Antibody-drug conjugates (ADCs) represent a promising class of targeted cancer therapeutics that combine the specificity of monoclonal antibodies with the potency of cytotoxic payloads. Despite their therapeutic potential, the use of ADCs faces significant challenges, including off/on-target toxicity and resistance development. This review examines the current landscape of ADC development, focusing on the critical aspects of target selection and antibody engineering. We discuss strategies to increase ADC efficacy and safety, including multitarget approaches, pH-dependent antibodies, and masked peptide technologies. The importance of comprehensive antigen expression profiling in both tumor and normal tissues is emphasized, highlighting the role of advanced technologies, such as single-cell sequencing and artificial intelligence, in optimizing target selection. Furthermore, we explore combination therapies and innovations in linker‒payload chemistry, which may provide approaches for expanding the therapeutic window of ADCs. These advances pave the way for the development of more precise and effective cancer treatments, potentially extending ADC applications beyond oncology.
Humans ; Immunoconjugates/adverse effects* ; Neoplasms/immunology* ; Animals ; Antibodies, Monoclonal/therapeutic use* ; Antineoplastic Agents/therapeutic use*

Neutralizing antibodies have been designed to specifically target and bind to the receptor binding domain (RBD) of spike (S) protein to block severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus from attaching to angiotensin converting enzyme 2 (ACE2). This study reports a distinctive nanobody, designated as VHH21, that directly catalyzes the S-trimer into an irreversible transition state through postfusion conformational changes. Derived from camels immunized with multiple antigens, a set of nanobodies with high affinity for the S1 protein displays abilities to neutralize pseudovirion infections with a broad resistance to variants of concern of SARS-CoV-2, including SARS-CoV and BatRaTG13. Importantly, a super-resolution screening and analysis platform based on visual fluorescence probes was designed and applied to monitor single proteins and protein subunits. A spontaneously occurring dimeric form of VHH21 was obtained to rapidly destroy the S-trimer. Structural analysis via cryogenic electron microscopy revealed that VHH21 targets specific conserved epitopes on the S protein, distinct from the ACE2 binding site on the RBD, which destabilizes the fusion process. This research highlights the potential of VHH21 as an abzyme-like nanobody (nanoabzyme) possessing broad-spectrum binding capabilities and highly effective anti-viral properties and offers a promising strategy for combating coronavirus outbreaks.
Single-Domain Antibodies/immunology* ; Spike Glycoprotein, Coronavirus/metabolism* ; SARS-CoV-2/immunology* ; Animals ; Humans ; Antibodies, Neutralizing/immunology* ; Camelus ; COVID-19/immunology* ; Antibodies, Viral/immunology* ; Angiotensin-Converting Enzyme 2

To prepare antibodies that specifically recognize the conserved domain in the large extracellular loop of the CD63 protein, we expressed anti-CD63 single-chain variable fragment (scFv) antibody in Pichia pastoris in a secreted form. The purified expression product was found to bind specifically with CD63 protein and recognize CD63 on the surface of SK-MEL-28 cells. The variable region of the anti-CD63 monoclonal antibody in an anti-CD63-positive cell line was sequenced. The anti-CD63 scFv consisted of a variable heavy chain and a variable light chain linked by a flexible peptide was then designed. After codon optimization, the gene was synthesized and cloned into the expression plasmid pPICZα-A. The SacI-linearized plasmid was electroporated into P. pastoris X33, and 1% methanol were used to induce the expression of scFv. The fermentation supernatant was purified by Ni column. Anti-CD63 scFv was identified by SDS-PAGE and Western blotting, and its biological activities were analyzed by immunoblotting, immunofluorescence, cell-based ELISA, and flow cytometry. A P. pastoris strain capable of expressing and secreting anti-CD63 scFv was successfully obtained. The antibody had a molecular weight of approximately 30 kDa and specifically recognized CD63 protein. The expression of anti-CD63 scFv in P. pastoris paves the way for the production of anti-CD63 antibodies on a large-scale, which is undoubtedly an economical and effective way of antibody acquisition.
Single-Chain Antibodies/immunology* ; Humans ; Tetraspanin 30/immunology* ; Recombinant Proteins/immunology* ; Pichia/genetics* ; Saccharomycetales/metabolism*

