Search Results (179)

Background/Objectives: Tumor-associated antigens are not tumor-specific antigens but proteins that are overexpressed by tumor cells and also weakly expressed at the surface of healthy tissues. Therefore, some side effects are observed when targeted by therapeutic antibodies, a phenomenon named “on-target, off-tumor toxicity”. As tumors generate an acidic microenvironment, we investigated whether we could generate pH-dependent antibodies to increase their tumor specificity. For this proof-of-concept study, we selected the tyrosine kinase receptor AXL because we already developed several antibodies against this target. Methods: To generate a pH-dependent anti-AXL antibody, we performed classical panning of a single-chain variable fragment (scFv) library using phage display at an acidic pH throughout the process. Results: After the third round of panning, 9 scFvs, among the 96 picked clones, bound to AXL at acidic pH and showed very low binding at a neutral pH. After reformatting them into IgG, two clones were selected for further study due to their strong pH-sensitive binding. Using molecular docking and alanine scanning, we found that their binding strongly depended on two histidine residues present on AXL at positions 61 and 116. Conclusions: To conclude, we set-up an easy process to generate pH-dependent antibodies that may increase their tumor-binding specificity and potentially decrease toxicity towards healthy tissues. Full article

Sepsis is a fetal disease that requires a clear diagnostic biomarker for timely antibiotic treatment. Recent research has identified a pyroptosis-inducing epitope known as P5-5 in tetranectin (TN), a plasma protein produced by monocytes. Previously, we produced a 12F1 monoclonal antibody against the P5-5 and discovered that it could not only diagnose the presence but also monitor the progress of sepsis in the clinic. In the current study, we further investigated the structure site of the P5-5 and the recognition mechanism between the 12F1 mAb and the P5-5 epitope. To this end, 10 amino acids (NDALYEYLRQ) in the P5-5 were individually mutated to alanine, and their binding to the mAb was tested to confirm the most significant antigenic recognition sites. In the meanwhile, the spatial conformation of 12F1 mAb variable regions was modeled, and the molecular recognition mechanisms in detail of the mAb to the P5-5 epitope were further studied by molecular docking. Following epitope prediction and experimental verification, we demonstrated that the motif “DALYEYL” in the epitope sequence position 2−8 of TN-P5-5 is the major binding region for mAb recognition, in which two residues (4L and 8L) were essential for the interaction between the P5-5 epitope and the 12F1 mAb. Therefore, our study greatly narrowed down the previously reported motif from ten to seven amino acids and identified two Leu as critical contact residues. Finally, a single-chain variable fragment (scFv) from the 12F1 hybridoma was constructed, and it was confirmed that the identified motif and residues are prerequisites for the strong binding between P5-5 and 12F1. Altogether, the data of the present work could serve as a theoretic guide for the clinical design of biosynthetic drugs by artificial intelligence to treat sepsis. Full article

Phospholipase A1 (Ves a 1), a major toxin from Vespa affinis venom, poses significant risks to allergic individuals. Nevertheless, the epitope determinants of Ves a 1 have not been characterized. Thus, identifying its linear B-cell epitopes is crucial for understanding envenomation mechanisms. In this study, we predicted and identified B-cell epitopes EP5 and EP6 as potential candidates. EP5 formed an α-helix at the active site of Ves a 1, whereas EP6 adopted an extended loop conformation. Both synthetic peptides were synthesized and evaluated for their inhibitory effects using immune-inhibitory assays with polyclonal antibodies (pAbs) targeting both native (nVes a 1) and recombinant (rVes a 1) forms. The Ves a 1 polyclonal antibodies (pAb-nVes a 1 and pAb-Ves a 1) were produced, and their specificity binding to Ves a 1 was confirmed by Western blot. Next, ELISA inhibition assays showed that EP5 and EP6 significantly blocked pAb binding to both nVes a 1 and rVes a 1. Dot blot and Western blot assays supported these findings, particularly with stronger inhibition toward rVes a 1. Furthermore, enzymatic assays indicated that nVes a 1 and rVes a 1 retained phospholipase activity. Immunoinformatics docking showed that EP5 and EP6 specifically bind to a single-chain variable fragment antibody (scFv) targeting Naja naja PLA2. Molecular analysis revealed similar amino acid interactions to the template, suggesting effective paratope–epitope binding. These results support the potential of EP5 and EP6 for future diagnosis and therapy of V. affinis venom allergy. Full article

