Molecular Pathogenesis of Ehrlichia chaffeensis Infection.
Ehrlichia chaffeensis is an obligatory intracellular and cholesterol-dependent bacterium that has evolved special proteins and functions to proliferate inside leukocytes and cause disease. E. chaffeensis has a multigene family of major outer membrane proteins with porin activity and induces infectious entry using its entry-triggering protein to bind the human cell surface protein DNase X. During intracellular replication, three functional pairs of two-component systems are sequentially expressed to regulate metabolism, aggregation, and the development of stress-resistance traits for transmission. A type IV secretion effector of E. chaffeensis blocks mitochondrion-mediated host cell apoptosis. Several type I secretion proteins are secreted at the Ehrlichia-host interface. E. chaffeensis strains induce strikingly variable inflammation in mice. The central role of MyD88, but not Toll-like receptors, suggests that Ehrlichia species have unique inflammatory molecules. A recent report about transient targeted mutagenesis and random transposon mutagenesis suggests that stable targeted knockouts may become feasible in Ehrlichia.
Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210; email: rikihisa.1@osu.edu.
Yasuko
Y
Rikihisa
D000818:Animals; D018469:Ehrlichia chaffeensis / Q000502:physiology*; D016873:Ehrlichiosis / Q000276:immunology* / Q000382:microbiology* / Q000473:pathology; D006801:Humans; D007249:Inflammation; D007962:Leukocytes / Q000382:microbiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D000069319:Type IV Secretion Systems
D017382:Reactive Oxygen Species; D000069319:Type IV Secretion Systems
MyD88; adhesin; chemokines; cytokines; invasin; outer membrane proteins; receptor for entry; two-component system; type I and IV secretion systems