Construction of Antibody Phage Libraries and Their Application in Veterinary Immunovirology

A review on camelid nanobodies with potential application in veterinary medicine

The single variable domains of camelid heavy-chain only antibodies, known as nanobodies, have taken a long journey since their discovery in 1989 until the first nanobody-based drug's entrance to the market in 2022. On account of their unique properties, nanobodies have been successfully used for diagnosis and therapy against various diseases or conditions. Although research on the application of recombinant antibodies has focused on human medicine, the development of nanobodies has paved the way for incorporating recombinant antibody production in favour of veterinary medicine. Currently, despite many efforts in developing these biomolecules with diversified applications, significant opportunities exist for exploiting these highly versatile and cost-effective antibodies in veterinary medicine. The present study attempts to identify existing gaps and shed light on paths for future research by presenting an updated review on camelid nanobodies with potential applications in veterinary medicine.

A dual-targeting approach using a human bispecific antibody against the receptor-binding domain of the Middle East Respiratory Syndrome Coronavirus

The emergence of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) has posed a significant global health concern due to its severe respiratory illness and high fatality rate. Currently, despite the potential for resurgence, there are no specific treatments for MERS-CoV, and only supportive care is available. Our study aimed to address this therapeutic gap by developing a potent neutralizing bispecific antibody (bsAb) against MERS-CoV. Initially, we isolated four human monoclonal antibodies (mAbs) that specifically target the MERS-CoV receptor-binding domain (RBD) using phage display technology and an established human antibody library. Among these four selected mAbs, our intensive in vitro functional analyses showed that the MERS-CoV RBD-specific mAb K111.3 exhibited the most potent neutralizing activity against MERS-CoV pseudoviral infection and the molecular interaction between MERS-CoV RBD and human dipeptidyl peptidase 4. Consequently, we engineered a novel bsAb, K207.C, by utilizing K111.3 as the IgG base and fusing it with the single-chain variable fragment of its non-competing pair, K111.1. This engineered bsAb showed significantly enhanced neutralization potential against MERS-CoV compared to its parental mAb. These findings suggest that K207.C may serve as a potential candidate for effective MERS-CoV neutralization, further highlighting the promise of the bsAb dual-targeting approach in MERS-CoV neutralization.

Combining CRISPR-Cas-mediated terminal resolution with a novel genetic workflow to achieve high-diversity adenoviral libraries

While recombinant adenoviruses (rAds) are widely used in both laboratory and medical gene transfer, library-based applications using this vector platform are not readily available. Recently, we developed a new method, the CRISPR-Cas9 mediated in vivo terminal resolution aiding high-efficiency rescue of rAds from recombinant DNA. Here we report on a genetic workflow that allows construction of bacterial artificial chromosome-based rAd libraries reconstituted using highly efficient terminal resolution. We utilized frequent, pre-existing genomic sequences to allow the insertion of a selection marker, complementing two selected target sites into novel endonuclease recognition sites. In the second step, this selection marker is replaced with a transgene or mutation of interest via Gibson assembly. Our approach does not cause unwanted genomic off-target mutations while providing substantial flexibility for the site and nature of the genetic modification. This new genetic workflow, which we termed half site-directed fragment replacement (HFR) allows the introduction of more than 106 unique modifications into rAd encoding BACs using laboratory scale methodology. To demonstrate the power of HFR, we rescued barcoded viral vector libraries yielding a diversity of approximately 2.5 × 104 unique rAds per cm2 of transfected cell culture.

Development, High-Throughput Profiling, and Biopanning of a Large Phage Display Single-Domain Antibody Library

Immunoglobulin G-based monoclonal antibodies (mAbs) have been effective in treating various diseases, but their large molecular size can limit their penetration of tissue and efficacy in multifactorial diseases, necessitating the exploration of alternative forms. In this study, we constructed a phage display library comprising single-domain antibodies (sdAbs; or "VHHs"), known for their small size and remarkable stability, using a total of 1.6 × 109 lymphocytes collected from 20 different alpacas, resulting in approximately 7.16 × 1010 colonies. To assess the quality of the constructed library, next-generation sequencing-based high-throughput profiling was performed, analyzing approximately 5.65 × 106 full-length VHH sequences, revealing 92% uniqueness and confirming the library's diverse composition. Systematic characterization of the library revealed multiple sdAbs with high affinity for three therapeutically relevant antigens. In conclusion, our alpaca sdAb phage display library provides a versatile resource for diagnostics and therapeutics. Furthermore, the library's vast natural VHH antibody repertoire offers insights for generating humanized synthetic sdAb libraries, further advancing sdAb-based therapeutics.

