 We prepared a monoclonal antibody (mAb 1C1) showing specificity for artemisinin (AM) and artesunate (AS), and we developed an indirect competitive enzyme-linked immunosorbent assay (icELISA) using this novel mAb. Moreover, we prepared a recombinant antibody derived from mAb 1C1 in order to overcome insufficient mAb production by hybridoma culture. A recombinant antigen-binding fragment (Fab) was easily constructed using antibody manipulation technologies and was produced by microorganisms in high yield. We herein review immunochemical approaches for analysis of the antimalarial drugs AM and AS that were able to yield analysis results for multiple samples in a short period of time using simple and reliable protocols. Antibodies 2012-11-02 1 3 Review 10.3390/antib1030273 273 283 2073-4468 2012-11-02 doi: 10.3390/antib1030273 Hiroyuki Tanaka Madan Paudel Ayako Takei Junichi Sakoda Thaweesak Juengwatanatrakul Kaori Sasaki-Tabata Waraporn Putalun Wanchai De-Eknamkul Oraphan Matangkasombut Yukihiro Shoyama Satoshi Morimoto http://www.mdpi.com/2073-4468/1/3/259 Non-specific lipid transfer protein (LTP) in barley grain reacted with the IgE in sera drawn from food allergy patients. A sandwich-type of enzyme-linked immunosorbent assay (ELISA) was developed with mouse monoclonal antibodies raised against LTP purified with barley flour. This ELISA showed a practical working range of 0.3–3 ng/mL and no cross-reactivity with wheat, adlay and rye. Using this ELISA, LTP was determined in several types of barley-foods, including fermented foods such as malt vinegar, barley-malt miso and beer. LTP content in beer of the same kind was approximately constant, even if manufacturing factory and production days were different. Not only as a factor of foam formation and stability but also as an allergen, controlling and monitoring of LTP in beer should be considered. Taken together, our LTP-detecting ELISA can be proposed as an appropriate system for the quality control of beer. Antibodies 2012-10-16 1 3 Article 10.3390/antib1030259 259 272 2073-4468 2012-10-16 doi: 10.3390/antib1030259 Yukie Murakami-Yamaguchi Junko Hirose Kumiko Kizu Fumiko Okazaki Wataru Fujii Hiroshi Narita http://www.mdpi.com/2073-4468/1/2/239 An enzyme-linked immunosorbent assay (ELISA) using monoclonal antibody (MAb), Fab antibody, and single-chain variable fragment (scFv) antibody has become one of the most promising analytical methods owing to its rapidity, sensitivity, and reliability. Recently, a chimera of green fluorescent protein (GFP) with a scFv antibody, named fluobody, was proposed as a probe for an alternative immunosorbent assay; i.e., fluorescence-linked immunosorbent assay (FLISA). In this FLISA, an even more sensitive, simple, and rapid immunoassay can be performed by detecting the highly sensitive fluorophore of GFP that is genetically and directly fused to the scFv antibody. In addition, the time- and cost-consuming secondary antibody reaction and the following enzyme-substrate reaction, necessary for conventional ELISA, can be avoided, making it possible to complete the assay more rapidly. Focusing on naturally occurring bioactive products, fluobody recognizing 1,4-naphthoquinone, plumbagin and triterpenoid saponin, ginsenosides were successfully expressed in Escherichia coli (E. coli) and applied to FLISA. The construction, the expression, and the potential use of fluobody in quantitative/qualitative analysis of bioactive natural products are reviewed in this article. Antibodies 2012-09-11 1 2 Review 10.3390/antib1020239 239 258 2073-4468 2012-09-11 doi: 10.3390/antib1020239 Seiichi Sakamoto Benyakan Pongkitwitoon Hiromichi Nakahara Osamu Shibata Yukihiro Shoyama Hiroyuki Tanaka Satoshi Morimoto http://www.mdpi.com/2073-4468/1/2/215 Monoclonal antibodies to the soluble antigens or cell surface markers hold great promise as effective human therapeutics. One of the major disadvantages is its large size, which prevents efficient penetration into the target tissues. Smaller version of antibodies, which has only antigen binding sites, is extensively investigated. It becomes increasingly apparent, however, that these smaller fragments of antibodies are rather difficult to produce, as the normally efficient mammalian secretion system does not work well for these fragments. Thus, refolding of insoluble proteins produced in Escherichia coli is a method of choice, although such refolding is mainly based on trial-and-error experiment. Here we describe a novel refolding system using a new amino acid-based detergent, N-lauroyl-L-glutamate, and arginine. This detergent appears to