scholarly journals Construction and directional evolution of anti-enrofloxacin ScFv antibody for the immunoassay of fluoroquinolones

Author(s):  
Guangxu Xing ◽  
Yunshang Zhang ◽  
Fangyu Wang ◽  
Liuding Wen ◽  
Gaiping Zhang

Abstract A recombinant anti-enrofloxacin single-chain antibody (scFv) was produced for the detection of enrofloxacin. An immunized mouse phage display scFv library with a capacity of 2.35×109 CFU/mL was constructed and used for anti-enrofloxacin scFv screening. After four rounds of bio-panning, 10 positives were isolated and identified successfully. The highest positive scFv was expressed in E. coli BL21. Then, its recognition mechanisms were studied using the molecular docking method. The result showed the amino acid residues Leu121 were the key residues for the binding of ScFv to ENR. Based on the results of virtual mutation, the ScFv antibody was evolved by directional mutagenesis of contact amino acid residue Leu121 to Asn. After the expression and purification, an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) based on the parental and mutant ScFv were established for enrofloxacin respectively. The IC50 value of the assay established with the ScFv mutant was 1.63 ng/mL, while the parental ScFv was 21.08 ng/mL, this result showed highly increased affinity with up to 12.9-folds improved sensitivity. The mean recovery for ENR ranged from 71.80% to 117.35% with 10.46% relative standard deviation between the intra-assay and the inter-assay. The results indicate that we have obtained a highly sensitive anti-ENR scFv by the phage library construction and directional evolution, and the scFv-based IC-ELISA is suitable for the detection of ENR residue in animal derived edible tissues and milk.

2021 ◽  
Author(s):  
Fangyu Wang ◽  
Ning Li ◽  
Yunshang Zhang ◽  
Xuxefeng Sun ◽  
Yali Zhao ◽  
...  

Abstract A recombinant anti-enrofloxacin single-chain antibody (scFv) was produced for the detection of enrofloxacin. An immunized mouse phage display scFv library with a capacity of 2.35×109 CFU/mL was constructed and used for anti-enrofloxacin scFv screening. After four rounds of bio-panning, 10 positives were isolated and identified successfully. The highest positive scFv was expressed in E. coli BL21. Then, its recognition mechanisms were studied using the molecular docking method. The result showed the amino acid residues Leu121 were the key residues for the binding of ScFv to ENR. Based on the results of virtual mutation, the ScFv antibody was evolved by directional mutagenesis of contact amino acid residue Leu121 to Asn. After the expression and purification, an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) based on the parental and mutant ScFv were established for enrofloxacin respectively. The IC50 value of the assay established with the ScFv mutant was 1.63 ng/mL, while the parental ScFv was 21.08 ng/mL, this result showed highly increased affinity with up to 12.9-folds improved sensitivity. The mean recovery for ENR ranged from 71.80% to 117.35% with 10.46% relative standard deviation between the intra-assay and the inter-assay. The results indicate that we have obtained a highly sensitive anti-ENR scFv by the phage library construction and directional evolution, and the scFv-based IC-ELISA is suitable for the detection of ENR residue in animal derived edible tissues and milk.


Foods ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1933
Author(s):  
Fangyu Wang ◽  
Ning Li ◽  
Yunshang Zhang ◽  
Xuefeng Sun ◽  
Man Hu ◽  
...  

An immunized mouse phage display scFv library with a capacity of 3.34 × 109 CFU/mL was constructed and used for screening of recombinant anti-ciprofloxacin single-chain antibody for the detection of ciprofloxacin (CIP) in animal-derived food. After four rounds of bio-panning, 25 positives were isolated and identified successfully. The highest positive scFv-22 was expressed in E. coli BL21. Then, its recognition mechanisms were studied using the molecular docking method. The result showed the amino acid residue Val160 was the key residue for the binding of scFv to CIP. Based on the results of virtual mutation, the scFv antibody was evolved by directional mutagenesis of contact amino acid residue Val160 to Ser. After the expression and purification, an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) based on the parental and mutant scFv was established for CIP, respectively. The IC50 value of the assay established with the ScFv mutant was 1.58 ng/mL, while the parental scFv was 26.23 ng/mL; this result showed highly increased affinity, with up to 16.6-fold improved sensitivity. The mean recovery for CIP ranged from 73.80% to 123.35%, with 10.46% relative standard deviation between the intra-assay and the inter-assay. The RSD values ranged between 1.49% and 9.81%. The results indicate that we obtained a highly sensitive anti-CIP scFv by the phage library construction and directional evolution, and the scFv-based IC-ELISA is suitable for the detection of CIP residue in animal-derived edible tissues.


