Search Results (380)

A single domain antibody (SDAb) targeting canine PD-1 was developed as a potential immunotherapeutic for canine cancer. An alpaca was immunized with canine PD-1 protein, and a phage-display library was constructed using mRNA isolated from peripheral lymphocytes. Screening of the library yielded multiple SDAb candidates capable of nanomolar binding to canine PD-1. Among these, clone STX-1b5 demonstrated high expression in a yeast-based recombinant system and was selected for further characterization. Binding and competition assays using ELISA confirmed its ability to bind canine PD-1 and block PDL-1 interaction. In silico structural modeling supported the interaction of STX-1b5 with key PD-1 residues implicated in ligand binding. These findings support the feasibility of using SDAbs and cost-effective yeast expression systems to generate immunotherapeutics for veterinary use, with STX-1b5 representing a promising lead candidate for future clinical development. Full article

Virus-like nanoparticles (VNPs) based on Moloney murine leukemia virus represent a well-established platform for the expression of heterologous molecules such as cytokines, cytokine receptors, peptide MHC (pMHC) and major allergens, but their application for inducing protective anti-viral immunity has remained understudied as of yet. Here, we variably fused the wildtype SARS-CoV-2 spike, its receptor-binding domain (RBD) and nucleocapsid (NC) to the minimal CD16b-GPI anchor acceptor sequence for expression on the surface of VNP. Moreover, a CD16b-GPI-anchored single-chain version of IL-12 was tested for its adjuvanticity. VNPs expressing RBD::CD16b-GPI alone or in combination with IL-12::CD16b-GPI were used to immunize BALB/c mice intramuscularly and subsequently to investigate virus-specific humoral and cellular immune responses. CD16b-GPI-anchored viral molecules and IL-12-GPI were well-expressed on HEK-293T-producer cells and purified VNPs. After the immunization of mice with VNPs, RBD-specific antibodies were only induced with RBD-expressing VNPs, but not with empty control VNPs or VNPs solely expressing IL-12. Mice immunized with RBD VNPs produced RBD-specific IgM, IgG_2a and IgG₁ after the first immunization, whereas RBD-specific IgA only appeared after a booster immunization. Protein/peptide microarray and ELISA analyses confirmed exclusive IgG reactivity with folded but not unfolded RBD and showed no specific IgG reactivity with linear RBD peptides. Notably, booster injections gradually increased long-term IgG antibody avidity as measured by ELISA. Interestingly, the final immunization with RBD–Omicron VNPs mainly enhanced preexisting RBD Wuhan Hu-1-specific antibodies. Furthermore, the induced antibodies significantly neutralized SARS-CoV-2 and specifically enhanced cellular cytotoxicity (ADCC) against RBD protein-expressing target cells. In summary, VNPs expressing viral proteins, even in the absence of adjuvants, efficiently induce functional SARS-CoV-2-specific antibodies of all three major classes, making this technology very interesting for future vaccine development and boosting strategies with low reactogenicity. 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

Background: Tetanus toxin, produced by Clostridium tetani, is the second deadliest known toxin. Antibodies capable of neutralizing tetanus toxin (TeNT) are vital for preventing and treating tetanus disease. Methods: Herein, we screened thirty-six single variable domains on a heavy chain (VHHs) binding to the light chain (L) and the translocation domain (HN) (L-HN) fragment of TeNT from a phage-display library. Then, the L-HN-specific clones were identified, humanized, and fused with a human fragment crystallizable region (hFc) to form humanized VHH-hFc fusion proteins. Results: The humanized VHH-hFc fusion proteins TL-16-h1-hFc, TL-25-h1-hFc, and TL-34-h1-hFc possessed potent efficacy with high binding affinity, specificity, and neutralizing activity. Only 0.3125 μg was required for TL-16-h1-hFc or TL-25-h1-hFc, and 0.625 μg was required for TL-34-h1-hFc to provide full protection against 10 × Lethal Dose 50 (LD₅₀) TeNT. In the prophylactic setting, 125 μg/kg of TL-16-h1-hFc or TL-25-h1-hFc provided full protection even when they were injected 12 days before exposure to 10 × LD₅₀ TeNT, while TL-34-h1-hFc was less effective. In the therapeutic setting, 25 μg/kg of TL-16-h1-hFc or TL-25-h1-hFc could provide complete protection when administered 24 h after exposure to 5 × LD₅₀ TeNT, while TL-34-h1-hFc required 50 μg/kg. Conclusion: Our results suggest that TL-16-h1-hFc, TL-25-h1-hFc, and TL-34-h1-hFc provide a bright future for the development of anti-TeNT preventive or therapeutic drugs. Full article

