HIV-1 matrix protein p17 induces human plasmacytoid dendritic cells to acquire a migratory immature cell phenotype

Numerical and functional defects in plasmacytoid dendritic cells (pDCs) are an important hallmark of progressive HIV-1 infection, yet its etiology remains obscure. HIV-1 p17 matrix protein (p17) modulates a variety of cellular responses, and its biological activity depends on the expression of p17 receptors (p17Rs) on the surface of target cells. In this study, we show that peripheral blood pDCs express p17Rs on their surface and that freshly isolated pDCs are sensitive to p17 stimulation. Upon p17 treatment, pDCs undergo phenotypic differentiation with up-regulation of CCR7. A chemotaxis assay reveals that p17-treated pDCs migrate in response to CCL19, suggesting that these cells may acquire the ability to migrate to secondary lymphoid organs. In contrast, p17 does not induce release of type I IFN nor does it enhance pDC expression of CD80, CD86, CD83, or MHC class II. Microarray gene expression analysis indicated that p17-stimulated pDCs down-regulate the expression of molecules whose functions are crucial for efficient protein synthesis, protection from apoptosis, and cell proliferation induction. Based on these results, we propose a model where p17 induces immature circulating pDCs to home in lymph nodes devoid of their ability to serve as a link between innate and adaptative immune systems.     

MSE55, a Cdc42 effector protein, induces long cellular extensions in fibroblasts

Cdc42 is a member of the Rho GTPase family that regulates multiple cellular activities, including actin polymerization, kinase-signaling activation, and cell polarization. MSE55 is a nonkinase CRIB (Cdc42/Rac interactive-binding) domain-containing molecule of unknown function. Using glutathione S-transferase-capture experiments, we show that MSE55 binds to Cdc42 in a GTP-dependent manner. MSE55 binding to Cdc42 required an intact CRIB domain, because a MSE55 CRIB domain mutant no longer interacted with Cdc42. To study the function of MSE55 we transfected either wild-type MSE55 or a MSE55 CRIB mutant into mammalian cells. In Cos-7 cells, wild-type MSE55 localized at membrane ruffles and increased membrane actin polymerization, whereas expression of the MSE55 CRIB mutant showed fewer membrane ruffles. In contrast to these results, MSE55 induced the formation of long, actin-based protrusions in NIH 3T3 cells as detected by immunofluorescence and live-cell video microscopy. MSE55-induced protrusion formation was blocked by expression of dominant-negative N17Cdc42, but not by expression of dominant-negative N17Rac. These findings indicate that MSE55 is a Cdc42 effector protein that mediates actin cytoskeleton reorganization at the plasma membrane.     

Osteopontin functionally activates dendritic cells and induces their differentiation toward a Th1-polarizing phenotype

Osteopontin (OPN) has been shown to have T helper 1 (Th1) cytokine functions in cell-mediated immunity. Deficiency of OPN is linked to a reduced Th1 immune response in autoimmunity, infectious disease, and delayed-type allergy. Dendritic cells (DCs) are central for the induction of T-cell-mediated immunity, when initially flexible DCs are instructed by priming signals and tissue-derived factors to adopt Th1, Th2, or regulatory T-cell-inducing phenotypes. Although OPN influences the cytokine secretion of T cells and macrophages, its effects on DC polarization remain an important missing link in the understanding of OPN functions in Th1 immunity. Here we demonstrate that OPN promotes the emigration of human DCs from the epidermis and functionally activates myeloid-type DCs, augmenting their expression of HLA-DR, costimulatory, and adhesion molecules. OPN induces their Th1-promoting tumor necrosis factor alpha (TNF-alpha) and interleukin-12 (IL-12) secretion, and enhances their allostimulatory capacity. In mixed lymphocyte reactions (MLRs), OPN stimulates IL-12 secretion by DCs, inducing elevated interferon-gamma (IFN-gamma) production by T cells. Naive Th cells stimulated by OPN-activated DCs show a Th1-polarized cytokine production. Our findings identify OPN as an important tissue-derived factor that DCs encounter when traveling from peripheral sites of activation to secondary lymphatic organs, which induces DC maturation toward a Th1-promoting phenotype.     

