Project description:Brucella dynamically engage macrophages while trafficking to an intracellular replicative niche as macrophages, the first line of innate host defense, attempt to eliminate organisms. Brucella melitensis, B. neotomae, and B. ovis are highly homologous, yet exhibit a range of host pathogenicity and specificity. RAW 264.7 macrophages infected with B. melitensis, and B. ovis exhibit divergent patterns of bacterial persistence and clearance; conversely, B. melitensis and B. neotomae exhibit similar patterns of infection. Evaluating early macrophage interaction with Brucella spp. allows discovery of host entry and intracellular translocation mechanisms, rather than bacterial replication. Microarray analysis of macrophage transcript levels following a 4 hr Brucella spp. infection revealed 130 probe sets altered compared to uninfected macrophages; specifically, 72 probe sets were increased and 58 probe sets were decreased with any Brucella spp. Interestingly, much of the inflammatory response was not regulated by the number of Brucella gaining intracellular entry, as macrophage transcript levels were often equivalent among B. melitensis, B. ovis, and B. neotomae infections. An additional 33 probe sets were identified with altered macrophage transcript levels among Brucella spp. infections that may correlate with species specific host defenses and intracellular survival. Gene ontological categorization unveiled genes altered among species are involved in cell growth and maintenance, response to external stimuli, transcription regulation, transporter activity, endopeptidase inhibitor activity and G-protein mediated signaling. Host transcript profiles provide a foundation to understand variations in Brucella spp. infections, while structure of the macrophage response and intracellular niche of Brucella spp. will be revealed through piecewise consideration of host signaling pathways. Keywords: Macrophage, intracellular pathogen, Brucella melitensis, Brucella neotomae, Brucella ovis, inflammatory immune response, species specificity
Project description:Brucella, a notorious intracellular pathogen, causes chronic infections in many mammals, including humans. The twin-arginine translocation (Tat) pathway transports folded proteins across the cytoplasmic membrane; protein substrates translocated by Brucella include ABC transporters, oxidoreductases, and cell envelope biosynthesis proteins. Previously, we showed that a Tat mutant of Brucella melitensis M28 exhibits reduced survival within murine macrophages. In this study, we compared the host responses elicited by wild-type M28 and its Tat-mutant strains ex vivo. We utilized label-free quantitative proteomics to assess proteomic changes in RAW264.7 macrophages after infection with M28 and its Tat mutants.
Project description:We used B. melitensis M5-90 wild type to construct gene-deleted strains of B. melitensis ∆per, RAW264.7 cells infected with B. melitensis M5-90 and B. melitensis M5-90 ∆per for 4h, respectively. miRNA microarray and mRNA array experiments were performed, qRT-PCR validation for miRNAs and mRNAs. We performed a joint analysis of differentially expressed miRNAs and mRNAs, and proved that the target gene of miRNA-146b is Tbc1d14. It further confirmed that miR-146b targeting tbc1d14 regulates brucella-mediated autophagy of RAW264.7 cells. Finally, the molecular mechanism of tbc1d14 influencing brucella-mediated autophagy of RAW264.7 cells was preliminarily revealed by DGE sequencing.
Project description:We used B. melitensis M5-90 wild type to construct gene-deleted strains of B. melitensis ∆per, RAW264.7 cells infected with B. melitensis M5-90 and B. melitensis M5-90 ∆per for 4h, respectively. miRNA microarray and mRNA array experiments were performed, qRT-PCR validation for miRNAs and mRNAs. We performed a joint analysis of differentially expressed miRNAs and mRNAs, and proved that the target gene of miRNA-146b is Tbc1d14. It further confirmed that miR-146b targeting tbc1d14 regulates brucella-mediated autophagy of RAW264.7 cells. Finally, the molecular mechanism of tbc1d14 influencing brucella-mediated autophagy of RAW264.7 cells was preliminarily revealed by DGE sequencing.
Project description:Facultative intracellular Brucella infect and survive inside macrophages, and the outcome of macrophage-Brucella interaction is a basis for establishment of a chronic Brucella infection. The majority of Brucella are killed at the early infection stage. A subpopulation of virulent Brucella strains is instead trafficked to an intracellular replicative phagosome, and are resistant to further attack and begin to multiply dramatically. Virulent Brucella also inhibit macrophage apoptosis that in turn favors pathogen survival and replication. We used the Affymetrix mouse GeneChip 430 2.0 array to analyze mouse macrophage gene expression profiles during the time course of virulent B. melitensis strain 16M infection. Experiment Overall Design: Murine J774.A1 macrophage cells were infected with B. melitensis strain 16M at a MOI of 200:1. Brucella cultures derived from different Brucella colonies were used to infect different groups of macrophage cells to reflect independent infections. Following 4 h incubation, the cells were washed with PBS and treated with 50 ug/ml gentamicin to kill extracellular Brucella. At 0 h (no Brucella infection), 4 h, 24 h, and 48 h post-infection, cells were individually collected, and total RNA was isolated. The Affymetrix mouse GeneChip 430 2.0 array was used for microarray hybridization. Microarray intensity data were obtained by using Affymetrix GCOS software and further analyzed by GeneSpring and other software programs.
