Adenoviral Expression of a Bispecific VHH-Based Neutralizing Agent That Targets Protective Antigen Provides Prophylactic Protection from Anthrax in Mice

Food-Borne Biotoxin Neutralization in Vivo by Nanobodies: Current Status and Prospects

Food-borne biotoxins from microbes, plants, or animals contaminate unclean, spoiled, and rotten foods, posing significant health risks. Neutralizing such toxins is vital for human health, especially after food poisoning. Nanobodies (Nbs), a type of single-domain antibodies derived from the genetic cloning of a variable domain of heavy chain antibodies (VHHs) in camels, offer unique advantages in toxin neutralization. Their small size, high stability, and precise binding enable effective neutralization. The use of Nbs in neutralizing food-borne biotoxins offers numerous benefits, and their genetic malleability allows tailored optimization for diverse toxins. As nanotechnology continues to evolve and improve, Nbs are poised to become increasingly efficient and safer tools for toxin neutralization, playing a pivotal role in safeguarding human health and environmental safety. This review not only highlights the efficacy of these agents in neutralizing toxins but also proposes innovative solutions to address their current challenges. It lays a solid foundation for their further development in this crucial field and propels their commercial application, thereby contributing significantly to advancements in this domain.

Nanobodies: the Potential Application in Bacterial Treatment and Diagnosis

An infection caused by bacteria is one of the main factors that poses a threat to human health. A recent report from the World Health Organization (WHO) has highlighted that bacteria that cause blood infections have become increasingly drug-resistant. Therefore, it is crucial to research and develop new techniques for detecting and treating these infections. Since their discovery, nanobodies have exhibited numerous outstanding biological properties. They are easy to express, modify, and have high stability, robust permeability and low immunogenicity, all of which indicate their potential as a substitute. Nanobodies have been utilized in a variety of studies on viruses and cancer. This article primarily focuses on nanobodies and introduces their characteristics and application in the diagnosis and treatment of bacterial infections.

Single Domain Antibody application in bacterial infection diagnosis and neutralization

Increasing antibiotic resistance to bacterial infections causes a serious threat to human health. Efficient detection and treatment strategies are the keys to preventing and reducing bacterial infections. Due to the high affinity and antigen specificity, antibodies have become an important tool for diagnosis and treatment of various human diseases. In addition to conventional antibodies, a unique class of “heavy-chain-only” antibodies (HCAbs) were found in the serum of camelids and sharks. HCAbs binds to the antigen through only one variable domain Referred to as VHH (variable domain of the heavy chain of HCAbs). The recombinant format of the VHH is also called single domain antibody (sdAb) or nanobody (Nb). Sharks might also have an ancestor HCAb from where SdAbs or V-NAR might be engineered. Compared with traditional Abs, Nbs have several outstanding properties such as small size, high stability, strong antigen-binding affinity, high solubility and low immunogenicity. Furthermore, they are expressed at low cost in microorganisms and amenable to engineering. These superior properties make Nbs a highly desired alternative to conventional antibodies, which are extensively employed in structural biology, unravelling biochemical mechanisms, molecular imaging, diagnosis and treatment of diseases. In this review, we summarized recent progress of nanobody-based approaches in diagnosis and neutralization of bacterial infection and further discussed the challenges of Nbs in these fields.

Research Progress and Applications of Multivalent, Multispecific and Modified Nanobodies for Disease Treatment

Recombinant antibodies such as nanobodies are progressively demonstrating to be a valid alternative to conventional monoclonal antibodies also for clinical applications. Furthermore, they do not solely represent a substitute for monoclonal antibodies but their unique features allow expanding the applications of biotherapeutics and changes the pattern of disease treatment. Nanobodies possess the double advantage of being small and simple to engineer. This combination has promoted extremely diversified approaches to design nanobody-based constructs suitable for particular applications. Both the format geometry possibilities and the functionalization strategies have been widely explored to provide macromolecules with better efficacy with respect to single nanobodies or their combination. Nanobody multimers and nanobody-derived reagents were developed to image and contrast several cancer diseases and have shown their effectiveness in animal models. Their capacity to block more independent signaling pathways simultaneously is considered a critical advantage to avoid tumor resistance, whereas the mass of these multimeric compounds still remains significantly smaller than that of an IgG, enabling deeper penetration in solid tumors. When applied to CAR-T cell therapy, nanobodies can effectively improve the specificity by targeting multiple epitopes and consequently reduce the side effects. This represents a great potential in treating malignant lymphomas, acute myeloid leukemia, acute lymphoblastic leukemia, multiple myeloma and solid tumors. Apart from cancer treatment, multispecific drugs and imaging reagents built with nanobody blocks have demonstrated their value also for detecting and tackling neurodegenerative, autoimmune, metabolic, and infectious diseases and as antidotes for toxins. In particular, multi-paratopic nanobody-based constructs have been developed recently as drugs for passive immunization against SARS-CoV-2 with the goal of impairing variant survival due to resistance to antibodies targeting single epitopes. Given the enormous research activity in the field, it can be expected that more and more multimeric nanobody molecules will undergo late clinical trials in the next future. Systematic Review Registration.

