Ribosome display of antibodies: expression, specificity and recovery in a eukaryotic system

Transcriptome and network analysis pinpoint ABA and plastid ribosomal proteins as main contributors to salinity tolerance in the rice variety, CSR28

Salinity stress is a major challenge for rice production, especially at seedling stage. To gain comprehensive insight into the molecular mechanisms and potential candidate genes involved in rice salinity stress response, we integrated physiological, transcriptome and network analysis to investigate salinity tolerance in two contrasting rice genotypes. The root and shoot samples were collected at two timepoints (6 hours and 54 hours) of high salt treatment. Element assay showed that the tolerant genotype CSR28 had lower Na+/K+ ratio in both organs than in those of the sensitive genotype IR28 under salinity stress. A total of 15,483 differentially expressed genes (DEGs) were identified from the RNA-Seq analysis. The salt-specific genes were mainly involved in metabolic processes, response to stimulus, and transporter activity, and were enriched in key metabolic pathways such as, biosynthesis of secondary metabolites, plant hormone signal transduction, and carotenoid biosynthesis. Furthermore, the results showed that the differential genes involved in abscisic acid (ABA) biosynthesis were specifically up-regulated in the tolerant genotype. Network analysis revealed 50 hub genes for the salt-specific genes in the roots of CSR28 which mainly encodes ribosomal proteins (RPs). Functional validation of the nine hub genes revealed three plastid RPs (PRPs), including OsPRPL17, OsPRPS9 and OsPRPL11, which contributes to protein synthesis, chloroplast development and stress signaling. Our findings suggested that ABA and PRPs play key roles to enhance of salinity tolerance in CSR28. Our study provides valuable information for further investigations of the candidate genes associated with salt tolerance and the development of salt-tolerant rice varieties.

Selection of an artificial paraquat-specific binding protein from a ribosome display library based on a lipocalin scaffold

In this study, an anticalin that could specifically bind paraquat (PQ), a quaternary nitrogen herbicide, as a new set of engineered receptor protein with antibody-like properties was generated to detect PQ concentration. To this end, a native and random library was constructed and engineered to allow in vitro transcription and translation using an Escherichia coli lysate system. Meanwhile, a PQ derivative that carries an active aliphatic carboxylate group at the end of an aliphatic spacer arm was synthesized. Then, this compound was coupled covalently to the carrier protein bovine serum albumin/ovalbumin and amino-functionalized paramagnetic beads. Alternating selection in solution and immobilization in microtiter wells were used to pan mRNA-ribosome-antibody complexes. After several rounds of ribosome display, three variants were selected from a random library of the bilin-binding protein. The variants that could bind complex PQ with high affinity and exhibit IC₅₀ values as low as 14.039 ± 0.970 ng/mL were identified. Moreover, the limits of detection reached 0.083 ± 0.011 ng/mL. Our data suggest that the generation of anticalins may provide a promising alternative to recombinant antibody fragments to create a stable receptor protein against hapten with bioanalytical relevance.

Ribosome Display Technology: Applications in Disease Diagnosis and Control

Antibody ribosome display remains one of the most successful in vitro selection technologies for antibodies fifteen years after it was developed. The unique possibility of direct generation of whole proteins, particularly single-chain antibody fragments (scFvs), has facilitated the establishment of this technology as one of the foremost antibody production methods. Ribosome display has become a vital tool for efficient and low-cost production of antibodies for diagnostics due to its advantageous ability to screen large libraries and generate binders of high affinity. The remarkable flexibility of this method enables its applicability to various platforms. This review focuses on the applications of ribosome display technology in biomedical and agricultural fields in the generation of recombinant scFvs for disease diagnostics and control.

