DNA immunization as a technology platform for monoclonal antibody induction

Revolutionizing snakebite care with novel antivenoms: Breakthroughs and barriers

Snakebite envenoming (SBE) is a global public health concern, primarily due to the lack of effective antivenom for treating snakebites inflicted by medically significant venomous snakes prevalent across various geographic locations. The rising demand for safe, cost-effective, and potent snakebite treatments highlights the urgent need to develop alternative therapeutics targeting relevant toxins. This development could provide promising discoveries to create novel recombinant solutions, leveraging human monoclonal antibodies, synthetic peptides and nanobodies. Such technologies as recombinant DNA, peptide and epitope mapping phage display etc) have the potential to exceed the traditional use of equine polyclonal antibodies, which have long been used in antivenom production. Recombinant antivenom can be engineered to target certain toxins that play a critical role in snakebite pathology. This approach has the potential to produce antivenom with improved efficacy and safety profiles. However, there are limitations and challenges associated with these emerging technologies. Therefore, identifying the limitations is critical for overcoming the associated challenges and optimizing the development of recombinant antivenoms. This review is aimed at presenting a thorough overview of diverse technologies used in the development of recombinant antivenom, emphasizing their limitations and offering insights into prospects for advancing recombinant antivenoms.

Comparison of Anti-rabies Virus Nucleoprotein IgY Prepared by DNA Immunization and Protein Immunization

Immunization of egg-laying hens with viral antigens efficiently produces large amounts of virus-specific IgY antibodies from egg yolks. A supply of practical and economical antibodies against the rabies virus is being desired worldwide. We immunized hens with the antigen gene DNA of the rabies virus, purified specific IgY antibodies from the egg yolk, and characterized the immuno-protein chemistry for use as a diagnosis. To prepare specific IgY antibodies against rabies virus nucleoprotein (RV-N) by DNA immunization, laying hens were pre-injected with λ-carrageenan or Freund's complete adjuvant to increase local immune activity (pre-immune stimulation), and then immunized with RV-N recombinant plasmid DNA. RV-N-specific IgY antibodies were prepared from egg yolks of immunized hens. For comparison, conventional protein antigen immunization was also used to induce the production of RV-N-specific IgY antibodies. Laying hens were immunized with an RV-N protein antigen and RV-N-specific IgY was purified from egg yolks. The binding activity against RV-N antigens was examined using IgY samples prepared by DNA (with pre-immune stimulation) and protein immunization. Immunohistochemical staining showed that IgY antibodies prepared by protein immunization strongly detected viral antigens in the brain sections of dogs infected with the virus, whereas IgY antibodies prepared by DNA immunization did not. Enzyme-linked immunosorbent assay was performed using a commercially available rabies vaccine (inactivated virus) treated with 10% formalin and heating (60°C, 30 min and 90°C, 5 min). IgY prepared by DNA immunization had weaker reactivity with denatured antigens and lower antigen concentrations than IgY prepared by protein immunization. These results suggest that it is necessary to develop a DNA immunization method for inducing IgY antibodies against the rabies virus that strongly bind to native and denatured antigens to prepare specific IgYs that can be used for antigen detection in clinical tests.

CD4-1 and CD4-2 single positive are two major CD4 lymphocyte subpopulations in ginbuna crucian carp Carassius auratus langsdorfii

In this study, we established a murine cell line that expresses ginbuna crucian carp (ginbuna) CD4-2 and used it to develop an anti-CD4-2 monoclonal antibody (mAb). An established mAb, named D5, showed good reactivities to BALB/3T3 cells expressing CD4-2 and a lymphocyte population in the ginbuna leukocytes. Gene expression analysis showed that D5⁺ cells express CD4-2 and TCRβ genes but not CD4-1 and IgM genes, meanwhile May Grunwald-Giemsa staining of sorted D5⁺ cells had the typical morphology of lymphocytes. Two-color immunofluorescence analysis with anti-CD4-1 mAb (6D1) and anti-CD4-2 mAb (D5) by flow cytometry revealed that the percentages of CD4-1 single positive (SP) and CD4-2 SP lymphocytes were comparatively higher than CD4-1/CD4-2 double positive (CD4 DP) lymphocytes in all tissues examined in ginbuna. The highest percentages of CD4-2 SP cells (∼40%) were found in the thymus, while the head-kidney exhibited the highest percentages of CD4-1 SP (∼30%) and CD4 DP (∼5%) cells. These findings indicated that ginbuna CD4⁺ lymphocyte population consists of two major subpopulations (CD4-1 SP and CD4-2 SP) and a minor subset (CD4 DP).

Generation of a single-cell B cell atlas of antibody repertoires and transcriptomes to identify signatures associated with antigen specificity

Although new genomics-based pipelines have potential to augment antibody discovery, these methods remain in their infancy due to an incomplete understanding of the selection process that governs B cell clonal selection, expansion, and antigen specificity. Furthermore, it remains unknown how factors such as aging and reduction of tolerance influence B cell selection. Here we perform single-cell sequencing of antibody repertoires and transcriptomes of murine B cells following immunizations with a model therapeutic antigen target. We determine the relationship between antibody repertoires, gene expression signatures, and antigen specificity across 100,000 B cells. Recombinant expression and characterization of 227 monoclonal antibodies revealed the existence of clonally expanded and class-switched antigen-specific B cells that were more frequent in young mice. Although integrating multiple repertoire features such as germline gene usage and transcriptional signatures failed to distinguish antigen-specific from nonspecific B cells, other features such as immunoglobulin G (IgG) subtype and sequence composition correlated with antigen specificity.

