No abstract available.
Antibodies* ; Molecular Biology* ; Single-Chain Antibodies*

OBJECTIVETo construct human phage single-chain antibody (scFv) library against breast cancer, and to identify anti-HER2 specific antibodies from the human phage display scFv library to offer a stronger affinity sequence targeting HER2 for fusion protein targeting HER2 and CXCR4.

METHODSTotal RNA was extracted from the adjacent lymphatic tissue harvested from breast cancer patients. The variable regions of the whole antibody were amplified by using RT-PCR and were cloned into the vector pCANTAB-5E through a linker. The products were electroporated into competent E.coli TG1 cells. Recombinant phages specific for breast cancer cells were enriched in SKBR-3 after four rounds. The antigen-positive clones were selected by ELISA and immunohistochemistry.

RESULTSThe fragment of VH and VL were about 375 and 330 bp and were linked in vitro to form scFv of 750 bp that was resistant to the breast cancer HER2 single strand. A fusion phage display library that contained total of 2.48×10(8) pfu /ml was established. ELISA and immunohistochemical results confirmed that the antibody has a strong affinity with HER2 antigen in breast cancer tissue. Compared to human IgG antibody, a scFv phage library against human breast cancer was successfully constructed with high capacity. The scFv was highly specific to HER2 antigen and the sequencing results indicated that VL and VH genes were highly homologous with the variable region of human antibody.

CONCLUSIONThis strategy may achieve new targeted antibody resistant to the breast cancer for clinical treatment and provide a carrier that uses HER2 as a target of the fusion protein for anti-tumor therapy.

Breast Neoplasms ; genetics ; immunology ; Female ; Humans ; Peptide Library ; Receptor, ErbB-2 ; immunology ; Single-Chain Antibodies ; immunology

Asthma is a common respiratory disease that affects 300 million of people worldwide, posing a serious health risk and medical burden. Development of new anti-asthmatic drugs and alternative treatment regimens is therefore encouraged. Recent studies have shown that Epidermal Growth Factor Receptor (EGFR) is involved in asthma development. In order to construct nanoparticles targeting EGFR for asthma treatment, a single chain antibody fragment (scFv) against EGFR was genetically engineered and modified at the N-terminal end of the human ferritin H-chain (FTH1) to construct Anti EGFR scFv::FTH1/FTH1 nanoparticles. Transmission electron microscopy showed that the nanoparticles were self-assembled into hollow cage-like structures with the particle size of about 12 nm. Semi-quantitative analysis of the purified nanoparticles by SDS-PAGE revealed the mass ratio of FTH1 to Anti EGFR scFv::FTH1 was 7:3. In House Dust Mite (HDM) driven models, Anti EGFR scFv::FTH1/FTH1 nanoparticles efficiently attenuated several key features of asthma, including goblet cell hyperplasia, mucous metaplasia and subepithelial fibrosis, showing the potential of using ferritin based nanoparticle for asthma treatment.
Asthma/drug therapy* ; Ferritins ; Humans ; Nanoparticles ; Oxidoreductases ; Single-Chain Antibodies/genetics*

The existence of cancer stem cells is regarded as the major cause for therapeutic resistance and relapse of a variety of cancer types including hepatocellular carcinoma (HCC). However, the tracing of such a subpopulation in vivo has been challenging. We have previously demonstrated that the isoform 5 of the voltage-gated calcium channel α2δ1 subunit, which can be recognized specifically by a monoclonal antibody 1B50-1, is a bona fide surface marker for HCC stem cells. Here we developed a strategy for optical imaging of α2δ1-positive cells by using a fusion protein containing the single chain variable fragment (scFv) of Mab1B50-1 and the luciferase NanoLuc which was tagged with Flag in the C-terminal. The scFv of Mab1B50-1 was fused to the N-terminal of NanoLucFlag using overlap PCR, and the recombinant fragment, which was named as 1B50-1scFv-NanoLucFlag, was subsequently cloned into a eukaryotic expression vector. The resulting construct was transfected into FreeStyle 293F cells in suspension using PEI reagent. The expression of the fusion protein was identified as a protein with molecular weight about 50 kDa by Western blotting. After purification by ANTI-FLAG® M2 affinity chromatography, 1B50-1scFv-NanoLucFlag was demonstrated to bind to α2δ1 positive cells specifically with a Kd value of (18.62±1.84) nmol/L. Furthermore, a strong luciferase activity of 1B50-1scFv-NanoLucFlag was detected in α2δ1 positive cells following incubation with the fusion protein, indicating that the presence of α2δ1 could be quantified using this fusion protein. Hence, 1B50-1scFv-NanoLucFlag provides a potential tool for optical imaging of α2δ1 positive cancer stem cells both in vitro and in vivo.
Carcinoma, Hepatocellular ; Humans ; Liver Neoplasms ; Neoplastic Stem Cells ; Recombinant Proteins/genetics* ; Single-Chain Antibodies/genetics*

