Monitoring of scFv selected by phage display using detection of scFv-pIII fusion proteins in a microtiter scale assay

Helicobacter pylori attachment-blocking antibodies protect against duodenal ulcer disease

The majority of the world population carry the gastric pathogen Helicobacter pylori. Fortunately, most individuals experience only low-grade or no symptoms, but in many cases the chronic inflammatory infection develops into severe gastric disease, including duodenal ulcer disease and gastric cancer. Here we report on a protective mechanism where H. pylori attachment and accompanying chronic mucosal inflammation can be reduced by antibodies that are present in a vast majority of H. pylori carriers. These antibodies block binding of the H. pylori attachment protein BabA by mimicking BabA's binding to the ABO blood group glycans in the gastric mucosa. However, many individuals demonstrate low titers of BabA blocking antibodies, which is associated with an increased risk for duodenal ulceration, suggesting a role for these antibodies in preventing gastric disease.

Antibody Affinity and Stability Maturation by Error-Prone PCR

Human antibodies are the most important class of biologicals, and antibodies - human and nonhuman - are indispensable as research agents and for diagnostic assays. When generating antibodies, they sometimes show the desired specificity profile but lack sufficient affinity for the desired application. In this article, a phage display-based method and protocol to increase the affinity of recombinant antibody fragments is given.The given protocol starts with the construction of a mutated antibody gene library by error-prone PCR. Subsequently, the selection of high-affinity variants is performed by panning on immobilized antigen with washing conditions optimized for off-rate-dependent selection. A screening ELISA protocol to identify antibodies with improved affinity and an additional protocol to select antibodies with improved thermal stability is described.

Efficient Construction and Effective Screening of Synthetic Domain Antibody Libraries

Phage display is a powerful technique for drug discovery in biomedical research in particular for antibody libraries. But, several technical challenges are associated with the selection process. For instance, during the panning step, the successful elution of the phages bound to the antigen is critical in order to avoid losing the most promising binders. Here, we present an efficient protocol to establish, screen and select synthetic libraries of domain antibodies using phage display. We do not only present suitable solutions to the above-mentioned challenges to improve elution by 50-fold, but we also present a step by step in-depth protocol with miniaturized volumes and optimized procedures to save material, costs and time for a successful phage display with domain antibodies. Hence, this protocol improves the selection process for an efficient handling process. The here presented library is based on the variable domain (vNAR) of the naturally occurring novel antibody receptor (IgNAR) from cartilage fishes. Diversity was introduced in the Complementarity-Determining Region 3 (CDR3) of the antigen-binding site with different composition and length.

Parallelized Microscale Expression of Soluble scFv

Antibody phage display is a key technology to generate recombinant, mainly human, antibodies for diagnostic and therapy, but also as tools for basic research. After antibody selection by "panning," a crucial step is the screening of monoclonal binders to isolate those which show antigen specificity. For this screening procedure, a highly parallelized approach to produce soluble antibody fragments in microtiter plates is essential. In this chapter, we give the protocol for the parallelized microscale production of scFvs for the screening procedure or further assays.

Antibody Affinity and Stability Maturation by Error-Prone PCR

Antibodies are the fastest growing class of pharmaceutical proteins and essential tools for research and diagnostics. Often antibodies do show a desirable specificity profile but lack sufficient affinity for the desired application. Here, we describe a method to increase the affinity of recombinant antibody fragments based on the construction of mutagenized phage display libraries.After the construction of a mutated antibody gene library by error-prone PCR, selection of high-affinity variants is either performed by panning in solution or on immobilized antigen with washing conditions optimized for off-rate-dependent selection. An additional screening protocol to identify antibodies with improved thermal stability is described.

NanoLuc Luciferase - A Multifunctional Tool for High Throughput Antibody Screening

Based on the recent development of NanoLuc luciferase (Nluc), a small (19 kDa), highly stable, ATP independent, bioluminescent protein, an extremely robust and ultra high sensitivity screening system has been developed whereby primary hits of therapeutic antibodies and antibody fragments could be characterized and quantified without purification. This system is very versatile allowing cellular and solid phase ELISA but also homogeneous BRET based screening assays, relative affinity determinations with competition ELISA and direct Western blotting. The new Nluc protein fusion represents a “swiss army knife solution” for today and future high throughput antibody drug screenings.

Selection of recombinant antibodies from antibody gene libraries

Antibodies are indispensable detection reagents for research and diagnostics and represent the biggest class of biological therapeutics on the market. In vitro antibody selection systems offer many advantages over animal-based technologies because the whole selection process is independent of the in vivo immune response. In the last two decades antibody phage display has evolved to the most robust and widely used method and has already yielded thousands of antibodies. The selection of binders by phage display is also referred to as "panning" and based on the specific molecular interaction of antibody phage with an immobilized antigen thus allowing the enrichment and isolation of antigen-specific monoclonal binders from very large antibody gene libraries. Here, we give detailed protocols for the selection of recombinant antibody fragments from antibody gene libraries in microtiter plates.