Breaking barriers in antibody discovery: harnessing divergent species for accessing difficult and conserved drug targets

To exploit highly conserved and difficult drug targets, including multipass membrane proteins, monoclonal antibody discovery efforts increasingly rely on the advantages offered by divergent species such as rabbits, camelids, and chickens. Here, we provide an overview of antibody discovery technologies, analyze gaps in therapeutic antibodies that stem from the historic use of mice, and examine opportunities to exploit previously inaccessible targets through discovery now possible in alternate species. We summarize the clinical development of antibodies raised from divergent species, discussing how these animals enable robust immune responses against highly conserved binding sites and yield antibodies capable of penetrating functional pockets via long HCDR3 regions. We also discuss the value of pan-reactive molecules often produced by these hosts, and how these antibodies can be tested in accessible animal models, offering a faster path to clinical development.

Development of therapeutic antibodies for the treatment of diseases

Since the first monoclonal antibody drug, muromonab-CD3, was approved for marketing in 1986, 165 antibody drugs have been approved or are under regulatory review worldwide. With the approval of new drugs for treating a wide range of diseases, including cancer and autoimmune and metabolic disorders, the therapeutic antibody drug market has experienced explosive growth. Monoclonal antibodies have been sought after by many biopharmaceutical companies and scientific research institutes due to their high specificity, strong targeting abilities, low toxicity, side effects, and high development success rate. The related industries and markets are growing rapidly, and therapeutic antibodies are one of the most important research and development areas in the field of biology and medicine. In recent years, great progress has been made in the key technologies and theoretical innovations provided by therapeutic antibodies, including antibody-drug conjugates, antibody-conjugated nuclides, bispecific antibodies, nanobodies, and other antibody analogs. Additionally, therapeutic antibodies can be combined with technologies used in other fields to create new cross-fields, such as chimeric antigen receptor T cells (CAR-T), CAR-natural killer cells (CAR-NK), and other cell therapy. This review summarizes the latest approved or in regulatory review therapeutic antibodies that have been approved or that are under regulatory review worldwide, as well as clinical research on these approaches and their development, and outlines antibody discovery strategies that have emerged during the development of therapeutic antibodies, such as hybridoma technology, phage display, preparation of fully human antibody from transgenic mice, single B-cell antibody technology, and artificial intelligence-assisted antibody discovery.

An efficient approach for SARS-CoV-2 monoclonal antibody production via modified mRNA-LNP immunization

Throughout the COVID-19 pandemic, many prophylactic and therapeutic drugs have been evaluated and introduced. Among these treatments, monoclonal antibodies (mAbs) that bind to and neutralize SARS-CoV-2 virus have been applied as complementary and alternative treatments to vaccines. Although different methodologies have been utilized to produce mAbs, traditional hybridoma fusion technology is still commonly used for this purpose due to its unmatched performance record. In this study, we coupled the hybridoma fusion strategy with mRNA-lipid nanoparticle (LNP) immunization. This time-saving approach can circumvent biological and technical hurdles, such as difficult-to-express membrane proteins, antigen instability, and the lack of posttranslational modifications on recombinant antigens. We used mRNA-LNP immunization and hybridoma fusion technology to generate mAbs against the receptor binding domain (RBD) of SARS-CoV-2 spike (S) protein. Compared with traditional protein-based immunization approaches, inoculation of mice with RBD mRNA-LNP induced higher titers of serum antibodies and markedly increased serum neutralizing activity. The mAbs we obtained can bind to SARS-CoV-2 RBDs from several variants. Notably, RBD-mAb-3 displayed particularly high binding affinities and neutralizing potencies against both Alpha and Delta variants. In addition to introducing specific mAbs against SARS-CoV-2, our data generally demonstrate that mRNA-LNP immunization may be useful to quickly generate highly functional mAbs against emerging infectious diseases.

Immuno-dominant dengue NS1 peptides as antigens for production of monoclonal antibodies

Synthetic peptides have recently become common as antigens for antibody production. Peptides are short chains of amino acids that can be used to elicit an immune response. The immunogenicity of the peptide antigens varies depending on the length, charge, solubility, and amino acids contained in the peptide sequence. Dengue NS1 protein is an important target antigen in the early detection of dengue infection. In this study, peptides corresponding to a highly conserved region from the dengue NS1 region were designed and synthesized. Balb/C mice were immunized against each peptide and spleen cells extracted from the immunized mice were fused with NS0 murine myeloma cells. Hybridoma clones obtained from the fusions were tested against peptides using ELISA. Out of 1,830 growing clones, 28 clones produced antibodies reacting with dengue NS1 peptides. A purified monoclonal antibody reacting with all four peptides was tested for reactivity with dengue NS1 native protein using dengue-confirmed serum and urine samples. The monoclonal antibody shows significant reactivity with both serum and urine. The findings of the current research can be used to detect dengue infection using urine, which ultimately results in the prevention of dengue epidemics through painless diagnosis, following treatment, and patient management to safeguard human and economic wellness.

Recent Progress in the Discovery and Development of Monoclonal Antibodies against Viral Infections

Monoclonal antibodies (mAbs), the new revolutionary class of medications, are fast becoming tools against various diseases thanks to a unique structure and function that allow them to bind highly specific targets or receptors. These specialized proteins can be produced in large quantities via the hybridoma technique introduced in 1975 or by means of modern technologies. Additional methods have been developed to generate mAbs with new biological properties such as humanized, chimeric, or murine. The inclusion of mAbs in therapeutic regimens is a major medical advance and will hopefully lead to significant improvements in infectious disease management. Since the first therapeutic mAb, muromonab-CD3, was approved by the U.S. Food and Drug Administration (FDA) in 1986, the list of approved mAbs and their clinical indications and applications have been proliferating. New technologies have been developed to modify the structure of mAbs, thereby increasing efficacy and improving delivery routes. Gene delivery technologies, such as non-viral synthetic plasmid DNA and messenger RNA vectors (DMabs or mRNA-encoded mAbs), built to express tailored mAb genes, might help overcome some of the challenges of mAb therapy, including production restrictions, cold-chain storage, transportation requirements, and expensive manufacturing and distribution processes. This paper reviews some of the recent developments in mAb discovery against viral infections and illustrates how mAbs can help to combat viral diseases and outbreaks.

