Development of fluorescence-linked immunosorbent assay for rapid detection of Staphylococcus aureus.

Staphylococcus aureus is a major pathogen that causes infections and life-threatening diseases. Although antibiotics, such as methicillin, have been used, methicillin-resistant S. aureus (MRSA) causes high morbidity and mortality rates, and conventional detection methods are difficult to be used because of time-consuming process. To control the spread of S. aureus, a development of a rapid and simple detection method is required. In this study, we generated a fluorescent anti-S. aureus antibody, and established a novel fluorescence-linked immunosorbent assay (FLISA)-based S. aureus detection method. The method showed high sensitivity and low limit of detection toward MRSA detection. The assay time for FLISA was 5 h, which was faster than that of conventional enzyme-linked immunosorbent assay (ELISA) or rapid ELISA. Moreover, the FLISA-based detection method was applied to diagnose clinically isolated MRSA samples that required only 5.3 h of preincubation. The FLISA method developed in this study can be widely applied as a useful tool for convenient S. aureus detection. KEY POINTS: • A fluorescence-linked immunosorbent assay-based S. aureus detection method • Simultaneous quantification of a maximum of 96 samples within 5 h • Application of the novel system to diagnosis clinical isolates.

Transnuclear mice reveal Peyer's patch iNKT cells that regulate B-cell class switching to IgG1.

Tissue-resident iNKT cells maintain tissue homeostasis and peripheral surveillance against pathogens; however, studying these cells is challenging due to their low abundance and poor recovery from tissues. We here show that iNKT transnuclear mice, generated by somatic cell nuclear transfer, have increased tissue resident iNKT cells. We examined expression of PLZF, T-bet, and RORγt, as well as cytokine/chemokine profiles, and found that both monoclonal and polyclonal iNKT cells differentiated into functional subsets that faithfully replicated those seen in wild-type mice. We detected iNKT cells from tissues in which they are rare, including adipose, lung, skin-draining lymph nodes, and a previously undescribed population in Peyer's patches (PP). PP-NKT cells produce the majority of the IL-4 in Peyer's patches and provide indirect help for B-cell class switching to IgG1 in both transnuclear and wild-type mice. Oral vaccination with α-galactosylceramide shows enhanced fecal IgG1 titers in iNKT cell-sufficient mice. Transcriptional profiling reveals a unique signature of PP-NKT cells, characterized by tissue residency. We thus define PP-NKT as potentially important for surveillance for mucosal pathogens.

Production of Tyrian purple indigoid dye from tryptophan in Escherichia coli.

Tyrian purple, mainly composed of 6,6'-dibromoindigo (6BrIG), is an ancient dye extracted from sea snails and was recently demonstrated as a biocompatible semiconductor material. However, its synthesis remains limited due to uncharacterized biosynthetic pathways and the difficulty of regiospecific bromination. Here, we introduce an effective 6BrIG production strategy in Escherichia coli using tryptophan 6-halogenase SttH, tryptophanase TnaA and flavin-containing monooxygenase MaFMO. Since tryptophan halogenases are expressed in highly insoluble forms in E. coli, a flavin reductase (Fre) that regenerates FADH2 for the halogenase reaction was used as an N-terminal soluble tag of SttH. A consecutive two-cell reaction system was designed to overproduce regiospecifically brominated precursors of 6BrIG by spatiotemporal separation of bromination and bromotryptophan degradation. These approaches led to 315.0 mg l-1 6BrIG production from tryptophan and successful synthesis of regiospecifically dihalogenated indigos. Furthermore, it was demonstrated that 6BrIG overproducing cells can be directly used as a bacterial dye.

Synthesis and biological evaluation of N-(3-fluorobenzyl)-4-(1-(methyl-d3)-1H-indazol-5-yl)-5-(6-methylpyridin-2-yl)-1H-imidazol-2-amine as a novel, potent ALK5 receptor inhibitor.

Specific inhibition of ALK5 provides a novel method for controlling the development of cancers and fibrotic diseases. In this work, a novel series of N-(3-fluorobenzyl)-4-(1-(methyl-d3)-1H-indazol-5-yl)-5-(6-methylpyridin-2-yl)-1H-imidazol-2-amine (11), a potential clinical candidate, was synthesized by strategic incorporation of deuterium at potential metabolic soft spots and identified as ALK5 inhibitors. This compound has a low potential for CYP-mediated drug-drug interactions as a CYP450 inhibitor (IC50 = >10 µM) and showed potent inhibitory effects in cellular assay (IC50 = 3.5 ± 0.4 nM). The pharmacokinetic evaluation of 11 in mice demonstrated moderate clearance (29.0 mL/min/kg) and also revealed high oral bioavailability in mice (F = 67.6%).

