Dynamic single-cell phenotyping of immune cells using the microfluidic platform DropMap.

Characterization of immune responses is currently hampered by the lack of systems enabling quantitative and dynamic phenotypic characterization of individual cells and, in particular, analysis of secreted proteins such as cytokines and antibodies. We recently developed a simple and robust microfluidic platform, DropMap, to measure simultaneously the kinetics of secretion and other cellular characteristics, including endocytosis activity, viability and expression of cell-surface markers, from tens of thousands of single immune cells. Single cells are compartmentalized in 50-pL droplets and analyzed using fluorescence microscopy combined with an immunoassay based on fluorescence relocation to paramagnetic nanoparticles aligned to form beadlines in a magnetic field. The protocol typically takes 8-10 h after preparation of microfluidic chips and chambers, which can be done in advance. By contrast, enzyme-linked immunospot (ELISPOT), flow cytometry, time-of-flight mass cytometry (CyTOF), and single-cell sequencing enable only end-point measurements and do not enable direct, quantitative measurement of secreted proteins. We illustrate how this system can be used to profile downregulation of tumor necrosis factor-α (TNF-α) secretion by single monocytes in septic shock patients, to study immune responses by measuring rates of cytokine secretion from single T cells, and to measure affinity of antibodies secreted by single B cells.

Combination of ribosome display and next generation sequencing as a powerful method for identification of affibody binders against ß-lactamase CTX-M15.

CTX-M15 is one of the most widespread, extended spectrum ß-lactamases, a major determinant of antibiotic resistance representing urgent public health threats, among enterobacterial strains infecting humans and animals. Here we describe the selection of binders to CTX-M15 from a combinatorial affibody library displayed on ribosomes. Upon three increasingly selective ribosome display iterations, selected variants were identified by next generation sequencing (NGS). Nine affibody variants with high relative abundance bearing QRP and QLH amino acid motifs at residues 9-11 were produced and characterized in terms of stability, affinity and specificity. All affibodies were correctly folded, with affinities ranging from 0.04 to 2 µM towards CTX-M15, and successfully recognized CTX-M15 in bacterial lysates, culture supernatants and on whole bacteria. It was further demonstrated that the binding of affibody molecules to CTX-M15 modulated the enzyme's kinetic parameters. This work provides an approach using ribosome display coupled to NGS for the rapid generation of protein ligands of interest in diagnostic and research applications.

Mutants with higher stability and specific activity from a single thermosensitive variant of T7 RNA polymerase.

A single strategy to select RNA polymerase from bacteriophage T7 (T7 RNAP) mutants in Escherichia coli with enhanced thermostability or enzymatic activity is described. T7 RNAP has the ability to specifically transcribe genes under control of T7 phage promoter. By using random mutagenesis of the T7 RNAP gene in combination with an appropriate screening at 25 and 42°C, we have generated and selected E.coli clones with temperature-sensitive phenotype in the presence of chloramphenicol. The resistance to chloramphenicol used to select these clones results from expression control of the chloramphenicol acetyl transferase gene by the T7 promoter. In a second phase, and using the thermosensitive T7 RNAP variants as template, a new round of random mutagenesis was performed. Combined to an appropriate screening strategy, 11 mutations (second-site T7 RNAP revertants) that restore the initial resistance to chloramphenicol at 42°C were identified. Nine of these mutations increase the thermal resistance of the wild-type T7 RNA. They include the five mutations previously described using different approaches and four novel mutations. One improves T7 RNA catalytic activity and one has no positive effect on the natural enzyme but increases the activity of some combined mutants. Additive effects of mutations amount to an increase of as much as 10°C in T1/2 compared with the wild-type enzyme and up to a 2-fold activity enhancement.

NucliSENS EasyQ HPV v1 test - Testing for oncogenic activity of human papillomaviruses.

BACKGROUND: Analytical sensitivity of DNA-based assays to detect infection with human papillomaviruses is very high, but clinical specificity for cervical cancer strongly depends on the age of the patient and case classification. To solve the dilemma between sensitivity and specificity, a new generation of assays focuses on the pathogenic factors that underlie the development of HPV-associated tumors: the expression of the viral oncogenes E6 and E7. Demonstration of persistent expression of these mRNAs or expression in the context of relevant clinical symptoms has a strong positive predictive value for the development of HPV-associated carcinomas and strongly warrants further diagnostic action. OBJECTIVES: The NucliSENS EasyQ HPV v1 test was designed to test cervical scrapes for the expression of the oncogenic E6/E7 mRNA from the five most common carcinogenic HPV types (16, 18, 31, 33 and 45). The test can be used for confirmation and risk stratification of individuals with proven infection with high risk papillomaviruses. STUDY DESIGN: In order to establish performance of the assay, sensitivity, specificity, repeatability, and reproducibility were determined with artificial and clinical specimens. Further, a total of 420 cervical scrapes were tested and the results directly compared to the CE-market device PreTect HPV-Proofer assay (NorChip, Klokkarstua, Norway). For arbitration of discordant clinical results, the specimens were rated according to Pap-classification and the presence of HPV DNA was determined. RESULTS: The limit of detection for the five HPV types 16, 18, 31, 33, and 45 ranged from 2.3x10(2) to 3.0x10(4) copies/mL on a background of 5x10(3) HPV-negative HS67 cells. No cross-reactivity for other viral, bacterial, or fungal agents known to be potentially present in cervical fluids was detected. Repeatability and reproducibility were shown by testing panels of HPV-spiked artificial and clinical samples. A comparative analysis of 420 cervical scrapes demonstrated an overall concordance of >90% between the NucliSENS EasyQ HPV test and the technologically related PreTect HPV-Proofer assay.

