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1.
Biotechnol J ; 19(7): e2300745, 2024 Jul.
Article in English | MEDLINE | ID: mdl-39014926

ABSTRACT

We developed a method to produce a soluble form of a single-chain fragment variable (scFv) targeting human epithelial growth factor receptor 2 (HER2) in Escherichia coli. By optimizing the orientations of the variable heavy (VH) and variable light (VL) domains and the His-tag, we identified the HL-His type antibody with the highest HER2-binding activity. Purification of HL-His yielded 40.7 mg from a 1 L culture, achieving >99% purity. The limit of detection was determined to be 2.9 ng, demonstrating high production yield, purity, and sensitivity. Moreover, we successfully labeled HER2+ cell lines with fluorescent dye-conjugated scFv, resulting in a significantly higher observed signal-to-background ratio, compared to that of HER2- cell lines. This highlights the potential of these fluorescent scFvs as valuable probes for HER2+ breast cancer diagnostics. Notably, the process for the complete scFv production was streamlined and required only 4-5 days. Additionally, the product maintained its activity after freeze storage, allowing for large-scale production and a wide range of practical applications.


Subject(s)
Escherichia coli , Receptor, ErbB-2 , Recombinant Proteins , Single-Chain Antibodies , Receptor, ErbB-2/immunology , Single-Chain Antibodies/genetics , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/isolation & purification , Humans , Escherichia coli/genetics , Escherichia coli/metabolism , Cell Line, Tumor , Breast Neoplasms/immunology
2.
Int J Mol Sci ; 25(13)2024 Jun 30.
Article in English | MEDLINE | ID: mdl-39000338

ABSTRACT

Chimeric antigen receptor (CAR) T cells represent a revolutionary immunotherapy that allows specific tumor recognition by a unique single-chain fragment variable (scFv) derived from monoclonal antibodies (mAbs). scFv selection is consequently a fundamental step for CAR construction, to ensure accurate and effective CAR signaling toward tumor antigen binding. However, conventional in vitro and in vivo biological approaches to compare different scFv-derived CARs are expensive and labor-intensive. With the aim to predict the finest scFv binding before CAR-T cell engineering, we performed artificial intelligence (AI)-guided molecular docking and steered molecular dynamics analysis of different anti-CD30 mAb clones. Virtual computational scFv screening showed comparable results to surface plasmon resonance (SPR) and functional CAR-T cell in vitro and in vivo assays, respectively, in terms of binding capacity and anti-tumor efficacy. The proposed fast and low-cost in silico analysis has the potential to advance the development of novel CAR constructs, with a substantial impact on reducing time, costs, and the need for laboratory animal use.


Subject(s)
Artificial Intelligence , Ki-1 Antigen , Molecular Docking Simulation , Molecular Dynamics Simulation , Receptors, Chimeric Antigen , Single-Chain Antibodies , Receptors, Chimeric Antigen/immunology , Receptors, Chimeric Antigen/metabolism , Receptors, Chimeric Antigen/genetics , Single-Chain Antibodies/immunology , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/genetics , Humans , Ki-1 Antigen/immunology , Ki-1 Antigen/metabolism , Animals , Mice , Protein Binding , Surface Plasmon Resonance
3.
Glycobiology ; 34(8)2024 Jun 22.
Article in English | MEDLINE | ID: mdl-38963938

ABSTRACT

Heparan sulfate (HS) is a linear polysaccharide with high structural and functional diversity. Detection and localization of HS in tissues can be performed using single chain variable fragment (scFv) antibodies. Although several anti-HS antibodies recognizing different sulfation motifs have been identified, little is known about their interaction with HS. In this study the interaction between the scFv antibody HS4C3 and heparin was investigated. Heparin-binding lysine and arginine residues were identified using a protect and label methodology. Site-directed mutagenesis was applied to further identify critical heparin-binding lysine/arginine residues using immunohistochemical and biochemical assays. In addition, computational docking of a heparin tetrasaccharide towards a 3-D homology model of HS4C3 was applied to identify potential heparin-binding sites. Of the 12 lysine and 15 arginine residues within the HS4C3 antibody, 6 and 9, respectively, were identified as heparin-binding. Most of these residues are located within one of the complementarity determining regions (CDR) or in their proximity. All basic amino acid residues in the CDR3 region of the heavy chain were involved in binding. Computational docking showed a heparin tetrasaccharide close to these regions. Mutagenesis of heparin-binding residues reduced or altered reactivity towards HS and heparin. Identification of heparin-binding arginine and lysine residues in HS4C3 allows for better understanding of the interaction with HS and creates a framework to rationally design antibodies targeting specific HS motifs.


