Nanobodies with cross-neutralizing activity provide prominent therapeutic efficacy in mild and severe COVID-19 rodent models.

The weakened protective efficacy of COVID-19 vaccines and antibodies caused by SARS-CoV-2 variants presents a global health emergency, which underscores the urgent need for universal therapeutic antibody intervention for clinical patients. Here, we screened three alpacas-derived nanobodies (Nbs) with neutralizing activity from twenty RBD-specific Nbs. The three Nbs were fused with the Fc domain of human IgG, namely aVHH-11-Fc, aVHH-13-Fc and aVHH-14-Fc, which could specifically bind RBD protein and competitively inhibit the binding of ACE2 receptor to RBD. They effectively neutralized SARS-CoV-2 pseudoviruses D614G, Alpha, Beta, Gamma, Delta, and Omicron sub-lineages BA.1, BA.2, BA.4, and BA.5 and authentic SARS-CoV-2 prototype, Delta, and Omicron BA.1, BA.2 strains. In mice-adapted COVID-19 severe model, intranasal administration of aVHH-11-Fc, aVHH-13-Fc and aVHH-14-Fc effectively protected mice from lethal challenges and reduced viral loads in both the upper and lower respiratory tracts. In the COVID-19 mild model, aVHH-13-Fc, which represents the optimal neutralizing activity among the above three Nbs, effectively protected hamsters from the challenge of SARS-CoV-2 prototype, Delta, Omicron BA.1 and BA.2 by significantly reducing viral replication and pathological alterations in the lungs. In structural modeling of aVHH-13 and RBD, aVHH-13 binds to the receptor-binding motif region of RBD and interacts with some highly conserved epitopes. Taken together, our study illustrated that alpaca-derived Nbs offered a therapeutic countermeasure against SARS-CoV-2, including those Delta and Omicron variants which have evolved into global pandemic strains.

Structural and Computational Studies of the SARS-CoV-2 Spike Protein Binding Mechanisms with Nanobodies: From Structure and Dynamics to Avidity-Driven Nanobody Engineering.

Nanobodies provide important advantages over traditional antibodies, including their smaller size and robust biochemical properties such as high thermal stability, high solubility, and the ability to be bioengineered into novel multivalent, multi-specific, and high-affinity molecules, making them a class of emerging powerful therapies against SARS-CoV-2. Recent research efforts on the design, protein engineering, and structure-functional characterization of nanobodies and their binding with SARS-CoV-2 S proteins reflected a growing realization that nanobody combinations can exploit distinct binding epitopes and leverage the intrinsic plasticity of the conformational landscape for the SARS-CoV-2 S protein to produce efficient neutralizing and mutation resistant characteristics. Structural and computational studies have also been instrumental in quantifying the structure, dynamics, and energetics of the SARS-CoV-2 spike protein binding with nanobodies. In this review, a comprehensive analysis of the current structural, biophysical, and computational biology investigations of SARS-CoV-2 S proteins and their complexes with distinct classes of nanobodies targeting different binding sites is presented. The analysis of computational studies is supplemented by an in-depth examination of mutational scanning simulations and identification of binding energy hotspots for distinct nanobody classes. The review is focused on the analysis of mechanisms underlying synergistic binding of multivalent nanobodies that can be superior to single nanobodies and conventional nanobody cocktails in combating escape mutations by effectively leveraging binding avidity and allosteric cooperativity. We discuss how structural insights and protein engineering approaches together with computational biology tools can aid in the rational design of synergistic combinations that exhibit superior binding and neutralization characteristics owing to avidity-mediated mechanisms.

A Methodological Approach Using rAAV Vectors Encoding Nanobody-Based Biologics to Evaluate ARTC2.2 and P2X7 In Vivo.

