Search Results (22)

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

Glycosaminoglycans (GAGs) are key ligands for proteins involved in physiological and pathological processes. Specific GAG-binding patterns are rarely identified, with the heparin pentasaccharide as an Antithrombin-III ligand being the best characterized. Generating glycan-specific antibodies is difficult due to their size, pattern dispersion, and flexibility. Single-domain variable new antigen receptors (VNAR nanobodies) from nurse sharks are highly soluble, stable, and versatile. Their unique properties suggest advantages over conventional antibodies, particularly for challenging biotherapeutic targets. Here we have used VNAR semi-synthetic phage libraries to select high-affinity fondaparinux-binding VNARs that did not show cross-reactivity with other GAG species. Competition ELISA and surface plasmon resonance identified a single fondaparinux-selective VNAR clone. This VNAR exhibited an extraordinarily stable protein fold: the beta-strands are stabilized by a robust hydrophobic network, as revealed by heteronuclear NMR. Docking fondaparinux to the VNAR structure revealed a large contact surface area between the CDR3 loop of the antibody and the glycan. Fusing the VNAR with a human Fc domain resulted in a stable product with a high affinity for fondaparinux (Kd = 9.3 × 10⁻⁸ M) that could efficiently discriminate between fondaparinux and other glycosaminoglycans. This novel glycan-targeting screening technology represents a promising therapeutic strategy for addressing GAG-related diseases. Full article

Heavy chain-only antibodies in sharks are called immunoglobulin new antigen receptors (IgNAR), consisting of one variable region (VNAR) and five constant regions (C1-C5). The variable region of IgNAR can be expressed as a monomer composed of a single domain, which has antigen specificity and is thus gaining attention as a next-generation antibody drug modality. In this study, we analyzed IgNAR of the cloudy catshark and Japanese bullhead shark, small demersal sharks available in the coastal waters of Japan. By analyzing the IgNAR gene sequence and comparing it with the constant regions of five other known shark species, high homology was observed in the C4 region. Consequently, we expressed the recombinant protein of the C4 domain from the cloudy catshark in E. coli, immunized rats, and produced antibodies. The obtained antiserum and mAbs recognized the C4 recombinant protein of the cloudy catshark, but reacted minimally with the plasma of non-immunized cloudy catsharks and instead reacted with the plasma of Japanese bullhead sharks. The results of this study imply that the protein expression levels of IgNAR in cloudy catsharks may be relatively lower compared to those in Japanese bullhead sharks, however, this interpretation remains to be determined through further studies. Full article

Single-domain antibodies, including variable domains of the heavy chains of heavy chain-only antibodies (VHHs) from camelids and variable domains of immunoglobulin new antigen receptors (VNARs) from cartilaginous fish, show the therapeutic potential of targeting antigens in a cytosol reducing environment. A large proportion of single-domain antibodies contain non-canonical cysteines and corresponding non-canonical disulfide bonds situated on the protein surface, rendering them vulnerable to environmental factors. Research on non-canonical disulfide bonds has been limited, with a focus solely on VHHs and utilizing only cysteine mutations rather than the reducing agent treatment. In this study, we examined an anti-lysozyme VNAR and an anti-BC2-tag VHH, including their non-canonical disulfide bond reduced counterparts and non-canonical cysteine mutants. Both the affinity and stability of the VNARs and VHHs decreased in the non-canonical cysteine mutants, whereas the reduced-state samples exhibited decreased thermal stability, with their affinity remaining almost unchanged regardless of the presence of reducing agents. Molecular dynamics simulations suggested that the decrease in affinity of the mutants resulted from increased flexibility of the CDRs, the disappearance of non-canonical cysteine–antigen interactions, and the perturbation of other antigen-interacting residues caused by mutations. These findings highlight the significance of non-canonical cysteines for the affinity of single-domain antibodies and demonstrate that the mutation of non-canonical cysteines is not equivalent to the disruption of non-canonical disulfide bonds with a reducing agent when assessing the function of non-canonical disulfide bonds. Full article

