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ABSTRACT Background Methods Results Conclusions Diagnosis of allergies is mostly based on the patient's clinical history and allergen provocation tests. Determination of specific IgE (sIgE) profiles can be performed to support allergy diagnosis. This is commonly done in vivo by the skin prick test or in vitro with automated systems. Several platforms exist to quantify sIgE levels, but all these methods require access to specific instruments, often delaying the test's results. The IgE luciferase‐linked immunosorbent assay (LuLISA) allows bioluminescent quantification of IgE against peanut in microliter samples, but this method awaits extension to other allergens. This study aimed to validate a new method, named LuLIPLEX, for multiplexed bioluminescent detection of sIgE against 20 major molecular allergens.Quantification of sIgE against 12 recombinant or purified food allergens and eight aeroallergens was performed by LuLIPLEX versus standard IgE detection methods (ImmunoCAP, ISAC, ALEX, or NOVEOS). Multiplexed detection of IgE against these 20 allergens was performed within 45 min using 50 μL of serum, plasma, or whole blood samples.A head‐to‐head comparison between LuLIPLEX and standard IgE detection methods showed a high correlation among all allergens tested. sIgE profiles in polysensitized subjects could be determined within 45 min in serum and plasma samples, as well as using a single drop of capillary blood.LuLIPLEX is a rapid and sensitive method to quantify sIgE levels against multiple allergens. Given that the test is very fast and can be performed on small and inexpensive luminometers, the IgE LuLIPLEX could allow point‐of‐care testing of sIgE profiles in allergic subjects. [ABSTRACT FROM AUTHOR]

Summary: Heavy‐chain antibodies (HCAbs) are a unique type of antibodies devoid of light chains, and comprised of two heavy chains‐only that recognize their cognate antigen by virtue of a single variable domain also referred to as VHH, single domain antibody (sdAb), or nanobody (Nb). These functional HCAbs, serendipitous discovered about three decades ago, are exclusively found in camelids, comprising dromedaries, camels, llamas, and vicugnas. Nanobodies have become an essential tool in biomedical research and medicine, both in diagnostics and therapeutics due to their beneficial properties: small size, high stability, strong antigen‐binding affinity, low immunogenicity, low production cost, and straightforward engineering into more potent affinity reagents. The occurrence of HCAbs in camelids remains intriguing. It is believed to be an evolutionary adaptation, equipping camelids with a robust adaptive immune defense suitable to respond to the pressure from a pathogenic invasion necessitating a more profound antigen recognition and neutralization. This evolutionary innovation led to a simplified HCAb structure, possibly supported by genetic mutations and drift, allowing adaptive mutation and diversification in the heavy chain variable gene and constant gene regions. Beyond understanding their origins, the application of nanobodies has significantly advanced over the past 30 years. Alongside expanding laboratory research, there has been a rapid increase in patent application for nanobodies. The introduction of commercial nanobody drugs such as Cablivi, Nanozora, Envafolimab, and Carvykti has boosted confidence among in their potential. This review explores the evolutionary history of HCAbs, their ontogeny, and applications in biotechnology and pharmaceuticals, focusing on approved and ongoing medical research pipelines. [ABSTRACT FROM AUTHOR]

Genetic studies have identified the voltage‐gated sodium channel 1.7 (Nav1.7) as pain target. Due to the ineffectiveness of small molecules and monoclonal antibodies as therapeutics for pain, single‐domain antibodies (VHHs) are developed against the human Nav1.7 (hNav1.7) using a novel antigen presentation strategy. A 70 amino‐acid peptide from the hNav1.7 protein is identified as a target antigen. A recombinant version of this peptide is grafted into the complementarity determining region 3 (CDR3) loop of an inert VHH in order to maintain the native 3D conformation of the peptide. This antigen is used to isolate one VHH able to i) bind hNav1.7, ii) slow the deactivation of hNav1.7, iii) reduce the ability of eliciting action potentials in nociceptors, and iv) reverse hyperalgesia in in vivo rat and mouse models. This VHH exhibits the potential to be developed as a therapeutic capable of suppressing pain. This novel antigen presentation strategy can be applied to develop biologics against other difficult targets such as ion channels, transporters and GPCRs. [ABSTRACT FROM AUTHOR]

Background: Antibodies have been proven effective as diagnostic agents for detecting zoonotic diseases. The variable domain of camel heavy chain antibody (VHH), as an antibody derivative, may be used as an alternative for traditional antibodies in existing immunodiagnostic reagents for detecting rapidly spreading infectious diseases. Objectives: To expedite the isolation of specific antibodies for diagnostic purposes, we constructed a semi‐synthetic camel single domain antibody library based on the phage display technique platform (PDT) and verified the validity of this study. Methods: The semi‐synthetic single domain antibody sequences consist of two parts: one is the FR1‐FR3 region amplified by RT‐PCR from healthy camel peripheral blood lymphocytes (PBLs), and the other part is the CDR3‐FR4 region synthesised as an oligonucleotide containing CDR3 randomised region. The two parts were fused by overlapping PCR, resulting in the rearranged variable domain of heavy‐chain antibodies (VHHs). Y. pestis low‐calcium response V protein (LcrV) is an optional biomarker to detect the Y. pestis infection. The semi‐synthetic library herein was screened using recombinant (LcrV) as a target antigen. Results: After four cycles of panning the library, four VHH binders targeting 1–270 aa residues of LcrV were isolated. The four VHH genes with unique sequences were recloned into an expression vector and expressed as VHH‐hFc chimeric antibodies. The purified antibodies were identified and used to develop a lateral flow immunoassay (LFA) test strip using latex microspheres (LM) for the rapid and visual detection of Y. pestis infection. Conclusions: These data demonstrate the great potential of the semi‐synthetic library for use in isolation of antigen‐specific nanobodies and the isolated specific VHHs can be used in antigen‐capture immunoassays. [ABSTRACT FROM AUTHOR]

