Construction of a Human Immune Library from Gallbladder Cancer Patients for the Single-Chain Fragment Variable (scFv) Antibody Selection against Claudin 18.2 via Phage Display

Gallbladder cancer (GBC) is a very aggressive malignant neoplasm of the biliary tract with a poor prognosis. There are no specific therapies for the treatment of GBC or early diagnosis tools; for this reason, the development of strategies and technologies that facilitate or allow an early diagnosis of GBC continues to be decisive. Phage display is a robust technique used for the production of monoclonal antibodies (mAbs) involving (1) the generation of gene libraries, (2) the screening and selection of isoforms related to an immobilized antigen, and (3) the in vitro maturation of the affinity of the antibody for the antigen. This research aimed to construct a human immune library from PBMCs of GBC patients and the isolation of scFv-phage clones with specificity against the larger extracellular loop belonging to claudin 18.2, which is an important biomarker overexpressed in GBC as well as gastric cancer. The immune-library-denominated GALLBLA1 was constructed from seven GBC patients and has a diversity of 6.12 × 1010pfu mL-1. After three rounds of panning, we were able to identify clones with specificity against claudin 18.2. GALLBLA1 can contribute to the selection, isolation, and recombinant production of new human mAbs candidates for the treatment of gastrointestinal cancers.

Nanobodies: a promising approach to treatment of viral diseases

Since their discovery in the 1990s, heavy chain antibodies have garnered significant interest in the scientific community. These antibodies, found in camelids such as llamas and alpacas, exhibit distinct characteristics from conventional antibodies due to the absence of a light chain in their structure. Furthermore, they possess a single antigen-binding domain known as VHH or Nanobody (Nb). With a small size of approximately 15 kDa, these Nbs demonstrate improved characteristics compared to conventional antibodies, including greater physicochemical stability and enhanced biodistribution, enabling them to bind inaccessible epitopes more effectively. As a result, Nbs have found numerous applications in various medical and veterinary fields, particularly in diagnostics and therapeutics. Advances in biotechnology have made the production of recombinant antibodies feasible and compatible with large-scale manufacturing. Through the construction of immune phage libraries that display VHHs and subsequent selection through biopanning, it has become possible to isolate specific Nbs targeting pharmaceutical targets of interest, such as viruses. This review describes the processes involved in nanobody production, from hyperimmunization to purification, with the aim of their application in the pharmaceutical industry.

Generation of an Ovomucoid-Immune scFv Library for the Development of Novel Immunoassays in Hen's Egg Detection

Hen's egg allergy is the second most common food allergy among infants and young children. The possible presence of undeclared eggs in foods poses a significant risk to sensitized individuals. Therefore, reliable egg allergen detection methods are needed to ensure compliance with food labeling and improve consumer protection. This work describes for the first time the application of phage display technology for the generation of a recombinant antibody aimed at the specific detection of hen's ovomucoid. First, a single-chain variable fragment (scFv) library was constructed from mRNA isolated from the spleen of a rabbit immunized with ovomucoid. After rounds of biopanning, four binding clones were isolated and characterized. Based on the best ovomucoid-binding candidate SR-G1, an indirect phage enzyme-linked immunosorbent assay (phage-ELISA) was developed, reaching limits of detection and quantitation of 43 and 79 ng/mL of ovomucoid, respectively. The developed ELISA was applied to the analysis of a wide variety of food products, obtaining a good correlation with a commercial egg detection assay used as a reference. Finally, in silico modeling of the antigen-antibody complex revealed that the main interactions most likely occur between the scFv heavy chain and the ovomucoid domain-III, the most immunogenic region of this allergen.

Construction of an alpaca immune antibody library for the selection of nanobodies against Drosophila melanogaster proteins

Introduction: Drosophila melanogaster is a model organism for studying developmental biology and human neural disorders. Nanobodies are the variable domains of the heavy chains of camelid heavy-chain antibodies (VHHs) with high affinity to their antigens and have applications in basic research, similar to traditional antibodies. In addition, nanobodies acting as functionalized antibodies or protein binders have become an additional valuable approach in Drosophila. This study aimed to develop a VHH library against Drosophila proteins and confirm its availability by retrieving some Drosophila protein-specific nanobodies from the library. Methods: An alpaca was first immunized with Drosophila embryo lysate and then its lymphocytes were isolated. Total RNA was extracted and cDNA was synthesized. The vhh sequences were amplified by two round PCR, which were then ligated to a phage display vector pADL-10b. The ligation products were transduced into SS320 competent cells to generate a VHH library. From this library, nanobodies against CG7544, Myc, and CyclinE was enriched and screened by phage display technology and ELISA. DNA sequences of identified nanobodies were cloned into pADL-10b-Flag-His for expression and purification in Escherichia coli SS320. Binding ability of purified nanobodies with corresponding antigens were determined by ELISA and surface plasmon resonance in vitro. Results: In this study, an immune VHH library against Drosophila embryo proteins was generated with a capacity of 3 × 10⁷. From this library, eight nanobodies against three Drosophila proteins, Myc, CyclinE, and CG7544, were identified and the DNA sequences of these nanobodies were obtained. These nanobodies were successfully expressed and purified from Escherichia coli SS320, and were demonstrated to bind corresponding antigens with high affinity in vitro. Moreover, the equilibrium constant between the highest enriched nanobodies and corresponding antigens were calculated. Conclusion: In summary, we report the availability of an immune VHH library and a highly efficient panning strategy for nanobodies against proteins in Drosophila.

