急性髓系白血病细胞总RNA冲击的树突细胞诱导抗自身白血病的T细胞免疫

目的探讨白血病细胞RNA冲击的完全缓解期的急性髓系白血病(AML-CR)患者骨髓单个核细胞(BMMNC)衍生的树突细胞(mRNA-DC)体外刺激自体T细胞抗白血病免疫的可行性及有效性。方法应用联合细胞因子(GM-CSF、IL-4)培养法从AML-CR患者贴壁BMMNC诱导DC,在诱导的第5天用脂质体DOTAP介导法以自体白血病细胞的总RNA冲击DC,然后以含10 ng/m l的TNF-α的培养基继续培养24 h促进其成熟,培养7 d后收获细胞,作为mRNA-DC。以流式细胞术检测DC特征性表型的表达;以MTT法测定mRNA-DC对自体T细胞的促增殖活性;将mRNA-DC与T细胞按1∶3混合,共培养7 d,收获活化的T细胞,采用酶联免疫斑点法(ELISPOT)测定分泌γ干扰素(IFN-γ)阳性细胞数;乳酸脱氢酶(LDH)释放法测定细胞毒活性。结果14例AML-CR患者BMMNC均可在体外分化为具有特征性形态和表型的成熟DC;当刺激细胞与反应细胞比例为1∶16时,mRNA-DC可刺激自体T细胞产生明显的增殖活性[(36.84±5.68)%],与未冲击DC组[(12.20±3.16)%]比较差异具有统计学意义(P<0.05,n=9);ELISPOT分析显示分泌IFN-γ的mRNA反应性的T细胞得到明显扩增;体外活化的T细胞在效靶比为20∶1时,对自体白血病细胞显示明显的杀伤活性[(45.46±6.34)%],与未冲击的DC组[(12.32±1.32)%]及单纯IL-2组[(13.26±2.28)%]比较,差异有统计学意义(P<0.05,n=5)。结论应用白血病细胞RNA冲击的DC疫苗免疫可以作为一种可行、有效的防治微量残留白血病的方法。     

Dendritic cells pulsed with RNA are potent antigen-presenting cells in vitro and in vivo

Immunization with defined tumor antigens is currently limited to a small number of cancers where candidates for tumor rejection antigens have been identified. In this study we investigated whether pulsing dendritic cells (DC) with tumor-derived RNA is an effective way to induce CTL and tumor immunity. DC pulsed with in vitro synthesized chicken ovalbumin (OVA) RNA were more effective than OVA peptide-pulsed DC in stimulating primary, OVA-specific CTL responses in vitro. DC pulsed with unfractionated RNA (total or polyA+) from OVA-expressing tumor cells were as effective as DC pulsed with OVA peptide at stimulating CTL responses. Induction of OVA-specific CTL was abrogated when polyA+ RNA from OVA-expressing cells was treated with an OVA- specific antisense oligodeoxynucleotide and RNase H, showing that sensitization of DC was indeed mediated by OVA RNA. Mice vaccinated with DC pulsed with RNA from OVA-expressing tumor cells were protected against a challenge with OVA-expressing tumor cells. In the poorly immunogenic, highly metastatic, B16/F10.9 tumor model a dramatic reduction in lung metastases was observed in mice vaccinated with DC pulsed with tumor-derived RNA (total or polyA+, but not polyA- RNA). The finding that RNA transcribed in vitro from cDNA cloned in a bacterial plasmid was highly effective in sensitizing DC shows that amplification of the antigenic content from a small number of tumor cells is feasible, thus expanding the potential use of RNA-pulsed DC- based vaccines for patients bearing very small, possibly microscopic, tumors.     