Toxins ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 273
Author(s):  
Caixia Zhang ◽  
Weiqi Zhang ◽  
Xiaoqian Tang ◽  
Qi Zhang ◽  
Wen Zhang ◽  
...  

Anti-idiotypic nanobodies, usually expressed by gene engineering protocol, has been shown as a nontoxic coating antigen for toxic compound immunoassays. We here focused on how to increase immunoassay sensitivity by changing the nanobody’s primary sequence. In the experiments, two anti-idiotype nanobodies against monoclonal antibody 1H2, which is specific to ochratoxin A, were obtained and named as nontoxic coating antigen 1 (NCA1) and nontoxic coating antigen 2 (NCA2). Three differences between the nanobodies were discovered. First, there are six amino acid residues (AAR) of changes in the complementarity determining region (CDR), which compose the antigen-binding site. One of them locates in CDR1 (I–L), two of them in CDR2 (G–D, E–K), and three of them in CDR3 (Y–H, Y–W). Second, the affinity constant of NCA1 was tested as 1.20 × 108 L mol−1, which is about 4 times lower than that of NCA2 (5.36 × 108 L mol−1). Third, the sensitivity (50% inhibition concentration) of NCA1 for OTA was shown as 0.052 ng mL−1, which was 3.5 times lower than that of nontoxic coating antigen 2 (0.015 ng mL−1). The results indicate that the AAR changes in CDR of the anti-idiotypic nanobodies, from nonpolar to polar, increasing the affinity constant may enhance the immunoassay sensitivity. In addition, by using the nontoxic coating antigen 2 to substitute the routine synthetic toxic antigen, we established an eco-friendly and green enzyme-linked immunosorbent assay (ELISA) method for rapid detection of ochratoxin A in cereals. The half-maximal inhibitory concentration (IC50) of optimized ELISA was 0.017 ng mL−1 with a limit of detection (LOD) of 0.003 ng mL−1. The optimized immunoassay showed that the average recoveries of spiked corn, rice, and wheat were between 80% and 114.8%, with the relative standard deviation (RSD) ranging from 3.1–12.3%. Therefore, we provided not only basic knowledge on how to improve the structure of anti-idiotype nanobody for increasing assay sensitivity, but also an available eco-friendly ELISA for ochratoxin A in cereals.


2019 ◽  
Vol 8 (1) ◽  
pp. 24-31
Author(s):  
Chol-Jin Kim ◽  
Sunll Choe ◽  
Kum-Chol Ri ◽  
Chol-Ho Kim ◽  
Hyon-Gwang Li ◽  
...  

Background: The focus of this study was the selection of a single chain variable fragment antibody (scFv) against subtilisin BRC, a fibrinolytic enzyme using phage display, and to characterize the interaction between the antibody and subtilisin BRC. Methods: The subtilisin BRC-specific phage clones were selected using Griffin.1 scFv phage library and sequenced. The gene of subtilisin BRC-specific scFv (scFv-BRC) from selected phage clone was expressed in E. coli and scFv-BRC was characterized. Molecular modeling of the three-dimensional (3D) structures of scFv-BRC was performed using MODELLER 9.19 modeling software and assessed by PROCHEK. Molecular docking of subtilisin BRC with scFv-BRC was carried out using PATCHDOCK. Results: The size of scFv-BRC gene is 635bp and it consists of 54bp of heavy chain region (VH), 336bp of light chain region (VL), 45bp of a linker. scFv-BRC was actively expressed by E. coli expression vector pET28a-scFv in E. coli BL21 (DE3), and the amount of expressed scFv-BRC was about 50 mg/L. Its molecular weight is ~26kDa. The CDR domain of scFv-BRC consists of 6 amino acids in CDR L1, 3 amino acids in CDR L2 and 9 amino acids in CDR L3. Docking results of subtilisin BRC and scFv-BRC showed global energy of - 56.29 kJ/mol. Furthermore, the results showed that amino acid residues in subtilisin BRC for binding with scFv-BRC are Tyr6, Ser182, Ser204, and Gln206. Conclusion: scFv against subtilisin BRC selected using phage display showed relatively strong binding energy with subtilisin BRC. The amino acid residues in subtilisin BRC for binding with scFv-BRC are not relevant to that in subtilisin BRC for binding with its substrates. These results suggested that scFv-BRC can be used as a ligand for detection and affinity purification of subtilisin BRC.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Patamalai Boonserm ◽  
Songchan Puthong ◽  
Thanaporn Wichai ◽  
Sajee Noitang ◽  
Pongsak Khunrae ◽  
...  

