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*

CD96 (Tactile) is an adhesion receptor expressed mainly on activated T cells, NK cells. As a family member of the immunoglobulin-like cell receptor, CD96 consists of three immunoglobulin-like domains (V1, V2/C and C) in the extracellular region. Recent studies have shown that the 1st IgV domain of CD96 (CD96V1) plays an essential role in cell adhesion and NK cell-mediated killing. In this study, the 1st IgV domain of human CD96 (hCD96V1) was cloned and expressed in Escherichia coli (BL21). The soluble protein was obtained by refolding of the hCD96V1 inclusion bodies. From analytical ultracentrifugation, we could predict that CD96 V1 maily exists as dimer with approximate molecular weight of 26.9 kDa. The protein was then successfully crystallized using the sitting-drop vapour-diffusion method. The crystals diffracted to 1.9 angstrom resolution and belonged to space group P21, with unit-cell parameters a = 35.1, b = 69.5, c = 49.6A, alpha=gamma=90 degrees, beta=105.4 degrees.
Antigens, CD ; biosynthesis ; genetics ; Crystallization ; Crystallography ; methods ; Escherichia coli ; genetics ; metabolism ; Humans ; Immunoglobulin Variable Region ; biosynthesis ; genetics ; Protein Structure, Tertiary ; genetics ; Recombinant Proteins ; biosynthesis ; genetics

To prepare large naive phage antibody library, the host bacteria with high transformation efficiency is used in the Cre-LoxP recombination system. The variable regions of immunoglobulin light and heavy genes were amplified from lymphocytes collected from adult peripheral blood and newborn cord blood. The genes were spliced to form the single-chain variable fragments (scFv) by overlap PCR, cloned into pDAN5a vector and then transformed into XL2-blue MRF' with the Hte gene. Compared with XL1-blue strain, the size of the primary library was increased by 3.9 times. The primary library infected Cre recombinase-expressing bacteria, and the genes between phagemids created many new VH/VL combinations. The library was calculated to have a diversity of 1.7 x 10(11) and validated by the selection of antibodies against six different protein antigens. This library provides the basis for further selection of antibody-based drugs. It is the first time to report that XL2-blue MRF' can be used to improve the diversity of the library in the recombination system.
Adult ; Escherichia coli ; genetics ; immunology ; Genetic Vectors ; Humans ; Immunoglobulin Heavy Chains ; genetics ; Immunoglobulin Light Chains ; genetics ; Immunoglobulin Variable Region ; genetics ; Infant, Newborn ; Integrases ; metabolism ; Lymphocytes ; immunology ; Peptide Library ; Recombination, Genetic ; genetics ; Single-Chain Antibodies ; genetics ; metabolism ; Transformation, Genetic

Total mRNA was extracted from lymphocytes separated from the peripheral blood of allergic patients, and then variable region of heavy chain (VH) and variable region of light chain (VL) cDNA library were constructed by RT-PCR. Human scFv templates for rabbit reticulocyte lysate ribosome display were assembled by primers and linker peptide (Gly4Ser)3. mRNA bound in antibody-ribosome-mRNA complexes was recovered using in-situ single primer RT-PCR, and three rounds of anti-IgE scFv DNA were enriched. The target DNA fragments were double enzyme digested and ligated into plasmid pET22b (+), followed by transformation in E. coli Rosseta (DE3). Positive clones were screened using clone PCR, Dot blotting and antigen ELISA. The correct lengths of VH (400 bp) and VL (710 bp) PCR products were obtained. The expected 1,000 bp ribosome display templates were also observed in agarose gel electrophoresis. After three rounds of ribosome display target sequences were effectively enriched, leading to a library of 10(13) members. Antibodies with the highest ELISA value for IgE were generated in the strain pET-IgE-6. A human anti-IgE scFv library was successfully constructed as described herein. Ribosome display using single primer in-situ RT-PCR as the recovery procedure effectively enriched target sequences. Anti-IgE scFv with high affinity and specificity were identified. The prepared human anti-IgE scFv fragment might be self-developed to a lead drug for treating asthma. Our study provides an alternative method for rapid discovery of human antibodies of therapeutic importance.
Amino Acid Sequence ; Antibodies, Anti-Idiotypic ; genetics ; isolation & purification ; Antibody Affinity ; Asthma ; blood ; Base Sequence ; DNA, Complementary ; metabolism ; Escherichia coli ; metabolism ; Humans ; Immunoglobulin Heavy Chains ; genetics ; Immunoglobulin Light Chains ; genetics ; Immunoglobulin Variable Region ; genetics ; Lymphocytes ; chemistry ; Peptide Library ; RNA, Messenger ; isolation & purification ; Recombination, Genetic ; genetics ; Ribosomes ; chemistry ; genetics ; immunology ; Single-Chain Antibodies ; genetics ; isolation & purification ; Transformation, Genetic