Transfected human dendritic cells to induce antitumor immunity

Dendritic cells are professional antigen-presenting cells able to prime naive T lymphocytes and regulate steadily the delicate balance between tolerance and activation during the immune response. In past years several reports have shown that genetically engineered dendritic cells (DCs) can be a powerful tool for inducing an antigen-specific immune response. The use of such modified antigen-presenting cells is a real working hypothesis in preclinical studies and in clinical vaccination approaches for cancer treatment. The definition of optimal transfection conditions for preserving DC survival and functionality is necessary to design a correct immunotherapeutic protocol. Different lipid-based transfection compounds were studied for their effects on DC survival, phenotype and functional properties. All the transfection procedures were able to select DCs with a higher expression of activation and costimulatory molecules (ie MHCII-DR, CD83, CD86, CD25) than the untreated DCs. However, only two compounds (LipofectAMINE PLUS and FuGENE 6), preserved or even increased the immunopotency of DCs as antigen-presenting cells. These protocols were applied to modify DCs in order to express an epithelial tumor-associated antigen, MUC1, and such cells were able to induce in vitro a specific immune response in healthy donors.     

Enhancement of antitumor immunity against B16 melanoma tumor using genetically modified dendritic cells to produce cytokines

Dendritic cells (DC) that have been genetically modified to express cytokine genes may be novel tools for inducing antitumor immune responses. In the present study, the pMX retroviral vector was modified to express the mouse IL-2 (mIL-2pMX) and mouse IL-12 (mIL-12pMX) genes. Supernatants from 293 cells transfected with pMX retroviral vectors were harvested and used to transduce mouse lin- bone marrow (BM) progenitor cells. After 48 h co-culture with pseudotype retrovirus, BM cells were cultured for 12 days in the presence of mGM-CSF, mSCF and mTNF-alpha to obtain a DC-enriched fraction. Flow cytometric analysis showed that GFP protein expression in these cultures was 20-40% and that 40-50% of the cultured BM cells were positive for the DC marker, DEC205. About 60% of cells sorted for DEC205 also expressed GFP. The supernatants of DC-mIL-2 and DC-mIL-12 cultured for 48 h contained 5.2 +/- 0.15 and 33.9 +/- 2.6 ng cytokine protein per milliliter, respectively. Intratumoral injection of DC-mIL-2 or DC-mIL-12 on days 8 and 15 after the intradermal injection of 1 x 105 B16F10 cells, resulted in a significant reduction in tumor size by day 21, as compared with mice treated with unmodified DC or DC-GFP. Longer term analysis as assessed at day 42 revealed that B16 tumor-bearing mice treated with cytokine gene-modified DC survived significantly longer than mice from other groups. Spleen cells obtained from DC-treated mice were specifically sensitized for the generation of CTL by subsequent restimulation with gene-modified DC. These results suggested that DC genetically modified to express IL-2 or IL-12 can induce potent antitumor responses against well-established, poorly immunogenic B16F10 tumors. Gene Therapy (2000) 7, 2113-2121.     

Induction of specific antitumor immunity in the mouse with the electrofusion product of tumor cells and dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells capable of inducing primary T-cell responses. Several immunotherapy treatment strategies involve manipulation of DCs, both in vivo and ex vivo, to promote the immunogenic presentation of tumor-associated antigens. In this study, an electrofusion protocol was developed to induce fusion between tumor cells and allogeneic bone marrow-derived DCs. Preimmunization with irradiated electrofusion product was found to provide partial to complete protection from tumor challenge in the murine Renca renal cell carcinoma model and the B16 and M3 melanoma models. Vaccinated survivors developed specific immunological memory and were able to reject a subsequent rechallenge with the same tumor cells but not a syngeneic unrelated tumor line. Antitumor protection in the B16 model was accompanied by the development of a polyclonal cytotoxic T-lymphocyte response against defined melanoma-associated antigens. The therapeutic potential of this type of approach was suggested by the ability of a Renca-DC electrofusion product to induce tumor rejection in a substantial percentage of hosts (60%) bearing pre-established tumor cells. These results indicate that treatment with electrofused tumor cells and allogeneic DCs is capable of inducing a potent antitumor response and could conceivably be applied to a wide range of cancer indications for which tumor-associated antigens have not been identified.     

