Expression and Characterization of a Functional Single-Chain Variable Fragment (scFv) Protein Recognizing MCF7 Breast Cancer Cells in E. coli Cytoplasm

Co-Expression of Chaperones for Improvement of Soluble Expression and Purification of An Anti-HER2 scFv in Escherichia Coli

Background

Single-chain fragment variable (scFv) is one of the most commonly used antibody fragments. They offer some advantages over full-length antibodies, including better penetration to target tissues. However, their functional production has been a challenge for manufacturers due to the potential misfolding and formation of inclusion bodies. Here we evaluated the soluble expression and purification of molecular chaperone co-expression.

Materials and Methods

E. coli BL21(DE3) cells were co-transformed with the mixture of plasmids pKJE7 and pET22b-scFv by the electroporation method. First, L-arabinose was added to induce the expression of molecular chaperones, and then IPTG was used as an inducer to start the expression of anti-HER2 scFv. The effect of cultivation temperature and IPTG concentration on soluble expression of the protein with or without chaperones was evaluated. The soluble expressed protein was subjected to native purification using the Ni-NTA affinity column.

Results

SDS-PAGE analysis confirmed the successful co-expression of anti-HER2-scFv and DnaK/DnaJ/GrpE chaperones. Co-expression with chaperones and low-temperature cultivation synergistically improved the soluble expression of anti-HER2 scFv. Co-expression with chaperone also exhibited an approximately four-fold increase in the final yield of purified soluble protein.

Conclusion

The combination of co-expression with chaperones and low temperature presented in this work may be useful for the improvement of commercial production of other scFvs in E. coli as functionally bioactive and soluble form.

Recombinant antibody production evolves into multiple options aimed at yielding reagents suitable for application-specific needs

BACKGROUND

Antibodies have been a pillar of basic research, while their relevance in clinical diagnostics and therapy is constantly growing. Consequently, the production of both conventional and fragment antibodies constantly faces more demanding challenges for the improvement of their quantity and quality. The answer to such an increasing need has been the development of a wide array of formats and alternative production platforms. This review offers a critical comparison and evaluation of the different options to help the researchers interested in expressing recombinant antibodies in their choice.

RESULTS

Rather than the compilation of an exhaustive list of the recent publications in the field, this review intendeds to analyze the development of the most innovative or fast-growing strategies. These have been illustrated with some significant examples and, when possible, compared with the existing alternatives. Space has also been given to those solutions that might represent interesting opportunities or that investigate critical aspects of the production optimization but for which the available data as yet do not allow for a definitive judgment.

CONCLUSIONS

The take-home message is that there is a clear process of progressive diversification concerning the antibody expression platforms and an effort to yield directly application-adapted immune-reagents rather than generic naked antibodies that need further in vitro modification steps before becoming usable.

High-yield production of functional soluble single-domain antibodies in the cytoplasm of Escherichia coli

Background

For their application in the area of diagnosis and therapy, single-domain antibodies (sdAbs) offer multiple advantages over conventional antibodies and fragments thereof in terms of size, stability, solubility, immunogenicity, production costs as well as tumor uptake and blood clearance. Thus, sdAbs have been identified as valuable next-generation targeting moieties for molecular imaging and drug delivery in the past years. Since these probes are much less complex than conventional antibody fragments, bacterial expression represents a facile method in order to produce sdAbs in large amounts as soluble and functional proteins.

Results

By the combined use of high cell density cultivation media with a genetically engineered E. coli mutant strain designed for the cytoplasmic formation of proper disulfide bonds, we achieved high level of intracellular sdAb production (up to 200 mg/L). Due to a carboxyterminal hexahistidine epitope, the soluble recombinant sdAbs could be purified by one-step immobilized metal affinity chromatography to apparent homogeneity and easily radiolabeled with ^99mTc within 1 h. The intradomain disulfide bridge being critical for the stability and functionality of the sdAb molecule was shown to be properly formed in ~96% of the purified proteins. In vitro binding studies confirmed the high affinity and specificity of the expressed sdAb 7C12 towards its molecular target.

Conclusions

Our study demonstrates an efficient cultivation and expression strategy for the production of substantial amounts of soluble and functional sdAbs, which may be adopted for high-yield production of other more complex proteins with multiple disulfides as well.

Phage display--a powerful technique for immunotherapy: 1. Introduction and potential of therapeutic applications

One of the most effective molecular diversity techniques is phage display. This technology is based on a direct linkage between phage phenotype and its encapsulated genotype, which leads to presentation of molecule libraries on the phage surface. Phage display is utilized in studying protein-ligand interactions, receptor binding sites and in improving or modifying the affinity of proteins for their binding partners. Generating monoclonal antibodies and improving their affinity, cloning antibodies from unstable hybridoma cells and identifying epitopes, mimotopes and functional or accessible sites from antigens are also important advantages of this technology. Techniques originating from phage display have been applied to transfusion medicine, neurological disorders, mapping vascular addresses and tissue homing of peptides. Phages have been applicable to immunization therapies, which may lead to development of new tools used for treating autoimmune and cancer diseases. This review describes the phage display technology and presents the recent advancements in therapeutic applications of phage display.