[Phage antibody library technology in tumor therapy: a review].

Tumor is a serious threat to human health. At present, surgical resection, chemoradiotherapy, targeted therapy and immunotherapy are the main therapeutic strategies. Monoclonal antibody has gradually become an indispensable drug type in the clinical treatment of cancer due to its high efficiency and low toxicity. Phage antibody library technology (PALT) is a novel monoclonal antibody preparation technique. The recombinant immunoglobulin variable region of heavy chain (VH)/variable region of light chain (VL) gene is integrated into the phage vector, and the antibody is expressed on the phage surface in the form of fusion protein to obtain a diverse antibody library. Through the process of adsorption-elution-amplification, the antibody library can be screened to obtain the antibody molecule with specific binding antigen as well as its gene sequence. PALT has the advantages of short antibody production cycle, strong plasticity of antibody structure, large antibody yield, high diversity and direct production of humanized antibodies. It has been used in screening tumor markers and preparation of antibody drugs for breast cancer, gastric cancer, lung cancer and liver cancer. This article reviews the recent progress and the application of PALT in tumor therapy.

Construction of a Hantaan Virus Phage Antibody Library and Screening for Potential Neutralizing Activity.

China is one of the main epidemic areas for hemorrhagic fever with renal syndrome (HFRS). Currently, there is no human antibody specific to Hantaan virus (HTNV) for the emergency prevention and treatment of HFRS. To prepare human antibodies with neutralizing activity, we established an anti-HTNV phage antibody library using phage display technology by transforming peripheral blood mononuclear cells (PBMCs) of patients with HFRS into B lymphoblastoid cell lines (BLCLs) and extracting cDNA from BLCLs that secreted neutralizing antibodies. Based on the phage antibody library, we screened HTNV-specific Fab antibodies with neutralizing activities. Our study provides a potential way forward for the emergency prevention of HTNV and specific treatment of HFRS.

Phage Display Technology as a Powerful Platform for Antibody Drug Discovery.

Antibody drugs with a high affinity and specificity are effective and safe for intractable diseases, such as cancers and autoimmune diseases. Furthermore, they have played a central role in drug discovery, currently accounting for eight of the top 20 pharmaceutical products worldwide by sales. Forty years ago, clinical trials on antibody drugs that were thought to be a magic bullet failed, partly due to the immunogenicity of monoclonal antibodies produced in mice. The recent breakthrough in antibody drugs is largely because of the contribution of phage display technology. Here, we reviewed the importance of phage display technology as a powerful platform for antibody drug discovery from various perspectives, such as the development of human monoclonal antibodies, affinity enhancement of monoclonal antibodies, and the identification of therapeutic targets for antibody drugs.

High sensitive single chain variable fragment screening from a microcystin-LR immunized mouse phage antibody library and its application in immunoassay.

Microcystin-LR (MC-LR) is one of common high-toxic biotoxins produced by cyanobacteria in waterbody. A high sensitive and convenient detection method is necessary for monitoring for MC-LR. To establish a high sensitive indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) based on single chain variable fragment (scFv) for detecting MC-LR, 16 positive anti-MC-LR phage scFv particles were screened out from a MC-LR-immunized mouse phage scFv library, which was successfully constructed with the capacity of 8.67 × 107 CFU/mL. The most positive anti-MC-LR phage scFv (MscFv7) was successfully expressed in Escherichia coli (E.coli) HB2151. The molecular weight (M.W.) of expressed protein was about 30 kDa, and the concentration of purified protein was 512.6 µg/mL analyzed by SDS-PAGE and protein quantitative respectively. The IC-ELISA based on MscFv7-scFv for MC-LR shows a half-maximum inhibition (IC50) of 0.471 µg/L and a limit of detection (LOD) of 0.044 µg/L, which is below the maximum residue limit standard (MRLs) of 1.0 µg/L in drinking water. The MscFv7-scFv has a strong cross-recognition for MC-RR and MC-YR with cross-reactivity (CRs) of 93.1% and 85.9%, respectively, but weak for MC-LW with that of 9.7%, even non-recognition for MC-WR, MC-LF and MC-LY. The recovery rates of IC-ELISA to detect MC-LR spiked in different cleanliness of water samples were 81.2-106.3% with CVs of 2.62-10.22% at intra-assay and inter-assay. The results showed that we obtained a high sensitive anti-MC-LR scFv, and the established IC-ELISA based on MscFv7-scFv should be promising for ultrasensitive monitoring MC-LR, MC-RR and MC-YR in water samples.

