HOST-SPECIFIC GENE EXPRESSION BY EHRLICHIA CHAFFEENSIS

Jeeba Kuriakose B.S.¹, S. Miyashiro M.P.H.^1,3, T. Luo Ph.D.¹, J.W. McBride Ph.D.^1,2

¹Departments of Pathology and ²Microbiology and Immunology, UTMB; ³Biologic Institute, São Paulo, Brazil

Background: The natural life cycle of Ehrlichia chaffeensis, an obligatory intracellular bacterium that causes life-threatening human monocytotropic ehrlichiosis, consists of alternate infection of two distinct hosts, ticks and mammals. However, little is known about the host-pathogen-associated genes involved in the adaptation and survival of E. chaffeensis within these distinct hosts. We hypothesize that E. chaffeensis expresses a subset of genes with tandem repeats (TR) in the vertebrate host that are not expressed in the invertebrate host. Objective: to examine expression of E. chaffeensis genes in tick and mammalian cells. Methods: Gene expression levels were examined at the RNA level by quantitative real-time RT-PCR and at the protein level by immunofluorescence assay and Western immunoblotting with protein specific antibodies. Results: genes with TRs expressed by E. chaffeensis cultivated in mammalian cells are not expressed by E. chaffeensis cultivated in tick cells. In addition, E. chaffeensis genes; thio-disulfide oxidoreductase (dsb), RNA polymerase sigma factor (rpoD), type IV secretion system protein (VirB4) and outer membrane protein (Omp 1B) were expressed in mammalian cells and not in tick cells. Among the genes expressed by E. chaffeensis cultivated in both tick cells and mammalian cells are OmpA family genes. These results indicate that E. chaffeensis genes are differentially expressed depending on the host environment. Supported by the National Institutes of Health RO1#A1071145-01.