Subject(s)
Heparin , Heparitin Sulfate , Heparitin Sulfate/chemistry , Heparitin Sulfate/immunology , Heparitin Sulfate/metabolism , Heparin/chemistry , Heparin/metabolism , Molecular Docking Simulation , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/immunology , Single-Chain Antibodies/genetics , Humans , Animals , Mutagenesis, Site-Directed , Binding Sites , Amino Acid Sequence
4.
Nat Commun ; 15(1): 5255, 2024 Jun 19.
Article in English | MEDLINE | ID: mdl-38898050

ABSTRACT

GPRC5D is an atypical Class C orphan G protein-coupled receptor. Its high expression on the surface of multiple myeloma cells has rendered it an attractive target for therapeutic interventions, including monoclonal antibodies, CAR-T cells, and T-cell engagers. Despite its therapeutic potential, the insufficient understanding regarding of the receptor's structure and antibody recognition mechanism has impeded the progress of effective therapeutic development. Here, we present the structure of GPRC5D in complex with a preclinical-stage single-chain antibody (scFv). Our structural analysis reveals that the GPRC5D presents a close resemblance to the typical Class C GPCRs in the transmembrane region. We identify a distinct head-to-head homodimer arrangement and interface mainly involving TM4, setting it apart from other Class C homo- or hetero-dimers. Furthermore, we elucidate the binding site engaging a sizable extracellular domain on GPRC5D for scFv recognition. These insights not only unveil the distinctive dimer organization of this unconventional Class C GPCR but also hold the potential to advance drug development targeting GPRC5D for the treatment of multiple myeloma.


Subject(s)
Multiple Myeloma , Protein Multimerization , Receptors, G-Protein-Coupled , Single-Chain Antibodies , Humans , Multiple Myeloma/immunology , Receptors, G-Protein-Coupled/immunology , Receptors, G-Protein-Coupled/metabolism , Single-Chain Antibodies/immunology , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/metabolism , Protein Binding , Binding Sites , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal/chemistry
5.
Protein Sci ; 33(7): e5084, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38923711

ABSTRACT

Small antibody fragments have recently been used as alternatives to full-length monoclonal antibodies in therapeutic applications. One of the most popular fragment antibodies is single-chain fragment variables (scFvs), consisting of variable heavy (VH) and variable light (VL) domains linked by a flexible peptide linker. scFvs have small molecular sizes, which enables good tissue penetration and low immunogenicity. Despite these advantages, the use of scFvs, especially for therapeutic purpose, is still limited because of the difficulty to regulate the binding activity and conformational stability. In this study, we constructed and analyzed 10 scFv fragments derived from 10 representatives of FDA-approved mAbs to evaluate their physicochemical properties. Differential scanning calorimetry analysis showed that scFvs exhibited relatively high but varied thermostability, from 50 to 70°C of melting temperatures, and different unfolding cooperativity. Surface plasmon resonance analysis revealed that scFvs fragments that exhibit high stability and cooperative unfolding likely tend to maintain antigen binding. This study demonstrated the comprehensive physicochemical properties of scFvs derived from FDA-approved antibodies, providing insights into antibody design and development.


Subject(s)
Protein Stability , Single-Chain Antibodies , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/immunology , Humans , Antibodies, Monoclonal/chemistry , Antibodies, Monoclonal/immunology , Calorimetry, Differential Scanning , Protein Binding
6.
Biosens Bioelectron ; 261: 116511, 2024 Oct 01.
Article in English | MEDLINE | ID: mdl-38917513