Objective: To construct humanized anti-CD19 chimeric antigen receptor T cells and investigate its ability to kill leukemia cells in vitro and in vivo. Methods: Humanized anti-human CD19 antibody with a high affinity was obtained based on mouse anti-human CD19 antibody (FMC63). Humanized CD19 CAR-T cells (hCART19) were constructed through transfection of lentivirus carrying a CAR sequence of humanized anti-CD19 scFv into human peripheral CD3(+) T cells. The ability of hCART19 to kill leukemia cells and secrete cytokines was detected by LDH release assay and ELISA. The in vivo tumor-killing effect of hCART19 was evaluated in a leukemia mouse model. Results: Several different humanized CD19 single-chain antibodies which were constructed by IMGT database were expressed in the eukaryotic expression vector and purified followed by acquiring humanized CD19 antibody (Clone H3L2) with similar binding ability to FMC63. Humanized CD19 CAR lentivirus vector was constructed and transfected into T cells to obtain hCART19 cells. The LDH release experiment confirmed that the killing rate of target cells was increased gradually along with the increased E/T ratio. When the ratio of E/T was 10∶1, the killing rate of target cells by hCART19 reached a maximum. When Raji cells were used as target cells, the hCART19 cells group had a significantly higher kill rate [(87.56±1.99)%] than the untransduced T cells group [(19.31±1.16)%] and the control virus transduced T cells group [(21.35±1.19)%](P<0.001). ELISA analysis showed that the secretion of IL-2 [ (10.56±0.88) pg/ml] and IFN-γ [ (199.02±12.66) pg/ml] in the hCART19 cells group were significantly higher than those in the untransduced T cells group [IL-2: (3.55±0.26) pg/ml; IFN-γ: (37.63±0.85) pg/ml] and the control virus transduced T cells group [IL-2: (2.92±0.32) pg/ml; IFN-γ: (52.07±3.33) pg/ml](P<0.001). The above experiments also showed similar results when CHO-K1-CD19 cells were used as target cells. Moreover, in a human leukemia xenograft animal model, the results showed that mice in the untransduced T cells group and the control virus transduced T cells group all died within 20 to 30 days, and the hCART19 cell group survived >40 days, which was more than the survival time of the other two groups of mice. The difference was statistically significant (χ(2)=11.73, P=0.008). Conclusion: Humanized CD19 CAR-T cells with anti-leukemic activity have been successfully constructed, which will lay a foundation for clinical studies in the future.
Animals ; Antigens, CD19 ; Cricetinae ; Cytokines ; Humans ; Lentivirus ; Mice ; Single-Chain Antibodies ; T-Lymphocytes

Single chain antibody fragment (scFv) is a small molecule composed of a variable region of heavy chain (VH) and a variable region of light chain (VL) of an antibody, and these two chains are connected by a flexible short peptide. scFv is the smallest functional fragment with complete antigen-binding activity, which contains both the antibody-recognizing site and the antigen-binding site. Compared with other antibodies, scFv has the advantages of small molecular weight, strong penetration, low immunogenicity, and easy expression. Currently, the most commonly used display systems for scFv mainly include the phage display system, ribosome display system, mRNA display system, yeast cell surface display system and mammalian cell display system. In recent years, with the development of scFv in the field of medicine, biology, and food safety, they have also attracted much attention in the sectors of biosynthesis and applied research. This review summarizes the advances of scFv display systems in recent years in order to facilitate scFv screening and application.
Animals ; Immunoglobulin Variable Region/genetics* ; Immunoglobulin Fragments/metabolism* ; Single-Chain Antibodies/metabolism* ; Peptide Library ; Mammals/genetics*

We present a bispecific antibody that recognizes an antigen and a hapten and can be applied to various biological assays, including immunoblotting and immunoprecipitation. In immunoblot analysis of serum, an anti-C5 x anti-cotinine bispecific tandem single-chain variable fragment (scFv)-Fc fusion protein and cotinine-conjugated horseradish peroxidase (HRP) generated a clean signal without the high background that was observed in a parallel experiment using HRP-conjugated goat anti-rabbit immunoglobulin G (Fc-specific) antibody. In immunoprecipitation analysis of serum, use of the bispecific tandem scFv-Fc fusion protein and cotinine-crosslinked magnetic beads significantly reduced the amount of protein contaminants compared with a parallel experiment done with protein A agarose beads. In subsequent immunoblot analysis, use of cotinine-HRP as the secondary probe instead of HRP-conjugated goat anti-rabbit IgG (Fc-specific) antibody successfully eliminated the band corresponding to the bispecific tandem scFv-Fc fusion protein.
Animals ; Antibodies, Bispecific/*immunology ; HEK293 Cells ; Haptens/*immunology ; Humans ; Immunoblotting/*methods ; Immunoprecipitation/methods ; Rabbits ; Single-Chain Antibodies/immunology

