High-affinity Monoclonal Antibody Research Articles

Efficacy and safety of tozorakimab in moderate-to-severe atopic dermatitis: A Phase 2a randomized controlled trial (FRONTIER-2).

Atopic dermatitis (AD) is a chronic, inflammatory skin disease characterized by intense pruritus and eczematous lesions. Tozorakimab is a high-affinity human monoclonal antibody that neutralizes interleukin-33, a broad-acting alarmin cytokine that is over-expressed in keratinocytes of patients with AD. This Phase 2a study (FRONTIER-2; NCT04212169) evaluated the safety and efficacy of tozorakimab in adults with moderate-to-severe AD. FRONTIER-2 was a randomized, placebo-controlled, parallel-group, double-blind study conducted from 9 December 2019 to 20 September 2022 at 32 centres across six countries. Patients were randomized 3:1:1:3 to receive placebo, tozorakimab 60 mg, tozorakimab 300 mg or tozorakimab 600 mg by subcutaneous injection once every 4 weeks for four doses. The primary endpoint was percentage change from baseline to Week 16 in the Eczema Area and Severity Index (EASI) score in patients treated with tozorakimab versus placebo. Secondary outcomes included EASI-75 responders (patients achieving ≥75% reduction from baseline in EASI score), Investigator's Global Assessment (IGA) responders (patients achieving an IGA score of 0 or 1), pharmacokinetics, immunogenicity and safety. Overall, 148 patients were randomized. There was no statistically significant difference in the primary endpoint (60 mg difference of 1.3 [90% confidence interval (CI): -13.7, 16.2], p = 0.888; 300 mg: difference of 5.9 [90% CI: -10.4, 22.1], p = 0.549; 600 mg: difference of - 1.7 [90% CI: -13.4, 10.0], p = 0.807). The proportion of EASI-75 and IGA 0/1 responders at Week 16 was numerically higher in the tozorakimab 600 mg group than in the placebo group (EASI-75: 18.2% vs. 7.1%, p = 0.094; IGA 0/1: 9.1% vs. 1.8%, p = 0.113). Serum pharmacokinetics were dose-dependent, immunogenicity incidence was low and tozorakimab was well tolerated. FRONTIER-2 did not show a statistically significant difference in the primary endpoint for tozorakimab compared with placebo. However, numerical increases in responder rates were observed.

Male fertility is preserved following ixekizumab treatment-a real life pilot study.

Preserving fertility is crucial when managing male patients with spondyloarthritis (SpA) and/or psoriasis (PsO), especially in young men. Chronic inflammation, hormonal dysregulation, and immunosuppressive therapies can negatively impact male fertility. Over the past decades, positive data have emerged regarding the reproductive safety of various therapies in men. Ixekizumab (IXE), a high-affinity monoclonal antibody targeting IL-17A, has shown a safe profile for male fertility in small studies. This pilot study assesses the impact of IXE treatment on sperm parameters in SpA and/or PsO patients in a real-world setting. Consecutive adult male SpA and/or PsO patients eligible for or undergoing IXE treatment were prospectively enrolled. Demographic data, disease characteristics, laboratory assessments, comorbidities, and previous treatments were recorded. Sperm analysis was conducted after a minimum of 6 months of IXE treatment, and also before treatment inititation in a subgroup of patients. Parallel sperm evaluations were performed in a control group of healthy donors. Ten patients were enrolled: 8 with SpA and 2 with PsO. After 6 months of IXE treatment, all patients had normal sperm parameters. One SpA and PsO patient with baseline oligozoospermia showed normal parameters at follow-up and achieved a successful pregnancy post-treatment. Compared with controls, IXE-treated patients had lower sperm concentrations but higher vitality. In our limited size pilot study on SpA and PsO patients, Ixekizumab exposure did not impair male fertility. Sperm parameters remained within normal ranges after a minimum of 6 months of treatment. Early Ixekizumab treatment may preserve or potentially reverse fertility impairment.

