Dissecting the molecular programs governing interferon production by plasmacytoid dendritic cells during a viral infection in vivo
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ABSTRACT: Plasmacytoid dendritic cells (pDC) are the major source of type I and type III interferons (IFN-I/III) during viral infections, in response to triggering of endosomal Toll Like Receptors (TLRs) 7 or 9 by viral single-stranded RNA or unmethylated CpG DNA, respectively. Interestingly, this function is restricted to a minor fraction of pDC (Zucchini et al. Int. Immunol. 2008). In this project, we aimed at identifying the molecular pathways involved in inducing IFN-I/III production in this minor faction of pDC during in vivo infection by the mouse cytomegalovirus (MCMV). To achive this goal, we infected with MCMV Ifnb1Eyfp mice, in which IFN-producing pDC can be detected by YFP expression (Scheu et al. PNAS 2008). Thanks to this model, we were able to sort three distinct subsets of pDC: CD86-YFP- (not activated, non IFN-producing), CD86+YFP- (activated, non IFN-producing) and CD86+YFP+ (activated, IFN-producing) and to perform microarray analysis. This allowed us to select genes differentially expressed among these three subsets and to mine these data in order to identify the related signaling pathways.
Project description:Plasmacytoid dendritic cells (pDC) are the major source of type I interferons (IFN-I) during viral infections, in response to triggering of endosomal Toll Like Receptors (TLR) 7 or 9 by viral single-stranded RNA or unmethylated CpG DNA, respectively. IFN-I production in pDC occurs in specialized endosomes encompassing preformed signaling complexes of TLR7 or 9 with their adaptor molecule MyD88 and the transcription factor interferon regulatory factor 7 (IRF7). The triggering of TLR leads to IRF7 phosphorylation, nuclear translocation and binding to the promoters of the genes encoding IFN-I to initiate their transcription. pDC express uniquely high levels of IRF7 at steady state and this expression is further enhanced by positive IFN-I feedback signaling during viral infections. However, the specific cell-intrinsic roles of MyD88 versus IFN-I signaling in pDC responses to a viral infection have not been rigorously dissected. To achieve this aim, we generated mixed bone marrow chimera mice (MBMC) allowing to rigorously compare the gene expression profiles of WT versus Ifnar1-KO or MyD88-KO pDC isolated from the same animals at steady state or after infection with the mouse cytomegalovirus (MCMV). Our results indicate that, in vivo during MCMV infection, pDC undergo a major transcriptional reprogramming, under combined instruction of IFN-I, IFN-γ and direct TLR triggering. However, these different stimuli drive specific, largely distinct, gene expression programs. We rigorously determined which gene modules require cell-intrinsic IFN-I signaling for their induction in pDC during a physiological viral infection in vivo. We delineated non-redundant versus shared versus antagonistic responses with IFN-γ. We demonstrated that cell-intrinsic IFN-I responsiveness is dispensable for induction of the expression of all IFN-I/III genes and many cytokines or chemokines in pDC during MCMV infection, contrary to MyD88 signaling.
Project description:Plasmacytoid dendritic cells (pDC) are the major source of type I IFN (IFN-I) in vivo during Murine Cytomegalovirus (MCMV) infection. This response requires pDC-intrinsic MyD88-dependent signaling by Toll Like Receptors 7/9. Provided that they express appropriate recognition receptors such as Ly49H, Natural Killer (NK) cells can directly sense and kill MCMV-infected cells. While MyD88- and Ly49H-dependent responses can contribute to MCMV control, the objective is to understand the relative importance of these 3 mechanisms. In order to decipher the relative impact of MyD88- and Ly49H-dependent mechanisms during MCMV infection, we performed a genome-wide expression analysis on total spleen of Ly49H-/-MyD88+/+, Ly49H-/-MyD88-/-, Ly49H+/+MyD88+/+ and Ly49H+/+MyD88-/- BALB/c mice at different time points after MCMV infection (d0, d1,5, d2, d3 and d6). This study includes data from the spleen BALB/c mice, under steady-state or MCMV condition at different time points. 2 to 5 mice for each mouse strain for each time point were used, and were hybridized on 5 separate batches of gene chips.
Project description:Type I IFNs are critical in initiating protective antiviral immune responses and plasmacytoid DCs (pDCs) represent a major source of these cytokines. Here we show that only few pDCs are capable to produce IFN? after virus infection or CpG stimulation. Utilizing IFN?/YFP reporter mice, we identify these IFN?-producing cells in the spleen as a CCR9+CD9- pDC subset exclusively localized within the T/B cell zones. IFN?-producing pDCs exhibit a distinct transcriptome profile with higher expression of genes encoding cytokines and chemokines, facilitating T cell recruitment and activation. These distinctive characteristics of IFN?-producing pDCs are independent of the type I IFN receptor mediated feedback loop. Furthermore, IFN?-producing pDCs exhibit enhanced CCR7-dependent migratory properties in vitro and in a peritoneal inflammation model they effectively recruit T cells in vivo. We define “professional type I IFN-producing cells” as a distinct subset of pDCs specialized in coordinating cellular immune responses. IFN? associated gene expression in ex vivo sorted IFN?/YFPpos vs. IFN?/YFPneg splenic pDCs was measured at 6 hr after i.v. injection of CpG 1668 complexed to DOTAP. Two independent experiments were performed using pooled samples of at least 12 mice per experiment.