Phase I/II study of vaccination with electrofused allogeneic dendritic cells/autologous tumor-derived cells in patients with stage IV renal cell carcinoma

In the present study, we assessed the feasibility, toxicity, immunologic response, and clinical efficacy of vaccination with allogeneic dendritic cell (DC)/tumor fusions in patients with metastatic renal cell carcinoma (RCC). Patients with stage IV RCC with accessible tumor lesions or independent therapeutic indications for nephrectomy were eligible for enrollment. Tumors were processed into single cell suspensions and cryopreserved. DCs were generated from adherent peripheral blood mononuclear cells isolated from normal volunteers and cultured with granulocyte macrophage colony-stimulating factor, interleukin-4, and tumor necrosis factor-alpha. DCs were fused to patient derived RCC with serial electrical pulses. Patients received up to 3 vaccinations at a fixed dose of 4x10(7) to 1x10(8) cells administered at 6-week intervals. Twenty-four patients underwent vaccination. Twenty-one and 20 patients were evaluable for immunologic and clinical response, respectively. DCs demonstrated a characteristic phenotype with prominent expression of HLA class II and costimulatory molecules. A mean fusion efficiency of 20% was observed, determined by the percent of cells coexpressing DC and tumor antigens. No evidence of significant treatment related toxicity or auto-immunity was observed. Vaccination resulted in antitumor immune responses in 10/21 evaluable patients as manifested by an increase in CD4 and/or CD8 T-cell expression of interferon-gamma after ex vivo exposure to tumor lysate. Two patients demonstrated a partial clinical response by Response Evaluation Criteria in Solid Tumors criteria and 8 patients had stabilization of their disease. Vaccination of patients with RCC with allogeneic DC/tumor fusions was feasible, well tolerated, and resulted in immunologic and clinical responses in a subset of patients.     

Current methods for loading dendritic cells with tumor antigen for the induction of antitumor immunity

The immunotherapy of cancer is predicated on the belief that it is possible to generate a clinically meaningful antitumor response that provides patient benefit, such as improvement in the time to progression or survival. Indeed, immunotherapeutics with dendritic cells (DC) as antigen-presenting delivery vehicles for cell-based vaccines have already improved patient outcome against a wide range of tumor types (1-9). This approach stimulates the patient's own antitumor immunity through the induction or enhancement of T-cell immunity. It is generally believed that the activity of cytotoxic T lymphocytes (CTL), the cells directly responsible for killing the tumor cells in vivo, are directed by DC. Therefore, the goal of many current designs for DC-based vaccines is to induce strong tumor-specific CTL responses in patients with cancer. In practice, most studies for DC-based cancer vaccine development have focused on the development of methods that can effectively deliver exogenous tumor antigens to DC for cross-priming of CD8+ T cells through the endogenous MHC class I processing and presentation pathway (10). To date, many methods have been developed or evaluated for the delivery of defined and undefined tumor antigens to DC. This review provides a brief summary on these methods, the techniques used in these methods, as well as the advantages and disadvantages of each method.     

RNA干扰抑制SOCS1表达增强树突状细胞抗肿瘤作用

目的采用RNA干扰技术抑制树突状细胞（DCs）SOCS1的表达，并检测其对树突状细胞抗肿瘤活性的影响，为树突状细胞的临床应用奠定基础。方法针对SOCS1基因，采用化学合成法合成3对SOCS1 siRNA，并转染树突状细胞。Western blot检测树突状细胞SOCS1的表达情况，筛选出有效的siRNA序列，MIT法测定SOCS1沉默的树突状细胞抗肿瘤活性的变化。结果与空白对照组相比，序列3组SOCS1蛋白质表达水平明显降低；SOCS1沉默的树突状细胞抗肿瘤活性显著提高。结论RNA干扰技术能显著下调树突状细胞SOCS1的表达，提高树突状细胞的抗肿瘤活性，为树突状细胞的临床应用提供了新的思路和手段。     

Enhancement of vaccine-mediated antitumor immunity in cancer patients after depletion of regulatory T cells