树突状细胞在HIV-1感染中的作用

树突状细胞(dendritic cells,DC)为体内重要的专职抗原提呈细胞(APC),是机体T细胞特异免疫应答的直接启动和调控者。近年来,树突状细胞的分化发育、抗原加工提呈机制及其在肿瘤、感染、自身免疫性疾病和移植排斥中的作用,已经成为免疫学的前沿领域,DCs在生产与控制适宜的免疫反应中扮演了十分重要的角色。未成熟DCs(iDCs)广泛地分布于体内并占据了组织中的“哨所”位置,并     

Hepatitis C virus NS4 protein impairs the Th1 polarization of immature dendritic cells

Summary. Dendritic cells (DCs) in chronic hepatitis C patients display impaired function, although the details remain unclear. To investigate the hepatitis C virus (HCV) protein that has the most impact on DC function, we compared five recombinant proteins and seven HCV protein genes in modulating DC phenotype and function. Immature DCs (iDCs) were established from healthy donor peripheral blood monocytes with granulocyte–macrophage colony stimulating factor (GM‐CSF) and IL‐4. Lipopolysaccharide was used to establish mature DCs (mDCs). Cells were then pulsed with HCV recombinant proteins or transfected with HCV plasmids and subsequently assayed for cell surface marker expression by flow cytometry. For cytokine and proliferative T‐cell response analysis, DCs were cultured with autologous CD4 T cells and tuberculin purified protein derivative (PPD). Mean fluorescent intensity of CD86 was reduced in HCV protein‐pulsed iDCs. Proliferative T‐cell responses and Th1 cytokine concentrations were reduced with HCV nonstructural proteins (NS), particularly with HCV NS4. HCV nonstructural proteins, particularly NS4, change the iDC phenotype and reduce antigen‐specific T‐cell stimulatory function with Th1 cytokine reductions.     

Activation of HIV-1 specific CD4 and CD8 T cells by human dendritic cells: roles for cross-presentation and non-infectious HIV-1 virus

BACKGROUND: The CD4 T cells in mucosal subepithelia are the first cells to become infected during sexual transmission of HIV-1. Dendritic cells (DC) are located in the same area and are known to play a central role in antiviral immune responses. However, extensive viral replication, syncytia formation and cell death follows the interaction between T cells and DC previously exposed to HIV-1. Despite this, anti-HIV responses are generated that control viremia following acute infection. OBJECTIVE: The anti-HIV-1 cellular immune responses observed may be activated by sources other than productively infected DC. HIV-1 induces apoptosis both in cells it infects and in bystander cells. Furthermore, retroviral replication typically generates a predominance of defective particles. We tested whether DC exposed to antigen from either of these sources could elicit anti-HIV specific immune responses. DESIGN AND METHODS: Apoptotic or necrotic monocytes infected with vaccinia virus vectors encoding HIV antigens, a cell line with integrated HIV-1 and apoptotic CD4 T cells pulsed with non-infectious or infectious HIV-1 virus were used as sources of antigens to assess cross presentation by DC. Furthermore, direct DC presentation of antigen from non-infectious and infectious HIV-1 was examined. RESULTS: We find that dead cells expressing HIV-1 antigens as well as non-infectious HIV-1 particles can be acquired and processed by DC, leading to the activation, differentiation and expansion of viral antigen-specific CD4 and CD8 T cells from seropositive individuals. CONCLUSIONS: These sources of antigens may be critical for the generation and maintenance of anti-HIV-1 immunity by DC.     

Efficient inhibition of HIV-1 replication in human immature monocyte-derived dendritic cells by purified anti-HIV-1 IgG without induction of maturation

During mucosal HIV transmission, immature dendritic cells (DCs) present in the mucosa are among the first cellular targets of the virus. Previous studies have analyzed the inhibition of HIV-1 transfer from human mature DCs to T lymphocytes by neutralizing IgG, but so far no in vitro data regarding the capacity of antibodies to inhibit HIV-1 infection of immature DCs have been reported. Here, we found an increased HIV-inhibitory activity of monoclonal IgG and purified polyclonal IgG when immature monocyte-derived dendritic cells (iMDDCs) were used as target cells instead of autologous blood lymphocytes. We showed that FcgammaRII is involved in the mechanism for inhibiting HIV-1 infection of iMDDCs by IgG, whereas no induction of maturation was detected at concentrations of IgG that result in a 90% reduction of HIV replication. After induction of FcgammaRI expression on iMDDCs by IFN-gamma, an augmentation of the HIV-inhibitory activity of IgG, related to the expression of FcgammaRI, was observed. Taken together, our results demonstrate the participation of FcgammaRs in HIV-1 inhibition by IgG when iMDDCs are the targets. We propose that IgG is able to efficiently inhibit HIV-1 replication in iMDDCs and should be one of the components to be induced by vaccination.     