Background/Objectives: Developing next-generation mRNA-based seasonal influenza vaccines remains challenging, primarily because of the relatively low immunogenicity of influenza B hemagglutinin (HA) antigens. We describe a systematic vaccine development strategy that combined vector and antigen design optimization. Methods: Novel untranslated region (UTR) sequences and a hybrid poly(A) tail were used to increase plasmid stability and mRNA expression. Fusion proteins containing HA antigens linked by T4 foldon domains were engineered to enhance the immune responses against influenza B HA antigens and to permit the expression of multiple HA ectodomains from a single mRNA species. The vaccine performance was verified in a traditional encapsulated lipid nanoparticle (LNP) formulation that requires long-term storage at temperatures below −15 °C as well as in a proprietary thermo-stable LNP formulation developed for the long-term storage of the mRNA vaccine at 2–8 °C. Results: In preclinical studies, our next-generation seasonal influenza vaccine tested alone or as a combination influenza/COVID-19 mRNA vaccine elicited hemagglutination inhibition (HAI) titers significantly higher than Fluzone HD, a commercial inactivated influenza vaccine, across all 2024/2025 seasonal influenza strains, including the B/Victoria lineage strain. At the same time, the combination mRNA vaccine demonstrated superior neutralizing antibody titers to 2023/2024 Spikevax, a commercial COVID-19 comparator mRNA vaccine. Conclusions: Our data demonstrate that the multimerization of antigens expressed as complex fusion proteins is a powerful antigen design approach that may be broadly applied toward mRNA vaccine development. Full article

Recombinant monoclonal antibody (mAb) botulinum neurotoxin (BoNT) antitoxins, consisting of three mAbs that bind non-overlapping epitopes, are highly potent. However, the three-mAb mixtures pose unique development and manufacturing challenges. Combining even more mAbs to create multivalent antitoxin drugs multiplies those challenges. We previously reported that a single tri-epitopic IgG1-based mAb (TeAb) containing the variable domains of the three parental BoNT/A mAbs and an Fc was as potent as the combination of three IgGs in the mouse neutralization assay (MNA). Here, we extended the tri-epitopic strategy to three other BoNT serotypes. Each TeAb (TeAb-B for BoNT/B, TeAb-E for BoNT/E, and TeAb-F for BoNT/F) binding was measured using fluorescence-activated cell sorting and flow fluorimetry, and the potency was tested in the MNA. The three TeAbs displayed binding affinities that were the same within error of the parental IgGs for each epitope, and all had higher avidity to each serotype of BoNT than that of the parental mAbs. The potency of the BoNT/B, BoNT/E, and BoNT/F TeAbs was similar to the combinations of the three parental IgGs binding BoNT/B, BoNT/E, and BoNT/F in the MNA. We now have four examples of a single TeAb recapitulating the affinity and in vivo potency of a three-mAb antitoxin. The tri-epitopic strategy could be applied to streamline the production and bioanalytics of antibody drugs where three-mAb binding is required for activity. Full article