ABSTRACT

Single-chain fragment variables (scFvs), composed of variable heavy and light chains joined together by a peptide linker, can be produced using a cost-effective bacterial expression system, making them promising candidates for pharmaceutical applications. However, a versatile method for monitoring recombinant-protein production has not yet been developed. Herein, we report a novel anti-scFv aptamer-based biosensing system with high specificity and versatility. First, anti-scFv aptamers were screened using the competitive systematic evolution of ligands by exponential enrichment, focusing on a unique scFv-specific peptide linker. We selected two aptamers, P1-12 and P2-63, with KD = 2.1 µM or KD = 1.6 µM toward anti-human epidermal growth factor receptor (EGFR) scFv, respectively. These two aptamers can selectively bind to scFv but not to anti-EGFR Fv. Furthermore, the selected aptamers recognized various scFvs with different CDRs, such as anti-4-1BB and anti-hemoglobin scFv, indicating that they recognized a unique peptide linker region. An electrochemical sensor for anti-EGFR scFv was developed using anti-scFv aptamers based on square wave voltammetry. Thus, the constructed sensor could monitor anti-EGFR scFv concentrations in the range of 10-500 nM in a diluted medium for bacterial cultivation, which covered the expected concentration range for the recombinant production of scFvs. These achievements promise the realization of continuous monitoring sensors for pharmaceutical scFv, which will enable the real-time and versatile monitoring of large-scale scFv production.


Subject(s)
Aptamers, Nucleotide , Biosensing Techniques , ErbB Receptors , Single-Chain Antibodies , Aptamers, Nucleotide/chemistry , Biosensing Techniques/methods , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/immunology , Humans , Recombinant Proteins/genetics , SELEX Aptamer Technique/methods , Electrochemical Techniques/methods
7.
Arch Biochem Biophys ; 758: 110068, 2024 Aug.
Article in English | MEDLINE | ID: mdl-38909835

ABSTRACT

Affinity maturation increases antigen-binding affinity and specificity of antibodies by somatic hypermutation. Various monoclonal antibodies against (4-hydroxy-3-nitrophenyl)acetyl (NP) were obtained during affinity maturation. Among them, highly matured anti-NP antibodies, such as E11 and E3, possess Cys96H and Cys100H in the complementarity-determining region 3 of the heavy chain, which would form a disulfide bond. In this study, we evaluated the effects of disulfide bonds on antigen binding by generating single-chain Fv (scFv) antibodies of E11 and its mutants, E11_C96KH/C100EH and E11_C96KH/C100QH, and determined their antigen-binding thermodynamics and kinetics. The binding affinities of the Cys mutants were lower than that of E11 scFv, indicating that the disulfide bond contributed to antigen binding, especially for stable complex formation. This was also supported by the decreased affinity of E11 scFv in the presence of a reducing agent. The crystal structures of NP-free and NP-bound E11 scFvs were determined at high resolution, showing the existence of a disulfide bond between Cys96H and Cys100H, and the antigen recognition mechanism, which could be compared with those of other anti-NP antibodies, such as germline-type N1G9 and matured-type C6, as reported previously. These structures could explain the molecular basis of changes in antigen-binding affinity and thermal stability in the absence or presence of antigens. Small-angle X-ray scattering further showed a local conformational change in E11 scFv upon antigen binding in solution.


Subject(s)
Antibody Affinity , Complementarity Determining Regions , Disulfides , Single-Chain Antibodies , Disulfides/chemistry , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/immunology , Single-Chain Antibodies/genetics , Complementarity Determining Regions/chemistry , Humans , Antibodies, Monoclonal/chemistry , Antibodies, Monoclonal/immunology , Animals , Thermodynamics , Kinetics , Crystallography, X-Ray , Models, Molecular
8.
ACS Appl Bio Mater ; 7(7): 4486-4496, 2024 Jul 15.
Article in English | MEDLINE | ID: mdl-38886921

ABSTRACT

Human tissue kallikrein-related peptidase 7 (KLK7) is a serine protease implicated in the physiology of skin desquamation, and its uncontrolled activity can lead to chronic diseases such as psoriasis, atopic dermatitis, and Netherton syndrome. For this reason, kallikrein 7 has been identified as a potential therapeutic target. This work aimed to evaluate Pluronic (PL) hydrogels as topical carriers of four specific scFv-Fc antibodies to inhibit KLK7. The hydrogels comprised PL F127 (30% w/v) alone and a binary F127/P123 (28-2% w/v) system. Each formulation was loaded with 1 µg/mL of each antibody and characterized by physicochemical and pharmaceutical techniques, considering antibody-micelle interactions and hydrogel behavior as smart delivery systems. Results showed that the antibodies were successfully loaded into the PL-based systems, and the sol-gel transition temperature was shifted to high values after the P123 addition. The antibodies released from the gels preserved their rheological properties (G' > G'', 35- to 41-fold) and inhibitory activity against KLK7, even after 24 h. This work presented potential agents targeting KLK7 that may provide strategies for treating skin abnormalities.