readily dissociate from proteins below critical micelle concentration (CMC), while remaining effective in protein solubilization above CMC. Arginine suppresses protein aggregation when the detergent concentration was reduced below CMC. The interaction of the detergent and arginine with proteins, which play an important role in protein refolding, will be discussed in great length. Antibodies 2012-08-29 1 2 Review 10.3390/antib1020215 215 238 2073-4468 2012-08-29 doi: 10.3390/antib1020215 Tsutomu Arakawa Yoshiko Kita Daisuke Ejima http://www.mdpi.com/2073-4468/1/2/199 Antibody fragments, especially single-chain Fv fragments, have been established for the generation of immunoliposomes for targeted drug delivery in cancer therapy and other applications. Bispecific immunoliposomes should be useful for dual targeting addressing inter- and intratumoral heterogeneity of tumor antigen expression. Here, we established a protocol to generate dual-targeted immunoliposomes using genetically engineered scFv molecules recognizing two different tumor-associated antigens, EGFR and CEA (CEACAM5), applying a step-wise insertion of antibody-coupled micelles into preformed PEGylated liposomes. The dual-targeted immunoliposomes retained binding activity for both antigens and combined the selectivity of both antibodies within one liposome. Thus, these dual-targeted immunoliposomes should be suitable to deliver therapeutic payloads to tumor cells expressing EGFR or CEA, or both antigens. Antibodies 2012-07-25 1 2 Article 10.3390/antib1020199 199 214 2073-4468 2012-07-25 doi: 10.3390/antib1020199 Katharina Mack Ronny Rüger Sina Fellermeier Oliver Seifert Roland E. Kontermann http://www.mdpi.com/2073-4468/1/2/172 Immunotherapy has emerged as an alternative strategy to treat malignancies in addition to conventional radio- and chemotherapy. There has been a plethora of evidence that the immune system is able to control tumor outgrowth and a number of strategies have been put forward to utilize this ability for immunotherapy. However, some of these strategies have not been very efficient and their success has been limited by tumor evasion mechanisms. A promising approach to engage effector cells of the immune system overcoming some of the escape mechanisms has been introduced more than two decades ago. This approach is based on bispecific antibodies. Here we summarize the evolution of bispecific antibodies, their improvement, remaining obstacles and some controversial reports. Antibodies 2012-07-18 1 2 Review 10.3390/antib1020172 172 198 2073-4468 2012-07-18 doi: 10.3390/antib1020172 Slava Stamova Stefanie Koristka Juliane Keil Claudia Arndt Anja Feldmann Irene Michalk Holger Bartsch Claudia C. Bippes Marc Schmitz Marc Cartellieri Michael Bachmann http://www.mdpi.com/2073-4468/1/2/149 Immunocytokines (ICs) are a class of molecules created by linking tumor-reactive monoclonal antibodies to cytokines that are able to activate immune cells. Tumor selective localization is provided by the ability of the mAb component to bind to molecules found on the tumor cell surface or molecules found selectively in the tumor microenvronment. In this way the cytokine component of the immunocytokine is selectively localized to sites of tumor and can activate immune cells with appropriate receptors for the cytokine. Immunocytokines have been made and tested by us, and others, using a variety of tumor-reactive mAbs linked to distinct cytokines. To date, the majority of clinical progress has been made with ICs that have linked human interleukin-2 (IL2) to a select number of tumor reactive mAbs that had already been in prior clinical testing as non-modified mAbs. Here we briefly review the background for the creation of ICs, summarize current clinical progress, emphasize mechanisms of action for ICs that are distinct from those of their constituent components, and present some directions for future development and testing. Antibodies 2012-07-04 1 2 Review 10.3390/antib1020149 149 171 2073-4468 2012-07-04 doi: 10.3390/antib1020149 Paul M. Sondel Stephen D. Gillies http://www.mdpi.com/2073-4468/1/2/124 Alpha-particle emitter labeled monoclonal antibodies are being actively developed for treatment of metastatic cancer due to the high linear energy transfer (LET) and the resulting greater biological efficacy of alpha-emitters. Our knowledge of high LET particle radiobiology derives primarily from accelerated heavy ion beam studies. In heavy ion beam therapy of loco-regional tumors, the modulation of steep transition to very high LET peak as the particle approaches the end of its track (known