This study was aimed to analyze the clinical and laboratorial characteristics of patients with chronic lymphocytic leukemia (CLL), as well as their relationship with outcomes of patients. The clinical and laboratorial data of 40 CLL patients admitted from 2004 to 2010 in our hospital were analyzed retrospectively. The results indicated that the most of CLL attacked the elderly male patients with median age 66 (from 42 to 80). Flow cytometric analysis showed that 25 cases were positive for typical immunophenotype of CLL. On the other hand, all the patients clearly expressed CD19 and CD5, 7 cases (17.5%) and 14 cases (35%) were positive for the expression of CD38 and Zap70 respectively. 8 cases harbored a mutated immunoglobulin heavy-chain (VH) gene, among them 4 cases belong to VH3 family. Interphase FISH analysis showed that P53 deletion, RB1 deletion, trisomy 12 and normal chromosome were detected in 6, 3, 1, and 5 cases, respectively. The median PFS in 31 patients received treatment of fludarabine based chemotherapy was 48 months (95%CI: 39 - 57 months), among them 27 cases (87.1%) achieved CR + PR. While PFS was 14 months (95%CI: 10 - 18 months, P < 0.001) in 9 patients received other treatment regimen, out of them only 3 cases (33.3%) achieved CR + PR. Patients with normal level of serum β2-microglobulin at diagnosis showed significantly higher overall survival (78%, 95%CI: 69% - 87%) in 36 months than those with abnormal level of serum β2-microglobulin (47%, 95%CI: 35% - 59%, P = 0.004). Significant difference in the rate of CR + PR was noted in the Zap70 positive group (50%) and in negative group (88.5%, P = 0.006). All of 8 patients with IgVH mutation displayed CR after treatment, while 4 cases (66.7%) archived CR among 6 patients without IgVH mutation. It is concluded that CLL is characterized by high heterogeneity in both clinical features and molecular markers, which are associated with prediction of outcomes for patients. The treatment with fludarabine-based chemotherapy results in a major benefit and long survival for patients with CLL.
ADP-ribosyl Cyclase 1 ; metabolism ; Adult ; Aged ; Aged, 80 and over ; Female ; Flow Cytometry ; Humans ; Immunoglobulin Variable Region ; genetics ; Leukemia, Lymphocytic, Chronic, B-Cell ; genetics ; metabolism ; Male ; Middle Aged ; Mutation ; Retrospective Studies ; ZAP-70 Protein-Tyrosine Kinase ; metabolism

