Scientific Resources

The extent,regulation and enzymatic basis of RNA editing by cytidine deamination are incompletely understood. Here we show that transcripts of hundreds of genes undergo site-specific CtextgreaterU RNA editing in macrophages during M1 polarization and in monocytes in response to hypoxia and interferons. This editing alters the amino acid sequences for scores of proteins,including many that are involved in pathogenesis of viral diseases. APOBEC3A,which is known to deaminate cytidines of single-stranded DNA and to inhibit viruses and retrotransposons,mediates this RNA editing. Amino acid residues of APOBEC3A that are known to be required for its DNA deamination and anti-retrotransposition activities were also found to affect its RNA deamination activity. Our study demonstrates the cellular RNA editing activity of a member of the APOBEC3 family of innate restriction factors and expands the understanding of CtextgreaterU RNA editing in mammals. View Publication

HIV-1 infection leads to numerous B cell abnormalities,including hypergammaglobulinemia,nonspecific B cell activation,nonspecific class switching,increased cell turnover,breakage of tolerance,increased immature/transitional B cells,B cell malignancies,as well as a loss of capacity to generate and maintain memory,all of which contribute to a global impairment of the immune humoral compartment. Several cytokines and soluble factors,which are increased in sera of HIV-1-infected individuals,have been suggested to directly or indirectly contribute to these B cell dysfunctions,and one of these is the B cell-activating factor (BAFF). We report in this study that HIV-1 (X4- and R5-tropic) upregulates BAFF expression and secretion by human monocytes. Moreover,we show that the virus-mediated production of BAFF by monocytes relies on a type I IFN response by a small percentage of plasmacytoid dendritic cells (pDCs) present in the monocyte cultures. HIV-1-induced type I IFN by pDCs triggers BAFF production in both classical and intermediate monocytes,but not in nonclassical monocytes,which nonetheless display a very strong basal BAFF production. We report also that basal BAFF secretion was higher in monocytes obtained from females compared with those from male donors. This study provides a novel mechanistic explanation for the increased BAFF levels observed during HIV-1 infection and highlights the importance of pDC/monocyte crosstalk to drive BAFF secretion. View Publication

Manipulation of the CD28/CTLA-4 pathway is at the heart of a number of immunomodulatory approaches used in both autoimmunity and cancer. Although it is clear that CTLA-4 is a critical regulator of T cell responses,the immunological contexts in which CTLA-4 controls immune responses are not well defined. In this study,we show that whereas CD80/CD86-dependent activation of resting human T cells caused extensive T cell proliferation and robust CTLA-4 expression,in this context CTLA-4 blocking Abs had no impact on the response. In contrast,in settings where CTLA-4(+) cells were present as regulators� View Publication

Owing to ongoing recognition of pathogen-associated molecular patterns,immune activation and upregulation of IFN-stimulated genes (ISGs) are sustained in the chronically infected host. Albeit most ISGs are important effectors for containing viral replication,some might exert compensatory immune suppression to limit pathological dysfunctions,although the mechanisms are not fully understood. In this study,we report that the ISG lymphocyte Ag 6 complex,locus E (LY6E) is a negative immune regulator of monocytes. LY6E in monocytes negatively modulated CD14 expression and subsequently dampened the responsiveness to LPS stimulation in vitro. In the setting of chronic HIV infection,the upregulation of LY6E was correlated with reduced CD14 level on monocytes; however,the immunosuppressive effect of LY6E was not adequate to remedy the hyperresponsiveness of activated monocytes. Taken together,the regulatory LY6E pathway in monocytes represents one of negative feedback mechanisms that counterbalance monocyte activation,which might be caused by LPS translocation through the compromised gastrointestinal tract during persistent HIV-1 infection and may serve as a potential target for immune intervention. View Publication

The ontogeny of human Langerhans cells (LCs) remains poorly characterized,in particular the nature of LC precursors and the factors that may drive LC differentiation. Here we report that thymic stromal lymphopoietin (TSLP),a keratinocyte-derived cytokine involved in epithelial inflammation,cooperates with transforming growth factor (TGF)-β for the generation of LCs. We show that primary human blood BDCA-1(+),but not BDCA-3(+),dendritic cells (DCs) stimulated with TSLP and TGF-β harbor a typical CD1a(+)Langerin(+) LC phenotype. Electron microscopy established the presence of Birbeck granules,an intracellular organelle specific to LCs. LC differentiation was not observed from tonsil BDCA-1(+) and BDCA-3(+) subsets. TSLP + TGF-β LCs had a mature phenotype with high surface levels of CD80,CD86,and CD40. They induced a potent CD4(+) T-helper (Th) cell expansion and differentiation into Th2 cells with increased production of tumor necrosis factor-α and interleukin-6 compared with CD34-derived LCs. Our findings establish a novel LC differentiation pathway from BDCA-1(+) blood DCs with potential implications in epithelial inflammation. Therapeutic targeting of TSLP may interfere with tissue LC repopulation from circulating precursors. View Publication

