Human dendritic cell maturation by adenovirus transduction enhances tumor antigen-specific T-cell responses

Dendritic cells (DCs) have been shown to require a degree of maturation to stimulate antigen-specific, type 1 cytotoxic T lymphocytes in numerous murine models. Limited data in humans suggest that immature DCs (DC) can induce tolerance, yet a variety of nonmatured DC used clinically have induced antigen-specific type 1 T cells in vivo to various tumor-associated antigens. Use of adenovirus to engineer DCs is an efficient method for delivery of entire genes to DC, but the data on the biologic effects of viral transduction are contradictory. The authors demonstrate that DCs transduced with adenovirus (AdV) clearly become more mature by the phenotypic criterion of upregulation of CD83 and downregulation of CD14. Transduced DCs also decrease production of IL-10, and a subset of transduced DCs produce increased levels of IL-12 p70. This level of maturation is superior to that achieved by treatment of these cells with tumor necrosis factor-alpha or interferon-alpha but less pronounced than with CD40L trimer or CD40L + interferon-gamma. Maturation by AdV transduction alone leads to efficient stimulation of antigen-specific T cells from both healthy donors and patients with advanced cancer using two defined human tumor-associated antigens, MART-1 and AFP. Given the pivotal role of DCs in immune activation, it is important to understand the direct biologic effects of AdV on DCs, as well as the impact these biologic changes have on the stimulation of antigen-specific T cells. This study has important implications for the design of DC-based clinical trials.     

Cord blood stem-cell-derived dendritic cells generate potent antigen-specific immune responses and anti-tumour effects

The aim of the present study was to investigate whether CBSCs [(umbilical) cord blood stem cells] can be a new source of DCs (dendritic cells), which can generate more potent antigen-specific immune responses and anti-tumour effects. CBSCs and PBMCs (peripheral blood mononuclear cells) were collected, cultured and differentiated into DCs. Surface markers, secreting cytokines, antigen-presentation activity, antigen-specific cell-mediated immunity and cytotoxic killing effects induced by these two DC origins were evaluated and compared. CBSCs were expanded ~17-fold by ex vivo culture. The expression of surface markers in CBSC-derived DCs were higher than those in PBMC-derived DCs treated with LPS (lipopolysaccharide). The CBSC-derived DCs mainly secreted IL (interleukin)-6, IL-10 and TNF (tumour necrosis factor)-α, whereas PBMC-derived DCs mainly secreted IL-5 and IFN (interferon)-γ. The CBSC-derived DCs had better antigen-presentation abilities when stimulated with LPS or TNF-α, induced higher numbers of IFN-γ-secreting antigen-specific CD8+ T-cells, as assessed using an ELISpot (enzyme-linked immunosorbent spot) assay, and stimulated more potent antigen-specific CTL (cytotoxic T-cell) activities (P<0.01, one-way ANOVA). CBSC-derived DCs had quicker and greater ERK (extracellular-signal-regulated kinase) and Akt phosphorylation, and weaker p38 phosphorylation, than PBMC-derived DCs when stimulated with LPS. In conclusion, CBSC-derived DCs have the ability to induce stronger antigen-specific immunity and more potent anti-tumour effects and therefore could be a good source of DCs for use in DC-based cancer vaccines and immunotherapy.     

Interleukin 1 enhances T-dependent immune responses by amplifying the function of dendritic cells

The function of exogenous murine recombinant IL-1 alpha as a T lymphocyte-activating molecule was examined. IL-1 did not induce IL-2 release or responsiveness in purified T cells regardless of their state of activation: unprimed lymphocytes, freshly sensitized lymphocytes, or memory cells derived from the blasts. Nor did IL-1 synergize with mitogens, or with antigens, to stimulate proliferation. For example the combinations of IL-1 plus Ia+ peritoneal macrophages, or IL-1 plus Con A, were less than 5% as effective in triggering T cell growth as a low dose (1%) of dendritic cells. However, when IL-1 was added at the onset of culture, the response to limiting doses of dendritic cells was increased 3- to 10-fold in several systems: the syngeneic and allogeneic MLR, Con A- and periodate-induced polyclonal mitogenesis, and T-dependent antibody formation against foreign red cells. The amplifying effect of IL-1 could be obtained if the dendritic cells but not the responding lymphocytes were exposed to IL-1 before use as accessory cells. Optimal activation of dendritic cells required a dose of 5 U/ml (50 pM) and 18 h of exposure, and was not due to carryover of IL-1 into the lymphocyte culture. IL-2, IL-3, and cachectin/TNF did not amplify dendritic cell function, while IFN-gamma diminished it. The enhanced function of IL-1-treated dendritic cells was due to an enhanced clustering with helper T lymphocytes in the first day of the MLR response. Therefore IL-1 does not seem to act as an activating factor for most peripheral T lymphocytes. Instead, IL-1 enhances the function of accessory dendritic cells and represents the first molecule that has been shown to enhance the immune response at this critical level.     

