Amplification-Free SARS-CoV-2 Detection Using Nanoyeast-scFv and Ultrasensitive Plasmonic Nanobox-Integrated Nanomixing Microassay

The implementation of accurate and sensitive molecular detection for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is paramount to effectively control the ongoing coronavirus disease 2019 (COVID-19) pandemic. In this regard, we herein propose the specific and highly sensitive SARS-CoV-2 detection based on nanoyeast single-chain-variable fragment (scFv) and ultrasensitive plasmonic nanobox-integrated nanomixing microassay. Importantly, this designed platform showcases the utility of nanoyeast-scFvs as specific capture reagents targeting the receptor-binding domain (RBD) of the virus and as monoclonal antibody alternatives suitable for cost-effective mass production and frequent testing. By capitalizing on single-particle active nanoboxes as plasmonic nanostructures for surface-enhanced Raman scattering (SERS), the microassay utilizes highly sensitive Raman signals to indicate virus infection. The developed microassay further integrated nanomixing for accelerating molecular collisions. Through the synergistic working of nanoyeast-scFv, plasmonic nanoboxes, and nanomixing, the highly specific and sensitive SARS-CoV-2 detection is achieved as low as 17 virus/μL without any molecular amplification. We successfully demonstrate SARS-CoV-2 detection in saliva samples of simulated patients at clinically relevant viral loads, suggesting the possibility of this platform for accurate and noninvasive patient screening.

Anti-Human Epidermal Growth Factor Receptor 2 Single-Chain Fv Fragment-Decorated DM1 Nanoparticles for Specific Targeting of Human Epidermal Growth Factor Receptor 2-Positive Breast Tumor Cells

PURPOSE

Although monoclonal antibodies are used to decorate nanoparticles to target specific cells, penetration of tumor tissues by monoclonal antibodies is limited by their large size. Therefore, we prepared DM1 nanoparticles decorated with the small anti-HER2 single-chain Fv fragment (scFvHER2) of trastuzumab (TMAB) for targeting to human epidermal growth factor receptor 2 (HER2) overexpressing in breast cancer effectively.

METHODS

ScFvHER2 fragment was coupled with DM1 nanoparticles (NPs) via covalent thiol-maleimide linkages. Their physicochemical properties, uptake by cells, and toxicity to tumor cells were investigated. Their vivo biodistribution was assessed employing liquid chromatographytandem mass spectrometry, while their antitumor activity was investigated in nude mice burdened with BT-474 tumor.

RESULTS

Viability of BT-474 cells incubated with scFvHER2-DM1-Nanoparticles (scFv-DM1-NPs) was significantly lower than that of BT-474 cell treated with TMAB-DM1-Nanoparticles (TMAB-DM1-NPs) (P < 0 05). Uptake by cells of scFvDM1-NPs was significantly higher than TMAB-DM1-NPs (P < 0 01). Accumulation of scFv-DM1-NPs in tumor tissue was notably higher than TMAB-DM1-NPs (P < 0 05). scFv-DM1-NPs exhibited improved antitumor effects compared to TMABDM1-NPs (P < 0 05), showing a tumor inhibition rate of more than 70%.

CONCLUSIONS

ScFvHER2 fragment could serve as a more effective targeting ligand than TMAB, and scFv-DM1-NPs could be developed as a possible drug delivery system to target HER2-positive breast cancer.

[Establishment and optimization of an ELISA for affinity detection of single-chain antibodies to EGFRvIII]