Monoclonal antibody targeting CEACAM1 enhanced the response to anti-PD1 immunotherapy in non-small cell lung cancer

Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1), an extensively studied cell surface molecule, mainly expressed by certain epithelial, endothelial, lymphoid and myeloid cells, and is an attractive target for cancer immunotherapy. Here, to investigate the anti-tumor effects and mechanisms of CEACAM1 antibody, we prepared the antibody and explored its anti-tumor effects on Non-small Cell Lung Cancer (NSCLC) in vitro and in vivo. Firstly, antigen of human CEACAM1 recombinant protein was immunized on BALB/c mice and the high-affinity mouse anti-human monoclonal antibody 3C11 was selected by hybridoma technique. Next, ELISA was applied to detect the blocking effects of 3C11 on CEACAM1-CEACAM1 and CEACAM1-CEACAM5. Then, cell assays and ELISA were used to evaluate the role of 3C11 in blocking CEACAM1-CEACAM1 immunosuppressive signal transduction between dendritic cells (DCs) and T cells or natural killer cells (NK) and tumor cells. Finally, the synergistic anti-tumor effect of 3C11 combined with anti-PD-1 antibody was evaluated through cell stimulation assays and NCI-H358-induced tumor models in mice. The results showed the EC50 of 3C11 binding to NCI-H358 or exhausted T cells were 0.04971 μg/mL and 0.03475 μg/mL, respectively. 3C11 activated the exhausted T cells and enhanced the killing effect of NK by blocking CEACAM1-CEACAM1. In addition, the combination of 3C11 and anti-PD1 antibody produced synergistic anti-tumor effect on NSCLC. Its improved tumor growth inhibition value (TGI) of anti-PD-1 from 18 % to 85 % in vivo. These findings suggest that 3C11 can be considered an effective immunotherapy drug for NSCLC.

Humanized recombinant immunotoxin targeting hCG demonstrates therapeutic potential for advanced stage difficult to treat cancers

We report the development of an immunotherapeutic molecule, a Humanized immunotoxin, for treating hCG-expressing advanced-stage cancers. PiPP, a high-affinity anti-hCG monoclonal antibody, is used in the immunotoxin for ‘homing’ hCG-positive cancer cells. The deimmunized (DI) form of α-Sarcin, a fungal-origin toxin that lacks functional T-cell epitopes, is used in the design to ensure minimal immunogenicity of the immunotoxin for repetitive use in humans. A single-chain variable fragment (scFv) of PiPP was constructed by linking the Humanized VH and VL regions of the antibody. The scFv part of the antibody was further linked to the toxin α-Sarcin (DI) at the gene level and expressed as a recombinant protein in E. coli. The immunotoxin was purified from the bacterial cell lysate and analysed for binding and cytotoxicity to hCG-secreting colorectal and pancreatic cancer cells. The results showed that the scFv(PiPP)-Sarcin immunotoxin was able to bind to colorectal and pancreatic cancer cells and killed approximately 85% of the cells. In vivo testing of the immunotoxin produced results similar to those of in vitro testing against colorectal adenocarcinoma-induced tumours. This immunotoxin could be a promising immunotherapeutic agent for treating colorectal, pancreatic and other terminal-stage hCG-expressing cancers.

High-affinity antibodies specific to the core region of the tau protein exhibit diagnostic and therapeutic potential for Alzheimer’s disease