Canine distemper virus (CDV)-neutralizing activities of an anti-CDV canine-derived single-chain variable antibody fragment 4-15 (scFv 4-15) screened by phage display technology

Canine distemper virus (CDV) is a highly contagious pathogen that causes severe diarrhea, fever and vomiting in domestic dogs, posing a serious threat to the dog breeding industry. Currently, there are no effective therapeutic agents for emergency treatment despite the availability of vaccines against CDV infection. Single-chain fragment variable (scFv) antibody has been demonstrated to effectively inhibit virus infections, suggesting a potential candidate as a therapeutic agent for canine distemper. In this study, a phage-displayed scFv library was constructed from the peripheral blood lymphocytes of dog immunized intramuscularly with live-attenuated CDV vaccine, and was subjected to four rounds of pannings against CDV. Subsequent indirect enzyme-linked immunosorbent assay screening revealed high-affinity scFv antibodies specific to CDV, and indirect immunofluorescence assay screening revealed CDV-neutralizing activity of scFv antibodies. Our results showed that a scFv antibody 4-15 (scFv 4-15) with high-affinity binding to CDV and neutralizing activity against CDV was obtained, which displayed effective therapeutic potential in vivo for dogs challenged with a lethal dose of CDV. Conclusively, the scFv 4-15 with high-affinity binding and neutralizing activity to CDV that was obtained by phage display technology provides a promising candidate for the therapeutic agents against CDV infection.

Eukaryotic ribosome display for antibody discovery: A review

Monoclonal antibody biologics have significantly transformed the therapeutic landscape within the biopharmaceutical industry, partly due to the utilisation of discovery technologies such as the hybridoma method and phage display. While these established platforms have streamlined the development process to date, their reliance on cell transformation for antibody identification faces limitations related to library diversification and the constraints of host cell physiology. Cell-free systems like ribosome display offer a complementary approach, enabling antibody selection in a completely in vitro setting while harnessing enriched cellular molecular machinery. This review aims to provide an overview of the fundamental principles underlying the ribosome display method and its potential for advancing antibody discovery and development.

Generation of a Naïve Human scFv Phage Display Library and Panning Selection

Phage display antibody libraries have been successfully used as the essential tool to produce monoclonal antibodies against a plethora of targets ranging from diseases to native biologically important proteins as well as small molecules. It is well documented that diverse antibody genes are the major genetic source for the construction of a high-quality antibody library and selection of high-affinity antibodies. Naïve antibody libraries are derived using the IgM repertoire of healthy donors obtained from B-cells isolated from human peripheral blood mononuclear cell (PBMC). Single-chain fragment variable (scFv) is a routinely used format due to its smaller size and preference for phage display. The process involves the use of a two-step cloning method for library construction. The protocol also covers the biopanning process for target positive clone selection.

Isolation and characterization of a novel single-chain variable fragment (scFv) against Lymphocyte function-associated antigen-1 (LFA-1) using phage display method

Lymphocyte function-associated antigene-1 (LFA-1) is a well-described integrin found on lymphocytes and other leukocytes, which is known to be overexpressed in leukemias and lymphomas. This receptor plays a significant role in immune responses such as T-cell activation, leukocyte cell-cell interactions, and trafficking of leukocyte populations. Subsequently, binders of LFA-1 emerge as potential candidates for cancer and autoimmune therapy. This study used the phage display technique to construct and characterize a high-affinity single-chain fragment variable (scFv) antibody against LFA-1. After expression, purification, dialysis, and concentration of the recombinant LFA-1 protein, four female BALB/c mice were immunized, splenocyte's mRNA was extracted, and cDNA was synthesized. A scFv library was constructed by linking the amplified VH/Vκ fragments through a 72-bp linker using SOEing PCR. Next, the scFv gene fragments were cloned into the pComb-3XSS phagemid vector; thus, the phage library was developed. The selection process involved three rounds of phage-bio-panning, polyclonal, and monoclonal phage ELISA. AF17 was chosen and characterized among the positive clones through SDS-PAGE, Western blotting, indirect ELISA, and in-silico analyses. The results of the study showed the successful construction of a high-affinity scFv library against LFA-1. The accuracy of the AF17 production and its ability to bind to the LFA-1 were confirmed through SDS-PAGE, Western blot, and ELISA. This study highlights the potential application of the high-affinity AF17 against LFA-1 for targeting T lymphocytes for therapeutic purposes.

