Application of a single-chain fragment variable (scFv) antibody for the confirmatory diagnosis of hydatid disease in non-endemic areas

Background: Hydatid disease is a serious parasitic disease threatening public health. Because of its rarity in non-endemic coastal areas, determining the nature and origin of a chronic, enlarged liver cystic mass is challenging in these regions. Under these circumstances, physicians need a confirmatory diagnostic tool beyond immunological and radiological examinations. This study investigated a novel human single-chain fragment variable (scFv) antibody for the confirmative diagnosis of 18 atypical hydatid disease cases in non-endemic coastal areas. Results: A scFv antibody against cystic echinococcosis was produced by genetic engineering and then applied to the immunohistochemical diagnosis of 18 cases of cystic echinococcosis presented in non-endemic coastal areas. The diagnosis of these cases by ultrasound and serum-based examinations was inconclusive. The 750 bp scFv antibody gene was expressed in COS-7 cells, and the antibody localized in the cytoplasm. The scFv antibody can detect the germinal layer and protoscolices of actively growing cysts but not of the degenerating protoscolices and has a diagnostic efficiency higher than that of single serum or ultrasound testing (P b 0.05). The combined use of scFv antibodies with serology and ultrasound diagnostics results in a diagnostic efficiency comparable to that of surgery. The scFv antibody can be used as a confirmatory test for the diagnosis of hydatid disease in non-endemic areas, providing a beneficial supplementary diagnostic method that complements traditional immune testing and ultrasonic radiology and thus helping physicians to effectively differentiate hydatid disease.

Affinity maturation of human scFv anti-TSLP in vitro / 中国免疫学杂志

Objective:To single amino acid mutation of the full human scFvs against TSLP to enhance its affinity.Methods: The specific scFvs against TSLP was screened in our previous study and here the three-dimensional structures of TSLP and anti-TSLP scFvs were simulated by Discovery Studio system,then the molecular docking was made.The amino acids of binding epitope were randomly mutated and the mutated amino acids were selected which could remarkably improve the affinity of scFvs.The primers were designed based on the sequence of mutation amino acids and the scFv sequences were mutated by the overlapping extension PCR.The DNA of mutated scFvs was ligated with the expression vector pLZ16 and transformed into E.coli DH5αF′.Then the scFvs were expressed and the scFvs with improved affinity were selected by ELISA and BIAcore.Results: The five scFvs with single amino acid mutation were screened out by DS system,which could elevate the affinity of scFvs.The mutated anti-TSLP-scFvs were amplified by PCR,which size was about 1 000 bp.The mutated scFvs with correct sequence were expressed,and the mutated scFvs with improved affinity were detected by ELISA and BIAcore.The affinity of selected mutated scFv (M4) has been about 10 times higher than the scFv nonmutation.Conclusion: The affinity of anti-TSLP-scFv has been improved successfully.

Selection,soluble expression and identification of full human scFvs against IL-13 / 中国免疫学杂志

Objective:To select specific and neutralizing scFv against IL-13 and soluble expression and identification them.Methods:In our previous study the scFv library were constructed,and here the scFv library was enriched and the positive scFv were screened from the enriched scFv library for three round.The specific positive scFvs with better affinity were ligated with expression vector for expression and identification.Results:After three rounds of enrichment,30%of clones were positive.The two specific scFvs with better affinity and neutralization were selected from almost 500 clones and then ligated with expression vector LZ16 for soluble ex-pression.The expressed scFvs were identified by western blot and biomolecular interaction analysis.Conclusion: The specific scFvs against IL-13 with better affinity and neutralization had been selected successfully.

Selection and identification of full human scFv against TSLP / 中国免疫学杂志

Objective:Expression of protein TSLP and selection of full human anti-TSLP single chain Fv ( scFv).Methods:The cDNA of TSLP was amplified.The amplified target gene and the expression vector pET 101/D-TOPO were ligated , and then transformed into E.coli BL21.The protein was induced to expression by IPTG and purified and identified.The biotinylated TSLP protein was used as antigen to select of human TSLP scFv from a constructed human scFv library by phage display .Results: The size of amplified cDNA of TSLP was about 423 bp,and that of expressed protein was about 26 kD.Dot blot and Western blot results showed that the expressed protein was correct.The constructed human scFv library was enriched for three rounds using biotinylated TSLP as antigen by phage display.ELISA results showed that 35% scFvs had binding activity with TSLP.The scFvs with good binding activity were selected and identified by Western blot and sequencing.Conclusion: The full human scFvs against for TSLP were selected suc-cessfully.