Autologous dendritic cells transfected with prostate-specific antigen RNA stimulate CTL responses against metastatic prostate tumors

Autologous dendritic cells (DCs) transfected with mRNA encoding prostate-specific antigen (PSA) are able to stimulate potent, T cell-mediated antitumor immune responses in vitro. A phase I trial was performed to evaluate this strategy for safety, feasibility, and efficacy to induce T cell responses against the self-protein PSA in patients with metastatic prostate cancer. In 13 study subjects, escalating doses of PSA mRNA-transfected DCs were administered with no evidence of dose-limiting toxicity or adverse effects, including autoimmunity. Induction of PSA-specific T cell responses was consistently detected in all patients, suggesting in vivo bioactivity of the vaccine. Vaccination was further associated with a significant decrease in the log slope PSA in six of seven subjects; three patients that could be analyzed exhibited a transient molecular clearance of circulating tumor cells. The demonstration of vaccine safety, successful in vivo induction of PSA-specific immunity, and impact on surrogate clinical endpoints provides a scientific rationale for further clinical investigation of RNA-transfected DCs in the treatment of human cancer.     

超声联合SonoVue微泡介导NET-1siRNA转染人肝癌细胞

目的探讨超声联合微泡造影剂介导NET-1siRNA在人肝癌细胞中的转染效果。方法将培养的HepG2细胞分为5组:A组为空白对照;B组培养瓶中仅加入NET-1siRNA;C组为加入脂质体及NET-1siRNA;D组为加入造影剂及NET-1siRNA并给予超声辐照;E组为加入脂质体、造影剂、NET-1siRNA,并给予超声辐照。之后以荧光显微镜检测NET-1siRNA转染率,RT-PCR法检测各组细胞NET-1 mRNA的基因表达,Western-Blotting法检测各组细胞NET-1表达情况,MTT检测HepG2细胞生长情况。结果与C组、D组相比,E组NET-1siRNA转染率明显提高(P<0.05);D组和E组细胞内NET-1mRNA及NET-1蛋白的表达抑制率均高于其他各组(P均<0.01),而转染后24～72hHepG2细胞增殖受到明显抑制。结论超声联合微泡造影剂能有效促进NET-1siRNA在肝癌细胞中的表达,并抑制肝癌细胞的增殖。     

K562细胞RNA负载人树突状细胞后体外诱导特异性CTL的研究

目的探讨人的树突状细胞(dendriticcell,DC)体外经K562细胞株总RNA转染后,能否诱导出p210蛋白表达,并诱导特异性细胞毒T淋巴细胞(CTL)。方法自健康人浓缩白细胞制品(白膜)分离有粘附特性的单核细胞(PBMC),经GMCSF、IL4培养5d后,获得未成熟的DC(imatureDC,imDC);体外以脂质体DOTAP或直接电穿孔转染K562细胞总RNA。抽提转染前后以及转染24h后的DC内RNA进行RTPCR检测,Westernblot分析p210蛋白表达,以及诱导CTL杀伤K562细胞功能检测等。PBMC以每组5×106/ml,分别在不同组分的培养液中培养DC,通过细胞计数、流式细胞仪测定CD1a表达、细胞纯度来估计制备效果。结果RTPCR检测表明DC经K562总RNA转染后,细胞内出现BcrAbl的cDNA条带,24h后消失。Westernblot试验表明转染24h后,开始表达p210特征性蛋白;并且明显促进T细胞对K562的杀伤活性。1%自体血浆体积分数RPMI1640培养的DC的CD1a表达量最高,并且细胞获得数量也仅屈居第二,为总体评价较高的一组。结论应用肿瘤总RNA负载DC来制备DC疫苗具有可行性,预示改良的DC疫苗抗肿瘤的广泛应用前景。     

