K562细胞可溶性抗原负载树突状细胞体外诱导CTL作用的研究

目的探讨经K562细胞裂解物冲击致敏的外周血单个核细胞衍生的树突状细胞（DC）的生物特性及体外诱导抗原特异性CTL应答的能力。方法采集健康人抗凝外周血分离单个核细胞，贴壁细胞用含rhGM—CSF、rhIL-4、TNF—α的RPM1640＋10％FBS培养基体外诱导培养产生DC，5天收获细胞并将细胞分组：A组：未负载抗原DC；B组：加入K562细胞裂解液脉冲DC。7天后用流式细胞仪检测成熟DC免疫表型，并将非贴壁细胞（淋巴细胞）作为效应细胞与各组DE共育，以产生细胞毒性T淋巴细胞（CTL）。12天用LDH释放试验测定对K562细胞的杀伤活性。并用ELISA方法测定细胞上清液中IL-12的含量。结果（1）经细胞因子联合体外诱导的各组DC较培养前在数量，形态及免疫表型上差异有统计学意义，CD86、CD83、CD40、CD1a表达增加，其中经K562细胞裂解液冲击的DC的CD83CD86表达率明显升高。（2）效应细胞与K562细胞混合培养时，负载K562细胞裂解液的DC刺激后的T细胞比单独DC刺激后的T细胞对K562细胞的杀伤作用更明显。（3）负载K562细胞裂解液的DC细胞培养上清液中产生IL-12含量较未负载抗原的DC明显增加。结论用GM—CSF、IL-4以及TNF—α诱导培养健康人外周血单个核细胞可以得到成熟的DC，且经K562细胞裂解液致敏可以进一步促进DC的成熟并体外诱导特异性杀伤靶细胞的CTL。     

Activation of autologous leukemia-specific T cells in acute myeloid leukemia: monocyte-derived dendritic cells cocultured with leukemic blasts compared with leukemia-derived dendritic cells

In acute myeloid leukemia (AML) blasts can be differentiated into dendritic cell (DC) like cells (AML-DC). These cells have a mature DC-like phenotype, are strong stimulators in mixed leukocyte reactions and can be used to generate leukemia-specific cytotoxic T cells. However, recent reports about naturally existing leukemic DC with immunoregulatory dysfunctions in peripheral blood of AML patients caused concerns about the use of AML-DC for therapeutic purposes. Systematic intra-individual comparisons between AML-DC and non-leukemic DC derived from monocytes (MoDC) in AML patients are missing. Thus, we investigated the ability to generate MoDC from peripheral blood of 17 AML patients in first remission and their functional integrity to stimulate leukemia-specific T cells by simple coculture with leukemic blasts. Phenotypic analysis of AML-DC and MoDC from the same individual patients revealed that MoDC exhibit a more homogenous mature DC phenotype. Additionally, functional analysis demonstrated the ability of remission MoDC to activate autologous leukemia-specific T cells in 11 of 12 patients, whereas AML-DC led to a specific T cell activation in four of eight patients. The presented findings might have impact on the design of further therapeutic studies using autologous antigen-presenting cells.     

Indoleamine 2,3-dioxygenase-expressing leukemic dendritic cells impair a leukemia-specific immune response by inducing potent T regulatory cells

Background

The immunoregulatory enzyme indoleamine 2,3-dioxygenase, which catalyzes the conversion of tryptophan into kynurenine, is expressed in a significant subset of patients with acute myeloid leukemia, resulting in the inhibition of T-cell proliferation and the induction of regulatory T cells. Acute myeloid leukemia cells can be differentiated into dendritic cells, which have increased immunogenicity and have been proposed as vaccines against leukemia.

Design and Methods

Leukemic dendritic cells were generated from acute myeloid leukemia cells and used as stimulators in functional assays, including the induction of regulatory T cells. Indoleamine 2,3-dioxygenase expression in leukemic dendritic cells was evaluated at molecular, protein and enzymatic levels.