Development and Validation of Rapid In-House Diagnostic ELISA Kits for Detection of Human Orthopneumovirus in Clinical Samples

Currently, the standard assay employed to diagnose human orthopneumovirus infection is real-time reverse transcriptase PCR assay (rRT-PCR), a costly and time-consuming procedure that requires the manipulation of infectious viruses. In addition to RT-PCR, serological tests can complement the molecular diagnostic methods and have proven to be important tools in sero-surveillance. In this study, we report the development, optimization, and validation of a novel and rapid in-house diagnostic ELISA kit to detect human orthopneumovirus in clinical samples. We developed three sensitive ELISA formats through the immunization of rats with novel recombinant pPOE-F or pPOE-TF vectors. The two vectors expressed either the full-length (pPOE-F) or the truncated form (pPOE-TF) of the fusion (F) protein. The developed ELISA kits were optimized for coating buffer, capture antibody, blocking buffer, sample antigen, detection antibodies, and peroxidase-conjugated antibody, and validated using 75 rRT-PCR-confirmed nasopharyngeal aspirate (NPA) human orthopneumovirus samples and 25 negative samples collected from hospitalized children during different epidemic seasons between 2014 and 2017. Our results indicate that rats immunized with pPOE-F or pPOE-TF showed significant induction of high levels of MPAs. Validation of the ELISA method was compared to the rRT-PCR and the sensitivity hierarchy of these developed ELISA assays was considered from highest to lowest: indirect competitive inhibition ELISA (93.3%) > indirect antigen-capture ELISA (90.6%) > direct antigen-capture ELISA (86.6%). The development of the rapid in-house diagnostic ELISA kits described in this study demonstrates that a specific, rapid and sensitive test for human orthopneumovirus antigens could be successfully applied to samples collected from hospitalized children during different epidemics and can help in the efficient diagnosis of respiratory syncytial viral infections.

Improving antibody drug development using bionanotechnology

Monoclonal antibodies are being used to treat a remarkable breadth of human disorders. Nevertheless, there are several key challenges at the earliest stages of antibody drug development that need to be addressed using simple and widely accessible methods, especially related to generating antibodies against membrane proteins and identifying antibody candidates with drug-like biophysical properties (high solubility and low viscosity). Here we highlight key bionanotechnologies for preparing functional and stable membrane proteins in diverse types of lipoparticles that are being used to improve antibody discovery and engineering efforts. We also highlight key bionanotechnologies for high-throughput and ultra-dilute screening of antibody biophysical properties during antibody discovery and optimization that are being used for identifying antibodies with superior combinations of in vitro (formulation) and in vivo (half-life) properties.

A novel DNA and protein combination COVID-19 vaccine formulation provides full protection against SARS-CoV-2 in rhesus macaques

The current study aims to develop a safe and highly immunogenic COVID-19 vaccine. The novel combination of a DNA vaccine encoding the full-length Spike (S) protein of SARS-CoV-2 and a recombinant S1 protein vaccine induced high level neutralizing antibody and T cell immune responses in both small and large animal models. More significantly, the co-delivery of DNA and protein components at the same time elicited full protection against intratracheal challenge of SARS-CoV-2 viruses in immunized rhesus macaques. As both DNA and protein vaccines have been proven safe in previous human studies, and DNA vaccines are capable of eliciting germinal center B cell development, which is critical for high-affinity memory B cell responses, the DNA and protein co-delivery vaccine approach has great potential to serve as a safe and effective approach to develop COVID-19 vaccines that provide long-term protection.

A single subcutaneous or intranasal immunization with adenovirus-based SARS-CoV-2 vaccine induces robust humoral and cellular immune responses in mice

Optimal vaccines are needed for sustained suppression of SARS-CoV-2 and other novel coronaviruses. Here, we developed a recombinant type 5 adenovirus vector encoding the gene for the SARS-CoV-2 S1 subunit antigen (Ad5.SARS-CoV-2-S1) for COVID-19 immunization and evaluated its immunogenicity in mice. A single immunization with Ad5.SARS-CoV-2-S1 via S.C. injection or I.N delivery induced robust antibody and cellular immune responses. Vaccination elicited significant S1-specific IgG, IgG1, and IgG2a endpoint titers as early as 2 weeks, and the induced antibodies were long lasting. I.N. and S.C. administration of Ad5.SARS-CoV-2-S1 produced S1-specific GC B cells in cervical and axillary LNs, respectively. Moreover, I.N. and S.C. immunization evoked significantly greater antigen-specific T-cell responses compared to unimmunized control groups with indications that S.C. injection was more effective than I.N. delivery in eliciting cellular immune responses. Mice vaccinated by either route demonstrated significantly increased virus-specific neutralization antibodies on weeks 8 and 12 compared to control groups, as well as BM antibody forming cells (AFC), indicative of long-term immunity. Thus, this Ad5-vectored SARS-CoV-2 vaccine candidate showed promising immunogenicity following delivery to mice by S.C. and I.N. routes of administration, supporting the further development of Ad-based vaccines against COVID-19 and other infectious diseases for sustainable global immunization programs.