转染A549细胞总RNA的树突状细胞疫苗抗肿瘤效应的体外研究

目的探讨人肺腺癌细胞株A549总RNA转染的人树突状细胞(DCs)在体外诱导特异性抗肿瘤免疫反应的能力。方法利用密度梯度离心法从血细胞分离机新鲜采集的外周富集血中分离出单个核细胞(PBMCs),贴壁获得单核细胞,加入重组人粒细胞巨噬细胞集落刺激因子(rhGM-CSF)和重组人白细胞介素-4(rhIL-4)进一步诱导为树突状细胞(DCs),同时利用提取的A549细胞总RNA转染DCs来制备疫苗,并与T细胞混合培养诱导扩增细胞毒性T淋巴细胞(CTLs);实验分为转染A549细胞总RNA的DC组、未转染DC组和转染空脂质体DC组,分别以流式细胞术(FCM)鉴定DCs表型、酶联免疫吸附法(ELISA)检测IL-12、IFN-γ分泌水平、3H-TdR掺入检测T细胞增殖能力及乳酸脱氢酶(LDH)释放法测定杀伤肿瘤活性并比较各组差异。结果1)转染总RNA组DCs表面CD40、CD80、CD83、HLA-DR的表达较未转染组DCs和转染空脂质体组DCs均有升高,CD40在3组的表达率分别为(69.01±7.67)%、(19.28±3.51)%和(39.62±2.72)%;CD80在3组的表达率分别为:(74.39±6.46)%、(15.48±3.03)%和(25.70±2.92)%;CD83在3组的表达率分别为:(81.79±4.61)%、(13.29±2.34)%和(31.42±1.97)%;HLA-DR在3组的表达率分别为:(76.53±5.13)%、(49.23±4.05)%和(29.94±3.53)%,差异有统计学意义(P<0.05);2)转染总RNA组DCs的IL-12和IFN-γ分泌水平较未转染组及转染空脂质体组明显升高(P<0.05),3组IL-12分别为(543.24±68.33)、(77.11±27.65)和(167.78±31.84)pg/ml;3组IFN-γ分别为:(122.95±32.84)、(41.06±10.97)和(56.08±15.96)pg/ml;3)3H-TdR掺入试验所得的cpm,3组分别为(7437±720)、(3 807±476)和(4 543±719),阳性对照组为:16 739±91,差异有统计学意义(P<0.05);4)LDH释放法可见转染A549总RNA的DC组的特异性杀瘤活性(58.54±8.27)%,明显高于未转染组(36.03±4.03)%和转染空脂质体组(33.47±8.21)%,差异具有统计学意义(P<0.05)。结论人肺腺癌细胞A549总RNA转染的DC疫苗体外诱导的特异性抗肿瘤免疫能力显著增强,有望为肺腺癌的治疗提供新的手段。     

急性白血病RNA转染脐血源性树突状细胞介导的免疫作用

目的检测应用脐血诱导成熟树突状细胞(DC),并以急性白血病(AL)总RNA冲击该DC所诱导产生的特异性细胞毒T细胞(CTL)的杀伤活性。方法取AL患者外周血或骨髓,以淋巴细胞分离液获得单个核细胞(MNC),并提取RNA。分离脐血MNC,以2×106个细胞/孔接种于12孔培养板,培养体系中加入重组人粒单核细胞集落刺激因子(rhGM-CSF),重组人白细胞介素4(rhIL-4)和肿瘤坏死因子α(TNF-α),并在培养第5天,加入白血病总RNA,致敏脐血DC。培养过程中,观察树突状细胞形态,流式细胞仪检测表型。培养第12天收获成熟DC,与自体T淋巴细胞共培养,诱导产生白血病特异性CTL,乳酸脱氢酶法(LDH法)测定溶细胞活性。结果脐血来源DC表现出成熟DC典型形态和免疫表型特征,培养第5天,DC相关分化抗原CD1a、CD83、CD86、CD80的表达较培养前增高,差异有统计学意义(P<0.01);培养至第12天,DC相关分化抗原CD1a、CD83、CD86、CD80的表达较培养第5天增高,另外人类白细胞相关抗原(HLA-DR)的表达也较培养第5天增高,差异均具有统计学意义(P<0.01)。以白血病RNA转染的DC组所刺激的自体T淋巴细胞对自身白血病靶细胞显示出明显的杀伤活性,而未经抗原转染DC组无明显杀伤活性,按照各效靶比进行两者的比较,差异有统计学意义(P<0.01)。结论利用细胞因子体外诱导脐带血产生大量成熟DC,以急性白血病RNA转染此DC,并以此白血病特异性DC诱导产生抗白血病特异性CTL,不失为清除AL患者体内残留灶的积极措施。     