Identification and characterization of a novel single-chain variable fragment (scFv) antibody against Neisseria meningitidis factor H-binding protein (fHbp)

Purpose. Neisseria meningitidis is the leading global cause of meningitis and sepsis. Detection, followed by identification, of bacterial pathogens is important in medicine and public health. In the present study, we used the ribosome display technique to select single-chain variable fragments (scFv) that are specific to the surface-exposed fHbp antigen of N. meningitidis. Methodology. The recombinant fHbp protein was used as the antigen for the immunization of BALB/c mice. Anti-fHbp VH/k chain ribosome display libraries were assembled by joining VH and k into the VH/k chain with a specially constructed linker by PCR overlap extension. The scFv library was panned against the recombinant fHbp protein by using a single round of the ribosome display method via a rabbit reticulocyte lysate system.Results/Key findings. The selected anti-fHbp antibody exhibited high affinity and specificity in the enzyme-linked immunosorbent assay (ELISA) and the whole bacterial cell enzyme-linked immunosorbent assay (Bact-ELISA).Conclusion. The affinity of the selected scFv was ~8.65×10⁹ M^-1. The isolated scFv can provide the basis for developing a diagnostic kit.

Bioinformatics evaluation of novel ribosome display-selected single chain variable fragment (scFv) structure with factor H binding protein through docking

Antibodies play a significant role in the immunotherapy, basic research and the pharmaceutical industry. Nowadays, both DNA recombinant technology and antibody engineering technology are widely used in many fields such as diagnostics, therapeutics, drug targeted delivery, and research reagents. Computational docking of antigen-antibody complexes and analysis of atomic interactions are important to find effective B-cell epitopes and new antibodies with appropriate properties. In the present study, by using ClusPro 2.0 webserver, docking the antigen (factor H binding protein (fHbp)) to the novel-selected scFv antibody was performed. By analyzing the fHbp-scFv complexes, important amino acids were identified. After docking, peptides Ala192-His198, Asp 211-216, and Gly229-Ser228 of the fHbp antigen were recognized as essential interactive regions to the scFv antibody. Results obtained from our bioinformatics study are important and give us the basis for the favored designs of new molecules such as effective B-cell epitopes targeted by neutralizing antibodies for vaccine design.

Screening scFv antibodies against infectious bursal disease virus by co-expression of antigen and antibody in the bacteria display system

We have previously reported an antigen and antibody co-expression (AAC) technology to demonstrate the interaction between a known antigen and antibody. To validate the co-expression system for screening antibody libraries, a single chain fragment variable(scFv)antibody library was constructed from chickens immunized with the VP2 protein of infectious bursal disease virus (IBDV). The genes of both VP2 and scFv antibodies were inserted into the pBFD-Ab-Ag vector. The co-expression library was subjected to three rounds of screening by flow cytometry (FCM) using a polyclonal antibody against VP2 through a bacteria display system. We achieved enrichment of scFv specific for IBDV. 110 individual clones were initially selected and sequenced. Twenty clones were selected based on fluorescence intensity by FCM. The scFv antibodies were expressed by pET-27b in E.coli and purified. The specificity and affinity of the selected scFv antibodies were confirmed by western blotting assay and ELISA analysis. What's more, the neutralizing capacity was measured with IBDV-B87(100 TCID₅₀) in vitro. Four scFvs (clone 8(1), Y8, L10 and L7) showed significant neutralizing capacity. Two of the four scFvs (clone 8(1) and Y8) demonstrated a higher neutralizing activity to IBDV-B87 and the titers were 16,384 and 8,192, respectively. The two scFvs had higher neutralizing capacity than those obtained in previous studies. We demonstrated that the AAC technology could be applied to screen antibody libraries without baiting antigen to make antibody screening process easier and obtain scFvs with higher neutralizing capacity.

Selection of Recombinant Human Antibodies

Since the development of therapeutic antibodies the demand of recombinant human antibodies is steadily increasing. Traditionally, therapeutic antibodies were generated by immunization of rat or mice, the generation of hybridoma clones, cloning of the antibody genes and subsequent humanization and engineering of the lead candidates. In the last few years, techniques were developed that use transgenic animals with a human antibody gene repertoire. Here, modern recombinant DNA technologies can be combined with well established immunization and hybridoma technologies to generate already affinity maturated human antibodies. An alternative are in vitro technologies which enabled the generation of fully human antibodies from antibody gene libraries that even exceed the human antibody repertoire. Specific antibodies can be isolated from these libraries in a very short time and therefore reduce the development time of an antibody drug at a very early stage.In this review, we describe different technologies that are currently used for the in vitro and in vivo generation of human antibodies.