Development of Anti-Human CC Chemokine Receptor 9 Monoclonal Antibodies for Flow Cytometry

CC chemokine receptor 9 (CCR9) belongs to the beta chemokine receptor family and is mainly distributed on the surface of immature T lymphocytes and enterocytes. This receptor is highly expressed in rheumatoid arthritis, colitis, type 2 diabetes, and various tumors. Therefore, more sensitive monoclonal antibodies (mAbs) need to be developed to predict the prognosis of many high CCR9 expression diseases. Because CCR9 is a structurally unstable G protein-coupled receptor, it has been difficult to develop anti-CCR9 mAbs using the traditional method. This study developed anti-human CCR9 (hCCR9) mAbs for flow cytometry using a Cell-Based Immunization and Screening (CBIS) method. Two mice were immunized with hCCR9-overexpressed Chinese hamster ovary (CHO)-K1 cells (CHO/hCCR9), and hybridomas showing strong signals from CHO/hCCR9 and no signals from CHO-K1 cells were selected by flow cytometry. We established an anti-hCCR9 mAb, C₉Mab-1 (IgG₁, kappa), which detected hCCR9 in MOLT-4 leukemia T lymphoblast cells and CHO/hCCR9 cells by flow cytometry. Our study showed that an anti-hCCR9 mAb was developed more rapidly by the CBIS method than the previous method.

Therapeutic Antibodies Targeting Potassium Ion Channels

Monoclonal antibodies combine specificity and high affinity binding with excellent pharmacokinetic properties and are rapidly being developed for a wide range of drug targets including clinically important potassium ion channels. Nonetheless, while therapeutic antibodies come with great promise, K⁺ channels represent particularly difficult targets for biologics development for a variety of reasons that include their dynamic structures and relatively small extracellular loops, their high degree of sequence conservation (leading to immune tolerance), and their generally low-level expression in vivo. The process is made all the more difficult when large numbers of antibody candidates must be screened for a given target, or when lead candidates fail to cross-react with orthologous channels in animal disease models due to their highly selective binding properties. While the number of antibodies targeting potassium channels in preclinical or clinical development is still modest, significant advances in the areas of protein expression and antibody screening are converging to open the field to an avalanche of new drugs. Here, the opportunities and constraints associated with the discovery of antibodies against K⁺ channels are discussed, with an emphasis on novel technologies that are opening the field to exciting new possibilities for biologics development.

Animal immunization merges with innovative technologies: A new paradigm shift in antibody discovery

Animal-derived antibody sources, particularly, transgenic mice that are engineered with human immunoglobulin loci, along with advanced antibody generation technology platforms have facilitated the discoveries of human antibody therapeutics. For example, isolation of antigen-specific B cells, microfluidics, and next-generation sequencing have emerged as powerful tools for identifying and developing monoclonal antibodies (mAbs). These technologies enable not only antibody drug discovery but also lead to the understanding of B cell biology, immune mechanisms and immunogenetics of antibodies. In this perspective article, we discuss the scientific merits of animal immunization combined with advanced methods for antibody generation as compared to animal-free alternatives through in-vitro-generated antibody libraries. The knowledge gained from animal-derived antibodies concerning the recombinational diversity, somatic hypermutation patterns, and physiochemical properties is found more valuable and prerequisite for developing in vitro libraries, as well as artificial intelligence/machine learning methods to discover safe and effective mAbs.

A Comprehensive Review of the Global Efforts on COVID-19 Vaccine Development

This report examines various vaccine platforms including inactivated vaccines, protein-based vaccines, viral vector vaccines, and nucleic acid (DNA or mRNA) vaccines, and their ways of producing immunogens in cells.

A Novel Gene Delivery Vector of Agonistic Anti-Radioprotective 105 Expressed on Cell Membranes Shows Adjuvant Effect for DNA Immunization Against Influenza

Radioprotective 105 (RP105) (also termed CD180) is an orphan and unconventional Toll-like receptor (TLR) that lacks an intracellular signaling domain. The agonistic anti-RP105 monoclonal antibody (mAb) can cross-link RP105 on B cells, resulting in the proliferation and activation of B cells. Anti-RP105 mAb also has a potent adjuvant effect, providing higher levels of antigen-specific antibodies compared to alum. However, adjuvanticity is required for the covalent link between anti-RP105 mAb and the antigen. This is a possible obstacle to immunization due to the link between anti-RP105 mAb and some antigens, especially multi-transmembrane proteins. We have previously succeeded in inducing rapid and potent recombinant mAbs in mice using antibody gene-based delivery. To simplify the covalent link between anti-RP105 mAb and antigens, we generated genetic constructs of recombinant anti-RP105 mAb (αRP105) bound to the transmembrane domain of the IgG-B cell receptor (TM) (αRP105-TM), which could enable the anti-RP105 mAb to link the antigen via the cell membrane. We confirmed the expression of αRP105-TM and the antigen hemagglutinin, which is a membrane protein of the influenza virus, on the same cell. We also found that αRP105-TM could activate splenic B cells, including both mature and immature cells, depending on the cell surface RP105 in vitro. To evaluate the adjuvanticity of αRP105-TM, we conducted DNA immunization in mice with the plasmids encoding αRP105-TM and hemagglutinin, followed by challenge with an infection of a lethal dose of an influenza virus. We then obtained partially but significantly hemagglutinin-specific antibodies and observed protective effects against a lethal dose of influenza virus infection. The current αRP105-TM might provide adjuvanticity for a vaccine via a simple preparation of the expression plasmids encoding αRP105-TM and of that encoding the target antigen.

Antigen Design for Successful Isolation of Highly Challenging Therapeutic Anti-GPCR Antibodies

G-protein-coupled receptors (GPCR) transmit extracellular signals into cells to regulate a variety of cellular functions and are closely related to the homeostasis of the human body and the progression of various types of diseases. Great attention has been paid to GPCRs as excellent drug targets, and there are many commercially available small-molecule chemical drugs against GPCRs. Despite this, the development of therapeutic anti-GPCR antibodies has been delayed and is challenging due to the difficulty in preparing active forms of GPCR antigens, resulting from their low cellular expression and complex structures. Here, we focus on anti-GPCR antibodies that have been approved or are subject to clinical trials and present various technologies to prepare active GPCR antigens that enable the isolation of therapeutic antibodies to proceed toward clinical validation.