To screen the specific anti-human intercellular adhesion molecule-1 (ICAM-1) single chain fragment variable (scFv) using phage display library technology and to identify its biological activity. P1 peptide was used as antigen, and the phage antibodies against human ICAM-1 antigen were panned by four binding-eluting-amplifying cycles using Tomlinson I+J phage display library. After four rounds of selective enrichment screening, the positive clones were determined by PCR, enzyme linked immunosorbent assay (ELISA)-based antigenic cross reaction and Dot blotting. Then the binding specificity and biological activity of purified scFv were identified by Western blotting, competitive ELISA and cell adhesion inhibition assay respectively. Furthermore, four positive clones were first panned through P1 peptide coated-ELISA assay, and then J-A1 was obtained and identified by PCR, ELISA-based antigenic cross reaction and Dot blotting, which could show a specific binding between P1 peptide and human ICAM-1 protein antigen. Subsequently, the purified scFv showed a satisfactory specificity and anti-adhesive activity in competitive ELISA and the cell adhesion inhibition assay. The specific anti-human ICAM-1 scFv was prepared successfully from Tomlinson I+J phage display library, which pave the way for further application of anti-human ICAM-1 scFv for inflammation diseases therapeutics.
Antibodies ; Enzyme-Linked Immunosorbent Assay ; Humans ; Immunoglobulin Variable Region ; Intercellular Adhesion Molecule-1 ; immunology ; Peptide Library ; Single-Chain Antibodies

Phage display technology provides a powerful tool to screen a library for a binding molecule via an enrichment process. It has been adopted as a critical technology in the development of therapeutic antibodies. However, a major drawback of phage display technology is that because the degree of the enrichment cannot be controlled during the bio-panning process, it frequently results in a limited number of clones. In this study, we applied next-generation sequencing (NGS) to screen clones from a library and determine whether a greater number of clones can be identified using NGS than using conventional methods. Three chicken immune single-chain variable fragment (scFv) libraries were subjected to bio-panning on prostate-specific antigen (PSA). Phagemid DNA prepared from the original libraries as well as from the Escherichia coli pool after each round of bio-panning was analyzed using NGS, and the heavy chain complementarity-determining region 3 (HCDR3) sequences of the scFv clones were determined. Subsequently, through two-step linker PCR and cloning, the entire scFv gene was retrieved and analyzed for its reactivity to PSA in a phage enzyme immunoassay. After four rounds of bio-panning, the conventional colony screening method was performed for comparison. The scFv clones retrieved from NGS analysis included all clones identified by the conventional colony screening method as well as many additional clones. The enrichment of the HCDR3 sequence throughout the bio-panning process was a positive predictive factor for the selection of PSA-reactive scFv clones.
Antibodies ; Bacteriophages ; Chickens ; Clone Cells* ; Cloning, Organism ; Complementarity Determining Regions ; DNA ; Escherichia coli ; Immunoenzyme Techniques ; Mass Screening ; Methods ; Polymerase Chain Reaction ; Prostate-Specific Antigen ; Single-Chain Antibodies

BACKGROUND: In order to characterize human antibodies with specificity for mite allergens at the molecular level, a scFv phage display library was constructed using peripheral blood mononuclear lymphocytes from an asthma patient allergic to mite as Ig gene sources. METHODS: Immunoglobulin VH and V gene fragments were obtained by polymerase chain reaction, and randomly combined in pCANTAB-5E vector. The resulting human scFv phage display library had 3 X 10(4) independent clones, and biopanning was performed with house dust mite extracts. RESULTS: Four scFv clones specific for house dust mite extract were isolated. Immunoblot assay showed that our clones reacted to 25 kDa and 50~60 kDa proteins with unknown identity in mite extracts. Sequence analysis indicated that two clones (b7 and c15) are identical, and all clones belong to human VH3 subgroup. On the other hand, light chain usage was different in that two clones (a2 and b7/c15) belonging to V kappa 4 subgroup, but a4 used V kappa 1 light chain gene. CONCLUSION: Our approach should facilitate provision of useful information on the antibody responses against allergens at the molecular level in humans.
Allergens ; Antibodies ; Antibody Formation ; Asthma* ; Bacteriophages* ; Clone Cells ; Dust* ; Genes, Immunoglobulin ; Hand ; Humans* ; Immunoglobulins ; Lymphocytes ; Mites ; Polymerase Chain Reaction ; Pyroglyphidae* ; Sensitivity and Specificity ; Sequence Analysis ; Single-Chain Antibodies*