Optimization of Tris/EDTA/Sucrose (TES) periplasmic extraction for the recovery of functional scFv antibodies

Recent advancements in soluble expression of recombinant antibody fragments in microbial host systems

Recombinant fabs dominate the pharmaceutical pipelines today with microbial host systems continuing to be a major contributor toward their production. Escherichia coli is a versatile host for recombinant protein expression due to its simplicity, affordability, and ability to be cultivated at high cell density. It is particularly suitable for non-glycosylated proteins and small proteins. Despite the aforementioned benefits, the use of E. coli as the host for the synthesis of recombinant antibody fragments often suffers from low yield and reduced activity. In most cases, proteins are expressed as inclusion bodies and need to undergo refolding to achieve their active forms and this refolding step is generally low-yielding. In this article, we review the various approaches that researchers have taken to enhance the production of recombinant antibody fragments in E. coli. Molecular biology-oriented approaches such as cloning, chaperone-mediated folding, and host cell screening as well as process optimization involving examination of process parameters, media, and feeding have been addressed.

Periplasmic stress contributes to a trade-off between protein secretion and cell growth in Escherichia coli Nissle 1917

Maximizing protein secretion is an important target in the design of engineered living systems. In this paper, we characterize a trade-off between cell growth and per-cell protein secretion in the curli biofilm secretion system of Escherichia coli Nissle 1917. Initial characterization using 24-h continuous growth and protein production monitoring confirms decreased growth rates at high induction, leading to a local maximum in total protein production at intermediate induction. Propidium iodide (PI) staining at the endpoint indicates that cellular death is a dominant cause of growth reduction. Assaying variants with combinatorial constructs of inner and outer membrane secretion tags, we find that diminished growth at high production is specific to secretory variants associated with periplasmic stress mediated by outer membrane secretion and periplasmic accumulation of protein containing the outer membrane transport tag. RNA sequencing experiments indicate upregulation of known periplasmic stress response genes in the highly secreting variant, further implicating periplasmic stress in the growth-secretion trade-off. Overall, these results motivate additional strategies for optimizing total protein production and longevity of secretory engineered living systems Graphical Abstract.

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.

Periplasmic stress contributes to a tradeoff between protein secretion and cell growth in E. Coli Nissile

Maximizing protein secretion is an important target in the design of engineered living systems. In this paper, we characterize a tradeoff between cell growth and per cell protein secretion in the curli biofilm secretion system of E Coli Nissile 1917. Initial characterization using 24-hour continuous growth and protein production monitoring confirms decreased growth rates at high induction leading to a local maximum in total protein production at intermediate induction. Propidium iodide staining at the endpoint indicates that cellular death is a dominant cause of growth reduction. Assaying variants with combinatorial constructs of inner and outer membrane secretion tags, we find that diminished growth at high production is specific to secretory variants associated with accumulation of protein containing the outer membrane transport tag in the periplasmic space. RNA sequencing experiments indicate upregulation of known periplasmic stress response genes in the highly secreting variant, further implicating periplasmic stress in the growth-secretion tradeoff. Overall, these results motivate additional strategies for optimizing total protein production and longevity of secretory engineered living systems.

An overview on display systems (phage, bacterial, and yeast display) for production of anticancer antibodies; advantages and disadvantages

Antibodies as ideal therapeutic and diagnostic molecules are among the top-selling drugs providing considerable efficacy in disease treatment, especially in cancer therapy. Limitations of the hybridoma technology as routine antibody generation method in conjunction with numerous developments in molecular biology led to the development of alternative approaches for the streamlined identification of most effective antibodies. In this regard, display selection technologies such as phage display, bacterial display, and yeast display have been widely promoted over the past three decades as ideal alternatives to traditional methods. The display of antibodies on phages is probably the most widespread of these methods, although surface display on bacteria or yeast have been employed successfully, as well. These methods using various sizes of combinatorial antibody libraries and different selection strategies possessing benefits in screening potency, generating, and isolation of high affinity antibodies with low risk of immunogenicity. Knowing the basics of each method assists in the design and retrieval process of antibodies suitable for different diseases, including cancer. In this review, we aim to outline the basics of each library construction and its display method, screening and selection steps. The advantages and disadvantages in comparison to alternative methods, and their applications in antibody engineering will be explained. Finally, we will review approved or non-approved therapeutic antibodies developed by employing these methods, which may serve as therapeutic antibodies in cancer therapy.

