Project description:Underdiagnosis of fatal spotted fever may be attributed to nonspecific clinical features and insensitive acute-phase serologic studies. We describe the importance of molecular and immunohistochemical methods in establishing the postmortem diagnosis of locally acquired Israeli spotted fever due to Rickettsia conorii subsp. israelensis in a traveler returning to Israel from India.
Project description:Rickettsia conorii is the etiologic agent of Mediterranean spotted fever, a re-emerging disease with significant mortality. This obligate, gram-negative intracellular pathogen is transmitted via tick bites, resulting in disseminated vascular endothelial cell infection with vascular leakage. In the infected human, Rickettsia conorii infects endothelial cells, stimulating expression of cytokines and pro-coagulant factors. However, the integrated proteomic response of human endothelial cells to R. conorii infection is not known. In this study, we performed quantitative proteomic profiling of R conorii –infected primary HUVECs vs those stimulated with LPS alone.
Project description:Rickettsia conorii are obligate intracellular bacteria responsible for the Mediterranean spotted fever. Their adaptation to highly divergent environments ranging from the arthropod vector to the human beings is essential to survival and virulence. Through a combination of total RNA purification and random prokaryotic cDNA amplification, we successfully analyzed transcription profiles by microarrays starting from 100 ng of R. conorii RNA. Real-time quantitative PCR results performed on unpurified total RNA was consistent with microarray measurements. Here, from the selected targets spotted on our microarray, we showed that in R. conorii, nutrient stress is accompanied by over-expression of the virB operon. Regulation of these genes could be mediated by the stringent response through ppGpp, consistent with the observed up-regulation of spoT and gmk. Exposure of R. conorii to a nutrient stress paradoxically reduced the expression of both GroEL and its transcriptional regulator RpoH. This shows that the over-expression of this chaperonin is a part of the natural life of intracellular growing rickettsiae. Our findings also evidenced that, unexpectedly, many atypical sequences, including small-size split genes, ORFans genes and highly conserved intergenic regions contains expressed sequences that are differentially regulated. The notable deficiency of transcriptional regulators within R. conorii genome does not reflect its incapability to undergo transcriptional changes but rather the existence of an alternative adaptation strategy. Keywords: Global transcriptional analysis