This study is designed to address the development, synthesis, and screening of non-animal-derived nanoantibody libraries. Furthermore, it seeks to elucidate the impact of framework region selection and complementarity-determining region (CDR) design on the characteristics of synthesized nanoantibody libraries. These investigations aim to establish a robust theoretical and technical foundation for enhancing the efficacy, diversity, and practical applicability of synthetic nanoantibody libraries. In this study, a new framework (IGHV3S65*01-IGHJ4*01) was identified based on the high-throughput sequencing results of natural nanobodies, and degenerate primers were designed based on the frequency of amino acids at each position in the complementarity-determining region (CDR) region to synthesize the coding fragments of nanobodies by overlap PCR. After 40 times of electro-transformation, a single-frame synthesized nanobody library (SS-Library) containing 6×10⁹ clones was obtained, and the titer of the library was demonstrated to be 10¹³ PFU/mL after rescue by the helper phage M13K07. Random 48 single colonies were picked for PCR, which revealed an insertion rate of 95.8%. Sanger sequencing results showed that 38 clones had complete sequences, none of which showed cysteines or stop codons, and no identical sequences appeared, suggesting that the library had higher diversity. The library was screened and validated with three antigens, including bovine serum albumin (BSA), acetylcholinesterase (AchE), and immunoglobulin G (IgG). Finally, 2 nanobodies against BSA, 10 against AchE, and 15 against IgG were obtained. One positive clone of each antigen was singled out for recombinant expression, and the results showed that all the three nanobodies were expressed in a soluble form. The binding activity of recombinantly expressed nanobodies was evaluated using indirect enzyme-linked immunosorbent assay (ELISA) and bio-layer interferometry (BLI). The results demonstrated that the anti-AChE and anti-IgG nanobodies exhibited specific binding to their respective antigens, with affinity constants (KD) of 294 nmol/L and 250 nmol/L, respectively. The nanobody synthetic library preparation method proposed in this study is simple and easy to use with low preference, and it is expected to be a universal nanobody discovery platform for the preparation and development of lead specific nanobodies.
Single-Domain Antibodies/biosynthesis* ; Peptide Library ; Complementarity Determining Regions/immunology* ; Animals

Hemoglobin, the principal protein in red blood cells, is crucial for oxygen transport in the bloodstream. The quantification of hemoglobin concentration is indispensable in medical diagnostics and health management, which encompass the diagnosis of anemia and the screening of various blood disorders. Immunological methods, based on antigen-antibody interactions, are distinguished by their high sensitivity and accuracy. Consequently, it is necessary to develop hemoglobin-specific antibodies characterized by high specificity and affinity to enhance detection accuracy. In this study, we immunized a Bactrian camel (Camelus bactrianus) with human hemoglobin and subsequently constructed a nanobody library. Utilizing a solid-phase screening method, we selected nanobodies and evaluated the binding activity of the screened nanobodies to hemoglobin. Initially, human hemoglobin was used to immunize a Bactrian camel. Following four immunization sessions, blood was withdrawn from the jugular vein, and a nanobody library with a capacity of 2.85×10⁸ colony forming units (CFU) was generated. Subsequently, ten hemoglobin-specific nanobody sequences were identified through three rounds of adsorption-elution-enrichment assays, and these nanobodies were subjected to eukaryotic expression. Finally, enzyme-linked immunosorbent assay and biolayer interferometry were employed to evaluate the stability, binding activity, and specificity of these nanobodies. The results demonstrated that the nanobodies maintained robust binding activity within the temperature range of 20-40 ℃ and exhibited the highest binding activity at pH 7.0. Furthermore, the nanobodies were capable of tolerating a 10% methanol solution. Notably, among the nanobodies tested, VHH-12 displayed the highest binding activity to hemoglobin, with a half maximal effective concentration (EC₅₀) of 10.63 nmol/L and a equilibrium dissociation constant (K_D) of 2.94×10^-7 mol/L. VHH-12 exhibited no cross-reactivity with a panel of eight proteins, such as ovalbumin and bovine serum albumin, while demonstrating partial cross-reactivity with hemoglobin derived from porcine, goat, rabbit, and bovine sources. In this study, a hemoglobin-specific high-affinity nanobody was successfully isolated, demonstrating potential applications in disease diagnosis and health monitoring.
Animals ; Camelus/immunology* ; Single-Domain Antibodies/immunology* ; Hemoglobins/immunology* ; Humans ; Peptide Library