Diverse candidate antibodies are needed to successfully identify therapeutic and diagnostic applications. The variable domain of IgNAR (VNAR), a shark single-domain antibody, has attracted attention owing to its favorable physicochemical properties. The phage display method used to screen for optimal VNARs loses sequence diversity because of the bias caused by the differential ease of protein expression in Escherichia coli. Here, we investigated a VNAR selection method that combined panning with various selection pressures and next-generation sequencing (NGS) analyses to obtain additional candidates. Drawing inspiration from the physiological conditions of sharks and the physicochemical properties of VNARs, we examined the effects of NaCl and urea concentrations, low temperature, and preheating at the binding step of panning. VNAR phage libraries generated from Japanese topeshark (Hemitriakis japanica) were enriched under these conditions. We then performed NGS analysis and attempted to select clones that were specifically enriched under each panning condition. The identified VNARs exhibited higher reactivity than those obtained by panning without selection pressure. Additionally, they possess physicochemical properties that reflect their respective selection pressures. These results can greatly enhance our understanding of VNAR properties and offer guidance for the screening of high-quality VNAR clones that are present at low frequencies. Full article

The shark-derived single-domain antibody VNAR (variable domain of new antigen receptor) has many advantageous features that make the VNAR suitable for improving current monoclonal antibody therapy deficiencies or disease diagnosis methods. In order to discover more VNARs, it is necessary to improve the efficiency of the isolation process. This research aims to enhance the VNAR discovery platform by dual displaying the semi-synthetic VNAR library and green fluorescent protein tag on the yeast surface. The GFP tag can be used to determine the degree of VNAR expression. The diversity of the semi-synthetic VNAR library constructed in this study is verified to be 1.97 × 10⁹ by next-generation sequencing (NGS). We conveniently screened VNARs against the feline neonatal Fc receptor or feline infectious peritonitis virus nucleocapsid protein by sequential MACS and FACS. To find more diverse VNARs, we analyzed the NGS data of VNAR CDR3 genes before and after biopanning. By comparing the frequency change of each sequence, we found that the amplification factor of sequences was increased by biopanning. Four VNAR candidates selected by the high-frequency and high-amplification factor criteria showed an antigen-binding ability. The results demonstrate that biopanning from a yeast surface displaying a semi-synthetic VNAR library followed by the NGS assay can generate antigen binders rapidly without the need for shark rearing and long-term immunization. Full article

Antibodies represent a relatively mature detection means and serve as therapeutic drug carriers in the clinical diagnosis and treatment of cancer—among which monoclonal antibodies (mAbs) currently occupy a dominant position. However, the emergence and development of small-molecule monodomain antibodies are inevitable due to the many limitations of mAbs, such as their large size, complex structure, and sensitivity to extreme temperature, and tumor microenvironments. Thus, since first discovered in Chondroid fish in 1995, IgNAR has become an alternative therapeutic strategy through which to replace monoclonal antibodies, thus entailing that this novel type of immunoglobulin has received wide attention with respect to clinical diagnoses and tumor therapies. The variable new antigen receptor (VNAR) of IgNAR provides an advantage for the development of new antitumor drugs due to its small size, high stability, high affinity, as well as other structural and functional characteristics. In that respect, a better understanding of the unique characteristics and therapeutic potential of IgNAR/VNAR in clinical and anti-tumor treatment is needed. This article reviews the advantages of its unique biochemical conditions and molecular structure for clinical diagnoses and novel anti-tumor drugs. At the same time, the main advantages of the existing conjugated drugs, which are based on single-domain antibodies, are introduced here, thereby providing new ideas and methods for the development of clinical diagnoses and anti-tumor therapies in the future. Full article

Immunoglobulin new antigen receptor (IgNAR) is a naturally occurring antibody that consists of only two heavy chains with two independent variable domains. The variable binding domain of IgNAR, called variable new antigen receptor (VNAR), is attractive due to its solubility, thermal stability, and small size. Hepatitis B surface antigen (HBsAg) is a viral capsid protein found on the surface of the Hepatitis B virus (HBV). It appears in the blood of an individual infected with HBV and is widely used as a diagnostic marker for HBV infection. In this study, the whitespotted bamboo sharks (Chiloscyllium plagiosum) were immunized with the recombinant HBsAg protein. Peripheral blood leukocytes (PBLs) of immunized bamboo sharks were further isolated and used to construct a VNAR-targeted HBsAg phage display library. The 20 specific VNARs against HBsAg were then isolated by bio-panning and phage ELISA. The 50% of maximal effect (EC₅₀) of three nanobodies, including HB14, HB17, and HB18, were 4.864 nM, 4.260 nM, and 8.979 nM, respectively. The Sandwich ELISA assay further showed that these three nanobodies interacted with different epitopes of HBsAg protein. When taken together, our results provide a new possibility for the application of VNAR in HBV diagnosis and also demonstrate the feasibility of using VNAR for medical testing. Full article

