Objective To screen the anti-CD22-specific nanobodies to provide a basis for immunotherapy agents. Methods The naive phage nanobody library was constructed and its diversity was analyzed. Three rounds of biotinylated streptavidin liquid phase screening were performed by using biotinylated CD22 antigen as the target, and the sequence of nanobodies against CD22 were identified by ELISA and gene sequencing. Results The capacity of the constructed naive phage nanobody library was 3.89×10⁹ CFU/mL, and the insertion of effective fragments was higher than 85%. Based on this library, seven anti-human CD22 nanobodies were screened, and the amino acid sequence comparison results showed that the overall similarity was 70.34%, and all of them were hydrophilic proteins. The results of protein-protein complex docking prediction showed that the mimetic proteins of the five nanobody sequences could be paired and linked to CD22, and the main forces were hydrophobic interaction and hydrogen bonding. Conclusion This study provided a basis for the study of chimeric antigen receptor T cells targeting CD22, successfully constructed the natural phage nanobody library and obtaining five anti-CD22-specific nanobodies.
Camelus/immunology* ; Single-Domain Antibodies/chemistry* ; Peptide Library ; Humans ; Animals ; Sialic Acid Binding Ig-like Lectin 2/genetics* ; Amino Acid Sequence ; Molecular Docking Simulation

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

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

Nanobodies (Nbs), the unique single-domain antibodies discovered in the species of Camelidae and sharks, are also known as the variable domain of the heavy chain of heavy-chain antibody (VHH). They offer strong antigen targeting and binding capabilities and overcome the drawbacks such as large size, low stability, high immunogenicity, and slow clearance of conventional antibodies. Nbs can be boosted by bioconjugation with toxins, enzymes, radioactive nucleotides, fluorophores, and other functional groups, demonstrating potential applications in the diagnosis and treatment of human and animal diseases. This article introduces the structures and characteristics of Nbs, the construction and screening of Nb libraries, and the strategies for affinity maturation and then reviews the current applications of Nbs in diagnosis and treatment, providing a reference for the development of diagnostic reagents and clinical therapies for infectious diseases.
Single-Domain Antibodies/chemistry* ; Animals ; Humans ; Camelidae/immunology*

Nanobody is a kind of antibody from camel, which misses light chain. Nanobody has the same antigen binding specificity and affinity as mAb. Moreover, because of its small molecular weight, high stability and easy preparation, nanobody has great value of biomedical applications. In this study, we successfully prepared highly pure antiEGFR nanobody in E.coli using genetic engineering techniques. Cell proliferation assay (CCK-8 assay) and migration experiments (cell scratch test and Transwell assay) indicated that the recombinant antiEGFRnano can significantly inhibit the proliferation and migration of endometrial cancer cells. These results provide a new way of thinking and methods for EGFR-targeted therapy of endometrial cancer.
Adenocarcinoma ; metabolism ; pathology ; Amino Acid Sequence ; Base Sequence ; Cell Line, Tumor ; Cell Movement ; drug effects ; Cell Proliferation ; drug effects ; Endometrial Neoplasms ; metabolism ; pathology ; Escherichia coli ; metabolism ; Estrogens ; metabolism ; Female ; Genetic Vectors ; Humans ; Plasmids ; Receptor, Epidermal Growth Factor ; genetics ; immunology ; Recombinant Proteins ; metabolism ; Single-Domain Antibodies ; genetics ; pharmacology

Small molecule antibodies are naturally existed and well functioned but not structurally related to the conventional antibodies. They are only composed of heavy protein chains or light chains, much smaller than common antibody. The first small molecule antibody, called Nanobody was engineered from heavy-chain antibodies found in camelids. Cartilaginous fishes also have heavy-chain antibodies (IgNAR, "immunoglobulin new antigen receptor"), from which single-domain antibodies called Vnar fragments can be obtained. In addition, free light chain (FLC) antibodies in human bodies are being developed as therapeutic and diagnostic agents. Comparing to intact antibodies, common advantages of small molecule antibodies are with better solubility, tissue penetration, stability towards heat and enzymes, and comparatively low production costs. This article reviews the structural characteristics and mechanism of action of the Nanobody, IgNAR and FLC.
Animals ; Camelids, New World ; immunology ; Humans ; Immunoglobulin Light Chains ; chemistry ; immunology ; Receptors, Antigen ; immunology ; Sharks ; immunology ; Single-Chain Antibodies ; chemistry ; immunology ; therapeutic use ; Single-Domain Antibodies ; chemistry ; immunology ; therapeutic use