Single-cell profiling identifies ACE+ granuloma macrophages as a non-permissive niche for intracellular bacteria during persistent Salmonella infection
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ABSTRACT: Macrophages mediate key antimicrobial responses against intracellular bacterial pathogens, such as Salmonella enterica. Yet, they can also act as a permissive niche for these pathogens to persist in infected tissues within granulomas, which are immunological structures comprised of macrophages and other immune cells. We apply single-cell transcriptomics to investigate macrophage functional diversity during persistent Salmonella enterica serovar Typhimurium (STm) infection in mice. We identify determinants of macrophage heterogeneity in infected spleens and describe populations of distinct phenotypes, functional programming, and spatial localization. Using a STm mutant with impaired ability to polarize macrophage phenotypes, we find that angiotensin converting enzyme (ACE) defines a granuloma macrophage population that is non-permissive for intracellular bacteria and their abundance anticorrelates with tissue bacterial burden. Disruption of pathogen control by neutralizing TNF is linked to preferential depletion of ACE+ macrophages in infected tissues. Thus ACE+ macrophages have limited capacity to serve as cellular niche for intracellular bacteria to establish persistent infection.
Project description:To investigate the extent to which macrophages respond to Salmonella infection, researchers infected RAW 264.7 macrophages with Salmonella enterica serotype Typhimurium and analyzed macrophage proteins at various time points following infection by using a global proteomic approach.
Project description:Intracellular bacterial pathogens can exhibit large heterogeneity in growth rate inside host cells with major consequences for the infection outcome. If and how the host responds to this heterogeneity remains poorly understood. Here, we combined a fluorescent reporter of bacterial cell division with single-cell RNA-seq analysis to study the macrophage response to different intracellular states of the model pathogen Salmonella enterica serovar Typhimurium. The transcriptomes of individual infected macrophages revealed a spectrum of functional host response states to dividing and non-dividing bacteria. Intriguingly, macrophages harboring non-dividing Salmonella display hallmarks of the pro-inflammatory M1 polarization state and differ little from bystander cells, suggesting that non-dividing bacteria evade recognition by intracellular immune receptors. By contrast, macrophages containing dividing bacteria have turned into an anti-inflammatory, M2-like state, as if fast-growing intracellular Salmonella overcome host defense by reprogramming macrophage polarization. Additionally, our clustering approach reveals intermediate host functional states between these extremes. Altogether our data suggest that gene expression variability in infected host cells shapes different cellular environments, some of which may favor a growth arrest of Salmonella facilitating immune evasion and the establishment of a long-term niche; while others allow Salmonella to escape intracellular antimicrobial activity and proliferate.
Project description:SrfJ is an effector of the type III secretion systems of the Gram-negative intracellular pathogen Salmonella enterica serovar Typhimurium. To study the effects of this effector on global gene expression in host cells, we have infected murine RAW264.7 macrophages with two strains of Salmonella enterica serovar Typhimurium. The comparison between cells infected with the wild-type strain and cells infected with a srfJ mutant revealed a number of genes that are differentially expressed when SrfJ is present.
Project description:Immune cells need to swiftly and effectively respond to invading pathogens. This response relies heavily on rapid protein synthesis and accurate cellular targeting to ensure pathogen destruction. In return, pathogens intercept this response so they can survive and proliferate. To gain insight into this dynamic interface, we combined click-chemistry with pulsed stable isotope labelling of amino acids (pSILAC-AHA) and quantified the newly synthesised host proteome during macrophage infection with the model intracellular bacterial pathogen, Salmonella enterica Typhimurium (STm). We monitored newly synthesized proteins across different compartments and during different infection stages, and used available proteomics data in response to LPS to deconvolute the STm-specific response. Within this rich resource, we detect aberrant trafficking of lysosomal proteases to the extracellular space and the nucleus, the latter of which correlates with signatures of cell death. Pharmacological cathepsin inhibition suppressed caspase-11 dependent macrophage cell death, thus demonstrating an active role for cathepsins during STm induced pyroptosis. Our study illustrates the utility of resolving the host proteome dynamics during infection to drive the discovery of novel biological mechanisms at the host-microbe interface.