Characterization of Anti-Citrinin Specific ScFvs Selected from Non-Immunized Mouse Splenocytes by Eukaryotic Ribosome Display

Single chain variable fragments (scFvs) against citrinin (CIT) were selected from a scFv library constructed from the splenocytes of non-immunized mice by an improved eukaryotic ribosome display technology in this study. Bovine serum albumin (BSA)/ CIT-BSA and ovalbumin (OVA)/ CIT-OVA were used as the antigens to select specific anti-CIT scFvs. Eukaryotic in situ RT-PCR method was used to recover the selected mRNA after every affinity selection. After six rounds of ribosome display, expression vector pTIG-TRX carrying specific scFv DNAs were constructed and transformed into Escherichia coli BL21 (DE3) for protein expression. Thirteen positive clones were selected out of which three (designated 23, 68 and 109) showed high binding activity and specificity to CIT by indirect ELISA, while no clone showed binding activity with carrier proteins. The three scFvs showed high specificity to CIT and the cross reactivity with other mycotoxins was below 0.01% as determined by indirect competitive ELISA. These specific scFvs offer a potential novel immunoassay method for CIT residues. This study confirmed the effectiveness of the improved eukaryotic ribosome display system and could be used as a reference for the selection of scFvs specific to other small molecules using ribosome display.

Eukaryotic ribosome display with in situ DNA recovery

Ribosome display is a cell-free display technology for in vitro selection and optimisation of proteins from large diversified libraries. It operates through the formation of stable protein-ribosome-mRNA (PRM) complexes and selection of ligand-binding proteins, followed by DNA recovery from the selected genetic information. Both prokaryotic and eukaryotic ribosome display systems have been developed. In this chapter, we describe the eukaryotic rabbit reticulocyte method in which a distinct in situ single-primer RT-PCR procedure is used to recover DNA from the selected PRM complexes without the need for prior disruption of the ribosome.

Evolution of antibodies in vitro by ribosome display

Ribosome display is a cell-free technology which enables in vitro selection and evolution of antibodies from very large diversified DNA libraries. It operates through the following key steps: (1) generation of PCR library; (2) formation of stable antibody-ribosome-mRNA (ARM) complexes as the selection particles, (3) selection of ligand-binding ARM complexes on an immobilized ligand and (4) recovery of the selected genetic information as DNA by RT-PCR. Since PCR-based random or/and site-directed mutagenesis can be easily used to introduce mutations into the selected DNA pool in each cycle, ribosome display offers an efficient "protein evolution" tool for antibody optimization. Both prokaryotic and eukaryotic cell-free systems have been explored for ribosome display of different proteins. In this chapter, we describe the use of the eukaryotic rabbit reticulocyte ribosome display method to isolate variants of V(H) antibody fragments with improved affinities.

Eukaryotic ribosome display selection using rabbit reticulocyte lysate

Ribosome display is a powerful in vitro technology for the selection and directed evolution of proteins. Cell-free translation is central to the ribosome display process and is performed in such a way that the ribosome provides the link between genotype and phenotype that allows genes encoding proteins with desired properties to be identified by selection. Prokaryotic cell-free translation reagents, based initially on E. coli cell extracts and more recently containing purified and recombinant factors, have dominated the ribosome display literature. Eukaryotic cell extracts are also suitable for ribosome display; however, protocols for prokaryotic ribosome display are not directly transferable to the use of eukaryotic cell extracts. This chapter describes an optimised methodology for the use of rabbit reticulocyte lysate for ribosome display selections.