In this study, we investigated whether elimination of CD4+/CD25+ Tregs using the recombinant IL-2 diphtheria toxin conjugate DAB(389)IL-2 (also known as denileukin diftitox and ONTAK) is capable of enhancing the immunostimulatory efficacy of tumor RNA-transfected DC vaccines. We show that DAB(389)IL-2 is capable of selectively eliminating CD25-expressing Tregs from the PBMCs of cancer patients without inducing toxicity on other cellular subsets with intermediate or low expression of CD25. DAB(389)IL-2-mediated Treg depletion resulted in enhanced stimulation of proliferative and cytotoxic T cell responses in vitro but only when DAB(389)IL-2 was omitted during T cell priming. DAB(389)IL-2 significantly reduced the number of Tregs present in the peripheral blood of metastatic renal cell carcinoma (RCC) patients and abrogated Treg-mediated immunosuppressive activity in vivo. Moreover, DAB(389)IL-2-mediated elimination of Tregs followed by vaccination with RNA-transfected DCs significantly improved the stimulation of tumor-specific T cell responses in RCC patients when compared with vaccination alone. Our findings may have implications in the design of immune-based strategies that may incorporate the Treg depletion strategy to achieve potent antitumor immunity with therapeutic impact.     

Dendritic cells transduced with HSV-1 amplicons expressing prostate-specific antigen generate antitumor immunity in mice

There is currently much interest in generating cytotoxic T lymphocyte (CTL) responses against tumor antigens as a therapy for cancer. This work describes a novel gene transfer technique utilizing dendritic cells (DCs), an extremely potent form of antigen-presenting cell (APC), and herpes simplex virus-1 (HSV-1) amplicons. HSV-1 amplicons are plasmid-based viral vectors that are packaged into HSV-1 capsids, but lack viral coding sequences. Amplicon vectors have been constructed that encode the model tumor antigen ovalbumin (HSV-OVA) and human prostate-specific antigen (HSV-PSA), a protein that is expressed specifically in prostate epithelium and prostate carcinoma cells. These amplicons were packaged using a helper virus-free system that produces vector stocks that are devoid of contaminating cytotoxic helper virus. Transduction of DCs with HSV-OVA or HSV-PSA and co-culture with CTL hybridomas results in specific activation, indicating that transduced DCs express these transgenes and process the tumor antigens for class I MHC presentation to CTL. Mice immunized with HSV-PSA-transduced DCs generate a specific CTL response that can be detected in vitro by a (51)Cr-release assay and are protected from challenge with tumors that express PSA. These results indicate that DCs transduced with HSV-1 amplicon vectors may provide a tool for investigation of the biology of CTL activation by DCs and a new modality for immunotherapy of cancer.     

Identification of antigen-presenting dendritic cells in mouse aorta and cardiac valves

Presumptive dendritic cells (DCs) bearing the CD11c integrin and other markers have previously been identified in normal mouse and human aorta. We used CD11c promoter–enhanced yellow fluorescent protein (EYFP) transgenic mice to visualize aortic DCs and study their antigen-presenting capacity. Stellate EYFP⁺ cells were readily identified in the aorta and could be double labeled with antibodies to CD11c and antigen-presenting major histocompatability complex (MHC) II products. The DCs proved to be particularly abundant in the cardiac valves and aortic sinus. In all aortic locations, the CD11c⁺ cells localized to the subintimal space with occasional processes probing the vascular lumen. Aortic DCs expressed little CD40 but expressed low levels of CD1d, CD80, and CD86. In studies of antigen presentation, DCs selected on the basis of EYFP expression or binding of anti-CD11c antibody were as effective as DCs similarly selected from the spleen. In particular, the aortic DCs could cross-present two different protein antigens on MHC class I to CD8⁺ TCR transgenic T cells. In addition, after intravenous injection, aortic DCs could capture anti-CD11c antibody and cross-present ovalbumin to T cells. These results indicate that bona fide DCs are a constituent of the normal aorta and cardiac valves.Inflammation is a component of many vascular disorders such as aortic aneurysm, giant cell arteritis, Takayasu’s disease, and atherosclerosis (1–4). DCs carry out many innate responses and orchestrate adaptive immunity (5). It is therefore important to assess the presence and properties of DCs in major blood vessels.Initially, electron microscopy and labeling for several intracellular markers were used to demonstrate DCs in human aorta, primarily in a subendothelial location (6–9). Ma-Krupa et al. (10) and Pryshchep et al. (11) then used more cell-restricted markers to identify DCs in increased numbers in human arteries, whereas Bobryshev (12) reported increased numbers of cells expressing S100, CD1a, and p55 markers in the intima and adventitia during atherosclerosis. Cells bearing the CD11c integrin, which is characteristically expressed at high levels on DCs, were also identified in the normal aortic intima and in atherosclerosis-prone areas in mice (13, 14). The numbers of aortic CD11c⁺ cells increased with aging and atherosclerosis through a recruitment process involving CX3CR1 chemokine receptor and VCAM-1 (13, 15, 16).Although abundant CD11c expression is a well-known marker for DCs, other cell types can express moderate levels of CD11c, including activated NK cells, some macrophages, and even some T cells (17–21). Therefore, additional criteria are required to identify DCs in the vascular wall in the steady state and ultimately disease, particularly the capacity of DCs to express MHC class II and present antigens to T lymphocytes.In this study, we found that the CD11c promoter–enhanced yellow fluorescent protein (EYFP) transgenic mouse developed by Lindquist et al. (22) is valuable to identify and study CD11c⁺ cells from the normal mouse aorta. We will report on the location, cell surface markers, and antigen-presenting functions of DCs and also describe their abundance in all of the cardiac valves.     

