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: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:We present a detailed single cell time course of the macrophage response to Salmonella infection. By combining phenotypic fluorescent labels with single cell expression analysis we are able to identify gene modules associated with bacterial exposure and bacterial infection. We also identify other genetic clusters that are expressed heterogenously, ananlyzing both their regulation and their impact on infection Analysis of 192 single cells across 4 time points after Salmonella exposure (MOI 1:1) with one of three different fluorescent labels indicating whether a given cell contained no intracellular bacteria (non-fluorescent), contained dead intracellular bacteria (only pHrodo positive), or contained live intracellular bacteria (pHrodo and GFP positive)
Project description:Interactions between intracellular bacteria and mononuclear phagocytes give rise to diverse cellular phenotypes that may determine the outcome of infection. Recent advances in single-cell RNA-seq (scRNA-seq) have identified multiple subsets within the mononuclear population, but implications to their function during infection remain unknown. Here, we applied microscopy, flow cytometry and scRNA-seq to survey the mononuclear niche of intracellular Salmonella Typhimurium (S.Tm) during early systemic infection in mice. We describe eclipse-like growth kinetics in the spleen, with a first phase of bacterial control mediated by tissue-resident red-pulp macrophages. A second phase involved extensive bacterial replication within a newly identified macrophage population characterized by CD9 expression. Using Nr4a1e2-/- mice we established that CD9+ macrophages originated from non-classical monocytes (NCM), and NCM-depleted mice were more resistant to S.Tm infection. Our study defines a novel host-pathogen interface, with macrophage subset-specific interactions that determines early infection dynamics and the infection outcome of the entire organism.
Project description:Interactions between intracellular bacteria and mononuclear phagocytes give rise to diverse cellular phenotypes that may determine the outcome of infection. Recent advances in single-cell RNA-seq (scRNA-seq) have identified multiple subsets within the mononuclear population, but implications to their function during infection remain unknown. Here, we applied microscopy, flow cytometry and scRNA-seq to survey the mononuclear niche of intracellular Salmonella Typhimurium (S.Tm) during early systemic infection in mice. We describe eclipse-like growth kinetics in the spleen, with a first phase of bacterial control mediated by tissue-resident red-pulp macrophages. A second phase involved extensive bacterial replication within a newly identified macrophage population characterized by CD9 expression. Using Nr4a1e2-/- mice we established that CD9+ macrophages originated from non-classical monocytes (NCM), and NCM-depleted mice were more resistant to S.Tm infection. Our study defines a novel host-pathogen interface, with macrophage subset-specific interactions that determines early infection dynamics and the infection outcome of the entire organism.
Project description:Interactions between intracellular bacteria and mononuclear phagocytes give rise to diverse cellular phenotypes that may determine the outcome of infection. Recent advances in single-cell RNA-seq (scRNA-seq) have identified multiple subsets within the mononuclear population, but implications to their function during infection remain unknown. Here, we applied microscopy, flow cytometry and scRNA-seq to survey the mononuclear niche of intracellular Salmonella Typhimurium (S.Tm) during early systemic infection in mice. We describe eclipse-like growth kinetics in the spleen, with a first phase of bacterial control mediated by tissue-resident red-pulp macrophages. A second phase involved extensive bacterial replication within a newly identified macrophage population characterized by CD9 expression. Using Nr4a1e2-/- mice we established that CD9+ macrophages originated from non-classical monocytes (NCM), and NCM-depleted mice were more resistant to S.Tm infection. Our study defines a novel host-pathogen interface, with macrophage subset-specific interactions that determines early infection dynamics and the infection outcome of the entire organism.
Project description:We present a detailed single cell analysis of the macrophage response to LPS from Salmonella enterica. By combining single cell transcriptional analysis, fluorescently labeled, LPS-coated beads, and cytometry we are able to distinguish the responses of macrophages that have internalized LPS-coated beads and those that have not.
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.