Construction of a Fab Library Merging Chains from Semisynthetic and Immune Origin, Suitable for Developing New Tools for Gluten Immunodetection in Food

The observed increase in the prevalence of gluten-related disorders has prompted the development of novel immunological systems for gluten detection in foodstuff. The innovation on these methods relies on the generation of new antibodies, which might alternatively be obtained by molecular evolution methods such as phage display. This work presents a novel approach for the generation of a Fab library by merging semi-synthetic heavy chains built-up from a pre-existent recombinant antibody fragment (dAb8E) with an immune light chain set derived from celiac donors. From the initial phage population (10⁷ candidates) and after three rounds of selection and amplification, four different clones were isolated for further characterization. The phage Fab8E-4 presented the best features to be applied in an indirect ELISA for the detection of gluten in foods, resulting in improved specificity and sensitivity.

A SARS-CoV-2 neutralizing antibody selected from COVID-19 patients binds to the ACE2-RBD interface and is tolerant to most known RBD mutations

The novel betacoronavirus severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) causes a form of severe pneumonia disease called coronavirus disease 2019 (COVID-19). To develop human neutralizing anti-SARS-CoV-2 antibodies, antibody gene libraries from convalescent COVID-19 patients were constructed and recombinant antibody fragments (scFv) against the receptor-binding domain (RBD) of the spike protein were selected by phage display. The antibody STE90-C11 shows a subnanometer IC₅₀ in a plaque-based live SARS-CoV-2 neutralization assay. The in vivo efficacy of the antibody is demonstrated in the Syrian hamster and in the human angiotensin-converting enzyme 2 (hACE2) mice model. The crystal structure of STE90-C11 Fab in complex with SARS-CoV-2-RBD is solved at 2.0 Å resolution showing that the antibody binds at the same region as ACE2 to RBD. The binding and inhibition of STE90-C11 is not blocked by many known emerging RBD mutations. STE90-C11-derived human IgG1 with FcγR-silenced Fc (COR-101) is undergoing Phase Ib/II clinical trials for the treatment of moderate to severe COVID-19.

A Generic Procedure for the Isolation of pH- and Magnesium-Responsive Chicken scFvs for Downstream Purification of Human Antibodies

Affinity chromatography provides an excellent platform for protein purification, which is a key step in the large scale downstream processing of therapeutic monoclonal antibodies (Mabs). Protein A chromatography constitutes the gold standard for Mab purification. However, the required acidic conditions (2.8–3.5) for elution from the affinity matrix limit their applicability, particularly for next generation antibodies and antibody fusion proteins, since denaturation and irreversible aggregation can occur due to the acidic buffer conditions. Here we describe a generic procedure for the generation of antigen-specific chromatography ligands with tailor-made elution conditions. To this end, we generated a scFv-library based on mRNA from a chicken immunized with human Fc. The antibody repertoire was displayed on yeast Saccharomyces cerevisiae screened via FACS toward pH- and magnesium-responsive scFvs which specifically recognize human IgG antibodies. Isolated scFvs were reformatted, produced in Escherichia coli and immobilized on NHS-agarose columns. Several scFvs were identified that mediated antibody binding at neutral pH and antibody recovery at pH values of 4.5 and higher or even at neutral pH upon MgCl₂ exposure. The iterative screening methodology established here is generally amenable to the straightforward isolation of stimulus-responsive antibodies that may become valuable tools for a variety of applications.

A Murine Monoclonal Antibody With Potent Neutralization Ability Against Human Adenovirus 7

B1-type human adenoviruses (HAdVs) HAdV-3, HAdV-7, and HAdV-55 have caused epidemics in North America, Asia, and Europe. However, to date, no adenovirus vaccines or antiviral drugs have been approved for general use. In the present work, a scFv-phage immune library was constructed and mouse monoclonal antibody (MMAb) 10G12 was obtained through selection. 10G12 is specific for HAdV-7 and binds the hexon loop1 and loop2 (LP12), resulting in strong neutralization activity against HAdV-7. Additionally, it is stable in serum and buffer at various pH values. The findings provide insight into adenovirus and antibody responses and may facilitate the design and development of adenovirus vaccines and antiviral drugs.