Synthetic biology: at the crossroads of genetic engineering and human therapeutics-a Keystone Symposia report

Synthetic biology has the potential to transform cell- and gene-based therapies for a variety of diseases. Sophisticated tools are now available for both eukaryotic and prokaryotic cells to engineer cells to selectively achieve therapeutic effects in response to one or more disease-related signals, thus sparing healthy tissue from potentially cytotoxic effects. This report summarizes the Keystone eSymposium "Synthetic Biology: At the Crossroads of Genetic Engineering and Human Therapeutics," which took place on May 3 and 4, 2021. Given that several therapies engineered using synthetic biology have entered clinical trials, there was a clear need for a synthetic biology symposium that emphasizes the therapeutic applications of synthetic biology as opposed to the technical aspects. Presenters discussed the use of synthetic biology to improve T cell, gene, and viral therapies, to engineer probiotics, and to expand upon existing modalities and functions of cell-based therapies.

DNA-based delivery of anti-DR5 Nanobodies improves exposure and anti-tumor efficacy over protein-based administration

Nanobodies present an appealing class of potential cancer therapeutics. The current study explores the in vivo expression of these molecules through DNA-encoded delivery. We hypothesized that this approach could address the rapid clearance of Nanobodies and, through half-life modulation, increase the produced levels in circulation. We therefore evaluated pharmacokinetics and efficacy of variants of an anti-death receptor 5 Nanobody (NbDR5), either monovalent or multivalent with half-life extension properties, after DNA-based administration. Intramuscular electrotransfer of a monovalent NbDR5-encoding plasmid (pNbDR5) did not result in detectable plasma levels in BALB/c mice. A tetravalent NbDR5-encoding plasmid (pNbDR5₄) provided peak concentrations of 54 ng/mL, which remained above 24 ng/mL during a 12-week follow-up. DNA-based delivery of these Nanobody formats fused to a Nanobody binding to serum albumin (NbSA), pNbDR5-NbSA and pNbDR5₄-NbSA, resulted in significantly higher plasma levels, with peak titers of 5.2 and 7.7 µg/mL, respectively. In an athymic-nude mice COLO 205 colon-cancer model, a quadrupled intramuscular DNA dose led to peak plasma levels of 270 ng/mL for pNbDR5₄ and 38 µg/mL for pNbDR5₄-NbSA. Potent anti-tumor responses were only observed for pNbDR5₄, following either intramuscular or intratumoral delivery. Despite comparable in vitro activity and superior plasma exposure, NbDR5₄-NbSA was less effective than NbDR5₄ in vivo, regardless of whether delivered as DNA or protein. Overall, DNA-based Nanobody delivery resulted in more potent and durable anti-tumor responses than protein-based Nanobody delivery. In conclusion, this study demonstrates pre-clinical proof of concept for DNA-based Nanobodies in oncology and highlights the improved outcome over conventional protein administration.

Use of camel single-domain antibodies for the diagnosis and treatment of zoonotic diseases

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VHHs provide many advantages over complete IgG in diagnostics and therapy.

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Toxins and viruses are more efficiently neutralized by multivalent VHHs.

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Camelids could be a source of broadly neutralizing antibodies (bNAbs) to treat zoonotic diseases.

Camelids produce both conventional heterotetrameric antibodies and homodimeric heavy-chain only antibodies. The antigen-binding region of such homodimeric heavy-chain only antibodies consists of one single domain, called VHH. VHHs provide many advantages over conventional full-sized antibodies and currently used antibody-based fragments (Fab, scFv), including high specificity, stability and solubility, and small size, allowing them to recognize unusual antigenic sites and deeply penetrate tissues. Since their discovery, VHHs have been used extensively in diagnostics and therapy. In recent decades, the number of outbreaks of diseases transmissible from animals to humans has been on the rise. In this review, we evaluate the status of VHHs as diagnostic and therapeutic biomolecular agents for the detection and treatment of zoonotic diseases, such as bacterial, parasitic, and viral zoonosis. VHHs show great adaptability to inhibit or neutralize pathogenic agents for the creation of multifunctional VHH-based diagnostic and therapeutic molecules against zoonotic diseases.