Results

We demonstrate that, after differentiation into dendritic cells, both indoleamine 2,3-dioxygenase-negative and indoleamine 2,3-dioxygenase-positive acute myeloid leukemia samples show induction and up-regulation of indoleamine 2,3-dioxygenase gene and protein, respectively. Indoleamine 2,3-dioxygenase-positive acute myeloid leukemia dendritic cells catabolize tryptophan into kynurenine metabolite and inhibit T-cell proliferation through an indoleamine 2,3-dioxygenase-dependent mechanism. Moreover, indoleamine 2,3-dioxygenase-positive leukemic dendritic cells increase the number of allogeneic and autologous CD4⁺CD25⁺ Foxp3⁺ T cells and this effect is completely abrogated by the indoleamine 2,3-dioxygenase-inhibitor, 1-methyl tryptophan. Purified CD4⁺CD25⁺ T cells obtained from co-culture with indoleamine 2,3-dioxygenase-positive leukemic dendritic cells act as regulatory T cells as they inhibit naive T-cell proliferation and impair the complete maturation of normal dendritic cells. Importantly, leukemic dendritic cell-induced regulatory T cells are capable of in vitro suppression of a leukemia-specific T cell-mediated immune response, directed against the leukemia-associated antigen, Wilms’ tumor protein.

Conclusions

These data identify indoleamine 2,3-dioxygenase-mediated catabolism as a tolerogenic mechanism exerted by leukemic dendritic cells and have clinical implications for the use of these cells for active immunotherapy of leukemia.     

Effects of cytotoxic T lymphocytes on hepatoma cell line SMMC-7721 induced by different subsets of dendritic cells in vitro

BACKGROUND: Dendritic cells (DCs) loaded with complex antigen are always used to induce cytotoxic T lymphocytes (CTLs) which have a specific anti-tumor activity. However, CTLs can assault autologous cells induced by DCs loaded with autologous antigen. This study aimed to explore how to weaken the autoimmune reaction induced by DC vaccine by combining mature DC (mDC) activating immunity and immature DC (imDC) leading to immune tolerance to make hepatocellular carcinoma (HCC) vaccine in vitro. METHODS: DC progenitors derived from human peripheral blood were assigned to two groups. One was cultured to mDC and pulsed with frozen-thawed antigen (FTA) of human HCC cell line SMMC-7721 cells (mDC group), and the other was cultured to imDC and pulsed with FTA of human liver cell line L-02 cells (imDC group). The morphology of DCs was monitored and cells phenotypes including HLA-DR, CD80, CD1α, CD83 were assayed by flowcytometry (FCM). The concentrations of interleukin-12 (IL-12) in the supernatant were assayed by ELISA. Methyl thiazolyl tetrazolium (MTT) was used to evaluate T cell proliferation induced by mDC and imDC and the killing rate of CTL induced by mDC and imDC respectively/together on SMMC-7721 and L-02 cells. RESULTS: Compared with the imDC group, the mDC group was characterized by the following: increased secretion of IL-12 (P<0.05); higher expression of HLA-DR, CDla, CD80, CD83; and stronger activity in stimulating proliferation of isogenic T cells (P<0.05). CTL induced by the mDC group had a significant killing response to SMMC-7721 as well as a higher killing rate for L-02 (P>0.05). CTL induced by mDC and imDC together had a higher killing response to SMMC-7721, but a lower killing rate for L-02(P<0.01). CONCLUSIONS: CTL induced by mDC and imDC together has a higher antigen-specific killing response in vitro than that induced by mDC alone. This may be of greater clinical value.     

