Highly Specific Monoclonal Antibody Targeting the Botulinum Neurotoxin Type E Exposed SNAP-25 Neoepitope

Generation and Next-Generation Sequencing-Based Characterization of a Large Human Combinatorial Antibody Library

Antibody phage display is a key technology for the discovery and development of target-specific monoclonal antibodies (mAbs) for use in research, diagnostics, and therapy. The construction of a high-quality antibody library, with larger and more diverse antibody repertoires, is essential for the successful development of phage display-derived mAbs. In this study, a large human combinatorial single-chain variable fragment library (1.5 × 10¹¹ colonies) was constructed from Epstein-Barr virus-infected human peripheral blood mononuclear cells stimulated with a combination of two of the activators of human B cells, the Toll-like receptor 7/8 agonist R848 and interleukin-2. Next-generation sequencing analysis with approximately 1.9 × 10⁶ and 2.7 × 10⁶ full-length sequences of heavy chain variable (VH) and κ light chain variable (Vκ) domains, respectively, revealed that the library consists of unique VH (approximately 94%) and Vκ (approximately 91%) sequences with greater diversity than germline sequences. Lastly, multiple unique mAbs with high affinity and broad cross-species reactivity could be isolated from the library against two therapeutically relevant target antigens, validating the library quality. These findings suggest that the novel antibody library we have developed may be useful for the rapid development of target-specific phage display-derived recombinant human mAbs for use in therapeutic and diagnostic applications.

Novel botulinum neurotoxin-A tibial nerve perineural injection to alleviate overactive bladder symptoms in male rats

Although tibial nerve modulation has shown to induce positive changes in the overactive bladder (OAB), prolonged therapeutic effects using percutaneous stimulation have not yet been achieved. Intradetrusor onabotulinum toxin A injection can provide prolonged therapeutic effects; however, its delivery requires invasive measures. By applying local relief of tibial nerve neural entrapment with onabotulinum toxin A injection, this study investigated the feasibility and efficacy of combining the abovementioned two therapeutic strategies. An OAB animal model was developed using 12 adult Sprague-Dawley rats with cyclophosphamide intraperitoneal injection. A perineural injection site comparable to the tibial nerve perineural injection site and corresponding to that in humans was identified and developed in rats. The toxin was injected five days after establishing the OAB. The incision was made in the skin on the lateral surface of the thigh. The biceps femoris muscle was cut across, exposing the sciatic nerve and its three terminal branches: the sural, common peroneal, and tibial nerves, and 100 units of onabotulinum toxin A was injected into the surrounding tissue. Five days following injection, cystometry was performed. Inter-contraction time, contraction pressure, and interval of the disease state improved with statistical significance. The OAB animal model showed significant improvement with the tibial nerve perineural injection of botulinum toxin, thereby suggesting the possibility of a comparable treatment adaptation in humans.

EGFRvⅢ-targeted immunotoxin combined with temozolomide and bispecific antibody for the eradication of established glioblastoma

EGFRvⅢ is an established target for immunotherapy of glioblastoma (GBM). Current study aims to explore the efficacy of EGFRvⅢ-targeted immunotoxin combined with temozolomide (TMZ) or T cell-engaged bispecific antibody for the treatment of GBM. We generated three rabbit monoclonal antibodies (R1, R2, and R6) that specifically bound to EGFRvⅢ, but not EGFR, with high affinity. Immunotoxins were made by fusing the scFv of these antibodies with engineered Pseudomonas exotoxin PE24. The in vitro cytotoxicity and specificity of the immunotoxins was rigorously validated by EGFRvⅢ and EGFR-expressed cell lines. The in vivo efficacy of immunotoxin monotherapy and in combination with TMZ or EGFRvⅢ-targeted bispecific antibody was evaluated in orthotopic and subcutaneous xenograft mouse models. EGFRvⅢ immunotoxins potently killed U87, U251 and GL261 cells that were forcefully expressing EGFRvⅢ, with IC₅₀ values bellow 1.2 ng/ml. In a subcutaneous model, multiple intratumoral injections of immunotoxin at a dose of 2 mg/kg resulted in complete tumor regression in 3/5 of mice. In a C57BL/6 orthotopic glioblastoma model transplanted with GL261 cells that expressed a mouse version of EGFRvⅢ, two injections of 10 micrograms of immunotoxin in the lateral ventricles significantly improved the survival, with 2/5 mice being completely cured. Furthermore, in a subcutaneous xenograft model transplanted with EGFRvⅢ-expressed U87 cells, a single intratumoral injection of immuntoxin followed by i.v. injections of TMZ or EGFRvⅢ-targeted bispecific antibody achieved complete regression in mice. Taken together, EGFRvⅢ immunotoxin combined with TMZ or T cell-engaged bispecific antibody offers promise for curative treatment of GBM.

Detection of VAMP Proteolysis by Tetanus and Botulinum Neurotoxin Type B In Vivo with a Cleavage-Specific Antibody

Tetanus and Botulinum type B neurotoxins are bacterial metalloproteases that specifically cleave the vesicle-associated membrane protein VAMP at an identical peptide bond, resulting in inhibition of neuroexocytosis. The minute amounts of these neurotoxins commonly used in experimental animals are not detectable, nor is detection of their VAMP substrate sensitive enough. The immune detection of the cleaved substrate is much more sensitive, as we have previously shown for botulinum neurotoxin type A. Here, we describe the production in rabbit of a polyclonal antibody raised versus a peptide encompassing the 13 residues C-terminal with respect to the neurotoxin cleavage site. The antibody was affinity purified and found to recognize, with high specificity and selectivity, the novel N-terminus of VAMP that becomes exposed after cleavage by tetanus toxin and botulinum toxin type B. This antibody recognizes the neoepitope not only in native and denatured VAMP but also in cultured neurons and in neurons in vivo in neurotoxin-treated mice or rats, suggesting the great potential of this novel tool to elucidate tetanus and botulinum B toxin activity in vivo.