Bio-mineralization has emerged as a promising strategy to enhance vaccine immunogenicity. This study optimized the calcium phosphate (CaP) mineralization process of foot-and-mouth disease virus-like particles (FMD VLPs) to achieve high mineralization efficiency and scalability. Key parameters, including concentrations of Ca²⁺, HPO₄^2-, NaCl, and VLPs, as well as stirring speed, were systematically optimized. Stability of the scaled-up reaction system and immunogenicity of the mineralized vaccine were evaluated. Optimal conditions [25.50 mmol/L Ca(NO₃)₂, 15 mmol/L Na₂HPO₄, 300 mmol/L NaCl, 0.75 mg/mL VLPs, and 1 500 r/min] yielded CaP-mineralized VLPs (VLPs-CaP) with high mineralization efficiency, uniform morphology, and a favorable particle size. Scaling up the reaction by 25 folds maintained consistent mineralization efficiency and particle characteristics. Immunization in mice demonstrated that VLPs-CaP induced higher titers of specific antibodies and neutralizing antibodies than unmineralized VLPs (P < 0.05). Higher IgG2a/IgG1 ratio and enhanced IFN-γ secretion (P < 0.05) further indicated robust cellular immune responses. We establish a stable and scalable protocol for VLPs-CaP, providing a theoretical and technical foundation for developing high-efficacy VLPs-CaP vaccines.
Vaccines, Virus-Like Particle/immunology* ; Immunogenicity, Vaccine ; Calcium Phosphates/chemistry* ; Foot-and-Mouth Disease Virus ; Biomineralization ; Particle Size ; Animals ; Mice ; Antibodies, Neutralizing/blood* ; Antibodies, Viral/blood* ; Immunity, Cellular

Pseudorabies (PR) is an infectious disease caused by the pseudorabies virus (PRV), affecting various domesticated and wild animals. Since pigs are the only natural hosts of PRV, PR poses a serious threat to the pig farming industry. Currently, PR is primarily prevented through vaccination with inactivated vaccines or genetically modified attenuated live vaccines. Developing safe and effective genetically engineered vaccines would facilitate the eradication and control of PR. In this study, the PRV vaccine strain Bartha-K61 was used as the reference strain. The gB protein was expressed via the baculovirus-insect cell expression system. Non-denaturing gel electrophoresis confirmed that the gB protein could form a trimeric structure. The purified gB protein was used to immunize mice, and the immune effect was evaluated by a challenge test. The results showed that the gB antigen induced a strong immune response in mice, with the serum-neutralizing antibody titer above 1:70. The lymphocyte stimulation index reached more than 1.29, and the level of (interferon gamma, IFN-γ) release was higher than 100 pg/mL. After immunization, mice were challenged with the virus at a dose of 10⁴ TCID₅₀/mL, 200 μL per mouse, and the clinical protection rate was 100%. Immunohistochemistry, histopathological section, and tissue viral load results showed that the pathological damage and viral load in the gB-immunized group were significantly lower than those in the PBS group. In summary, the gB protein obtained in this study induced strong humoral and cellular immune responses in mice, laying a foundation for developing a recombinant gB protein subunit vaccine.
Animals ; Mice ; Baculoviridae/metabolism* ; Viral Envelope Proteins/biosynthesis* ; Herpesvirus 1, Suid/genetics* ; Pseudorabies/immunology* ; Swine ; Pseudorabies Vaccines/genetics* ; Antibodies, Viral/blood* ; Insecta/cytology* ; Mice, Inbred BALB C ; Female ; Viral Vaccines/immunology*

Senecavirus A (SVA) is a major viral pathogen causing disease in pigs, and effective monitoring of SVA infection is critical for disease control. In this study, we aimed to develop a reliable ELISA method for rapidly detecting neutralizing antibodies against SVA. We used HEK293F cells to express an SVA-specific porcine Fab antibody and verified the biological activity of the Fab antibody by indirect ELISA, immunofluorescence assay, virus neutralization test, and Western blotting. The Fab antibody was biotinylated and used as a competitive antibody to establish a competitive ELISA (C-ELISA) for detecting neutralizing antibodies against SVA. We then evaluated the C-ELISA in terms of sensitivity, specificity, repeatability, and result agreement rate with the VNT. The results showed that we successfully prepared an SVA-specific porcine Fab antibody, which showed high affinity for SVA. We named this antibody 1M33Fab and designated it as Bio-1M33Fab after biotin labeling. The assay conditions were optimized as follows: the coating concentration of SVA particles being 1 μg/mL, the working concentration of Bio-1M33Fab being 0.5 μg/mL, the optimal serum dilution of 1:10, and the optimal dilution of enzyme-labeled avidin being 1:30 000. At a percent inhibition (PI) of 47%, the assay demonstrated the highest sensitivity (96.88%) and specificity (100%), with no cross-reactivity observed with the positive sera of major porcine viral diseases. The intra-assay coefficient of variation ranged from 1.12% to 7.34%, while the inter-assay coefficient of variation ranged from 1.10% to 8.97%, indicating good repeatability. In the detection of 224 clinical pig serum samples, C-ELISA and VNT showed a result agreement rate of 93.75%. In conclusion, we successfully develop a C-ELISA method for detecting neutralizing antibodies against SVA by using a porcine-derived Fab antibody, which lays a foundation for the development of detection kits.
Animals ; Swine ; Antibodies, Neutralizing/immunology* ; Enzyme-Linked Immunosorbent Assay/methods* ; Immunoglobulin Fab Fragments/immunology* ; Antibodies, Viral/immunology* ; Picornaviridae/immunology* ; Humans ; HEK293 Cells ; Swine Diseases/diagnosis* ; Picornaviridae Infections/diagnosis*