BACKGROUND Acute respiratory distress syndrome (ARDS) is characterized by overwhelming inflammatory responses and lung remodeling. We hypothesized that leukocyte infiltration during the inflammatory response modulates epithelial remodeling through a mechanism of epithelial-mesenchymal transition (EMT). METHODS Human lung epithelial cells were treated for 30 min with hydrochloric acid (HCl). Human monocytes were then cocultured with the epithelial cells for up to 48 h,in the presence or absence of blocking peptides against lymphocyte function-associated antigen-1 (LFA-1),or tyrphostin A9,a specific inhibitor for platelet-derived growth factor (PDGF) receptor tyrosine kinase. RESULTS Exposure of lung epithelial cells to HCl resulted in increased expression of intercellular adhesion molecule-1 (ICAM-1) and production of interleukin (IL)-8 at 24 h. The expression of the epithelial markers E-cadherin decreased while the mesenchymal markers vimentin and α-smooth muscle actin (α-SMA) increased at 24 h and remained high at 48 h. The addition of monocytes augmented the profiles of lower expression of epithelial markers and higher mesenchymal markers accompanied by increased collagen deposition. This EMT profile was associated with an enhanced production of IL-8 and PDGF. Treatment of the lung epithelial cells with the LAF-1 blocking peptides CD11a237-246 or/and CD18112-122 suppressed monocyte adhesion,production of IL-8,PDGF and hydroxyproline as well as EMT markers. Treatment with tyrphostin A9 prevented the EMT profile shift induced by HCl stimulation. CONCLUSIONS The interaction between epithelial cells and monocytes enhanced epithelial remodelling after initial injury through EMT signalling that is associated with the release of soluble mediators,including IL-8 and PDGF. View Publication

The recruitment of monocytes and their differentiation into macrophages at sites of inflammation are key events in determining the outcome of the inflammatory response and initiating the return to tissue homeostasis. To study monocyte trafficking and macrophage differentiation in vivo,we have generated a novel transgenic reporter mouse expressing a green fluorescent protein (GFP) under the control of the human CD68 promoter. CD68-GFP mice express high levels of GFP in both monocyte and embryo-derived tissue resident macrophages in adult animals. The human CD68 promoter drives GFP expression in all CD115(+) monocytes of adult blood,spleen,and bone marrow; we took advantage of this to directly compare the trafficking of bone marrow-derived CD68-GFP monocytes to that of CX3CR1(GFP) monocytes in vivo using a sterile zymosan peritonitis model. Unlike CX3CR1(GFP) monocytes,which downregulate GFP expression on differentiation into macrophages in this model,CD68-GFP monocytes retain high-level GFP expression for 72 hours after differentiation into macrophages,allowing continued cell tracking during resolution of inflammation. In summary,this novel CD68-GFP transgenic reporter mouse line represents a powerful resource for analyzing monocyte mobilization and monocyte trafficking as well as studying the fate of recruited monocytes in models of acute and chronic inflammation. View Publication

Gaucher disease is caused by an inherited deficiency of glucocerebrosidase that manifests with storage of glycolipids in lysosomes,particularly in macrophages. Available cell lines modeling Gaucher disease do not demonstrate lysosomal storage of glycolipids; therefore,we set out to develop two macrophage models of Gaucher disease that exhibit appropriate substrate accumulation. We used these cellular models both to investigate altered macrophage biology in Gaucher disease and to evaluate candidate drugs for its treatment. We generated and characterized monocyte-derived macrophages from 20 patients carrying different Gaucher disease mutations. In addition,we created induced pluripotent stem cell (iPSC)-derived macrophages from five fibroblast lines taken from patients with type 1 or type 2 Gaucher disease. Macrophages derived from patient monocytes or iPSCs showed reduced glucocerebrosidase activity and increased storage of glucocerebroside and glucosylsphingosine in lysosomes. These macrophages showed efficient phagocytosis of bacteria but reduced production of intracellular reactive oxygen species and impaired chemotaxis. The disease phenotype was reversed with a noninhibitory small-molecule chaperone drug that enhanced glucocerebrosidase activity in the macrophages,reduced glycolipid storage,and normalized chemotaxis and production of reactive oxygen species. Macrophages differentiated from patient monocytes or patient-derived iPSCs provide cellular models that can be used to investigate disease pathogenesis and facilitate drug development. View Publication

