Rapid and Sensitive Detection of Staphylococcal Enterotoxin B by Recombinant Nanobody Using Phage Display Technology

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.

Phage display technology for fabricating a recombinant monoclonal ScFv antibody against tetanus toxin

Tetanus is a specific infectious disease, often associated with lower immunization in developing countries and catastrophic events (such as earthquakes). Millions of people, especially children, die every year from tetanus disease. Therefore, it is necessary to devise a rapid and sensitive detection method for tetanus toxin to ensure an early diagnosis and clinical treatment of tetanus. The current study looks at developing a novel, high specific, low-cost, and sensitive ScFv antibody. It is capable of tetanus detection immunoassays in clinical diagnosis, suspicious foods, and water monitoring. For this regard, a high-quality phage display antibody library (8.7 × 107 PFU/ml) was constructed. Tetanus-specific antibodies with high affinity retrieved from libraries. After phage rescue and four rounds of biopanning, clone screening was performed by phage ELISA. Recombinant antibodies expressed from the AC8 clone showed the highest affinity for tetanus. SDS-PAGE and western blotting confirmed the presence of a high-quality, pure ScFv band at 32 kDa. ELISA was used to determine the affinity value, estimated to be around 10-8 M. The results suggest that the proposed detection method by ScFv antibodies is an alternative diagnostic tool enabling rapid and specific detection of the tetanus toxin.

Emerging Landscape of Nanobodies and Their Neutralizing Applications against SARS-CoV-2 Virus

The new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes the coronavirus disease 2019 (COVID-19) has significantly altered people's way of life. Despite widespread knowledge of vaccination, mask use, and avoidance of close contact, COVID-19 is still spreading around the world. Numerous research teams are examining the SARS-CoV-2 infection process to discover strategies to identify, prevent, and treat COVID-19 to limit the spread of this chronic coronavirus illness and restore lives to normalcy. Nanobodies have advantages over polyclonal and monoclonal antibodies (Ab) and Ab fragments, including reduced size, high stability, simplicity in manufacture, compatibility with genetic engineering methods, and lack of solubility and aggregation issues. Recent studies have shown that nanobodies that target the SARS-CoV-2 receptor-binding domain and disrupt ACE2 interactions are helpful in the prevention and treatment of SARS-CoV-2-infected animal models, despite the lack of evidence in human patients. The creation and evaluation of nanobodies, as well as their diagnostic and therapeutic applications against COVID-19, are discussed in this paper.

Development of Thermally Stable Nanobodies for Detection and Neutralization of Staphylococcal Enterotoxin B

In this study, sixteen unique staphylococcal enterotoxin B (SEB)-reactive nanobodies (nbs), including ten monovalent and six bivalent nbs, were developed. All characterized nbs were highly specific for SEB and did not cross-react with other staphylococcal enterotoxins (SE). Several formats of highly sensitive enzyme-linked immunosorbent assays (ELISAs) were established using SEB nbs and a polyclonal antibody (pAb). The lowest limit of detection (LOD) reached 50 pg/mL in PBS. When applied to an ELISA to detect SEB-spiked milk (a commonly contaminated foodstuff), a LOD as low as 190 pg/mL was obtained. The sensitivity of ELISA was found to increase concurrently with the valency of nbs used in the assay. In addition, a wide range of thermal tolerance was observed among the sixteen nbs, with a subset of nbs, SEB-5, SEB-9, and SEB-6², retaining activity even after exposure to 95 °C for 10 min, whereas the conventional monoclonal and polyclonal antibodies exhibited heat-labile properties. Several nbs demonstrated a long shelf-life, with one nb (SEB-9) retaining 93% of its activity after two weeks of storage at room temperature. In addition to their usage in toxin detection, eleven out of fifteen nbs were capable of neutralizing SEB's super-antigenic activity, demonstrated by their inhibition on IL-2 expression in an ex vivo human PBMC assay. Compared to monoclonal and polyclonal antibodies, the nbs are relatively small, thermally stable, and easy to produce, making them useful in applications for sensitive, specific, and cost-effective detection and management of SEB contamination in food products.

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.