Generation of a novel antibody against BxPrx, a diagnostic marker of pine wilt disease.

BACKGROUND: Bursaphelenchus xylophilus is a pathogenic nematode that causes pine wilt disease (PWD). To prevent the rapid spread of this pathogen, developing a method for rapid and accurate detection of B. xylophilus is required. METHODS AND RESULTS: In this study, we produced a B. xylophilus peroxiredoxin (BxPrx), which is a protein that is overexpressed in B. xylophilus. Using recombinant BxPrx as an antigen, we generated and selected a novel antibody that binds to BxPrx via phage display and biopanning. We subcloned the anti-BxPrx single-chain variable fragment-encoding phagemid DNA to mammalian expression vector. We transfected the plasmid into mammalian cells and produced a highly sensitive recombinant antibody that enabled nanogram order detection of BxPrx. CONCLUSION: The sequence of anti-BxPrx antibody as well as the rapid immunoassay system described here can be applied for rapid and accurate diagnosis of PWD.

Tiered human health risk assessment of antibacterial quaternary ammonium compounds (QACs) in dishwashing detergents.

Quaternary ammonium compounds (QACs) are widely used in consumer products because of their unique antibacterial properties, and dishwashing detergents are a major source of exposure through oral, inhalation, and dermal routes. The three classes of QACs, including benzalkonium chloride (BAC), n-alkyldimethylethylbenzylammonium chloride (ADEBAC), and di-n-alkyldimethylammonium chloride (DDAC), in spray and non-spray types of dishwashing detergents were quantified by high-performance liquid chromatography-mass spectrometry. A tiered risk assessment approach was also considered. In the Tier 1 assessment, the mean and worst-case exposure were estimated to screen for rough exposure and risk levels. In the Tier 2 assessment, mean and upper-tail exposure levels were calculated based on the exposure parameters of Korean consumers using Monte Carlo simulation. QACs had a low frequency of detection of up to 20% in dishwashing detergents, and the contents of detected QACs varied depending on the individual samples. Based on the results of the Tier 1 assessment, BACs and DDACs posed potential health risks via inhalation and dermal routes. Tier 2 assessment suggested that the current level of oral and dermal exposure of Korean consumers to QACs in dishwashing detergents is unlikely to pose a health risk, even for upper-tail exposure groups. However, the present results suggest that spray-type DDACs may pose a health risk in the upper-tail inhalation exposure group, and further investigation is required to clarify this risk.

Generation of a novel monoclonal antibody against inflammatory biomarker S100A8 using hybridoma technology.

OBJECTIVES: S100A8 is highly expressed in several inflammatory and oncological conditions. To address the current lack of a reliable and sensitive detection method for S100A8, we generated a monoclonal antibody with a high binding affinity to human S100A8 to enable early disease diagnosis. RESULTS: A soluble recombinant S100A8 protein with a high yield and purity was produced using Escherichia coli. Next, mice were immunized with recombinant S100A8 to obtain anti-human S100A8 monoclonal antibodies using hybridoma technology. Lastly, the high binding activity of the antibody was confirmed and its sequence was identified. CONCLUSIONS: This method, including the production of antigens and antibodies, will be useful for the generation of hybridoma cell lines that produce anti-S100A8 monoclonal antibodies. Moreover, the sequence information of the antibody can be used to develop a recombinant antibody for use in various research and clinical applications.

Simulator evaluation of an intersection maneuver assist system with connected and automated vehicle technologies.

Intersection crashes can be potentially mitigated through vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) safety management systems. It is important, however, to consider some of the human factors related aspects of such systems to maximise potential safety benefits. In this study, Intersection Manoeuvre Assistance Systems were conceptualised and evaluated in a driving simulator. The systems were designed to assist drivers with intersection manoeuvres by making use of connected infrastructure and providing real-time feedback, guidance, and active vehicle controls. The study compared drivers' confidence, workload, glances at the instrument panel, and hazard anticipation when driving using three systems-System A (no alert or assist); System B (alert only); and System C (alert and assist). Study results show differences in drivers' confidence in such systems and potentially degraded visual gaze behaviours.Practitioner summary: Connected infrastructure-based intersection management assistance systems can potentially reduce crashes. This experimental driving simulation study evaluated drivers' perceptions and reactions to intersection management systems. Results indicate reduced confidence in automated systems, reduced visual scanning for external hazards at intersections, and increased off-road glances towards the instrument panel.

Bacterial Production of Recombinant Coagulation Factor VIII Domains.