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease characterized by tissue damage in multiple organs caused by autoantibodies and the resulting immune complexes. One possible way for complement system contribution to onset of autoimmune disorder could be realized by the impairment of C1q-mediated apoptotic clearance as part of human homeostasis. The capacity of C1q to bind early apoptotic cells could be decreased or even lost in the presence of anti-C1q antibodies. A monoclonal anti-idiotypic single-chain (scFv) antibody was selected from the phage library Griffin1” to recognize anti-C1q autoantibodies, purified from sera of lupus nephritis patients. Lupus-prone MRL/lpr mice were injected weekly with scFv A1 fragment-binding anti-C1q antibodies. The number of in vitro and ex vivo studies with collected cells, sera, and organs from the treated animals was performed. scFv treatment changed the percentage of different B-, T-, and NK-cell subpopulations as well as plasma cells and plasmablasts in the spleen and bone marrow. An increase in the levels of splenocyte proliferation, anti-C1q antibodies, and the number of plasma cells producing anti-dsDNA and anti-C1q antibodies were also observed in scFv-treated animals. High levels of proteinuria and hematuria combined with unstable levels of IL10 and IFNγ promote the development of severe lupus and shorten the survival of treated MRL/lpr mice. Therapy with the scFv A1 antibody resulted in BCR recognition on the surface of anti-C1q-specific B-cells and had a disease progression effect, enhancing lupus symptoms in the MRL/lpr mouse model of SLE. Full article

Background: Human cytomegalovirus (CMV) is a major pathogen that poses significant risks to immunocompromised individuals and neonates. The tegument protein pp71, encoded by the UL82 gene, plays a pivotal role in initiating viral lytic replication and evading host immune responses. Despite its clinical relevance, standardized monoclonal antibodies (mAbs) for pp71 remain limited, prompting the need to expand the available repertoire of antibodies targeting this critical protein. Methods: In this study, we constructed a diverse human single-chain variable fragment (scFv) library using RNA derived from the B cells of four healthy donors. The library was expressed in Saccharomyces cerevisiae, and iterative rounds of magnetic-activated cell sorting (MACS) were performed against recombinant pp71. Clonal enrichment was monitored using flow cytometry. Results: Among the isolated clones, one designated ID2 exhibited high sensitivity and specificity for pp71, as demonstrated by flow cytometry, immunofluorescence, an enzyme-linked immunosorbent assay (ELISA), and biolayer interferometry (BLI). Conclusions: Collectively, these findings establish a novel pp71-specific mAb and underscore the utility of yeast surface display combined with MACS for expanding the antibody toolkit available for CMV research and diagnostics. Full article

Background/Objectives: Esophageal squamous cell carcinoma (ESCC) is a common form of esophageal cancer with a poor prognosis and limited treatment options. Epidermal growth factor receptor (EGFR), an overexpressed oncogenic gene in all ESCC patients, is an attractive target for developing therapies against ESCC. There is an extremely urgent need to develop immunotherapy tools targeting EGFR for the treatment of ESCC. Methods: In this study, we developed human Interleukin-21 (hIL-21)-armed, chimeric-antigen-receptor-modified T (CAR-T) cells targeting EGFR as a new therapeutic approach. The CAR contains a variable domain of the llama heavy chain of heavy-chain antibodies (VHHs), also known as nanobodies (Nbs), as a promising substitute for the commonly used single-chain variable fragment (ScFv) for CAR-T development. Results: We show that nanobody-derived, EGFR-targeting CAR-T cells specifically kill EGFR-positive esophageal cancer cells in vitro and in animal models. Human IL-21 expression in CAR-T cells further improved their expansion and antitumor ability and were observed to secrete more interferon-gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and Interleukin-2 (IL-2) when co-cultured with ESCC cell lines in vitro. More CD8⁺ CAR-T cells and CD3⁺CD8⁺CD45RO⁺CD62L⁺ central memory T cells were detected in CAR-T cells expressing hIL-21 cells. Notably, hIL-21-expressing CAR-T cells showed superior antitumor activity in vivo in a KYSE-150 xenograft mouse model. Conclusions: Our results show that hIL-21-armed, nanobody-derived, EGFR-specific CAR-T cell therapy is a highly promising option for treating ESCC patients. Full article

