• Journal of Microbiology and Biotechnology
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• v.9 no.3
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• pp.376-380
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• 1999

Constructs, encoding a single-chain variable fragment of a catalytic antibody 4f4f (scFv-4f4f) with glycosidase activity, were made by combining the coding sequences for the heavy and light chain variable domains with a sequence encoding a linker (GGGGS). Using three different plasmid systems, single-chain antibodies were expressed separately in Escherichia coli, demonstrating significant differences in the expression level and amounts in soluble form of the recombinant protein. The protein expression from pET3a-scFv-4f4f was up to 20% of the total soluble proteins and, more importantly, the proteins were mostly found in a soluble form. An SDS-PAGE analysis of the purified single-chain proteins, yielding higher than 5mg from a 1-1 culture, showed a single band corresponding to its molecular weight of 29,100. A preliminary study shows that the expressed scFv-4f4f is catalytically active. The catalytic parameters for the hydrolysis of p-nitrophenyl-$\beta$-D-glucopyranoside by scFv-4f4f are being investigated.

• BMB Reports
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• v.42 no.11
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• pp.731-736
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• 2009

The generation of functional recombinant antibodies from hybridomas is necessary for antibody engineering. However, this is not easily accomplished due to high levels of aberrant heavy and light chain mRNAs, which require a highly selective technology that has proven complicated and difficult to operate. Herein, we attempt to use an alkaline phosphate (AP)-fused form of single-chain variable fragment (scFv) for the simple identification of a hybridoma-derived, functional recombinant antibody. As a representative example, we cloned the scFv gene from a hybridoma-producing mouse IgG against branched-chain keto acid dehydrogenase complex-E2 (BCKD-E2) into an expression vector containing an in-frame phoA gene. Functional recombinant antibodies were easily identified by conventional enzyme-linked immunosorbent assay (ELISA) by employing scFv-AP fusion protein, which also readily serves as a valuable immuno-detective reagent.

• Journal of Microbiology and Biotechnology
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• v.27 no.5
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• pp.965-974
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• 2017

The single-chain variable fragment (scFv) against lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a promising molecule for its potential use in the diagnosis and immunotherapy of atherosclerosis. Producing this scFv in several milligram amounts could be the starting point for further engineering and application of the scFv. In this study, the abundant expression of the anti-LOX-1 scFv was attempted using Escherichia coli (E. coli) and Brevibacillus choshinensis (B. choshinensis). The scFv had limited soluble yield in E. coli, but it was efficiently secreted by B. choshinensis. The optimized fermentation was determined using the Plackett-Burman screening design and response surface methodology, under which the yield reached up to 1.5 g/l in a 5-L fermentor. Moreover, the properties of the scFvs obtained from the two expression systems were different. The antigen affinity, transition temperature, and particle diameter size were 1.01E-07 M, $55.2{\pm}0.3^{\circ}C$, and 9.388 nm for the scFv expressed by B. choshinensis, and 4.53E-07 M, $52.5{\pm}0.3^{\circ}C$, and 13.54 nm for the scFv expressed by E. coli. This study established an efficient scale-up production methodology for the anti-LOX-1 scFv, which will boost its use in LOX-1-based therapy.

• Proceedings of the Microbiological Society of Korea Conference
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• 2008.05a
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• pp.62-64
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• 2008