Progress on Phage Display Technology: Tailoring Antibodies for Cancer Immunotherapy

The search for innovative anti-cancer drugs remains a challenge. Over the past three decades, antibodies have emerged as an essential asset in successful cancer therapy. The major obstacle in developing anti-cancer antibodies is the need for non-immunogenic antibodies against human antigens. This unique requirement highlights a disadvantage to using traditional hybridoma technology and thus demands alternative approaches, such as humanizing murine monoclonal antibodies. To overcome these hurdles, human monoclonal antibodies can be obtained directly from Phage Display libraries, a groundbreaking tool for antibody selection. These libraries consist of genetically engineered viruses, or phages, which can exhibit antibody fragments, such as scFv or Fab on their capsid. This innovation allows the in vitro selection of novel molecules directed towards cancer antigens. As foreseen when Phage Display was first described, nowadays, several Phage Display-derived antibodies have entered clinical settings or are undergoing clinical evaluation. This comprehensive review unveils the remarkable progress in this field and the possibilities of using clever strategies for phage selection and tailoring the refinement of antibodies aimed at increasingly specific targets. Moreover, the use of selected antibodies in cutting-edge formats is discussed, such as CAR (chimeric antigen receptor) in CAR T-cell therapy or ADC (antibody drug conjugate), amplifying the spectrum of potential therapeutic avenues.

Antibody Phage Display Technology for Sensor-Based Virus Detection: Current Status and Future Prospects

Viruses are widespread in the environment, and many of them are major pathogens of serious plant, animal, and human diseases. The risk of pathogenicity, together with the capacity for constant mutation, emphasizes the need for measures to rapidly detect viruses. The need for highly sensitive bioanalytical methods to diagnose and monitor socially significant viral diseases has increased in the past few years. This is due, on the one hand, to the increased incidence of viral diseases in general (including the unprecedented spread of a new coronavirus infection, SARS-CoV-2), and, on the other hand, to the need to overcome the limitations of modern biomedical diagnostic methods. Phage display technology antibodies as nano-bio-engineered macromolecules can be used for sensor-based virus detection. This review analyzes the commonly used virus detection methods and approaches and shows the prospects for the use of antibodies prepared by phage display technology as sensing elements for sensor-based virus detection.

Recombinant antibodies by phage display for bioanalytical applications

Antibody phage display, aimed at preparing antibodies to defined antigens, is a useful replacement for hybridoma technology. The phage system replaces all work stages that follow animal immunization with simple procedures for manipulating DNA and bacteria. It enables the time needed to generate stable antibody-producing clones to be shortened considerably, making the process noticeably cheaper. Antibodies prepared by phage display undergo several affinity selection steps and can be used as selective receptors in biosensors. This article briefly describes the techniques used in the making of phage antibodies to various antigens. The possibilities and prospects are discussed of using phage antibodies as selective agents in analytical systems, including biosensors.

Protein Engineering: Advances in Phage Display for Basic Science and Medical Research

Functional Protein Engineering became the hallmark in biomolecule manipulation in the new millennium, building on and surpassing the underlying structural DNA manipulation and recombination techniques developed and employed in the last decades of 20th century. Because of their prominence in almost all biological processes, proteins represent extremely important targets for engineering enhanced or altered properties that can lead to improvements exploitable in healthcare, medicine, research, biotechnology, and industry. Synthetic protein structures and functions can now be designed on a computer and/or evolved using molecular display or directed evolution methods in the laboratory. This review will focus on the recent trends in protein engineering and the impact of this technology on recent progress in science, cancer- and immunotherapies, with the emphasis on the current achievements in basic protein research using synthetic antibody (sABs) produced by phage display pipeline in the Kossiakoff laboratory at the University of Chicago (KossLab). Finally, engineering of the highly specific binding modules, such as variants of Streptococcal protein G with ultra-high orthogonal affinity for natural and engineered antibody scaffolds, and their possible applications as a plug-and-play platform for research and immunotherapy will be described.