BackgroundHuman African trypanosomiasis is a lethal disease caused by the extracellular parasite Trypanosoma brucei. The proteins secreted by T. brucei inhibit the maturation of dendritic cells and their ability to induce lymphocytic allogenic responses. To better understand the pathogenic process, we combined different approaches to characterize these secreted proteins.ResultsOverall, 444 proteins were identified using mass spectrometry, the largest parasite secretome described to date. Functional analysis of these proteins revealed a strong bias toward folding and degradation processes and to a lesser extent toward nucleotide metabolism. These features were shared by different strains of T. brucei, but distinguished the secretome from published T. brucei whole proteome or glycosome. In addition, several proteins had not been previously described in Trypanosoma and some constitute novel potential therapeutic targets or diagnostic markers. Interestingly, a high proportion of these secreted proteins are known to have alternative roles once secreted. Furthermore, bioinformatic analysis showed that a significant proportion of proteins in the secretome lack transit peptide and are probably not secreted through the classical sorting pathway. Membrane vesicles from secretion buffer and infested rat serum were purified on sucrose gradient and electron microscopy pictures have shown 50- to 100-nm vesicles budding from the coated plasma membrane. Mass spectrometry confirmed the presence of Trypanosoma proteins in these microvesicles, showing that an active exocytosis might occur beyond the flagellar pocket.ConclusionsThis study brings out several unexpected features of the secreted proteins and opens novel perspectives concerning the survival strategy of Trypanosoma as well as possible ways to control the disease. In addition, concordant lines of evidence support the original hypothesis of the involvement of microvesicle-like bodies in the survival strategy allowing Trypanosoma to exchange proteins at least between parasites and/or to manipulate the host immune system.

Résumé -Spectroscopie infrarouge en réflexion diffuse (DRIFTS) : application à l'analyse in situ de catalyseurs -La technique infrarouge de spectroscopie de réflexion diffuse (DRIFTS), moins pratiquée que la transmission en raison de ses limitations, est extrêmement utile, en effet indispensable, pour les matériaux non transparents et/ou pour des mesures in situ à la température élevée. Les auteurs décrivent les principes de cette technique et ses avantages par rapport à la spectroscopie infrarouge en transmission. L'application de DRIFTS à la caractérisation des catalyseurs est illustrée par deux études : sur l'interaction du molybdène avec le précurseur de catalyseurs de désulfuration de carburant, et sur les modifications in situ sous gaz réactifs des catalyseurs de réduction des composés azotés dans les gaz d'échappement. Abstract -Diffuse Reflection Infrared Spectroscopy (DRIFTS): Application to the in situ Analysis of Catalysts -The diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) technique, less practiced than the transmission mode because of its limitations, is extremely useful, indeed indispensable, for non-transparent materials and/or for in situ measurements at elevated temperature. The authors describe the principles of this technique and its advantages over transmission infrared spectroscopy. The application of DRIFTS to the characterization of catalysts is illustrated by two studies conducted on the interaction of molybdenum with the precursor of fuel desulphurization catalysts, and on the in situ modifications under reactive gases of catalysts for reducing nitrogen compounds in exhaust gases.

No abstract

No abstract