Construction and Periplasmic Expression of the Anti-EGFRvIII ScFv Antibody Gene in Escherichia coli

In silico analysis of the different variable domain oriented single-chain variable fragment antibody-antigen complexes

Single-chain variable fragment (scFv) antibodies hold great potential as diagnostic tools and therapeutic agents, especially for tumor cells. Since these applications require their production with improved properties, the design strategy of scFvs is crucial for their active, soluble, and high yield expression with high affinity towards their antigens. The order of VL and VH domains is one of the important parameters that affect the expression and binding affinity properties of scFvs. In addition, the optimum order of VL and VH domains could change for each scFv. In the present study, we used computer simulation tools to evaluate the effect of variable domain orientation on structure, stability, interacting residues of scFvs, and binding free energies of scFv-antigen complexes. We selected anti-HER2 scFv, which is specific for human epidermal growth receptor 2 (HER2) overexpressed in breast cancer, and anti-IL-1β scFv against IL-1β which is an important inflammatory biomarker, as model scFvs. Molecular dynamics simulations of the scFv-antigen complexes for 100 ns resulted in stability and compactness for both scFv constructs. Interaction and binding free energies calculated by the Molecular Mechanics-Poisson-Boltzmann Surface Area (MM-PBSA) approach suggested that the relative binding energies of anti-HER2 scFv-VLVH and anti-HER2 scFv-VHVL constructs had similar binding affinity towards HER2, while a relatively more negative binding free energy obtained between anti-IL-1β scFv-VHVL and IL-1β pointed to a higher binding affinity. The in silico approach and the results obtained here could be applied as a guide for future experimental interaction studies for highly specific scFvs used as biotechnological tools.Communicated by Ramaswamy H. Sarma.

A Shiga Toxin B-Subunit-Based Lectibody Boosts T Cell Cytotoxicity towards Gb3-Positive Cancer Cells

Aberrant glycosylation plays a crucial role in tumour progression and invasiveness. Tumour-associated carbohydrate antigens (TACAs) represent a valuable set of targets for immunotherapeutic approaches. The poor immunogenicity of glycan structures, however, requires a more effective and well-directed way of targeting TACAs on the surface of cancer cells than antibodies. The glycosphingolipid globotriaosylceramide (Gb3) is a well-established TACA present in a multitude of cancer types. Its overexpression has been linked to metastasis, invasiveness, and multidrug resistance. In the present study, we propose to use a dimeric fragment of the Shiga toxin B-subunit (StxB) to selectively target Gb3-positive cancer cells in a StxB-scFv UCHT1 lectibody. The lectibody, comprised of a lectin and the UCHT1 antibody fragment, was produced in E. coli and purified via Ni-NTA affinity chromatography. Specificity of the lectibody towards Gb3-positive cancer cell lines and specificity towards the CD3 receptor on T cells, was assessed using flow cytometry. We evaluated the efficacy of the lectibody in redirecting T cell cytotoxicity towards Gb3-overexpressing cancer cells in luciferase-based cytotoxicity in vitro assays. The StxB-scFv UCHT1 lectibody has proven specific for Gb3 and could induce the killing of up to 80% of Gb3-overexpressing cancer cells in haemorrhagic and solid tumours. The lectibody developed in this study, therefore, highlights the potential that lectibodies and lectins in general have for usage in immunotherapeutic approaches to boost the efficacy of established cancer treatments.

Preparation, Purification and Performance Evaluation of Polyclonal Antibody Against SARS-CoV-2 Produced in Rat

Purpose

Among all known human coronaviruses, some viruses (e.g., SARS-CoV-2) cause severe pneumonia or even death. With the regard to its spread and the importance of its rapid identification/treatment, and because pAbs are relatively cheap, able to bind to more sites on antigens and even neutralize them, this study was done for the production and purification of anti-SARS-CoV-2 polyclonal antibodies (pAb) in rats.

Methods

Viral antigen purification was performed by PEG/NaCl precipitation. The efficiency of the sucrose cushion method was also investigated to produce a purer antigen. Immunization was done and antibody purification was performed by ammonium sulfate precipitation (33%), dialysis, and ion-exchange chromatography. Western blotting and enzyme-linked immunosorbent assay (ELISA) were performed to verify the antibody specificity. All data were analyzed by SPSS software.

Results

The results showed that the amount of concentrated virus increased with the increase of PEG concentration. Moreover, the sucrose cushion method increased its purity. Besides, induction of immune response in rats for pAb production with high titers was reached via these antigens and ELISA/western blot results indicated a suitable antibody-antigen interaction. Additionally, it was shown that ion-exchange chromatography could be a suitable technique for IgG purification.