BackgroundRecent advances in blood-based biomarker discovery are paving the way for simpler, more accessible diagnostic tools that can detect early signs of Alzheimer’s disease (AD). Recent successes in the development of amyloid-targeting immunotherapy approaches mark an important advancement in providing new options for the treatment of AD. We have developed a set of high-affinity monoclonal antibodies (mAbs) to tau protein that have the potential as tools for diagnosis and treatment of AD.MethodsSheep were immunised with either full-length tau (1-441) or truncated paired helical filament (PHF)-core tau (297–391). A stringent bio-panning and epitope selection strategy, with a particular focus directed to epitopes within the disease-relevant PHF-core tau, was used to identify single-chain antibodies (scAbs). These scAbs were ranked by affinity for each epitope class, with leads converted to high-affinity mAbs. These antibodies and their potential utility were assessed by their performance in tau immunoassays, as well as their ability to prevent tau aggregation and propagation. Further characterisation of these antibodies was performed by immunohistochemical staining of brain sections and immuno-gold electronmicroscopy of isolated PHFs.ResultsOur work resulted in a set of high-affinity antibodies reacting with multiple epitopes spanning the entire tau protein molecule. The tau antibodies directed against the core tau unit of the PHF inhibited pathological aggregation and seeding using several biochemical and cell assay systems. Through staining of brain sections and PHFs, the panel of antibodies revealed which tau epitopes were available, truncated, or occluded. In addition, highly sensitive immunoassays were developed with the ability to distinguish between and quantify various tau fragments.ConclusionThis article introduces an alternative immunodiagnostic approach based on the concept of a “tauosome” – the diverse set of tau fragments present within biological fluids. The development of an antibody panel that can distinguish a range of different tau fragments provides the basis for a novel approach to potential diagnosis and monitoring of disease progression. Our results further support the notion that tau immunotherapy targeting the PHF-core needs to combine appropriate selection of both the target epitope and antibody affinity to optimise therapeutic potential.

Preparation and Construction of Chimeric Humanized Broadly Reactive Antibody 10H10 to Protein E of Tick-Borne Encephalitis Virus.

A full-length humanized chimeric antibody 10H10ch that specifically interacts with the surface glycoprotein E of flaviviruses was obtained. To construct it, we used variable fragments of the heavy and light chains of the monoclonal antibody 10H10 that form the active center of the antibody and a fragment of the constant part of the heavy chain of the human IgG1 antibody. The resulting full-length chimeric humanized antibody 10H10ch specifically interacted with the E protein of flaviviruses pathogenic to humans, such as tick-borne encephalitis, Zika, West Nile, and dengue viruses. An immunochemical assessment of the interaction constants of the 10H10ch antibody with a panel of native and recombinant flavivirus antigens by ELISA and biolayer interferometry showed that the dissociation constant (Kd) of the chimeric antibody is in the nanomolar region and is comparable to that of the high-affinity mouse monoclonal antibody 10H10. The possibility of using the resulting chimeric humanized antibody 10H10ch for the diagnosis, prevention, and treatment of various flavivirus infections is discussed.

Differential detection of SARS-CoV-2 variants and influenza A viruses utilizing a dual lateral flow strip based on colloidal gold-labeled monoclonal antibodies

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the seasonal influenza virus are spreading among humans concurrently, especially with the ongoing replacement of mutant strains. It is challenging to differentiate between symptoms for therapy due to the comparable symptoms following infection with the SARS-CoV-2 variants and influenza viruses. Meanwhile, in order to achieve rapid point-of-care testing (POCT) to manage the spread of the disease, we developed a dual lateral flow strip based on colloidal gold-labeled monoclonal antibodies that can perform differential detection of SARS-CoV-2 variants and influenza A viruses (IAV) in this study. High-affinity monoclonal antibodies (mAbs) targeting SARS-CoV-2 and IAV were prepared to capture antigens and labeled with colloidal gold nanoparticles (AuNPs). Based on high-affinity mAbs, two targets were immobilized on one nitrocellulose (NC) membrane to establish the lateral flow strip (LFS) for differential diagnosis of SARS-CoV-2 and IAV. With no reactivity to other viruses, this LFS is extremely specific and can only identify SARS-CoV-2 and IAV. The LFS showed a limit of detection (LOD) of 4.88 ng/mL for the Omicron BA.2 RBD protein and 2.44 ng/mL for the nucleoprotein (NP) protein of H1N1. When analyzing 16 SARS-CoV-2 positive clinical samples, eight IAV positive clinical samples, and six negative samples that had already been pre-confirmed by commercial kits, its clinical application is effectively and accurately proven. These results demonstrated that the LFS integrated with AuNPs has great potential to facilitate quick, easy, and reliable POCT diagnosis for promoting the control of infectious diseases.

MEDI1814 selectively reduces free Aβ42 in cerebrospinal fluid of non-clinical species and Alzheimer's disease patients.