Subject(s)
Hydrogels , Kallikreins , Hydrogels/chemistry , Hydrogels/pharmacology , Kallikreins/antagonists & inhibitors , Kallikreins/metabolism , Humans , Materials Testing , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/pharmacology , Biocompatible Materials/chemistry , Biocompatible Materials/pharmacology , Particle Size , Poloxamer/chemistry , Recombinant Proteins/pharmacology , Recombinant Proteins/chemistry , Recombinant Proteins/administration & dosage , Temperature , Skin Diseases/drug therapy , Skin Diseases/pathology
9.
J Biol Chem ; 300(6): 107397, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38763332

ABSTRACT

Constant domains in antibody molecules at the level of the Fab (CH1 and CL) have long been considered to be simple scaffolding elements that physically separate the paratope-defining variable (V) region from the effector function-mediating constant (C) regions. However, due to recent findings that C domains of different isotypes can modulate the fine specificity encoded in the V region, elucidating the role of C domains in shaping the paratope and influencing specificity is a critical area of interest. To dissect the relative contributions of each C domain to this phenomenon, we generated antibody fragments with different C regions omitted, using a set of antibodies targeting capsular polysaccharides from the fungal pathogen, Cryptococcus neoformans. Antigen specificity mapping and functional activity measurements revealed that V region-only antibody fragments exhibited poly-specificity to antigenic variants and extended to recognition of self-antigens, while measurable hydrolytic activity of the capsule was greatly attenuated. To better understand the mechanistic origins of the remarkable loss of specificity that accompanies the removal of C domains from identical paratopes, we performed molecular dynamics simulations which revealed increased paratope plasticity in the scFv relative to the corresponding Fab. Together, our results provide insight into how the remarkable specificity of immunoglobulins is governed and maintained at the level of the Fab through the enforcement of structural restrictions on the paratope by CH1 domains.


Subject(s)
Cryptococcus neoformans , Epitopes , Cryptococcus neoformans/immunology , Cryptococcus neoformans/chemistry , Epitopes/chemistry , Epitopes/immunology , Immunoglobulin Constant Regions/chemistry , Immunoglobulin Constant Regions/genetics , Molecular Dynamics Simulation , Immunoglobulin Fab Fragments/chemistry , Immunoglobulin Fab Fragments/immunology , Immunoglobulin Fab Fragments/metabolism , Humans , Antibody Specificity , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/immunology , Single-Chain Antibodies/genetics , Animals , Antibodies, Fungal/immunology , Antibodies, Fungal/chemistry
10.
J Immunoassay Immunochem ; 45(4): 307-324, 2024 Jul 03.
Article in English | MEDLINE | ID: mdl-38776466

ABSTRACT

Single Chain Variable Fragment (scFv), a small fragment of antibody can be used to substitute the monoclonal antibody for diagnostic purposes. Production of scFv in Escherichia coli host has been a challenge due to the potential miss-folding and formation of inclusion bodies. This study aimed to express anti-CHIKV E2 scFv which previously designed specifically for Asian strains by co-expression of three chaperones that play a role in increasing protein solubility; GroEL, GroES, and Trigger Factor. The scFv and chaperones were expressed in Origami B E. coli host under the control of the T7 promoter, and purified using a Ni-NTA column. Functional assay of anti-CHIKV-E2 scFv was examined by electrochemical immunosensor using gold modified Screen Printed Carbon Electrode (SPCE), and characterized by differential pulses voltammetry (DPV) using K3[Fe(CN)6] redox system and scanning microscope electron (SEM). The experimental condition was optimized using the Box-Behnken design. The results showed that co-expression of chaperone increased the soluble scFv yield from 54.405 µg/mL to 220.097 µg/mL (~5×). Furthermore, scFv can be used to detect CHIKV-E2 in immunosensor electrochemistry with a detection limit of 0.74048 ng/mL and a quantification limit of 2,24388 ng/mL. Thus, the scFv-anti-CHIKV-E2 can be applied as a bioreceptor in another immunoassay method.


