Project description:Mycobacterium tuberculosis persists in the lungs of mammalian hosts despite inducing an immune response dominated by the macrophage-activating cytokine interferon-gamma (IFN-gamma). We identified the M. tuberculosis phosphate uptake system component PstA1 as a factor required to resist IFN-gamma dependent immunity. A ∆pstA1 mutant was fully virulent in IFN-gamma-/- mice but was attenuated in mice lacking the IFN-gamma-inducible nitric oxide synthase (NOS2). This phenotype suggests that ∆pstA1 bacteria are hypersensitive to an IFN-gamma-dependent immune mechanism(s) other than NOS2. In other species, the Pst system participates in phosphate-responsive gene regulation by interacting with a two-component signal transduction system. We identified genes that exhibited dysregulated expression in the ∆pstA1 mutant and showed that aberrant gene expression was dependent on the two-component system response regulator RegX3. Deletion of regX3 suppressed the replication and virulence defects of ∆pstA1 bacteria in NOS2-/- mice, suggesting that the ∆pstA1 mutant is attenuated, in part, due to aberrant RegX3-dependent gene expression. Our data imply that phosphate is an important signal controlling M. tuberculosis gene expression during replication in the lung. Aerobically growing logarithmic phase Wt or pstA1/regX3/pstA1regX3 mutant strains were grown in phosphate replete media and analyzed after several hours. Experiments were repeated in triplicate (pstA1 mutant) or quadruplicate (regX3/pstA1regX3 mutant).
Project description:Mycobacterium tuberculosis persists in the lungs of mammalian hosts despite inducing an immune response dominated by the macrophage-activating cytokine interferon-gamma (IFN-gamma). We identified the M. tuberculosis phosphate uptake system component PstA1 as a factor required to resist IFN-gamma dependent immunity. A ∆pstA1 mutant was fully virulent in IFN-gamma-/- mice but was attenuated in mice lacking the IFN-gamma-inducible nitric oxide synthase (NOS2). This phenotype suggests that ∆pstA1 bacteria are hypersensitive to an IFN-gamma-dependent immune mechanism(s) other than NOS2. In other species, the Pst system participates in phosphate-responsive gene regulation by interacting with a two-component signal transduction system. We identified genes that exhibited dysregulated expression in the ∆pstA1 mutant and showed that aberrant gene expression was dependent on the two-component system response regulator RegX3. Deletion of regX3 suppressed the replication and virulence defects of ∆pstA1 bacteria in NOS2-/- mice, suggesting that the ∆pstA1 mutant is attenuated, in part, due to aberrant RegX3-dependent gene expression. Our data imply that phosphate is an important signal controlling M. tuberculosis gene expression during replication in the lung.
Project description:Immunity to Mycobacterium tuberculosis in humans and in mice requires interferon gamma (IFNγ). Wheras IFNγ has been studied extensively for its effects on macrophages in tuberculosis, we determined that protective immunity to tuberculosis also requires IFNγ-responsive non-hematopoietic cells. Bone marrow chimeric mice with IFNγ-unresponsive lung epithelial and endothelial cells exhibited earlier mortality and higher bacterial burdens than control mice, under-expressed indoleamine-2,3-dioxygenase (Ido1) in lung endothelium and epithelium and over-expressed interleukin-17 (IL-17) with massive neutrophilic inflammation in the lungs. We also found that the products of IDO catabolism of tryptophan selectively inhibit IL-17 production by Th17 cells, by inhibiting the action of IL-23. These results reveal a previously-unsuspected role for IFNγ responsiveness in non-hematopoietic cells in regulation of immunity to M. tuberculosis, and reveal a mechanism for IDO inhibition of Th17 cell responses.
Project description:The Mycobacterium tuberculosis genome encodes two complete high-affinity Pst phosphate-specific transporters. We previously demonstrated that a membrane-spanning component of one Pst system, PstA1, was essential both for M. tuberculosis virulence and for regulation of gene expression in response to external phosphate availability. To determine if the alternative Pst system is similarly required for virulence or gene regulation, we constructed a deletion of pstA2. Transcriptome analysis revealed that PstA2 is not required for regulation of gene expression in phosphate-replete growth conditions. PstA2 was also dispensable for replication and virulence of M. tuberculosis in a mouse aerosol infection model. However, a ∆pstA1∆pstA2 double mutant was attenuated in mice lacking the cytokine interferon-gamma, suggesting that M. tuberculosis requires high-affinity phosphate transport to survive phosphate limitation encountered in the host. Surprisingly, ∆pstA2 bacteria were more resistant to acid stress in vitro. This phenotype is intrinsic to the alternative Pst transporter since a ∆pstS1 mutant exhibited similar acid resistance. Our data indicate that the two M. tuberculosis Pst transporters have distinct physiological functions, with the PstA1 transporter being specifically involved in phosphate sensing and gene regulation while the PstA2 transporter influences survival in acidic conditions.
