American Express

Résumé

American Express (aussi abrégé en Amex ou AmEx), fondée en est une entreprise américaine spécialisée dans les moyens de paiement, notamment les cartes de paiement ainsi que ses chèques de voyage. Elle est le quatrième réseau mondial, au niveau du nombre de titulaires de cartes comme au titre du nombre total de commerçants acceptant des cartes de paiement, le premier étant le réseau acceptant les cartes émises par la société chinoise Union Pay, le second étant le réseau Visa et le troisième étant constitué par les commerçants acceptant les cartes Mastercard. Créée en 1850, elle était à l’origine une entreprise de messagerie et de transport de fonds, issue de la fusion de trois entreprises : Wells, Fargo et Butterfield. Histoire gauche|vignette|Action de l'American Express Company en date du . En 1841, Henry Wells crée une entreprise de transport de fonds (Wells & Company) dans l'État de New York. En 1845, William Fargo fonde une entreprise concurrente (Livingston, Fargo

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https://fr.wikipedia.org/wiki/American_Express

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Concepts associés (28)

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The Semantics of COALA in CO-OPN/2

This report presents the formal semantics of COALA, a design language based on the concept of Coordinated Atomic Actions (CA actions). COALA has been developped with the intent of providing a concrete language to express CA actions and thus facilitate the desing of softwares whose structure relies on this concept. The semantics is expressed using the formal object-oriented specification language CO-OPN/2. The complete semantics is given in the appendix; specifications were checked (syntax and types) using the tools developped for CO-OPN/2.

1999

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The goal of this thesis was to evaluate the use of artificial transposon systems for the generation of recombinant cell pools and cell lines with Chinese hamster ovary (CHO) cells as the production host. Transposons are naturally occurring genetic elements present in the genome of most organisms. Several transposons of metazoan origin have been engineered to facilitate the integration of one or more recombinant genes (transgenes) into the genome of the host cell. In this thesis, three of the most commonly used transposons, piggyBac (PB), Tol2, and Sleeping Beauty (SB), were used for transgene delivery into CHO-DG44 cells. The transposon systems described here involves co-transfection of the host cells with a helper plasmid for the transient expression of the transposase, and a donor plasmid coding for the transgene and a gene for the selection, both positioned between two transposon repeat sequences that are required for DNA transposition. Through the optimization of various selection parameters we showed that PB-mediated cell pools can be generated with selection duration of as little as 5 days in the presence of puromycin. All three transposon systems, PB, Tol2, and SB, resulted in cell pools with similar volumetric TNFR:Fc productivities that were about 9 times higher than those generated by conventional plasmid transfection. Transposon-mediated cell pools had 10 - 12 transgene integrations per cell. However, we demonstrated that some the integration events occurred via DNA recombination rather than transposition. We also isolated clonal cell lines from cell pools. As expected, the average volumetric TNFR:Fc productivity of transposon-derived cell lines was higher than that of cell lines generated by conventional transfection. In 14-day fed-batch cultures, protein levels up to 900 mg/L and 1.5 g/L were obtained from transposon-mediated cell pools and cell lines, respectively. The stability over time of the volumetric productivity of cell pools was determined by maintaining the cells in culture for 3 months in the absence of selection. In general, the productivity decreased to 50 % its initial level over the first 7 weeks in culture and then remained constant for the following 5 weeks. In contrast, the volumetric protein yield from transposon-mediated cell lines remained constant for up to 4 months in the absence of selection. We also showed that the three transposon systems could be used for cell pool generation with CHO-K1 and CHO-S with similar volumetric productivities as observed with CHO-DG44 cells. Finally, we utilized the PB transposon system for generating cell pools co-expressing up to 4 different transgenes, enhanced green fluorescent protein (EGFP), secreted alkaline phosphatase (SEAP), and the light and heavy chains of an IgG1 monoclonal antibody, by simultaneous transfection of all four transgenes. We showed that PB-mediated cell pools had increased volumetric productivity of each of the proteins compared to those generated by conventional co-transfection. The use of the PB transposon system increased the percentage of cells in the pools that were co-expressing all four proteins as compared to the results with cell pools generated by conventional transfection. In conclusion, the transfection of CHO cells with the PB, Tol2 or SB transposon system is a simple, efficient, and reproducible approach to the generation of cell pools and cell lines for the rapid production of recombinant proteins.

EPFL2015

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Balancing GFP reporter plasmid quantity in large-scale transient transfections for recombinant anti-human Rhesus-D IgG1 synthesis

Horst Pick, Horst Vogel, Florian Maria Wurm

Using transient expression, high amounts (>20 mg/mL) of secreted anti-human Rhesus-D IgG1 were produced in a suspension-adapted HEK293 EBNA cell line (Meissner et al., Biotechnol Bioeng 75: 197-203, 2001). Time of harvest was 3 days after transfection. For the estimation of transfection efficiencies, we routinely co-transfected EGFP reporter DNA. At higher reporter plasmid concentrations, >2% of total transfecting plasmid DNA, a substantial reduction of recombinant antibody synthesis, was observed. This phenomenon was investigated in detail by co-expressing various green fluorescent protein (GFP) reporter constructs, which were targeted at different subcellular locations. Enhanced and humanized GFPs targeted to either the endoplasmic reticulum, the cytosol, or the nucleus reduced recombinant antibody production by 30 to 40% when present at higher concentrations in the transfection solution. The most severe effects were observed when the co-transfected EGFP was targeted to the endoplasmic reticulum, leading to a reduction of up to 80% in the presence of only 5% of reporter DNA. Interestingly, one nuclear-targeted GFP variant that was not codon optimized for expression in human cell lines could be added, to up to almost half of the total amount of transfecting DNA, without adverse effect on antibody production. Although the minimum amount of this reporter DNA needed for fluorescence reading was 10 times higher than for the other variants, it provided a much broader quantity range within which the transfection process could be studied without being negatively affected.

2002

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EPFL2015