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Mycobacterium tuberculosis Requires Phosphate-Responsive Gene Regulation to Resist Host Immunity

ABSTRACT: 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.

ORGANISM(S): Mycobacterium tuberculosis H37Rv Mycobacterium tuberculosis str. Erdman = ATCC 35801 Mycobacterium tuberculosis CDC1551

PROVIDER: GSE36998 | GEO | 2013/01/01

SECONDARY ACCESSION(S): PRJNA158489

REPOSITORIES: GEO

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Project description:Background: Conflicting results have been reported about the role of the two-component sensor and transcriptional regulator DosS/DosR, controlling the expression of the dormancy DosR regulon, for in vivo virulence of M. tuberculosis. Here, we have used a new approach to further analyze the relevance of the dosRS system, by driving DosR (Rv3133c) expression under the control of a constitutive promoter (phsp60). Methodology/Principal Findings: M. tuberculosis H37Rv constitutively expressing the transcriptional regulator DosR (Mtb::DosR) was compared to wild type M. tuberculosis (Mtb+/+) for in vitro growth kinetics and expression of the target genes of the DosR dormancy regulon, for in vivo virulence and for immunogenicity in mice. Under aerobic conditions, hsp60-driven DosR induced the expression of 28 out of 39 tested DosR regulon genes. In vitro growth characteristics were comparable for both strains, but Mtb::DosR showed an attenuated in vivo phenotype in immunocompetent mice, as indicated by reduced bacterial replication, reduced pulmonary immunopathology, reduced cachexia and significantly prolonged survival time as compared Mtb+/+. In immunodeficient SCID mice, Mtb::DosR was fully virulent. RT-qPCR analysis revealed a strong and comparable pulmonary TNF-?? and IL-23 expression following intratracheal infection, whereas IL-12 and IL-17 expression was slightly higher with wild type Mtb+/+. Finally, mice persistently infected with Mtb::DosR for 8 months showed five to tenfold higher lung IFN-?? responses against ten of the 48 DosR regulon encoded antigens (Rv1733c, Rv1734, Rv1738, Rv1996, Rv1997, Rv2029c, Rv2623, Rv2627c, Rv2628 and Rv3127) than mice actively infected with Mtb+/+. In spleen however, DosR regulon encoded antigen specific IFN-?? responses were similar in both groups. Conclusions/Significance. Collectively, these results suggest that increased DosR regulon encoded antigen specific pulmonary T cell responses are responsible for the attenuated phenotype of Mtb::DosR and that infection with Mtb::DosR could be used as a new animal model for studying key aspects of latent tuberculosis. Set of arrays that are part of repeated experiments

Project description:Tuberculosis results from an interaction between a chronically persistent pathogen counteracted by IFN-g-mediated immune responses. Modulation of IFN-g signaling could therefore constitute a major immune evasion mechanism for M. tuberculosis. SOCS1 plays a major role in the inhibition of IFN-g-mediated responses. We found that M. tuberculosis infection stimulates SOCS1 expression in mouse and human myeloid cells. Significantly higher levels of SOCS1 were induced after in vitro or in vivo infection with virulent M. tuberculosis-than with attenuated M. bovis BCG. Different innate and adaptive immune mechanisms participated in infection-induced SOCS1 expression. SOCS1 hampered M. tuberculosis clearance both in macrophages and during murine infection in vivo. On the other hand, SOCS1 protected the host from an infection-induced inflammation. Despite SOCS1 expression, mycobacteria-infected macrophages were not tolerant to IFN-g. Instead, an impaired IFN-g secretion by macrophages, associated to lower responses to IL-12, accounted for the increased mycobacterial intracellular growth in presence of SOCS1. SOCS1 attenuated the expression of the majority of genes modulated by infection of macrophages (6,1% of the transcriptome), indicating the relevance of the molecule in the outcome of infection with M. tuberculosis. We suggest that SOCS1 is expressed during M. tuberculosis infection to establish a successful chronic infection, and dampen inflammatory damage. Difference in genotype and TB infection comparison Relative gene expressions were determined by normalized intensity values. GeneSpring analysis was performed using the Treg transcriptome data with following comparisons: no GvHD d90 versus no GvHD d150, no GvHD d90 versus acute GvHD, no GvHD d150 versus chronic GvHD, acute GvHD versus chronic GvHD, acute GvHD versus GvHD d90 and chronic GvHD versus GvHD d150 (Figure 2). Cut-off was a transcript fold change of +2 or -2 in at least one comparison. Student´s t-test was used to identify significant expression changes.

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Mycobacterium tuberculosis Requires Phosphate-Responsive Gene Regulation to Resist Host Immunity

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