Expression and functional analysis of fusion protein for the human anti-HBsAg scFv antibody fragment-consensus interferon / 中国免疫学杂志

Objective:Express a human anti-HBsAg single chain antibody fragment(scFv)-consensus interferon (cIFN) fusion protein by bacterial expression system and analyse the function of the fusion protein.Methods:Human anti-HBsAg single chain monoclonal antibody cDNA encoding the variable regions of immunoglobulin from PBMC of Hepatitis B patient. Consensus interferon gene was produced by overlap PCR.A plasmid for production of cIFN-scFV fusion protein was constructed, then the expression vector pRA cIFN-scFV transformed with the E.coli strain BL21(DE3). The gene product was analysed SDS-PAGE and Western blotting, then was solubilized by guanidine hydyochloride, refolded by conventional dilution method, and purified using metal-chelating chromatography. The immune and functional analysis of the resulting fusion protein have been studied by ELISA,FACS(Flow cytometry),MTS assay and hemaglutination inhibition test.Results:The authors isolated and characterized the human anti-HBsAg single chain antibody fragment(scFv)-consensus interferon (cIFN) fusion protein. The resulting human anti-HBsAg scFv-cIFN fusion protein was bound to react with HBsAg and cIFN, this react show that highly specific and bioactivity.Conclusion:A human anti-HBsAg single chain antibody fragment(scFv)-consensus interferon (cIFN) fusion protein was produced by bacterial expression system in this study. This genetically engineered human anti-HBsAg scFv-cIFN fusion protein promises to be an important reagent for hepatitis B immunotherapy.

Cloning of human ScFv against digoxin from a semi-synthetic phage antibody library / 中国免疫学杂志

Objective:To clone human anti digoxin ScFv from a human semi synthetic phage antibody library.Methods:①Digoxin BSA conjugate(Dig BSA) was preparaed by a modified periodate oxidation method.②A semi synthetic phage antibody library was panned against immobilized Dig BSA.Collected clones were analysed by ELISA,inhibition ELISA and DNA Sequencing.Results:①During the four rounds panning against Dig BSA,the enrichment of the eluted phage particles was observed;②Analysis of the eluted clones identified one clone that could bind Dig as well as other digitalis.③Sequencing analysis showed that the variable genes of the positive clone belonged to VH5 and V?1 subgroup respectively.Conclusion:Human Dig specific ScFv that could bind Dig and other digitalis has been cloned from a semi synthetic phage antibody library which may provide a potential reagent for the diagnosis and therapy of Dig toxication.

Affinity Selection of Human ScFv Against Botulinum Neurotoxin Serotype A / 微生物学通报

In this work, rare specific binders to botulinum neurotoxin antigen were selected from human phage immunized library through three rounds of panning in vitro. Of them, clone ScFvB17 is of high affinity and specificity to target antigen. B17 is of 750bp encoding 250 amino acid. Analysis results of gene structure showed V-genes of B17 belonging respectively to VH4 or? chainⅡ family are new antibody Fv genes. More important result showed that recombinant ScFvB17 expressed in E.coli could bind specific for neurotoxin competing with antiserum. Successful selection of human phage antibody library and obtaining specific ScFv against botulinum neurotoxin serotype A provide useful materials for further study on detection of neurotoxin and human engineering therapeutic antitoxin.

High-level Secretion Expression of Human ScFv Against Botulinum Neurotoxin A in Pichia pastoris* / 微生物学通报

The specific ScFv gene against botulinum neurotoxin A (BoNTa)was cloned into pPIC9k. Positive integrators were screened by increasing the dose of G418 in culture and expressed in Pichia pastoris GS115. As a result, engineered recombinant clone were obtained. 26 kD product of interest was seen easily in SDS-PAGE. Expression of human ScFv got the highest level 15% of total secreted proteins during 72～84 h after 1% methanol inducing. Purification of ScFv was finished by two steps: gel filter and ion exchange. Competing ELISA showed that recombinant ScFv could compete with antiserum to specific bind BoNTa.