Elevated levels of the small GTPase Cdc42 induces senescence in male rat mesenchymal stem cells

Mesenchymal stem cells (MSCs) represent a promising cell source for cellular therapy and tissue engineering and are currently being tested in a number of clinical trials for various diseases. However, like other somatic cells, MSCs age, and this senescence is accompanied by a progressive decline in stem cell function. Several lines of evidence suggest a role for the Rho family GTPase Cdc42 activity in cellular senescence processes. In the present study, we have examined aging-associated Cdc42 activity in rat adipose-derived mesenchymal stem cells (ADMSCs) and the consequences of pharmacological inhibition of Cdc42 in ADMSCs from aged rats. We demonstrate that ADMSCs show a decreased rate of cell growth and a decreased ability to differentiate into chrodrogenic, osteogenic and adipogenic cell lineages as a function of rat age. This is accompanied with an increased staining for SA-β-Gal activity and increased levels of Cdc42 bound to GTP. Treatment of ADMSCs from 24-month old rats with three Cdc42 inhibitors significantly increased proliferation rates, decreased SA-β-Gal staining, and reduced Cdc42-GTP. The Cdc42 inhibitor CASIN increased adipogenic and osteogenic differentiation potential in ADMSCs from 24-month old rats, and decreased the levels of radical oxygen species (ROS), p16^INK4a levels, F-actin, and the activity of the ERK1/2 and JNK signaling pathways that were all elevated in these cells. These data suggest that ADMSCs show increased rates of senescence as rats age that appear to be due to elevated Cdc42 activity. Thus, Cdc42 plays important roles in MSC senescence and differentiation potential, and pharmacological reduction of Cdc42 activity can, at least partially, rejuvenate aged MSCs.     

白细胞介素-10基因修饰的未成熟树突状细胞诱导自身免疫性心肌炎特异性耐受的实验研究

目的探讨白细胞介素(IL)-10基因修饰的未成熟树突状细胞(iDC)对实验性自身免疫性心肌炎的作用。方法从Lewis大鼠骨髓培养成熟树突状细胞(mDC)和iDC,pcDNA3-IL-10质粒转染iDC。分别将2×106 mDC、iDC、pcDNA3-iDC、pcDNA3-IL-10-iDC或PBS回输5天前以猪心肌肌球蛋白免疫的实验性自身免疫性心肌炎大鼠体内。3周后观察心肌炎症、超声心动图、Th1/Th2细胞因子、主要组织相容性Ⅱ(MHC-Ⅱ)类分子及共刺激分子表达。以T细胞增殖实验及过继转移实验检测pcDNA3-IL-10-iDC诱导耐受的抗原特异性。结果IL-10基因修饰的iDC显著抑制抗原特异性T细胞增殖,pcDNA3-IL-10-iDC治疗后实验性自身免疫性心肌炎大鼠心肌炎症显著减轻,心功能改善,MHC-Ⅱ、共刺激分子表达显著降低,脾细胞分泌细胞因子呈Th2型。结论IL-10基因修饰的iDC可诱导实验性自身免疫性心肌炎产生抗原特异性耐受,其机制与IL-10诱导的Th1/Th2偏离及MHC-Ⅱ、共刺激分子表达下调等有关。     

CCR7 ligands induce rapid endocytosis in mature dendritic cells with concomitant up-regulation of Cdc42 and Rac activities