as the Bragg peak) enables greater delivery of biologically potent radiation to the deep seated tumors while sparing normal tissues surrounding the tumor with the relatively low LET track segment part of the heavy ion beam. Moreover, fractionation of the heavy ion beam can further enhance the peak-to-plateau relative biological effectiveness (RBE) ratio. In contrast, internally delivered alpha particle radiopharmaceutical therapy lack the control of Bragg peak energy deposition and the dose rate is determined by the administered activity, alpha-emitter half-life and biological kinetics of the radiopharmaceutical. The therapeutic ratio of tumor to normal tissue is mainly achieved by tumor specific targeting of the carrier antibody. In this brief overview, we review the radiobiology of high LET radiations learned from ion beam studies and identify the features that are also applicable for the development of alpha-emitter labeled antibodies. The molecular mechanisms underlying DNA double strand break repair response to high LET radiation are also discussed. Antibodies 2012-06-26 1 2 Review 10.3390/antib1020124 124 148 2073-4468 2012-06-26 doi: 10.3390/antib1020124 Hong Song Srinivasan Senthamizhchelvan Robert F. Hobbs George Sgouros http://www.mdpi.com/2073-4468/1/1/88 Unmodified antibodies (abs) have been successful in the treatment of hematologic malignancies, but less so for the treatment of solid tumors. They trigger anti-tumor effects through their Fc-domains, and one way to improve their efficacy is to optimize their interaction with the effectors through Fc-engineering. Another way to empower abs is the design of bispecific abs and related fusion proteins allowing a narrower choice of effector cells. Here we review frequently chosen classes of effector cells, as well as common trigger molecules. Natural Killer (NK)- and T-cells are the most investigated populations in therapeutical approaches with bispecific agents until now. Catumaxomab, the first bispecific ab to receive drug approval, targets the tumor antigen Epithelial Cell Adhesion Molecule (EpCAM) and recruits T-cells via a binding site for the cell surface protein CD3. The next generation of recombinant ab-derivatives replaces the broadly reactive Fc-domain by a binding domain for a single selected trigger. Blinatumomab is the first clinically successful member of this class, targeting cancer cells via CD19 and engaging T-cells by CD3. Other investigators have developed related recombinant fusion proteins to recruit effectors, such as NK-cells and macrophages. The first such agents currently in preclinical and clinical development will be discussed. Antibodies 2012-06-01 1 1 Review 10.3390/antib1010088 88 123 2073-4468 2012-06-01 doi: 10.3390/antib1010088 Christoph Stein Ingo Schubert Georg H. Fey http://www.mdpi.com/2073-4468/1/1/70 A number of cytokines have shown beneficial effects in preclinical animal models of cancer and chronic inflammatory diseases. However, cytokine treatment is often associated with severe side effects, which prevent the administration of clinically relevant doses in humans. Immunocytokines are a novel class of biopharmaceuticals, consisting of a cytokine moiety fused to monoclonal antibodies or to an antibody fragment, which selectively accumulate at the disease site and thereby enhance the therapeutic effects of cytokines. This review surveys the recent preclinical and clinical advances in the field, with a special focus on the impact of antibody formats, target antigen and cytokine moieties on the therapeutic performance in vivo. We also discuss emerging data about the possibility to combine immunocytokines with other pharmacological agents. Antibodies 2012-05-31 1 1 Review 10.3390/antib1010070 70 87 2073-4468 2012-05-31 doi: 10.3390/antib1010070 Katrin L. Gutbrodt Dario Neri http://www.mdpi.com/2073-4468/1/1/39 Antibody-based immunotoxins comprise an important group in targeted cancer therapeutics. These chimeric proteins are a form of biological guided missiles that combine a targeting moiety with a potent effector molecule. The targeting moiety is mostly a monoclonal antibody (MAb) or a recombinant antibody-based fragment that confers target specificity to the immunotoxin. The effector domain is a potent protein toxin of bacterial or plant origin, which, following binding to the target cells, undergoes internalization and causes cell death. Over time and following research progression, immunotoxins become better fitted to their purpose, losing immunogenic fragments and non-specific targeting moieties. Many immunotoxins have gone through