Factor VIII (F8) is a blood coagulation protein prearranged in six domains, and its deficiency causes hemophilia A. To fashion functional F8 therapeutics, development of a recombinant F8 (rF8) domain is essential not only for F8 substitution, but also to decipher the F8-related mechanisms. In this study, we generated Glutathione S-transferase (GST)-conjugated recombinant A2 and A3 domains of F8 using Escherichia coli. The high growth rate and economically advantageous protein production system in terms of inexpensive reagents and materials in E. coli cells facilitated the completion of entire process from protein expression to purification in 3-4 days with low production cost. Subsequent assessment of these purified proteins using enzyme-linked immunosorbent assay (ELISA) and antibodies against F8 revealed enhanced detection of rF8-A2 or rF8-A3 in a concentration dependent manner, indicating the presence of the antibody-binding epitopes in these proteins. Furthermore, these proteins are suitable for generating novel antibodies against the F8 domain and F8 domain-capturing affinity columns by enabling their conjugation to GST-capturing beads. Additionally, the recombinant F8 domains produced herein can be used for various studies, which include investigating the explicit roles of the F8 domain in the coagulation process, with domain-specific binding partners, and antibodies.

Soluble Expression of a Neo2/15-Conjugated Single Chain Fv against PD-L1 in Escherichia coli.

Immunocytokines, antibody-cytokine fusion proteins, have the potential to improve the therapeutic index of cytokines by delivering the cytokine to the site of localized tumor cells using antibodies. In this study, we produced a recombinant anti-programmed death-ligand 1 (PD-L1) scFv, an antibody fragment against PD-L1 combined with a Neo2/15, which is an engineered interleukin with superior function using an E. coli expression system. We expressed the fusion protein in a soluble form and purified it, resulting in high yield and purity. The high PD-L1-binding efficiency of the fusion protein was confirmed via enzyme-linked immunosorbent assay, suggesting the application of this immunocytokine as a cancer-related therapeutic agent.

A rapid ELISA for the detection of matrix metallopeptidase 9 using a recombinant Fab-type antibody.

Matrix metalloproteinase 9 (MMP9) contributes to several aspects of inflammation and cancer pathology, including invasion, metastasis, and angiogenesis. In this study, we expressed a recombinant fragment antigen-binding (Fab)-type anti-MMP9 antibody in Escherichia coli with high purity within five days and confirmed the nanomolar order of antigen-binding efficiency of the recombinant Fab. Moreover, we optimized the experimental time for performing enzyme-linked immunosorbent assay (ELISA), and decreased the reaction time from the conventional 20.5 h to 3.5 h. The rapid and sensitive MMP9 detection system developed in this study can be applied to a range of applications, including the diagnosis of diseases with MMP9 overexpression including inflammatory and cancer-related diseases.

Development of a CHO cell line for stable production of recombinant antibodies against human MMP9.

BACKGROUND: Human matrix metalloproteinase 9 (hMMP9) is a biomarker in several diseases, including cancer, and the need for developing detectors and inhibitors of hMMP9 is increasing. As an antibody against hMMP9 can be selectively bound to hMMP9, the use of anti-MMP9 antibody presents new possibilities to address hMMP9-related diseases. In this study, we aimed to establish a stable Chinese hamster ovary (CHO) cell line for the stable production of antibodies against hMMP9. RESULTS: Weconstructed recombinant anti-hMMP9 antibody fragment-expressing genes and transfected these to CHO cells. We chose a single clone, and successfully produced a full-sized antibody against hMMP9 with high purity, sensitivity, and reproducibility. Subsequently, we confirmed the antigen-binding efficiency of the antibody. CONCLUSIONS: We developed a novel recombinant anti-hMMP9 antibody via a CHO cell-based mammalian expression system, which has a high potential to be used in a broad range of medical and industrial areas.

Generation of a recombinant antibody for sensitive detection of Pseudomonas aeruginosa.

Pseudomonas aeruginosa (P. aeruginosa) is a major pathogen that causes nosocomial infections and often exhibits antibiotic resistance. Therefore, the development of an accurate method for detecting P. aeruginosa is required to control P. aeruginosa-related outbreaks. In this study, we established an enzyme-linked immunosorbent assay method for the sensitive detection of three P. aeruginosa strains, UCBPP PA14, ATCC 27853, and multidrug-resistant ATCC BAA-2108. We produced a recombinant antibody (rAb) against P. aeruginosa V-antigen (PcrV), which is a needle tip protein of the type III secretion system of P. aeruginosa using mammalian cells with high yield and purity, and confirmed its P. aeruginosa binding efficiency. The rAb was paired with commercial anti-P. aeruginosa Ab for a sandwich ELISA, resulting in an antigen-concentration-dependent response with a limit of detection value of 230 CFU/mL. These results suggest that the rAb produced herein can be used for the sensitive detection of P. aeruginosa with a wide range of applications in clinical diagnosis and point-of-care testing.