Although chemokines are well known to function in chemotaxis, additional roles for these molecules in the immune system are not well understood. Dendritic cells (DCs) developmentally regulate the expression of chemokine receptors to facilitate their migration from the peripheral tissues to regional lymph nodes. Expressions of CCR1 and CCR5 on immature DCs are down-regulated on maturation, whereas CCR7 is selectively expressed on mature DCs. In the present study, we examined the effects of CCL19 and CCL21, 2 CCR7 ligands, on endocytosis of fluorescein isothiocyanate (FITC)-dextran by murine DCs. Both CCL19 and CCL21 markedly induced rapid uptake of FITC-dextran by mature DCs but not immature DCs. In contrast, CCL3, a ligand of CCR1 and CCR5, induced rapid uptake of FITC-dextran by immature DCs but not mature DCs. CCL19-induced endocytosis could be completely blocked by Clostridium difficile toxin B, which inhibits the Rho guanosine triphosphatase proteins, Rho, Rac, and Cdc42. This process was not abrogated by Y-27632, a specific inhibitor of Rho-associated kinase. In addition, CCL19 rapidly enhanced Cdc42 and Rac activity in mature DCs. These findings demonstrate that certain chemokines induce rapid endocytosis in each relevant DC population. It is suggested that CCR7 ligands activate Cdc42 and Rac, thereby inducing the endocytosis in mature DCs.     

HIV-1 Gag-specific immunity induced by a lentivector-based vaccine directed to dendritic cells

Lentivectors (LVs) have attracted considerable interest for their potential as a vaccine delivery vehicle. In this study, we evaluate in mice a dendritic cell (DC)-directed LV system encoding the Gag protein of human immunodeficiency virus (HIV) (LV-Gag) as a potential vaccine for inducing an anti-HIV immune response. The DC-directed specificity is achieved through pseudotyping the vector with an engineered Sindbis virus glycoprotein capable of selectively binding to the DC-SIGN protein. A single immunization by this vector induces a durable HIV Gag-specific immune response. We investigated the antigen-specific immunity and T-cell memory generated by a prime/boost vaccine regimen delivered by either successive LV-Gag injections or a DNA prime/LV-Gag boost protocol. We found that both prime/boost regimens significantly enhance cellular and humoral immune responses. Importantly, a heterologous DNA prime/LV-Gag boost regimen results in superior Gag-specific T-cell responses as compared with a DNA prime/adenovector boost immunization. It induces not only a higher magnitude response, as measured by Gag-specific tetramer analysis and intracellular IFN-γ staining, but also a better quality of response evidenced by a wider mix of cytokines produced by the Gag-specific CD8⁺ and CD4⁺ T cells. A boosting immunization with LV-Gag also generates T cells reactive to a broader range of Gag-derived epitopes. These results demonstrate that this DC-directed LV immunization is a potent modality for eliciting anti-HIV immune responses.     

Subset of DC-SIGN(+) dendritic cells in human blood transmits HIV-1 to T lymphocytes

The dendritic cell (DC)-specific molecule DC-SIGN is a receptor for the HIV-1 envelope glycoprotein gp120 and is essential for the dissemination of HIV-1. DC-SIGN is expressed by DCs, both monocyte-derived DCs and DCs in several tissues, including mucosa and lymph nodes. To identify a DC-SIGN(+) DC in blood that may be involved in HIV-1 infection through blood, we have analyzed the expression of DC-SIGN in human blood cells. Here we describe the characterization of a subset of DCs in human blood, isolated from T-/NK-/B-cell-depleted peripheral blood mononuclear cells (PBMCs) on the basis of expression of DC-SIGN. This subset coexpresses CD14, CD16, and CD33 and is thus of myeloid origin. In contrast to CD14(+) monocytes, DC-SIGN(+) blood cells display a DC-like morphology and express markers of antigen-presenting cells, including CD1c, CD11b, CD11c, CD86, and high levels of major histocompatibility complex (MHC) class I and II molecules. This DC population differs from other described CD14(-) blood DC subsets. Functionally, DC-SIGN(+) blood DCs are able to stimulate proliferation of allogeneic T cells and can produce tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) upon activation with lipopolysaccharide (LPS). When they encounter HIV-1, low amounts of these blood DC-SIGN(+) DCs enhance infection of T lymphocytes in trans, whereas blood monocytes and CD14(-) blood DCs are not capable of transmitting HIV-1. Therefore DC-SIGN(+) blood DCs can be the first target for HIV-1 upon transmission via blood; they can capture minute amounts of HIV-1 through DC-SIGN and transfer HIV-1 to infect target T cells in trans.     