Selection of scFvs specific for the HepG2 cell line using ribosome display

The aim of this study was to construct a ribosome display library of single chain variable fragments (scFvs) associated with hepatocarcinoma and screen such a library for hepatocarcinoma-binding scFvs. mRNA was isolated from the spleens of mice immunized with hepatocellular carcinoma cell line HepG2. Heavy and k chain genes (VH and k) were amplified separately by RT-PCR, and an anti-HepG2 VH/k chain ribosome display library was constructed by assembling VH and k into the VH/k chain with a specially constructed linker by SOE-PCR. The VH/k chain library was transcribed and translated in vitro using a rabbit reticulocyte lysate system. In order to isolate specific scFvs, recognizing HepG2 negative selection on a normal hepatocyte line WRL-68 was carried out before three rounds of positive selection on HepG2. After three rounds of panning, cell enzyme-linked immunosorbent assay (ELISA) showed that one of the scFvs had high affinity for the HepG2 cell and lower affinity for the WRL-68 cell. In this study, we successfully constructed a native ribosome display library. Such a library would prove useful for direct intact cell panning using ribosome display technology. The selected scFv had a potential value for hepatocarcinoma treatment.

Selection of anti-sulfadimidine specific ScFvs from a hybridoma cell by eukaryotic ribosome display

BACKGROUND

Ribosome display technology has provided an alternative platform technology for the development of novel low-cost antibody based on evaluating antibiotics derived residues in food matrixes.

METHODOLOGY/PRINCIPAL FINDINGS

In our current studies, the single chain variable fragments (scFvs) were selected from hybridoma cell lines against sulfadimidine (SM(2)) by using a ribosome library technology. A DNA library of scFv antibody fragments was constructed for ribosome display, and then mRNA-ribosome-antibody (MRA) complexes were produced by a rabbit reticulocyte lysate system. The synthetic sulfadimidine-ovalbumin (SM(2)-OVA) was used as an antigen to pan MRA complexes and putative scFv-encoding genes were recovered by RT-PCR in situ following each panning. After four rounds of ribosome display, the expression vector pCANTAB5E containing the selected specific scFv DNA was constructed and transformed into Escherichia coli HB2151. Three positive clones (SAS14, SAS68 and SAS71) were screened from 100 clones and had higher antibody activity and specificity to SM(2) by indirect ELISA. The three specific soluble scFvs were identified to be the same molecular weight (approximately 30 kDa) by Western-blotting analysis using anti-E tag antibodies, but they had different amino acids sequence by sequence analysis.

CONCLUSIONS/SIGNIFICANCE

The selection of anti-SM(2) specific scFv by in vitro ribosome display technology will have an important significance for the development of novel immunodetection strategies for residual veterinary drugs.

Applications of single-chain variable fragment antibodies in therapeutics and diagnostics

Antibodies (Abs) are some of the most powerful tools in therapy and diagnostics and are currently one of the fastest growing classes of therapeutic molecules. Recombinant antibody (rAb) fragments are becoming popular therapeutic alternatives to full length monoclonal Abs since they are smaller, possess different properties that are advantageous in certain medical applications, can be produced more economically and are easily amendable to genetic manipulation. Single-chain variable fragment (scFv) Abs are one of the most popular rAb format as they have been engineered into larger, multivalent, bi-specific and conjugated forms for many clinical applications. This review will show the tremendous versatility and importance of scFv fragments as they provide the basic antigen binding unit for a multitude of engineered Abs for use as human therapeutics and diagnostics.

Selection of recombinant antibodies by eukaryotic ribosome display

Ribosome display is a powerful method for selection of single-chain antibodies in vitro. It operates through the formation of libraries of antibody-ribosome-mRNA complexes that are selected on immobilized antigen, followed by recovery of the genetic information from the mRNA by RT-PCR. Both prokaryotic and eukaryotic versions are used. We describe our eukaryotic system, in which rabbit reticulocyte extracts are used for cell free transcription/translation and cDNA is recovered by in situ RT-PCR performed on the selected complexes.