Vaccination of patients with metastatic renal cell carcinoma with autologous dendritic cells pulsed with autologous tumor antigens in combination with interleukin-2: a phase 1 study

Dendritic cells (DC) have been recognized as the most potent antigen presenting cells (APC) of the immune system. We performed a phase 1 study in twelve patients with metastatic renal cell carcinoma (RCC) using autologous immature DC loaded with autologous tumorlysate (TuLy) as a vaccine based on our earlier in vitro observations that such DC can activate tumor-specific cytotoxic T-lymphocytes. The treatment was combined with low-dose interleukin (IL)-2, as this has shown benefit in DC-based therapies. Patients received three intradermal vaccinations at two weekly intervals, and, after each vaccination, IL-2 was administered for 5 consecutive days. In six patients, keyhole-limpet hemocyanin (KLH) was added to the DC culture for immunologic monitoring purposes. In general, DC phenotype was CD14(low), CD86(high), CD40(high), CD80(low), and CD83(low). We noticed that the number of CD14+ cultured DC increased during treatment. Nevertheless, ovalbumin uptake remained high, underlining that these cells were still functional immature DC. The vaccine was able to elicit cellular anti-KLH responses, emphasizing the ability of the injected DC to mount an immunologic response. However, proliferative responses against TuLy were not detected, and humoral responses against TuLy or KLH were absent. Objective clinical responses were not observed, but extended stable disease was noted. The absence of cellular, humoral, or clinical antitumor responses suggests that the vaccination strategy with immature DC has little benefit for patients with advanced RCC. Nevertheless, this study shows the feasibility of a completely autologous DC and tissue culture methodology for the generation of TuLy pulsed DC.     

Allogeneic melanoma vaccine expressing alphaGal epitopes induces antitumor immunity to autologous antigens in mice without signs of toxicity

Owing to the absence of alphaGal epitopes in human cells and constant stimulation of the immune system by the symbiotic bacterial flora, humans develop high titers of natural antibodies against these epitopes. It has been demonstrated that syngeneic whole cell vaccines modified to express alphaGal epitopes could be used to generate a potent anticancer vaccine. In this study, we tested whether allogeneic whole cell cancer vaccines modified to express alphaGal epitopes would be effective for the treatment of murine melanoma. The alpha(1,3)galactosyltransferase (alphaGT) knockout mice (H-2) with preexisting subcutaneous and pulmonary tumors [alphaGal B16, H-2] received therapeutic vaccinations with S91M3alphaGal (H-2) whole cell allogeneic vaccines. These mice had better survival and reduced pulmonary metastasis burden compared with control mice treated with S91M3 vaccine cells. Vaccination with S91M3alphaGal-induced cytotoxic CD8 T cells recognizing the syngeneic alphaGal B16 tumors measured by adoptive transfer to recipients bearing pulmonary metastases. The presence of allo-antigens did not dominate the induction of immunity to "cryptic" tumor antigens and had helped in the generation of a more efficient vaccine to treat preexisting tumors when compared with classic autologous vaccines. Vaccination with allogeneic alphaGal vaccines did not induce signs of toxicity including changes in weight, hematology, chemistry, and histopathology of major perfused organs or autoimmunity in long-term murine models for breast, lung, and melanoma. This study established the safety and efficacy data of allogeneic alphaGal whole cell vaccines and constituted the basis for the initiation of human clinical trials to treat human malignancies.     