Biparatopic antibodies (bpAbs) are engineered antibodies that bind to multiple different epitopes within the same antigens. bpAbs comprise diverse formats, including fragment‐based formats, and choosing the appropriate molecular format for a desired function against a target molecule is a challenging task. Moreover, optimizing the design of constructs requires selecting appropriate antibody modalities and adjusting linker length for individual bpAbs. Therefore, it is crucial to understand the characteristics of bpAbs at the molecular level. In this study, we first obtained single‐chain variable fragments and camelid heavy‐chain variable domains targeting distinct epitopes of the metal binding protein MtsA and then developed a novel format single‐chain bpAb connecting these fragment antibodies with various linkers. The physicochemical properties, binding activities, complex formation states with antigen, and functions of the bpAb were analyzed using multiple approaches. Notably, we found that the assembly state of the complexes was controlled by a linker and that longer linkers tended to form more compact complexes. These observations provide detailed molecular information that should be considered in the design of bpAbs. [ABSTRACT FROM AUTHOR]

Ozoralizumab is a bispecific NANOBODY compound that binds tumor necrosis factor alpha (TNFα) and human serum albumin. Ozoralizumab inhibits the TNFα physiological activity while maintaining long‐term plasma retention owing to its human serum albumin–binding ability. A population pharmacokinetic (PK) model was developed using data from 494 Japanese patients with rheumatoid arthritis in Phase II/III and Phase III trials to assess the effects of potential PK covariates. The ozoralizumab PK after subcutaneous administration was described using a 1‐compartment model with first‐order absorption and first‐order elimination processes. A proportional error model was used for inter‐ and intra‐individual variabilities, with covariance set between inter‐individual variabilities of the apparent clearance and apparent distribution volume. Body weight, sex, antidrug antibody status, estimated glomerular filtration rate, and concomitant methotrexate use were identified as covariates for apparent clearance, while body weight and sex were covariates for apparent distribution volume in the final model. Body weight had the greatest effect on the PK of ozoralizumab, while the other covariates had minor effects. When administered at 30 mg every 4 weeks, the predicted steady‐state plasma trough concentration in a patient weighing 83.2 kg exceeded the trough concentration required to maintain efficacy of ozoralizumab, and the estimated exposure in a patient weighing 42.5 kg did not exceed the mean exposure at 80 mg, a well‐tolerated dose, throughout 52 weeks. We developed a population PK model that adequately described the ozoralizumab PK in Japanese patients with rheumatoid arthritis, and none of the evaluated covariates showed clinically relevant effects on the PK of ozoralizumab. [ABSTRACT FROM AUTHOR]

Herein, we describe the generation of potent NK cell engagers (NKCEs) based on single domain antibodies (sdAbs) specific for NKp46 harboring the humanized Fab version of Cetuximab for tumor targeting. After immunization of camelids, a plethora of different VHH domains were retrieved by yeast surface display. Upon reformatting into Fc effector‐silenced NKCEs targeting NKp46 and EGFR in a strictly monovalent fashion, the resulting bispecific antibodies elicited potent NK cell‐mediated killing of EGFR‐overexpressing tumor cells with potencies (EC50killing) in the picomolar range. This was further augmented via co‐engagement of Fcγ receptor IIIa (FcγRIIIa). Importantly, NKp46‐specific sdAbs enabled the construction of various NKCE formats with different geometries and valencies which displayed favorable biophysical and biochemical properties without further optimization. By this means, killing capacities were further improved significantly. Hence, NKp46‐specific sdAbs are versatile building blocks for the construction of different NKCE formats. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) neutralizing antibodies are shown to be effective therapeutics for providing coronavirus disease 2019 (COVID‐19) protection. However, recurrent variants arise and facilitate significant escape from current antibody therapeutics. Bispecific antibodies (bsAbs) represent a unique platform to increase antibody breadth and to reduce neutralization escape. Herein, a novel immunoglobulin G–variable domains of heavy‐chain‐only antibody (IgG–VHH) format bsAb derived from a potent human antibody R15‐F7 and a humanized nanobody P14‐F8‐35 are rationally engineered. The resulting bsAb SYZJ001 efficiently neutralizes wild‐type SARS‐CoV‐2 as well as the alpha, beta, gamma, and delta variants, with superior efficacy to its parental antibodies. Cryo‐electron microscopy structural analysis reveals that R15‐F7 and P14‐F8‐35 bind to nonoverlapping epitopes within the RBD and sterically hindered ACE2 receptor binding. Most importantly, SYZJ001 shows potent prophylactic and therapeutic efficacy against SARS‐CoV‐2 in three established mouse models. Collectively, the current results demonstrate that the novel bsAb format is feasible and effective, suggesting great potential as an inspiring antiviral strategy. [ABSTRACT FROM AUTHOR]

