The DNA coding for the fusion protein of thromobopoietin mimetic peptide (TMP) and human IgG1 Fc fragment was amplified from recombinant plasmid pET28a/TMPFc, inserted into pPICZalphaA and transformed into Pichia pastoris using electroporation. The recombinants of correct phenotype were identified after screening on MDH and MMH culture medium. The fusion gene was verified with PCR and western blot. MTT method was used to test the activity of TMPFc in promoting the growth of Ba/ F3-mpl cell. The TMPFc with a 64 000 molecular weight was a secretary protein in the system and its expression amounted to 65% of the total protein in the medium supernatant. The TMPFc showed a promotive effect on the growth of Ba/F3-mpl in vitro. A significant portion of the secretary protein existed as dimer, which provided material for studying the dimer in future.
Amino Acid Sequence ; Blotting, Western ; Humans ; Immunoglobulin Fc Fragments ; genetics ; Immunoglobulin G ; genetics ; Molecular Sequence Data ; Pichia ; genetics ; Plasmids ; Polymerase Chain Reaction ; Recombinant Fusion Proteins ; biosynthesis ; Thrombopoietin ; genetics

OBJECTIVETo isolate single chain antibody fragments (scFv) against cell surface molecules by pathfinder selection from an anti-KG1a cell scFv phage library.

METHODSThe anti-KG1a scFv library was enriched by KGla cell panning for three rounds, or unenriched, then processed for pathfinder selection respectively using anti-CD34 monoclonal antibody as pathfinder molecule. ScFv phage clones were randomly picked and identified by binding KG1a cells using immunofluorescein and flow cytometry. The KG1a+ clones were further identified by KG1a, HL60, U937, and CEM cell lines and ELISA. Their antigenic molecules on cell surface were digested by chymopapain and analyzed by flow cytometry. DNAs from ten positive clones were sequenced. The scFv clones with different primary structure were used to analyze the molecular weight of their antigens by Western blot.

RESULTSOne hundred and two KG1a+ scFv phage clones were isolated from 144 enriched and 96 unenriched scFv phage library respectively, among which 47 bound KG1a, HL60, U937, and CEM cells, 55 bound KG1a cells exclusively. None of 28 KG1a+, HL60-, U937-, and CEM- scFv clones bound to the CD34 antigen, as confirmed by ELISA, although most of their antigens were sensitive to chymopapain digestion. DNA sequences from ten positive clones showed that they were from four different clones. They bound antigens with different molecular weight.

CONCLUSIONSOne hundred and two scFv phage clones specific for hematopoietic stem and progenitor cells have been isolated from an anti-KG1a cell scFv phage library. The pathfinder selection has showed advantages to improve the screening efficacy of scFv phage clones against antigens, which present at very low densities on the cell surface.

Antibodies, Anti-Idiotypic ; immunology ; Antibodies, Monoclonal ; genetics ; Antibody Specificity ; Bacteriophages ; genetics ; Cloning, Molecular ; Hematopoietic Stem Cells ; immunology ; Humans ; Immunoglobulin Fc Fragments ; biosynthesis ; genetics ; immunology ; Immunoglobulin Fragments ; genetics ; immunology ; Immunoglobulin Variable Region ; genetics ; immunology ; Peptide Library ; Single-Chain Antibodies

To evaluate the efficiency of three in vitro refolding methods for a humanized single-chain Fv antibody against human CTLA4(CD152) expressed in E. coli, the denatured and purified inclusion bodies (IBS) were refolded by dilution, dialysis and in situ refolding via Immobilized Metal-Ion-Affinity Chromatography (IMAC), respectively. The concentration of refolded scFvs was examined by Bradford method. And the antigen binding activity of the refolded scFvs was analyzed by indirect cell-ELISA. The highest and lowest refolding yields could be obtained by dialysis and in situ refolding via IMAC, respectively. The binding activity of the refolded scFv by dialysis was 1.95-fold higher than that by dilution, 4.13-fold higher than that by in situ refolding via IMAC (GSH/GSSH excluded) and 3.63-fold higher than that by in situ refolding via IMAC (GSH/GSSH included), respectively. In conclusion, a high refolding yield and binding activity of scFv with natural conformation could be obtained by dialysis in the condition of 0. 15 mol/L sodium chloride, 50 mmol/L Tirs-HCl, pH 8. 0 buffer containing 3 mmol/L reduced glutathione and 1 mmol/L oxidized glutathione for 48 hours at 4 degrees C.
Antigens, CD ; biosynthesis ; genetics ; immunology ; Antigens, Differentiation ; biosynthesis ; genetics ; immunology ; CTLA-4 Antigen ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Humans ; Immunoglobulin Fc Fragments ; biosynthesis ; genetics ; immunology ; Immunoglobulin Variable Region ; biosynthesis ; genetics ; immunology ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; immunology