Preparation of single-chain antibody against VP3 protein of duck hepatitis virus type 1 by phage display technology.

To construct phage antibody library for VP3 protein of duck hepatitis virus type 1(DHAV-1) and pan the specific single-chain variable fragment antibody (scFv), total RNA was extracted from the protein VP3- immunized mice spleen., vp3 gene encoding VP3 protein was amplified from the genome of DHAV-1 by RT-PCR method for the following recombinant pET-VP3 construction, immunogenic VP3 expression and purification, and combined with SOE-PCR method to complete the assembly of scFv. The scFv gene was cloned into pCANTAB5E vector for phage antibody library construction. Finally, the library for anti-VP3 scFv was screened by four rounds of adsorption-elution-enrichment with the purified VP3 protein. The characters of binding ability, specificity and neutralization of soluble antibodies expressed were evaluated by ELISA. The results showed 7 VP3-specific scFvs have been screened and identified with high both sensitivity and specificity for binding DHAV-1. To our knowledge, this is the first report for VP3-specific scFv of DHAV-1 and potentially promising application used in prevention and treatment of duck viral hepatitis.

Combine Phage Antibody Display Library Selection on Patient Tissue Specimens with Laser Capture Microdissection to Identify Novel Human Antibodies Targeting Clinically Relevant Tumor Antigens.

A functional approach to generate tumor-targeting human monoclonal antibodies is through selection of phage antibody display libraries directly on tumor cells. Although technically convenient, the use of cancer cell lines for the selection has limitations as those cell lines often undergo genetic and epigenetic changes during prolonged in vitro culture and alter their cell surface antigen expression profile. The key is to develop a technology that allows selection of phage antibody display libraries on tumor cells in situ residing in their natural tissue microenvironment. Laser capture microdissection (LCM) permits the precise procurement of tumor cells from human cancer patient tissue sections. Here, we describe a LCM-based method for selecting phage antibodies against tumor cells in situ using both fresh frozen and paraffin-embedded tissues. To restrict the selection to antibodies that bind internalizing epitopes, the method utilizes a polyclonal phage population pre-enriched for internalizing phage antibodies. The ability to recognize tumor cells in situ residing in their natural tissue microenvironment and to deliver payload intracellularly makes these LCM-selected antibodies attractive candidates for the development of targeted cancer therapeutics.

Prokaryotic expression of MLAA-34 and generation of a novel human ScFv against MLAA-34 by phage display technology.

MLAA-34 is a newly identified monocytic leukemia-associated antigen that is overexpressed in acute monocytic leukemia specifically, thus providing a novel target for the therapy of acute monocytic leukemia. In this study, we first expressed MLAA-34 protein in Escherichia coli (E.coli) BL21 (DE3) cells and purified it by nickel ion affinity chromatography with high purity (>90%). Then, MLAA-34 was used as antigen for biopanning anti-MLAA-34 single chain antibody fragment (ScFv) from a fully human ScFv library, and a high affinity ScFv named MA1 was selected by phage-ELISA. Finally, after expression of MA1, we found that MA1 can specifically bind with U937 MLAA-34 positive cells, and the binding affinity of MA1 was at the nanomolar level. Furthermore, inhibition of U937 cell proliferation indicated that the novel antibody MA1 has the potential to be used as a therapeutic agent for acute monocytic leukemia.