Antibiotics in aquaculture prevent bacterial infection of fish, but their misuse is a public health risk and contributes to the unintentional creation of multiresistant pathogens. Regulatory agencies cannot do the rigorous, expensive testing required to keep up with the volume of seafood shipments. Current rapid test kits for these drugs enable the increase in testing needed for adequate monitoring of food supply chains, but they lack a high degree of accuracy. To combat this, we set out to discover and engineer single‐domain antibodies (VHHs) that bind to small molecule antibiotics, and that can be used in rapid test kits. The small size, solubility, and stability of VHHs are useful properties that can improve the reliability and shelf‐life of test kits for these adulterants. Here, we report a novel anti‐chloramphenicol VHH (Chl‐VHH) with a disassociation constant of 57 nM. This was achieved by immunizing a llama against a chloramphenicol‐keyhole limpet hemocyanin (KLH) conjugate and screening for high affinity binders through phage display. The crystal structure of the bound‐VHH to chloramphenicol was key to identifying a mutation in the binding pocket that resulted in a 16‐fold improvement in binding affinity. In addition, the structure provides new insights into VHH‐hapten interactions that can guide future engineering of VHHs against additional targets. PDB Code(s): 7TJC; [ABSTRACT FROM AUTHOR]

The camelid single domain antibody, referred to VHH or Nanobody, is considered a versatile tool for various biotechnological and clinical applications because of its favorable biophysical properties. To take advantage of these characteristics and for its application in biotechnology and therapy, research on VHH engineering is currently vigorously conducted. To humanize a camelid VHH, we performed complementarity determining region (CDR) grafting using a humanized VHH currently in clinical trials, and investigated the effects of these changes on the biophysical properties of the resulting VHH. The chimeric VHH exhibited a significant decrease in affinity and thermal stability and a large conformational change in the CDR3. To elucidate the molecular basis for these changes, we performed mutational analyses on the framework regions revealing the contribution of individual residues within the framework region. It is demonstrated that the mutations resulted in the loss of affinity and lower thermal stability, revealing the significance of bulky residues in the vicinity of the CDR3, and the importance of intramolecular interactions between the CDR3 and the framework‐2 region. Subsequently, we performed back‐mutational analyses on the chimeric VHH. Back‐mutations resulted in an increase of the thermal stability and affinity. These data suggested that back‐mutations restored the intramolecular interactions, and proper positioning and/or dynamics of the CDR3, resulting in the gain of thermal stability and affinity. These observations revealed the molecular contribution of the framework region on VHHs and further designability of the framework region of VHHs without modifying the CDRs. PDB Code(s): 7XL0 and 7XL1; [ABSTRACT FROM AUTHOR]

Single‐domain antibodies (sdAbs), the autonomous variable domains of camelid and shark heavy‐chain antibodies, have many desirable properties as components of biologic drugs. However, their sequences may increase the risk of immunogenicity and antidrug antibody (ADA) development in humans, and thus, sdAbs are routinely humanized during development. Here, we review and summarize the available evidence regarding the factors governing immunogenicity of sdAbs and our current state of knowledge of strategies to mitigate immunogenicity risks by humanization. While several sdAb properties, including high homology of camelid VHHs with human IGHV3 gene products, favor low immunogenicity in humans, epitopes absent in the human repertoire including the exposed VH:VL interface may be intrinsically immunogenic. While most clinical trials have demonstrated minimal sdAb immunogenicity, two notable exceptions (the tetrameric DR5‐specific VHH TAS266 and the TNFR1‐specific VH GSK1995057) illustrate that special caution must be taken in identifying preexisting ADAs against highly potent sdAbs. Nonhuman sequence alone does not adequately explain sdAb immunogenicity, as some camelid VHHs are nonimmunogenic while some fully human VHs elicit ADAs. The presence of preexisting ADAs directed against the exposed C‐termini of some sdAbs in a significant proportion of individuals awaits a molecular explanation. Whether sdAb humanization reduces or promotes immunogenicity remains unclear: reduction of nonhuman sequence content at the expense of introducing low‐level aggregation in humanized variants may be counterproductive. Further work will establish thresholds for VHH and VNAR humanization to maximize human sequence content while avoiding loss of binding affinity and/or immunogenicity resulting from aggregation or decreased stability. [ABSTRACT FROM AUTHOR]

Background: Recent studies showed that a single injection of human monoclonal allergen‐specific IgG antibodies significantly reduced allergic symptoms in birch pollen‐allergic patients. Since the production of full monoclonal antibodies in sufficient amounts is laborious and expensive, we sought to investigate if smaller recombinant allergen‐specific antibody fragments, that is, nanobodies, have similar protective potential. For this purpose, nanobodies specific for Bet v 1, the major birch pollen allergen, were generated to evaluate their efficacy to inhibit IgE‐mediated responses. Methods: A cDNA‐VHH library was constructed from a camel immunized with Bet v 1 and screened for Bet v 1 binders encoding sequences by phage display. Selected nanobodies were expressed, purified, and analyzed in regards of epitope‐specificity and affinity to Bet v 1. Furthermore, cross‐reactivity to Bet v 1‐homologues from alder, hazel and apple, and their usefulness to inhibit IgE binding and allergen‐induced basophil activation were investigated. Results: We isolated three nanobodies that recognize Bet v 1 with high affinity and cross‐react with Aln g 1 (alder) and Cor a 1 (hazel). Their epitopes were mapped to the alpha‐helix at the C‐terminus of Bet v 1. All nanobodies inhibited allergic patients' polyclonal IgE binding to Bet v 1, Aln g 1, and Cor a 1 and partially suppressed Bet v 1‐induced basophil activation. Conclusion: We identified high‐affinity Bet v 1‐specific nanobodies that recognize an important IgE epitope and reduce allergen‐induced basophil activation revealing the first proof that allergen‐specific nanobodies are useful tools for future treatment of pollen allergy. [ABSTRACT FROM AUTHOR]