Why Is Eradicating Typhoid Fever So Challenging: Implications for Vaccine and Therapeutic Design

Salmonella enterica serovar Typhi (S. Typhi) and S. Paratyphi, namely typhoidal Salmonellae, are the cause of (para) typhoid fever, which is a devastating systemic infectious disease in humans. In addition, the spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) S. Typhi in many low and middle-income countries poses a significant risk to human health. While currently available typhoid vaccines and therapeutics are efficacious, they have some limitations. One important limitation is the lack of controlling individuals who chronically carry S. Typhi. However, due to the strict host specificity of S. Typhi to humans, S. Typhi research is hampered. As a result, our understanding of S. Typhi pathogenesis is incomplete, thereby delaying the development and improvement of prevention and treatment strategies. Nonetheless, to better combat and contain S. Typhi, it is vital to develop a vaccine and therapy for controlling both acutely and chronically infected individuals. This review discusses how scientists are trying to combat typhoid fever, why it is so challenging to do so, which approaches show promise, and what we know about the pathogenesis of S. Typhi chronic infection.

Genetic Modification of the Lung Directed Toward Treatment of Human Disease

Genetic modification therapy is a promising therapeutic strategy for many diseases of the lung intractable to other treatments. Lung gene therapy has been the subject of numerous preclinical animal experiments and human clinical trials, for targets including genetic diseases such as cystic fibrosis and α1-antitrypsin deficiency, complex disorders such as asthma, allergy, and lung cancer, infections such as respiratory syncytial virus (RSV) and Pseudomonas, as well as pulmonary arterial hypertension, transplant rejection, and lung injury. A variety of viral and non-viral vectors have been employed to overcome the many physical barriers to gene transfer imposed by lung anatomy and natural defenses. Beyond the treatment of lung diseases, the lung has the potential to be used as a metabolic factory for generating proteins for delivery to the circulation for treatment of systemic diseases. Although much has been learned through a myriad of experiments about the development of genetic modification of the lung, more work is still needed to improve the delivery vehicles and to overcome challenges such as entry barriers, persistent expression, specific cell targeting, and circumventing host anti-vector responses.

State of play and clinical prospects of antibody gene transfer

Recombinant monoclonal antibodies (mAbs) are one of today's most successful therapeutic classes in inflammatory diseases and oncology. A wider accessibility and implementation, however, is hampered by the high product cost and prolonged need for frequent administration. The surge in more effective mAb combination therapies further adds to the costs and risk of toxicity. To address these issues, antibody gene transfer seeks to administer to patients the mAb-encoding nucleotide sequence, rather than the mAb protein. This allows the body to produce its own medicine in a cost- and labor-effective manner, for a prolonged period of time. Expressed mAbs can be secreted systemically or locally, depending on the production site. The current review outlines the state of play and clinical prospects of antibody gene transfer, thereby highlighting recent innovations, opportunities and remaining hurdles. Different expression platforms and a multitude of administration sites have been pursued. Viral vector-mediated mAb expression thereby made the most significant strides. Therapeutic proof of concept has been demonstrated in mice and non-human primates, and intramuscular vectored mAb therapy is under clinical evaluation. However, viral vectors face limitations, particularly in terms of immunogenicity. In recent years, naked DNA has gained ground as an alternative. Attained serum mAb titers in mice, however, remain far below those obtained with viral vectors, and robust pharmacokinetic data in larger animals is limited. The broad translatability of DNA-based antibody therapy remains uncertain, despite ongoing evaluation in patients. RNA presents another emerging platform for antibody gene transfer. Early reports in mice show that mRNA may be able to rival with viral vectors in terms of generated serum mAb titers, although expression appears more short-lived. Overall, substantial progress has been made in the clinical translation of antibody gene transfer. While challenges persist, clinical prospects are amplified by ongoing innovations and the versatility of antibody gene transfer. Clinical introduction can be expedited by selecting the platform approach currently best suited for the mAb or disease of interest. Innovations in expression platform, administration and antibody technology are expected to further improve overall safety and efficacy, and unlock the vast clinical potential of antibody gene transfer.