clinical evaluation. Some of these have been shown to be active and work is progressing with them in the form of further clinical trials. Others, mostly developed in the previous century, failed to generate a response in patients, or even caused undesired side effects. This article reviews the antibody and protein-toxin based immunotoxins that were clinically evaluated up to the present day. Antibodies 2012-05-15 1 1 Review 10.3390/antib1010039 39 69 2073-4468 2012-05-15 doi: 10.3390/antib1010039 Nurit Becker Itai Benhar http://www.mdpi.com/2073-4468/1/1/19 Bivalent single chain (sc)Fv-Fc antibodies have been used for years as recombinant alternatives of natural immunoglobulins. We have extended this approach to the scFv-Fc-scFv antibody format to obtain tetravalent antigen binding and the possibility to generate bispecific antibodies. We developed a mammalian expression vector system to construct tetravalent scFv-Fc-scFv antibodies with two NcoI+NotI compatible cloning sites flanking the Fc gene fragment. We demonstrated direct cloning from single chain antibody gene libraries and tested various scFv combinations. Transient production of scFv-Fc-scFv antibodies in human embryonic kidney (HEK) 293T cells achieved volumetric yields of up to 10 mg/L. However, expression levels were strongly dependent on the carboxyterminal scFv and the scFv combination. All scFv-Fc-scFv antibodies exclusively formed disulfide-linked homodimers. Antigen binding studies revealed dual specificity for all scFv-Fc-scFv employing different scFv fragments. Comparison of C-reactive protein (CRP) specific monovalent scFv LA13-IIE3, bivalent scFv-Fc and Fc-scFv LA13-IIE3, and tetravalent scFv-Fc-scFv (scFv LA13-IIE3 in combination with scFvs LA13-IIE3, TOB4-B11, or TOB5-D4) revealed an up to 500-fold increased antigen binding. This novel scFv-Fc-scFv antibody expression system allows simple and fast testing of various scFv combinations. Antibodies 2012-04-11 1 1 Article 10.3390/antib1010019 19 38 2073-4468 2012-04-11 doi: 10.3390/antib1010019 Stefanie Claudia Pohl Steffi Schwarz André Frenzel Thomas Schirrmann http://www.mdpi.com/2073-4468/1/1/2 Here we review recombinant proteins with a capability for dual-targeting. These molecules address two different antigens on the same tumor cell and therefore are called “dual-targeting agents”. By virtue of binding a chosen pair of antigens on the malignant cell, preferential binding to antigen double-positive over single-positive cells can be achieved when both are present in the same environment. Therapeutic effects of such agents are based on different modes of action: (1) They can act as pro-apoptotic agents or by inhibiting pro-survival signals; (2) The dual recognition moiety can be fused to effector-domains, such as bacterial toxins or other drugs, leading to the generation of bispecific antibody-drug conjugates (ADCs); (3) Dual-targeting agents can further be used to redirect an effector-cell to the tumor. A new generation of scFv-derived fusion proteins are the tandem single chain triplebodies (sctbs), which carry two scFv binding sites for antigens on the tumor cell plus a third, specific for a trigger molecule on an effector cell. The ability of preferential or selective targeting of antigen double-positive over single-positive cells opens attractive new perspectives for the use of dual-targeting agents in cancer therapy, and possibly also for the treatment of certain inflammatory and autoimmune disorders. Antibodies 2012-04-10 1 1 Review 10.3390/antib1010002 2 18 2073-4468 2012-04-10 doi: 10.3390/antib1010002 Ingo Schubert Christoph Stein Georg H. Fey http://www.mdpi.com/2073-4468/1/1/1 Secreted antibodies are a key player for exerting appropriate humoral immunity. For instance, in infectious diseases, poly-specific “natural” antibodies provide early protection, independent of T cell help. If this line of defense is crossed, T cell-dependent immune responses then generate a humoral memory provided by long-lived plasma cells secreting specific antibodies of adapted avidity and isotype. Secreted antibodies provide an efficient line of defense against re-infection and are backed up by specific memory B and T cells. In the field of humoral immunity, great discoveries including identification of a special T cell subset helping B cell activation (TFH), have been made in a last couple of years; however, important questions (such as mechanisms for affinity maturation of antibodies) still remain. [...] Antibodies 2011-12-30 1 1 Editorial 10.3390/antib1010001 1 1 2073-4468 2011-12-30 doi: 10.3390/antib1010001 Tomohiro Kurosaki