Chronic pain affects a significant portion of the population, with fewer than 30% achieving adequate relief from existing treatments. This study describes the humanization methodology and characterization of an effective non-opioid single-chain fragment variable (scFv) biologic that reverses pain-related behaviors, in this case by targeting P2X4. After nerve injury, ATP release activates/upregulates P2X4 receptors (P2X4R) sequestered in late endosomes, triggering a cascade of chronic pain-related events. Nine humanized scFv (hscFv) variants targeting a specific extracellular 13-amino-acid peptide fragment of human P2X4R were generated via CDR grafting. ELISA analysis revealed nanomolar binding affinities, with most humanized molecules exhibiting comparable or superior affinity compared to the original murine antibody. Octet measurements confirmed that the lead, HC3-LC3, exhibited nanomolar binding kinetics (KD = 2.5 × 10⁻⁹ M). In vivo functional validation with P2X4R hscFv reversed nerve injury-induced chronic pain-related behaviors with a single dose (0.4 mg/kg, intraperitoneal) within two weeks. The return to naïve baseline remained durably reduced > 100 days. In independent confirmation, the spared nerve injury (SNI) model was similarly reduced. This constitutes an original method whereby durable reversals of chronic nerve injury pain, anxiety and depression measures are accomplished. Full article

Tau pathology is one of the main pathological features of Alzheimer’s disease (AD). Intracellular Tau may be released to the extracellular space upon neuron degeneration, where it has the potential to be toxic to other neurons. The propagation of Tau pathology, mediated by extracellular Tau aggregates, may underlie the pathogenesis of AD. Antibody therapies targeting Tau proteins are, therefore, considered highly promising. In this study, the cytotoxicity of extracellular Tau aggregates on SH-SY5Y cells was examined. The effect of extracellular Tau aggregates on intracellular Tau aggregation was also studied using a FRET-based assay. The extracellular Tau aggregates were found to cause intracellular Tau aggregation after entering the cells; meanwhile, ROS (reactive oxygen species) induced by Tau aggregates facilitated this process. A single-chain variable fragment antibody (scFv T1) inhibits Tau aggregation both extracellularly and intracellularly. ScFv T1 also inhibited the accumulation of ROS and alleviated the inflammation and apoptosis induced by Tau aggregates. These findings could provide experimental support for the study of neurotoxicity and related mechanisms of extracellular Tau aggregates, in addition to providing insights into the development of novel therapeutic agents to treat AD. Full article

The Wnt signalling pathway plays a crucial role in tissue homeostasis and cancer biology due to its regulation of cellular processes, including proliferation, migration, and stem cell activity. Frizzled receptor 7 (FZD7) (a member of the F-class G protein-coupled receptors) has emerged as a key Wnt receptor within this pathway, which is elevated in several human malignancies. FZD7 is notably upregulated in gastrointestinal, breast, pancreatic, and hepatocellular carcinomas and transmits oncogenic Wnt signalling through canonical and non-canonical pathways. FZD7 promotes tumour initiation, and emerging evidence implicates FZD7 in cancer stem cell maintenance and epithelial–mesenchymal transition (EMT), reinforcing its role in metastasis. Therapeutic strategies targeting FZD7 have shown promise, including FZD7-specific monoclonal antibody-drug conjugates (ADCs), human single-chain fragment variable (scFVs) antibodies, and nanoparticles. Notably, our recent development of FZD7-ADC has demonstrated tumour-selective cytotoxicity with reduced off-target effects, positioning FZD7 as an attractive therapeutic target. Additionally, nanoparticle-based drug delivery systems have enhanced the precision of existing chemotherapies by targeting FZD7-expressing tumour cells. Despite significant advances, clinical translation remains a challenge due to potential on-target toxicity and the complexity of tumour microenvironments. Future research should focus on optimising delivery systems, refining antibody specificity, and conducting comprehensive preclinical and clinical trials. This review will focus on novel discoveries regarding FZD7 in cancer and provide an update on our original review on this subject in 2016. Additionally, we present new figures generated by our group using the publicly available Pan-Cancer Atlas RNAseq datasets, highlighting FZD7 expression patterns in patient samples. This integrated approach aims to provide updated insights into the function of FZD7 during cancer and its growing status as an attractive target for therapy. In summary, FZD7 stands out as a promising molecular target in cancer therapy due to its selective overexpression in tumours, functional role in Wnt-driven oncogenesis, and potential for innovative therapeutic applications. This review underscores the critical need for the continued exploration of FZD7-targeted therapies to improve patient outcomes in cancer treatment. Full article