Project description:Objective: Patients with Systemic Lupus Erythematosus (SLE) have an ongoing interferon (IFN) production due to an activation of plasmacytoid dendritic cells (pDCs), which can be triggered to type I IFN synthesis by RNA containing immune complexes (RNA-IC). Considering emerging data suggesting a role of type III interferon (IFN) in the SLE disease process, we asked if RNA-IC can induce type III IFN production in pDC, and how this production can be regulated. Methods: Peripheral blood mononuclear cells (PBMCs) or immune cell subsets were isolated from healthy blood donors or SLE patients and stimulated with IC containing U1 snRNP and SLE-IgG (RNA-IC). Hydroxychloroquine (HCQ) and an interleukin receptor 1 associated kinase 4 inhibitor (IRAK4i) were added to cell cultures. Cytokine mRNA levels were determined with a microarray and protein levels with immunoassays. Single-cell RNA-sequencing of pDCs using ddSEQ technology was performed. Results: Type III IFN mRNA and protein was induced in RNA-IC stimulated pDC-NK and pDC-B cell co-cultures. A subset of activated pDCs (3%) expressed both type III and type I IFN mRNA. IFN-λ2, IFN-α2b, interleukin (IL)-3, IL-6 or granulocyte-macrophage colony stimulating factor (GM-CSF) enhanced IFN-λ1/3 production 2-5-fold. HCQ and an IRAK4i blocked the RNA-IC-triggered IFN-λ1/3 production (p<0.01). IFN-α2b and GM-CSF increased the proportion of SLE patients producing IFN-λ1/3 in response to RNA-IC from 11 to 33%. Conclusions: Type III IFN production is triggered by RNA-IC in pDCs in a TLR-MyD88-dependent manner, enhanced by NK and B cells as well as several pro-inflammatory cytokines. These results support a contributing role for both type I and type III IFNs in SLE, which needs to be considered when targeting the IFN system in this disease.
Project description:Objective: Patients with Systemic Lupus Erythematosus (SLE) have an ongoing interferon (IFN) production due to an activation of plasmacytoid dendritic cells (pDCs), which can be triggered to type I IFN synthesis by RNA containing immune complexes (RNA-IC). Considering emerging data suggesting a role of type III interferon (IFN) in the SLE disease process, we asked if RNA-IC can induce type III IFN production in pDC, and how this production can be regulated. Methods: Peripheral blood mononuclear cells (PBMCs) or immune cell subsets were isolated from healthy blood donors or SLE patients and stimulated with IC containing U1 snRNP and SLE-IgG (RNA-IC). Hydroxychloroquine (HCQ) and an interleukin receptor 1 associated kinase 4 inhibitor (IRAK4i) were added to cell cultures. Cytokine mRNA levels were determined with a microarray and protein levels with immunoassays. Single-cell RNA-sequencing of pDCs using ddSEQ technology was performed. Results: Type III IFN mRNA and protein was induced in RNA-IC stimulated pDC-NK and pDC-B cell co-cultures. A subset of activated pDCs (3%) expressed both type III and type I IFN mRNA. IFN-λ2, IFN-α2b, interleukin (IL)-3, IL-6 or granulocyte-macrophage colony stimulating factor (GM-CSF) enhanced IFN-λ1/3 production 2-5-fold. HCQ and an IRAK4i blocked the RNA-IC-triggered IFN-λ1/3 production (p<0.01). IFN-α2b and GM-CSF increased the proportion of SLE patients producing IFN-λ1/3 in response to RNA-IC from 11 to 33%. Conclusions: Type III IFN production is triggered by RNA-IC in pDCs in a TLR-MyD88-dependent manner, enhanced by NK and B cells as well as several pro-inflammatory cytokines. These results support a contributing role for both type I and type III IFNs in SLE, which needs to be considered when targeting the IFN system in this disease.
Project description:Plasmacytoid dendritic cells (pDC) are the major source of type I IFN (IFN-I) in vivo during Murine Cytomegalovirus (MCMV) infection. This response requires pDC-intrinsic MyD88-dependent signaling by Toll Like Receptors 7/9. Provided that they express appropriate recognition receptors such as Ly49H, Natural Killer (NK) cells can directly sense and kill MCMV-infected cells. While MyD88- and Ly49H-dependent responses can contribute to MCMV control, the objective is to understand the relative importance of these 3 mechanisms. In order to decipher the relative impact of MyD88- and Ly49H-dependent mechanisms during MCMV infection, we performed a genome-wide expression analysis on total spleen of Ly49H-/-MyD88+/+, Ly49H-/-MyD88-/-, Ly49H+/+MyD88+/+ and Ly49H+/+MyD88-/- BALB/c mice at different time points after MCMV infection (d0, d1,5, d2, d3 and d6).
