Screening of High-Affinity scFvs From a Ribosome Displayed Library Using BIAcore Biosensor

Affinity improvement of the fully human anti‑TSLP recombinant antibody

Thymic stromal lymphopoietin (TSLP) is a potentially important target for the treatment of asthma and malignancies. However, a fully human antibody reactive with TSLP is currently unavailable for clinical use. In a previous study, a human anti-TSLP-single-chain antibody variable fragment (anti-TSLP-scFv) 84 was selected by phage display from a constructed human scFv library. In the present study, a computer simulation method was developed using Discovery Studio 4.5 software, to increase the affinity of anti-TSLP-scFv-84. Specific primers were designed and mutated DNA sequences of anti-TSLP-scFvs were obtained by overlap extension PCR. The mutant scFvs were expressed in pLZ16 and affinity-enhanced anti-TSLP-scFv-M4 was screened using ELISA. However, in general the scFvs have low stability and short half-lives in vivo. Therefore, scFv-84 and scFv-M4 were inserted into eukaryotic expression vectors (pcDNA3.1-sp-Fc and PMH3^EN-sp-Fc) and then transfected into 293F cells to express anti-TSLP-scFv-Fc. ELISA and western blotting results indicated the size of the anti-TSLP-scFv-Fc to be ~50 kDa. Binding of anti-TSLP-scFv-Fc-M4 to TSLP was enhanced compared with the pre-mutated scFv-Fc-84. The affinity of the mutated recombinant antibody was determined using the BIAcore technique and found to be ~10-fold greater than the pre-mutated antibody.

Tethered bilayer lipid membranes (tBLMs): interest and applications for biological membrane investigations

Biological membranes play a central role in the biology of the cell. They are not only the hydrophobic barrier allowing separation between two water soluble compartments but also a supra-molecular entity that has vital structural functions. Notably, they are involved in many exchange processes between the outside and inside cellular spaces. Accounting for the complexity of cell membranes, reliable models are needed to acquire current knowledge of the molecular processes occurring in membranes. To simplify the investigation of lipid/protein interactions, the use of biomimetic membranes is an approach that allows manipulation of the lipid composition of specific domains and/or the protein composition, and the evaluation of the reciprocal effects. Since the middle of the 80's, lipid bilayer membranes have been constantly developed as models of biological membranes with the ultimate goal to reincorporate membrane proteins for their functional investigation. In this review, after a brief description of the planar lipid bilayers as biomimetic membrane models, we will focus on the construction of the tethered Bilayer Lipid Membranes, the most promising model for efficient membrane protein reconstitution and investigation of molecular processes occurring in cell membranes.

Construction of human nonimmune library and selection of scFvs against IL-33

Interleukin (IL) 33 plays very important roles in inflammatory and allergic diseases. To select human single-chain Fv fragments (scFvs) against IL-33, a nonimmune phage library system was constructed. The full-length cDNA library was synthesized for amplification of the variable heavy chain (V(H)) and variable light chain (V(L)). By overlapping extension PCR for splicing V(H) and V(L), the full-length scFv library DNA were amplified and then transformed into Escherichia coli TG1. The scFv library was constructed successfully which contained 2.5×10(8) independent clones with full-length scFv inserts. The results of fingerprint maps of the scFvs by BstN I and DNA sequencing from the library at random proved that the library was diverse. The human IL-33 was amplified, expressed, and purified. The purified IL-33 with bioactivity was biotinylated and used as antigen for selection of scFv library by phage display. After three rounds of affinity selection, about 30 % of clones have specific binding activity with IL-33. Five of those with good binding activity were transformed into E. coli strain HB2151 for soluble expression. The selected scFvs were further identified by western blot and sequencing. Those selected scFvs could be used for further research of their effect on inflammatory and allergic diseases such as asthma by blockade of IL-33.

Surface plasmon resonance for high-throughput ligand screening of membrane-bound proteins

Technologies based on surface plasmon resonance (SPR) have allowed rapid, label-free characterization of protein-protein and protein-small molecule interactions. SPR has become the gold standard in industrial and academic settings, in which the interaction between a pair of soluble binding partners is characterized in detail or a library of molecules is screened for binding against a single soluble protein. In spite of these successes, SPR is only beginning to be adapted to the needs of membrane-bound proteins which are difficult to study in situ but represent promising targets for drug and biomarker development. Existing technologies, such as BIAcoreTM, have been adapted for membrane protein analysis by building supported lipid layers or capturing lipid vesicles on existing chips. Newer technologies, still in development, will allow membrane proteins to be presented in native or near-native formats. These include SPR nanopore arrays, in which lipid bilayers containing membrane proteins stably span small pores that are addressable from both sides of the bilayer. Here, we discuss current SPR instrumentation and the potential for SPR nanopore arrays to enable quantitative, high-throughput screening of G protein coupled receptor ligands and applications in basic cellular biology.

Rapid antibody selection by mRNA display on a microfluidic chip

In vitro antibody-display technologies are powerful approaches for isolating monoclonal antibodies from recombinant antibody libraries. However, these display techniques require several rounds of affinity selection which is time-consuming. Here, we combined mRNA display with a microfluidic system for in vitro selection and evolution of antibodies and achieved ultrahigh enrichment efficiency of 10⁶- to 10⁸-fold per round. After only one or two rounds of selection, antibodies with high affinity and specificity were obtained from naïve and randomized single-chain Fv libraries of ∼10¹² molecules. Furthermore, we confirmed that not only protein–protein (antigen–antibody) interactions, but also protein–DNA and protein–drug interactions were selected with ultrahigh efficiencies. This method will facilitate high-throughput preparation of antibodies and identification of protein interactions in proteomic and therapeutic fields.