Analysis of Qa-1bPeptide Binding Specificity and the Capacity of Cd94/Nkg2a to Discriminate between Qa-1–Peptide Complexes

The major histocompatibility complex class Ib protein, Qa-1b, serves as a ligand for murine CD94/NKG2A natural killer (NK) cell inhibitory receptors. The Qa-1b peptide-binding site is predominantly occupied by a single nonameric peptide, Qa-1 determinant modifier (Qdm), derived from the leader sequence of H-2D and L molecules. Five anchor residues were identified in this study by measuring the peptide-binding affinities of substituted Qdm peptides in experiments with purified recombinant Qa-1b. A candidate peptide-binding motif was determined by sequence analysis of peptides eluted from Qa-1 that had been folded in the presence of random peptide libraries or pools of Qdm derivatives randomized at specific anchor positions. The results indicate that Qa-1b can bind a diverse repertoire of peptides but that Qdm has an optimal primary structure for binding Qa-1b. Flow cytometry experiments with Qa-1b tetramers and NK target cell lysis assays demonstrated that CD94/NKG2A discriminates between Qa-1b complexes containing peptides with substitutions at nonanchor positions P4, P5, or P8. Our findings suggest that it may be difficult for viruses to generate decoy peptides that mimic Qdm and raise the possibility that competitive replacement of Qdm with other peptides may provide a novel mechanism for activation of NK cells

A novel category of antigens enabling CTL immunity to tumor escape variants: Cinderella antigens

Deficiencies in MHC class I antigen presentation are a common feature of tumors and allows escape from cytotoxic T lymphocyte (CTL)-mediated killing. It is crucial to take this capacity of tumors into account for the development of T-cell-based immunotherapy, as it may strongly impair their effectiveness. A variety of escape mechanisms has been described thus far, but progress in counteracting them is poor. Here we review a novel strategy to target malignancies with defects in the antigenic processing machinery (APM). The concept is based on a unique category of CD8+ T-cell epitopes that is associated with impaired peptide processing, which we named TEIPP. We characterized this alternative peptide repertoire emerging in MHC-I on tumors lacking classical antigen processing due to defects in the peptide transporter TAP (transporter associated with peptide processing). These TEIPPs exemplify interesting parallels with the folktale figure Cinderella: they are oppressed and neglected by a stepmother (like functional TAP prevents TEIPP presentation), until the suppression is released and Cinderella/TEIPP achieves unexpected recognition. TEIPP-specific CTLs and their cognate peptide-epitopes provide a new strategy to counteract immune evasion by APM defects and bear potential to targeting escape variants observed in a wide range of cancers

Interest of electrodialysis to reduce potassium level in vinasses. Preliminary experiments

Correspondance: [email protected] audienceNowadays, treatment of vinasse from the alcohol fermentation is a major cost centre which decides the economic viability of this traditional industry. Increasingly stringent environment norms in France have put enormous pressure on manufacturers of alcohol from traditional feedstock like beet molasses. Nowadays, the most industrial treatment is the vinasse valorisation as fertiliser in the field after concentration. Nevertheless, the final solids are limited because of the sulphate potassium crystallisation and precipitation in evaporator tubes, storage tanks and fertiliser sprayers. The paper gives some figures of beet molasses vinasse composition, details the most widely used treatment schemes and presents the first results obtained with an electrodialysis treatment to reduce the potassium concentration in view to prevent the crystallisation and even increase the final dissolved solids of the concentrated vinass

Traitement et valorisation des vinasses: problématique et synthèse des voies de valorisation étudiées et envisagées

Correspondance: [email protected] audienceLes vinasses sont des effluents à forte charge organique qui nécessitent obligatoirement un traitement dépendant de la matière première fermentée. Les vinasses de mélasse de betterave sont valorisées comme engrais après concentration avec parfois une dépotassification, mais les condensats chargés en DCO (3-5 g/L) doivent traités biologiquement. Dans les DOM, les vinasses de jus de canne sont épandues ou rejetées en mer, les vinasses de mélasse sont, elles, envoyées dans un forage ou rejetées en mer. Les vinasses de lies de vin sont détartrées puis traitées de manière biologique en méthaniseur ou en lagune avec aération ou non, ou concentrées avant épandage.L’épandage fait l’objet de normes de plus en plus strictes et les usines s’orientent souvent maintenant vers la méthanisation couplée à un traitement aérobie. A côté de ces procédés, la séparation de molécules intéressantes, notamment le glycérol, la tétaïne et des acides organiques, ou la production de ces molécules à partir de vinasses sont à l’étud

Les composés d'arôme du rhum traditionnel blanc : nature, propriétés sensorielles et voies de formation

National audienceWhite traditional rum is produced from cane molasses fermentation followed by distillation of the broth. Rum's organoleptic properties depend on concentration of aromatic compounds. The present bibliography synthesis aims to classify the aromatic compounds of white traditional rum then to precise their sensorial impact and their origin. Compounds are presented according to their chemical family: alcohols, carbonyl compounds (aldehydes, cetones, acetals), acids, esters and "minor compounds" including compounds at very low concentration but with a sensorial impact (sulphur compounds, derives from isoprenoids, pyrazines, lactone, phenolic compounds).Le rhum traditionnel blanc est issu de la fermentation de la mélasse de canne à sucre puis de la distillation du moût fermenté. Les propriétés sensorielles du rhum sont liées à la présence des composés d'arômes et à leur concentration. La synthèse bibliographique présentée ici vise à classifier les composés présents dans le rhum traditionnel blanc puis à préciser leur impact sensoriel et leur origine. Les composés sont présentés par famille chimique : les alcools, les composés carbonylés (aldéhydes, cétones, acétals), les acides, les esters et les "composés minoritaires" regroupant des composés ayant un impact sensoriel significatif malgré leur très faible concentration (composés soufrés, dérivés des isoprénoïdes, pyrazines, lactones, composés phénoliques)

Mutant bias in nonlethal selections results from selective recovery of mutants.

Abstract We have characterized a nonlethal selection for mutations that allow Escherichia coli to grow on large maltodextrins (Dex+) in the absence of the lamB encoded maltoporin LamB. These Dex+ mutations occur before and after imposition of the selection and the selection does not result in a general increase in mutagenesis. The recovered Dex+ mutations are almost exclusively mutations that alter the ompF gene that encodes a major E. coli porin, OmpF even though analogous mutations in the homologous ompC gene, which encodes the OmpC porin, can confer a Dex+ phenotype. We show that the bias for ompF mutations results from a biased recovery and that the genetic background of the starting strain and the selection itself influences the type of mutants that are recovered. When we use a strain carrying an amber mutation in the lamB gene we observe the same preference for ompF mutations as when we start with a lamB deletion strain. In addition, we show that there is no preferential mutagenesis of the lamB gene during the selection which induces transcription of the lamB gene. We present evidence that the biased recovery of mutants observed in this selection does not result from adaptive or directed mutagenesis and that the phenotypic fitness which allows recovery of Dex+ mutants involves more than the increased ability to take up maltodextrins.</jats:p