An iPSC-derived exosome-pulsed dendritic cell vaccine boosts antitumor immunity in melanoma

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Immunotherapy using autologous monocyte-derived dendritic cells pulsed with leukemic cell lysates for acute myeloid leukemia relapse after autologous peripheral blood stem cell transplantation

Although a second stem cell transplantation (SCT) can be used as salvage therapy in patients with relapsing leukemia after SCT, most of these patients have a poor outcome. We tried clinical vaccination using monocyte-derived dendritic cells (DCs) pulsed with leukemic lysates to treat relapsing acute myeloid leukemia (AML) after autologous SCT. To generate DCs, CD14+ cells isolated from peripheral blood stem cell products were cultured in AIM-V in the presence of GM-CSF and IL-4. Adding TNF-alpha on day 6 induced maturation of the DCs, which were harvested on day 8 or 9. The DCs were incubated with tumor lysate and KLH for 2 hr at 37 degrees C. After certifying the absence of microorganisms and endotoxins, the patients received four DC vaccinations at two- to three-week intervals. Two patients received four DC vaccinations with means of 7.8 x 10(6) and 9 x 10(6) DCs at two- to three-week intervals. The DC vaccinations were well tolerated with no apparent side effects. After the vaccinations, the patients showed immunological responses with positive delayed-type hypersensitivity skin reaction and increasing autologous T cells stimulatory capacity to the DCs; however, the BM blast percentage of the patients did not improve. The results suggest that DCs are a feasible cellular therapy for relapsing AML after autologous SCT.     

Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity

The success of clinically relevant immunotherapies requires reversing tumor-induced immunosuppression. Here we demonstrated that linear polyethylenimine-based (PEI-based) nanoparticles encapsulating siRNA were preferentially and avidly engulfed by regulatory DCs expressing CD11c and programmed cell death 1–ligand 1 (PD-L1) at ovarian cancer locations in mice. PEI-siRNA uptake transformed these DCs from immunosuppressive cells to efficient antigen-presenting cells that activated tumor-reactive lymphocytes and exerted direct tumoricidal activity, both in vivo and in situ. PEI triggered robust and selective TLR5 activation in vitro and elicited the production of hallmark TLR5-inducible cytokines in WT mice, but not in Tlr5^–/– littermates. Thus, PEI is a TLR5 agonist that, to our knowledge, was not previously recognized. In addition, PEI-complexed nontargeting siRNA oligonucleotides stimulated TLR3 and TLR7. The nonspecific activation of multiple TLRs (specifically, TLR5 and TLR7) reversed the tolerogenic phenotype of human and mouse ovarian tumor–associated DCs. In ovarian carcinoma–bearing mice, this induced T cell–mediated tumor regression and prolonged survival in a manner dependent upon myeloid differentiation primary response gene 88 (MyD88; i.e., independent of TLR3). Furthermore, gene-specific siRNA-PEI nanocomplexes that silenced immunosuppressive molecules on mouse tumor-associated DCs elicited discernibly superior antitumor immunity and enhanced therapeutic effects compared with nontargeting siRNA-PEI nanocomplexes. Our results demonstrate that the intrinsic TLR5 and TLR7 stimulation of siRNA-PEI nanoparticles synergizes with the gene-specific silencing activity of siRNA to transform tumor-infiltrating regulatory DCs into DCs capable of promoting therapeutic antitumor immunity.     