A major hurdle to the development of RNA interference as therapy for HIV infection is the delivery of siRNA to T lymphocytes which are difficult cells to transfect even in vitro. We have employed a single chain antibody to the pan T cell surface antigen CD7 was conjugated to an oligo-9-arginine peptide (scFvCD7-9R) for T cell-specific siRNA delivery in NOD/SCIDIL2${\gamma}$-/- mice reconstituted with human peripheral blood lymphocytes (Hu-PBL). Using a novel delivery, we first show that scFvCD7-9R efficiently delivered CD4 siRNA into human T cells in vitro. In vivo administration to Hu-PBL mice resulted in reduced levels of surface CD4 expression on T cells. Mice infected with HIV-1 and treated on a weekly basis with scFvCD7-9R-siRNA complexes targeting a combination of viral genes and the host coreceptor molecule CCR5 successfully maintained CD4/CD3 T cell ratios up to 4 weeks after infection in contrast to control mice that displayed a marked reduction in CD4 T cell numbers. p24 antigen levels were undetectable in 3 of the 4 protected mice. scFvCD7-9R/antiviral siRNA treatment also helped maintain CD4 T cell numbers with reduced plasma viral loads in Hu-PBL mice reconstituted with PBMC from donors seropositive for HIV, indicating that this method can contain viral replication even in established HIV infections. Our results show that scFvCD7-9R could be further developed as a potential therapeutic for HIV-1 infection.

• Journal of Microbiology
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• v.42 no.2
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• pp.126-132
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• 2004

A single chain variable fragment (scFv) specific towards B. pseudomallei exotoxin had previously been generated from an existing hybridoma cell line (6E6AF83B) and cloned into the phage display vector pComb3H. In this study, the scFv was subcloned into the pComb3X vector to facilitate the detection and purification of expressed antibodies. Detection was facilitated by the presence of a hemagglutinin (HA) tag, and purification was facilitated by the presence of a histidine tag. The culture was grown at 30$^{\circ}C$ until log phase was achieved and then induced with 1 mM IPTG in the absence of any additional carbon source. Induction was continued at 30$^{\circ}C$ for five h. The scFv was discerned by dual processes-direct enzyme-linked immunosorbent assays (ELISA), and Western blotting. When compared to E. coli strains ER2537 and HB2151, scFv expression was observed to be highest in the E. coli strain Topl0F'. The expressed scFv protein was purified via nickel-mediated affinity chromatography and results indicated that two proteins a 52 kDa protein, and a 30 kDa protein were co-purified. These antibodies, when blotted against immobilized exotoxin, exhibited significant specificity towards the exotoxin, com-pared to other B. pseudomallei antigens. Thus, these antibodies should serve as suitable reagents for future affinity purification of the exotoxin.

• IMMUNE NETWORK
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• v.12 no.1
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• pp.33-39
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• 2012

Background: Therapeutic approaches using monoclonal antibodies (mAbs) against complement regulatory proteins (CRPs:i.e.,CD46,CD55 and CD59) have been reported for adjuvant cancer therapy. In this study, we generated a recombinant 1E8 single-chain anti-CD59 antibody (scFv-Fc) and tested anti-cancer effect.by using complement dependent cytotoxicity (CDC). Methods: We isolated mRNA from 1E8 hybridoma cells and amplified the variable regions of the heavy chain (VH) and light chain (VL) genes using reversetranscriptase polymerase chain reaction (RT-PCR). Using a linker, the amplified sequences for the heavy and light chains were each connected to the sequence for a single polypeptide chain that was designed to be expressed. The VL and VH fragments were cloned into the pOptiVEC-TOPO vector that contained the human CH2-CH3 fragment. Then, 293T cells were transfected with the 1E8 single-chain Fv-Fc (scFv-Fc) constructs. CD59 expression was evaluated in the prostate cancer cell lines using flow cytometry. The enhancement of CDC effect by mouse 1E8 and 1E8 scFv-Fc were evaluated using a cytotoxicity assay. Results: The scFv-Fc constructs were expressed by the transfected 293T cells and secreted into the culture medium. The immunoreactivity of the secreted scFv-Fc construct was similar to that of the mouse 1E8 for CCRF-CEM cells. The molecular masses of 1E8 scFv-Fc were about 120 kDa and 55 kDa under reducing and non-reducing conditions, respectively. The DNA sequence of 1E8 scFv-Fc was obtained and presented. CD59 was highly expressed by the prostate cancer cell line. The recombinant 1E8 scFv-Fc mAb revealed significantly enhanced CDC effect similar with mouse 1E8 for prostate cancer cells. Conclusion: A 1E8 scFv-Fc construct for adjuvant cancer therapy was developed.