Objective To establish an ELISA for the detection of the affinity of the epidermal growth factor receptor variant III (EGFRvIII ) single-chain antibodies PD0721, and optimize the experimental conditions. Methods An indirect ELISA for the detection of the affinity of the PD0721 single-chain antibody which was prepared by our laboratory was established. By square matrix titration method of indirect ELISA, the experimental conditions including antibody and antigen concentrations and coating conditions were optimized, and finally the sensitivity and precision of the method were analyzed. Results The antigen was diluted with PBS to 1.25 mg/L and coated at 4 DegreesCelsius for 12 hours, 120 ng/mL PD0721 single-chain antibody and enzyme-labeled antibody at the dilution of 1:8000 were added for the best results. Indirect ELISA exhibited high performance within a dynamic range 15 ng/mL-480 ng/mL, and the limit of detection (LOD) was 7.5 ng/mL. The intra-assay coefficient variations (CV) ranged from 0.11% to 0.99% and inter-assay CV ranged from 0.68% to 3.15%. Conclusion An accurate and stable ELISA for detecting the affinity of PD0721 single-chain antibody has been established, which laid a foundation for future preparation of antibody-conjugated drugs.

Sterols in an intramolecular channel of Smoothened mediate Hedgehog signaling

Smoothened (SMO), a class Frizzled G protein-coupled receptor (class F GPCR), transduces the Hedgehog signal across the cell membrane. Sterols can bind to its extracellular cysteine-rich domain (CRD) and to several sites in the seven transmembrane helices (7-TMs) of SMO. However, the mechanism by which sterols regulate SMO via multiple sites is unknown. Here we determined the structures of SMO-Gi complexes bound to the synthetic SMO agonist (SAG) and to 24(S),25-epoxycholesterol (24(S),25-EC). A novel sterol-binding site in the extracellular extension of TM6 was revealed to connect other sites in 7-TMs and CRD, forming an intramolecular sterol channel from the middle side of 7-TMs to CRD. Additional structures of two gain-of-function variants, SMOD384R and SMOG111C/I496C, showed that blocking the channel at its midpoints allows sterols to occupy the binding sites in 7-TMs, thereby activating SMO. These data indicate that sterol transport through the core of SMO is a major regulator of SMO-mediated signaling.

Recombinant Endoglin-Single-Chain Variable Fragment/ Induced Protein 10 Fusion Protein Potently Boosts the Anti-Tumor Efficacy of Adoptively Transferred TRP2-Specific CD8+ CD28+ Cytotoxic T Lymphocytes in Mice

In this research, we studied the therapeutic efficacy of a newly designed fusion protein containing Endoglin single-chain variable fragment and IP10 (Endoglin-scFv/IP10), together with our recently generated TRP2-specific CD8⁺ CD28⁺ CTLs (CD8⁺ CD28⁺ CTLs) in controlling melanoma growth in mice. The recombinant Endoglin-scFv/IP10 was expressed in E. coli, purified by affinity chromatography, and characterized in vitro for its chemotactic movement and immunoreactivity with endoglin-expressing cells. In vivo, melanoma xenografts were established in mice (C57BL/6) using B16F10 cells. After that, mice were treated with intravenous injections of vehicle (PBS), Endoglin-scFv/IP10 alone, CD8⁺ CD28⁺ CTLs alone, or Endoglin-scFv/IP10⁺ CD8⁺ CD28⁺ CTLs. The therapeutic efficacy was assessed by monitoring tumor growth, mouse survival and cellular biomarkers. Endoglin-scFv/IP10 fusion protein combined with CD8⁺ CD28⁺ CTLs observed a reduction in tumor growth, resulting in improved survival. On the cellular level, the combination treatment dramatically reduced the number of systemic and tumor associated myeloid-derived suppressor cells or regulatory T cells, increased tumor-responsive interferon-γ-producing lymphocytes and tumor-associated CD8⁺ CXCR3⁺ T cells, and inhibited proliferation and angiogenesis but stimulated apoptosis within melanoma tissue. This study demonstrates the therapeutic potential of Endoglin-scFv/IP10 fusion protein in combination with CD8⁺ CD28⁺ CTLs in melanoma treatment.