Selection and identification of human monoantibody TRAb Fab fragment / 天津医药

Objective To select and express a human thyrotrophin receptor antibody (TRAb) Fab fragment from phage antibody library constructed with phage display technology. Methods With immobilized antigen, the reconstructed humanized TRAb Fab library was enriched by five rounds panning (adsorption-elution-amplification). The TSAb Fab and TBAb Fab fragment were selected by coated fusion proteins of hTSHRn and hTSHRc. The positive clones were identified and selected by Phage-ELISA. TRAb positive clones were identified by PCR and double restriction enzyme digestion. The soluble TRAb (TSAb, TBAb) Fab fragments were expressed. TRAb (TSAb, TBAb) Fab fragments were identified by Western blotting assay. The DNA fragment was sequenced from the positive clones. Results Following five rounds of biopanning, TRAb (TSAb,TBAb) Fab phage antibody was screened. The enrichment effect reached to 77 times and 94 times. The soluble TRAb (TSAb,TBAb) Fab antibodies were expressed from positive clones and identified by phage ELISA. Western blotting analysis showed that the phage displaying Fab had significant binding activity with antigens. These sequence analysis showed that all of the heavy chain Fd gene and light chain gene were derived from human immunoglobulin variable region. The light chain variable region of the monoclonal 48 was homologous to the immunoglobulin light chain Vλ homology of 94.4%, and the heavy chain variable region of the monoclonal 48 was homologous to the immunoglobulin heavy Fd chain VH4 homology of 88.9%. The light chain variable region of the monoclonal 56 was homologous to the immunoglobulin light chain Vλ homology of 95.6%, and the heavy chain variable region of the monoclonal 56 was homologous to the immunoglobulin heavy Fd chain VH3 homology of 84.6%. Conclusion We have successfully selected TRAb (TSAb, TBAb) Fab fragment from a human phage display immune antibody library.

Phage display library selection of a hypoxia-binding scFv antibody for liver cancer metabolic marker discovery.

Hypoxia, which is frequently observed in liver cancer and metastasis, influences tumor progression and resistance to therapy. Although hypoxia-associated biomarkers are of use in other cancers, none is recognized as a surrogate for hypoxia in liver cancer. In this study, we generated seven unique human single-chain Fv (scFv) antibodies (Abs) specific to hypoxic liver cancer cells, using normoxia-depleted vs hypoxia-selected phage library panning technology. By developing the scFv immunoprecipitation-based mass spectrometry method, the antigen that bound with one of the Abs (H103) was identified as the M2 splice isoform of pyruvate kinase (PKM2), an enzyme that is a key regulator of aerobic glycolysis in cancer cells. Increased expression of PKM2 was induced by hypoxia in liver cancer cell lines. Immunohistochemical (IHC) staining showed that PKM2 was highly expressed in moderately and well differentiated hepatocellular carcinoma (HCC) tissues with a hypovascular staining pattern. High expression of PKM2 was also localized in the perinecrotic area of intrahepatic cholangiocarcinoma (ICC) tissues. The percentage of the HCC or ICC tumor expressing PKM2 was significantly higher with more tumor necrosis, low microvessel density, and advanced stage. Moreover, the H103 scFv Ab was efficiently internalized into hypoxic liver cancer cells and could have potential for targeted drug delivery. CONCLUSION: our study, for the first time, developed hypoxia-specific scFv Ab H103 to liver cancer cells, and revealed that PKM2 is a promising biomarker for hypoxia in HCC and ICC tissues. These allow further exploration of this valuable Ab and PKM2 antigen for hypoxia targeting in liver cancer.

Phage antibody display libraries: a powerful antibody discovery platform for immunotherapy.

Phage display technology (PDT), a combinatorial screening approach, provides a molecular diversity tool for creating libraries of peptides/proteins and discovery of new recombinant therapeutics. Expression of proteins such as monoclonal antibodies (mAbs) on the surface of filamentous phage can permit the selection of high affinity and specificity therapeutic mAbs against virtually any target antigen. Using a number of diverse selection platforms (e.g. solid phase, solution phase, whole cell and in vivo biopannings), phage antibody libraries (PALs) from the start point provides great potential for the isolation of functional mAb fragments with diagnostic and/or therapeutic purposes. Given the pivotal role of PDT in the discovery of novel therapeutic/diagnostic mAbs, in the current review, we provide an overview on PALs and discuss their impact in the advancement of engineered mAbs.