Macrophage colony-stimulating factor can modulate immune responses and attract dendritic cells in vivo

Studies have indicated that professional APCs in the periphery, such as dendritic cells and macrophages, play an important role in initiating DNA vaccine-specific immune responses. To engineer the immune response induced by DNA vaccines in vivo we investigated the modulatory effects of codelivering growth factor genes for the hematopoietic APCs along with DNA vaccines. Specifically, we examined the effects on the antigen-specific immune responses following the codelivery of the gene expression cassettes for M-CSF, G-CSF, and GM-CSF along with HIV-1 DNA immunogen constructs. We observed that coimmunization with GM-CSF increased the antibody response and resulted in a significant enhancement of lymphoproliferative response. Furthermore, among all coinjection combinations, we found that M-CSF coinjections resulted in a high level of CTL enhancement. This enhancement of CTL responses observed from the coinjection with M-CSF was CD8+ T cell dependent and was associated with the presence of CD11c+ cells at the site of injection and with the antigen-specific induction of the beta-chemokine MIP-1beta, suggesting a role for this chemokine in CTL induction. These results suggest that hematopoietic growth factors should be further studied as potential adjuvants for in vivo modulators of immune responses.     

Enhanced transgene expression and effective in vivo antitumor immune responses initiated by dendritic progenitors transfected with a nonviral T7 vector expressing a model tumor antigen

Genetic education of dendritic cells (DCs) with tumor-associated antigens is an encouraging development in DC-mediated tumor immunotherapy. In this study, to increase the transgene expression by DCs using nonviral vectors, a cytoplasmic T7 vector (T7T7/T7Luc) was used to transfect bone marrow-derived DCs with the firefly luciferase gene as a reporter and as a model tumor antigen. As a result, the luciferase activity of T7T7/T7Luc-transfected DCs was more than four times greater than that of DCs transfected with pCMVLuc, a commonly used nonviral vector. Furthermore, the luciferase activity was increased three times more when dendritic progenitor cells rather than mature DCs were transfected. In vivo tumor studies showed that T7T7/T7Luc-transfected DCs, which express high levels of luciferase (model tumor antigen), stimulated a stronger immune response than did pCMVLuc-transfected DCs, which express relatively low levels of luciferase, as indicated by the cytotoxic T lymphocyte assay. T7T7/T7Luc transfected DCs, when injected into recipient mice, evoked an antigen-specific immune response that can effectively eradicate implanted metastasis and prevent new tumor development by murine melanoma cells genetically modified to express luciferase. Therefore, the T7 system is a powerful nonviral vector that can be used to genetically educate DCs with tumor-associated antigens for tumor immunotherapy.     

Parvovirus H-1-induced tumor cell death enhances human immune response in vitro via increased phagocytosis, maturation, and cross-presentation by dendritic cells