Engineering of an enhanced synthetic Notch receptor by reducing ligand-independent activation

Notch signaling is highly conserved in most animals and plays critical roles during neurogenesis as well as embryonic development. Synthetic Notch-based systems, modeled from Notch receptors, have been developed to sense and respond to a specific extracellular signal. Recent advancement of synNotch has shown promise for future use in cellular engineering to treat cancers. However, synNotch from Morsut et al. (2016) has a high level of ligand-independent activation, which limits its application. Here we show that adding an intracellular hydrophobic sequence (QHGQLWF, named as RAM7) present in native Notch, significantly reduced ligand-independent activation. Our enhanced synthetic Notch receptor (esNotch) demonstrates up to a 14.6-fold reduction in ligand-independent activation, without affecting its antigen-induced activation efficiency. Our work improves a previously reported transmembrane receptor and provides a powerful tool to develop better transmembrane signaling transduction modules for further advancement of eukaryotic synthetic biology.

[Preparation and identification of single-chain fragment variable against epidermal growth factor receptor 3]

Objective To express, purify and identify the single-chain fragment variable (scFv) against human epidermal growth factor receptor 3 (HER3). Methods We searched NCBI for the light chain sequence and heavy chain sequence of anti-HER3 mAb LJM716 to construct the gene of scFv against HER3. The recombinant expression vector pGAPZαA-anit-HER3-scFv was constructed using the constitutive expression vector pGAPZαA and then electro-transformed into Pichia Pastoris X-33 to screen the strains with high expression of the protein of interest. After shaking flask fermentation, the supernatant was purified by hydrophobic chromatography and metal ion affinity chromatography. The purified product was identified by Western blotting and ELISA. Results The anti-HER3-scFv gene was successfully constructed and the strains with high expression of anti-HER3-scFv were obtained. The anti-HER3-scFv was purified to a purity of more than 95% by two-step chromatography, and the purified yield was 192 mg/L. Western blotting showed that the anti-HER3-scFv was correctly expressed and ELISA indicated that anti-HER3-scFv could specifically recognize HER3. Conclusion The anti-HER3-scFv has been successfully prepared.

Human C5-specific single-chain variable fragment ameliorates brain injury in a model of NMOSD

Objective

Using phage display, we sought to screen single-chain variable fragments (scFvs) against complement C5 to treat neuromyelitis optica spectrum disorder (NMOSD).

Methods

After 5 rounds of phage display, we isolated individual clones and identified phage clones specifically binding to C5 using ELISA. Using aquaporin-4 (AQP4)-transfected cells in vitro, we confirmed whether these scFvs prevented complement-dependent cytotoxicity (CDC) caused by the serum of patients with NMOSD and human complement (hC). We selected an NMOSD mouse model, in which intracerebral NMOSD immunoglobulin G (IgG) and hC injections induce NMOSD-like lesions in vivo.

Results

We obtained scFvs to test specificity and blocking efficiency. The scFv C5B3 neutralized C5 in the complement activation pathway, which prevented AQP4-IgG-mediated CDC in AQP4-transfected cells. In an NMOSD mouse model, C5B3 prevented AQP4 and astrocyte loss, decreased demyelination, and reduced inflammatory infiltration and membrane attack complex formation in lesions.

Conclusions

We used phage display to screen C5B3 against C5, which was effective in inhibiting cytotoxicity in vitro and preventing CNS pathology in vivo.

Enhanced delivery of siRNA to triple negative breast cancer cells in vitro and in vivo through functionalizing lipid-coated calcium phosphate nanoparticles with dual target ligands

The conjugation of ligands to nanoparticle platforms for the target delivery of therapeutic agents to the tumor tissue is one of the promising anti-cancer strategies. However, conventional nanoparticle platforms are not so effective in terms of the selectivity and transfection efficiency. In this study, we designed and developed a dual-target drug/gene delivery system based on lipid-coated calcium phosphate (LCP) nanoparticles (NPs) for significantly enhanced siRNA cellular uptake and transfection efficiency. LCP NPs loaded with therapeutic siRNA were conjugated with a controlled number of folic acid and/or EGFR-specific single chain fragment antibody (ABX-EGF scFv). The uptake of ABX-EGF scFv-modified (LCP-scFv) and folic acid-modified LCP NPs (LCP-FA) by human breast tumor cells (MDA-MB-468) was significantly higher with an optimal ligand density on each NP surface (LCP-125scFv and LCP-100FA). Co-conjugation with sub-optimal dual ligands (50 FA and 75 ABX-EGF scFv) per LCP NP (LCP-50FA-75scFv) further enhanced the cellular uptake. More significantly, much more NPs were delivered to the MDA-MB-468 tumor tissue in the nude mouse model when LCP-50FA-75scFv NPs were used. Therefore, the new dual-ligand LCP NPs may be a valuable targeting system for human breast cancer diagnosis and therapy.