Conclusion

Herein, we presented a simple and cheap method for the purification of whole viral particles with relatively high quality. The results verified that these antigens could elicit a good immune response in the rat. The obtained pAbs showed a good specificity toward SARS-CoV-2 antigens. Accordingly, this study proposes a promising method for viral vaccine development.

Construction and Periplasmic Expression of a Bispecific Tandem scFv for Dual Targeting of Immune Checkpoints

Background

Immune checkpoints are molecules that act as regulators of immune system pathways. However, some tumor cells can express the ligands of immune checkpoints to escape from antitumor immune responses. Some agents, such as antibodies, can inhibit these checkpoints that prevent the immune system from targeting and killing cancer cells. The aim of this study was to express a novel bispecific tandem scFv in periplasmic space of Escherichia coli for simultaneous targeting of two immune checkpoints, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1).

Materials and Methods

The bispecific tandem scFv was constructed based on the variable regions gene of anti-PD1 and anti-CTLA-4 antibodies. The optimum codon for expression in E. coli was chemically synthesized and subcloned in periplasmic expression plasmid. After transformation, the effect of cultivation conditions on periplasmic expression of the protein in E. coli BL21(DE3) was evaluated. Then, the bispecific tandem scFv was purified and its binding ability to cells expressing PD-1 and CTLA-4 was evaluated.

Results

Expression of tandem scFv with a molecular weight of 55 kDa was verified by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotting analysis. The best condition for soluble periplasmic expression was obtained to be incubation with 0.5 mM isopropyl β-D-1-thiogalactopyranoside at 23°C. The protein was successfully purified using affinity chromatography with a final yield of 4.5 mg/L. Binding analysis confirmed the bioactivity of purified the tandem scFv.

Conclusion

This bispecific tandem scFv could be a potential candidate to cancer immunotherapy, although more biological activity assessments are still required to be carried out.

Designing and generating a single-chain fragment variable (scFv) antibody against IL2Rα (CD25): An in silico and in vitro study

OBJECTIVES

IL-2Rα plays a critical role in maintaining immune function. However, expression and secretion of CD25 in various malignant disorders and autoimmune diseases are now well established. Thus, CD25 is considered an important target candidate for antibody-based therapy. This study aimed to find the most suitable linker peptide to construct a functional anti-CD25 single-chain fragment variable (scFv) by bioinformatics studies and its production in a bacterial expression system.

MATERIALS AND METHODS

Here, the 3D structures of the scFvs with different linkers were predicted and molecular dynamics simulation was performed to compare their structures and dynamics. Then, interactions between five models of scFv and human CD25 were calculated via molecular docking. According to MD and docking results, the anti-CD25 scFvs with (Gly4Ser)3 linker were constructed and cloned into pET-22b(+). Then, recombinant plasmids were transformed into Escherichia coli Bl21 (DE3) for expression using IPTG and lactose as inducers. Anti-CD25 scFv was purified from the periplasm and detected by SDS-PAGE and Western blot. Afterward, functionality was evaluated using ELISA.

RESULTS

In silico analysis showed that the model containing (Gly4Ser)3 as a linker has more stability compared with other linkers. The results of SDS-PAGE, Western blot, and ELISA confirmed the accuracy of anti-CD25 scFv production and its ability to bind to the human CD25.

CONCLUSION

Conclusively, our work provides a theoretical and experimental basis for production of an anti-CD25 scFv, which may be applied for various malignant disorders and autoimmune diseases.

Improving the Expression of Human Granulocyte Colony Stimulating Factor in Escherichia coli by Reducing the GC-content and Increasing mRNA Folding Free Energy at 5'-Terminal End

Purpose: Strategy for improving the production of biopharmaceutical protein continues to develop due to increasing market demand. Human granulocyte colony stimulating factor (hG-CSF) is one of biopharmaceutical proteins that has many applications, and easily produced in Escherichia coli expression system. Previous studies reported that codon usage, rare codon, mRNA folding and GC-content at 5’-terminal end were crucial for protein production in E. coli. In the present study, the effect of reducing the GC-content and increasing the mRNA folding free energy at the 5’-terminal end on the expression level of hG-CSF proteins was investigated.