Single domain antibodies (VHHs) are potentially disruptive therapeutics, with important biological value for treatment of several diseases, including neurological disorders. However, VHHs have not been widely used in the central nervous system (CNS), largely because of their restricted blood–brain barrier (BBB) penetration. Here, we propose a gene transfer strategy based on BBB‐crossing adeno‐associated virus (AAV)‐based vectors to deliver VHH directly into the CNS. As a proof‐of‐concept, we explored the potential of AAV‐delivered VHH to inhibit BACE1, a well‐characterized target in Alzheimer's disease. First, we generated a panel of VHHs targeting BACE1, one of which, VHH‐B9, shows high selectivity for BACE1 and efficacy in lowering BACE1 activity in vitro. We further demonstrate that a single systemic dose of AAV‐VHH‐B9 produces positive long‐term (12 months plus) effects on amyloid load, neuroinflammation, synaptic function, and cognitive performance, in the AppNL‐G‐F Alzheimer's mouse model. These results constitute a novel therapeutic approach for neurodegenerative diseases, which is applicable to a range of CNS disease targets. Synopsis: VHH and blood‐brain‐barrier (BBB)‐crossing AAV‐based vectors are combined to achieve highly‐specific, long‐term BACE1 inhibition in a mouse model of Alzheimer's disease (AD). A gene transfer strategy based on BBB‐crossing AAV vectors is developed to deliver VHH single domain antibodies directly into the CNS.VHH‐B9 is generated to target BACE1, an enzyme critical to Aβ generation in AD, and incorporated into an AAV‐PHP.B‐based vector.A single dose of AAV‐VHH resulted in long‐term VHH expression in the AppNL‐G‐F mouse model, with concomitant improvements in cognitive status, amyloidosis, neuroinflammation, and synaptic function. [ABSTRACT FROM AUTHOR]

VHH stands for the variable regions of heavy chain only of camelid IgGs. The VHH family forms a set of interesting proteins derived from antibodies that maintain their capacity to recognize the antigen, despite their relatively small molecular weight (in the 12,000 Da range). Continuing our exploration of the possibilities of those molecules, we chose to design alternative molecules with maintained antigen recognition, but enhanced capacity, by fusing four VHH with one Fc, the fragment crystallizable region of antibodies. In doing so, we aimed at having a molecule with superior quantitative antigen recognition (×4) while maintaining its size below the 110 kDa. In the present paper, we described the building of those molecules that we coined VHH2‐Fc‐VHH2. The structure of VHH2‐Fc‐VHH2 in complex with HER2 antigen was determined using electronic microscopy and modeling. The molecule is shown to bind four HER2 proteins at the end of its flexible arms. VHH2‐Fc‐VHH2 also shows an internalization capacity via HER2 receptor superior to the reference anti‐HER2 monoclonal antibody, Herceptin®, and to a simple fusion of two VHH with one Fc (VHH2‐Fc). This new type of molecules, VHH2‐Fc‐VHH2, could be an interesting addition to the therapeutic arsenal with multiple applications, from diagnostic to therapy. [ABSTRACT FROM AUTHOR]

Single‐domain antibodies (sdAbs) offer the affinity and therapeutic value of conventional antibodies, with increased stability and solubility. Unlike conventional antibodies, however, sdAbs do not benefit from a platform manufacturing process. While successful production of a variety of sdAbs has been shown in numerous hosts, purification methods are often molecule specific or require affinity tags, which generally cannot be used in clinical manufacturing due to regulatory concerns. Here, we have developed a broadly applicable production and purification process for sdAbs in Komagataella phaffii (Pichia pastoris) and demonstrated the production of eight different sdAbs at a quality appropriate for nonclinical studies. We developed a two‐step, integrated purification process without the use of affinity resins and showed that modification of a single process parameter, pH of the bridging buffer, was required for the successful purification of a variety of sdAbs. Further, we determined that this parameter can be predicted based only on the biophysical characteristics of the target molecule. Using these methods, we produced nonclinical quality sdAbs as few as 5 weeks after identifying the product sequence. Nonclinical studies of three different sdAbs showed that molecules produced using our platform process conferred protection against viral shedding of rotavirus or H1N1 influenza and were equivalent to similar molecules produced in Escherichia coli and purified using affinity tags. [ABSTRACT FROM AUTHOR]

Spatial organization and conformational changes of antibodies may significantly affect their biological functions. We assessed the effect of mutual organization of the two VHH domains within bispecific antibodies recognizing human TNF and the surface molecules of murine myeloid cells (F4/80 or CD11b) on TNF retention and inhibition. TNF‐neutralizing properties in vitro and in vivo of MYSTI‐2 and MYSTI‐3 antibodies were compared with new variants with interchanged VHH domains and different linker sequences. The most effective structure of MYSTI‐2 and MYSTI‐3 proteins required the Ser/Gly‐containing 'superflexible' linker. The orientation of the modules was crucial for the activity of the proteins, but not for MYSTI‐3 with the Pro/Gln‐containing 'semi‐rigid' linker. Our results may contribute toward the development of more effective drug prototypes. [ABSTRACT FROM AUTHOR]

A distinguishing feature of camel (Camelus dromedarius) VHH domains are noncanonical disulfide bonds between CDR1 and CDR3. The disulfide bond may provide an evolutionary advantage, as one of the cysteines in the bond is germline encoded. It has been hypothesized that this additional disulfide bond may play a role in binding affinity by reducing the entropic penalty associated with immobilization of a long CDR3 loop upon antigen binding. To examine the role of a noncanonical disulfide bond on antigen binding and the biophysical properties of a VHH domain, we have used the VHH R303, which binds the Listeria virulence factor InlB as a model. Using site directed mutagenesis, we produced a double mutant of R303 (C33A/C102A) to remove the extra disulfide bond of the VHH R303. Antigen binding was not affected by loss of the disulfide bond, however the mutant VHH displayed reduced thermal stability (Tm = 12°C lower than wild‐type), and a loss of the ability to fold reversibly due to heat induced aggregation. X‐ray structures of the mutant alone and in complex with InlB showed no major changes in the structure. B‐factor analysis of the structures suggested that the loss of the disulfide bond elicited no major change on the flexibility of the CDR loops, and revealed no evidence of loop immobilization upon antigen binding. These results suggest that the noncanonical disulfide bond found in camel VHH may have evolved to stabilize the biophysical properties of the domain, rather than playing a significant role in antigen binding. [ABSTRACT FROM AUTHOR]