Small molecules and antibodies are being developed to lower amyloid beta (Aβ) peptides. We describe MEDI1814, a fully human high-affinity monoclonal antibody selective for Aβ42, the pathogenic self-aggregating species of Aβ. MEDI1814 reduces free Aβ42 without impacting Aβ40 in the cerebrospinal fluid of rats and cynomolgus monkeys after systemic administration. MEDI1814 administration to patients with Alzheimer's disease (AD; n=57) in single or repeat doses up to 1800mg intravenously or 200mg subcutaneously was associated with a favorable safety and tolerability profile. No cases of amyloid-related imaging abnormalities were observed. Predictable dose-proportional changes in serum exposures for MEDI1814 were observed across cohorts. Cerebrospinal fluid (CSF) analysis demonstrated central nervous system penetration of MEDI1814. Pharmacodynamic data showed dose-dependent suppression of free Aβ42, increases in total (bound and free) Aβ42, but no change in total Aβ40 in CSF across doses. MEDI1814 offers a differentiated approach to impacting Aβ in AD via selective reduction of free Aβ42.

Advancing SARS‐CoV‐2 Variant Detection with High Affinity Monoclonal Antibodies and Plasmonic Nanostructure

AbstractA nanoplasmonic biosensor for the precise detection of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) by leveraging advances in nanostructured sensing materials and highly selective monoclonal antibodies is presented. The sensor integrates plasmonic Au nanostructures optimized for surface‐enhanced Raman scattering (SERS), enhancing sensitivity through unique light interactions at the nanoscale. Coupled with exclusive antibodies that specifically target SARS‐CoV‐2 and its evolving variants, this sensor demonstrates remarkable selectivity and versatility. Validated with 270 clinical samples, it demonstrates a sensitivity of 98.9% and specificity of 100%. More importantly, the virus in nasopharyngeal swab samples collected over 3 years, marking the long‐term, large‐scale clinical validation of the nanoplasmonic biosensor for SARS‐CoV‐2 is been successfully detected. Furthermore, the integration of this sensor with face masks enables the detection of airborne SARS‐CoV‐2, highlighting its potential for routine management of coronavirus disease 2019 (COVID‐19).

Evaluation of High-Affinity Monoclonal Antibodies and Antibody-Drug Conjugates by Homogenous Time-Resolved FRET.

The rapid growth of therapeutic monoclonal antibodies demands greater accessibility to scalable methods of evaluating antigen binding. Homogenous TR-FRET is ideal for preliminary screening but has not been reported to assay these interactions due to their high-affinity and complex solution-phase kinetics. Here we report the development of a competition assay to rank-order the relative affinities of these drugs for a common antigen. The assay is compatible with automation, requires no modification of the analytes, and measures affinities as low as single-digit picomolar. We further demonstrate applications to inform the development of antibody-drug conjugates. The assay may aid discovery and manufacturing of therapeutic antibodies as a low-cost, high-throughput alternative to existing technologies.

Function-first discovery of high affinity monoclonal antibodies using Nanovial-based plasma B cell screening.

Antibody discovery technologies, essential for research and therapeutic applications, have evolved significantly since the development of hybridoma technology. Various in vitro (display) and in vivo (animal immunization and B cell-sequencing) workflows have led to the discovery of antibodies against diverse antigens. Despite this success, standard display and B-cell sequencing-based technologies are limited to targets that can be produced in a soluble form. This limitation inhibits the screening of function-inducing antibodies, which require the target to be expressed in cells to monitor function or signaling, and antibodies targeting proteins that maintain their physiological structure only when expressed on cell membranes, such as G-protein coupled receptors (GPCRs). A high-throughput two-cell screening workflow, which localizes an antibody-secreting cell (ASC) and a cell expressing the target protein in a microenvironment, can overcome these challenges. To make function-first plasma cell-based antibody discovery accessible and scalable, we developed hydrogel Nanovials that can capture single plasma cells, target-expressing cells, and plasma cell secretions (antibodies). The detection and isolation of Nanovials harboring the antigen-specific plasma cells are then carried out using a flow cytometry cell sorter - an instrument that is available in most academic centers and biopharmaceutical companies. The antibody discovery workflow employing Nanovials was first validated in the context of two different cell membrane-associated antigens produced in recombinant form. We analyzed over 40,000 plasma cells over two campaigns and were able to identify a diversity of binders that i) exhibited high affinity (picomolar) binding, ii) targeted multiple non-overlapping epitopes and iii) demonstrated high developability scores. A campaign using the two-cell assay targeting the immune checkpoint membrane protein PD-1 yielded cell binders with similar EC50s to clinically used Pembrolizumab and Nivolumab. The highest selectivity for binders was observed for sorted events corresponding with the highest signal bound to target cells on Nanovials. Overall, Nanovials can provide a strong foundation for function-first antibody discovery, yielding direct cell binding information and quantitative data on prioritization of hits with flexibility for additional functional readouts in the future.