AbstractIt is important to understand the amino acid residues that govern the properties of the binding between antibodies and ligands. We studied the binding of two anti-norfloxacins, anti-nor 132 and anti-nor 155, and the fluoroquinolones norfloxacin, enrofloxacin, ciprofloxacin, and ofloxacin. Binding cross-reactivities tested by an indirect competitive enzyme-linked immunosorbent assay indicated that anti-nor 132 (22–100%) had a broader range of cross-reactivity than anti-nor 155 (62–100%). These cross-reactivities correlated with variations in the numbers of interacting amino acid residues and their positions. Molecular docking was employed to investigate the molecular interactions between the fluoroquinolones and the monoclonal antibodies. Homology models of the heavy chain and light chain variable regions of each mAb 3D structure were docked with the fluoroquinolones targeting the crucial part of the complementarity-determining regions. The fluoroquinolone binding site of anti-nor 155 was a region of the HCDR3 and LCDR3 loops in which hydrogen bonds were formed with TYR (H:35), ASN (H:101), LYS (H:106), ASN (L:92), and ASN (L:93). These regions were further away in anti-nor 132 and could not contact the fluoroquinolones. Another binding region consisting of HIS (L:38) and ASP (H:100) was found for norfloxacin, enrofloxacin, and ciprofloxacin, whereas only ASP (H:100) was found for ofloxacin.


Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 517
Author(s):  
Seohee Chang ◽  
Soohyun Kim ◽  
Jerome Han ◽  
Suji Ha ◽  
Hyunho Lee ◽  
...  

Phage display is one of the most frequently used platform technologies utilized to screen and select therapeutic antibodies, and has contributed to the development of more than 10 therapeutic antibodies used in the clinic. Despite advantages like efficiency and low cost, it has intrinsic technical limitations, such as the asymmetrical amplification of the library after each round of biopanning, which is regarded as a reason for it yielding a very limited number of antigen binders. In this study, we developed a high-throughput single-clonal screening system comprised of fluorescence immunoassays and a laser-driven clonal DNA retrieval system using microchip technology. Using this system, from a single-chain variable fragment (scFv) library displayed on phages with a complexity of 5.21 × 105 harboring random mutations at five amino acid residues, more than 70,000 clones—corresponding to ~14% of the library complexity—were screened, resulting in 78 antigen-reactive scFv sequences with mutations restricted to the randomized residues. Our results demonstrate that this system can significantly reduce the number of biopanning rounds, or even eliminate the need for this process for libraries with lower complexity, providing an opportunity to obtain more diverse clones from the library.


1977 ◽  
Author(s):  
T. E. Petersen ◽  
G. Dudek-Wojciechowska ◽  
L. Sottrup-Jensen ◽  
S. Magnusson

Human antithrombin-III is a single-chain glycoprotein with three disulfide bridges and four prosthetic glucosamine-based oligosaccharide groups. The disulfide bridges have been established. In four fragments of 208, 168, 3 and 46 amino acid residues, resp. 415 of the appr. 425 residues have been sequenced. The four oligosaccharide groups are attached to four Asn-residues within a sequence region of 95 residues. No extensive sequence homology with the trypsin inhibitors has been observed. One chymotryptic peptide was found to be a substrate for bovine factor Xa, cleaving the arginyl bond in the sequence -Ile-Val-Ala-Glu-Gly-Arg-Asp-. A second peptide is cleaved by thrombin. It is not clear whether these sites are inhibitor sites in the native molecule. Other possible candidates for inhibitor sites are a -Val-Leu-Ile-Leu-Pro-Lys-Pro- sequence (similar to the sequence 40-48 of hirudin, which also includes a -Pro-Lys-Pro- sequence) and also the C-terminal sequence -Gly-Arg-Val-Ala-Asn-Pro-Cys-Val-Lys.


1972 ◽  
Vol 128 (4) ◽  
pp. 961-970 ◽  
Author(s):  
L. R. Croft

The amino acid sequence of γ-crystallin (fraction II) from calf lens has been determined; this indicates it to be a single-chain polypeptide of 165 amino acid residues.


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