Effects of dietary recombinant chlorella supplementation on growth performance, meat quality, blood characteristics, excreta microflora, and nutrient digestibility in broilers

The use of chlorella as an immune stimulant to enhance nonspecific host defense mechanisms or as an antimicrobial to inhibit bacterial growth has been reported. Thus, the aim of the present study was to clarify the effect of recombinant chlorella supplementation on growth performance, meat quality, and the blood profile, excreta microflora, and nutrient digestibility in broilers. A total of 375 one-day-old ROSS 308 broilers (male and female) were allotted to 5 dietary treatments using 5 cages with 15 chicks per cage. Treatments were: 1) NC, basal diet supplemented with 1.0% E. coli fermented liquor (EFL); 2) PC1, 0.2% EFL with chlorella; 3) PC2, 1.0% EFL with chlorella; 4) T1, 0.2% EFL with chlorella (anti-viral); and 5) T2, 1.0% EFL with chlorella (anti-viral). The broilers in the T2 treatment groups showed higher body weight gain (BGW) by 2.55% (P < 0.01) and lower feed conversion ratio (FCR) by 2.75% (P < 0.05) compared with those fed the control NC treatment group. Moreover, the blood contents of blood urea nitrogen (BUN), creatinine, and IgA in the broilers of the T2 treatment group were significantly increased by 28.12, 23.07, and 29.72%, respectively -more than those found in the broilers of the NC treatment group (P < 0.01). In contrast, the LDL/C in the blood from the animals in the T2 treatment group was significantly decreased by 23.23% - more than that in the blood from the NC broilers (P < 0.05). Based on these results, we suggest that the dietary supplementation of broilers with recombinant chlorella could improve their growth performance, increase the concentration of IgA and apparently metabolizable nitrogen in the blood, and decrease ammonia emissions. Therefore, our findings have important implications for the effect of recombinant chlorella supplementation through increasing the concentration of IgA and the level of metabolizable nitrogen.

Leishmania donovani tyrosyl-tRNA synthetase structure in complex with a tyrosyl adenylate analog and comparisons with human and protozoan counterparts

The crystal structure of Leishmania donovani tyrosyl-tRNA synthetase (LdTyrRS) in complex with a nanobody and the tyrosyl adenylate analog TyrSA was determined at 2.75 Å resolution. Nanobodies are the variable domains of camelid heavy chain-only antibodies. The nanobody makes numerous crystal contacts and in addition reduces the flexibility of a loop of LdTyrRS. TyrSA is engaged in many interactions with active site residues occupying the tyrosine and adenine binding pockets. The LdTyrRS polypeptide chain consists of two pseudo-monomers, each consisting of two domains. Comparing the two independent chains in the asymmetric unit reveals that the two pseudo-monomers of LdTyrRS can bend with respect to each other essentially as rigid bodies. This flexibility might be useful in the positioning of tRNA for catalysis since both pseudo-monomers in the LdTyrRS chain are needed for charging tRNATyr. An "extra pocket" (EP) appears to be present near the adenine binding region of LdTyrRS. Since this pocket is absent in the two human homologous enzymes, the EP provides interesting opportunities for obtaining selective drugs for treating infections caused by L. donovani, a unicellular parasite causing visceral leishmaniasis, or kala azar, which claims 20,000 to 30,000 deaths per year. Sequence and structural comparisons indicate that the EP is a characteristic which also occurs in the active site of several other important pathogenic protozoa. Therefore, the structure of LdTyrRS could inspire the design of compounds useful for treating several different parasitic diseases.