Evaluation of High-Affinity Monoclonal Antibodies and Antibody-Drug Conjugates by Homogenous Time-Resolved FRET.

The rapid growth of therapeutic monoclonal antibodies demands greater accessibility to scalable methods of evaluating antigen binding. Homogenous TR-FRET is ideal for preliminary screening but has not been reported to assay these interactions due to their high-affinity and complex solution-phase kinetics. Here we report the development of a competition assay to rank-order the relative affinities of these drugs for a common antigen. The assay is compatible with automation, requires no modification of the analytes, and measures affinities as low as single-digit picomolar. We further demonstrate applications to inform the development of antibody-drug conjugates. The assay may aid discovery and manufacturing of therapeutic antibodies as a low-cost, high-throughput alternative to existing technologies.

Preclinical Efficacy of VTX-0811: A Humanized First-in-Class PSGL-1 mAb Targeting TAMs to Suppress Tumor Growth.

Omnipresent suppressive myeloid populations in the tumor microenvironment limit the efficacy of T-cell-directed immunotherapies, become more inhibitory after administration of T-cell checkpoint inhibitors, and are overall associated with worse survival of cancer patients. In early clinical trials, positive outcomes have been demonstrated for therapies aimed at repolarizing suppressive myeloid populations in the tumor microenvironment. We have previously described the key role of P-selectin glycoprotein ligand-1 (PSGL-1) in maintaining an inhibitory state of tumor-associated macrophages (TAMs), most of which express high levels of PSGL-1. Here we describe a novel, first-in-class humanized high-affinity monoclonal antibody VTX-0811 that repolarizes human macrophages from an M2-suppressive phenotype towards an M1 inflammatory phenotype, similar to siRNA-mediated knockdown of PSGL-1. VTX-0811 binds to PSGL-1 of human and cynomolgus macaque origins without inhibiting PSGL-1 interaction with P- and L-Selectins or VISTA. In multi-cellular assays and in patient-derived human tumor cultures, VTX-0811 leads to the induction of pro-inflammatory mediators. RNAseq data from VTX-0811 treated ex vivo tumor cultures and M2c macrophages show similar pathways being modulated, indicating that the mechanism of action translates from isolated macrophages to tumors. A chimeric version of VTX-0811, consisting of the parental murine antibody in a human IgG4 backbone, inhibits tumor growth in a humanized mouse model of cancer. VTX-0811 is exceptionally well tolerated in NHP toxicology assessment and is heading into clinical evaluation after successful IND clearance.

Establishment and application of PDCoV antigen-specific DAS-ELISA detection method