Murine double minute 2 (MDM2) is involved in various cancers and is an attractive target. The RING domain of MDM2 has been discussed as an alternative target to stabilize p53. Designing drugs to target the RING domain of MDM2 is an alternative approach to preventing MDM2-mediated deactivation of p53. In this study, we obtained a human VH single-domain antibody and revealed its regulatory effects and mechanisms. The RING domain of MDM2 was synthesized using a chemical synthesis method, and antibodies against the MDM2 RING domain were screened from a human VH single-domain antibody library and expressed intracellularly. A nuclear localization sequence was designed to ensure intrabody efficiency. The binding activity of the individually cloned antibodies was detected using ELISA. MTT and flow cytometry assays were used to detect the reactions related to intrabody in vitro. The combination and its influence on MDM2 were detected using immunoprecipitation assays, confocal microscopy, and Western blotting. The effects on apoptosis-related mitochondrial pathways downstream of p53 were examined using Western blotting. The influence on cell cycle distribution and cyclin-related proteins was detected using flow cytometry and Western blotting. A549 cell xenografts were constructed to assess the effect of intrabodies on growth in vivo. The molecular mechanisms of MDM2 and p53 were studied using Western blotting. Eight individual cloned antibodies were positive compared to the signals on the BSA-coated plates, especially intrabodies VH-HT3. In A549 and MCF-7 cell lines, VH-HT3 exhibited significant inhibitory effects on cell proliferation and apoptosis. VH-HT3 co-localized with MDM2 in the nucleus and cytoplasm. The specific combination of VH-HT3 triggered no significant effect on MDM2 activity for p53 degradation but upregulated the levels of factors downstream of p53, especially those in the mitochondrial apoptosis pathway. Moreover, VH-HT3 induced cell cycle arrest, and the expression of cyclin-related proteins was consistent with this observation. VH-HT3 also retarded the growth of A549 xenografts in vivo. Further tests suggested that VH-HT3 inhibited MDM2 function by increasing HIPK2 levels and activating p53 at the Ser46 site. VH-HT3, prepared from a human VH single-domain antibody library, inhibited p53 activity and produced a tumor-suppressive effect. The intrabody VH-HT3 is a candidate for the development of novel MDM2 inhibitors. Full article

Background/Objectives: Identification and characterization of broadly neutralizing monoclonal antibodies from individuals exposed to SARS-CoV-2, either by infection or vaccination, can inform the development of next-generation vaccines and antibody therapeutics with pan-SARS-CoV-2 protection. Methods: Through single B cell sorting and RT-PCR, monoclonal antibodies (mAbs) were isolated from a donor who experienced a BA.5 or BF.7 breakthrough infection after three doses of inactivated vaccines. Their binding and neutralizing capacities were measured with ELISA and a pseudovirus-based neutralization assay, respectively. Their epitopes were mapped by competition ELISA and site-directed mutation. Results: Among a total of 67 spike-specific mAbs cloned from the donor, four mAbs (KXD643, KXD652, KXD681, and KXD686) can neutralize all tested SARS-CoV-2 variants from wild-type to KP.3. Moreover, KXD643, KXD652, and KXD681 belong to a clonotype encoded by IGHV5-51 and IGKV1-13 and recognize the cryptic and conserved RBD-8 epitope on the receptor-binding domain (RBD). In contrast, KXD686 is encoded by IGHV1-69 and IGKV3-20 and targets a conserved epitope (NTD Site iv) outside the antigenic supersite (NTD Site i) of the N-terminal domain (NTD). Notably, antibody cocktails containing these two groups of mAbs can neutralize SARS-CoV-2 more potently due to synergistic effects. In addition, bispecific antibodies derived from KXD643 and KXD686 demonstrate further improved neutralizing potency compared to antibody cocktails. Conclusions: These four mAbs can be developed as candidates of pan-SARS-CoV-2 antibody therapeutics through further antibody engineering. On the other hand, vaccines designed to simultaneously elicit neutralizing antibodies towards RBD-8 and NTD Site iv have the potential to provide pan-SARS-CoV-2 protection. Full article