Activation-induced cytidine deaminase (AID) is required for the generation of antibody diversity through initiating both somatic hypermutation (SHM) and class switch recombination. A few research groups have successfully used the feature of AID for generating mutant libraries in directed evolution of target proteins in B cells in vitro. B cells, cultured in suspension, are not convenient for transfection and cloning. In this study, we established an AID-based mutant accumulation and sorting system in adherent human cells. Mouse AID gene was first transfected into the human non-small cell lung carcinoma H1299 cells, and a stable cell clone (H1299-AID) was selected. Afterwards, anti-hTNF-α scFv (ATscFv) was transfected into H1299-AID cells and ATscFv was displayed on the surface of H1299-AID cells. By 4-round amplification/flow cytometric sorting for cells with the highest affinities to hTNF-alpha, two ATscFv mutant gene clones were isolated. Compared with the wild type ATscFv, the two mutants were much more efficient in neutralizing cytotoxicity of hTNF-alpha. The results indicate that directed evolution by somatic hypermutation can be carried out in adherent non-B cells, which makes directed evolution in mammalian cells easier and more efficient.
Animals ; Antibody Affinity ; Cells, Cultured ; Cytidine Deaminase ; genetics ; metabolism ; HEK293 Cells ; Humans ; Immunoglobulin Variable Region ; genetics ; immunology ; Mice ; Mutation ; Single-Chain Antibodies ; chemistry ; genetics ; immunology ; Somatic Hypermutation, Immunoglobulin ; genetics ; immunology ; Tumor Necrosis Factor-alpha ; immunology

In the application of therapeutic antibodies, large molecular weight of antibodies is always a problem that prevents them from penetrating into tissues or binding to antigenic determinants. To overcome this problem, we investigated the function of the heavy chain variable domain of a monoclonal anti-VEGF human IgM antibody derived from the Five-Feature Translocus Mice. We cloned the cDNA of the heavy chain variable domain, which was then inserted into pET28a vector and expressed in Escherichia coli. After purification and renaturation of the denatured recombinant protein, we obtained a 16 kDa antibody fragment, which is named as rhVVH. By immunoassaying its VEGF-binding capability in vitro, we proved that rhVVH retains this activity as the complete IgM. Importantly, rhVVH is shown to inhibit the HUVEC cell proliferation in a concentration-dependent manner. Our results indicate that the single heavy chain variable domain might inherit part of the biological function of the complete IgM antibody, which provided a valuable potential in further research on antibody miniaturisation.
Amino Acid Sequence ; Animals ; Base Sequence ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Humans ; Immunoglobulin Heavy Chains ; biosynthesis ; genetics ; Immunoglobulin Variable Region ; biosynthesis ; genetics ; Mice ; Molecular Sequence Data ; Recombinant Proteins ; biosynthesis ; genetics ; Single-Chain Antibodies ; biosynthesis ; genetics ; Vascular Endothelial Growth Factor A ; genetics ; metabolism

Chronic lymphocytic leukemia (CLL) remains the most common adult leukemia. The recent progress on research of molecular and cellular genetics of CLL promotes the development of the diagnosis, treatment and prognosis for CLL patients. IGVH gene mutation status is the most important prognostic marker for CLL patients. Zeta-chain-associated protein kinase (ZAP-70) can be used as a surrogate marker for IGVH mutation status. CD38 is a type II transmembrane glycoprotein promoting B cell activation and proliferation, which can improve the survival of CLL cells and enhance their proliferation, so it also can be used as an independent prognostic indicator for CLL. Chromosome aberrations are found in more than 80% of CLL cases. The most frequent abnormalities are losses of chromosomal material, with deletions in band 13q14 being the most common. The most common gains of chromosomal material are trisomies 12q. Human leukocyte antigen G (HLA-G) is a non-classical HLA-I gene. Increased expression of HLA-G leads to the malignant progression of CLL, significantly shortens survival, indicating HLA-G might serve as a prognostic marker in CLL. Toll-like receptors (TLA) are important component of natural immunity. The combination of TLR agonists and release chemotherapy, monoclonal antibodies and tumor vaccines would bring a breakthrough for the treatment of CLL.
ADP-ribosyl Cyclase 1 ; metabolism ; Chromosome Aberrations ; HLA Antigens ; metabolism ; HLA-G Antigens ; Histocompatibility Antigens Class I ; metabolism ; Humans ; Immunoglobulin Heavy Chains ; genetics ; Immunoglobulin Variable Region ; genetics ; Leukemia, Lymphocytic, Chronic, B-Cell ; genetics ; immunology ; metabolism ; Mutation ; Prognosis ; Sequence Deletion ; Toll-Like Receptors ; metabolism ; ZAP-70 Protein-Tyrosine Kinase ; metabolism