OBJECTIVETo construct a recombinant adenovirus vector carrying soluble extracellular region of tumor necrosis factor alpha receptor I-IgGFc (sTNFRI-IgGFc) and express the fusion protein in human bronchial epithelial HBE135-E6E7 cells.

METHODSsTNFRI-IgGFc fusion gene was subcloned into the adenovirus shuttle plasmid pDC316, which was co-transfected with helper plasmid pBHGloxPE1,3Cre into HEK293 cells. The recombinant adenovirus (Ad-sTNFRI-IgGFc) was generated by homologous recombination of the 2 plasmids in HEK293 cells. After identification with PCR, Ad-sTNFRI-IgGFc was amplified and purified, and its titer measured using TCID50 assay. The transcription and expression of sTNFRI-IgGFc gene in the transfected HBE135-E6E7 were detected by RT-PCR and immunohistochemistry.

RESULTSAd-sTNFRI-IgGFc was successfully constructed with a viral titer of 3 x 10(10) TCID50/ml. The expression of sTNFRI-IgGFc mRNA and protein was confirmed in the transfected HBE135-E6E7 cells.

CONCLUSIONThe constructed Ad-sTNFRI-IgGFc can effectively infect HBE135-E6E7 cells for efficient expression of sTNFRI-IgGFc protein, which antagonizes the cytolytic effect of TNFalpha in L929 cells, suggesting the potential of adenovirus expressing sTNFRI-IgGFc for local treatment of asthma.

Adenoviridae ; genetics ; Bronchi ; cytology ; Epithelial Cells ; cytology ; metabolism ; Genetic Vectors ; genetics ; Immunoglobulin Fc Fragments ; biosynthesis ; genetics ; Immunoglobulin G ; biosynthesis ; genetics ; Receptors, Tumor Necrosis Factor, Type I ; biosynthesis ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Transfection

ATR-Fc is a fusion protein consisting of extracellular domain of human anthrax toxin receptor (ATR) and a fragment (hinge, CH2, and CH3 domains) of the Fc of human IgG1. The aim of ATR-Fc expression is to get an antibody-like molecule binding to protective antigen (PA), a component of anthrax toxins, this fusion protein may compete with cell surface receptor for PA binding, and block the transport of lethal factor (LF) and edema factor (EF) into cells, thereby act as an antitoxin to prevent and treat anthrax infection. A DNA fragment encoding N-terminal amino acids 1-227 of ATR and human IgG1 Fc was inserted into the Hind III and Not I sites of pcDNA3.1 to generate the eukaryotic vector pcDNA3.1/ATR-Fc for expression of ATR-Fc fusion protein. Using lipofectine-mediated gene transfer technique, pcDNA3.1/ATR-Fc was transfected into CHO-K1 cells. After selected with G418, a recombinant CHO cell line, ATR-Fc-1D5, whose expression level was about 10 - 15 microg/(10(6) cells x d), was established. The recombinant protein expressed by the ATR-Fc-1D5 cells was purified with protein A chromatography. The experimental results demonstrated a direct and specific interaction between ATR-Fc and PA assessed by ELISA.
Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Gene Transfer Techniques ; Genetic Vectors ; Humans ; Immunoglobulin Fc Fragments ; biosynthesis ; genetics ; Immunoglobulin G ; biosynthesis ; genetics ; Neoplasm Proteins ; biosynthesis ; genetics ; Receptors, Cell Surface ; biosynthesis ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; immunology