A Simple and Specific Noncompetitive ELISA Method for HT-2 Toxin Detection

We developed an HT-2 toxin-specific simple ELISA format with a positive read-out. The assay is based on an anti-immune complex (IC) scFv antibody fragment, which is genetically fused with alkaline phosphatase (AP). The anti-IC antibody specifically recognizes the IC between a primary anti-HT-2 toxin Fab fragment and an HT-2 toxin molecule. In the IC ELISA format, the sample is added together with the scFv-AP antibody to the ELISA plate coated with the primary antibody. After 15 min of incubation and a washing step, the ELISA response is read. A competitive ELISA including only the primary antibody recognizes both HT-2 and T-2 toxins. The anti-IC antibody makes the assay specific for HT-2 toxin, and the IC ELISA is over 10 times more sensitive compared to the competitive assay. Three different naturally contaminated matrices: wheat, barley and oats, were used to evaluate the assay performance with real samples. The corresponding limits of detection were 0.3 ng/mL (13 µg/kg), 0.1 ng/mL (4 µg/kg) and 0.3 ng/mL (16 µg/kg), respectively. The IC ELISA can be used for screening HT-2 toxin specifically and in relevant concentration ranges from all three tested grain matrices.

Nanoyeast and Other Cell Envelope Compositions for Protein Studies and Biosensor Applications

Rapid progress in disease biomarker discovery has increased the need for robust detection technologies. In the past several years, the designs of many immunoaffinity reagents have focused on lowering costs and improving specificity while also promoting stability. Antibody fragments (scFvs) have long been displayed on the surface of yeast and phage libraries for selection; however, the stable production of such fragments presents challenges that hamper their widespread use in diagnostics. Membrane and cell wall proteins similarly suffer from stability problems when solubilized from their native environment. Recently, cell envelope compositions that maintain membrane proteins in native or native-like lipid environment to improve their stability have been developed. This cell envelope composition approach has now been adapted toward stabilizing antibody fragments by retaining their native cell wall environment. A new class of immunoaffinity reagents has been developed that maintains antibody fragment attachment to yeast cell wall. Herein, we review recent strategies that incorporate cell wall fragments with functional scFvs, which are designed for easy production while maintaining specificity and stability when in use with simple detection platforms. These cell wall based antibody fragments are globular in structure, and heterogeneous in size, with fragments ranging from tens to hundreds of nanometers in size. These fragments appear to retain activity once immobilized onto biosensor surfaces for the specific and sensitive detection of pathogen antigens. They can be quickly and economically generated from a yeast display library and stored lyophilized, at room temperature, for up to a year with little effect on stability. This new format of scFvs provides stability, in a simple and low-cost manner toward the use of scFvs in biosensor applications. The production and "panning" of such antibody cell wall composites are also extremely facile, enabling the rapid adoption of stable and inexpensive affinity reagents for emerging infectious threats.

Advancing the global proteome survey platform by using an oriented single chain antibody fragment immobilization approach

Increasing the understanding of a proteome and how its protein composition is affected by for example different diseases, such as cancer, has the potential to improve strategies for early diagnosis and therapeutics. The Global Proteome Survey or GPS is a method that combines mass spectrometry and affinity enrichment with the use of antibodies. The technology enables profiling of complex proteomes in a species independent manner. The sensitivity of GPS, and other methods relying on affinity enrichment, is largely affected by the activity of the exploited affinity reagent. We here present an improvement of the GPS platform by utilizing an antibody immobilization approach which ensures a controlled immobilization process of the antibody to the magnetic bead support. More specifically, we make use of an antibody format that enables site-directed biotinylation and use this in combination with streptavidin coated magnetic beads. The performance of the expanded GPS platform was evaluated by profiling yeast proteome samples. We demonstrate that the oriented antibody immobilization strategy increases the ability of the GPS platform and results in larger fraction of functional antibodies. Additionally, we show that this new antibody format enabled in-solution capture, i.e. immobilization of the antibodies after sample incubation. A workflow has been established that permit the use of an oriented immobilization strategy for the GPS platform.