Inhibitory effect of RNA pool complexity on stimulatory capacity of RNA-pulsed dendritic cells

Tumor cells that show downregulation of their tumor-associated antigens (TAAs) may be able to escape immune-mediated elimination. Therefore, efficient vaccine strategies attempt to target multiple TAAs simultaneously. This is easily achieved in dendritic cell (DC)-based vaccines by introducing antigens in the form of RNA. Although insufficient message may hinder adequate expression of individual TAAs when using total-tumor RNA, high amounts of individual RNAs as pools yield DCs presenting high numbers of specific peptide-major histocompatibility complex ligands with epitopes derived from different TAAs. We used the transfer of RNAs encoding the well-defined melanoma TAAs tyrosinase, Melan-A, CDK4mut, gp100, SNRP116mut, and GPNMBmut to characterize DCs at the levels of transfected RNA, expressed protein and peptide-major histocompatibility complex ligand presentation. TAA-encoding RNA was rapidly degraded in the DCs, allowing only a single surge in protein expression shortly after transfection. We compared the functional capacity of DCs transfected with pools of 3 versus 6 RNAs. Whereas functional assays demonstrated a decrease in stimulatory capacity of DCs transfected with a pool of 3 RNAs by only 30% as compared with single RNAs, a 60% loss was seen with 6 RNAs. We conclude that larger RNA pools result in diminished presentation of individual epitopes and suggest that smaller pools of RNA be transfected into separate DC populations which are then pooled to create multiplex vaccines.     

Enhanced antitumor immunity in mice deficient in CD69

We investigated the in vivo role of CD69 by analyzing the susceptibility of CD69-/- mice to tumors. CD69-/- mice challenged with MHC class I- tumors (RMA-S and RM-1) showed greatly reduced tumor growth and prolonged survival compared with wild-type (WT) mice. The enhanced anti-tumor response was NK cell and T lymphocyte-mediated, and was due, at least in part, to an increase in local lymphocytes. Resistance of CD69-/- mice to MHC class I- tumor growth was also associated with increased production of the chemokine MCP-1, diminished TGF-beta production, and decreased lymphocyte apoptosis. Moreover, the in vivo blockade of TGF-beta in WT mice resulted in enhanced anti-tumor response. In addition, CD69 engagement induced NK and T cell production of TGF-beta, directly linking CD69 signaling to TGF-beta regulation. Furthermore, anti-CD69 antibody treatment in WT mice induced a specific down-regulation in CD69 expression that resulted in augmented anti-tumor response. These data unmask a novel role for CD69 as a negative regulator of anti-tumor responses and show the possibility of a novel approach for the therapy of tumors.     

Intratumoral administration of adenoviral interleukin 7 gene-modified dendritic cells augments specific antitumor immunity and achieves tumor eradication

In two murine lung cancer models adenoviral interleukin 7-transduced dendritic cells (DC-AdIL-7) were administered intratumorally, resulting in complete tumor regression. Intratumoral DC-AdIL-7 therapy was as effective as DCs pulsed with specific tumor peptide antigens. Comparison with other intratumoral therapies including recombinant IL-7, AdIL-7 vector alone, unmodified DCs, IL-7-transduced fibroblasts, or DCs pulsed with tumor lysates revealed DC-AdIL-7 therapy to be superior in achieving antitumor responses and augmenting immunogenicity. Mice with complete tumor eradication as a result of either DC-AdIL-7 or AdIL-7 therapy were rechallenged with parental tumor cells 30 days or more after complete tumor eradication. All the DC-AdIL-7-treated mice completely rejected a secondary rechallenge, whereas the AdIL-7-treated mice had sustained antitumor effects in only 20-25% of the mice. DC-AdIL-7 therapy was more effective than AdIL-7 in achieving systemic antitumor responses and enhancing immunogenicity. After complete tumor eradication, those mice treated with DC-AdIL-7 evidenced significantly greater release of splenocyte GM-CSF and IFN-gamma than did controls or AdIL-7-treated mice. After intratumoral injection, gene-modified DCs trafficked from the tumor to lymph node sites and spleen. DCs were detected in nodal tissues for up to 7 days after intratumoral injection. We report that intratumoral DC-AdIL-7 leads to significant systemic immune responses and potent antitumor effects in murine lung cancer models.