We constructed the eukaryotic expression vector of human IL-35-IgG4 (Fc)-pOptiVEC-TOPO by gene recombination technique and expressed the fusion protein human IL-35-IgG4 (Fc) in CHO/DG44 cells. The two components of the newly discovered cytokine human IL-35, EBI3 and IL-12p35, were amplified by PCR from the cDNA library derived from the KG-I cells after LPS induction. The two PCR-amplified cDNA fragments of human IL-35 were linked by over-lapping PCR and then cloned into the IgG4 (Fc)-pOptiVEC-TOPO vector. The constructed plasmid with the recombinant cDNA IL-35-IgG4 (Fc) was verified by restriction enzyme digestion analysis, PCR and DNA sequencing. The verified plasmid with the recombinant cDNA was transfected into CHO/DG44 cells using Lipofectamine 2000. The success of the transfection was examined and confirmed by RT-PCR. After selection in alpha-MEM (-) medium, the IL-35-Ig G4 (Fc) positive CHO/DG44 clones were chosen and the media from these positive clones were collected to be used to purify the fusion protein. The positive CHO/DG44 clones were further cultured in increasing concentrations of MTX and the expression levels of the fusion protein IL-35-Ig G4 (Fc) were repetitively induced by MTX-induced gene amplification. The IL-35-IgG4 (Fc) fusion protein was purified from the media collected from the positive CHO/DG44 clones by protein G affinity chromatography and then identified by SDS-PAGE and Western blotting. The results showed that one protein band was found to match well with the predicted relative molecular mass of human IL-35-IgG4 (Fc) and this protein could specifically bind to anti-human IgG4 (Fc) monoclonal antibody. In conclusion, our study successfully established an IL-35-IgG4 (Fc) positive DG44 cell line which could stably express IL-35-IgG4 (Fc) fusion protein.
Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Gene Fusion ; genetics ; Genetic Vectors ; Humans ; Immunoglobulin Fc Fragments ; biosynthesis ; genetics ; Immunoglobulin G ; biosynthesis ; genetics ; Interleukins ; biosynthesis ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Transfection

Anti-angiogenesis mechanism plays a vital role in tumor targeting immunotherapy. Based on the amino acid sequence of an anti-VEGFR-2 scFv-Fc fusion antibody (AK404R-Fc), this article is aimed to generate an anti-VEGFR-2 human IgG1-like full length antibody (Mab-04). Firstly, the light chain (L-chain) and heavy chain (H-chain) were obtained by overlap PCR and then linked to eukaryotic expression vector pcDNA3.1, separately. The recombinant plasmids (pcDNA3.1-L-chain and pcDNA3.1-H-chain) were then co-transfected into CHO-k cells using liposome transient transfection. Subsequently, Mab-04 antibody was expressed and purified by Protein A affinity chromatography. Western blotting was applied to identify the expression of Mab-04 and its affinity was detected by ELISA assay. DNA sequencing revealed the successful construction of recombinant plasmids and Western blotting assay proved the successful expression of full-length antibody (1 microg x mL(-1)). Finally, ELISA assay illustrated that the binding of the antibody to its antigen was in a concentration-dependent manner (IC50: 50 nmol x L(-1)). These outcomes above indicated that Mab-04 was successfully expressed and assembled, which laid the foundation for further preparation and antineoplastic activity study.
Animals ; Antibodies, Monoclonal, Humanized ; analysis ; CHO Cells ; Cricetulus ; Genetic Vectors ; Immunoglobulin Fc Fragments ; genetics ; Immunoglobulin G ; genetics ; immunology ; Plasmids ; Recombinant Fusion Proteins ; analysis ; genetics ; Single-Chain Antibodies ; genetics ; Transfection ; Vascular Endothelial Growth Factor Receptor-2 ; genetics ; immunology