A Novel Nanobody-Horseradish Peroxidase Fusion Based-Competitive ELISA to Rapidly Detect Avian Corona-Virus-Infectious Bronchitis Virus Antibody in Chicken Serum

Avian coronavirus-infectious bronchitis virus (AvCoV-IBV) is the causative agent of infectious bronchitis (IB) that has brought great threat and economic losses to the global poultry industry. Rapid and accurate diagnostic methods are very necessary for effective disease monitoring. At the present study, we screened a novel nanobody against IBV-N protein for development of a rapid, simple, sensitive, and specific competitive ELISA for IBV antibody detection in order to enable the assessment of inoculation effect and early warning of disease infection. Using the phage display technology and bio-panning, we obtained 7 specific nanobodies fused with horseradish peroxidase (HRP) which were expressed in culture supernatant of HEK293T cells. Out of which, the nanobody of IBV-N-Nb66-vHRP has highly binding with IBV-N protein and was easily blocked by the IBV positive serums, which was finally employed as an immunoprobe for development of the competitive ELISA (cELISA). In the newly developed cELISA, we reduce the use of enzyme-conjugated secondary antibody, and the time of whole operation process is approximately 1 h. Moreover, the IBV positive serums diluted at 1:1000 can still be detected by the developed cELISA, and it has no cross reactivity with others chicken disease serums including Newcastle disease virus, Fowl adenovirus, Avian Influenza Virus, Infectious bursal disease virus and Hepatitis E virus. The cut-off value of the established cELISA was 36%, and the coefficient of variation of intra- and inter-assay were 0.55–1.65% and 2.58–6.03%, respectively. Compared with the commercial ELISA (IDEXX kit), the agreement rate of two methods was defined as 98% and the kappa value was 0.96, indicating the developed cELISA has high consistency with the commercial ELISA. Taken together, the novel cELISA for IBV antibody detection is a simple, rapid, sensitive, and specific immunoassay, which has the potential to rapidly test IBV antibody contributing to the surveillance and control of the disease.

Developing Recombinant Antibodies by Phage Display Against Infectious Diseases and Toxins for Diagnostics and Therapy

Antibodies are essential molecules for diagnosis and treatment of diseases caused by pathogens and their toxins. Antibodies were integrated in our medical repertoire against infectious diseases more than hundred years ago by using animal sera to treat tetanus and diphtheria. In these days, most developed therapeutic antibodies target cancer or autoimmune diseases. The COVID-19 pandemic was a reminder about the importance of antibodies for therapy against infectious diseases. While monoclonal antibodies could be generated by hybridoma technology since the 70ies of the former century, nowadays antibody phage display, among other display technologies, is robustly established to discover new human monoclonal antibodies. Phage display is an in vitro technology which confers the potential for generating antibodies from universal libraries against any conceivable molecule of sufficient size and omits the limitations of the immune systems. If convalescent patients or immunized/infected animals are available, it is possible to construct immune phage display libraries to select in vivo affinity-matured antibodies. A further advantage is the availability of the DNA sequence encoding the phage displayed antibody fragment, which is packaged in the phage particles. Therefore, the selected antibody fragments can be rapidly further engineered in any needed antibody format according to the requirements of the final application. In this review, we present an overview of phage display derived recombinant antibodies against bacterial, viral and eukaryotic pathogens, as well as microbial toxins, intended for diagnostic and therapeutic applications.

Isolation and characterizations of a novel recombinant scFv antibody against exotoxin A of Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is the leading cause of nosocomial infections, especially in people with a compromised immune system. Targeting virulence factors by neutralizing antibodies is a novel paradigm for the treatment of antibiotic-resistant pseudomonas infections. In this respect, exotoxin A is one of the most potent virulence factors in P. aeruginosa. The present study was carried out to identify a novel human scFv antibody against the P. aeruginosa exotoxin A domain I (ExoA-DI) from a human scFv phage library.

METHODS

The recombinant ExoA-DI of P. aeruginosa was expressed in E. coli, purified by Ni-NTA column, and used for screening of human antibody phage library. A novel screening procedure was conducted to prevent the elimination of rare specific clones. The phage clone with high reactivity was evaluated by ELISA and western blot.

RESULTS

Based on the results of polyclonal phage ELISA, the fifth round of biopanning leads to the isolation of several ExoA-DI reactive clones. One positive clone with high affinity was selected by monoclonal phage ELISA and used for antibody expression. The purified scFv showed high reactivity with the recombinant domain I and full-length native exotoxin A.

CONCLUSIONS

The purified anti-exotoxin A scFv displayed high specificity against exotoxin A. The human scFv identified in this study could be the groundwork for developing a novel therapeutic agent to control P. aeruginosa infections.