Expression of soluble recombinant human matrix metalloproteinase 9 and generation of its monoclonal antibody.

We have successfully produced a recombinant human matrix metalloproteinase 9 (hMMP9) antigen with high yield and purity and used it to generate a hybridoma cell-culture-based monoclonal anti-hMMP9 antibody. We selected the most effective antibody for binding antigens and successfully identified its nucleotide sequence. The entire antigen and antibody developmental procedures described herein can be a practical approach for producing large amounts of monoclonal antibodies against hMMP9 and other antigens of interest. Additionally, the nucleotide sequence information of the anti-hMMP9 monoclonal antibody revealed herein will be useful for the generation of recombinant antibodies or antibody fragments against hMMP9.

In-depth characterization of non-human sialic acid (Neu5Gc) in human serum using label-free ZIC-HILIC/MRM-MS.

Sialic acid Neu5Gc, a non-human glycan, is recognized as a new harmful substance that can cause vascular disease and cancer. Humans are unable to synthesize Neu5Gc due to a genetic defect that converts Neu5Ac to Neu5Gc, but Neu5Gc is often observed in human biological samples. Therefore, the demand for accurately measuring the amount of Neu5Gc present in human blood or tissues is rapidly increasing, but there is still no method to reliably quantify trace amounts of a non-human sugar. In particular, selective isolation and detection of Neu5Gc from human serum is analytically challenging due to the presence of excess sialic acid Neu5Ac, which has physicochemical properties very similar to Neu5Gc. Herein, we developed the label-free approach based on ZIC-HILIC/MRM-MS that can enrich sialic acids released from human serum and simultaneously monitor Neu5Ac and Neu5Gc. The combination of complete separation of Neu5Gc from abundant Neu5Ac by hydrophilic and electrostatic interactions with selective monitoring of structure-specific cross-ring cleavage ions generated by negative CID-MS/MS was remarkably effective for quantification of Neu5Ac and Neu5Gc at the femtomole level. Indeed, we were able to successfully determine the absolute quantitation of Neu5Gc from 30 healthy donors in the range of 3.336 ± 1.252 pg/µL (mean ± SD), 10,000 times lower than Neu5Ac. In particular, analysis of sialic acids in protein-free serum revealed that both Neu5Ac and Neu5G are mostly bound to proteins and/or lipids, but not in free form. In addition, the correlation between expression level of Neu5Gc and biological factors such as BMI, age, and sex was investigated. This method can be widely used in studies requiring sialic acid-related measurements such as disease diagnosis or prediction of immunogenicity in biopharmaceuticals as it is both fast and highly sensitive.

Production of a Soluble Recombinant Antibody Fragment against MMP9 Using Escherichia coli.

Matrix metalloproteinase 9 (MMP9) is involved in several aspects of the pathology of cancer, including invasion, metastasis, and angiogenesis. In this study, we expressed a recombinant scFv-type anti-MMP9 antibody in soluble form using Escherichia coli, purified it, and confirmed its antigen-binding ability. The convenient, rapid, inexpressive system used in this study for producing recombinant antibody fragments needs only five days, and thus can be used for the efficient production of scFv against MMP9, which can be used in a range of applications and industrial fields, including diagnosis and treatment of inflammatory and cancer-related diseases.

Characterization of a Tryptophan 6-Halogenase from Streptomyces albus and Its Regioselectivity Determinants.

Tryptophan halogenases are found in diverse organisms and catalyze regiospecific halogenation. They play an important role in the biosynthesis of halogenated indole alkaloids, which are biologically active and of therapeutic importance. Here, a tryptophan 6-halogenase (SatH) from Streptomyces albus was characterized by using a whole-cell reaction system in Escherichia coli. SatH showed substrate specificity for chloride and bromide ions, leading to regiospecific halogenation at the C6-position of l-tryptophan. In addition, SatH exhibited higher performance in bromination than that of previously reported tryptophan halogenases in the whole-cell reaction system. Through structure-based protein mutagenesis, it has been revealed that two consecutive residues, A78/V79 in SatH and G77/I78 in PyrH, are key determinants in the regioselectivity difference between tryptophan 6- and 5-halogenases. Substituting the AV with GI residues switched the regioselectivity of SatH by moving the orientation of tryptophan. These data contribute to an understanding of the key residues that determine the regioselectivity of tryptophan halogenases.