Induction of myeloma-specific cytotoxic T cells using dendritic cells transfected with tumor-derived RNA

Current immunotherapeutic trials for patients with multiple myeloma (MM) focus on the idiotype (Id) as a tumor-specific antigen for active immunization. To bypass the need for the identification of shared MM-associated antigens and the characterization of possible immunogenic T-cell epitopes in a human leukocyte antigen (HLA) type-restricted manner, we focused on myeloma RNA transfection of dendritic cells (DCs). Total RNA encodes the whole antigen content of tumor cells, therefore allowing the transfected DCs to process and present the most relevant peptides and to induce a possible polyclonal cytotoxic T lymphocyte (CTL) response against different immunogenic antigens. We transfected monocyte-derived DCs with total RNA from the myeloma cell lines LP-1 and U266 by electroporation and investigated the potential of these DCs to induce myeloma-specific CTLs. We show that RNA-transfected DCs induce CTLs that lyse the LP-1 and U266 myeloma cells in an antigen-specific and major histocompatibility complex (MHC) class I-restricted manner, as demonstrated by cold-target inhibition and antibody-blocking studies. Interestingly, LP-1-specific CTLs showed no specificity for the idiotype. Consistent with studies demonstrating mucin 1 (MUC1) as a myeloma-associated antigen, we found MUC1 specificity of the CTLs induced with U266-derived RNA. As corresponding epitopes, we tested the described peptides M1.1 and M1.2 and found a striking fine specificity for M1.2, assuming a possible immunodominance of this peptide. This is the first report on the induction of myeloma-specific CTLs by RNA transfection of DCs.     

An unusual case of CD4+ CD7+ CD56+ acute leukemia with overlapping features of type 2 dendritic cell (DC2) and myeloid/NK cell precursor acute leukemia

Type 2 dendritic cell (DC2) acute leukemia has been recently described. We report here an unusual case of a 17-yr-old adolescent with overlapping features of DC2 and myeloid/NK cell precursor acute leukemia as defined by Suzuki et al. The patient presented with lymphadenopathy and hepatosplenomegaly without extranodal manifestations in skin or elsewhere. The morphologic, cytochemical and immunophenotypic features were compatible with those described in DC2 acute leukemia, with co-expression of CD4, CD56 and CD123 antigens. The novel markers BDCA-4 and BDCA-2 considered specific for DC2s were co-expressed. However, bright CD7 positivity along with a dim expression of CD33 (57%) and CD117 (27%) were also noted. Additionally, there was bright expression of NG2 monoclonal antibody 7.1, a frequent finding in myeloid/NK cell precursor acute leukemia. The interpretation of the immunophenotypic profile leads to the hypothesis on the existence of borderline cases between DC2 and myeloid/NK cell precursor acute leukemia. Still, other hypotheses can not be overlooked, such as the possibility for a kind of variant monoblastic leukemia or of another rare entity of acute unclassified leukemia.     

Ex vivo generation of human cytomegalovirus-specific cytotoxic T cells by peptide-pulsed dendritic cells

Adoptive transfer of donor-derived human cytomegalovirus (HCMV)-specific T-cell clones can restore protective immunity after stem cell transplantation. Ex vivo induction of HCMV-specific T cells using HCMV-infected fibroblasts as stimulator cells confines this approach to HCMV-seropositive donors and requires the presence of infectious virus during the stimulation procedure. In this study, we describe a potential alternative strategy to generate HCMV-specific T cells ex vivo for adoptive immunotherapy. Generation of HCMV-specific cytotoxic T lymphocytes (CTLs) ex vivo was investigated using peptide-pulsed dendritic cells as antigen-presenting cells. HCMV-specific T cells were generated and sufficiently expanded for adoptive immunotherapy in 6 out of 14 HCMV-seropositive and 2 out of 11 HCMV-seronegative donors. The CTLs recognized HCMV-infected autologous fibroblasts. No lysis was observed with either non-infected autologous or HLA-mismatched infected fibroblasts. Staining with tetrameric HLA/peptide complexes revealed significant enrichment for peptide-specific T cells of up to 28% and > 90% of CD8(+) T cells after three and five specific stimulations respectively. In addition, the expansion rates indicated that ex vivo generation of > 1 x 10(9) HCMV-specific T cells was possible after 6--7 weeks when cultures were initiated with 1--5 x 10(6) responder cells. Thus, the approach with peptide-pulsed DCs to generate HCMV-specific CTLs is feasible for clinical application after allogeneic stem cell transplantation.     