Optimized selection of anti-tumor recombinant antibodies from phage libraries on intact cells.

Generation of human recombinant antibody libraries displayed on the surface of the filamentous phage and selection of specific antibodies against desirable targets allows production of fully human antibodies usable for repeated administration in humans. Various lymphoid tissues from immunized donors, such as lymph nodes or peripheral blood lymphocytes from individuals with tumor or lymphocytes infiltrating tumor masses may serve as a source of specific anti-tumor antibody repertoire for generation of tumor-focused phage display libraries. In the case of lack of tumor-associated antigens in the purified form, high affinity anti-tumor antibodies can be isolated through library panning on whole cells expressing these antigens. However, affinity selection against cell surface specific antigens within highly heterogeneous population of molecules is not a very efficient process that often results in the selection of unspecific antibodies or antibodies against intracellular antigens that are generally useless for targeted immunotherapy. In this work, we developed a new cell-based antibody selection protocol that, by eliminating the contamination of dead cells from the cell suspension, dramatically improves the selection frequency of anti-tumor antibodies recognizing cell surface antigens.

Screening and primary identification of anti-CCR7 scFv from large phage library / 中国药理学通报

Aim To screen and identify anti-CCR7 single chain fragments variable(scFv)from lager phage library and to detect the scFv efficiency.Methods The insert ratio of ScFv antibodies library was identified by PCR.The products digested by Sfi I/Not I double enzyme.Panning against breast cancer cell and CCR7 were performed four and three rounds respectively.Positive clones were transformed to E.coli HB2151, and their dissolvability was assayed.The soluble scFv was purified by affinity chromatography, and its relative molecular mass was determined by Western blot.The ELISA assay was used to identify the immunocompetence of the antibody.Immunocytochemical staining and radioimmunoimaging were employed to determine the affinities of scFv binding with CCR7 in cell line and in nude mice.Results The insert ratio of ScFv gene was 90%(18/20), enzyme digest reaction showed the aim products on 1% agarose gel.ScFvs were obviously enriched after 7 round panning.Western blot result showed soluble scFv's molecular mass was about 34 KD.ELISA analysis showed dissolved antibody had high immunocompetence to MDA-MB-435 s cells.Immunocytochemical staining and radioimmunoimaging indicated that ScFvs were bound efficiently to MDA-MB-435 s cells which expressed CCR7.Conclusions ScFvs against CCR7 are successfully acquired by screening the phage antibody library.The soluble ScFvs have high affinity and specifical binding to human breast cancer cells.

Selection and preliminary identification of human Fab fragement antibody against amylin from phage antibody library / 中国免疫学杂志

Objective:To obtain antibodies against amylin from a 'naive' human Fab fragment antibody phage diasplay library and to analyze the specificity of antigen binding activity.Methods:Panning and screening Fab antibody from the antibody library,the positive clones with well reactivity to amylin were selected after five times selection of 'adsorption-elution-enrichment'.Then the plasmid DNA which was extracted from the clones,was digested with Spe Ⅰ and Nhe Ⅰ to delete gⅢ (about 660 bp).The digested 47 000 bp DNA which was purified after separation of bands from agarose gel was ligated with T4-DNA ligase.The constructed expressing phagemids were transformed to the BL21(DE3)pLysS,soluble Fab was expressed in it by the induction of IPTG and its characteristics and specificity were determined by ELISA and Western blot.Results:Soluble Fab antibodies were expressed in E.coli.According with molecular weight of IgG Fab,protein band of about 47 kD was shown by SDS-PAGE.Western blot using the goat anti human IgG-HRP showed their binding activities.ELISA showed their specificity with amylin antigens and they did not react with bovine serum albumin.Conclusion:The high level expression and identification of the soluble human anti- amylin Fab fragment antibodies has been obtained successfully,which lays a solid foundation for further researching about the biological and pathological activities of amylin.