Ribosome display and selection of human anti-CD22 scFvs derived from an acute lymphocytic leukemia patient

Novelin vitromethods for the display of antibody libraries against disease-related antigens have led to the development of powerful protein-based biotherapeutics. Eukaryotic ternary ribosome complexes can be used to display human single chain antibodies (scFvs) to isolate specific binding reagents to these antigens. Here, we present the isolation of human scFv against the immunotherapeutic target antigen CD22 from a patient-derived human scFv library using ribosome display technology. The ribosome complexes were enriched against the extra-cellular domain of human CD22 conjugated to magnetic beads. Isolated constructs were further affinity-matured and specific binding activity was demonstrated by surface plasmon resonance and validated usingin vitrocell assays. The isolated human anti-CD22 scFvs can provide a basis for the development of new immunotherapeutic strategies in CD22-expressing malignant diseases.

Rapid discovery of protein interactions by cell-free protein technologies

Cell-free transcription and translation provides an open, controllable environment for production of correctly folded, soluble proteins and allows the rapid generation of proteins from DNA without the need for cloning. Thus it is becoming an increasingly attractive alternative to conventional in vivo expression systems, especially when parallel expression of multiple proteins is required. Through novel design and exploitation, powerful cell-free technologies of ribosome display and protein in situ arrays have been developed for in vitro production and isolation of protein-binding molecules from large libraries. These technologies can be combined for rapid detection of protein interactions.

Affinity reagent resources for human proteome detection: initiatives and perspectives

Essential to the ambition of characterising fully the human proteome are systematic and comprehensive collections of specific affinity reagents directed against all human proteins, including splice variants and modifications. Although a large number of affinity reagents are available commercially, their quality is often questionable and only a fraction of the proteome is covered. In order for more targets to be examined, there is a need for broad availability of panels of affinity reagents, including binders against proteins of unknown functions. The most familiar affinity reagents are antibodies and their fragments, but engineered forms of protein scaffolds and nucleic acid aptamers with similar diversity and binding properties are becoming viable alternatives. Recent initiatives in Europe and the USA have been established to improve both the availability and quality of reagents for affinity proteomics, with the ultimate aim of creating standardised collections of well-validated binding molecules for proteome analysis. As well as coordinating affinity reagent production through existing resources and technology providers, these projects aim to benchmark key molecular entities, tools, and applications, and establish the bioinformatics framework and databases needed. The benefits of such reagent resources will be seen in basic research, medicine and the biotechnology and pharmaceutical industries.

A pseudoknot improves selection efficiency in ribosome display

The size and diversity of ribosome display libraries depends upon stability of the complex formed between the ribosome, mRNA and translated protein. To investigate if mRNA secondary structure improves stability of the complex, we tested a pseudoknot, originating from the genomic RNA of infectious bronchitis virus (IBV), a member of the positive-stranded coronavirus group. We used the previously-isolated anti-DNA scFv, 3D8, as a target protein. During in vitro translation in rabbit reticulocyte lysate, we observed that incorporation of the pseudoknot into the mRNA resulted in production of a translational intermediate that corresponded to the expected size for ribosomal arrest at the pseudoknot. Complexes containing the mRNA pseudoknot exhibited a higher efficiency of affinity selection than that those without, indicating that the pseudoknot improves stability of the mRNA-ribosome-antibody complex in a eukaryotic translation system. Thus, in order to improve the efficiency of selection, this relatively short pseudoknot sequence could be incorporated into ribosome display.