Project description:Brucella ovis causes an important disease characterized by decreased fertility in rams, sporadic abortions in ewes and increased lamb mortality. The live attenuated B. melitensis Rev.1 vaccine is considered the best vaccine available against this infection. However, this vaccine shows variable protective efficacy ranging from 40% to 100%.The objective of this study was to identify possible correlates of protective response to B. ovis infection through the characterization by microarray hybridization and real-time RT-PCR of inflammatory and immune response genes upregulated in rams previously immunized with the B. melitensis Rev 1 vaccine strain and experimentally challenged with B. ovis. Gene expression profiles were compared before and after challenge with B. ovis between rams protected and those vaccinated but found infected after challenge. The genes upregulated in vaccinated and protected rams provide possible correlates of protective response to B. ovis infection in rams immunized with the B. melitensis Rev 1 vaccine.
Project description:Brucella ovis causes an important disease characterized by decreased fertility in rams, sporadic abortions in ewes and increased lamb mortality. The live attenuated B. melitensis Rev.1 vaccine is considered the best vaccine available against this infection. However, this vaccine shows variable protective efficacy ranging from 40% to 100%.The objective of this study was to identify possible correlates of protective response to B. ovis infection through the characterization by microarray hybridization and real-time RT-PCR of inflammatory and immune response genes upregulated in rams previously immunized with the B. melitensis Rev 1 vaccine strain and experimentally challenged with B. ovis. Gene expression profiles were compared before and after challenge with B. ovis between rams protected and those vaccinated but found infected after challenge. The genes upregulated in vaccinated and protected rams provide possible correlates of protective response to B. ovis infection in rams immunized with the B. melitensis Rev 1 vaccine. Gene expression profiles were compared before and after vaccination and challenge with B. ovis between rams protected with the B. melitensis Rev 1 vaccine strain and those vaccinated but infected after challenge. Total RNA was isolated from buffy coat samples before vaccination (T0), after vaccination and before challenge (T1) and 60 days post challenge (T2) using TriReagent (Sigma, St. Louis, MO, USA)
Project description:Using Solexa/Illumina's digital gene expression (DGE) system, a tag-based transcriptome sequencing method, we investigated the kinetic transcriptional profile of gene expression in macrophages infected with Brucella melitensis strain 16M. A key aspect of Brucella virulence is their ability to proliferate within professional and nonprofessional phagocytic host cells, thereby successfully bypassing the bactericidal effects of phagocytes. Their virulence and chronic infections are thought to be due to their ability to avoid the killing mechanisms within host cells. Defining the interaction between a host cell and Brucella is crucial to understanding the infectious process. Most researchers have studied the pathogens, but the host plays a very important role during infections. To date, relatively few host factors have been shown important in Brucella infections. However, little is known about the host networks that mediate infection. The objective of the study is to analyze the genes and cellular components related to the innate immunity response to determine the mechanisms through which Brucella avoids the host innate immunity. A total of 3576 and 3962 genes that are differentially expressed between 0 and 4 h and between 0 and 24 h were identified. The identified genes are related to immune processes, signal transduction, inflammation, apoptosis, cell membrane, transcriptional regulation, and intracellular trafficking. Our data have added to the current understanding of different host gene expressions during different infection phases by Brucella spp. The RAW264.7 cells were seeded into 24-well plates at 5-105 cells/well, incubated in 5% CO2 at 37 M-BM-0C for 24 h, and then infected with Brucella at a multiplicity of infection of 200. To synchronize the infection, the infected plates were centrifuged at 200 ug for 5 min at room temperature and then incubated at 37 M-BM-0C for 20 minutes. The infected cell monolayers were washed three times with PBS, overlaid with 0.5 ml of DMEM containing 100 mg/ml of ampicillin and 50 mg/ml of kanamycin at 37 M-BM-0C for 0, 4, and 24 h. At the end of the incubation period, the culture medium was removed and centrifuged at 1500 rpm for 15 min. The cell pellet and adherent cells were resuspended in TRIzol. Total RNA were extracted from the cells at 0, 4 and 24 h post infection.