• Molecules and Cells
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• v.38 no.9
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• pp.773-780
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• 2015

3D8 single chain variable fragment (scFv) is a recombinant monoclonal antibody with nuclease activity that was originally isolated from autoimmune-prone MRL mice. In a previous study, we analyzed the nuclease activity of 3D8 scFv and determined that a HeLa cell line expressing 3D8 scFv conferred resistance to herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV). In this study, we demonstrate that 3D8 scFv could be delivered to target tissues and cells where it exerted a therapeutic effect against PRV. PRV was inoculated via intramuscular injection, and 3D8 scFv was injected intraperitoneally. The observed therapeutic effect of 3D8 scFv against PRV was also supported by results from quantitative reverse transcription polymerase chain reaction, southern hybridization, and immunohistochemical assays. Intraperitoneal injection of 5 and $10{\mu}g$ 3D8 scFv resulted in no detectable toxicity. The survival rate in C57BL/6 mice was 9% after intramuscular injection of 10 $LD_{50}$ PRV. In contrast, the 3D8 scFv-injected C57BL/6 mice showed survival rates of 57% ($5{\mu}g$) and 47% ($10{\mu}g$). The results indicate that 3D8 scFv could be utilized as an effective antiviral agent in several animal models.

• Journal of Microbiology and Biotechnology
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• v.17 no.10
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• pp.1670-1674
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• 2007

Duffy binding protein (DBP) plays a critical role in Plasmodium vivax invasion of human red blood cells. We previously reported a single-chain antibody fragment (scFv) that was specific to P. vivax DBP (PvDBP). However, the stabilization and the half-life of scFvs have not been studied. Here, we investigated the effect of PEGylated scFvs on their biological activity and stability in vitro. SDS-PAGE analysis showed that three clones (SFDBII-12, -58, and -92) were formed as monomers (about 70 kDa) with PEGylation. Clone SFDBII-58 gave the highest yield of PEGylated scFv. Binding analysis using BIAcore between DBP and scFv showed that both SFDBII-12 and -58 were decreased approximately by two folds at the level of binding affinity to DBP after PEGylation. However, the SFDBII-92 clone still showed a relatively high level of binding affinity ($K_D=1.02{\times}10^{-7}\;M$). Binding inhibition assay showed that PEGylated scFv was still able to competitively bind the PvDBP and playa critical role in inhibiting the interactions between PvDBP protein expressed on the surface of Cos-7 cells and Duffy receptor on the surface of erythrocytes. When both scFvs and their PEGylated counterparts were exposed to trypsin, scFv was completely degraded only after 24 h, whereas 35% of PEGylated scFvs remained intact, maintaining their stability against the proteolytic attack of trypsin until 72 h. Taken together, these results suggest that the PEGylated scFvs retain their stability against proteolytic enzymes in vivo, with no significant loss in their binding affinity to target antigen, DBP.

• Biotechnology and Bioprocess Engineering:BBE
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• v.4 no.1
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• pp.72-77
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• 1999

An antibody containing a genetically engineered lipid group at the N-termunus and a hexahistidinyl tag at the C-terminus (Lpp-scF-His6) was immobilized in an oriented manner on the surface of liposome. Liposomes, consisting of antibody and phosphatidyl-choline, have been prepared and imaged by AFM. For AFM visualization, the resulting liposomes were bound on the surface of mica by two different mechanisms. The histidine tags present in the antibody molecules of the immonuliposome were anchored to the NiCl2 treated mica surface. Alternatively, the immunoliposomes were immunochemically bound on antigen-coated mica surface. Both approaches yielded liposomes which were clearly imaged without damage by AFM in ambient condition.

• IMMUNE NETWORK
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• v.2 no.2
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• pp.91-95
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• 2002

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 $V_H$ 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 $3{\times}10^4$ 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 $V_H3$ 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.