A review of antibody-based therapeutics targeting G protein-coupled receptors: an update

INTRODUCTION

G protein-coupled receptors (GPCRs) play key roles in many biological functions and are linked to many diseases across all therapeutic areas. As such, GPCRs represent a significant opportunity for antibody-based therapeutics.

AREAS COVERED

The structure of the major GPCR families is summarized in the context of choice of antigen source employed in the drug discovery process and receptor biology considerations which may impact on targeting strategies. An overview of the therapeutic GPCR-antibody target landscape and the diversity of current therapeutic programs is provided along with summary case studies for marketed antibody drugs or those in advanced clinical studies. Antibodies in early clinical studies and the emergence of next-generation modalities are also highlighted.

EXPERT OPINION

The GPCR-antibody pipeline has progressed significantly with a number of technical developments enabling the successful resolution of some of the challenges previously encountered and this has contributed to the growing interest in antibody-based therapeutics addressing this target class.

How can monoclonal antibodies be harnessed against neglected tropical diseases and other infectious diseases?

Introduction: Monoclonal antibody-based therapies now represent the single-largest class of molecules undergoing clinical investigation. Although a handful of different monoclonal antibodies have been clinically approved for bacterial and viral indications, including rabies, therapies based on monoclonal antibodies are yet to fully enter the fields of neglected tropical diseases and other infectious diseases. Areas covered: This review presents the current state-of-the-art in the development and use of monoclonal antibodies against neglected tropical diseases and other infectious diseases, including viral, bacterial, and parasitic infections, as well as envenomings by animal bites and stings. Additionally, a short section on mushroom poisonings is included. Key challenges for developing antibody-based therapeutics are discussed for each of these fields. Expert opinion: Neglected tropical diseases and other infectious diseases represent a golden opportunity for academics and technology developers for advancing our scientific capabilities within the understanding and design of antibody cross-reactivity, use of oligoclonal antibody mixtures for multi-target neutralization, novel immunization methodologies, targeting of evasive pathogens, and development of fundamentally novel therapeutic mechanisms of action. Furthermore, a huge humanitarian and societal impact is to gain by exploiting antibody technologies for the development of biotherapies against diseases, for which current treatment options are suboptimal or non-existent.

Using DNA Immunization to Elicit Monoclonal Antibodies in Mice, Rabbits, and Humans

In recent vaccine studies, DNA immunization was found to effectively stimulate both innate and adaptive immunities to elicit high levels of antigen-specific antibody responses. The DNA molecule itself can activate multiple pathways of innate immunity. The in vivo production of antigens allows for presentation by major histocompatibility complexes, so that T-cell responses are generated to help in the development of antigen-specific B cells, leading to high-affinity antibody response. By using the same process, DNA immunization should also be effective at producing functionally potent monoclonal antibodies (mAbs). Furthermore, the in vivo expressed proteins can maximally maintain the native structures and go through appropriate post-transcriptional modifications. By combining such advantages, DNA immunization can be expected to play more important roles in the future to elicit mAbs against difficult targets from a wide range of host systems. The current report shares our group's experience in using DNA immunization to elicit mAbs in the mouse, rabbit, and human models.

Antibody repertoire analysis of mouse immunization protocols using microfluidics and molecular genomics

Immunization of mice followed by hybridoma or B-cell screening is one of the most common antibody discovery methods used to generate therapeutic monoclonal antibody (mAb) candidates. There are a multitude of different immunization protocols that can generate an immune response in animals. However, an extensive analysis of the antibody repertoires that these alternative immunization protocols can generate has not been performed. In this study, we immunized mice that transgenically express human antibodies with either programmed cell death 1 protein or cytotoxic T-lymphocyte associated protein 4 using four different immunization protocols, and then utilized a single cell microfluidic platform to generate tissue-specific, natively paired immunoglobulin (Ig) repertoires from each method and enriched for target-specific binders using yeast single-chain variable fragment (scFv) display. We deep sequenced the scFv repertoires from both the pre-sort and post-sort libraries. All methods and both targets yielded similar oligoclonality, variable (V) and joining (J) gene usage, and divergence from germline of enriched libraries. However, there were differences between targets and/or immunization protocols for overall clonal counts, complementarity-determining region 3 (CDR3) length, and antibody/CDR3 sequence diversity. Our data suggest that, although different immunization protocols may generate a response to an antigen, performing multiple immunization protocols in parallel can yield greater Ig diversity. We conclude that modern microfluidic methods, followed by an extensive molecular genomic analysis of antibody repertoires, can be used to quickly analyze new immunization protocols or mouse platforms.

Immunogenicity and protective efficacy against Treponema pallidum in New Zealand rabbits immunized with plasmid DNA encoding flagellin

Plasmid DNA encoding flagellin FlaB3 was used as a vaccination candidate for the evaluation of immunogenicity and protection against Treponema pallidum subsp. pallidum dissemination. First, intramuscular injection of the flagellin encoded by the plasmid DNA into New Zealand rabbits elicited both humoral and cellular immune responses. Total IgG production increased in response to flagellin. In addition, serum IFN-γ secretion and CD8+ cells were substantially greater in the rabbits immunized with the plasmid encoding flagellin FlaB3 than those in the rabbits immunized with recombinant flagellin. The flagellin encoded by the plasmid DNA induced significant upregulation of serum IL-6 and IL-8 compared to that of the control rabbits. Subsequently, intradermal challenge of the vaccinated New Zealand rabbits with 1 × 10⁷T. pallidum resulted in a significant reduction of the bacterial organ burden in the blood, liver, spleen, and testicles in the flagellin plasmid DNA-vaccinated rabbits. Furthermore, the histopathological analysis demonstrated that the rabbits immunized with the plasmid DNA-encoded flagellin (FlaB3) showed better immune protection. These findings provide evidence that plasmid DNA-encoded flagellin (FlaB3) may be useful as a potential immunization route for future development of a vaccine to inhibit T. pallidum dissemination in related animals.