In Pursuit of Zero 2.0: Recent Developments in Nonfouling Polymer Brushes for Immunoassays

"Nonfouling" polymer brush surfaces can greatly improve the performance of in vitro diagnostic (IVD) assays due to the reduction of nonspecific protein adsorption and consequent improvement of signal-to-noise ratios. The development of synthetic polymer brush architectures that suppress adventitious protein adsorption is reviewed, and their integration into surface plasmon resonance and fluorescent sandwich immunoassay formats is discussed. Also, highlighted is a novel, self-contained immunoassay platform (the D4 assay) that transforms time-consuming laboratory-based assays into a user-friendly and point-of-care format with a sensitivity and specificity comparable or better than standard enzyme-linked immunosorbent assay (ELISA) directly from unprocessed samples. These advancements clearly demonstrate the utility of nonfouling polymer brushes as a substrate for ultrasensitive and robust diagnostic assays that may be suitable for clinical testing, in field and laboratory settings.

Nanobodies in Human Infections: Prevention, Detection, and Treatment

Despite the existence of vaccination, antibiotic therapy, and antibody therapies, infectious diseases still remain as one of the biggest challenges to human health all over the world. Among the different methods for treatment and prevention of infectious diseases, antibodies are well known but poorly developed. There is a new subclass of antibodies calledheavy-chain antibodies that belong to the IgG isotype. However, they are low in molecular weight and lost the first constant domain (CH1). Their single-domain antigen-binding fragments, identified as nanobodies, have unique characteristics, which make them superior in comparison with the conventional antibodies. Low molecular weight and small size, high stability and solubility, ease of expression, good tissue penetration, and low-cost production make nanobodies an appropriate alternative to use against infectious disease. In this research, we review the properties of nanobodies and their potential applications in controlling human infections and inflammations.

mRNA: A Novel Avenue to Antibody Therapy?

First attempts to use exogenous mRNA for protein expression in vivo were made more than 25 years ago. However, widespread appreciation of in vitro transcribed mRNA as a powerful technology for supplying therapeutic proteins to the body has evolved only during the past few years. Various approaches to turning mRNA into a potent therapeutic have been developed. All of them share utilization of specifically designed, rather than endogenous, sequences and thorough purification protocols. Apart from this, there are two fundamental philosophies, one promoting the use of chemically modified nucleotides, the other advocating restriction to unmodified building blocks. Meanwhile, both strategies have received broad support by successful mRNA-based protein treatments in animal models. For such in vivo use, specifically optimized mRNA had to be combined with potent formulations to enable efficient in vivo delivery. The present review analyzes the applicability of mRNA technology to antibody therapy in all main fields: antitoxins, infectious diseases, and oncology.

A new ligand of CD105 screened out by phage display technology provides a reliable identification of recurrent or metastasizing pleomorphic adenoma from pleomorphic adenoma

OBJECTIVES

To assess CD105 expression in pleomorphic adenoma (PA), recurrent pleomorphic adenoma (RPA) and metastasizing pleomorphic adenoma (MPA), to identify new epitopes and screen a ligand with high affinity to CD105 by phage display technology, to evaluate the reliability of the new ligand for identifying RPA/MPA from PA.

METHODS

Phage display technology was used to screen ligands with high affinity to recombinant human CD105. The ligand with strongest affinity to CD105 was synthesized by FMOC Chemistry according to the sequencing results. The archived formalin fixed paraffin-embedded (FFPE) tissues of 35 PA cases, 12 RPA cases and 2 MPA cases were sliced and immunofluorescent stained. CD105 expression were detected by Confocal laser scanning microscopy (CLSM). The relative fluorescence intensity was calculated with the image processing software Image J. Statistical analyses were performed by the software Graph Pad Prism (Version 7.0a). Using PROC logistic, receiver operating characteristic (ROC) curves, area under ROC curves (AUCs) were generated to assess the sensitivity and specificity of the new ligand for identifying RPA/MPA from PA cases.

RESULTS

A ligand with specialty and high affinity to CD105 i.e. ligand nABPK296 were developed. FITC-labeled ligand nABPK296 confirmed the difference of CD105 expression in RPA/MPA and PA. The AUC of nABPK296 was 0.9418.

CONCLUSIONS

CD105 is a promising biomarker for identification of RPA/MPA from PA cases. Ligand nABPK296 provides a promising approach to CD105 detection. This study also validated the reliability of phage display technology in finding new episodes and ligands with high affinity for antigens.