Antibody-Mediated Pathogen Resistance in Plants

The methods described in this chapter were developed in order to produce transgenic plants expressing pathogen-specific single-chain variable fragment (scFv) antibodies fused to antifungal peptides (AFPs), conferring resistance against fungal pathogens. We describe the selection from a phage display library of avian scFv antibodies that recognize cell surface proteins on fungi from the genus Fusarium, and the construction of scFv-AFP fusion protein constructs followed by their transient expression in tobacco (Nicotiana spp.) plants and stable expression in Arabidopsis thaliana plants. Using these techniques, the antibody fusion with the most promising in vitro activity can be used to generate transgenic plants that are resistant to pathogens such as Fusarium oxysporum f. sp. matthiolae.

Development of Human-Like scFv-Fc Neutralizing Botulinum Neurotoxin E

Background

Botulinum neurotoxins (BoNTs) are considered to be the most toxic substances known on earth and are responsible for human botulism, a life-threatening disease characterized by flaccid muscle paralysis that occurs naturally by food-poisoning or colonization of the gastrointestinal tract by BoNT-producing clostridia. BoNTs have been classified as category A agent by the Centers of Disease Control and Prevention (CDC) and are listed among the six agents with the highest risk to be used as bioweapons. Neutralizing antibodies are required for the development of effective anti-botulism therapies to deal with the potential risk of exposure.

Results

In this study, a macaque (Macaca fascicularis) was immunized with recombinant light chain of BoNT/E3 and an immune phage display library was constructed. After a multi-step panning, several antibody fragments (scFv, single chain fragment variable) with nanomolar affinities were isolated, that inhibited the endopeptidase activity of pure BoNT/E3 in vitro by targeting its light chain. Furthermore, three scFv were confirmed to neutralize BoNT/E3 induced paralysis in an ex vivo mouse phrenic nerve-hemidiaphragm assay. The most effective neutralization (20LD₅₀/mL, BoNT/E3) was observed with scFv ELC18, with a minimum neutralizing concentration at 0.3 nM. Furthermore, ELC18 was highly effective in vivo when administered as an scFv-Fc construct. Complete protection of 1LD₅₀ BoNT/E3 was observed with 1.6 ng/dose in the mouse flaccid paralysis assay.

Conclusion

These scFv-Fcs antibodies are the first recombinant antibodies neutralizing BoNT/E by targeting its light chain. The human-like nature of the isolated antibodies is predicting a good tolerance for further clinical development.

Enzyme-linked immunosorbent assay with monoclonal and single-chain variable fragment antibodies selective to coplanar polychlorinated biphenyls

Coplanar polychlorinated biphenyls (Co-PCBs) consisting of non-ortho and mono-ortho-chlorinated PCBs are dioxin-like compounds and cause wide contamination in the environment. To monitor Co-PCB residues, it was attempted to establish an enzyme-linked immunosorbent assay (ELISA) with monoclonal and recombinant antibodies selective to Co-PCBs. When 3,3',5,5'-tetrachlorobiphenoxybutyric acid (PCBH)-keyhole limpet hemocyanin conjugate was immunized into mice, two monoclonal antibodies, Mab-0217 and Mab-4444, were obtained. 3,3',5,5'-Tetrachlorobiphenyl (PCB80) was determined with an IC(50) value of 2.6 and 0.46 ng mL(-1) in ELISA based on Mab-0217 and Mab-4444, respectively. Mab-4444 cross-reacted with Co-PCB congeners, except for PCB77 and PCB81. Mab-0217 reacted with PCB80 and cross-reacted with PCB111. A single-chain variable fragment (scFv) antibody derived from Mab-4444 was produced in recombinant Escherichia coli cells. The scFv antibody showed nearly the same sensitivity toward PCBH as the parent monoclonal antibody in ELISA. These results clearly suggested that Mab-4444 and its scFv antibodies were suitable for monitoring the representative congeners of Co-PCBs.