Innovative Immunization Strategies for Antivenom Development

Snakes, scorpions, and spiders are venomous animals that pose a threat to human health, and severe envenomings from the bites or stings of these animals must be treated with antivenom. Current antivenoms are based on plasma-derived immunoglobulins or immunoglobulin fragments from hyper-immunized animals. Although these medicines have been life-saving for more than 120 years, opportunities to improve envenoming therapy exist. In the later decades, new biotechnological tools have been applied with the aim of improving the efficacy, safety, and affordability of antivenoms. Within the avenues explored, novel immunization strategies using synthetic peptide epitopes, recombinant toxins (or toxoids), or DNA strings as immunogens have demonstrated potential for generating antivenoms with high therapeutic antibody titers and broad neutralizing capacity. Furthermore, these approaches circumvent the need for venom in the production process of antivenoms, thereby limiting some of the complications associated with animal captivity and venom collection. Finally, an important benefit of innovative immunization approaches is that they are often compatible with existing antivenom manufacturing setups. In this review, we compile all reported studies examining venom-independent innovative immunization strategies for antivenom development. In addition, a brief description of toxin families of medical relevance found in snake, scorpion, and spider venoms is presented, as well as how biochemical, bioinformatic, and omics tools could aid the development of next-generation antivenoms.

One Group's Historical Reflections on DNA Vaccine Development

DNA vaccines were pioneered by several groups in the early 1990s. This article presents the reflections of one of these groups on their work with retroviral vectors in chickens that contributed to the discovery and early development of DNA vaccines. Although the findings were initially met with skepticism, the work presented here combined with that of others founded a new method of vaccination: the direct inoculation of purified DNA encoding the target antigen.

Analysis of the effect of promoter type and skin pretreatment on antigen expression and antibody response after gene gun-based immunization

Monoclonal antibodies (mAbs) have enabled numerous basic research discoveries and therapeutic approaches for many protein classes. However, there still exist a number of target classes, such as multi-pass membrane proteins, for which antibody discovery is difficult, due in part to lack of high quality, recombinant protein. Here we describe the impact of several parameters on antigen expression and the development of mAbs against human claudin 4 (CLDN4), a potential multi-indication cancer target. Using gene gun-based DNA delivery and bioluminescence imaging, we optimize promoter type by comparing expression profiles of four robust in vivo promoters. In addition, we observe that most vectors rapidly lose expression, ultimately reaching almost background levels by three days post-delivery. Recognizing this limitation, we next explored skin pretreatment strategies as an orthogonal method to further boost the efficiency of mAb generation. We show that SDS pretreatment can boost antigen expression, but fails to significantly increase mAb discovery efficiency. In contrast, we find that sandpaper pretreatment yields 5-fold more FACS⁺ anti-CLDN4 hybridomas, without impacting antigen expression. Our findings coupled with other strategies to improve DNA immunizations should improve the success of mAb discovery against other challenging targets and enable the generation of critical research tools and therapeutic candidates.

Codon optimization and improved delivery/immunization regimen enhance the immune response against wild-type and drug-resistant HIV-1 reverse transcriptase, preserving its Th2-polarity

DNA vaccines require a considerable enhancement of immunogenicity. Here, we optimized a prototype DNA vaccine against drug-resistant HIV-1 based on a weak Th2-immunogen, HIV-1 reverse transcriptase (RT). We designed expression-optimized genes encoding inactivated wild-type and drug-resistant RTs (RT-DNAs) and introduced them into mice by intradermal injections followed by electroporation. RT-DNAs were administered as single or double primes with or without cyclic-di-GMP, or as a prime followed by boost with RT-DNA mixed with a luciferase-encoding plasmid (“surrogate challenge”). Repeated primes improved cellular responses and broadened epitope specificity. Addition of cyclic-di-GMP induced a transient increase in IFN-γ production. The strongest anti-RT immune response was achieved in a prime-boost protocol with electroporation by short 100V pulses done using penetrating electrodes. The RT-specific response, dominated by CD4+ T-cells, targeted epitopes at aa 199–220 and aa 528–543. Drug-resistance mutations disrupted the epitope at aa 205–220, while the CTL epitope at aa 202–210 was not affected. Overall, multiparametric optimization of RT strengthened its Th2- performance. A rapid loss of RT/luciferase-expressing cells in the surrogate challenge experiment revealed a lytic potential of anti-RT response. Such lytic CD4+ response would be beneficial for an HIV vaccine due to its comparative insensitivity to immune escape.

The wide utility of rabbits as models of human diseases

Studies using the European rabbit Oryctolagus cuniculus contributed to elucidating numerous fundamental aspects of antibody structure and diversification mechanisms and continue to be valuable for the development and testing of therapeutic humanized polyclonal and monoclonal antibodies. Additionally, during the last two decades, the use of the European rabbit as an animal model has been increasingly extended to many human diseases. This review documents the continuing wide utility of the rabbit as a reliable disease model for development of therapeutics and vaccines and studies of the cellular and molecular mechanisms underlying many human diseases. Examples include syphilis, tuberculosis, HIV-AIDS, acute hepatic failure and diseases caused by noroviruses, ocular herpes, and papillomaviruses. The use of rabbits for vaccine development studies, which began with Louis Pasteur’s rabies vaccine in 1881, continues today with targets that include the potentially blinding HSV-1 virus infection and HIV-AIDS. Additionally, two highly fatal viral diseases, rabbit hemorrhagic disease and myxomatosis, affect the European rabbit and provide unique models to understand co-evolution between a vertebrate host and viral pathogens.