Therapeutic immunization with dendritic cells loaded with heat-inactivated autologous HIV-1 in patients with chronic HIV-1 infection

Therapeutic immunization with autologous monocyte-derived dendritic cells (DCs) loaded with heat-inactivated autologous human immunodeficiency virus type 1 (HIV-1) in 12 patients with chronic HIV-1 infection who were receiving highly active antiretroviral therapy (HAART) was feasible, safe, and well tolerated. Virus was obtained during an initial interruption of HAART (hereafter, "stop 1") so that DCs could be pulsed. After immunization and a second interruption of HAART (hereafter, "stop 2"), set-point plasma viral load (PVL; 24 weeks after stop 2) decreased > or =0.5 log(10) copies/mL relative to baseline PVL in 4 of 12 patients. We observed a significant lengthening in mean doubling time of PVL rebound and significant decreases in the area under the curve and the mean peak of PVL rebound after stop 2, compared with those after stop 1. This response was associated with changes in HIV-1-specific CD4(+) lymphoproliferative and CD8(+) T cell responses. These changes were not observed in a group of nonimmunized control patients.     

Probiotic Bio-Three induces Th1 and anti-inflammatory effects in PBMC and dendritic cells

AIM:To investigate the immune response of peripheral blood mononuclear cells(PBMCs)and dendritic cells (DCs)that were stimulated by probiotic preparations. METHODS:PBMCs were isolated,cultured,and stimulated with Bio-Three(a mixture of Bacillus mesentericus, Clostridium butyricum and Enterococcus faecalis;105, 10 6 and 10 7 CFU/mL for 24 h).Cytokine production of (1)circulating PBMCs;(2)PBMCs stimulated by probiotic preparation;(3)monocyte-derived DCs;and(4)DC andT cell co-culture was determined by enzyme-l...     

Priming of human immunodeficiency virus type 1 (HIV-1)-specific CD8+ T cell responses by dendritic cells loaded with HIV-1 proteins

Proteins may serve as ideal CD8(+) T cell immunogens for human immunodeficiency virus type 1 (HIV-1) if they can be delivered to and processed through the human leukocyte antigen class I pathway. This study shows that human blood monocyte-derived dendritic cells loaded with liposome-complexed HIV-1 proteins and matured with CD40 ligand can prime CD8(+) T cells to HIV-1 in vitro. Whole HIV-1 protein in liposome may be an effective immunogen for HIV-1 vaccine protocols.     

联合应用供体未成熟树突状细胞与CD40L mAb诱导大鼠小肠移植免疫耐受

目的:研究供体骨髓来源的未成熟树突状细胞(imDC)联合CD40L mAbi诱导大鼠小肠移植免疫耐受.方法:体外培养供体大鼠树突状细胞(DC),实验动物分为3组,受体于手术前分别预处理后进行小肠移植.A组(n=15):注射生理盐水;B组(n=15):注射供体来源的imDC;C组(n=151:同时注射供体来源的imDC CD40L mAb.观察受体存活时间(n=6),移植小肠病理学检查,用ELISA法检测受体血清IL-2、INF-γ和IL-10水平(n=5).结果:C组受体动物存活时间明显长于A、B两组,统计学有显著差异(22.67±7.09 d vs7.17±1.47 d,11.00±2.61 d,P＜0.01),C组移植小肠炎性细胞浸润、黏膜结构破坏程度、血清IL-2、INF-γ水平均明显低于A、B组,有统计学差异(IL-2:225.4±48.7 ng/Lvs 374.1±13.2 ng/L,353.6±10.4 ng/L;INF-γ:56.9±2.6 ng/Lvs 229.2±20.6,125.4±18.5 ng/L,P＜0.05),血清IL-10水平C组明显高于A、B组,有统计学意义(186.4±10.6 ng/Lvs 91.7±5.4,162.2±8.1 ng/L,P＜0.05).结论:联合应用CD40L mAb和imDC可抑制小肠移植后的排斥反应,诱导受体产生免疫耐受.