The aim of this study is to construct a bifunctional fusion protein, which can conjugate both human red blood cells and antibodies against classical swine fever virus (CSFV). We respectively amplified 2E8ScFv and mE2 genes from different recombinant vectors, in which 2E8ScFv gene is the single chain Fv gene against H antigen of human red blood cells, whereas mE2 gene is the main antigen coding region gene of CSFV E2 protein. We used overlap extension PCR to obtain an artificial fusion gene segment 2E8mE2 containing genes of Both 2E8ScFv and mE2, then ligated into the expression vector pET-DsbA and expressed in Escherichia coli BL21(DE3) PlysS host cells, after induced with IPTG the target fusion protein was successfully expressed and identified in inclusion bodies by SDS-PAGE and Western blotting. We purified the fusion protein and renatured it from inclusion bodies to obtain a native state of well biological activity. The Erythrocyte agglutination test results indicated that the fusion protein can conjugate both human red blood cells and antibodies of CSFV.
Erythrocytes ; immunology ; Escherichia coli ; genetics ; metabolism ; Humans ; Immunoglobulin Fragments ; biosynthesis ; genetics ; immunology ; Immunoglobulin Variable Region ; biosynthesis ; genetics ; immunology ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Single-Chain Antibodies ; biosynthesis ; genetics ; Viral Envelope Proteins ; biosynthesis ; genetics

OBJECTIVETo observe the function of gamma delta T lymphocytes and the polymorphism of T cell receptor V delta chain in the lungs of asthmatic patients and explore the role of gamma delta T cells in airway inflammation.

METHODSBronchoalveolar lavage fluid BALF was obtained from 7 asthmatic patients and 7 healthy control individuals. The percentage of gamma delta T cell in BALF was measured by flow cytometry. The gamma delta T cell in BALF was purified by magnetic labeled beads. Proliferous activity was examined by MTT assay. Cytokines secreted by gamma delta T cells in medium was assessed by enzyme-linked immunosorbent assay. Polymorphism of T cell receptor V delta chain was detected by RT-PCR and gene scan analysis.

RESULTSThe proportion of gamma delta T cell in the BALF of asthmatic patients [(6.39+/-0.71)%] was significantly higher than that in control subjects [(2.62+/-0.37)%] (P<0.01). The proportion of macrophage in the BALF of asthmatic patients [(81+/-4)] was significantly lower than that in control subjects [(86+/-2)] (P<0.05). The proliferation rate of asthmatic patients [(284.2+/-43.6)%] was significantly higher than that of control subjects [(217.5+/-59.5)%] (P<0.05). Interleukin-4 secreted by gamma delta T cells of asthmatic patients [(18.9+/-3.1) pg/ml)] significantly increased when compared with the control subjects [(14.1+/-3.0) pg/ml] (P<0.05). The polymorphism of T cell receptor V delta chain was not significantly different between these two groups.

CONCLUSIONSThe increase of gamma delta T cells in the lung of asthmatic patients further exacerbates Th1/Th2 disturbance and airway inflammation. Antigen recognition by gamma delta T cells is non-specific.

Adult ; Asthma ; genetics ; immunology ; Bronchoalveolar Lavage Fluid ; cytology ; Case-Control Studies ; Cell Proliferation ; Cytokines ; metabolism ; Female ; Genes, T-Cell Receptor delta ; genetics ; Genes, T-Cell Receptor gamma ; genetics ; Humans ; Immunoglobulin Variable Region ; genetics ; Lung ; immunology ; Male ; Middle Aged ; Polymorphism, Genetic ; T-Lymphocyte Subsets ; immunology ; metabolism ; Th1-Th2 Balance