ABSTRACT
We prepared single-chain immunoglobulin Fv fragments (scFv) SLH10 specific for the HepG2 cell line after biopanning from a large human-naive phage display library (Griffin. 1 Library). The three-dimensional (3D) structure of SLH10 was modelled by the Insight II molecule simulation software.The structure was refined using the molecular dynamics method.The structures with the least steric clashes and lowest energy were determined finally. The optimized structures of heavy (VH) and light (VL) variable chains of SLH10 scFv were obtained.Then SLH10 bivalent single-chain Fv (BsFv) was constructed that would be suitable for high-affinity targeting.SLH10 BsFv was generated by linking scFvs together and identified by sequencing. Its expression products were confirmed by western blot analysis.The relative molecular masses of scFv and BsFv were approximately 30 kDa and 60 kDa,respectively. Flow cytometry revealed that SLH10 BsFv bound the selected cell lines with greater signal intensity than the parental scFv. The improved antigen binding of SLH10 BsFv may be useful for immunodiagnostics or targeted gene therapy for liver cancer.
Subject(s)
Antibodies , Cell Line , Hepatocytes/immunology , Humans , Immunoglobulin Fragments/chemistry , Immunoglobulin Heavy Chains , Immunoglobulin Light Chains , Models, Biological , Models, Molecular , Peptide Library , Protein Binding , Protein Conformation , Sequence Homology, Amino AcidABSTRACT
The effectS of survivin antisense RNA on proliferation of leukemia cell line HL-60 and taxol.induced chemotherapy was explorcd.A cDNA fragment of survivin obtained by RT-PCR was inserted into a plamid vector named pcDNA3 in the reverse direction.The vector encoding antisense RNA of survivin was confirmed by restriction enzyme digestion and DNA sequencing.The recombi-nant plasmid was delivered into HL-60 cells by electroporation.Growth curves were plotted based on cell counting.Trypan blue dye exclusion assay and MTT assay were carried out after the cells were incubated with taxol.DNA gel electrophoresis and nuclear staining were performed for cell apoptosis assay.The correct construction of the recombinant plasmid has been identificd bv restriction enzy.me digestion and DNA sequencing.A stable down.regulation has been achieved in HL-60 SVVas cells after G418 selection.Compared tO HL-60 cells.the proliferation of HL-60 SVVaS cells was signifi.cantly inhibited(P＜0.05).Cytotoxicity assays indicated that IC50 of HL-60 SVVas for taxol was rela-tively lower than controls(P＜0.01).Apoptosis assays revealed that taxol-induced apoptosis was de-tected in HL-60 sVVas cells incubated with 50 ng/ml taxol for 12 h,while in HL-60 cells incubated with 100 ng/ml taxol for 72 h.It was suggested that Survivin antisense RNA could inhibit the prolif-eration of HL-60 cells and enhance taxol-induced apoptosis in HL-60 cells.which may lay an ex-perimental foundation for further research on gene therapy in leukemia.
ABSTRACT
Summary: The purpose of this study was to construct expression vectors of idiotype (Id) Smlg in patients with B-chronic lymphocytic leukemia and to express them in E.coli to obtain recombinant Id,and to investigate the effect of the protein on the proliferation and secretion of IL-2 and IFN-γ of stimulated peripheral blood mononuclear cells (PBMC) in vitro. Light chain gene and Fd fragment of heavy chain gene were inserted into fd-tet-DOG2 vector to construct fd-tet-DOG2-Fab. Fab gene was further cloned into expression vector pHEN2 to construct the soluble expression vector pHEN2-Fab. After induction by IPTG, Fab protein was purified by Ni-NTA-chromatography. MTT was used to determine the effects of purified protein on the proliferation of stimulated PBMC in vitro and the concentrations of IL-2 and IFN-γ in the culture supernatants were detected by ELISA. The results showed that recombinant pHEN2-Fab expression vector was constructed successfully. Fab protein was expressed in positive clone after induced by 1PTG and two specific bands at 24-25 kD position were observed by SDS-PAGE electrophoresis. Proliferation of PBMC could be induced by purified Fab and the concentrations of IL-2 and IFN-γ, in culture supernatants were increased significantly after induction. It was suggested that the expression vector of SmIg Fab fragment was constructed successfully, and expressed and secreted from E. Coli. The Fab protein could induce proliferation of PBMC and promote secretion of IL-2 and IFN-γ.
ABSTRACT
To obtain single chain variable fragment (scFv) and bivalent single chain variable fragment (bsFv) against transferrin receptor, up-stream and down-stream primers were designed according to the complemenary sequences of FR1 region of variable heavy (VH) and FR4 of variable light (VL), respectively, which contained inter-linker G4S and the restriction endonuclease Sill, AscI and NotI. Two pieces of scFv fragments were first amplified through PCR and then inserted into plasmid pAB 1, which could express scFv protein once induced by IPTG in the host bacteria. To express scFv and bsFv, E. coli TG1 was cultured in LB broth and was induced by IPTG The restriction enzyme digestion map and DNA sequencing demonstrated that scFv and bsFv genes were successfully inserted into the expression plasmid. SDS-PAGE and Western blotting revealed the protein band at 35kD and 60kD, which were consistent with the molecular weight of scFv and bsFv respectively.Flow cytometry showed that scFv and bsFv harbored the specific binding activity with TfR expressed in various tumor cells, and the avidity of bsFv was higher than that of the parent scFv.