Subject(s)
Biosensing Techniques , Electrochemical Techniques , Escherichia coli , Molecular Chaperones , Single-Chain Antibodies , Single-Chain Antibodies/immunology , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/genetics , Escherichia coli/metabolism , Escherichia coli/genetics , Molecular Chaperones/immunology , Immunoassay/methods
11.
Protein Sci ; 33(6): e5017, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38747382

ABSTRACT

Biparatopic antibodies (bpAbs) are engineered antibodies that bind to multiple different epitopes within the same antigens. bpAbs comprise diverse formats, including fragment-based formats, and choosing the appropriate molecular format for a desired function against a target molecule is a challenging task. Moreover, optimizing the design of constructs requires selecting appropriate antibody modalities and adjusting linker length for individual bpAbs. Therefore, it is crucial to understand the characteristics of bpAbs at the molecular level. In this study, we first obtained single-chain variable fragments and camelid heavy-chain variable domains targeting distinct epitopes of the metal binding protein MtsA and then developed a novel format single-chain bpAb connecting these fragment antibodies with various linkers. The physicochemical properties, binding activities, complex formation states with antigen, and functions of the bpAb were analyzed using multiple approaches. Notably, we found that the assembly state of the complexes was controlled by a linker and that longer linkers tended to form more compact complexes. These observations provide detailed molecular information that should be considered in the design of bpAbs.


Subject(s)
Single-Chain Antibodies , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/genetics , Single-Chain Antibodies/immunology , Animals , Humans , Protein Engineering/methods , Epitopes/chemistry , Epitopes/immunology , Immunoglobulin Heavy Chains/chemistry , Immunoglobulin Heavy Chains/genetics , Immunoglobulin Heavy Chains/immunology
12.
Cell Chem Biol ; 31(5): 944-954.e5, 2024 May 16.
Article in English | MEDLINE | ID: mdl-38653243

ABSTRACT

Agonist antibodies are being pursued for therapeutic applications ranging from neurodegenerative diseases to cancer. For the tumor necrosis factor (TNF) receptor superfamily, higher-order clustering of three or more receptors is key to their activation, which can be achieved using antibodies that recognize two unique epitopes. However, the generation of biepitopic (i.e., biparatopic) antibodies typically requires animal immunization and is laborious and unpredictable. Here, we report a simple method for identifying biepitopic antibodies that potently activate TNF receptors without the need for additional animal immunization. Our approach uses existing, receptor-specific IgGs, which lack intrinsic agonist activity, to block their corresponding epitopes, then selects single-chain antibodies that bind accessible epitopes. The selected antibodies are fused to the light chains of IgGs to generate human tetravalent antibodies. We highlight the broad utility of this approach by converting several clinical-stage antibodies against OX40 and CD137 (4-1BB) into biepitopic antibodies with potent agonist activity.


Subject(s)
Epitopes , Humans , Epitopes/immunology , Epitopes/chemistry , Animals , Receptors, Tumor Necrosis Factor/agonists , Receptors, Tumor Necrosis Factor/immunology , Receptors, Tumor Necrosis Factor/metabolism , Tumor Necrosis Factor Receptor Superfamily, Member 9/agonists , Tumor Necrosis Factor Receptor Superfamily, Member 9/immunology , Tumor Necrosis Factor Receptor Superfamily, Member 9/metabolism , Tumor Necrosis Factor Receptor Superfamily, Member 9/antagonists & inhibitors , Receptors, OX40/agonists , Receptors, OX40/immunology , Receptors, OX40/metabolism , Receptors, OX40/antagonists & inhibitors , Antibodies/immunology , Single-Chain Antibodies/immunology , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/pharmacology , Mice
13.
J Am Chem Soc ; 146(18): 12454-12462, 2024 May 08.
Article in English | MEDLINE | ID: mdl-38687180

ABSTRACT

Quantum defects in single-walled carbon nanotubes promote exciton localization, which enables potential applications in biodevices and quantum light sources. However, the effects of local electric fields on the emissive energy states of quantum defects and how they can be controlled are unexplored. Here, we investigate quantum defect sensitization by engineering an intrinsically disordered protein to undergo a phase change at a quantum defect site. We designed a supercharged single-chain antibody fragment (scFv) to enable a full ligand-induced folding transition from an intrinsically disordered state to a compact folded state in the presence of a cytokine. The supercharged scFv was conjugated to a quantum defect to induce a substantial local electric change upon ligand binding. Employing the detection of a proinflammatory biomarker, interleukin-6, as a representative model system, supercharged scFv-coupled quantum defects exhibited robust fluorescence wavelength shifts concomitant with the protein folding transition. Quantum chemical simulations suggest that the quantum defects amplify the optical response to the localization of charges produced upon the antigen-induced folding of the proteins, which is difficult to achieve in unmodified nanotubes. These findings portend new approaches to modulate quantum defect emission for biomarker sensing and protein biophysics and to engineer proteins to modulate binding signal transduction.