Construction of human naive phage antibody library and primary screening of the gab antibodies against gp96 / 中国综合临床

Objective To construct a naive human Fab fragment phage display library,from which the anti-gp96 antibodies may be panned by the gp96 purified from the tissue of urothelial carcinoma in the urinary bladder and provide a basis to new therapy for the malignant tumors.Methods Peripheral blood lymphocytes were isolated from 800 ml of blood,which was obtained from four healthy blood donors.The heavy chain Fd and light chain cDNA synthesized from the total RNA of lympbocytes were amplified by PCR with variable regions 5' and 3' primers of heavy and light chain, and the amplification products were ligated into the phagemid vector pComb3, then the ligated sample was transformed into competent E.coli XL1-Blue by electroperation.The transformed cells were infected with VCSM13 helper phage to yield recombinant phage antibody Fabs.The phagemids abstracted from amplified E.coli were cut with endonucleases such as Sac Ⅰ,Xba Ⅰ,Xho Ⅰ and Spe Ⅰ, and both the phage antibody Fabs and phage-raids abstracted from amplified E.coil were amplified by PCR to monitor the insertion of the genes of light chain or heavy chain Fd fragment.The gp96 purified from the urothelial carcinoma tissue of the bladder by affinity chromatog-raphy on eoncanavalin-A sephnrose and DEAE-sephnrose ion exchange chromatography were utilized as antigens to process three rounds of panning to the original Fab antibody library.Results The quantity of total RNA and cDNA were qualified.By combination of light chain and heavy chain genes, an antibody library containing 6.6×106 clones was obtained, and both the cutting of enzymes and PCR showed that there were the genes of light chain or heavy chain Fd fragment in the phagemids.The gp96 protein was obtained from urothelial carcinoma tissue in the urinary bladder.After having been panned by gp96, the original antibody library gained enrichment by 68 times.Conclusion Utilizing the technology of phage surface display, specific antibody can be gained from the human naive Fab phage display library,which can be used for immunological therapy for tumors.

Construction of gene library of human-originated single-chain variable fragment antibody associated with lung adenocarcinoma / 重庆医科大学学报

Objective:To construct human single-chain variable fragment (scFv) antibodies gene library associated with lung adenocarcinoma. Methods:Total RNA was extracted from the lymphatic tissue near the lung adenocarcinoma.VH and VL fragments were amplified with RT-PCR,the purified VH and VL fragments were used to produce scFv fragment by splicing-overlap-extension PCR. The scFv gene was cloned in pCANTAB-5E Phasmid,then transferred to Ecoli TG1.The insertion ratio of antibody gene was identified with RT-PCR,the positive enzyme-cutting products were identified with 1.5% agarose gel electrophoresis. Results:Clear 28 S and 18 S strips were found in total RNA;The size of VH is about 370 bp,VL is about 350 bp.The size of scFv is about 750 bp.After transformation into Ecoli TG1,2.2?107 CFU/?g ampicillin resistant bacteria colonies grow after overnight culture,and the positive insert ratio was 83.3%. Conclusion:Human single-chain variable fragment(scFv) antibodies gene associated with lung adenocarcinoma was constructed successfully. It could provide bases to further screen the antibody library construction.

Preparation and Identification of Anti-lactoferrin Single Chain Fv Antibody / 医学研究杂志

Objective To prepare a specific anti-lactoferrin single chain variable fragment(ScFv).Methods Anti-lactoferrin clones were screened from a 'naive' phage antibody library against the immobilized lactoferrin antigen,then the clones were transformed to the E.coli HB2151 to give soluble expression of antibody fragments.The culture supernatant containing ScFv was purified by immobilized metal affinity chromatography,and then determined with SDS-PAGE and ELISA.Results The results demonstrated that ScFvs were specific;they did not react with transferrin,lysozyme and bovine serum albumin in ELISA.The SDS-PAGE showed that the ScFvs had high purity through affinity chromatography and the molecular weight of them was about 32 kD.Conclusions The successful generation of the ScFvs against lactoferrin provides a basis for further study and clinical applications for dry eye and other ocular diseases.