Generation of hepatitis C virus-specific cytotoxic T lymphocytes from healthy individuals with peptide-pulsed dendritic cells

BACKGROUND AND AIMS: In hepatitis C virus (HCV) infection, cytotoxic T lymphocytes (CTL) are involved in liver inflammation and contribute to the reduction of viral load. Antibodies for HCV-CTL precursor frequencies (CTLpf) are relatively low in chronic hepatitis C, and this may be related to the poor CTL response in vivo. The aim of this study was to assess the efficacy of dendritic cells (DC) as antigen-presenting cells in CTL generation from low CTLpf. METHODS: To confirm the rationale of using DC to prime naive T cells, five HCV-uninfected individuals were enrolled in the study. We obtained DC by maturation from peripheral progenitors under stimulation with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-4 and IL-1alpha. Autologous T cells were cultured with DC or concanavalin-A-induced blasts loaded with four HCV-derived peptides bearing human leukocyte antigen (HLA)-A*0201 or -A24 motifs for 28 days under IL-7 and IL-2 stimulation. The lytic activity against peptide-pulsed targets was assessed by using a [51Cr]-releasing assay. RESULTS: The DC strongly expressed HLA class I, II, B7-1 and B7-2, but not phenotypic markers of T-, B-, natural killer (NK)-cells or monocytes. The CD8-positive, HLA-class I-restricted and HCV peptide-specific CTL were generated with DC from HLA-A antigen-matched subjects, whereas no CTL activity was detected with concavalin (Con-A) blasts. We were thus able to generate HCV specific CTL from naive precursors with peptide-pulsed DC. CONCLUSIONS: This DC-based system can be used to generate CTL of desired antigen specificity, even from a source with low CTLpf.     

胰腺癌细胞总RNA转染树突细胞诱导特异性CTL能力的体外研究

目的观察人胰腺癌Mia Pa Ca-2细胞总RNA电转染树突细胞(Dendritic Cell,DC)体外激发抗原特异性细胞毒T淋巴细胞(Cytotoxic T Lymphocyte,CTL)的能力。方法自6例胰腺癌患者外周血单核细胞中分离、培养DC。使用电穿孔法将Mia Pa Ca-2细胞总RNA体外转录和PCR扩增的MUC1m RNA转染DC,以未负载抗原的DC为对照。采用实时定量PCR技术检测各组DC中MUC1表达。四甲基偶氮唑盐(MTT)检测转染各组DC存活率变化;混合细胞培养法评价各组DC体外刺激自体T淋巴细胞增殖能力;ELISA法检测各组DC体外激发抗原特异性CTL细胞因子释放量。结果 Mia Pa Ca-2总RNA与MUC1 m RNA分别转染后48 h DC中目标抗原的相对表达量分别为37.24±3.17和34.53±2.02,两者比较无显著差异(P0.05)。电转染后96 h Mia Pa Ca-2总RNA转染组DC存活率降至60.81%,低于MUC1 m RNA单转染时DC的存活率(80%左右)(P0.05)。转染Mia Pa Ca-2总RNA DC刺激自体T细胞增殖指数为8 432±611.25,显著高于MUC1单独转染组3 664±305.17(P0.05);且转染Mia Pa Ca-2总RNA DC激发特异性CTL分泌IL-2、IL-10、Granzyme B、IFN-γ水平亦显著高于MUC1 m RNA单独转染组(P0.05)。结论胰腺癌肿瘤细胞总RNA转染的DC较单一胰腺癌相关抗原负载DC有更强的体外抗原特异性CTL激发能力。     

HBcAg-pulsed dendritic cell vaccine induces Th1 polarization and production of hepatitis B virus-specific cytotoxic T lymphocytes