BackgroundPorcine deltacoronavirus (PDCoV) is a swine enteropathogenic coronavirus that affects young pigs, causing vomiting, acute diarrhea, dehydration, and even death. There is growing evidence that PDCoV can undergo cross-species as well as zoonotic transmissions. Due to the frequent outbreaks of this deadly virus, early detection is essential for effective prevention and control. Therefore, developing a more convenient and reliable method for PDCoV detection is the need of the hour.ResultsThis study utilized a high-affinity monoclonal antibody as the capture antibody and a horseradish peroxidase labeled polyclonal antibody as the detection antibody to develop an enzyme-linked immunosorbent assay (DAS-ELSA) for PDCoV detection.Both antibodies target the PDCoV nucleocapsid (N) protein. The findings of this study revealed that DAS-ELISA was highly specific to PDCoV and did not cross-react with other viruses to cause swine diarrhea. The limit of detection of the virus titer using this method was 103 TCID50/mL of PDCoV particles. The results of a parallel analysis of 239 known pig samples revealed a coincidence rate of 97.07% (κ = 0.922) using DAS-ELISA and reverse transcriptase PCR (RT-PCR). The DAS-ELISA was used to measure the one-step growth curve of PDCoV in LLC-PK cells and the tissue distribution of PDCoV in infected piglets. The study found that the DAS-ELISA was comparable in accuracy to the TCID50 method while measuring the one-step growth curve. Furthermore, the tissue distribution measured by DAS-ELISA was also consistent with the qRT-PCR method.ConclusionThe developed DAS-ELISA method can be conveniently used for the early clinical detection of PDCoV infection in pigs, and it may also serve as an alternative method for laboratory testing of PDCoV.

A targetable secreted neural protein drives pancreatic cancer metastatic colonization and HIF1a nuclear retention.

Pancreatic ductal adenocarcinoma (PDAC) is an increasingly diagnosed cancer that kills 90% of afflicted patients, with most patients receiving palliative chemotherapy. We identified neuronal pentraxin 1 (NPTX1) as a cancer secreted protein that becomes over-expressed in human and murine PDAC cells during metastatic progression and identified adhesion molecule with Ig like domain 2 (AMIGO2) as its receptor. Molecular, genetic, biochemical and pharmacologic experiments revealed that secreted NPTX1 acts cell-autonomously on the AMIGO2 receptor to drive PDAC metastatic colonization of the liver-the primary site of PDAC metastasis. NPTX1-AMIGO2 signaling enhanced hypoxic growth and was critically required for hypoxia induced factor-1a (HIF1a) nuclear retention and function. NPTX1 is over-expressed in human PDAC tumors and upregulated in liver metastases. Therapeutic targeting of NPTX1 with a high-affinity monoclonal antibody substantially reduced PDAC liver metastatic colonization. We thus identify NPTX1-AMIGO2 as druggable critical upstream regulators of the HIF1a hypoxic response in PDAC.

The Impact of Lebrikizumab on Vaccine-Induced Immune Responses: Results from a Phase3 Study in Adult Patients with Moderate-to-Severe Atopic Dermatitis.

Lebrikizumab, a high-affinity IgG4 monoclonal antibody that selectively inhibits interleukin-13 with high binding affinity and slow dissociation rate, prevents the formation of the interleukin-4Rα/interleukin-13Rα1heterodimer receptor signaling complex. Here we report the impact of lebrikizumab on responses to two non-live vaccines in adult patients with moderate-to-severe atopic dermatitis (AD). ADopt-VA (NCT04626297) was a double-blind, placebo-controlled, parallel-group, 16-week, phase3 randomized study to assess the impact of lebrikizumab treatment on non-live vaccine immune responses, and efficacy and safety of lebrikizumab compared with placebo. Eligible patients included adults from 18 to 55years of age with moderate-to-severe chronic AD who were randomly assigned 1:1 to lebrikizumab 250mg every 2weeks or placebo and stratified according to disease severity. The primary endpoints were the development of a booster response to tetanus toxoid and a positive antibody response to meningococcal conjugate vaccine (MCV), 4weeks after administration of the corresponding vaccine. At week16, 73.6% of patients in the lebrikizumab group (n = 78/106) achieved Tdap booster response compared with 73.4% of patients in the placebo group (n = 58/79). MCV vaccine response was observed in 86.9% of patients in the lebrikizumab group (n = 86/99) and 75.0% of patients in the placebo group (n = 60/80). At week16, IGA0,1 with ≥ 2-point improvement from baseline was achieved by 40.6% (n = 51/125) of patients treated with lebrikizumab and 18.9% (n = 23/122) of patients who received placebo (p < 0.001). There was a higher proportion of patients achieving EASI75 at week16 in the lebrikizumab-treated patients (58.0%, n = 72/125) compared with placebo (32.7%, n = 40/122, p < 0.001). Treatment with lebrikizumab did not impact response to non-live vaccines Tdap and MCV in this study. Lebrikizumab treatment had a significant degree of efficacy compared to placebo across multiple endpoints. ClinicalTrials.gov identifier NCT04626297.