Cardiovascular diseases, including thrombosis, are the leading cause of mortality worldwide. The generation of monoclonal antibodies (mAb) targeting specific coagulation factors could provide more targeted and safer anticoagulant therapies. Factor V (FV) is a critical cofactor in the prothrombinase complex, which catalyzes the conversion of prothrombin to thrombin, a key enzyme in the coagulation cascade. We isolated a novel human antibody specific to FV by using phage display technology. The selection occurred by panning a large repertoire of phages expressing human antibody fragments (scFv) in parallel on the purified recombinant protein in its native form (FV) or activated by proteolytic maturation (Factor Va (FVa)). Through ELISA screening, we identified the clone with the highest binding affinity for both targets, and it was successfully converted into IgG1. The novel human mAb, called D9, was found capable of binding to Factor V with a low nM affinity both by ELISA and BLI assays, whereas its cross-reactivity with some other coagulation factors was found null or very poor. Furthermore, when tested in blood clotting tests, it was found able to prolong activated partial thromboplastin time (aPTT). Thus, D9 could become not only a potential therapeutic agent as a specific anticoagulant but also a precious tool for diagnostic and research applications. Full article

Background: Monoclonal antibodies (mAbs) are potent treatment options for infectious diseases. The rapid isolation and in vivo validation of therapeutic mAb candidates, including mAb cocktails, are essential to combat novel or rapidly mutating pathogens. The rapid selection and production of mAb candidates in sufficient amount and quality for preclinical studies are a major limiting step in the mAb development pipeline. Methods: Here, we developed a method to facilitate the screening of therapeutic mAbs in mouse models. Four conventional mAbs were transformed into single-chain variable fragments fused to the fragment crystallizable (Fc) region of a human IgG1 (scFv-IgG). These scFv-IgG were expressed individually or as a cocktail in vitro and in mice following transfection or hydrodynamic delivery of the corresponding plasmids. Results: This method induced high expression of all scFv-IgG and provided protection in two murine infection models. Conclusions: This study highlights the benefits of this approach for the rapid, low-cost screening of therapeutic mAb candidates. Full article

Background/Objectives: COVID-19, caused by SARS-CoV-2, has emerged as a global pandemic since its outbreak in 2019. As an increasing number of variants have emerged, especially concerning variants such as Omicron BA.1, BA.2, XBB.1, EG.5, which can escape the immune system and cause repeated infections, they have exerted significant pressure on monoclonal antibodies and the treatment approaches for COVID-19. Broad spectrum antiviral medication was urgently needed. In this study, we developed several bispecific antibodies based on the IgG-scFv format and one trispecific antibody containing Fab fragments with different anti-virus mechanisms studied previously. The Fab fragments are from h11B11, S2P6, and S309 respectively. Method: all recombinant antibodies were expressed by HEK 293. The pseudoviruses’ neutralization assay and the virus challenge to BALB/c mice were deployed to assess the efficiency of recombinant antibodies in vitro and in vivo. Results: the bispecific antibodies exhibited a favorable pseudoviruses neutralization activity, with IC₅₀ values ranging from 8 to 591 ng/mL. The trispecific antibody performed even better, with IC₅₀ values ranging from 5 to 27 ng/mL. Furthermore, the virus challenge to mice confirmed that the bispecific antibodies, including the trispecific antibody, had decent therapeutic efficacy. Conclusions: our study provided several supplements to the therapeutic measures of COVID-19 based on multispecific antibodies, supporting the great potential of the multispecific antibodies strategy in dealing with emerging pathogens. Full article