Aim:  Dendritic cells (DCs) pulsed with HBsAg efficiently reverse the immune tolerance to hepatitis B virus (HBV) and induce HBV-specific cytotoxic T lymphocyte (CTL) responses in transgenic mice and healthy volunteers. However, it is not clear whether HBV core antigen (HBcAg)-pulsed DCs can effectively induce CD4⁺ helper T cells polarization into Th1, which contribute to the induction and maintenance of HBV-specific CD8⁺ T cells in chronic hepatitis B (CHB) patients. To address this issue, we conducted this study and investigated whether HBcAg-pulsed DCs could polarize Th1 cells and induce an HBcAg-specific CTL response.
Methods:  HBcAg-pulsed DCs were generated from 21 CHB patients. The capacity of the HBcAg-pulsed DC vaccine to stimulate CD4⁺ and CD8⁺ T cells to produce IFN-γ and IL-4 was estimated by intercellular cytokine staining, and the HBcAg-pulsed DCs derived from 10 humam leucocyte antigen (HLA)-A2⁺ CHB patients were tested for the induction of HBV-specific CTLs from autologous T cells by pentamer staining. The cytotoxicity of these CTLs was evaluated in vitro by flow cytometry.
Results:  The HBcAg-pulsed DCs derived from CHB patients exhibited a stronger capacity to stimulate autologous CD4⁺ and CD8⁺ T cells to release IFN-γ rather than IL-4, which could induce HBV core 18-27 specific CTLs, suggesting a specific cytotoxicity against T2 cells that had been loaded with the HBV core 18-27 peptide in vitro .
Conclusion:  HBcAg-pulsed DC vaccine derived from CHB patients efficiently induced autologous T cell polarization to Th1 and generation of HBV core 18-27 specific CTLs.     

Recognition of chronic myelogenous leukaemia cells by autologous T lymphocytes primed in vitro against the patient's dendritic cells

Defects in immune responses are common in patients with chronic myelogenous leukaemia (CML). However, using dendritic cells (DCs) to promote T-cell immunity in vitro may nonetheless elicit potent specific anti-tumour responses for use in immunotherapy. Here, we show that DCs generated from CML patients had a typical dendritic phenotype and were able to stimulate autologous T cells. Three primed T-cell lines were studied in more detail in one patient. They were stimulated by autologous CML cells, but not by normal non-leukaemic cells from the patient's HLA-identical sibling. This was blocked by HLA-DR-specific, but not HLA-DQ- or HLA-DP-specific antibodies. CML-stimulated cytokine secretion, including interferon-gamma and granulocyte macrophage-colony stimulating factor, suggested a Th1-type phenotype for these sensitized anti-leukaemic T cells. This study therefore shows that cells with a functional dendritic phenotype can be generated from the blood of CML patients and are potent inducers of T-cell responses to tumour cells. This approach allows sensitization of patients' T cells by their own particular tumour without the need to identify the exact leukaemia antigens involved, and may find application in immunotherapy of CML.     

Calcium ionophore: a single reagent for the differentiation of primary human acute myelogenous leukaemia cells towards dendritic cells

Blood monocytes and CD34(+) haemopoietic progenitor cells, as well as certain leukaemic cell lines, acquire characteristics of mature dendritic cells (DC) after stimulation with calcium ionophore (CI). We studied whether the in vitro treatment of primary human acute myelogenous leukaemia (AML) cells with CI leads to differentiation towards DC. Blast cells derived from nine AML patients were cultured in the presence of either CI or an established differentiation cocktail consisting of granulocyte-macrophage colony-stimulating factor plus interleukin 4 and tumour necrosis factor-alpha for 5-7 d. Microscopic examination revealed that under both conditions, AML cells were shifted along the DC pathway. In seven out of nine cases, CI-cultivation led to a higher proportion of cells with dendritic morphology. The percentage of CD40 and CD86 expressing cells was significantly increased upon CI treatment compared with cytokine-cultured cells. DC molecules as CD80 and CD83 were up-regulated upon calcium mobilization of AML cells in four out of nine samples. In four cases, CI-treated stimulator cells induced an enhanced proliferative allogeneic T-cell response compared with cytokine-treated stimulator cells. In conclusion, these data demonstrate that CI treatment is an alternative in vitro strategy to differentiate human AML cells into DC.     

