Construction and sequencing analysis of scFv antibody fragment derived from monoclonal antibody against norfloxacin (Nor155)

The development of single-chain antibody anchored on the BmE cell membrane to inhibit BmNPV infection

Bombyx mori nucleopolyhedrovirus (BmNPV) poses a significant threat to sericulture production, and traditional sanitation practices remain the main strategy for controlling BmNPV infection. Although RNAi targeting BmNPV genes engineered into transgenic silkworms has shown to be a promising approach in reducing viral infection, it cannot block viral entry into host cells. Therefore, there is an urgent need to develop new effective prevention and control measures. In this study, we screened a monoclonal antibody 6C5 that potently neutralizes BmNPV infection by clamping the internal fusion loop of the BmNPVglycoprotein64 (GP64). Furthermore, we cloned the VH and VL fragments of mAb-6C5 from the hybridoma cell, and the eukaryotic expression vector of scFv6C5 was constructed to anchor the antibody on the cell membrane. The GP64 fusion loop antibody-expressing cells exhibited a reduced capacity for BmNPV infection. The results from our study provide a novel BmNPV control strategy and lay the foundation for the future development of transgenic silkworms with improved antiviral efficacy.

Generation, selection and modification of anti-cardiac troponin I antibodies with high specificity and affinity

Current diagnosis of acute myocardial infarction involves quantification of circulating cTn levels. This work endeavoured to generate and enhance recombinant antibody fragments targeting various epitopes on the N- and C-terminals of the cTnI molecule, thereby facilitating highly sensitive detection of the troponin molecule. From this approach, two anti-cTnI scFv antibodies were successfully selected using either phage display or structural reformatting of full length anti-cTnI IgG. Their antibody binding affinity was further optimised via chain shuffling and/or site directed mutagenesis, resulting in scFv with heightened sensitivity when compared to the wild-type scFv. If used in conjunction with existing anti-mid fragment cTnI antibodies, these N- and C- terminal-targeting scFvs show high potential for the enhancement of current cTnI detection assays by limiting the effects from cTnI degradation or troponin complex formation.

Recombinant antibodies and their use for food immunoanalysis

Antibodies are widely employed as biorecognition elements for the detection of a plethora of compounds including food and environmental contaminants, biomarkers, or illicit drugs. They are also applied in therapeutics for the treatment of several disorders. Recent recommendations from the EU on animal protection and the replacement of animal-derived antibodies by non-animal-derived ones have raised a great controversy in the scientific community. The application of recombinant antibodies is expected to achieve a high growth rate in the years to come thanks to their versatility and beneficial characteristics in comparison to monoclonal and polyclonal antibodies, such as stability in harsh conditions, small size, relatively low production costs, and batch-to-batch reproducibility. This review describes the characteristics, advantages, and disadvantages of recombinant antibodies including antigen-binding fragments (Fab), single-chain fragment variable (scFv), and single-domain antibodies (V_HH) and their application in food analysis with especial emphasis on the analysis of biotoxins, antibiotics, pesticides, and foodborne pathogens. Although the wide application of recombinant antibodies has been hampered by a number of challenges, this review demonstrates their potential for the sensitive, selective, and rapid detection of food contaminants.

Isolation and characterization of a novel GRP78-specific single-chain variable fragment (scFv) using ribosome display method

Glucose-regulated protein 78 (GRP78) is a well-characterized endoplasmic reticulum (ER) chaperon frequently overexpressed at the surface of tumor cells and associated with tumor survival, metastasis, and chemoresistance. Hence, potential GRP78 binders emerge as promising candidates for cancer therapy and diagnosis. We applied ribosome display to isolate a single-chain variable domain (scFv) specific for the C-terminal domain of a recombinant human GRP78 (CGRP). Six female BALB/c mice were immunized and then splenocyte mRNA was extracted. An scFv-ribosome display library was established by joining the amplified V_H/Vκ fragments through a 72-bp linker using overlap extension PCR. Then, selection was performed by applying two rounds of eukaryotic ribosome display panning with stepwise decreased amount of CGRP. Ultimately, the selected scFv was characterized using the indirect-ELISA assay, competitive-ELISA assay, Western blotting, Surface Plasmon Resonance (SPR), and in-silico analyses. The constructed library had a length of ~ 1100 bp and the high-affinity scFvs were isolated using the outputs of the final panning round. Among 60 positive clones, GSF3 was selected and its expression, purification, and binding capacity was confirmed by SDS-PAGE and Western blotting. GSF3 exhibited an affinity of 13 × 10⁷ M^-1 to CGRP as assessed by SPR. Moreover, the in-silico analyses indicated that GSF3 binds the C-terminal domain of GRP78 through key residues engaged in antibody-antigen interactions. We found that ribosome display is a swift and reliable technique for specific and high-affinity scFv isolation. Moreover, our results suggest that GSF3 might be applied as a potential cancer immunotherapeutic and diagnostic tool if this approach is carefully followed by successful preclinical and clinical evaluations to validate the findings for further confirmation.

Design and evaluation of scFv-RTX-A as a novel immunotoxin for breast cancer treatment: an in silico approach

Human epidermal growth factor receptor 2 (HER2) is overexpressed in breast cancer (BC) patients. Hence, immunotherapy is a proper treatment option for HER2-positive BC patients. Accumulating evidence has indicated that immunotoxin therapy is a novel approach to improve the potency of targeted therapy. Immunotoxins are antibodies or antibody fragments coupled with a toxin. We designed an immunotoxin. The physicochemical properties were evaluated using ProtParam servers and secondary structure was examined by PROSO II and GORV. Using I-TASSER, a 3D model was built and refined by GalaxyRefine. The model was validated using PROCHECK and RAMPAGE. To predict immunotoxin allergenicity and mRNA stability, AlgPred server and RNAfold were used. Furthermore, the immunotoxin and HER2 were docked by ZDOCK. The scFv+RTX-A could be a non-allergenic and stable chimeric protein, and the secondary structure of its components did not alter, and this protein had a proper 3D structure that might have stable mRNA structure which could bind to HER2. Given the fact that the designed immunotoxin was a non-allergenic and stable chimeric protein and that it could bind with high affinity to HER2 receptors, we proposed that this chimeric protein could be a useful candidate for HER-2 positive BC patients.