Both interleukin-1 and IgE are important in the pathogenic mechanism of the allergy asthma. cDNA of interleukin-1receptor antagonist (IL-1ra) and IgE were cloned and a prokaryotic expression vector IL-1ra-Fcepsilon/pBV220 was constructed. The vector was transformed into Escherichia coli BL21(DE3). The fusion protein was expressed successfully in the form of inclusion body. The recombination protein of IL-1ra-Fcepsilon was highly purified by chromatography of gel filtration and ion exchange, which was identifited by Western blotting. The cell assay showed that the activity of IL-1ra-Fcepsilon was as high as IL-1ra in vitro after refolding. The pharmacokenetic profile of IL-1ra-Fcepsilon and L-1ra was analyzed, and the half time of IL-1ra-Fcepsilon is 4.78 times than that of IL-1ra.
Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Gene Fusion ; Immunoglobulin E ; genetics ; metabolism ; Immunoglobulin Fc Fragments ; genetics ; metabolism ; Interleukin 1 Receptor Antagonist Protein ; genetics ; metabolism ; Recombinant Fusion Proteins ; genetics ; metabolism

We studied the aggregation of a recombinant engineering antibody (chA21). Anti-ErbB2 antibody chA21 was produced by fusing single-chain Fv (scFv) with human IgG1 Fc fragment, and it was proved to be a drug candidate for cancer therapy. We characterized the aggregation of chA21 by high performance sized-exclusive chromatography (HPSEC), dynamic light scattering (DLS), SDS-PAGE, indirect ELISA assay, and compared the influence of temperature and additive on the level of aggregation and binding activity. Conformation changes of different levels of aggregation were also analyzed via circular dichroism (CD). Finally, we analyzed which part of chA21 was involved in aggregation by cleaving it into scFv and Fc fragments. The results showed that chA21 could form aggregates in the storage solution. The aggregates interacted through non-covalent bonds and remained binding activity. Temperature and additive could slightly affect the level of aggregation and binding activity, while the conformations of chA21 were stable. Aggregation propensity of scFv fragment was almost same as chA21, indicating that scFv may be the major part to form the aggregates. The research on aggregation may be helpful to develop a suitable formulation for chA21 clinical application as well as provide direction for future antibody design and reconstruction.
Antibodies ; chemistry ; metabolism ; Humans ; Immunoglobulin Fc Fragments ; chemistry ; metabolism ; Immunoglobulin Variable Region ; chemistry ; metabolism ; Protein Conformation ; Protein Engineering ; methods ; Receptor Aggregation ; immunology ; Receptor, ErbB-2 ; chemistry ; immunology ; Recombinant Proteins ; biosynthesis ; chemistry ; genetics ; immunology

To prolong serum half-life of human Erythropoietin for better efficacy, a new form of recombinant human erythropoietin (rhEpo-L-Fc) was generated by fusion of a full length human erythropoietin gene and the Fc fragment of human IgG1 with flexible linker sequence. The fusion gene rhEPO-L-Fc was constructed by PCR, then inserted into expression vector pOptiVEC-TOPO, and expressed in Chinese Hamster Ovary cells deficient in the DHFR enzyme(CHO-dhfr-). The chimeric protein was purified by Protein A affinity chromatography, showed expected molecular weight and demonstrated a similar bioactivity compared to that of the native recombinant human erythropoietin (rhEPO) in an EPO-dependent cell-based assay. In vivo pharmacokinetic studies showed that the rhEPO-L-Fc had an elimination half-life of 27 h. In vivo efficacy studies showed that a single dose administration of rhEPO-L-Fc in rats increased the reticulocyte number in the peripheral blood significantly. These results demonstrated that the new engineered rhEPO-L-Fc may become alternative therapeutic approach to extend the half-time of rhEPO to treat anemia.
Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Erythropoietin ; chemistry ; genetics ; metabolism ; pharmacokinetics ; Female ; Humans ; Immunoglobulin Fc Fragments ; biosynthesis ; genetics ; Male ; Rats ; Rats, Sprague-Dawley ; Recombinant Fusion Proteins ; biosynthesis ; chemistry ; genetics ; pharmacokinetics ; Recombinant Proteins