Research into various proteins capable of blocking metabolic pathways has improved the detection and treatment of multiple pathologies associated with the malfunction and overexpression of different metabolites. However, antigen-binding proteins have limitations. To overcome the disadvantages of the available antigen-binding proteins, the present investigation aims to provide chimeric antigen-binding peptides by binding a complementarity-determining region 3 (CDR3) of variable domains of new antigen receptors (VNARs) with a conotoxin. Six non-natural antibodies (NoNaBodies) were obtained from the complexes of conotoxin cal14.1a with six CDR3s from the VNARs of Heterodontus francisci and two NoNaBodies from the VNARs of other shark species. The peptides cal_P98Y vs. vascular endothelial growth factor 165 (VEGF₁₆₅), cal_T10 vs. transforming growth factor beta (TGF-β), and cal_CV043 vs. carcinoembryonic antigen (CEA) showed in-silico and in vitro recognition capacity. Likewise, cal_P98Y and cal_CV043 demonstrated the capacity to neutralize the antigens for which they were designed. Full article

Since the delivery of biologic drugs to the brain is greatly hampered by the existence of the blood–brain barrier (BBB), brain shuttles are being developed to enhance therapeutic efficacy. As we have previously shown, efficient and selective brain delivery was achieved with TXB2, a cross-species reactive, anti-TfR1 VNAR antibody. To further explore the limits of brain penetration, we conducted restricted randomization of the CDR3 loop, followed by phage display to identify improved TXB2 variants. The variants were screened for brain penetration in mice using a 25 nmol/kg (1.875 mg/kg) dose and a single 18 h timepoint. A higher kinetic association rate to TfR1 correlated with improved brain penetration in vivo. The most potent variant, TXB4, showed a 3.6-fold improvement over TXB2, which had on average 14-fold higher brain levels when compared to an isotype control. Like TXB2, TXB4 retained brain specificity with parenchymal penetration and no accumulation in other organs. When fused with a neurotensin (NT) payload, it led to a rapid drop in body temperature upon transport across the BBB. We also showed that fusion of TXB4 to four therapeutic antibodies (anti-CD20, anti-EGFRvIII, anti-PD-L1 and anti-BACE1) improved their brain exposure between 14- to 30-fold. In summary, we enhanced the potency of parental TXB2 brain shuttle and gained a critical mechanistic understanding of brain delivery mediated by the VNAR anti-TfR1 antibody. Full article

Severe Acute Respiratory Syndrome Coronavirus 2 is the causal pathogen of coronavirus disease 2019 (COVID-19). The emergence of new variants with different mutational patterns has limited the therapeutic options available and complicated the development of effective neutralizing antibodies targeting the spike (S) protein. Variable New Antigen Receptors (VNARs) constitute a neutralizing antibody technology that has been introduced into the list of possible therapeutic options against SARS-CoV-2. The unique qualities of VNARs, such as high affinities for target molecules, capacity for paratope reformatting, and relatively high stability, make them attractive molecules to counteract the emerging SARS-CoV-2 variants. In this study, we characterized a VNAR antibody (SP240) that was isolated from a synthetic phage library of VNAR domains. In the phage display, a plasma with high antibody titers against SARS-CoV-2 was used to selectively displace the VNAR antibodies bound to the antigen SARS-CoV-2 receptor binding domain (RBD). In silico data suggested that the SP240 binding epitopes are located within the ACE2 binding interface. The neutralizing ability of SP240 was tested against live Delta and Omicron SARS-CoV-2 variants and was found to clear the infection of both variants in the lung cell line A549-ACE2-TMPRSS2. This study highlights the potential of VNARs to act as neutralizing antibodies against emerging SARS-CoV-2 variants. Full article

The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein is the major target for antibody therapeutics. Shark-derived variable domains of new antigen receptors (VNARs) are the smallest antibody fragments with flexible paratopes that can recognize protein motifs inaccessible to classical antibodies. This study reported four VNARs binders (JM-2, JM-5, JM-17, and JM-18) isolated from Chiloscyllium plagiosum immunized with SARS-CoV-2 RBD. Biolayer interferometry showed that the VNARs bound to the RBD with an affinity K_D ranging from 38.5 to 2720 nM, and their Fc fusions had over ten times improved affinity. Gel filtration chromatography revealed that JM-2-Fc, JM-5-Fc, and JM-18-Fc could form stable complexes with RBD in solution. In addition, five bi-paratopic VNARs, named JM-2-5, JM-2-17, JM-2-18, JM-5-18, and JM-17-18, were constructed by fusing two VNARs targeting distinct RBD epitopes based on epitope grouping results. All these bi-paratopic VNARs except for JM-5-18 showed higher RBD binding affinities than its component VNARs, and their Fc fusions exhibited further enhanced binding affinities, with JM-2-5-Fc, JM-2-17-Fc, JM-2-18-Fc, and JM-5-18-Fc having K_D values lower than 1 pM. Among these Fc fusions of bi-paratopic VNARs, JM-2-5-Fc, JM-2-17-Fc, and JM-2-18-Fc could block the angiotensin-converting enzyme 2 (ACE2) binding to the RBD of SARS-CoV-2 wildtype, Delta, Omicron, and SARS-CoV, with inhibition rates of 48.9~84.3%. Therefore, these high-affinity VNAR binders showed promise as detectors and therapeutics of COVID-19. Full article