Oncotropic and oncolytic viruses have attracted high attention as antitumor agents because they preferentially kill cancer cells in vitro and reduce the incidence of spontaneous, induced, or implanted animal tumors. Some autonomous parvoviruses (H-1, minute virus of mice) and derived recombinant vectors are currently under preclinical evaluation. Still not fully understood, their antitumor properties involve more than just tumor cell killing. Because wild-type parvovirus-mediated tumor cell lysates (TCLs) may trigger antigen-presenting cells (APCs) to augment the host immune repertoire, we analyzed phagocytosis, maturation, and crosspresentation of H-1-induced TCLs by human dendritic cells (DCs). We first established H-1-mediated oncolysis in two HLA-A2(+) and A2(-) variant melanoma cell clones. Monocyte-derived immature DCs phagocytosed H- 1-infected TCLs as well as ultraviolet-induced apoptotic TCLs and better than freeze-thaw-induced necrotic TCLs. Immature DCs incubated with H-1-induced TCLs acquired specific maturation markers comparable to a standard cytokine cocktail. Furthermore, A2(+) DCs pulsed with H-1-infected A2(-) TCLs cross-presented melanoma antigens to specific cytotoxic T lymphocytes (CTLs) and released proinflammatory cytokines. This shows for the first time that tumor cell killing by a wild-type oncolytic virus directly stimulates human APCs and CTLs. Because H-1-infected tumors enhance the immune repertoire, the clinical perspectives of parvoviral vectors are even more promising.     

Primary stimulation by dendritic cells induces antiviral proliferative and cytotoxic T cell responses in vitro

We used well-gassed hanging drop (20 microliters) cultures with high concentrations of purified T cells from normal BALB/c mice to examine whether dendritic cells (DC) can induce primary antiviral proliferative T cell responses and generate virus-specific CTL. We found that DC exposed to infectious influenza virus in vitro or in vivo in small numbers (0.1-1%) resulted in strong proliferation of responder T cells within 3 d, and this was strongly inhibited by antibodies to class II MHC molecules. In addition, in 5-d cultures, the influenza-treated DC generated CTL specifically able to lyse influenza-infected syngeneic target cells bearing MHC class I antigens. The most potent nucleoprotein (NP) epitope recognized by BALB/c CTL is peptide 147-158 (Arg156-) and influenza-infected DC in vitro stimulated CTL recognizing this peptide, thus mimicking the response in mice primed by intranasal influenza infection. We also induced T cell proliferation and virus-specific CTL in cultures of normal T cells by stimulating with DC pulsed with the natural NP sequence 147-158 or the potent peptide 147-158 (Arg156-). Small numbers of peritoneal exudate cells, after activation with Con A to produce class II MHC expression and after removal of DC with a specific mAb (33DI), did not lead to primary CTL generation but initiated secondary stimulation in vitro. Our results using the hanging drop culture method and DC as APC have implications for studying the T cell repertoire for viral components in humans without the necessity of previous immunization.     

肺腺癌细胞总RNA转染树突状细胞诱导特异性CTLs的体内抗肿瘤效应研究

目的探讨人肺腺癌细胞总RNA转染的树突状细胞(DCs)诱导抗原特异性的细胞毒T细胞(CTLs)对移植瘤裸鼠的抗肿瘤作用。方法 1)从外周血单个核细胞(PBMCs)中诱导DCs,提取人肺癌细胞A549总RNA,用于电转染DCs,转染后的DCs与自体T细胞混合培养,诱导抗原特异性的CTLs;2)实验分为转染RNA的DCs组、转染PBS的DCs组和未转染DCs组,流式细胞术(FCM)鉴定T细胞表型,3H-TdR掺入检测T细胞增殖能力;3)建立肺癌细胞株A549荷瘤裸鼠模型,过继回输CTLs,比较肿瘤体积,计算抑瘤率,免疫组化法检测移植瘤组织中Bax、Bcl-2、COX-2和VEGF的表达,并用全自动图像分析系统分析其平均光密度值(MOD)。结果 1)转染RNA的DCs和自体T细胞共育诱导的CTLs的CD8+T细胞大幅度上调,表达率(79.29±2.18)%明显高于转染PBS的DCs组CD8+T细胞(26.10±1.76)%和未转染DCs组CD8+T细胞(25.58±2.73)%(P0.05);2)转染RNA的DCs显著刺激了自体T细胞增殖,3H-TdR渗入所得的cpm值:阳性对照组为17 105±130,转染RNA的DCs组为7 759±493,转染PBS的DCs组为2 611±161,未转染DCs组为2 248±332(P0.05);3)成功建立肺癌裸鼠移植瘤模型,实验结束时,转染RNA组裸鼠荷瘤体积(540±99)mm3明显小于转染PBS组(1 572±147)mm3和未转染组(2 043±395)mm3(P0.05);4)转染RNA组和转染PBS组的抑瘤率分别为68.53%和8.62%;5)转染RNA的DCs诱导的CTLs能显著上调Bax的表达(转染RNA组MOD值为335±105),显著下调Bcl-2、COX-2和VEGF的表达(转染RNA组MOD值分别为146±47、122±33和128±58)。结论人肺腺癌细胞总RNA转染DCs诱导的抗原特异性CTLs对肺腺癌裸鼠移植瘤的生长产生抑制作用。     

IL-12 in conjunction with dendritic cells enhances antiviral CD8+ CTL responses in vitro.