Expressivity tag: a novel tool for increased expression in Escherichia coli

Protein expression in Escherichia coli is rarely trivial as low expression and insolubility are common problems. In this work we define a fusion partner, which increases expression levels similarly to the distinct function of solubility and affinity tags. This type of fusion tag we term an expressivity tag. Our work is based on earlier observations where 3' deletions of the InfB gene displays strongly increased expression levels. We have constructed progressively shortened fragments of the InfB(1-471) gene and fused gene fragments to a gfp reporter gene. A 5-fold increase in GFP expression was seen for an optimal 21 nucleotide InfB(1-21) sequence compared to gfp independently. We defined the InfB(1-21) sequence as an expressivity tag. The tag was tested for improved expression of two biotechnological important proteins streptavidin and a single chain antibody (scFv). Expression of both streptavidin and scFv(L32) was improved as evaluated by SDS-PAGE. Calculation of folding energies in the translation initiation region gave higher free energies for gfp, L32 and streptavidin when linked to InfB(1-21) than independently. InfB(1-21) did however not improve the codon usage or codon adaptation index. The expressivity tag is an important addition to the box of tools available for optimizing heterologous protein expression.

Activated platelets in carotid artery thrombosis in mice can be selectively targeted with a radiolabeled single-chain antibody

Background

Activated platelets can be found on the surface of inflamed, rupture-prone and ruptured plaques as well as in intravascular thrombosis. They are key players in thrombosis and atherosclerosis. In this study we describe the construction of a radiolabeled single-chain antibody targeting the LIBS-epitope of activated platelets to selectively depict platelet activation and wall-adherent non-occlusive thrombosis in a mouse model with nuclear imaging using in vitro and ex vivo autoradiography as well as small animal SPECT-CT for in vivo analysis.

Methodology/Principal Findings

LIBS as well as an unspecific control single-chain antibody were labeled with ¹¹¹Indium (¹¹¹In) via bifunctional DTPA ( = ¹¹¹In-LIBS/¹¹¹In-control). Autoradiography after incubation with ¹¹¹In-LIBS on activated platelets in vitro (mean 3866±28 DLU/mm², 4010±630 DLU/mm² and 4520±293 DLU/mm²) produced a significantly higher ligand uptake compared to ¹¹¹In-control (2101±76 DLU/mm², 1181±96 DLU/mm² and 1866±246 DLU/mm²) indicating a specific binding to activated platelets; P<0.05. Applying these findings to an ex vivo mouse model of carotid artery thrombosis revealed a significant increase in ligand uptake after injection of ¹¹¹In-LIBS in the presence of small thrombi compared to the non-injured side, as confirmed by histology (49630±10650 DLU/mm² vs. 17390±7470 DLU/mm²; P<0.05). These findings could also be reproduced in vivo. SPECT-CT analysis of the injured carotid artery with ¹¹¹In-LIBS resulted in a significant increase of the target-to-background ratio compared to ¹¹¹In-control (1.99±0.36 vs. 1.1±0.24; P<0.01).

Conclusions/Significance

Nuclear imaging with ¹¹¹In-LIBS allows the detection of platelet activation in vitro and ex vivo with high sensitivity. Using SPECT-CT, wall-adherent activated platelets in carotid arteries could be depicted in vivo. These results encourage further studies elucidating the role of activated platelets in plaque pathology and atherosclerosis and might be of interest for further developments towards clinical application.

Rise and fall of an anti-MUC1 specific antibody

BACKGROUND

So far, human antibodies with good affinity and specificity for MUC1, a transmembrane protein overexpressed on breast cancers and ovarian carcinomas, and thus a promising target for therapy, were very difficult to generate.