Nanobodies, derived from naturally occurring heavy-chain antibodies in camelids (VHHs) and sharks (V_NARs), are unique single-domain antibodies that have garnered significant attention in therapeutic, diagnostic, and biotechnological applications due to their small size, stability, and high specificity. This review first traces the historical discovery of nanobodies, highlighting key milestones in their isolation, characterization, and therapeutic development. We then explore their structure–function relationship, emphasizing features like their single-domain architecture and long CDR3 loop that contribute to their binding versatility. Additionally, we examine the growing interest in multiepitope nanobodies, in which binding to different epitopes on the same antigen not only enhances neutralization and specificity but also allows these nanobodies to be used as controllable modules for precise antigen manipulation. This review also discusses the integration of AI in nanobody design and optimization, showcasing how machine learning and deep learning approaches are revolutionizing rational design, humanization, and affinity maturation processes. With continued advancements in structural biology and computational design, nanobodies are poised to play an increasingly vital role in addressing both existing and emerging biomedical challenges. Full article

Background/Objectives: Venezuelan equine encephalitis virus (VEEV) represents a significant biothreat with no FDA-approved vaccine currently available, highlighting the need for alternative therapeutic strategies. Single-domain antibodies (sdAbs) present a potential alternative to conventional antibodies, due to their small size and ability to recognize cryptic epitopes. Methods: This research describes the development and preliminary evaluation of VEEV-binding sdAbs generated using a generative artificial intelligence (AI) platform. Using a dataset of known alphavirus-binding sdAbs, the AI model produced sequences with predicted affinity for the E2 glycoprotein of VEEV. These candidate sdAbs were expressed in a bacterial periplasmic system and purified for initial assessment. Results: Enzyme-linked immunosorbent assays (ELISAs) indicated binding activity of the sdAbs to VEEV antigens. In vitro neutralization tests suggested inhibition of VEEV infection in cultured cells for some of the candidates. Conclusions: This study demonstrates how generative AI can expedite antiviral therapeutic development and establishes a framework for quick responses to emerging viral threats when extensive example databases are unavailable. Additional refinement and validation of AI-generated sdAbs could establish effective VEEV therapeutics. Full article

Background/Objectives: Intact (146S) foot-and-mouth disease virus (FMDV) particles easily dissociate into 12S particles with a concomitant decreased immunogenicity. Vaccine quality control with 146S-specific single-domain antibodies (VHHs) is hampered by the high strain specificity of most 146S-specific VHHs. This study aimed to isolate 146S-specific VHHs that recognize all serotype O strains. Methods: Biopanning was performed with the FMDV strain O/SKR/7/2010 146S, using a secondary library of mutagenized M170F VHH that did not recognize O/SKR/7/2010 or using phage-display libraries from llamas immunized with other serotype O strains. Novel VHHs were yeast-produced and their strain-, particle-, and antigenic-site specificities were determined by ELISA. Results: M170F mutagenesis did not improve the cross-reaction with O/SKR/7/2010. However, selection from immune libraries resulted in four VHHs that exhibited high 146S specificity for all five serotype O strains analyzed. These VHHs presumably recognize all serotype O strains since the five strains analyzed represent different phylogenetic clades. They bind the same antigenic site as M170F, which was previously shown to be a conserved site in serotypes A and O, and which has an altered 3D structure when 146S dissociates into 12S particles. M916F had the lowest limit of detection, which varied from 0.7 to 5.9 ng/mL 146S particles for three serotype O strains. Conclusions: We identified four VHHs (M907F, M910F, M912F, and M916F) that specifically bind 146S particles of probably all serotype O strains. They enable further improved FMDV vaccine quality control. Full article