Vibrio harveyi, as one of the main pathogens of vibriosis, has serious multidrug resistance, which has been a focus for domestic and foreign researchers. Vibrio harveyi hemolysin (VHH), an important virulence determinant of V. harveyi, causes cell necrosis and tissue damage by lysing cell membranes, which is essential for V. harveyi invasion of the host. The critical role of VHH in the virulence of V. harveyi renders it an ideal target for designing novel anti‐virulence therapeutics. We found that honokiol, a natural compound, could act as a potent antagonist of VHH‐mediated haemolysis at non‐bacteriostatic concentrations. Honokiol can effectively inhibit the damage caused by VHH and V. harveyi both in vitro and in vivo. qRT‐PCR and molecular docking analysis showed that although honokiol up‐regulated the transcription level of vhh, it could block the active centre of VHH directly and forcefully, thereby reducing the catalytic activity of VHH. The results suggest that HNK could have great potential in the development of new aquaculture drugs. [ABSTRACT FROM AUTHOR]

Single‐domain antibodies (sdAbs), the variable domains of camelid heavy chain‐only antibodies, are generally thought to poorly recognize nonproteinaceous small molecules and carbohydrates in comparison with conventional antibodies. However, the structures of anti‐methotrexate, anti‐triclocarban and anti‐cortisol sdAbs revealed unexpected contributions of the non‐hypervariable "CDR4" loop, formed between β‐strands D and E of framework region 3, in binding. Here, we investigated the potential role of CDR4 in sdAb binding to a hapten, 15‐acetyl‐deoxynivalenol (15‐AcDON), and to carbohydrates. We constructed and panned a phage‐displayed library in which CDR4 of the 15‐AcDON‐specific sdAb, NAT‐267, was extended and randomized. From this library, we identified one sdAb, MA‐232, bearing a 14‐residue insertion in CDR4 and showing improved binding to 15‐AcDON by ELISA and surface plasmon resonance. On the basis of these results, we constructed a second set of phage‐displayed libraries in which the CDR4 and other regions of three hapten‐ or carbohydrate‐binding sdAbs were diversified. With the goal of identifying sdAbs with novel glycan‐binding specificities, we panned the library against four tumor‐associated carbohydrate antigens but were unable to enrich binding phages. Thus, we conclude that while CDR4 may play a role in binding of some rare hapten‐specific sdAbs, diversifying this region through molecular engineering is probably not a general solution to sdAb carbohydrate recognition in the absence of a paired VL domain. [ABSTRACT FROM AUTHOR]

In the continuous exploration of the VHH chemistry, biochemistry and therapeutic future use, we investigated two different production strategies of this small antibody‐like protein, using an anti‐HER2 VHH as a model. The total chemical synthesis of the 125 amino‐acid peptide was performed with reasonable yield, even if optimization will be necessary to upgrade this kind of production. In parallel, we expressed the same sequence in two different hosts: Escherichia coli and Pichia pastoris. Both productions were successful and led to a fair amount of VHHs. The integrity and conformation of the VHH were characterized by complementary mass spectrometry approaches, while surface plasmon resonance experiments were used to assess the VHH recognition capacity and affinity toward its "antigen." Using this combination of orthogonal techniques, it was possible to show that the three VHHs—whether synthetic or recombinant ones—were properly and similarly folded and recognized the "antigen" HER2 with similar affinities, in the nanomolar range. This opens a route toward further exploration of modified VHH with unnatural amino acids and subsequently, VHH‐drug conjugates. [ABSTRACT FROM AUTHOR]

BACKGROUND: The variable domain of camelid heavy‐chain antibodies (VHH) is increasingly being adapted to detect small molecules in various matrices. The insecticide carbaryl is widely used in agriculture while its residues have posed a threat to food safety and human health. RESULTS: VHHs specific for carbaryl were generated from an alpaca immunized with the hapten CBR1 coupled to keyhole limpet hemocyanin. An enzyme‐linked immunosorbent assay (ELISA) based on the VHH C1 and the coating antigen CBR2‐BSA was developed for the detection of carbaryl in cereals. This assay, using an optimized assay buffer (pH 6.5) containing 10% methanol and 0.8% NaCl, has a half‐maximum signal inhibition concentration of 5.4 ng mL−1 and a limit of detection (LOD) of 0.3 ng mL−1 for carbaryl, and shows low cross reactivity (≤0.8%) with other tested carbamates. The LOD of carbaryl using the VHH‐based ELISA was 36 ng g−1 in rice and maize and 72 ng g−1 in wheat. Recoveries of carbaryl in spiked rice, maize and wheat samples were in the range of 81–106%, 96–106% and 83–113%, respectively. Relative standard deviations of repeatability and intra‐laboratory reproducibility were in the range of 0.8–9.2% and 2.9–9.7%, respectively. CONCLUSION: The VHH‐based ELISA was highly effective in detecting carbaryl in cereal samples after simple sample extraction and dilution. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