Rapid real-time nucleic Acid sequence-based amplification-molecular beacon platform to detect fungal and bacterial bloodstream infections.

Bloodstream infections (BSIs) are a significant cause of morbidity and mortality. Successful patient outcomes are diminished by a failure to rapidly diagnose these infections and initiate appropriate therapy. A rapid and reliable diagnostic platform of high sensitivity is needed for the management of patients with BSIs. The combination of an RNA-dependent nucleic acid sequence-based amplification and molecular beacon (NASBA-MB) detection system in multiplex format was developed to rapidly detect medically important BSI organisms. Probes and primers representing pan-gram-negative, pan-gram-positive, pan-fungal, pan-Candida, and pan-Aspergillus organisms were established utilizing 16S and 28S rRNA targets for bacteria and fungi, respectively. Two multiplex panels were developed to rapidly discriminate bacterial or fungal infections at the subkingdom/genus level with a sensitivity of 1 to 50 genomes. A clinical study was performed to evaluate the accuracy of this platform by evaluating 570 clinical samples from a tertiary-care hospital group using blood bottle samples. The sensitivity, specificity, and Youden's index values for pan-gram-positive detection and pan-gram-negative detection were 99.7%, 100%, 0.997 and 98.6%, 95.9%, 0.945, respectively. The positive predictive values (PPV) and the negative predictive values (NPV) for these two probes were 100, 90.7, and 99.4, 99.4, respectively. Pan-fungal and pan-Candida probes showed 100% sensitivity, specificity, PPV, and NPV, and the pan-Aspergillus probe showed 100% NPV. Robust signals were observed for all probes in the multiplex panels, with signal detection in <15 min. The multiplex real-time NASBA-MB assay provides a valuable platform for the rapid and specific diagnosis of bloodstream pathogens, and reliable pathogen identification and characterization can be obtained in under 3 h.

High-density DNA probe arrays for identification of staphylococci to the species level.

Rapid and accurate identification and speciation of staphylococci clinical isolates is important for predicting medical pathology. We evaluated the ability of a high-density DNA probe array based on 16S rDNA sequences to identify Staphylococcus species. Correct identification was observed for 185 out of the 201 strains (92%). Of the 33 tested species, the array was able to correctly identify 30 of them. The total time required for identification of 4 isolates was 5 h. Such a tool represents a powerful method for routine microbiological diagnostic as well as for epidemiological studies.

Universal labeling chemistry for nucleic acid detection on DNA chips.

An efficient strategy for nucleic acid labeling and analysis on deoxyribonucleic acid (DNA) chips has been developed. This approach, which combines the fragmentation and the labeling steps, is based on the reactivity of the phosphates of DNA and ribonucleic acid (RNA) fragments and is using reporter molecules bearing a bromomethyl- or aryldiazomethane-reactive group. In this chapter, we describe the preparation of the reactive label and protocols for efficient labeling of any nucleic acid sequence, DNA or RNA, prior to their hybridization, detection, and analysis on DNA chips.

Evaluation of a high-density oligonucleotide array for characterization of grlA, grlB, gyrA and gyrB mutations in fluoroquinolone resistant Staphylococcus aureus isolates.

Using high-density oligonucleotide array technology, 30 Staphylococcus aureus strains were studied for the presence of mutations in genes involved in fluoroquinolone resistance: grlA, gyrA, grlB and gyrB. For the two most important genes, gyrA and grlA, correlation with sequencing reached 95.1%. If all genes were considered, correlation was 88.8%.

Aryldiazomethanes for universal labeling of nucleic acids and analysis on DNA chips.

DNA and RNA labeling and detection are key steps in nucleic acid-based technologies, used in medical research and molecular diagnostics. We report here the synthesis, reactivity, and potential of a new type of labeling molecule, m-(N-Biotinoylamino)phenylmethyldiazomethane (m-BioPMDAM), that reacts selectively and efficiently with phosphates in nucleotide monomers, oligonucleotides, DNA, and RNA. This molecule contains a biotin as detectable unit and a diazomethyl function as reactive moiety. We demonstrate that this label fulfills the requirements of stability, solubility, reactivity, and selectivity for hybridization-based analysis and especially for detection on high-density DNA chips.

Multilocus sequence typing of Staphylococcus aureus with DNA array technology.

A newly developed oligonucleotide array suited for multilocus sequence typing (MLST) of Staphylococcus aureus strains was analyzed with two strain collections in a two-center study. MLST allele identification for the first strain collection fully agreed with conventional strain typing. Analysis of strains from the second collection revealed that chip-defined MLST was concordant with conventional MLST. Array-mediated MLST data were reproducible, exchangeable, and epidemiologically concordant.