Detecting and identifying glycoside hydrolases using cyclophellitol-derived activity-based probes

The ability to detect active enzymes in a complex mixture of folded proteins (e.g., secretome, cell lysate) generally relies on observations of catalytic ability, necessitating the development of an activity assay that is compatible with the sample and selective for the enzyme(s) of interest. Deconvolution of the contributions of different enzymes to an observed catalytic ability further necessitates an often-challenging protein separation. The advent of broadly reactive activity-based probes (ABPs) for retaining glycoside hydrolases (GHs) has enabled an alternative, often complementary, assay for active GHs. Using activity-based protein profiling (ABPP) techniques, many retaining glycoside hydrolases can be separated, detected, and identified with high sensitivity and selectivity. This chapter outlines ABPP methods for the detection and identification of retaining glycoside hydrolases from microbial sources, including protein sample preparation from bacterial lysates and fungal secretomes, enzyme labeling and detection via fluorescence, and enzyme identification using affinity-based enrichment coupled to peptide sequencing following isobaric labeling.

Production of antibodies in SHuffle Escherichia coli strains

Antibodies are globally important macromolecules, used for research, diagnostics, and as therapeutics. The common mammalian antibody immunoglobulin G (IgG) is a complex glycosylated macromolecule, composed of two heavy chains and two light chains held together by multiple disulfide bonds. For this reason, IgG and related antibody fragments are usually produced through secretion from mammalian cell lines, such as Chinese Hamster Ovary cells. However, there is growing interest in production of antibodies in prokaryotic systems due to the potential for rapid and cheap production in a highly genetically manipulable system. Research on oxidative protein folding in prokaryotes has enabled engineering of Escherichia coli strains capable of producing IgG and other disulfide bonded proteins in the cytoplasm, known as SHuffle. In this protocol, we provide a review of research on prokaryotic antibody production, guidelines on cloning of antibody expression constructs, conditions for an initial expression and purification experiment, and parameters which may be optimized for increased purification yields. Last, we discuss the limitations of prokaryotic antibody production, and highlight potential future avenues for research on antibody expression and folding.

Implementation of a Design of Experiments to Improve Periplasmic Yield of Functional ScFv Antibodies in a Phage Display Platform

Purpose: Production of functional recombinant antibody fragments in the periplasm of E. coli is a prerequisite step to achieve sufficient reagent for preclinical studies. Thus, the cost-effective and lab-scale production of antibody fragments demands the optimization of culture conditions.

Methods: The culture conditions such as temperature, optical density (OD₆₀₀) at induction, induction time, and IPTG concentration were investigated to optimize the functional expression of a phage-derived scFv molecule using a design of experiment (DoE). Additionally, the effects of different culture media and osmolyte supplements on the expression yield of scFv were examined.

Results: The developed 2FI regression model indicated the significant linear effect of the incubation temperature, the induction time, and the induction OD₆₀₀ on the expression yield of functional scFv. Besides, the statistical analysis indicated that two significant interactions of the temperature/induction time and the temperature/induction OD₆₀₀ significantly interplay to increase the yield. Further optimization showed that the expression level of functional scFv was the most optimal when the cultivation was undertaken either in the TB medium or in the presence of media supplements of 0.5 M sorbitol or 100 mM glycine betaine.

Conclusion: In the present study, for the first time, we successfully implemented DoE to comprehensively optimize the culture conditions for the expression of scFv molecules in a phage antibody display setting, where scFv molecules can be isolated from a tailor-made phage antibody library known as "Human Single Fold scFv Library I."