Study On Coxiella Burnetii Interaction With Monocytes

Coxiella bumetii is an obligate intracellular, Gram-negative bacterium that replicates within the phagolysosome of the phagocytes. It is the etiological agent of the "Q fever" which is highly infectious to both humans and livestock. Macrophage is the key host cell for C. bumetii. The aim of this study is to use state-of-art proteomic method to study on C. bumetii interaction with host cells, monocytes, in order to understand its pathogenic mechanism, which will provide useful knowledge for finding new drug targets and designing new type vaccines against C. bumetii.The organisms of C. bumetii were interacted with the human monocytes (THP-1) cultured in vitro and the regular patterns of monocytes to intake the organisms and the organisms to grow in monocytes were investigated. The results showed that the efficiency of monocyte to intake the live organisms of C. bumetii was significantly lower than that to intake the organisms inactivated with y -ray. The number of live organisms increased gradually from the forth day in monocytes; however, the number of inactivated organisms decreased quickly after the first day and they were almost undetectable on the fifth day.The total proteins of monocytes infected with C. bumetii collected on hour 4 after infection and monocytes without infection were analyzed 2-dimensional electrophoresis, respectively; 97 of 158 different protein spots found by the software analysis were identified by mass spectrometry analysis. These proteins were functioned in energy metabolism, syntheses of protein and nucleic acid, reorganization of the actin cytoskeleton, and inhibition of cell apoptosis. The data suggest that the up-regulation or down-regulation of the proteins identified in the monocytes infected with C. bumetii may be beneficial to growth and propagation of the pathogen in monocytes.The total protein of C. bumetii purified were separated by 2-dimensional electrophoresis and analyzed by immunoblot assay. By immunoblot assay, 2, 8, 18, and 94 positive spots were found with sera collected from mice infected with C. bumetii on days 5, 10, 20, and 30 after infection, respectively. However, only 13 immunoreactive proteins were identified by mass spectrometry. The dynamic changes of immunoreactive proteins and the new immunoreactive proteins of C. bumetii may be the new targets for studying of diagnosis and vaccine of Q fever...