体外诱导白血病源性树突状细胞及其对T细胞杀伤活性影响的研究

目的 :探讨体外培养白血病源性树突状细胞 (DC)及其对T细胞杀伤活性的影响。方法 :从慢性髓细胞性白血病 (CML)患者外周血中分离单个核细胞 ,加入 1× 10 6U/L粒 巨噬细胞集落刺激因子 (GM CSF)、1×10 6U/L白细胞介素 (IL) 4和 5 0× 10 3 U/L肿瘤坏死因子 (TNF α) ,每 3～ 4天换液 1次 ,连续培养 14天 ,获得DC。取外周血单个核细胞加入 5 0 0× 10 3 U/LIL 2 ,培养至第 7天 ,把细胞分成两组 ,其中一组加入培养的DC ,两组细胞继续培养 3～ 4天 ,然后测定T细胞杀伤活性。结果 :DC具有典型的树状突起 ,高表达CD1a,具有慢粒特异性染色体t(9;2 2 ) ,能增强T细胞对白血病细胞的杀伤活性。结论 :在体外利用细胞因子可以把CML细胞诱导分化成具有刺激T细胞产生细胞毒性反应的白血病源性DC。     

胃腺癌BGC-823细胞总RNA转染人树突状细胞分泌exosomes的抗肿瘤效应研究

目的研究人外周血树突状细胞（DC）体外经人胃腺癌BGC-823细胞系总RNA转染后,提取培养上清液中DC分泌的外泌体（exosomes）,诱导出特异性抗胃癌效应。方法分离外周血单核细胞,经GM-CSF、IL-4培养5d后,获得未成熟DC（imDC）;体外以脂质体转染BGC-823细胞总RNA。第7天收集上清,利用超速离心法提取exosomes。分别将DC以及exosomes与T淋巴细胞共培养3d,获得细胞毒T淋巴细胞（CTL）,检测CTL对BGC-823细胞的杀伤作用。结果与未转染组相比,转染BGC-823总RNADC来源的exosomes明显促进T细胞对BGC-823的杀伤活性（P〈0．05）。结论应用BGC-823总RNA转染DC分泌exosomes能够诱导出强烈的抗肿瘤免疫反应。     

Blood donor derived dendritic cells and cytotoxic T cells for specific fusion-gene adoptive immunotherapy

BACKGROUND AND OBJECTIVES: Therapeutic immunological reagents tailored to individual patients have been shown to be a viable treatment strategy for some forms of leukaemia. This work investigates the possibility of using blood donations as a source of leukaemia-specific immune therapeutics. MATERIALS AND METHODS: The acute promyelocytic cell line NB4 carrying the PML-RAR alpha fusion was used as a target for cytotoxic T lymphocytes (CTL) stimulated to recognize the fusion. Stimulation of CTL was by production of dendritic cells pulsed with plasmid vectors containing polymerase chain reaction (PCR)-generated sequences of PML-RAR alpha derived from NB4 cells. PCR primer design included a Kozak consensus sequence to allow correct translation of the nucleic acid into protein. Identification of specific cytotoxicity was by both Granzyme B ELISPOT and by (51)Cr-release assays. RESULTS: Specific CTL activity targeting NB4 cells can be generated from donor-derived peripheral blood mononuclear cells. However, individual donors appear to respond differently to the length of stimulatory sequence encoded in the vector. Use of an internal methionine in the PML gene, which also satisfies the Kozak rules, allows translation in vitro and, thus, might provide a suitable start site for stimulation using acute promyelocytic leukaemia-specific sequence. CONCLUSION: The work presented here suggests that blood donor derived dendritic cells can be used to stimulate leukaemia-specific CTL from the same donation ex vivo. This would enable the generation of patient-specific therapeutics from major histocompatibility (MHC)-matched allogeneic donors. However, different MHC-matched donors might vary in their response depending on the length of the antigenic sequence.     