Spleen tyrosine kinase (Syk) is an attractive drug target in autoimmune,inflammatory,and oncology disease indications. The most advanced Syk inhibitor,R406,1 (or its prodrug form fostamatinib,2),has shown efficacy in multiple therapeutic indications,but its clinical progress has been hampered by dose-limiting adverse effects that have been attributed,at least in part,to the off-target activities of 1. It is expected that a more selective Syk inhibitor would provide a greater therapeutic window. Herein we report the discovery and optimization of a novel series of imidazo[1,2-a]pyrazine Syk inhibitors. This work culminated in the identification of GS-9973,68,a highly selective and orally efficacious Syk inhibitor which is currently undergoing clinical evaluation for autoimmune and oncology indications. View Publication

As sentinels of the immune system,dendritic cells (DCs) play an essential role in regulating cellular immune responses. One of the main challenges of developing DC-targeted therapies includes the delivery of antigen to DCs in order to promote the activation of antigen-specific effector CD8 T cells. With the goal of creating antigen-directed immunotherapeutics that can be safely administered directly to patients,Immune Design has developed a platform of novel integration-deficient lentiviral vectors that target and deliver antigen-encoding nucleic acids to human DCs. This platform,termed ID-VP02,utilizes a novel genetic variant of a Sindbis virus envelope glycoprotein with posttranslational carbohydrate modifications in combination with Vpx,a SIVmac viral accessory protein,to achieve efficient targeting and transduction of human DCs. In addition,ID-VP02 incorporates safety features in its design that include two redundant mechanisms to render ID-VP02 integration-deficient. Here,we describe the characteristics that allow ID-VP02 to specifically transduce human DCs,and the advances that ID-VP02 brings to conventional third-generation lentiviral vector design as well as demonstrate upstream production yields that will enable manufacturing feasibility studies to be conducted. View Publication

Circulating levels of leptin are elevated in type-2 diabetes mellitus (T2DM) and leptin plays a role in immune responses. Elevated circulating IL-18 levels are associated with clinical complications of T2DM. IL-18 regulates cytokine secretion and the function of a number of immune cells including T-cells,neutrophils and macrophages and as such has a key role in immunity and inflammation. Pro-inflammatory monocytes exhibiting elevated cytokine secretion are closely associated with inflammation in T2DM,however,little is known about the role of leptin in modifying monocyte IL-18 secretion. We therefore aimed to investigate the effect of leptin on IL-18 secretion by monocytes. We report herein that leptin increases IL-18 secretion in THP-1 and primary human monocytes but has no effect on IL-18mRNA. Leptin and LPS signalling in monocytes occurs by overlapping but distinct pathways. Thus,in contrast to a strong stimulation by LPS,leptin has no effect on IL-1βmRNA levels or IL-1β secretion. In addition,LPS stimulates the secretion of IL-6 but leptin did not whereas both treatments up regulate IL-8 secretion from the same cells. Although leptin (and LPS) has a synergistic effect with exogenous ATP on IL-18 secretion in both THP-1 and primary monocytes,experiments involving ATP assays and pharmacological inhibition of ATP signalling failed to provide any evidence that endogenous ATP secreted by leptin-stimulated monocytes was responsible for enhancement of monocyte IL-18 secretion by leptin. Analysis of the action of caspase-1 revealed that leptin up regulates caspase-1 activity and the effect of leptin on IL-18 release is prevented by caspase-1 inhibitor (Ac-YVAD-cmk). These data suggest that leptin activates IL-18 processing rather than IL-18 transcription. In conclusion,leptin enhances IL-18 secretion via modulation of the caspase-1 inflammasome function and acts synergistically with ATP in this regard. This process may contribute to aberrant immune responses in T2DM and other conditions of hyperleptinemia. View Publication

We describe here the effects of three drugs that are either approved or have the potential for treating multiple sclerosis (MS) patients through the in vitro activities of human natural killer (NK) cells and dendritic cells (DCs). Our results indicate that 1,25(OH)2D3,the biologically active metabolite of vitamin D3,calcipotriol and FTY720 augment IL-2-activated NK cell lysis of K562 and RAJI tumor cell lines as well as immature (i) and mature (m) DCs,with variable efficacies. These results are corroborated with the ability of the drugs to up-regulate the expression of NK cytotoxicity receptors NKp30 and NKp44,as well as NKG2D on the surfaces of NK cells. Also,they down-regulate the expression of the killer inhibitory receptor CD158. The three drugs down-regulate the expression of CCR6 on the surface of iDCs,whereas vitamin D3 and calcipotriol tend to up-regulate the expression of CCR7 on mDCs,suggesting that they may influence the migration of DCs into the lymph nodes. Finally,vitamin D3,calcipotriol and FTY720 enhance NK17/NK1 cell lysis of K562 cells,suggesting that a possible mechanism of action for these drugs is via activating these newly described cells. In conclusion,our results show novel mechanisms of action for vitamin D3,calcipotriol and FTY720 on cells of the innate immune system. View Publication