Project description:The Mycobacterium tuberculosis genome encodes two complete high-affinity Pst phosphate-specific transporters. We previously demonstrated that a membrane-spanning component of one Pst system, PstA1, was essential both for M. tuberculosis virulence and for regulation of gene expression in response to external phosphate availability. To determine if the alternative Pst system is similarly required for virulence or gene regulation, we constructed a deletion of pstA2. Transcriptome analysis revealed that PstA2 is not required for regulation of gene expression in phosphate-replete growth conditions. PstA2 was also dispensable for replication and virulence of M. tuberculosis in a mouse aerosol infection model. However, a âpstA1âpstA2 double mutant was attenuated in mice lacking the cytokine interferon-gamma, suggesting that M. tuberculosis requires high-affinity phosphate transport to survive phosphate limitation encountered in the host. Surprisingly, âpstA2 bacteria were more resistant to acid stress in vitro. This phenotype is intrinsic to the alternative Pst transporter since a âpstS1 mutant exhibited similar acid resistance. Our data indicate that the two M. tuberculosis Pst transporters have distinct physiological functions, with the PstA1 transporter being specifically involved in phosphate sensing and gene regulation while the PstA2 transporter influences survival in acidic conditions. Aerobically growing logarithmic phase Wt or pstA2 mutant or pstA1A2 double mutant strains were grown in phosphate replete media and analyzed after several hours. Experiments were repeated in triplicate.
Project description:Immunity to Mycobacterium tuberculosis in humans and in mice requires interferon gamma (IFNγ). Wheras IFNγ has been studied extensively for its effects on macrophages in tuberculosis, we determined that protective immunity to tuberculosis also requires IFNγ-responsive non-hematopoietic cells. Bone marrow chimeric mice with IFNγ-unresponsive lung epithelial and endothelial cells exhibited earlier mortality and higher bacterial burdens than control mice, under-expressed indoleamine-2,3-dioxygenase (Ido1) in lung endothelium and epithelium and over-expressed interleukin-17 (IL-17) with massive neutrophilic inflammation in the lungs. We also found that the products of IDO catabolism of tryptophan selectively inhibit IL-17 production by Th17 cells, by inhibiting the action of IL-23. These results reveal a previously-unsuspected role for IFNγ responsiveness in non-hematopoietic cells in regulation of immunity to M. tuberculosis, and reveal a mechanism for IDO inhibition of Th17 cell responses. Bone marrow chimera were created by γ-irradiation (10 Gy) of recipient mice, Ifngr+/+ (W) or Ifngr-/- (K), and reconstitution by i.v. injection of Ifngr+/+ (W) bone marrow cells. After 6 weeks, the two groups of chimera Wâ??W and Wâ??K were infected via the aerosol route with 100 colony forming units of Mycobacterium tuberculosis strain H37Rv. At 63 days post-infection, 4 Wâ??W mice and 4 Wâ??K mice were euthanized, their lung left lobe removed and processed for total RNA isolation and microarray. The 4 samples from the Wâ??W mice were pooled together and used as control sample whereas the 4 samples from the Wâ??K mice were pooled together and used as experimental sample. The same harvest and sample processing was conducted on day 97 after infection, using 5 Wâ??W mice and 6 Wâ??K mice.
Project description:Infectious diseases, such as Mycobacterium tuberculosis (Mtb)-caused tuberculosis (TB), remain a global health threat exacerbated by increasing drug resistance. Host-directed therapy (HDT) is a complementing strategy for infection treatment through targeting host immune mechanisms. However, the limited understanding of the host factors and their regulatory mechanisms involved in host immune defense against infections has impeded HDT development. Here, we identify the E3 ubiquitin ligase tripartite motif-containing 27 (TRIM27) elicits host protective immunity against Mtb. Mechanistically, TRIM27 enters host cell nucleus upon Mtb infection to function as a transcription activator of transcription factor EB (TFEB). TRIM27 binds to TFEB promoter and the TFEB transcription factor cAMP responsive element binding protein 1 (CREB1), thus enhancing CREB1-TFEB promoter binding affinity and promoting CREB1 transcription activity towards TFEB, eventually leading to autophagy activation and pathogen clearance. Thus, TRIM27 contributes to host anti-Mtb immunity and targeting TRIM27/CREB1/TFEB axis serves as a promising HDT-based TB treatment.