Extensive flow cytometric characterization of plasmacytoid dendritic cell leukemia cells

OBJECTIVES: Accumulating evidence suggests that non-T, non-B cell CD4+CD56+ neoplasms with lymphoblastic morphology include clinically and immunophenotypically diverse entities. Although their cells of origin or classification are still controversial several entities clearly represent a distinct type of neoplasms that are clinically aggressive. METHODS: In this work we present the immunophenotypic and genotypic features of bone marrow (BM), peripheral blood (PB), lymph node and skin lymphocytes from a patient diagnosed as plasmacytoid dendritic cell leukemia involving the skin, BM, PB, lymph nodes, liver and spleen. For determination of immunophenotypic characteristics of malignant plasmacytoid dendritic cells 73 monoclonal antibodies detecting lineage markers, chemokine receptors, cytokine receptors, activation, and co-stimulatory molecules were used. RESULTS AND CONCLUSION: The malignant cells proved to express CD4+, CD56+ lineage negative leukemia phenotype characteristically positive for CD36, CD38, CD40, CD45, CD45RA, CD68, CD123, CD184, HLA-DR, BDCA2, and granzyme-B corresponding to the preplasmacytoid dendritic cell developmental stage. The presence of CD11a/CD18, CD84, CD91, CD95, alphavbeta5, CDw197, and the absence of CD52 and CD133 in this case can be regarded as additional features of malignant cells. Completing the immunophenotypes with multidrug resistance function can provide additional information for characterizing pDC leukemia.     

Clinical outcomes of a novel therapeutic vaccine with Tax peptide‐pulsed dendritic cells for adult T cell leukaemia/lymphoma in a pilot study

Adult T cell leukaemia/lymphoma (ATL) is a human T cell leukaemia virus type‐I (HTLV‐I)‐infected T cell malignancy with poor prognosis. We herein developed a novel therapeutic vaccine designed to augment an HTLV‐I Tax‐specific cytotoxic T lymphocyte (CTL) response that has been implicated in anti‐ATL effects, and conducted a pilot study to investigate its safety and efficacy. Three previously treated ATL patients, classified as intermediate‐ to high‐risk, were subcutaneously administered with the vaccine, consisting of autologous dendritic cells (DCs) pulsed with Tax peptides corresponding to the CTL epitopes. In all patients, the performance status improved after vaccination without severe adverse events, and Tax‐specific CTL responses were observed with peaks at 16–20 weeks. Two patients achieved partial remission in the first 8 weeks, one of whom later achieved complete remission, maintaining their remission status without any additional chemotherapy 24 and 19 months after vaccination, respectively. The third patient, whose tumour cells lacked the ability to express Tax at biopsy, obtained stable disease in the first 8 weeks and later developed slowly progressive disease although additional therapy was not required for 14 months. The clinical outcomes of this pilot study indicate that the Tax peptide‐pulsed DC vaccine is a safe and promising immunotherapy for ATL.     

Dendritic cells pulsed with unfractionated helminthic proteins to generate antiparasitic cytotoxic T lymphocyte

Dendritic cells (DC) are sentinels of immunity. We determined their role in the induction of immunity against alveolar echinococcosis, caused by the larval stage of the cestode Echinococcus multilocularis. Furthermore, we evaluated if unfractionated protein from E. multilocularis (Em-Ag) can be used as loading agent for DC (comparable to unfractionated tumour proteins) in order to generate antiparasitic cytotoxic T lymphocyte (CTL). Interestingly, immature DC did not mature in the presence of 1 microg/ml Em-Ag as analysed by FACS and mixed leucocyte reactions. Yet, their capacity to take up dextran was markedly reduced. Further maturation of immature Em-Ag pulsed DC could be induced by proinflammatory cytokines. These mature DC were slightly better inducers of T cell proliferation when compared with unpulsed mature DC. Importantly, by repetetive stimulation of autologous CD8+ lymphocytes with the Em-Ag pulsed mature DC, we were able to generate specifically proliferating CTL lines. Thus, immunotherapy with ex vivo generated Em-Ag pulsed DC might be of benefit for patients inheriting this incurable disease.     