CD8+ cytolytic T lymphocytes (CTLs) are important mediators for resistance to infections and malignant diseases. IL-12 enhances proliferative and cytolytic responses by killer cells, but its function in the generation of human antiviral CD8+ T cell responses has not been defined. We therefore evaluated the role of IL-12 in the generation of CTLs to influenza-infected dendritic cells. IL-12 was not detectable in supernatants of infected-dendritic cells, or during CTL generation. Furthermore, anti-IL-12 antibody did not block CTL generation. However, exogenous IL-12 (30-300 pg/ml) enhanced CD8+ T cell proliferative and cytolytic responses. The effect was greatest in individuals with weak reactivity to influenza virus or at antigen-presenting cell (APC):T cell ratios of 1:100 or less. IL-12 augmented interferon-gamma production during CTL generation. The CTL enhancing effects of the cytokine, however, could not be blocked by neutralizing anti-interferon-gamma antibody. Together with IL-12, antigen-pulsed dendritic cells may be a useful approach for boosting CTL responses against infectious agents and malignancies.     

Potent antigen-specific immune responses stimulated by codelivery of CpG ODN and antigens in degradable microparticles

CpG ODN stimulates a TH1 response through its receptor Toll-like receptor 9 (TLR9). TLR9 is a receptor that is found intracellularly. Microparticles are efficiently internalized by dendritic cells (DCs) and macrophages and would thus be an ideal delivery vehicle for CpG ODN to reach its target site thereby enhancing the TH1 response to an antigen also encapsulated in the microparticle. Here, we show that careful control over fabrication parameters can produce biodegradable microparticles with predictable size distributions, surface morphology, and shape. Entrapment efficiencies of the model antigen OVA ranged from 19% to 23% with an average loading of 10 microg/mg of microparticles. For CpG ODN, these values were 33% to 35%, which corresponded to an average loading of 8.5 microg/mg of microparticles. The microparticles release CpG ODN and OVA in a burst followed by sustained release profile. At the highest concentration of microparticles incubated with a pure DC cell line, 92% of DCs had internalized microparticles by 16 hours, confirming that DCs efficiently take up the microparticles. Microparticles are capable of inducing DC maturation as determined by up-regulation of CD80 and CD86 markers. Although the presence of CpG ODN in the microparticles did not impact on the phenotype of the DCs, it was necessary for DCs to induce activation of antigen-specific T cells as indicated by interferon-gamma production. Microparticles entrapping both antigen and CpG ODN induced significantly higher amounts of anti-OVA antibody production than other preparations such as the soluble OVA and CpG ODN (P<0.01) and stimulated stronger IgG2a production than delivery of microparticles entrapping antigen alone. We conclude that co-encapsulating immunostimulatory CpG ODN and antigen in degradable microparticles is an effective approach to enhancing development of a TH1 immune response.     

Eosinophil-derived neurotoxin acts as an alarmin to activate the TLR2-MyD88 signal pathway in dendritic cells and enhances Th2 immune responses

Eosinophil-derived neurotoxin (EDN) is an eosinophil granule-derived secretory protein with ribonuclease and antiviral activity. We have previously shown that EDN can induce the migration and maturation of dendritic cells (DCs). Here, we report that EDN can activate myeloid DCs by triggering the Toll-like receptor (TLR)2-myeloid differentiation factor 88 signaling pathway, thus establishing EDN as an endogenous ligand of TLR2. EDN activates TLR2 independently of TLR1 or TLR6. When mice were immunized with ovalbumin (OVA) together with EDN or with EDN-treated OVA-loaded DCs, EDN enhanced OVA-specific T helper (Th)2-biased immune responses as indicated by predominant production of OVA-specific interleukin (IL)-5, IL-6, IL-10, and IL-13, as well as higher levels of immunoglobulin (Ig)G1 than IgG2a. Based on its ability to serve as a chemoattractant and activator of DCs, as well as the capacity to enhance antigen-specific immune responses, we consider EDN to have the properties of an endogenous alarmin that alerts the adaptive immune system for preferential enhancement of antigen-specific Th2 immune responses.     