Construction of human antibody gene libraries and selection of antibodies by phage display

Antibody phage display is the most commonly used in vitro selection technology and has yielded thousands of useful antibodies for research, diagnostics, and therapy.The prerequisite for successful generation and development of human recombinant antibodies using phage display is the construction of a high-quality antibody gene library. Here, we describe the methods for the construction of human immune and naive scFv gene libraries.The success also depends on the panning strategy for the selection of binders from these libraries. In this article, we describe a panning strategy that is high-throughput compatible and allows parallel selection in microtiter plates.

Construction of human antibody gene libraries and selection of antibodies by phage display

Recombinant antibodies as therapeutics offer new opportunities for the treatment of many tumor diseases. To date, 18 antibody-based drugs are approved for cancer treatment and hundreds of anti-tumor antibodies are under development. The first clinically approved antibodies were of murine origin or human-mouse chimeric. However, since murine antibody domains are immunogenic in human patients and could result in human anti-mouse antibody (HAMA) responses, currently mainly humanized and fully human antibodies are developed for therapeutic applications.Here, in vitro antibody selection technologies directly allow the selection of human antibodies and the corresponding genes from human antibody gene libraries. Antibody phage display is the most common way to generate human antibodies and has already yielded thousands of recombinant antibodies for research, diagnostics and therapy. Here, we describe methods for the construction of human scFv gene libraries and the antibody selection.

Affinity maturation by phage display

Antibodies are indispensable tools for research, diagnostics, and therapy. However, sometimes antibodies with the most favourable specificity profile lack sufficient affinity for a desired application. Here, we describe a method to increase the affinity of recombinant scFv antibody fragments based on random mutagenesis and phage display under stringent conditions. Random mutations are inserted by performing several rounds of error-prone PCR. After construction of a mutated antibody gene library, affinity selection is performed by panning with washing conditions optimized for off-rate-dependent selection. Alternatively, panning in solution with competition can be used to enrich binders with improved binding properties.

Selection of recombinant antibodies from antibody gene libraries

After the sequencing of the human genome is completed, the research focus shifts toward the analysis of gene products. The human genome encodes more than 30,000 genes. Owing to alternative mRNA splicing and posttranslational modifications, for example, glycosylation, phoshorylation, and so on, the number of different proteins of human proteome is supposed to easily exceed 90,000. Antibodies are key detection reagents for the "postgenomic" analysis of these proteins. Any systematic investigation of the human proteome requires high throughput methods for antibody generation. In vitro selection systems utilizing recombinant antibody repertoires offer this capability and capacity. The most commonly used contemporary in vitro selection system is antibody phage display, which has already yielded thousands of useful antibodies for therapy, research, and diagnostics. Herein, methods are described for the selection of recombinant antibody fragments from naive antibody gene libraries.

Perspectives for systematic in vitro antibody generation

After the completion and refinement of the human genome, the characterization of individual gene products in respect of their functions, their modifications, their cellular localization and regulation in both space and time has generated an increased demand for antibodies for their analysis. Taking into account that the human genome contains approximately 25,000 genes, and that their products are found in different splice variants and produce proteins with post-translational modifications, it can be estimated that at least 100,000 different protein products have to be investigated to gain a complete picture of what's going on in the proteome of a cell. Antibodies are preferred tools helping with the characterization and detection of proteins as well as with elucidating their individual functions. The generation of antibodies to all available human protein products by immunization and/or the hybridoma technology is not only logistically and financially enduring, but may prove to be a difficult task, as quite a number of interesting targets may evade the immune response of experimental animals, for example, allosteric variants dependent on fragile interactions to cofactors, highly conserved antigens etc. For this reason, alternative methods for the generation of antibodies have to supplement these approaches. In vitro methods for antibody generation are seen to offer this capability. In addition, they may provide a cost effective and large scale production alternative for detection reagents for the research community in their own right. Among in vitro techniques, phage display has been evolved as the most efficient option for tackling this problem and approaches optimised for automation are emerging. Maximum benefit for proteomic research could be generated by judicious and preferably international coordination of the ongoing efforts to combine the strengths of the well established animal based approaches and the novel opportunities offered by in vitro methods.