Background/Objectives: The aim of our study was to investigate B cell and T cell responses in people with multiple sclerosis (PwMS) treated with ocrelizumab, a humanized anti-CD20 antibody, who were vaccinated with second and/or booster doses of various vaccine brands against COVID-19. Additionally, we detected the outcomes related to COVID-19 in PwMS after vaccination, based on follow-up for at least 12 months. Methods: We enrolled 91 PwMS on ocrelizumab and 42 healthy controls (HCs) in a prospective, single-center study, conducted at the Clinic of Neurology, UCCS, between January 2022 and October 2024. The serological responses were measured using the spike receptor-binding domain (RBD) Architect SARS-CoV-2 IgG Quant kit (Abbot), and cellular responses were measured by quantifying IFN-γ secretion in blood incubated with SARS-CoV-2 antigens. Results: A total of 58.2% (53/91) of PwMS on ocrelizumab and 100% of the HCs (42/42) were seropositive after a second or booster vaccination (p < 0.001), irrespective of the vaccine brand received. Anti-spike antibody levels were significantly lower in PwMS on ocrelizumab compared to the HCs (p < 0.001), again irrespective of the vaccine type. Interferon-γ responses were detected in 95.6% of the PwMS receiving ocrelizumab therapy and 97.6% of HCs after vaccination (p = 0.570). In our cohort, PCR-confirmed SARS-CoV-2 infections after vaccination occurred in a similar proportion of the PwMS (45/91, 49.5%) and HCs (15/32, 46.9%) (p = 0.139). Most of the PwMS (36/45, 79.2%) and HCs (13/15, 87.8%) had COVID-19 of mild severity. Conclusions: PwMS treated with ocrelizumab developed diminished humoral and robust cellular responses following two and three SARS-CoV-2 vaccinations. The obtained immunity after SARS-CoV-2 vaccination may translate into lower incidence and severity of COVID-19. 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

Antibody-based agents have become a preferred treatment for various diseases, including cancer, due to significant advances in antibody engineering. The use of single-chain Fv-Fcs (scFv-Fcs) has been a promising engineering approach for therapeutic design. The concept is that the Fc provides increased stability and target binding and ultimately improves performance. However, the structural and dynamic relationship between the variable and Fc domains, which are fused in close proximity, and the impact on stability and target binding are not well understood. This study evaluated trastuzumab-derived scFv-Fc antibodies, focusing on the impact of their design on important biopharmaceutical parameters. Computational modelling and molecular dynamics, alongside experimental studies, were used to ascertain their dynamics, expression and purification, stabilities, and binding potencies. The results showed that the scFv subunits exhibited stochastic interplays that lead to diverse shapes and were associated with functional performance. This new understanding of scFv-Fc antibodies and their structural and functional nuances provides important details to further guide the design of more effective and less toxic therapeutics. Full article

Background: The emergence of several paramyxoviruses, including Nipah virus (NiV), makes continued efforts in vaccine development as part of pandemic preparedness efforts necessary. Although NiV is a zoonotic pathogen with high case fatality, there is still no licensed vaccine. Methods: Herein, NiV attachment glycoprotein G (NiV-G), which is crucial to host cell receptor binding, was used to develop Nipah epitope-based peptide vaccines. A total of 39 B- and T-cell epitopes of NiV-G were shortlisted for peptide synthesis and evaluation using in silico analysis. Results: The in vitro antigenicity evaluation of the peptide candidates showed eight synthesized peptides (G7, stalk-domain epitopes) with relatively high binding to NiV-G antibody-positive serum (A_450nm: 1.39–3.78). Moreover, nine-mer (9-mer) peptides were found to be less reactive than their longer peptide counterparts (15–30 aa, G7-1, and G7-4), but 9-mer activity was enhanced with cyclization (NPLPFREYK, A_450nm: 2.66) and C-terminal amidation modification (NPLPFREYK-NH2, A_450nm: 1.39). Subsequently, in vivo validation in immunized mice revealed the immunogenicity potential of the G7-1 peptide vaccine (30 aa, NENVNEKCKFTLPPLKIHECNISCPNPLPF) to elicit a strong antigen-specific antibody response against their homologous peptide antigen (I.V., A_450nm: 1.48 ± 0.78; I.M., A_450nm: 1.66 ± 0.66). However, antibody binding to recombinant NiV-G protein remained low, suggesting limited recognition to the native antigen. Conclusions: This study focused on the preliminary screening and validation of peptide vaccines using single formulations with minimal modifications in the peptide candidates. Our findings collectively show the immunogenic potential of the NiV-G stalk-based epitope peptide vaccine as a novel therapeutic for NiV and underscores the need for strategic design, delivery, and formulation optimization to enhance its protective efficacy and translational application. Full article