Subject(s)
Quantum Theory , Single-Chain Antibodies/chemistry , Nanotubes, Carbon/chemistry , Protein Folding , Interleukin-6 , Humans , Intrinsically Disordered Proteins/chemistry
14.
Anal Bioanal Chem ; 416(12): 2929-2939, 2024 May.
Article in English | MEDLINE | ID: mdl-38491149

ABSTRACT

Deoxynivalenol (DON) is a mycotoxin that widely distributes in various foods and seriously threatens food safety. To minimize the consumers' dietary exposure to DON, there is an urgent demand for developing rapid and sensitive detection methods for DON in food. In this study, a bifunctional single-chain variable fragment (scFv) linked alkaline phosphatase (ALP) fusion protein was developed for rapid and sensitive detection of deoxynivalenol (DON). The scFv gene was chemically synthesized and cloned into the expression vector pET25b containing the ALP gene by homologous recombination. The prokaryotic expression, purification, and activity analysis of fusion proteins (scFv-ALP and ALP-scFv) were well characterized and performed. The interactions between scFv and DON were investigated by computer-assisted simulation, which included hydrogen bonds, hydrophobic interactions, and van der Waals forces. The scFv-ALP which showed better bifunctional activity was selected for developing a direct competitive enzyme-linked immunosorbent assay (dc-ELISA) for DON in cereals. The dc-ELISA takes 90 min for one test and exhibits a half inhibitory concentration (IC50) of 11.72 ng/mL, of which the IC50 was 3.08-fold lower than that of the scFv-based dc-ELISA. The developed method showed high selectivity for DON, and good accuracy was obtained from the spike experiments. Furthermore, the detection results of actual cereal samples analyzed by the method correlated well with that determined by high-performance liquid chromatography (R2=0.97165). These results indicated that the scFv-ALP is a promising bifunctional probe for developing the one-step colorimetric immunoassay, providing a new strategy for rapid and sensitive detection of DON in cereals.


Subject(s)
Alkaline Phosphatase , Edible Grain , Enzyme-Linked Immunosorbent Assay , Recombinant Fusion Proteins , Single-Chain Antibodies , Trichothecenes , Trichothecenes/analysis , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/genetics , Single-Chain Antibodies/immunology , Edible Grain/chemistry , Alkaline Phosphatase/chemistry , Enzyme-Linked Immunosorbent Assay/methods , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/chemistry , Food Contamination/analysis , Limit of Detection
15.
Anal Methods ; 16(12): 1756-1762, 2024 Mar 22.
Article in English | MEDLINE | ID: mdl-38440844

ABSTRACT

Single-chain variable fragments (scFvs) are valuable in the development of immunoassays for pesticide detection. In this study, scFvs specific to thiamethoxam (Thi) were successfully isolated from a library generated by chicken immunization through heterologous coating selection. These scFvs were subsequently expressed with fusion with an Avi tag and alkaline phosphatase. After combination and optimization, a scFv-biotin based enzyme linked immunosorbent assay (ELISA) was developed for the detection of Thi, demonstrating an impressive half-maximum signal inhibition concentration (IC50) of 30 ng mL-1 and a limit of detection (LOD) of 1.8 ng mL-1. The immunoassay exhibited minimal cross-reactivity with other neonicotinoid insecticides, except for 7.5% for imidacloprid and 6.7% for imidaclothiz. The accuracy of the assay was confirmed by testing spiked samples of apple, pear, cabbage, and cucumber, which resulted in average recoveries ranging between 82% and 119%, closely aligning with the results obtained through high-performance liquid chromatography. Therefore, the chicken scFv-biotin based assay showed promise as a high-throughput screening tool for Thi in agricultural samples.