RESULTS

A human scFv antibody was isolated from an immune library derived from breast cancer patients immunised with MUC1. The anti-MUC1 scFv reacted with tumour cells in more than 80% of 228 tissue sections of mamma carcinoma samples, while showing very low reactivity with a large panel of non-tumour tissues. By mutagenesis and phage display, affinity of scFvs was increased up to 500fold to 5,7×10(-10) M. Half-life in serum was improved from below 1 day to more than 4 weeks and was correlated with the dimerisation tendency of the individual scFvs. The scFv bound to T47D and MCF-7 mammalian cancer cell lines were recloned into the scFv-Fc and IgG format resulting in decrease of affinity of one binder. The IgG variants with the highest affinity were tested in mouse xenograft models using MCF-7 and OVCAR tumour cells. However, the experiments showed no significant decrease in tumour growth or increase in the survival rates. To study the reasons for the failure of the xenograft experiments, ADCC was analysed in vitro using MCF-7 and OVCAR3 target cells, revealing a low ADCC, possibly due to internalisation, as detected for MCF-7 cells.

CONCLUSIONS

Antibody phage display starting with immune libraries and followed by affinity maturation is a powerful strategy to generate high affinity human antibodies to difficult targets, in this case shown by the creation of a highly specific antibody with subnanomolar affinity to a very small epitope consisting of four amino acids. Despite these "best in class" binding parameters, the therapeutic success of this antibody was prevented by the target biology.

Cancer therapy with bispecific antibodies: Clinical experience

The binding of at least two molecular targets simultaneously with a single bispecific antibody is an attractive concept. The use of bispecific antibodies as possible therapeutic agents for cancer treatment was proposed in the mid-1980s. The design and production of bispecific antibodies using antibody- and/or receptor-based platform technology has improved significantly with advances in the knowledge of molecular manipulations, protein engineering techniques, and the expression of antigens and receptors on healthy and malignant cells. The common strategy for making bispecific antibodies involves combining the variable domains of the desired mAbs into a single bispecific structure. Many different formats of bispecific antibodies have been generated within the research field of bispecific immunotherapeutics, including the chemical heteroconjugation of two complete molecules or fragments of mAbs, quadromas, F(ab')2, diabodies, tandem diabodies and single-chain antibodies. This review describes key modifications in the development of bispecific antibodies that can improve their efficacy and stability, and provides a clinical perspective on the application of bispecific antibodies for the treatment of solid and liquid tumors, including the promises and research limitations of this approach.

[Antibody engineering: barnase-barstar module as a molecular constructor]

Today, antibody engineering for clinical applications is a rapidly progressing field of science and a big business. The basic functions of an antibody can be spatially differentiated and attributed to various structural domains of a molecule. Therefore, each of them may be an object for engineering with the aim of using a definite antibody function. In this sense, the potential of antibodies is unique. In this article, recent achievements and current problems of antibody engineering are briefly reviewed. The main attention is focused on a molecular constructor that allows for obtaining, with the help of a versatile barnase-barstar module, mono- and multiva-lent miniantibodies and their derivatives with outlined properties.

[A novel protein equalizer based on single chain variable fragment display M13 phage library for nephropathy patient urine study]

A novel protein equalizer was developed with single chain variable fragment (scFv) library displaying M13 phage covalently bonded on monolithic cryogel. Due to the great number and various kinds of displayed scFv fragments, as well as strong and specific binding capacity between scFv fragments and proteins, a new protein equalizer technology is preferable in the pretreatment of complex protein samples. After the sample dissolved in phosphate buffer solution (PBS), it was repeatedly loaded onto the equalizer for five times, the bound proteins were in sequence eluted by 2 mol/L NaCl and 50 mmol/L Gly-HC1 (pH 2.5) solution, followed by digestion with thrombin. All proteins or peptides collected from each fraction were further analyzed by high performance liquid chromatography-electrospray tandem mass spectrometry (RPLC-ESI-MS/MS) with a serially coupled long microcolumn. Compared with the untreated samples, the identified protein number was increased from 142 to 396. Furthermore, from sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis results, it was found that the protein concentration difference was reduced obviously in the eluant of direct sample loading, and most high abundance proteins were identified in the eluant of NaCl. All these results demonstrate that the novel protein equalizer with scFv display M13 phage library immobilized on cyrogel could effectively reduce the dynamic range of proteins in complex samples, enabling the identification of more low abundance proteins.