Study Of Cytokine Pattern Induced By Intracelullar Survival Of Bartonellain Macrophage

Bartonella is arthropod-born, Gram-negative, oxidase negative andfastidious small intracellular parasitic bacterium, which can causelong-lasting infection in host cells, such as endothelial cells, epithelial cells,etc. Bartonella, formerly known as Rochalimaea, has been moved into-proteobacteria. Hitherto, there are24species and3subspecies inBartonellaceae, with forteen species have been confirmed to associate withhuman infections. Bartonella can cause Cat-Scratch disease and bacillaryangiomatosis in humans. Histopathological studies found lots of freeBartonella bacilli in infected lymph nodes, which indicated that Bartonellawas able to escape from host innate immunity or phagocytosis. However, theinteraction between Bartonella and macrophage has not been welldemonstrated. To better understand the interaction of Bartonella and macrophage, weused Bartonella tribocorum, a murine origin pathogen, to infect J774A1,RAW264.7and SD rat peritoneal macrophages in vitro. The aim of this studyis to explore the intracellular survival of Bartonella in macrophages and thecytokine pattern of macrophages induced by Bartonella infection.1、Explore Bartonella survival in different macrophagesThe extracellular and intracellular bacterium was differentiated by usingDylight405conjugated goat anti-rabbit IgG secondary antibody andDylight488conjugated goat anti-rabbit IgG secondary antibody respectively.Results showed that Bartonella can be phagocytosed in macrophageseffectively, without showing any obvious morphological changes.The intracellular survival of Bartonella tribocorum in J774A1、RAW267.4,and rat peritoneal macrophage was investigated by using gentamycinprotection assay. Results demonstrated that Bartonella can replicate andsurvive at least in48hours post infection in all macrophages. Moreover,LPS-activated macrophage also failed to clear the intracellular bacteria,which indicated Bartonella can escape or inhibit bactericidal effect ofmacrophages.2、Cytokine pattern in macrophages induced by Bartonella infectionIn this study, cytokines in rat peritoneal macrophages infected with Bartonella was detected by real-time PCR. Results showed that IL-10waselevated significantly in macrophage infected with live Bartonella (referringto the cells infected with inactive bacteria or mock infection). However,IL-1β, a cytokine caused by inflammasome activation was decreased in liveBartonella infected cells. This indicated that Bartonlla infection activate themacrophages from canonical M1macrophage to non-canonical M2macrophages, which might facilitate the intracellular survival of Bartonellain macrophages.