On murine T cells, mono-ADP ribosyltransferase ARTC2.2 catalyzes ADP-ribosylation of various surface proteins when nicotinamide adenine dinucleotide (NAD+) is released into the extracellular compartment. Covalent ADP-ribosylation of the P2X7 receptor by ARTC2.2 thereby represents an additional mechanism of activation, complementary to its triggering by extracellular ATP. P2X7 is a multifaceted receptor that may represents a potential target in inflammatory, and neurodegenerative diseases, as well as in cancer. We present herein an experimental approach using intramuscular injection of recombinant AAV vectors (rAAV) encoding nanobody-based biologics targeting ARTC2.2 or P2X7. We demonstrate the ability of these in vivo generated biologics to potently and durably block P2X7 or ARTC2.2 activities in vivo, or in contrast, to potentiate NAD+- or ATP-induced activation of P2X7. We additionally demonstrate the ability of rAAV-encoded functional heavy chain antibodies to elicit long-term depletion of T cells expressing high levels of ARTC2.2 or P2X7. Our approach of using rAAV to generate functional nanobody-based biologics in vivo appears promising to evaluate the role of ARTC2.2 and P2X7 in murine acute as well as chronic disease models.

A Dual Target-Directed Single Domain-Based Fusion Protein Against Interleukin-6 Receptor Decelerate Experimental Arthritis Progression Via Modulating JNK Expression.

The currently used anti-cytokine therapeutic antibodies cannot selectively neutralize pathogenic cytokine signalling that cause collateral damage to protective signalling cascades. The single domain chain firstly discovered in Camelidae displays fully functional ability in antigen-binding against variable targets, which has been seemed as attractive candidates for the next-generation biologic drug study. In this study, we established a simple prokaryotic expression system for a dual target-directed single domain-based fusion protein against the interleukin-6 receptor and human serum, albumin, the recombinant anti-IL-6R fusion protein (VHH-0031). VHH-0031 exhibited potent anti-inflammatory effects produced by LPS on cell RAW264.7, where the major cytokines and NO production were downregulated after 24 h incubation with VHH-0031 in a dose-dependent manner. In vivo, VHH-0031 presented significant effects on the degree reduction of joint swelling in the adjuvant-induced arthritis (AIA) rat, having a healthier appearance compared with the dexamethasone. The expression level of JNK protein in the VHH-0031 group was significantly decreased, demonstrating that VHH-0031 provides a low-cost and desirable effect in the treatment of more widely patients.

Phenotypic Lentivirus Screens to Identify Antiviral Single Domain Antibodies.

Our understanding of infection biology is based on experiments in which pathogen or host proteins are perturbed by small compound inhibitors, mutation, or depletion. This approach has been remarkably successful, as, for example, demonstrated by the independent identification of the endosomal membrane protein Niemann-Pick C1 as an essential factor for Ebola virus infection in both small compound and insertional mutagenesis screens (Côté, Nature 477:344-348, 2011; Carette et al., Nature 477:340-343, 2011). However, many aspects of host-pathogen interactions are poorly understood because we cannot target all of the involved molecules with small molecules, or because we cannot deplete essential proteins. Single domain antibody fragments expressed in the cytosol or other organelles constitute a versatile alternative to perturb the function of any given protein by masking protein-protein interaction interfaces, by stabilizing distinct conformations, or by directly interfering with enzymatic activities. The variable domains of heavy chain-only antibodies (VHHs) from camelid species can be cloned from blood samples of animals immunized with the desired target molecules. We can thus exploit the ability of the camelid immune system to generate affinity-matured single domain antibody fragments to obtain highly specific tools. Interesting VHH candidates are typically identified based on their affinity toward immobilized antigens using techniques such as phage display.The phenotypical screening approach described here allows the direct identification of VHHs that prevent infection of cells with influenza A virus (IAV) or other pathogens. The VHH repertoire is cloned into a lentiviral vector, which is used to generate pseudo-typed lentivirus particles. Target cells are transduced with the lentivirus, so that every cell inducibly expresses a different VHH. This cell collection is then challenged with a lethal dose of virus. Only the cells which express a VHH that prevents infection by targeting virus proteins or host cell components essential for infection will survive. We can thus identify critical target molecules including vulnerable epitopes and conformations, render target molecules accessible to informative perturbation studies, and stabilize intermediates of virus entry for detailed analysis.

Camelid Single-Domain Antibodies (VHHs) against Crotoxin: A Basis for Developing Modular Building Blocks for the Enhancement of Treatment or Diagnosis of Crotalic Envenoming.