CD22 is a B‐cell‐specific trans‐membrane glycoprotein, which is found on the surface of the most B cells and modulates their function, survival, and apoptosis. Recently, targeting this cell surface biomarker in B‐cell malignancies and disorders has attracted a lot of attention. The variable domain of camelid single‐chain antibodies (VHH, nanobody) is a form of antibodies with novel properties including small size (15–17 kDa), thermal and chemical stability, high affinity and homology to human antibody sequences. In this study, a novel anti‐CD22‐specific VHH (Nb) has been developed and characterized by the screening of an immunized phage display library and its binding to CD22+ B cells is evaluated. Produced anti‐CD22 VHH had a single protein band about 17 kDa of molecular size in Western blotting and its binding affinity was approximately 9 × 10−9 M. Also, this product had high specificity and it was able to recognize the natural CD22 antigen in CD22+ cell lysate as well as on the cell surface (93%). This anti‐CD22 VHH with both high affinity and specificity recognizes CD22 antigen well and can be used in diagnosis and treatment of B cell disorders and malignancies. [ABSTRACT FROM AUTHOR]

Abstract: Nanobodies are a class of antigen‐binding protein derived from camelids that achieve comparable binding affinities and specificities to classical antibodies, despite comprising only a single 15 kDa variable domain. Their reduced size makes them an exciting target molecule with which we can explore the molecular code that underpins binding specificity—how is such high specificity achieved? Here, we use a novel dataset of 90 nonredundant, protein‐binding nanobodies with antigen‐bound crystal structures to address this question. To provide a baseline for comparison we construct an analogous set of classical antibodies, allowing us to probe how nanobodies achieve high specificity binding with a dramatically reduced sequence space. Our analysis reveals that nanobodies do not diversify their framework region to compensate for the loss of the VL domain. In addition to the previously reported increase in H3 loop length, we find that nanobodies create diversity by drawing their paratope regions from a significantly larger set of aligned sequence positions, and by exhibiting greater structural variation in their H1 and H2 loops. [ABSTRACT FROM AUTHOR]

The transcription and replication machinery of negative-stranded RNA viruses presents a possible target for interference in the viral life cycle. We demonstrate the validity of this concept through the use of cytosolically expressed single-domain antibody fragments ( VHHs) that protect cells from a lytic infection with vesicular stomatitis virus ( VSV) by targeting the viral nucleoprotein N. We define the binding sites for two such VHHs, 1004 and 1307, by X-ray crystallography to better understand their inhibitory properties. We found that VHH 1307 competes with the polymerase cofactor P for binding and thus inhibits replication and mRNA transcription, while binding of VHH 1004 likely only affects genome replication. The functional relevance of these epitopes is confirmed by the isolation of escape mutants able to replicate in the presence of the inhibitory VHHs. The escape mutations allow identification of the binding site of a third VHH that presumably competes with P for binding at another site than 1307. Collectively, these binding sites uncover different features on the N protein surface that may be suitable for antiviral intervention. [ABSTRACT FROM AUTHOR]

Vibrio cholerae serogroup O1 is the main causative agent of cholera diseases defined by life threatening rice watery diarrhea. Cholera routine vaccination has failed in controlling epidemics in developing countries because of their hard and expensive production. In this study, our aim was to investigate phage displayed mimotopes that could mimic V. cholerae lipopolysaccharide (LPS). Although LPS of Vibrio, as an endotoxin, can stimulate the immune system, thereby making it a suitable candidate for cholera vaccine, its toxicity remains as a main problem. Phage particles displaying 12 amino acid peptides were selected from phage library mimicking the antigenic epitopes of LPS from vibrio. The screening was carried out using single-domain antibody fragment VHH against LPS as target through three rounds of selection. Three clones with highest affinity to VHH were selected. To find out a new and efficient vaccine against cholera, these three phage particles containing high-affinity peptides were administered to mice to investigate the active and passive immunity. Out of 20 particles, three showed the highest affinity toward VHH. ELISA was carried out with immunized mice sera using LPS and three selected phages particles individually. ETEC, Shigella sonnei, and clinical isolates were used as bacterial targets. These three selected phages (individually or in combination) could stimulate mice immune system producing active and passive immunity. The mice immunized with phage particles could protect about 14 LD50 of V. cholerae. In conclusion, these peptides are mimicking LPS and can potentially act as vaccine candidates against V. cholerae. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A PMMA-binding peptide (PMMA-tag) was genetically fused with the C-terminal region of an anti-human chorionic gonadotropin (hCG) single-domain antibody (VHH). It was over-expressed in an insoluble fraction of E. coli cells, and recovered in the presence of 8 M urea via one-step IMAC purification. Monomeric and denatured PMMA-tag-fused VHH (VHH-PM) was successfully prepared via the reduction and oxidation of VHH-PM at a concentration less than 1 mg/mL in the presence of 8 M of urea. Furthermore, the VHH-PM was refolded with a recovery of more than 95% by dialysis against 50 mM TAPS at pH 8.5, because the genetic fusion of PMMA-tag resulted in a decrease in the apparent isoelectric point (pI) of the fusion protein, and its solubility at weak alkaline pH was considerably increased. The antigen-binding activities of VHH-PM in the adsorptive state were 10-fold higher than that of VHH without a PMMA-tag. The density of VHH-PM on a PMMA plate was twice that of VHH, indicating that the site-directed attachment of a PMMA-tag resulted in positive effects to the adsorption amount as well as to the orientation of VHH-PM in its adsorptive state. The preparation and immobilization methods for VHH-PM against hCG developed in the present study were further applied to VHH-PMs against four different antigens, and consequently, those antigens with the concentrations lower than 1 ng/mL were detected by the sandwich ELISA. Thus, the VHH-PMs developed in the present study are useful for preparation of high-performance and economical immunosorbent for detection of biomarkers. [ABSTRACT FROM AUTHOR]