Rabbits offer a powerful complement to rodents as a model for studying human immunology, disease pathology, and responses to infectious disease. A review from Pedro Esteves at the University of Porto, Portugal, Rose Mage of the National Institute of Allergy and Infectious Disease, Bethesda, USA and colleagues highlights some of the areas of research where rabbits offer an edge over rats and mice. Rabbits have a particularly sophisticated adaptive immune system, which could provide useful insights into human biology and produce valuable research and clinical reagents. They are also excellent models for studying - infectious diseases such as syphilis and tuberculosis, which produce pathology that closely resembles that of human patients. Rabbit-specific infections such as myxomatosis are giving researchers insights into how pathogens and hosts can shape each other’s evolution.

Generation of High-Specificity Antibodies against Membrane Proteins Using DNA-Gold Micronanoplexes for Gene Gun Immunization

Membrane proteins are the molecular interface of the cell and its environs; however, studies of membrane proteins are highly technically challenging, mainly due to instability of the isolated protein. Towards the production of antibodies that recognize properly folded and stabilized forms of membrane protein antigen, we describe a DNA-based immunization method for mice that expresses the antigen in the membranes of dendritic cells, thus allowing direct presentation to the immune system. This genetic immunization approach employs a highly efficient method of biolistic delivery based on DNA-gold micronanoplexes, which are complexes of micron-sized gold particles that allow dermal penetration and nanometer-sized gold particles that provide a higher surface area for DNA binding than micron gold alone. In contrast to antibodies derived from immunizations with detergent-solubilized protein or with protein fragments, antibodies from genetic immunization are expected to have a high capacity for binding conformational epitopes and for modulating membrane protein activity. © 2018 by John Wiley & Sons, Inc.

Prolonged in vivo expression and anti-tumor response of DNA-based anti-HER2 antibodies

Antibody gene transfer presents an appealing alternative to conventional antibody protein therapy. This pre-clinical study evaluates the impact of various parameters on the pharmacokinetics and efficacy of in vivo expressed DNA-based anti-HER2 monoclonal antibodies (mAbs), newly engineered and delivered via intramuscular electrotransfer in mice. Plasma concentrations of trastuzumab and 4D5, its murine IgG1 equivalent, peaked on average between 1–15 µg/ml, depending on the administration and configuration of the encoding plasmid DNA (pDNA). A dual expression cassette system outperformed a single 2A-based cassette, and the CAG promoter was superior to a muscle-specific ΔUSE-based promoter. A ‘gene therapy-compatible’ Gene Transport Unit (gtGTU, FIT Biotech), a plasmid backbone that co-encodes viral elements, failed to improve in vivo reporter and mAb expression compared to a conventional plasmid. In BALB/c mice, trastuzumab detection was lost within two weeks after pDNA administration due to anti-drug antibodies. This host immune response was addressed by expressing trastuzumab in immune-compromised mice, or by gene transfer of murine 4D5 in BALB/c mice. Both approaches maintained single-digit µg/ml mAb concentrations for at least six to nine months, and allowed to boost mAb expression over time by pDNA re-dosing. In a breast cancer mouse model, prophylactic and therapeutic DNA-based trastuzumab or 4D5 led to complete tumor regressions, thereby rivalling with the administration of milligrams of mAb protein. In conclusion, our study demonstrates proof of concept for antibody gene transfer in cancer, provides critical insights in the engineering and application of DNA-based antibodies, and serves to advance this modality in oncology and beyond.

Rapid and Low-Cost Tools Derived from Plants to Face Emerging/Re-emerging Infectious Diseases and Bioterrorism Agents

Whether naturally occurring or man-made, biological threats pose a severe risk in an increasingly globalized world.

The dual-use nature of biological research, with its most recent advances in biotechnology (‘synthetic biology’, gene editing, nanotechnologies etc.) and the rapid diffusion of knowledge, raise proliferation concerns of biological weapons by non-state actors.

Thus, there is an urgent need to develop measures intended to enhance diagnostic, prophylactic and therapeutic capabilities and capacities to improve the ability of society to combat infectious diseases outbreaks, as well as to alleviate the effects of bioterrorism attacks.

We present here two examples of biotechnology usage for biodefence purposes: (i) plants as biofactories for the rapid production of improved biopharmaceuticals (‘Plant Molecular Farming’), and (ii) plant sequences as immune-modulating agents to enhance the efficacy of genetic vaccines.

These platforms represent two promising (and complementary) approaches for the rapid and low-cost production of countermeasures (diagnostics and vaccine candidates) against emerging, re-emerging and bioterrorism-related infections.

Evaluation of Immune Responses Induced by GRA7 and ROP2 Genes by DNA Vaccine Cocktails Against Acute Toxoplasmosis in BALB/c Mice

BACKGROUND

The severe damages of toxoplasmosis clearly indicate the need for the development of a more effective vaccine. Immunization with plasmid DNA is a promising vaccination technique. Therefore, GRA7 plasmid was prepared to be used as a vaccine. The purpose of this study was evaluation of immunization with cocktail DNA vaccine including plasmids encoding Toxoplasma gondii ROP2 and GRA7 in BALB/c mice.

METHODS

In this study, 733 bp of GRA7 gene was cloned in pCDNA3.1 plasmid as an expression vector. The plasmids containing GRA7 and ROP2 genes were administered via IM according to immunized mice three times with a 3 week interval. For lymphocyte proliferation and cytokine assay, splenocytes of immunized mice were cultured for proliferation and cytokine assay. The other mice in each group were inoculated by the parasite and mortality of the mice was evaluated on a daily basis.