The global outbreak of monkeypox in 2022 has aroused widespread concern in public health. To date, the prevention and treatment of monkeypox has mainly relied on smallpox vaccines and drugs. This study aims to screen and obtain therapeutic antibodies with high affinity, neutralizing activity, and protective effects, and provide candidate molecules for the development of specific therapeutic antibodies against monkeypox. Therefore, humanized mice were immunized to screen for antibodies against the envelope protein of the mpox virus. Two M1R-specific antibodies, 12G5 and 12H6, were obtained, with the affinity of 0.095 nmol/L and 0.089 nmol/L, respectively. The 50% reduction of the plaque counts (PRNT₅₀) of 12G5 and 12H6 was (1.821±1.766) μg/mL and (17.605±2.383) μg/mL, respectively. The two antibodies targeted two binding epitopes of M1R. Moreover, 12H6 could protect 60% of mice from death following the vaccinia virus challenge. This study provides research materials for subsequent in-depth studies on the immunoprotection of mpox virus and potential therapeutic strategies.
Animals ; Mice ; Antibodies, Viral/immunology* ; Monkeypox virus/immunology* ; Mpox, Monkeypox/immunology* ; Antibodies, Neutralizing/immunology* ; Viral Envelope Proteins/immunology* ; Humans ; Antibodies, Monoclonal/biosynthesis* ; Female

Hemoglobin A1c (HbA1c) has a unique structure that makes monoclonal antibody (mAb) preparation challenging. This study aims to develop a method for preparing HbA1c mAbs and establish a fluorescent immunochromatographic assay (FICA) for rapid detection of HbA1c. Three glycosylated peptides were synthesized and used to prepare complete antigens, which were identified by dot enzyme-linked immunosorbent assay (Dot-ELISA) and ultraviolet absorption spectroscopy. The complete antigens and natural HbA1c were used for cross-immunization of mice, and the optimal complete antigen was selected. The mouse with the highest serum titer was chosen for mAb preparation. The purity and specificity of the mAbs were verified, and a FICA method was developed. The optimal complete antigen, with a titer of 1:512 000, was successfully prepared and selected. Fusion with splenocytes resulted in four specific HbA1c antibodies (purity > 90%). The best antibody exhibited a binding constant (Ka) of 1.67×10¹⁰ L/mol with the antigen. Based on this antibody, a FICA method was successfully established, capable of producing results within 15 min. The method demonstrated a good linear range (3%-13% HbA1c, y=0.071 3x+0.005 6, R²=0.993 7), recovery rates of 98%-102%, precision < 10.00%, and no nonspecific reactions. Clinical testing of 210 samples showed positive agreement of 96.36%, negative agreement of 97.00%, and overall agreement of 96.68%. The receiver operating characteristic (ROC) curve analysis yielded an area under curve (AUC) of 0.980 9 [95% confidence interval (CI): 0.961 0-1.000 0], with high consistency verified in multicenter studies. We successfully developed a key technique for preparing HbA1c monoclonal antibodies and established a FICA method for rapid detection of HbA1c. It will provide an efficient and convenient detection method for the early diagnosis and long-term management of diabetes and its complications.
Antibodies, Monoclonal/biosynthesis* ; Animals ; Mice ; Glycated Hemoglobin/immunology* ; Mice, Inbred BALB C ; Humans ; Antibody Specificity ; Chromatography, Affinity/methods* ; Enzyme-Linked Immunosorbent Assay/methods* ; Female