Immunogenicity of HIV type 1 gp120 CD4 binding site phage mimotopes

The conserved domain of the CD4 binding site (CD4bs) on the human immunodeficiency virus type 1 (HIV- 1) envelope represents a potential target for vaccine development. Here we describe selection of peptide mimotopes by panning a phage peptide library on the HIV-1 CD4bs-specific, broadly neutralizing anti-HIV-1 monoclonal antibody, IgG(1) b12. We identified an initial consensus sequence for IgG1 b12 binding (M/VThetaSD, where Theta represents an aromatic amino acid). A molecular evolution approach, using second- and third-generation libraries, led us to identify a refined consensus sequence (GLLVWSDEL). The resulting IgG1 b12 phage mimotopes compete with gp160 for the IgG1 b12 antigen-binding site, but the phage coat protein (pIII) may play an important structural role, since both free peptides and KLH-conjugated peptides have no detectable binding activity. Mice immunized with IgG1 b12 phage mimotopes elicited a weak but persistent humoral response directed against the HIV-1 envelope. An antibody fragment was isolated from the antibody repertoires of these animals. It is noteworthy that while it has a relatively low affinity for HIV-1 gp160, the antibody targets an epitope that overlaps with that of IgG1 b12. Our data therefore suggest that engineered IgG1 b12 mimotopes share immunogenic features with the CD4bs. However, these peptidic structures will require further improvement in order to generate broad specificity neutralizing antibodies like IgG1 b12.

Human antibody derivatives against the fibroblast activation protein for tumor stroma targeting of carcinomas

The fibroblast activation protein (FAP) is selectively expressed on activated fibroblasts of the tumor stroma on more than 90% of lung, breast and colon carcinomas. The high prevalence and abundance of FAP(+) stroma make it a promising target for in vivo diagnosis and therapy of a variety of carcinomas. We describe the humanization of the murine FAP-specific MAb, F19, which has already been clinically used for in vivo diagnostic purposes. Using phage display technology and human V-repertoires, VL and VH regions of F19 were replaced by analogous human V-regions while retaining the original HCDR3 sequence in order to maintain F19 epitope specificity. The resulting human single-chain fragments of immunoglobulin variable regions (scFv 34, scFv 18) showed affinities of 6 nM on cell membrane-bound FAP. scFv 34 was expressed as a bivalent minibody (Mb 34). The antigen-binding characteristics of Mb 34 were comparable to the parental and a complementarity-determining region (CDR)-grafted version of F19. This was revealed by binding competition studies, FACS analyses and immunohistochemistry on various tumor samples including breast, colon and lung carcinomas. Importantly, compared with the CDR-grafted humanized scFv version of F19, the V-regions of the selected human scFv 34 showed sequence identity with the parental antibody (Ab) only over the short, 15-amino acid long HCDR3. Thus, a largely reduced xenoantigenic potential is expected. These human Ab derivatives are suitable to develop novel therapeutic concepts with broad applicability for a wide variety of histological carcinomas based on tumor stroma targeting.

Survey of the 1998 optical biosensor literature

The utilization of optical biosensors to study molecular interactions continues to expand. In 1998, 384 articles relating to the use of commercial biosensors were published in 130 different journals. While significant strides in new applications and methodology were made, a majority of the biosensor literature is of rather poor quality. Basic information about experimental conditions is often not presented and many publications fail to display the experimental data, bringing into question the credibility of the results. This review provides suggestions on how to collect, analyze and report biosensor data.

Procaryotic expression of single-chain variable-fragment (scFv) antibodies: secretion in L-form cells of Proteus mirabilis leads to active product and overcomes the limitations of periplasmic expression in Escherichia coli

Recently it has been demonstrated that L-form cells of Proteus mirabilis (L VI), which lack a periplasmic compartment, can be efficiently used in the production and secretion of heterologous proteins. In search of novel expression systems for recombinant antibodies, we compared levels of single-chain variable-fragment (scFv) production in Escherichia coli JM109 and P. mirabilis L VI, which express four distinct scFvs of potential clinical interest that show differences in levels of expression and in their tendencies to form aggregates upon periplasmic expression. Production of all analyzed scFvs in E. coli was limited by the severe toxic effect of the heterologous product as indicated by inhibition of culture growth and the formation of insoluble aggregates in the periplasmic space, limiting the yield of active product. In contrast, the L-form cells exhibited nearly unlimited growth under the tested production conditions for all scFvs examined. Moreover, expression experiments with P. mirabilis L VI led to scFv concentrations in the range of 40 to 200 mg per liter of culture medium (corresponding to volume yields 33- to 160-fold higher than those with E. coli JM109), depending on the expressed antibody. In a translocation inhibition experiment the secretion of the scFv constructs was shown to be an active transport coupled to the signal cleavage. We suppose that this direct release of the newly synthesized product into a large volume of the growth medium favors folding into the native active structure. The limited aggregation of scFv observed in the P. mirabilis L VI supernatant (occurring in a first-order-kinetics manner) was found to be due to intrinsic features of the scFv and not related to the expression process of the host cells. The P. mirabilis L VI supernatant was found to be advantageous for scFv purification. A two-step chromatography procedure led to homogeneous scFv with high antigen binding activity as revealed from binding experiments with eukaryotic cells.