Herpes simplex viruses (HSV-1 and HSV-2), which can be transmitted both orally and sexually, cause lifelong morbidity and in some cases, meningitis and encephalitis. While both the passive transfer of neutralizing antibodies and placental transfer of anti-HSV monoclonal antibodies (Mabs) have shown therapeutic promise in animal models, clinical trials have yet to identify approved immunotherapeutics for herpes infection. Here, we present strategies for the generation of recombinant bispecific antibodies (BsAbs) that target different domains of glycoprotein D (gD), crucial for HSV entry, that have the potential to outperform the effect of individual Mabs to curb herpes infection. Specifically, we selected three pairs of Mabs from our extensive panel for BsAb design and production based on their binding site and ability to block virus entry. Actual binding of BsAbs to gD and epitope availability on gD after BsAb binding were characterized using surface plasmon resonance (SPR) and inhibition by IgG Fab fragments generated from selected Mabs. While one BsAb exhibited an additive effect similar to that observed using a combination of the Mabs utilized for its generation, two showed antagonistic effects, suggesting that the simultaneous engagement of two epitopes or selective binding to one affected their activity against HSV. One BsAb (DL11/1D3) targeting the binding site for both nectin-1 and HVEM receptors demonstrated synergistic inhibitory activity against HSV, outperforming the effect of the individual antibodies. Recombinant DL11/1D3 antibody variants, in which the size of one or both paratopes was decreased to single chains (scFv-Fc), highlighted differences in potency depending on antibody size and format. We propose that BsAbs to individual glycoproteins offer a potential avenue for herpes therapeutics, but their design, mechanism of action, antibody format, and epitope engagement require careful consideration of structure for optimal efficacy. Full article

Snakebite is a critical global public health issue, causing substantial mortality and morbidity, particularly in tropical and subtropical regions. The development of innovative antivenoms targeting snake venom toxins is therefore of paramount importance. In this study, we adopted an epitope-directed approach to design three degenerate 15-mer peptides based on amino acid sequence alignments of snake venom phospholipase A₂s (PLA₂s) and snake venom serine proteases (SVSPs) from snake (Crotalus atrox). By leveraging their immunogenic and inhibitory profiles, these peptides were specifically designed to target the Asp49 and Lys49 variants of PLA₂ and SVSP toxins. Groups of five mice were immunized with each peptide, and IgG mRNA was subsequently extracted from peripheral blood mononuclear cells (PBMCs) and spleen lymphocytes of the top three responders. The extracted mRNA was reverse-transcribed into complementary DNA (cDNA), and the variable regions of the IgG heavy and kappa chains were amplified using polymerase chain reaction (PCR). These amplified regions were then linked with a 66-nucleotide spacer to construct single-chain variable fragments (scFvs). Sequence analysis of 48 randomly selected plasmids from each PLA₂ and SVSP scFv library revealed that over 80% contained scFv sequences with notable diversity observed in the complementarity-determining regions (CDRs), particularly CDR3. Enzyme-linked immunosorbent assay (ELISA) results demonstrated that the SP peptide elicited a broader immune response in mice compared to the Asp49 peptide, implying the strong immunogenicity of the SP peptide. These scFvs represent a promising foundation for the development of recombinant human monoclonal antibodies targeting snake PLA₂ and SVSP toxins, providing a potential therapeutic strategy for the treatment of snakebites. Full article

Osteocalcin is a useful biomarker for bone formation and bone-related diseases. KTM219 is an anti-osteocalcin C-terminal peptide antibody. The single-chain variable region (scFv) and antigen-binding fragment (Fab) of KTM219 are applicable to the Quenchbody (Q-body) immunoassay. Q-body is a new type of fluorescent immunosensor, which is scFv or Fab labeled with a fluorescent dye. When Q-body binds to its antigen, the fluorescence intensity increases. The highly sensitive detection of antigens by changes in fluorescence intensity is performed in a single step by mixing the sample and reagent. In this study, to reveal the recognition mechanism of the KTM219 antibody and to discuss the structural basis for Q-body, we solved the crystal structures of Fab of the anti-osteocalcin antibody KTM219 and its complex with the antigen osteocalcin C-terminal peptide (BGP-C7). Also, we solved the structure of a KTM219 Fab crystal grown in the presence of a fluorescent dye, carboxytetramethylrhodamine (TAMRA); however, tightly bound TAMRA was not found in the electron density map. We predicted the binding sites of TAMRA in the antigen-binding pocket by docking simulations. These results support the proposed Q-body mechanism. The crystal structures of KTM219 Fab would be useful for further development and improvement of Q-body fluorescent immunosensors. Full article