Methods: Synonymous codon substitutions were performed to generate mutant variants of open reading frame (ORF) with lower GC-content at 5’-terminal ends. Oligoanalyzer tool was used to calculate the GC content of eight codons sequence after ATG. Whereas, mRNA folding free energy was predicted using KineFold and RNAfold tools. The template DNA was amplified using three variant forward primers and one same reverse primer. Those DNA fragments were individually cloned into pJexpress414 expression vector and were confirmed using restriction and DNA sequencing analyses. The confirmed constructs were transformed into E. coli NiCo21(DE3) host cells and the recombinant protein was expressed using IPTG-induction. Total protein obtained were characterized using SDS-PAGE, Western blot and ImageJ software analyses.

Results: The result showed that the mutant variant with lower GC-content and higher mRNA folding free energy near the translation initiation region (TIR) could produce a higher amount of hG-CSF proteins compared to the original gene sequence.

Conclusion: This study emphasized the important role of the nucleotide composition immediately downstream the start codon to achieve high-yield protein product on heterologous expression in E. coli.

Evolution of Escherichia coli Expression System in Producing Antibody Recombinant Fragments

Antibodies and antibody-derived molecules are continuously developed as both therapeutic agents and key reagents for advanced diagnostic investigations. Their application in these fields has indeed greatly expanded the demand of these molecules and the need for their production in high yield and purity. While full-length antibodies require mammalian expression systems due to the occurrence of functionally and structurally important glycosylations, most antibody fragments and antibody-like molecules are non-glycosylated and can be more conveniently prepared in E. coli-based expression platforms. We propose here an updated survey of the most effective and appropriate methods of preparation of antibody fragments that exploit E. coli as an expression background and review the pros and cons of the different platforms available today. Around 250 references accompany and complete the review together with some lists of the most important new antibody-like molecules that are on the market or are being developed as new biotherapeutics or diagnostic agents.

Design and Production of Bispecific Antibodies

With the current biotherapeutic market dominated by antibody molecules, bispecific antibodies represent a key component of the next-generation of antibody therapy. Bispecific antibodies can target two different antigens at the same time, such as simultaneously binding tumor cell receptors and recruiting cytotoxic immune cells. Structural diversity has been fast-growing in the bispecific antibody field, creating a plethora of novel bispecific antibody scaffolds, which provide great functional variety. Two common formats of bispecific antibodies on the market are the single-chain variable fragment (scFv)-based (no Fc fragment) antibody and the full-length IgG-like asymmetric antibody. Unlike the conventional monoclonal antibodies, great production challenges with respect to the quantity, quality, and stability of bispecific antibodies have hampered their wider clinical application and acceptance. In this review, we focus on these two major bispecific types and describe recent advances in the design, production, and quality of these molecules, which will enable this important class of biologics to reach their therapeutic potential.

Evaluation of scFv protein recovery from E. coli by in vitro refolding and mild solubilization process

BACKGROUND

The production of therapeutically active single chain variable fragment (scFv) antibody is still challenging in E. coli due to the aggregation propensity of recombinant protein into inclusion bodies (IBs). However, recent advancement of biotechnology has shown substantial recovery of bioactive protein from such insoluble IBs by solubilization and refolding processes. In addition, gene fusion technology has also widely been used to improve the soluble protein production using E. coli. This study demonstrates that mild-solubilization and in vitro refolding strategies, both are capable to recover soluble scFv protein from bacterial IBs, although the degree of success is greatly influenced by different fusion tags with the target protein.

RESULTS

It was observed that the most commonly used fusion tag, i.e., maltose binding protein (MBP) was not only influenced the cytoplasmic expression in E. coli but also greatly improved the in vitro refolding yield of scFv protein. On the other hand, mild solubilization process potentially could recover soluble and functional scFv protein from non-classical IBs without assistance of any fusion tag and in vitro refolding step. The recovery yield achieved by mild solubilization process was also found higher than denaturation-refolding method except while scFv was refolded in fusion with MBP tag. Concomitantly, it was also observed that the soluble protein achieved by mild solubilization process was better structured and functionally more active than the one achieved by in vitro refolding method in the absence of MBP tag or refolding enhancer.

CONCLUSIONS

Maltose binding protein tagged scFv has shown better refolding and solubility yields as compare to mild solubilization process. However, in terms of cost, time and tag free nature, mild solubilization method for scFv recovery from bacterial IBs is considerable for therapeutic application and further structural studies.

Genetically engineering of Escherichia coli and immobilization on electrospun fibers for drug delivery purposes

Engineered EcN bacteria were entrapped in core-sheath fibersviacoaxial electrospinning or grafted on the fiber surfaceviacovalent binding or affinity adsorption.