Accumulation and aggregation of the amyloid-β (Aβ) peptide is associated with Alzheimer's disease ( AD). Aβ is generated from the amyloid precursor protein by the successive action of two membrane-associated processing enzymes: β-secretase or β-site of amyloid precursor protein cleaving enzyme 1 ( BACE1) and γ-secretase. Inhibition of one or both of these enzymes prevents Aβ generation and the accompanying Aβ accumulation. Antigen binding fragments from camelid heavy chain only antibodies ( VHHs) were found to exert excellent enzyme inhibition activity. In the present study, we generated VHHs against BACE1 by active immunization of Lama glama with the recombinant BACE1 protein. Two classes of VHHs were selected from a VHH-phage display library by competitive elution with a peptide encoding the Swedish mutation variant of the BACE1 processing site. One VHH was found to inhibit the enzyme activity of BACE1 in vitro and in cell culture, whereas two other VHHs were found to stimulate BACE1 activity under the same conditions in vitro. Furthermore, an in vivo study with a transgenic AD mouse model, using intracisternal injection of the inhibitory VHH, led to acute reduction of the Aβ load in the blood and brain. This inhibitory VHH may be considered as a candidate molecule for a therapy directed towards reduction of Aβ load and prevention of AD progression. Both the inhibitory and stimulatory VHH may be useful for improving our understanding of the structure-function relationship of BACE1, as well as its role in AD progression. Database The GenBank sequence accession numbers are for VHH B1a; for VHH B3a; and for VHH B5a. [ABSTRACT FROM AUTHOR]

Post-translational modifications are difficult to visualize in living cells and are conveniently analyzed using antibodies. Single-chain antibody fragments derived from alpacas and called nanobodies can be expressed and bind to the target antigenic sites in living cells. As a proof of concept, we generated and characterized nanobodies against the commonly used biomarker for DNA double strand breaks γ-H2AX. In vitro and in vivo characterization showed the specificity of the γ-H2AX nanobody. Mammalian cells were transfected with fluorescent fusions called chromobodies and DNA breaks induced by laser microirradiation. We found that alternative epitope recognition and masking of the epitope in living cells compromised the chromobody function. These pitfalls should be considered in the future development and screening of intracellular antibody biomarkers. [ABSTRACT FROM AUTHOR]

The variable region of camelid heavy-chain antibodies produces the smallest known antibody fragment with antigen-binding capability (a VHH). The VHH R303 binds internalin B (InlB), a virulence factor expressed by the pathogen Listeria monocytogenes. InlB is critical for initiation of Listeria infection, as it binds a receptor (c-Met) on epithelial cells, triggering the entry of bacteria into host cells. InlB is surface-exposed and is required for virulence, hence a VHH targeting InlB has potential applications for pathogen detection or therapeutic intervention. Here, the expression, purification, crystallization and X-ray diffraction of R303 are reported. Crystals of R303 were obtained following in situ proteolysis with trypsin. Gel filtration and SDS-PAGE revealed that trypsin removed the C-terminal tag region of R303, facilitating crystal formation. Crystals of R303 diffracted to 1.3 Å resolution and belonged to the monoclinic space group P21, with unit-cell parameters a = 46.4, b = 31.2, c = 74.8 Å, β = 93.8°. The crystals exhibited a Matthews coefficient of 1.95 Å3 Da−1 with two molecules in the asymmetric unit. [ABSTRACT FROM AUTHOR]

Single-domain antibodies (sd Abs) are powerful tools for the detection, quantification, purification and subcellular localization of proteins of interest in biological research. We have generated camelid ( Lama pacos) heavy chain-only variable VH domain ( VH H) libraries against antigens in total cell lysates from Chlamydomonas reinhardtii. The sd Abs in the sera from immunized animals and VH H antibody domains isolated from the library show specificity to C. reinhardtii and lack of reactivity to antigens from four other algae: Chlorella variabilis, Coccomyxa subellipsoidea, Nannochloropsis oceanica and Thalassiosira pseudonana. Antibodies were produced against a diverse representation of antigens as evidenced by sera ELISA and protein-blot analyses. A phage-display library consisting of the VH H region contained at least 106 individual transformants, and thus should represent a wide range of C. reinhardtii antigens. The utility of the phage library was demonstrated by using live C. reinhardtii cells to pan for VH H clones with specific recognition of cell-surface epitopes. The lead candidate VH H clones (designated B11 and H10) bound to C. reinhardtii with EC50 values ≤0.5 n m. Treatment of cells with VH H B11 fused to the m Cherry or green fluorescent proteins allowed brilliant and specific staining of the C. reinhardtii cell wall and analysis of cell-wall genesis during cell division. Such high-complexity VH H antibody libraries for algae will be valuable tools for algal researchers and biotechnologists. [ABSTRACT FROM AUTHOR]