A Tetraspecific VHH-Based Neutralizing Antibody Modifies Disease Outcome in Three Animal Models of Clostridium difficile Infection

Clostridium difficile infection (CDI), a leading cause of nosocomial infection, is a serious disease in North America, Europe, and Asia. CDI varies greatly from asymptomatic carriage to life-threatening diarrhea, toxic megacolon, and toxemia. The incidence of community-acquired infection has increased due to the emergence of hypervirulent antibiotic-resistant strains. These new strains contribute to the frequent occurrence of disease relapse, complicating treatment, increasing hospital stays, and increasing morbidity and mortality among patients. Therefore, it is critical to develop new therapeutic approaches that bypass the development of antimicrobial resistance and avoid disruption of gut microflora. Here, we describe the construction of a single heteromultimeric VHH-based neutralizing agent (VNA) that targets the two primary virulence factors of Clostridium difficile, toxins A (TcdA) and B (TcdB). Designated VNA2-Tcd, this agent has subnanomolar toxin neutralization potencies for both C. difficile toxins in cell assays. When given systemically by parenteral administration, VNA2-Tcd protected against CDI in gnotobiotic piglets and mice and to a lesser extent in hamsters. Protection from CDI was also observed in gnotobiotic piglets treated by gene therapy with an adenovirus that promoted the expression of VNA2-Tcd.

A Diverse Set of Single-domain Antibodies (VHHs) against the Anthrax Toxin Lethal and Edema Factors Provides a Basis for Construction of a Bispecific Agent That Protects against Anthrax Infection

Infection with Bacillus anthracis, the causative agent of anthrax, can lead to persistence of lethal secreted toxins in the bloodstream, even after antibiotic treatment. VHH single-domain antibodies have been demonstrated to neutralize diverse bacterial toxins both in vitro and in vivo, with protein properties such as small size and high stability that make them attractive therapeutic candidates. Recently, we reported on VHHs with in vivo activity against the protective antigen component of the anthrax toxins. Here, we characterized a new set of 15 VHHs against the anthrax toxins that act by binding to the edema factor (EF) and/or lethal factor (LF) components. Six of these VHHs are cross-reactive against both EF and LF and recognize the N-terminal domain (LF_N, EF_N) of their target(s) with subnanomolar affinity. The cross-reactive VHHs block binding of EF/LF to the protective antigen C-terminal binding interface, preventing toxin entry into the cell. Another VHH appears to recognize the LF C-terminal domain and exhibits a kinetic effect on substrate cleavage by LF. A subset of the VHHs neutralized against EF and/or LF in murine macrophage assays, and the neutralizing VHHs that were tested improved survival of mice in a spore model of anthrax infection. Finally, a bispecific VNA (VHH-based neutralizing agent) consisting of two linked toxin-neutralizing VHHs, JMN-D10 and JMO-G1, was fully protective against lethal anthrax spore infection in mice as a single dose. This set of VHHs should facilitate development of new therapeutic VNAs and/or diagnostic agents for anthrax.

A Bispecific Antibody Promotes Aggregation of Ricin Toxin on Cell Surfaces and Alters Dynamics of Toxin Internalization and Trafficking

JJX12 is an engineered bispecific antibody against ricin, a member of the medically important A-B family of toxins that exploits retrograde transport as means to gain entry into the cytosol of target cells. JJX12 consists of RTA-D10, a camelid single variable domain (VHH) antibody directed against an epitope on ricin's enzymatic subunit (RTA), linked via a 15-mer peptide to RTB-B7, a VHH against ricin's bivalent galactose binding subunit (RTB). We previously reported that JJX12, but not an equimolar mixture of RTA-D10 and RTB-B7 monomers, was able to passively protect mice against a lethal dose ricin challenge, demonstrating that physically linking RTB-B7 and RTA-D10 is critical for toxin-neutralizing activity in vivo. We also reported that JJX12 promotes aggregation of ricin in solution, presumably through the formation of intermolecular crosslinking. In the current study, we now present evidence that JJX12 affects the dynamics of ricin uptake and trafficking in human epithelial cells. Confocal microscopy, as well as live cell imaging coupled with endocytosis pathway-specific inhibitors, revealed that JJX12-toxin complexes are formed on the surfaces of mammalian cells and internalized via a pathway sensitive to amiloride, a known inhibitor of macropinocytosis. Moreover, in the presence of JJX12, retrograde transport of ricin to the trans-Golgi network was significantly reduced, while accumulation of the toxin in late endosomes was significantly enhanced. In summary, we propose that JJX12, by virtue of its ability to crosslink ricin toxin, alters the route of toxin uptake and trafficking within cells.