Toxic effects triggered by crotalic envenoming are mainly related to crotoxin (CTX), composed of a phospholipase A2 (CB) and a subunit with no toxic activity (CA). Camelids produce immunoglobulins G devoid of light chains, in which the antigen recognition domain is called VHH. Given their unique characteristics, VHHs were selected using Phage Display against CTX from Crotalus durissus terrificus. After three rounds of biopanning, four sequence profiles for CB (KF498602, KF498603, KF498604, and KF498605) and one for CA (KF498606) were revealed. All clones presented the VHH hallmark in FR2 and a long CDR3, with the exception of KF498606. After expressing pET22b-VHHs in E. coli, approximately 2 to 6 mg of protein per liter of culture were obtained. When tested for cross-reactivity, VHHs presented specificity for the Crotalus genus and were capable of recognizing CB through Western blot. KF498602 and KF498604 showed thermostability, and displayed affinity constants for CTX in the micro or nanomolar range. They inhibited in vitro CTX PLA2 activity, and CB cytotoxicity. Furthermore, KF498604 inhibited the CTX-induced myotoxicity in mice by 78.8%. Molecular docking revealed that KF498604 interacts with the CA–CB interface of CTX, seeming to block substrate access. Selected VHHs may be alternatives for the crotalic envenoming treatment.

Novel nanoscale bacteriophage-based single-domain antibodies for the therapy of systemic infection caused by Candida albicans.

Candida albicans (C. albicans) is an important human commensal and opportunistic fungal pathogen. Secreted aspartyl proteinases (Saps) are a major virulence trait of C. albicans, and among these proteases Sap2 has the highest expression levels. It is possible that antibodies against Sap2 could provide an antifungal effect. In this study, two phages displaying anti-rSap2 single chain variable fragments (scFvs) were screened from human single fold scFv libraries, and their potential therapeutic roles were evaluated using a murine model infected by C. albicans. The in vivo efficacies were assessed by mortality rates, fungal burden and histological examination. Overall survival rates were significantly increased while the colony counts and infectious foci were significantly decreased after treatment with the scFv-phages relative to the control groups. In order to investigate the immune response provoked by scFv-phages, three kinds of cytokines (Th1, Th2 and Th17 types) were measured and a clear immune response was observed. These findings suggest that anti-rSap2 scFv-phages have potential in the therapy of systemic infection caused by C. albicans.

Camelid single-domain antibody fragments: Uses and prospects to investigate protein misfolding and aggregation, and to treat diseases associated with these phenomena.

The deposition of misfolded peptides and proteins in the form of amyloid fibrils is the hallmark of nearly fifty medical disorders, including Alzheimer's disease, Parkinson's disease, prion diseases and type II diabetes. These disorders, referred to as amyloidoses, generally become apparent late in life. Their psycho-sociological and economic incidence in western societies will be therefore considerable in the coming decades due to the ageing of the population. Neither preventing nor curative treatments are available yet. These disorders constitute therefore a medical challenge of great importance. Thus, an extensive research is being carried out to understand, at the molecular level, (i) how amyloidogenic proteins misfold and convert from their soluble form into amyloid fibrils, and (ii) how these aggregates or some of their oligomeric precursor species are toxic. The formation of amyloid fibrils proceeds through a complex nucleation/polymerisation mechanism with the formation of various species, including small oligomers. In this review, we focus on how VHHs or nanobodies, the antigen-binding domains of camelid heavy-chain antibodies, are being increasingly used to characterise each of the species formed on the pathway of fibril formation in terms of structure, stability, kinetics of formation and toxicity. We first introduce the characteristic features of nanobodies compared to those of conventional antibody fragments. Thereafter, we discuss how nanobodies, due to their unique properties, are used as probes to dissect the molecular mechanisms of misfolding and aggregation of six proteins associated with diseases, i.e. human lysozyme, ß2-microglobulin, α-synuclein, prion, polyadenylate binding protein nuclear 1 and amyloid ß-peptide. A brief general presentation of each disease and the associated peptide/protein is also provided. In addition, we discuss how nanobodies could be used as early diagnostic tools and as novel strategies to treat diseases associated with protein misfolding and aggregation.