Subject(s)
Insecticides , Single-Chain Antibodies , Animals , Thiamethoxam , Single-Chain Antibodies/genetics , Single-Chain Antibodies/chemistry , Chickens , Biotin , Insecticides/analysis
16.
J Labelled Comp Radiopharm ; 67(5): 168-179, 2024 May 15.
Article in English | MEDLINE | ID: mdl-38485465

ABSTRACT

Breast cancer is the most common diagnosed cancer, and the second cause of cancer death among women, worldwide. HER2 overexpression occurred in approximately 15% to 20% of breast cancers. Invasive biopsy method has been used for detection of HER2 overexpression. HER2-targeted imaging via an appropriate radionuclide is a promising method for sensitive and accurate identification of HER2+ primary and metastatic lesions. 99mTc-anti-HER2 scFv can specifically target malignancies and be used for diagnosis of the cancer type and metastasis as well as treatment of breast cancer. We radiolabeled anti-HER2 scFv that was expressed in Escherichia coli and purified through Ni-NTA resin under native condition with 99mTc-tricarbonyl formed from boranocarbonate. HER2-based ELISA, BCA, TLC, and HPLC were used in this study. In the current study, anti-HER2 scFv was lyophilized before radiolabeling. It was found that freeze-drying did not change the binding activity of anti-HER2 scFv to HER2. Results demonstrated direct anti-HER2 scFv radiolabeling by 99mTc-tricarbonyl to hexahistidine sequence (His-tag) without any changes in biological activity and radiochemical purity of around 98%. Stability analysis revealed that 99mTc-anti-HER2 scFv is stable for at least 24 h in PBS buffer, normal saline, human plasma proteins, and histidine solution.


Subject(s)
Isotope Labeling , Organotechnetium Compounds , Receptor, ErbB-2 , Single-Chain Antibodies , Receptor, ErbB-2/metabolism , Receptor, ErbB-2/immunology , Humans , Single-Chain Antibodies/chemistry , Organotechnetium Compounds/chemistry , Drug Stability , Technetium/chemistry , Radiopharmaceuticals/chemistry
17.
Biotechnol Prog ; 40(3): e3439, 2024.
Article in English | MEDLINE | ID: mdl-38377106

ABSTRACT

Programmed cell death-ligand 1 (PDL1) is a transmembrane protein that is characterized as an immune regulatory molecule. We recently developed a recombinant single-chain fragment of variable domain (scFv) against PDL1, which showed high binding efficiency to purified recombinant PDL1 protein. However, at that time, proof-of-concept data for the effect of scFv using PDL1-expressing cells was lacking. In this study, we conducted two kinds of cell-based immunoassays, western blotting and enzyme-linked immunosorbent assay, using anti-PDL1 scFv. The results indicate that scFv can selectively and sensitively detect PDL1 from PDL1 positive human cancer cell lines. Our findings suggest that scFv could be used as a potential PDL1 inhibitor agent and probe for cell-based immunoassays to detect PDL1.


Subject(s)
B7-H1 Antigen , Recombinant Proteins , Single-Chain Antibodies , Humans , B7-H1 Antigen/immunology , B7-H1 Antigen/metabolism , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/immunology , Single-Chain Antibodies/genetics , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Recombinant Proteins/metabolism , Cell Line, Tumor , Enzyme-Linked Immunosorbent Assay
18.
Comput Biol Med ; 170: 108091, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38295473

ABSTRACT

BACKGROUND: The SARS-CoV-2 has led to a worldwide disaster. Thus, developing prophylactics/therapeutics is required to overcome this public health issue. Among these, producing the anti-SARS-CoV-2 single-chain variable fragment (scFv) antibodies has attracted a significant attention. Accordingly, this study aims to address this question: Is it possible to bioinformatics-based design of a potent anti-SARS-CoV-2 scFv as an alternative to current production approaches? METHOD: Using the complexed SARS-CoV-2 spike-antibodies, two sets analyses were performed: (1) B-cell epitopes (BCEs) prediction in the spike receptor-binding domain (RBD) region as a parameter for antibody screening; (2) the computational analysis of antibodies variable domains (VH/VL). Based on these primary screenings, and docking/binding affinity rating, one antibody was selected. The protein-protein interactions (PPIs) among the selected antibody-epitope complex were predicted and its epitope conservancy was also evaluated. Thereafter, some elements were added to the final scFv: (1) the PelB signal peptide; (2) a GSGGGGS linker to connect the VH-VL. Finally, this scFv was analyzed/optimized using various web servers. RESULTS: Among the antibody library, only one met the various criteria for being an efficient scFv candidate. Moreover, no interaction was predicted between its paratope and RBD hot-spot residues of SARS-CoV-2 variants-of-Concern (VOCs). CONCLUSIONS: Herein, a step-by-step bioinformatics platform has been introduced to bypass some barriers of traditional antibody production approaches. Based on existing literature, the current study is one of the pioneer works in the field of bioinformatics-based scFv production. This scFv may be a good candidate for diagnostics/therapeutics design against the SARS-CoV-2 as an emerging aggressive pathogen.


