title: Transmission of Anaplasma phagocytophilum from endothelial cells to peripheral granulocytes in vitro under shear flow conditions.
abstract: Anaplasma phagocytophilum (Ap) is a tick-borne pathogen, which can cause granulocytic anaplasmosis in humans and animals. In vivo this obligate intracellular pathogen is primarily located in circulating mature granulocytes, but it also infects endothelial cells. In order to study the interaction between Ap-infected endothelial cells and human granulocytes under conditions similar to those found naturally in the infected host, an in vitro model that mimics physiological flow conditions in the microvasculature was established. Cell-to-cell interactions were then visualized by microscopy, which showed that granulocytes adhered strongly to Ap-infected endothelial cells at a shear stress of 0.5 dyne/cm(2). In addition, Ap-transmission assays under flow conditions showed that the bacteria transferred from infected endothelial cells to circulating granulocytes and were able to establish infection in constantly moving granulocytes. Cell surface analysis showed that Ap induced up-regulation of the cell adhesion molecules ICAM-1 and VCAM-1 on infected endothelial cells in a dose-dependent manner. Furthermore, IL-8 secretion by endothelial cells indicated that the presence of Ap induced a pro-inflammatory response. In summary, the results of this study suggest that endothelial cells of the microvasculature (1) provide an excellent site for Ap dissemination to peripheral blood granulocytes under flow conditions and therefore may play a crucial role in the development of persistent infection, and (2) are stimulated by Ap to express surface molecules and cytokines that may lead to inflammatory responses at the site of the infection.
authors.affiliation: Institute for Infectious Diseases and Zoonoses, Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU Munich, Veterinärstr. 13, 80539, Munich, Germany.
authors.forename: Jinyong
authors.initials: J
authors.lastname: Wang
authors.forename: Viktor
authors.initials: V
authors.lastname: Dyachenko
authors.forename: Ulrike G
authors.initials: UG
authors.lastname: Munderloh
authors.forename: Reinhard K
authors.initials: RK
authors.lastname: Straubinger
mesh_terms: D041081:Anaplasma phagocytophilum / Q000302:isolation & purification* / Q000502:physiology*; D002448:Cell Adhesion; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000737:chemistry / Q000382:microbiology*; D006098:Granulocytes / Q000382:microbiology*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D008853:Microscopy; D008954:Models, Biological; D019010:Vascular Cell Adhesion Molecule-1 / Q000032:analysis
chemical_list: D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1