Induction of hepatitis C virus-specific cytotoxic T and B cell responses by dendritic cells expressing a modified antigen targeting receptor

AIM: To find a novel antigen (Ag) presentation strategy to improve the immune responses induced by dendritic cell (DC) vaccine expressing hepatitis C virus (HCV) core antigen (pcDNA3HCV C-Fc) in Balb/c mice (H-2d). METHODS: pcDNA3HCV C-Fc plasmid and eukaryotic expression vector pcDNA3 were injected into mice sc. Immune responses to pcDNA3HCV C-Fc were studied. Meanwhile the effect of pcDNA3HCV C-Fc on anti-translated subcutaneous tumor of SP2/0 cells stably expressing HCV C Ag (SP2/0-HCV C-FC) was also studied. Anti-HCV C in serum was detected by enzyme-linked immunoadsordent assay (ELISA) and HCV specific cytotoxic T lymphocyte (CTL) activity was measured by LDH release assay. After 3 wk of DNA immunization, the cells of SP2/0-HCV C-FC were inoculated into mice subcutaneously and tumor growth was measured every 5 d. The survival rate and living time of mice were also calculated. RESULTS: After 4 wk of DC immunization, the A450 nm values of sera in mice immunized with pcDNA3HCV C-Fc-DC and pcDNA3-DC were 0.56±0.17 and 0.12±0.03 respectively. The antibody titres in mice codeliveried with pcDNA3HCV C-Fc with DC were significantly higher than those of mice injected with pcDNA3-DC. The HCV specific CTL activities in mice coinjected with DC and pcDNA3HCV C-Fc or empty expression vectors were(73.2±3.1) % and (24.4±8.8) % , which were significantly higher than those of mice injected with water. The DC vaccine could evidently inhibit tumor growth, prolong the survival time of mice and improve the survival rate of mice and these effects could be improved by HCV C-Fc (pcDNA3HCV C-Fc) gene codelivered. CONCLUSION: DC vaccine has a strong antigenicity in humoral and cellular immunities, which can be promoted by transduced pcDNA3HCV C-Fc expressing HCV C or Fc. Thus, pcDNA3HCV C-Fc-transduced DCs may be a promising candidate for a CTL-based vaccine against HCV.     

In-vitro activation of cytotoxic T lymphocytes by fusion of mouse hepatocellular carcinoma cells and lymphotactin gene-modified dendritic cells

AIM： To investigate the in-vitro activation of cytotoxic T lymphocytes （CTLs） by fusion of mouse hepatocellular carcinoma （HCC） ceils and lymphotactin gene-modified dendritic cells （DCs）.
METHODS： Lymphotactin gene modified DCs （DCLptn） were prepared by lymphotactin recombinant adenovirus transduction of mature DCs which differentiated from mouse bone marrow cells by stimulation with granulocyte/macrophage colony-stimulating factor （GM- CSF）, interleukin-4 （IL-4） and tumor necrosis factor alpha （TNF-α）. DCLptn and H22 fusion was prepared using 50% PEG. Lymphotactin gene and protein expression levels were measured by RT-PCR and ELISA, respectively. Lymphotactin chemotactic responses were examined by in-vitro chemotaxis assay. In-vitro activation of CTl_s by DCLptn/H22 fusion was measured by detecting CD25 expression and cytokine production after autologous T cell stimulation. Cytotoxic function of activated T lymphocytes stimulated with DCLptn/H22 cells was determined by LDH cytotoxicity assay. RESULTS： Lymphotactin gene could be efficiently transduced to DCs by adenovirus vector and showed an effective biological activity. After fusion, the hybrid DCLptn/H22 cells acquired the phenotypes of both DCLptn and H22 cells. In T cell proliferation assay, flow cytometry showed a very high CD25 expression, and cytokine release assay showed a significantly higher concentration of IFN-α, and IL-2 in DCLptn/H22 group than in DCLptn, DCLptn＋H22, DC/H22 or H22 groups. Cytotoxicity assay revealed that T cells derived from DCLptn/H22 group had much higher anti-tumor activity than those derived from DCLptn, H22, DCLptn ＋ H22, DC/H22 groups. CONCLUSION： Lymphotactin gene-modified dendritoma induces T-cell proliferation and strong CTL reaction against allogenic HCC cells. Immunization-engineered fusion hybrid vaccine is an attractive strategy in prevention and treatment of HCC metastases.