A high affinity monoclonal antibody against HLA-E-VL9 enhances natural killer cell anti-tumor killing.

A high affinity monoclonal antibody against HLA-E-VL9 enhances natural killer cell anti-tumor killing by checkpoint inhibition and antibody dependent cellular cytotoxicity.

Development of a single-chain variable antibody fragment against a conserved region of the SARS-CoV-2 spike protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has prolonged the duration of the pandemic because of the continuous emergence of new variant strains. The emergence of these mutant strains makes it difficult to detect the virus with the existing antibodies; thus, the development of novel antibodies that can target both the variants as well as the original strain is necessary. In this study, we generated a high-affinity monoclonal antibody (5G2) against the highly conserved region of the SARS-CoV-2 spike protein to detect the protein variants. Moreover, we generated its single-chain variable antibody fragment (sc5G2). The sc5G2 expressed in mammalian and bacterial cells detected the spike protein of the original SARS-CoV-2 and variant strains. The resulting sc5G2 will be a useful tool to detect the original SARS-CoV-2 and variant strains.

A highly sensitive electrochemical immunosensor based on rGO-PEI-Ag nanocomposites for the detection of tilmicosin

A label-free electrochemical immunosensor was developed to rapidly detect tilmicosin (TMC) residues in pork and milk. The immunosensor was constructed by immobilizing a high-affinity monoclonal antibody against TMC on an rGO-PEI-Ag nanocomposite-modified electrode. The rGO-PEI-Ag nanocomposites were prepared by mixing polyethyleneimine (PEI) modified reduced graphene oxide (rGO) with AgNO3 solution. The prepared rGO-PEI-Ag nanocomposites showed good redox activity and conductivity, as characterized by ultraviolet-visible spectroscopy (UV–Vis), transmission electron microscopy (TEM), and X-ray diffraction (XRD). During the preparation process, staphylococcal protein A (SPA) was added to targetedly bind the Fc segment of the monoclonal antibody. The immunosensor showed a low detection limit (LOD) of 0.0013 ng/mL, a linear range of 0.01–100 ng/mL, and recoveries ranging from 92.77 to 100.02% in pork and 92.26–101.23% in milk. Furthermore, the immunosensor exhibited good stability, reproducibility, and specificity in detecting TMC in pork and milk real samples.

High-affinity monoclonal antibodies against the porcine epidemic diarrhea virus S1 protein

The porcine epidemic diarrhea virus (PEDV) infection inflicted substantial economic losses upon the global pig-breeding industry. This pathogen can infect all pigs and poses a particularly high fatality risk for suckling piglets. The S1 subunit of spike protein is a crucial target protein for inducing the particularly neutralizing antibodies that can intercept the virus-host interaction and neutralize virus infectivity. In the present study, the HEK293F eukaryotic expression system was successfully utilized to express and produce recombinant S1 protein. Through quantitative analysis, five monoclonal antibodies (mAbs) specifically targeting the recombinant S1 protein of PEDV were developed and subsequently evaluated using enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), and flow cytometry assay (FCA). The results indicate that all five mAbs belong to the IgG1 isotype, and their half-maximal effective concentration (EC50) values measured at 84.77, 7.42, 0.89, 14.64, and 7.86 pM. All these five mAbs can be utilized in ELISA, FCA, and IFA for the detection of PEDV infection. MAb 5-F9 exhibits the highest sensitivity to detect as low as 0.3125 ng/mL of recombinant PEDV-S1 protein in ELISA, while only 0.096 ng/mL of mAb 5-F9 is required to detect PEDV in FCA. The results from antigen epitope analysis indicated that mAb 8-G2 is the sole antibody capable of recognizing linear epitopes. In conclusion, this study has yielded a highly immunogenic S1 protein and five high-affinity mAbs specifically targeting the S1 protein. These findings have significant implications for early detection of PEDV infection and provide a solid foundation for further investigation into studying virus-host interactions.