Project description:Intracellular pathogens, such as Salmonella enterica serovar Typhimurium (S.Tm), are able to sense and respond to a changing host cell environment. Macrophages exposed to microbial products undergo metabolic changes that are increasingly understood to drive a productive inflammatory response. However, the role of macrophage metabolic reprogramming in bacterial adaptation to the intracellular environment has not been explored. Here we show that changes in host metabolic state serve as a signal detected byS.Tm. Using metabolic profiling and dual RNA-seq, we show that succinate accumulates in infected macrophages and is sensed by intracellular S.Tm to promote induction of virulence genes. Succinate uptake by the bacterium drives induction of pmrAB-dependent genes and SPI-2 virulence-associated regulon. S.Tm lacking the DcuB transporter for succinate uptake display impaired intracellular survival. Our work demonstrates that accumulation of metabolic intermediates, necessary for macrophage activation, promote intracellular survival of pathogens, opening a new realm of metabolic host-pathogen crosstalk.
Project description:Intracellular pathogens, such as Salmonella enterica serovar Typhimurium (S.Tm), are able to sense and respond to a changing host cell environment. Macrophages exposed to microbial products undergo metabolic changes that are increasingly understood to drive a productive inflammatory response. However, the role of macrophage metabolic reprogramming in bacterial adaptation to the intracellular environment has not been explored. Here we show that changes in host metabolic state serve as a signal detected byS.Tm. Using metabolic profiling and dual RNA-seq, we show that succinate accumulates in infected macrophages and is sensed by intracellular S.Tm to promote induction of virulence genes. Succinate uptake by the bacterium drives induction of pmrAB-dependent genes and SPI-2 virulence-associated regulon. S.Tm lacking the DcuB transporter for succinate uptake display impaired intracellular survival. Our work demonstrates that accumulation of metabolic intermediates, necessary for macrophage activation, promote intracellular survival of pathogens, opening a new realm of metabolic host-pathogen crosstalk.
Project description:Intracellular pathogens, such as Salmonella enterica serovar Typhimurium (S.Tm), are able to sense and respond to a changing host cell environment. Macrophages exposed to microbial products undergo metabolic changes that are increasingly understood to drive a productive inflammatory response. However, the role of macrophage metabolic reprogramming in bacterial adaptation to the intracellular environment has not been explored. Here we show that changes in host metabolic state serve as a signal detected byS.Tm. Using metabolic profiling and dual RNA-seq, we show that succinate accumulates in infected macrophages and is sensed by intracellular S.Tm to promote induction of virulence genes. Succinate uptake by the bacterium drives induction of pmrAB-dependent genes and SPI-2 virulence-associated regulon. S.Tm lacking the DcuB transporter for succinate uptake display impaired intracellular survival. Our work demonstrates that accumulation of metabolic intermediates, necessary for macrophage activation, promote intracellular survival of pathogens, opening a new realm of metabolic host-pathogen crosstalk.
Project description:Single-cell profiling identifies ACE+ granuloma macrophages as a non-permissive niche for intracellular bacteria during persistent Salmonella infection
Project description:An all pairs experiment design type is where all labeled extracts are compared to every other labeled extract. We have adapted a microarray-based transposon tracking strategy for use with a Salmonella enterica serovar Typhimurium cDNA microarray in order to identify genes important for survival and replication in RAW 264.7 mouse macrophage-like cells or in the spleens of BALB/cJ mice. A 50,000-CFU transposon library of S. enterica serovar Typhimurium strain SL1344 was serially passaged in cultured macrophages or intraperitoneally inoculated into BALB/cJ mice. The bacterial genomic DNA was isolated and processed for analysis on the microarray. The novel application of this approach to identify mutants unable to survive in cultured cells resulted in the identification of components of Salmonella pathogenicity island 2 (SPI2), which is known to be critical for intracellular survival and replication. Computed
Project description:To investigate the polarization status of macrophages during salmonella persistent infection we established a model of Salmonella enterica serovar Thyphimurium infection in the zebrafish larva in which salmonella survive long term inside the host. In this model, during initial stages of the infection, macrophages are recruited to the infection site and express tnfa. By contrast, in the late stages of the infection, macrophages form clusters at the infection site and do not express tnfa. The objective is to characterize the transcriptional profile of macrophages in early stage of infection (4 hours post-infection) and late stage of infection (4 days post-infection).