Selection of antigenic markers on a GFP-Cκ fusion scaffold with high sensitivity by eukaryotic ribosome display

Ribosome display is a cell-free system permitting gene selection through the physical association of genetic material (mRNA) and its phenotypic (protein) product. While often used to select single-chain antibodies from large libraries by panning against immobilized antigens, we have adapted ribosome display for use in the 'reverse' format in order to select high affinity antigenic determinants against solid-phase antibody. To create an antigenic scaffold, DNA encoding green fluorescent protein (GFP) was fused to a light chain constant domain (Ckappa) with stop codon deleted, and with 5' signals (T7 promoter, Kozak) enabling coupled transcription/translation in a eukaryotic cell-free system. Epitopes on either GFP (5') or Ckappa (3') were selected by anti-GFP or anti-Ckappa antibodies, respectively, coupled to magnetic beads. After selection, mRNA was amplified directly from protein-ribosome-mRNA (PRM) complexes by in situ PCR followed by internal amplification and reassembly PCR. As little as 10fg of the 1kb DNA construct, i.e. approximately 7500 molecules, could be recovered following a single round of interaction with solid-phase anti-GFP antibody. This platform is highly specific and sensitive for the antigen-antibody interaction and may permit selection and reshaping of high affinity antigenic variants of scaffold proteins.

Design of synthetic antibody libraries

Antibody libraries came into existence 15 years ago when the accumulating sequence data of immunoglobulin genes and the advent of polymerase chain reaction technology made it possible to clone antibody gene repertoires. Since then, virtually hundreds of antibody libraries have been constructed, employing limitless maneuvers from the antibody engineering molecular bag of tricks towards the crucial parameters that determine library quality, library size, diversity and robustness. Phage and additional display and screening technologies were applied to pan out desired binding specificities from antibody libraries. Several biotech companies established themselves as key operators in the multibillion-dollar field of recombinant antibody technology. Out of nineteen FDA-approved therapeutic antibodies, one was isolated from an antibody library and many more are in various stages of clinical evaluation. This review highlights key milestones in the short history of antibody libraries and attempts to predict the future impact of antibody libraries on drug discovery.

Eukaryotic ribosome display with in situ DNA recovery

Ribosome display is a cell-free technology for the in vitro selection and evolution of proteins encoded by DNA libraries, in which individual nascent proteins (phenotypes) are linked physically to their corresponding mRNA (genotypes) in stable protein-ribosome-mRNA (PRM) complexes. Formation of the complexes can be achieved through deletion of the stop codon of the mRNA, stalling the ribosome at the end of translation; the nascent protein is extended by a spacer such as the immunoglobulin Ckappa domain or others to allow exit through the ribosome tunnel. Through affinity for a ligand, the protein-mRNA coupling permits simultaneous isolation of a functional nascent protein and its translated mRNA; the latter is then converted into cDNA by reverse transcription and amplified for further manipulation, repeated cycles or soluble protein expression. Through the use of PCR-generated libraries, avoiding the need for cloning, ribosome display can be used to both screen very large populations and continuously search for new diversity during subsequent rounds of selection. Additionally, the use of cell-free systems allows the selection of proteins that are toxic or unstable in cells, and proteins with chemical modifications. Ribosome display systems using both prokaryotic and eukaryotic cell extracts have been developed. Examples of the application of eukaryotic systems include the selection and evolution of antibody fragments, DNA binding domains, enzymes, interacting proteins and peptides among others. Here we describe the step-by-step procedure to perform our previously described eukaryotic ribosome display method, which has the distinctive feature of an in situ reverse transcription-PCR (RT-PCR) procedure for DNA recovery from ribosome-bound mRNA. We also introduce a recent, previously unpublished improvement to the procedure in which in situ reverse transcription is combined with sensitive single-primer PCR technology.

In vitro display technologies reveal novel biopharmaceutics

Display technologies are fundamental to the isolation of specific high-affinity binding proteins for diagnostic and therapeutic applications in cancer, neurodegenerative, and infectious diseases as well as autoimmune and inflammatory disorders. Applications extend into the broad field of antibody (Ab) engineering, synthetic enzymes, proteomics, and cell-free protein synthesis. Recently, in vitro display technologies have come to prominence due to the isolation of high-affinity human antibodies by phage display, the development of novel scaffolds for ribosome display, and the discovery of novel protein-protein interactions. In vitro display represents an emerging and innovative technology for the rapid isolation and evolution of high-affinity peptides and proteins. So far, only one clinical drug candidate produced by in vitro display technology has been approved by the FDA for use in humans, but several are in clinical or preclinical testing. This review highlights recent advances in various engineered biopharmaceutical products isolated by in vitro display with a focus on the commercial developments.