RESULTS

The cytokine assay results and lymphocyte proliferation response in cocktail DNA vaccines showed that IFN-γ levels were significantly higher than controls (p<0.05), whereas IL-4 expression level in BALB/c mice immunized with cocktail was lower than that in control groups and these results are confirmed by MTT test. Predominance of the levels of IgG2a over IgG1 was observed in sera of the immunized mice. Furthermore, IgG2a values in cocktail DNA vaccines pcGRA7 were significantly higher than control group (p<0.01). In contrast, IgG1 antibodies were similar between the two groups (p>0.5). So, survival time in the immune groups was significantly prolonged in comparison to control ones (p<0.01).

CONCLUSION

The immunized mice by DNA vaccine produce higher titration of IFNγ, indicated with Th1 response which is confirmed by high level of IgG2a. These data demonstrate that the cocktail GRA7/ROP2 is a potential vaccine candidate against toxoplasmosis.

Camelid Single-Domain Antibodies: Historical Perspective and Future Outlook

Tremendous effort has been expended over the past two and a half decades to understand many aspects of camelid heavy chain antibodies, from their biology, evolution, and immunogenetics to their potential applications in various fields of research and medicine. In this article, I present a historical perspective on the development of camelid single-domain antibodies (sdAbs or V_HHs, also widely known as nanobodies) since their discovery and discuss the advantages and disadvantages of these unique molecules in various areas of research, industry, and medicine. Commercialization of camelid sdAbs exploded in 2001 with a flurry of patents issued to the Vrije Universiteit Brussel (VUB) and later taken on by the Vlaams Interuniversitair Instituut voor Biotechnologie (VIB) and, after 2002, the VIB-founded spin-off company, Ablynx. While entrepreneurial spirit has certainly catalyzed the exploration of nanobodies as marketable products, IP restrictions may be partially responsible for the relatively long time span between the discovery of these biomolecules and their entry into the pharmaceutical market. It is now anticipated that the first V_HH-based antibody drug, Caplacizumab, a bivalent anti-vWF antibody for treating rare blood clotting disorders, may be approved and commercialized in 2018 or shortly thereafter. This elusive first approval, along with the expiry of key patents, may substantially alter the scientific and biomedical landscape surrounding camelid sdAbs and pave the way for their emergence as mainstream biotherapeutics.

Characterization of Monoclonal Antibodies against HA Protein of H1N1 Swine Influenza Virus and Protective Efficacy against H1 Viruses in Mice

H1N1 swine influenza viruses (SIV) are prevalent in pigs globally, and occasionally emerge in humans, which raises concern about their pandemic threats. To stimulate hemagglutination (HA) of A/Swine/Guangdong/LM/2004 (H1N1) (SW/GD/04) antibody response, eukaryotic expression plasmid pCI-neo-HA was constructed and used as an immunogen to prepare monoclonal antibodies (mAbs). Five mAbs (designed 8C4, 8C6, 9D6, 8A4, and 8B1) against HA protein were obtained and characterized. Western blot showed that the 70 kDa HA protein could be detected by all mAbs in MDCK cells infected with SW/GD/04. Three mAbs—8C4, 8C6, and 9D6—have hemagglutination inhibition (HI) and neutralization test (NT) activities, and 8C6 induces the highest HI and NT titers. The protection efficacy of 8C6 was investigated in BALB/c mice challenged with homologous or heterologous strains of the H1 subtype SIV. The results indicate that mAb 8C6 protected the mice from viral infections, especially the homologous strain, which was clearly demonstrated by the body weight changes and reduction of viral load. Thus, our findings document for the first time that mAb 8C6 might be of potential therapeutic value for H1 subtype SIV infection.

Opportunities for therapeutic antibodies directed at G-protein-coupled receptors

G-protein-coupled receptors (GPCRs) are activated by a diverse range of ligands, from large proteins and proteases to small peptides, metabolites, neurotransmitters and ions. They are expressed on all cells in the body and have key roles in physiology and homeostasis. As such, GPCRs are one of the most important target classes for therapeutic drug discovery. The development of drugs targeting GPCRs has therapeutic value across a wide range of diseases, including cancer, immune and inflammatory disorders as well as neurological and metabolic diseases. The progress made by targeting GPCRs with antibody-based therapeutics, as well as technical hurdles to overcome, are presented and discussed in this Review. Antibody therapeutics targeting C-C chemokine receptor type 4 (CCR4), CCR5 and calcitonin gene-related peptide (CGRP) are used as illustrative clinical case studies.

Generation and Characterization of Inhibitory Antibodies Specific to Guinea Pig CXCR1 and CXCR2

CXCR1 and CXCR2 are chemokine receptors that have different selectivity of chemokine ligands, but the distinct role of each receptor is not clearly understood. This is due to the absence of specific inhibitors in guinea pigs, which are the appropriate species for investigation of CXCR1 and CXCR2 because of their functional similarity to humans. In this study, we generated and evaluated monoclonal antibodies that specifically bound to guinea pig CXCR1 (gpCXCR1) and guinea pig CXCR2 (gpCXCR2) for acquisition of specific inhibitors. To assess the activity of antibodies, we established CHO-K1 cells stably expressing either gpCXCR1 or gpCXCR2 (CHO/gpCXCR1 or CHO/gpCXCR2). CHO/gpCXCR1 showed migration in response to guinea pig interleukin (IL)-8, and CHO/gpCXCR2 showed migration in response to both guinea pig IL-8 and guinea pig growth-regulated oncogene α. The receptor selectivities of the chemokines of guinea pigs were the same as the human orthologs. The inhibitory activities of the anti-gpCXCR1 and anti-gpCXCR2 monoclonal antibodies on cell migration were observed in a concentration-dependent manner. In conclusion, we successfully obtained inhibitory antibodies specific to gpCXCR1 and gpCXCR2. These inhibitory antibodies will be useful to clarify the physiological roles of CXCR1 and CXCR2 in guinea pigs.