ADP-ribosylation of host cell proteins is a common mode of cell intoxication by pathogenic bacterial toxins. Antibodies induced by immunization with inactivated ADP-ribosylating toxins provide efficient protection in case of some secreted toxins, e.g., diphtheria and pertussis toxins. However, other ADP-ribosylating toxins, such as Salmonella SpvB toxin, are secreted directly from the Salmonella-containing vacuole into the cytosol of target cells via the SPI-2 encoded bacterial type III secretion system, and thus are inaccessible to conventional antibodies. Small-molecule ADP-ribosylation inhibitors are fraught with potential side effects caused by inhibition of endogenous ADP-ribosyltransferases. Here, we report the development of a single-domain antibody from an immunized llama that blocks the capacity of SpvB to ADP-ribosylate actin at a molar ratio of 1:1. The single-domain antibody, when expressed as an intrabody, effectively protected cells from the cytotoxic activity of a translocation-competent chimeric C2IN-C/SpvB toxin. Transfected cells were also protected against cytoskeletal alterations induced by wild-type SpvB-expressing strains of Salmonella. This proof of principle paves the way for developing new antidotes against intracellular toxins. [ABSTRACT FROM AUTHOR]

Tumour necrosis factor (TNF) is a major pro-inflammatory cytokine involved in multiple inflammatory diseases. The detrimental activity of TNF can be blocked by various antagonists, and commercial therapeutics based upon this principle have been approved for treatment of diseases including rheumatoid arthritis, Crohn's disease and psoriasis. In a search for new, improved anti-inflammatory therapeutics we have designed a single-domain monoclonal antibody (VH), which recognizes TNF. The antibody component (TNF-VH) is based upon an anti-human TNF Camelidae heavy-chain monoclonal antibody, which was linked to an elastin-like polypeptide (ELP). We demonstrate that ELP fusion to the TNF-VH enhances accumulation of the fusion protein during biomanufacturing in transgenic tobacco plants. With this study, we show for the first time that this plant-derived anti-human TNF-VH antibody was biologically active in vivo. Therefore, therapeutic application of TNF-VH-ELP fusion protein was tested in humanized TNF mice and was shown to be effective in preventing death caused by septic shock. The in vivo persistence of the ELPylated antibody was ∼24 fold longer than that of non-ELPylated TNF-VH. [ABSTRACT FROM AUTHOR]

Hypoxia is a hallmark of solid cancers and triggers the transcription of genes responsible for cell survival. The transcription factor Hypoxia-Inducible Factor 1 (HIF-1) is a key regulator in this response and frequently activated in human cancer. HIF-1 activation is associated with tumor aggressiveness and poor clinical outcome and, therefore, may provide an attractive therapeutic target. Here we provide a novel approach for HIF-1 targeted therapy using single-domain llama antibodies directed against the HIF-1α oxygen dependent degradation domain which encompass the N-terminal transactivation domain. Conditional expression of HIF intrabodies in mammalian cells interfered with binding to pVHL and inhibited hypoxia induced activation of endogenous target genes. Inducible intrabody targeting is a highly specific strategy for temporal protein inactivation and may have applications for disease treatment. [ABSTRACT FROM AUTHOR]

A crystallization chaperone is an auxiliary protein that binds to a target of interest, enhances and modulates crystal packing, and provides high-quality phasing information. We critically evaluated the effectiveness of a camelid single-domain antibody (VHH) as a crystallization chaperone. By using a yeast surface display system for VHH, we successfully introduced additional Met residues in the core of the VHH scaffold. We identified a set of SeMet-labeled VHH variants that collectively produced six new crystal forms as the complex with the model antigen, RNase A. The crystals exhibited monoclinic, orthorhombic, triclinic, and tetragonal symmetry and have one or two complexes in the asymmetric unit, some of which diffracted to an atomic resolution. The phasing power of the Met-enriched VHH chaperone allowed for auto-building the entire complex using single-anomalous dispersion technique (SAD) without the need for introducing SeMet into the target protein. We show that phases produced by combining SAD and VHH model-based phases are accurate enough to easily solve structures of the size reported here, eliminating the need to collect multiple wavelength multiple-anomalous dispersion (MAD) data. Together with the presence of high-throughput selection systems (e.g., phage display libraries) for VHH, the enhanced VHH domain described here will be an excellent scaffold for producing effective crystallization chaperones. [ABSTRACT FROM AUTHOR]

The variable VHH domains of camelid single chain antibodies have been useful in numerous biotechnology applications due to their simplicity, biophysical properties, and abilities to bind to their cognate antigens with high affinities and specificity. Their interactions with proteins have been well‐studied, but considerably less work has been done to characterize their ability to bind haptens. A high‐resolution structural study of three nanobodies (T4, T9, and T10) which have been shown to bind triclocarban (TCC, 3‐(4‐chlorophenyl)‐1‐(3,4‐dichlorophenyl)urea) with near‐nanomolar affinity shows that binding occurs in a tunnel largely formed by CDR1 rather than a surface or lateral binding mode seen in other nanobody‐hapten interactions. Additional significant interactions are formed with a non‐hypervariable loop, sometimes dubbed "CDR4". A comparison of apo and holo forms of T9 and T10 shows that the binding site undergoes little conformational change upon binding of TCC. Structures of three nanobody‐TCC complexes demonstrated there was not a standard binding mode. T4 and T9 have a high degree of sequence identity and bind the hapten in a nearly identical manner, while the more divergent T10 binds TCC in a slightly displaced orientation with the urea moiety rotated approximately 180° along the long axis of the molecule. In addition to methotrexate, this is the second report of haptens binding in a tunnel formed by CDR1, suggesting that compounds with similar hydrophobicity and shape could be recognized by nanobodies in analogous fashion. Structure‐guided mutations failed to improve binding affinity for T4 and T9 underscoring the high degree of natural optimization. Single‐chain antibodies can be raised in camelids that bind to haptens with high affinity and specificity. This can be accomplished by enveloping a substantial portion of the molecule in a tunnel to maximize interactions. Despite this general mode of binding, independent antibodies can bind the same hapten in different orientations within this tunnel. [ABSTRACT FROM AUTHOR]