Project description:Type I IFNs are critical in initiating protective antiviral immune responses and plasmacytoid DCs (pDCs) represent a major source of these cytokines. Here we show that only few pDCs are capable to produce IFNβ after virus infection or CpG stimulation. Utilizing IFNβ/YFP reporter mice, we identify these IFNβ-producing cells in the spleen as a CCR9+CD9- pDC subset exclusively localized within the T/B cell zones. IFNβ-producing pDCs exhibit a distinct transcriptome profile with higher expression of genes encoding cytokines and chemokines, facilitating T cell recruitment and activation. These distinctive characteristics of IFNβ-producing pDCs are independent of the type I IFN receptor mediated feedback loop. Furthermore, IFNβ-producing pDCs exhibit enhanced CCR7-dependent migratory properties in vitro and in a peritoneal inflammation model they effectively recruit T cells in vivo. We define “professional type I IFN-producing cells” as a distinct subset of pDCs specialized in coordinating cellular immune responses.
Project description:Human rhinoviruses (HRV) are usually innocuous viruses; however, they can trigger serious consequences in certain individuals, especially in the setting of deficient interferon (IFN) synthesis. Plasmacytoid dendritic cells (pDC) are key IFN producing cells, though we know little about the mechanisms by which pDC regulate HRV-induced immune responses. Herein we used gene expression microarrays to examine HRV-induced mRNA in blood mononuclear cells from healthy people, in combination with pDC depletion to assess whether observed expression patterns were pDC dependent. As expected, pDC depletion led to a major reduction in HRV-induced IFN-α release, and this was associated with profound differences in gene expression between intact PBMC and pDC depleted PBMC. pDC depletion led to major changes in upstream regulators, with 70-80% of the HRV activated genes appearing to be pDC dependent. PCR validation experiments confirmed changes seen in the microarrays, specifically the extent to which the following differentially expressed genes were highly pDC dependent: the transcription factor IRF7, both IL-27 chains (IL-27 and EBI3), the alpha chain of the IL-15 receptor (IL-15RA) and the IFN stimulated gene IFI27. IL-6, IFN-γ and IL-27 protein synthesis were also highly pDC dependent. Supplementing pDC-depleted cultures with either recombinant IFN-γ, IL-15, IL-27 or IL-6 was able to restore the IFN-α response, thereby compensating for the absence of pDC. Though pDC comprise only a minority population of migratory leukocytes, our findings highlight the extent to which these cells are able to exert a profound effect on the immune response to HRV.
Project description:Plasmacytoid dendritic cells (pDCs) can be activated by the endosomal TLRs, and contribute to the pathogenesis of systemic lupus erythematosus (SLE) by producing type I IFNs. Thus, blocking TLR-mediated pDC activation may represent a useful approach for the treatment of SLE. In an attempt to identify a therapeutic target for blocking TLR signaling in pDCs, we investigated the contribution of Bruton's tyrosine kinase (Btk) to the activation of pDCs by TLR7 and TLR9 stimulation by using a selective Btk inhibitor RN486. Stimulation of TLR7 and 9 with their respective agonist, namely, gardiquimod and type A CpG ODN2216, resulted in the activation of human pDCs, as demonstrated by the expression of activation markers (CD69, CD40, and CD86), elevated production of IFN-alpha and other inflammatory cytokines, as well as up-regulation of numerous genes including IFN-alpha-inducible genes and activation of interferon regulatory factor 7 (IRF7) and NF-kB. RN486 inhibited all of these events induced by TLR9, but not TLR7 stimulation, with a nanomolar potency for inhibiting type A CpG ODN2216-mediated production of cytokines (e.g., IC50=386 nM for inhibiting IFN-alpha). Our data reveal Btk as an important regulatory enzyme in the TLR9 pathway, and a potential therapeutic target for SLE and other TLR-driven diseases. pDCs from healthy donors (n=4) were treated with gardiquimod (TLR7 agonist) or ODN 2216 (TLR9 agonist) with or without BTK inhibitor for 3 hours.
Project description:Plasmacytoid dendritic cells (pDCs) can rapidly produce interferons and other soluble factors in response to extracellular viruses or virus mimics such as CpG-containing DNA. pDCs can also recognize live cells infected with certain RNA viruses, but the relevance and functional consequences of such recognition remain unclear. We studied the response of primary DCs to the prototypical persistent DNA virus, the human cytomegalovirus (CMV). Human pDCs responded poorly to free CMV but strongly to live CMV-infected fibroblasts, in a process that involved integrin-mediated adhesion, transfer of viral DNA to pDCs and its recognition through TLR9. Compared to transient polyfunctional responses to CpG or free influenza virus, pDC response to CMV-infected cells was long-lasting, dominated by the production of type I (IFN-I) and type III (IFN-III) interferons, and lacked diversification into functionally distinct populations. Similarly, pDC activation by influenza-infected lung epithelial cells was highly efficient, prolonged and dominated by interferon production. Prolonged pDC activation by CMV-infected cells facilitated the activation of natural killer cells that are critical for CMV control. Finally, patients with CMV viremia harbored phenotypically activated pDCs and increased levels of IFN-I and IFN-III in circulation. Thus, recognition of live infected cells is a common mechanism of virus detection by pDCs that elicits a unique antiviral response program.