Detection and destruction of HER2-positive cancer cells by Ultra Quenchbody-siRNA complex.

Ultra Quenchbody (UQ-body) is a biosensor that utilizes the quenching behavior of the fluorescent dye linked to the antibody V region. When the corresponding antigen is bound to the UQ-body, the fluorescence is restored and allows the detection of target molecules easily and sensitively. In this paper, we constructed UQ-bodies to sensitively detect the human epidermal growth factor receptor 2 (HER2) cancer marker in solution or on cancer cells, which was further used to kill the cancer cells. A synthetic Fab fragment of anti-HER2 antibody Fab37 with many Trp residues at hypervariable region was prepared and labeled with fluorescent dyes to obtain the UQ-bodies. The UQ-body could detect HER2 in solution at concentrations as low as 20 pM with an EC50 of 0.3 nM with a fourfold response. Fluorescence imaging of HER2-positive cells was successfully performed without any washing steps. To deliver small interfering RNA (siRNA) to cancer cells, a modified UQ-body with C-terminal 9R sequence was also prepared. HER2-positive cancer cells were effectively killed by polo-like kinase 1 siRNA intracellularly delivered by the UQ-body-9R. The novel approach employing siRNA-empowered UQ-body could detect and image the HER2 antigen easily and sensitively, and effectively kill the HER2-positive cancer cells.

Diagnostic ability of salivary matrix metalloproteinase-9 lateral flow test point-of-care test for periodontitis.

AIM: This cross-sectional study aimed to examine the diagnostic ability of salivary matrix metalloproteinase (MMP)-9 lateral flow test (LFT) point-of-care (POC) kit and develop an algorithm for diagnosis of periodontitis. MATERIALS AND METHODS: Through Seoul National Dental Hospital, 137 participants (46 LFT negatives, 91 LFT positives) were recruited. For salivary diagnostics, 150 µl of the unstimulated saliva was applied to LFT-POC kit. To make a diagnosis of periodontitis, stage II-IV in modified new international classification system was used. Covariates encompassing age, sex, smoking and obesity were evaluated through face-to-face interview. Enzyme-linked immunosorbent assay was used for quantification of salivary MMP-9. To develop a diagnostic algorithm, multivariable logistic regression analysis was used. Receiver operating characteristic curve was applied for evaluating diagnostic ability. RESULTS: Diagnostic ability of salivary MMP-9 LFT-POC test was 0.82 (sensitivity of 0.92, specificity of 0.72) in total participants. Diagnostic algorithm using POC test resulted in a response equation, that is algorithm score = -3.675 + 2.877*LFT + 0.034*age + 0.121*sex + 0.372*smoking + 0.192*obesity. Diagnostic ability of the algorithm was 0.88 (sensitivity of 0.92, specificity of 0.85) with cut-off score of 0.589. CONCLUSIONS: Salivary MMP-9 LFT-POC kit showed appropriate diagnostic ability for periodontitis and would be an efficient tool for screening of periodontitis.

Rapid detection of the neonicotinoid insecticide imidacloprid using a quenchbody assay.

Contamination of the land and water by neonicotinoid insecticide residues is currently a severe environmental problem. However, the traditional methods for pesticide residue analysis are time consuming and laborious. To tackle this problem, here we describe a novel quenchbody (Q-body) immunoassay reagent that allows the rapid and sensitive detection of imidacloprid, one of the most frequently used neonicotinoid pesticides, in aqueous solution. A Q-body comprises an antibody Fab fragment that is site-specifically labeled with a fluorescent dye. The Fab fragment quenches the dye with its internal tryptophan residues via photoinduced electron transfer. The subsequent addition of imidacloprid stabilizes the antibody structure and displaces the quenched dye to the outside of the protein, resulting in increased fluorescence. The constructed Q-body assay exhibited a high dynamic range and a low limit of detection (10 ng mL-1), and the entire assay procedure could be completed in a few minutes. The assay showed a low cross-reactivity with possible interfering analogous compounds, indicating that it has a good selectivity. Hence, the developed Q-body assay has excellent potential as a universal technology for monitoring neonicotinoid residues in environmental and food samples. Graphical abstract A novel quenchbody (Q-body) immunoassay reagent that allows the rapid and sensitive detection of imidacloprid, one of the most frequently used neonicotinoid pesticides, in aqueous solution was developed. The addition of imidacloprid stabilizes the Q-body structure and displaces the quenched dye to the outside of the protein, resulting in increased fluorescence. The constructed Q-body assay exhibited a high dynamic range and a low limit of detection (10 ng mL-1), and completed in a few minutes.