Abstract EN:

The obligatory intracellular bacterium Ehrlichia ruminantium (ER) is a pathogen responsible for heartwater wich affects in wild and domestic ruminants. To elucidate the pathogenesis of ER in endothelial cells, a high throughput analysis of its transcriptome was done. A comparison of gene expression between two sequenced strains was done: Gardel virulent and attenuated. Selective capture of ER transcribed sequences was done using the SCOTS method which has been adapted to our model. The cDNA were hybridized on pangenomic ER microarrays specific of both Gardel and Welgevonden strains. 239 genes were identified to be differentially expressed between virulent and attenuated Gardel strains in host cells within the three developmental stages studied. 116 genes were detected at the late stage corresponding to free elementary bodies. Among overexpressed genes identified for virulent strain, sorne genes have been described previously in other intracellular bacteria (R. Conorii) to be involved in the host cell immune response escape. They were mainly involved in DNA repair (helicase, Iigase), diminution of the oxidatif (thioredoxine) and osmotic stress, the inhibition of endosome fusion (SNARE) and diminution of apoptosis (Ank A). Sorne interesting genes over-expressed for attenuated strain could induce a protective immune response. Genomic and transcriptomic comparison of data from both strains allowed identification of several cluster of genes potentially co-regulated such as the cluster recB. The qRTPCR validation of differential gene expression identified by microarrays is currently done. In parallel, ER proteomic analysis 1 paves the way for further functional analysis.