Subject(s)
COVID-19 , Single-Chain Antibodies , Vaccines , Humans , Single-Chain Antibodies/chemistry , SARS-CoV-2 , Antibodies, Viral , Epitopes, B-Lymphocyte/chemistry , Computational Biology , COVID-19 Testing
19.
Biochem Biophys Res Commun ; 691: 149308, 2024 Jan 08.
Article in English | MEDLINE | ID: mdl-38029542

ABSTRACT

This study tried to generate anti-idiotypic antibodies (Ab2s) which mimic Cry2Aa toxin using a phage-display antibody library (2.8 × 107 CFU/mL). The latter was constructed from a mouse immunized with F (ab')2 fragments digested from anti-Cry2Aa polyclonal antibodies. The F (ab')2 fragments and Plutella xylostella (P. xylostella) brush border membrane vesicles (BBMV) were utilized as targets for selection. Eight mouse phage-display single-chain variable fragments (scFvs) were isolated and identified by enzyme-linked immunoassay (ELISA), PCR and DNA sequencing after four rounds of biopanning. Among them, M3 exhibited the highest binding affinity with F (ab')2, while M4 bound the best with the toxin binding region of cadherin of P. xylostella (PxCad-TBR). Both of these two fragments were chosen for prokaryotic expression. The expressed M3 and M4 proteins with molecular weights of 30 kDa were purified. The M4 showed a binding affinity of 29.9 ± 2.4 nM with the PxCad-TBR and resulted in 27.8 ± 4.3 % larvae mortality against P. xylostella. Computer-assisted molecular modeling and docking analysis showed that mouse scFv M4 mimicked some Cry2Aa toxin binding sites when interacting with PxCad-TBR. Therefore, anti-idiotypic antibodies generated by BBMV-based screening could be useful for the development of new bio-insecticides as an alternative to Cry2Aa toxin for pest control.


Subject(s)
Bacteriophages , Insecticides , Lepidoptera , Single-Chain Antibodies , Animals , Mice , Gene Library , Single-Chain Antibodies/chemistry , Endotoxins/metabolism , Antibodies, Anti-Idiotypic , Peptide Library
20.
J Vis Exp ; (201)2023 Nov 10.
Article in English | MEDLINE | ID: mdl-38009747

ABSTRACT

Single-chain fragment variable (scFv) antibodies were previously constructed of variable light and heavy chains joined by a (Gly4-Ser) 3 linker. The linker was created using molecular modeling software as a loop structure. Here, we introduce a protocol forin silico analysis of a complete scFv antibody that interacts with the epidermal growth factor receptor (EGFR). The homology modeling, with Pyrx of protein-protein docking and molecular dynamic simulation of the interacting scFv antibody and EGFR First, the authors used a protein structure modeling program and Python for homology modeling, and the antibody scFv structure was modeled for homology. The investigators downloaded Pyrx software as a platform in the docking study. The Molecular dynamic simulation was run using modeling software. Results show that when the MD simulation was subjected to energy minimization, the protein model had the lowest binding energy (-5.4 kcal/M). In addition, the MD simulation in this study showed that the docked EGFR-scFv antibody was stable for 20-75 ns when the movement of the structure increased sharply to 7.2 Å. In conclusion, in silicoanalysiswas performed, and the molecular docking and molecular dynamics simulations of the scFv antibody proved the effectiveness of the designed immune-therapeutic drug scFv as a specific drug therapy for EGFR.


Subject(s)
Single-Chain Antibodies , Molecular Docking Simulation , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/metabolism , Molecular Dynamics Simulation , ErbB Receptors/metabolism
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