RESUMEN
Brucella is an intracellular pathogen able to persist for long periods of time within the host and establish a chronic disease. We show that soon after Brucella inoculation in intestinal loops, dendritic cells from ileal Peyer's patches become infected and constitute a cell target for this pathogen. In vitro, we found that Brucella replicates within dendritic cells and hinders their functional activation. In addition, we identified a new Brucella protein Btp1, which down-modulates maturation of infected dendritic cells by interfering with the TLR2 signaling pathway. These results show that intracellular Brucella is able to control dendritic cell function, which may have important consequences in the development of chronic brucellosis.
Asunto(s)
Brucella abortus/patogenicidad , Brucelosis/microbiología , Células Dendríticas/microbiología , Interacciones Huésped-Patógeno , Receptor Toll-Like 2/metabolismo , Animales , Brucella abortus/crecimiento & desarrollo , Brucella abortus/inmunología , Brucelosis/inmunología , Brucelosis/patología , Supervivencia Celular , Células Cultivadas , Citocinas/metabolismo , Células Dendríticas/inmunología , Células Dendríticas/metabolismo , Modelos Animales de Enfermedad , Regulación hacia Abajo , Íleon/microbiología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ganglios Linfáticos Agregados/microbiologíaRESUMEN
The lipopolysaccharides (LPS) of intracellular Proteobacteria such as Brucella, Chlamydia, Legionella and Rickettsia, have properties distinct from enterobacterial LPSs. These properties include deficient LPS induction of host cell activation, low endotoxicity and resistance to macrophage degradation. Together these constitute key virulence mechanisms for intracellular survival and replication. We previously demonstrated that B. abortus LPS captured by macrophages was recycled back to the plasma membrane where it was found associated with macrodomains. Furthermore, this LPS interferes with the MHC class II (MHC-II) presentation of peptides to specific T cell hybridomas. Here, we characterized the Brucella LPS macrodomains by microscopy and biochemistry approaches. We show for the first time that LPS macrodomains act as detergent resistant membranes (DRMs), segregating several lipid-raft components, LPS-binding proteins and MHC-II molecules. Brucella LPS macrodomains remain intact for several months in macrophages and are resistant to the disruptive effects of methyl beta-cyclodextrin. Fluorescent anisotropy measurements show that B. abortus LPS is responsible for the formation of rigid surface membrane complexes. In addition, relocalization of MHC-II molecules is observed in these structures. The effects of B. abortus LPS on membrane properties could be responsible for pathogenic effects such as the inhibition of MHC-II-dependent antigen presentation.