Ribosome display: next-generation display technologies for production of antibodies in vitro

Antibodies represent an important and growing class of biologic research reagents and biopharmaceutical products. They can be used as therapeutics in a variety of diseases. With the rapid expansion of proteomic studies and biomarker discovery, there is a need for the generation of highly specific binding reagents to study the vast number of proteins encoded by the genome. Display technologies provide powerful tools for obtaining antibodies. Aside from the preservation of natural antibody repertoires, they are capable of exploiting diversity by DNA recombination to create very large libraries for selection of novel molecules. In contrast to in vivo immunization processes, display technologies allow selection of antibodies under in vitro-defined selection condition(s), resulting in enrichment of antibodies with desired properties from large populations. In addition, in vitro selection enables the isolation of antibodies against difficult antigens including self-antigens, and this can be applied to the generation of human antibodies against human targets. Display technologies can also be combined with DNA mutagenesis for antibody evolution in vitro. Some methods are amenable to automation, permitting high-throughput generation of antibodies. Ribosome display is considered as representative of the next generation of display technologies since it overcomes the limitations of cell-based display methods by using a cell-free system, offering advantages of screening larger libraries and continuously expanding new diversity during selection. Production of display-derived antibodies can be achieved by choosing one of a variety of prokaryotic and eukaryotic cell-based expression systems. In the near future, cell-free protein synthesis may be developed as an alternative for large-scale generation of antibodies.

Ribosome display for improved biotherapeutic molecules

Ribosome display presents an innovative in vitro technology for the rapid isolation and evolution of high-affinity peptides or proteins. Displayed proteins are bound to and recovered from target molecules in multiple rounds of selection in order to enrich for specific binding proteins. No transformation step is necessary, which could lead to a loss of library diversity. A cycle of display and selection can be performed in one day, enabling the existing gene repertoire to be rapidly scanned. Proteins isolated from the panning rounds can be further modified through random or directed molecular evolution for affinity maturation, as well as selected for characteristics such as protein stability, folding and functional activity. Recently, the field of display technologies has become more prominent due to the generation of new scaffolds for ribosome display, isolation of high-affinity human antibodies by phage display, and their implementation in the discovery of novel protein-protein interactions. Applications for this technology extend into the broad field of antibody engineering, proteomics, and synthetic enzymes for diagnostics and therapeutics in cancer, autoimmune and infectious diseases, neurodegenerative diseases and inflammatory disorders. This review highlights the role of ribosome display in drug discovery, discusses advantages and disadvantages of the system, and attempts to predict the future impact of ribosome display technology on the development of novel engineered biopharmaceutical products for biological therapies.

An improved method for an efficient and easily accessible eukaryotic ribosome display technology

Ribosome display is a powerful in vitro technology for the selection and directed evolution of proteins. However, this technology has so far been perceived as being technically challenging owing to comparatively difficult protocols and the absence of tailored commercial reagents, particularly when using prokaryotic cell-free expression systems. Eukaryotic ribosome display is potentially a more accessible alternative because of the availability of suitable commercial reagents, yet despite published protocols, this method has been less widely used. For eukaryotic ribosome display, a novel mechanism of mRNA recovery compared with that of the well-proven prokaryotic method has been proposed. We have examined the eukaryotic ribosome display process with the aims of investigating the proposed mechanism of sequence recovery and of identifying aspects of the protocol that may have lead to poor performance and therefore so far limited its use. We demonstrate that the proposed novel method is in fact mechanistically comparable to the prokaryotic method and we provide a step-by-step protocol for eukaryotic ribosome display that is 20-fold more efficient than current published methods. Our findings should increase the ease of operating ribosome display technology, making it more accessible to the scientific community.