Plasmacytoid dendritic cells induce NK cell-dependent, tumor antigen-specific T cell cross-priming and tumor regression in mice

A prerequisite for strong adaptive antiviral immunity is the robust initial activation of the innate immune system, which is frequently mediated by TLR-activated plasmacytoid DCs (pDCs). Natural antitumor immunity is often comparatively weak, potentially due to the lack of TLR-mediated activation signals within the tumor microenvironment. To assess whether pDCs are capable of directly facilitating effective antitumor immune responses, mice bearing established subcutaneous B16 melanoma tumors were administered TLR9-activated pDCs directly into the tumor. We found that TLR9-activated pDCs induced robust, spontaneous CTL cross-priming against multiple B16 tumor antigens, leading to the regression of both treated tumors and untreated tumors at distant contralateral sites. This T cell cross-priming was mediated by conventional DCs (cDCs) and was completely dependent upon the early recruitment and activation of NK cells at the tumor site. NK cell recruitment was mediated by CCR5 via chemokines secreted by pDCs, and optimal IFN-gamma production by NK cells was mediated by OX40L expressed by pDCs. Our data thus demonstrated that activated pDCs are capable of initiating effective and systemic antitumor immunity through the orchestration of an immune cascade involving the sequential activation of NK cells, cDCs, and CD8(+) T cells.     

Induction of cellular immune responses in patients with stage-I multiple myeloma after vaccination with autologous idiotype-pulsed dendritic cells

Idiotype vaccines have shown both biological efficacy and clinical benefit in lymphoma. Circulating idiotype proteins (Id) in multiple myeloma patients offer a suitable target for immunotherapy. So far, specific immune responses after vaccination with Ids have been evaluated mostly in advanced myeloma. We explored the potential of dendritic-cell (DC)-based immunotherapy in 9 patients with stage-I disease. Mature monocyte-derived Id-pulsed DCs and keyhole limpet hemocyanin (KLH) were administered at dose levels between 2 and 20×10? cells. Patients received 5 immunizations every 4 weeks. A median number of 6.8×10? DCs were administered per vaccination. Five out of 9 patients (56%) developed Id-specific T cells as showed in proliferation assays and 8 out of 9 patients (89%) showed specific T-cell-mediated cytokine release after Id stimulation. The cytokine-secretion did not show a distinct Th1-type or Th2-type pattern. The M protein dropped slightly in 3 out of 9 patients. We could show that DC-based Id vaccination is a feasible way of inducing specific T-cell responses in stage-I myeloma patients. Further trials are needed to increase the rate of responses and to define the role of DC-based vaccination in the era of new pharmacologic therapies.     

Induction of antigen-specific CD8+ cytotoxic T cells by dendritic cells co-electroporated with a dsRNA analogue and tumor antigen mRNA

The maturation state of dendritic cells (DCs) is an important determinant for the initiation and regulation of adaptive immune responses. In this study, we wanted to assess whether functional activation of human monocyte-derived DCs can be achieved by electroporation of an activation signal in the form of double-stranded (ds) RNA and whether simultaneous electroporation of the dsRNA with tumor antigen encoding mRNA can lead to the induction of a cytotoxic T-lymphocyte (CTL) response. Electroporation of immature DCs with poly(I:C(12)U), a dsRNA analogue, resulted in phenotypic as well as functional changes, indicative of DC maturation. Co-electroporation of DCs with both poly(I:C(12)U) and Melan-A/MART-1 encoding mRNA induced strong anti-Melan-A/MART-1 CD8(+) T-cell responses in vitro. Higher numbers of Melan-A/MART-1-specific CTLs were consistently obtained with poly(I:C(12)U)-activated DCs compared to DCs matured in the presence of an inflammatory cytokine cocktail. These results indicate that DC co-electroporation with both dsRNA and tumor antigen encoding mRNA induces fully activated and antigen-loaded DCs that promote antigen-specific CTL responses and may provide the basis for future immunotherapeutic strategies.