Screening and identification of human anti-HIF-1? scFv of lung adenocarcinoma / 第三军医大学学报

Objective To screen human anti-hypoxia-inducible factor (HIF)-1? scFv of lung adenocarcinoma from large phage antibody library and identify the positive clones. Methods Panning of large phage antibody library against lung adenocarcinoma cell line A549 and HIF-1? was conducted respectively to select specific antibodies. E. coli HB2151 was infected to induce the expression of soluble scFv. The binding activity and specificity were tested by ELISA and immunocytochemical assay. The expression and relative molecular weight of the soluble scFv was detected by SDS-PAGE and Western blot analysis. Results After panning,the target scFv was enriched,and ELISA results showed that positive reactions to HIF-1? were detected in 5 of 10 random clones with a positive ratio of 50%. Immunocytochemical analysis showed the specific affinity of the antibodies to A549 cells. The soluble human anti-HIF-1? scFv fragments of lung adenocarcinoma were expressed in E. coli HB2151 and then confirmed by SDS-PAGE. The result of Western blotting showed that the relative molecular weight of the soluble scFv was about 30?103. The binding activity and specificity were confirmed by ELISA. Conclusion Human anti-HIF-1? scFv of lung adenocarcinoma is successfully obtained with large phage antibody library technique.

Construction of and screening for phage antibody library of human lung adenocarcinoma / 第三军医大学学报

Objective To construct human single-chain antibody gene library associated with lung adenocarcinoma, and screen lung adenocarcinoma cell A549-specific antibody. Methods The lymphatic tissue near lung adenocarcinoma was used to construct human single-chain antibody gene library. The specific antibody to lung adenocarcinoma cell A549 was screened from the antibody library. Positive clone bacteria were transformed to E. coli HB2151, and their dissolvability was observed. The soluble scFv was purified by affinity chromatography and its relative molecular mass was determined by SDS-PAGE and Western blotting. The specificity of scFv to human lung adenocarcinoma cells was identified with ELISA. Results The phage antibody library of 4.6?107 was constructed successfully. Single-chain antibody of human lung adenocarcinoma was enriched. The ratio of yield was increased gradually, 181 times higher after 5 rounds of panning than after the first round of panning. SDS-PAGE and Western blotting results showed soluble scFv' molecular mass was about 30 000. ELISA showed dissolved antibody had high specificity to bind A549 cells, not MDA-MB-435. Conclusion The single-chain antibody gene library of human lung adenocarcinoma was constructed successfully, and specific antibodies to lung adenocarcinoma were screened, providing the basis for single-chain antibody radionuclide imaging and treatment.

Screening and identification of phage antibodies against human lipopolysaccharide binding protein / 第三军医大学学报

Objective To obtain and identify monoclonal antibody against human lipopolysaccharide binding protein (LBP). Methods Three clones of antibody with better activity against human LBP were isolated after human antibody library screening by human LBP and 5 rounds of enrichment. After plasmid extracting, geneⅢ cutting, self-recircling and electric transforming, soluble Fab was expressed in E.coli. XL1-blue by the induction of IPTG and its characteristics were determined. Results The positive antibody was concentrated to 8.16?104 folds and the highest activity of the three clones was 106 . Conclusion Phage antibody against human LBP has been obtained successfully, which lays a solid foundation for researching its function.

Application of two bacteria colony-PCR methods in the screening of phage antibody library / 医学研究生学报

Objective:To value the application of two bacteria colony-PCR methods in the screening of phage antibody library. Methods:Five positive monoclonal bacterium were respectively suspended in either deionized water or 0.1% Triton X-100, and then boiled to be used as template in PCR. . The DNAs products of PCR were extracted and digested by two enzymes, and then determined by electrophoresis. Results:The inserted genes were detected in all the 5 clones after PCR and enzyme digestion .Conclusion:Bacteria colony-PCR can be used in screening positive recombinant colonies. The bacteria colony-PCR method with bacteria colonies suspended in deionized water is valuable in large scale positive recombinant bacterium screening.