Development and Utilization of VHH Antibodies Derived from Camelus Dromedarius Against Foot-and-Mouth Disease Virus

Foot-and-mouth disease (FMD) is an acute, highly contagious, and economically devastating viral disease of domestic and wildlife species. For effective implementation of FMD control program, there is an imperative need for developing a rapid, sensitive, and specific diagnostics which help in the identification of serotypes involved in the outbreaks. The humoral immune response of the Camelidae is unique since in these animals 75% of circulating antibodies are constituted by heavy-chain antibodies and 25% are conventional immunoglobulin with two identical heavy chains. In the present study, we developed and characterized FMD virus-specific single-domain heavy-chain antibodies (VHHs) against inactivated whole-virus antigens of FMDV serotypes O (INDR2/1975), A (IND40/2000), and Asia 1 (IND63/1972) vaccine strains. After six rounds of panning and enrichment, these VHHs were stably expressed in Escherichia coli cells. The VHHs directed against outer capsid proteins of FMD virus were successfully utilized as the capture antibody in liquid-phase blocking ELISA (LPBE) thus replacing rabbit coating antibodies. Our study demonstrated the utility of FMD virus-specific VHHs as potential candidates in FMD research and diagnostic application.

Antibody-Based Protective Immunity against Helminth Infections: Antibody Phage Display Derived Antibodies against BmR1 Antigen

Helminth parasite infections are significantly impacting global health, with more than two billion infections worldwide with a high morbidity rate. The complex life cycle of the nematodes has made host immune response studies against these parasites extremely difficult. In this study, we utilized two phage antibody libraries; the immune and naïve library were used to identify single chain fragment variable (scFv) clones against a specific filarial antigen (BmR1). The V-gene analysis of isolated scFv clones will help shed light on preferential VDJ gene segment usage against the filarial BmR1 antigen in healthy and infected states. The immune library showed the usage of both lambda and kappa light chains. However, the naïve library showed preferential use of the lambda family with different amino acid distributions. The binding characteristics of the scFv clones identified from this work were analyzed by immunoassay and immunoaffinity pull down of BmR1. The work highlights the antibody gene usage pattern of a naïve and immune antibody library against the same antigen as well as the robust nature of the enriched antibodies for downstream applications.

Comparing CDRH3 diversity captured from secondary lymphoid organs for the generation of recombinant human antibodies

The plasticity of natural immunoglobulin repertoires can be exploited for the generation of phage display libraries. Secondary lymphoid organs, such as the spleen and the lymph nodes, constitute interesting sources of diversity because they are rich in B cells, part of which can be affinity matured. These organs, however, differ in their anatomical structure, reflecting the different fluids they drain, which affects the B cell repertoires. The CDRH3 repertoires from these organs, extracted from naïve or immunized mice, were compared in the context of phage display libraries using human antibody framework families. Deep sequencing analysis revealed that all libraries displayed different CDRH3 repertoires, but the one derived from lymph nodes of naïve mice was the most diverse. Library performance was assessed by in vitro selection. For both organs, immunization increased substantially the frequency of molecules able to bind to the immunogen. The library derived from lymph nodes from naïve mice, however, was the most effective in generating diverse and high affinity candidates. These results illustrate that the use of a biased CDRH3 repertoire increases the performance of libraries, but reduces the clonal diversity, which may be detrimental for certain strategies.

Antibodies against non-immunizing antigens derived from a large immune scFv library

Target-specific antibodies can be rapidly enriched and identified from an antibody library using phage display. Large, naïve antibody libraries derived from synthetic or unimmunized sources can yield antibodies against virtually any antigen, whereas libraries from immunized sources tend to be smaller and are used exclusively against the antigen of immunization. In this study, 25 scFv libraries made from the spleens of immunized rabbits, each with a size ranging from 10(8) to higher than 10(9), were combined into a single large library with > 10(10) individual clones. Panning of this combined library yielded target-specific rabbit scFv clones against many non-immunizing antigens, including proteins, peptides, and a small molecule. Notably, specific scFv clones against a rabbit self-antigen (rabbit serum albumin) and a phosphorylated protein (epidermal growth factor receptor pTyr1173) could be isolated from the library. These results suggest that the immune library contained a significant number of unimmunized clones and that a sufficiently large immune library can be utilized similarly to a naïve library, i.e., against various non-immunizing antigens to yield specific antibodies.

Non-human primate immune libraries combined with germline humanization: an (almost) new, and powerful approach for the isolation of therapeutic antibodies

Panning of libraries constructed from immunised non-human primates (NHP) has not been widely used, even though this has proven to be a successful approach for the isolation of human-like antibody fragments with affinities in the nanomolar to the picomolar range. As recently demonstrated, after initial isolation of antibodies with such high affinities, germline humanization may be applied to these Fabs or scFvs to increase the similarity of their framework regions with those encoded by human germline genes. 'Germlinized' antibody fragments may be converted to full size IgGs; indications are given that these IgGs could be better tolerated in clinical use than human antibodies. The use of the combination of NHP immune libraries and germline humanization thus may compete with use of libraries of human origin, whether naïve or immune, and with synthetic libraries. In this report, the various approaches will be compared, and advantages of the two-step NHP-based method, as well as corresponding intellectual property aspects, will be discussed.