High-throughput, high-level production of PS-tag-fused single-chain Fvs by microplate-based culture

Development of a novel and broadly applicable sandwich ELISA assay based on rabbit single-chain variable fragments and a modified Ig-binding domain of protein L fused to a polystyrene-binding peptide

Most of currently available sandwich-type enzyme-linked immunosorbent assays (ELISA) require the use of full-length animal-derived antibodies which poses welfare criticisms and are often expensive to produce. There is therefore a strong demand for the development of more affordable and animal-free methods to produce antibodies for sandwich ELISA assay. To address these issues, we propose here the development of a new technology based on two complementary rabbit single-chain variable fragments (scFvs) and an Ig-binding domain of protein L (PpL1) fused to a polystyrene-binding peptide (PS-tag) that can be recombinantly produced in bacteria. Toward this goal, we developed a rabbit scFv capable to bind the antigen via its variable regions while engaging protein L through its constant framework domain. To enhance the density of captured scFv and enable a better solvent exposure, we generated multiple PpL1 variants bearing polystyrene-binding peptides (PS) tags fused to its ends. The tandem trimer of PpL1 variant bearing PS-tags located at the N-terminus (PpL1'-T-PSN) revealed increased antigen-binding signal when immobilized on hydrophilic polystyrene (phi-PS) plates. By CDR-grafting different antigen-binding specificities into our engineered protein L-binding scFv we validated our technology against a different antigen. Finally, to further enhance the sensitivity of our assay, we implemented a protein L-based pretreatment to remove potential inhibitory immunoglobulin often present in the blood samples. The ability to rapidly and cost-effectively generate animal-free recombinant antibody fragments that can be adsorbed and specifically oriented on plates while retaining their antigen-binding properties could lead to the development of innovative and widely applicable sandwich ELISA systems for the efficient, versatile and sensitive detection of different types of antigens.

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.

The development and application of high throughput cultivation technology in bioprocess development

This review focuses on recent progress in the technology of high throughput (HTP) cultivation and its increasing application in quality by design (QbD) -driven bioprocess development. Several practical HTP strategies aimed at shortening process development (PD) timelines from DNA to large scale processes involving commercially available HTP technology platforms, including microtiter plate (MTP) culture, micro-scale bioreactors, and in parallel fermentation systems, etc., are critically reviewed in detail. This discussion focuses upon the relative strengths and weaknesses or limitations of each of these platforms in this context. Emerging prototypes of micro-bioreactors reported recently, such as milliliter (mL) scale stirred tank bioreactors, and microfludics integrated micro-scale bioreactors, and their potential for practical application in QbD-driven HTP process development are also critically appraised. The overall aim of such technology is to rapidly gain process insights, and since the analytical technology deployed in HTP systems is critically important to the achievement of this aim, this rapidly developing area is discussed. Finally, general future trends are critically reviewed.