Chimeric antigen receptor (CAR) technology has been highlighted in recent years as a new therapeutic approach for cancer treatment. Although the impressive efficacy of CAR-based T cell adoptive immunotherapy has been observed in hematologic cancers, limited effect has been reported on solid tumors. Approximately 20% of gastric cancer (GC) patients exhibit a high expression of c-Met. We have generated an anti c-Met CAR construct that is composed of a single-chain variable fragment (scFv) of c-Met antibody and signaling domains consisting of CD28 and CD3ζ. To test the CAR construct, we used two cell lines: the Jurkat and KHYG-1 cell lines. These are convenient cell lines, compared to primary T cells, to culture and to test CAR constructs. We transduced CAR constructs into Jurkat cells by electroporation. c-Met CAR Jurkat cells secreted interleukin-2 (IL-2) only when incubated with c-Met positive GC cells. To confirm the lytic function of CAR, the CAR construct was transduced into KHYG-1, a NK/T cell line, using lentiviral particles. c-Met CAR KHYG-1 showed cytotoxic effect on c-Met positive GC cells, while c-Met negative GC cell lines were not eradicated by c-Met CAR KHYG-1. Based on these data, we created c-Met CAR T cells from primary T cells, which showed high IL-2 and IFN-γ secretion when incubated with the c-Met positive cancer cell line. In an in vivo xenograft assay with NSG bearing MKN-45, a c-Met positive GC cell line, c-Met CAR T cells effectively inhibited the tumor growth of MKN-45. Our results show that the c-Met CAR T cell therapy can be effective on GC. Full article

Shark is a cartilaginous fish that produces new antigen receptor (IgNAR) antibodies. This antibody is identified with a similar human heavy chain but dissimilar sequences. The variable domain (VNAR) of IgNAR is stable and small in size, these features are desirable for drug discovery. Previous study results revealed the effectiveness of VNAR as a single molecule or a combination molecule to treat diseases both in vivo and in vitro with promising clinical applications. We showed the first evidence of IgNAR alternative splicing from spotted bamboo shark (Chiloscyllium plagiosum), broadening our understanding of the IgNARs characteristics. In this review, we summarize the discoveries on IgNAR with a focus on its advantages for therapeutic development based on its peculiar biochemistry and molecular structure. Proper applications of IgNAR will provide a novel avenue to understand its special presence in cartilaginous fishes as well as designing a number of drugs for undefeated diseases. Full article

Natural immunoglobulin M (IgM) antibodies are pentameric or hexameric macro-immunoglobulins and have been highly conserved during evolution. IgMs are initially expressed during B cell ontogeny and are the first antibodies secreted following exposure to foreign antigens. The IgM multimer has either 10 (pentamer) or 12 (hexamer) antigen binding domains consisting of paired µ heavy chains with four constant domains, each with a single variable domain, paired with a corresponding light chain. Although the antigen binding affinities of natural IgM antibodies are typically lower than IgG, their polyvalency allows for high avidity binding and efficient engagement of complement to induce complement-dependent cell lysis. The high avidity of IgM antibodies renders them particularly efficient at binding antigens present at low levels, and non-protein antigens, for example, carbohydrates or lipids present on microbial surfaces. Pentameric IgM antibodies also contain a joining (J) chain that stabilizes the pentameric structure and enables binding to several receptors. One such receptor, the polymeric immunoglobulin receptor (pIgR), is responsible for transcytosis from the vasculature to the mucosal surfaces of the lung and gastrointestinal tract. Several naturally occurring IgM antibodies have been explored as therapeutics in clinical trials, and a new class of molecules, engineered IgM antibodies with enhanced binding and/or additional functional properties are being evaluated in humans. Here, we review the considerable progress that has been made regarding the understanding of biology, structure, function, manufacturing, and therapeutic potential of IgM antibodies since their discovery more than 80 years ago. Full article