Induction of strong and persistent MelanA/MART-1-specific immune responses by adjuvant dendritic cell-based vaccination of stage II melanoma patients

A significant percentage of stage II melanoma patients (tumor thickness>1 mm) remain at risk of tumor recurrence after primary tumor excision. In this study, we used tumor antigen-pulsed dendritic cells as an adjuvant for immunization of these "high-risk" melanoma patients after resection of the primary tumor. A total of 13 patients were included and vaccinated 6 times every 14 days with autologous dendritic cells pulsed with a MelanA/MART-1 peptide in combination with a recall antigen. Antigen-specific immune responses were monitored before, during and up to 1 year after the last vaccination. The majority of patients exhibited increased recall antigen-specific CD4+ T cell responses upon vaccination. MelanA/MART-1-specific CD8+ T cells were expanded in 9/13 patients resulting in increased frequencies of memory cells in these patients. CD8+ T cells acquired the capacity to secrete IFN-gamma, to proliferate in culture in response to the tumor antigen used for vaccination and postvaccine samples contained MelanA/MART-1-specific T cells that recognized also the natural MelanA/MART-1-antigen expressed by tumor cells. Moreover, vaccination induced a long-lived tumor antigen-specific DTH-reactivity in the majority of the patients, detectable even 12 months after the last immunization. These data demonstrate for the first time that vaccination with tumor antigen-pulsed dendritic cells in a clinically adjuvant setting induces strong and persistent antigen-specific T-cell responses in tumor-free stage II melanoma patients, suggesting that tumor protective T cell immunity can be achieved.     

Mild hyperthermia enhances human monocyte-derived dendritic cell functions and offers potential for applications in vaccination strategies

Dendritic cell (DC)-based immunotherapy has been shown to be a promising strategy for anti-cancer therapy. Nevertheless, only a low overall clinical response rate has been observed in vaccinated patients with advanced cancer and therefore methods to improve DC immuno-stimulatory functions are currently under intense investigation. In this respect, we exposed human monocyte-derived DCs to a physiological temperature stress of 40°C for up to 24 h followed by analysis for (i) expression of different heat shock proteins, (ii) survival, (iii) cell surface maturation markers, (iv) cytokine secretion, and (v) migratory capacity. Furthermore, we examined the ability of heat-shocked DCs to prime naïve CD8⁺ T cells after loading with MelanA peptide, by transfection with MelanA RNA, or by transduction with MelanA by an adenovirus vector. The results clearly indicate that in comparison to control DCs, which remained at 37°C, heat-treated cells revealed no differences concerning the survival rate or their migratory capacity. However, DCs exposed to thermal stress showed a time-dependent enhanced expression of the immune-chaperone heat shock protein 70A and both an up-regulation of co-stimulatory molecules such as CD80, CD83, and CD86 and of the inflammatory cytokine TNF-α. Moreover, these cells had a markedly improved capacity to prime autologous naïve CD8⁺ T cells in vitro in an antigen-specific manner, independent of the method of antigen-loading. Thus, our strategy of heat treatment of DCs offers a promising means to improve DC functions during immune activation which, as a physical method, facilitates straight-forward applications in clinical DC vaccination protocols.     

A comparison of two types of dendritic cell as adjuvants for the induction of melanoma-specific T-cell responses in humans following intranodal injection.

Dendritic cells (DCs) elicit potent anti-tumoral T-cell responses in vitro and in vivo. However, different types of DC have yet to be compared for their capacity to induce anti-tumor responses in vivo at different developmental stages. Herein, we correlated the efficiencies of different types of monocyte-derived DC as vaccines on the resulting anti-tumor immune responses in vivo. Immature and mature DCs were separately pulsed with a peptide derived from tyrosinase, MelanA/MART-1 or MAGE-1 and a recall antigen. Both DC populations were injected every 2 weeks in different lymph nodes of the same patient. Immune responses were monitored before, during and after vaccination. Mature DCs induced increased recall antigen-specific CD4(+) T-cell responses in 7/8 patients, while immature DCs did so in only 3/8. Expansion of peptide-specific IFN-gamma-producing CD8(+) T cells was observed in 5/7 patients vaccinated with mature DCs but in only 1/7 using immature DCs. However, these functional data did not correlate with the tetramer staining. Herein, immature DCs also showed expansion of peptide-specific T cells. In 2/4 patients vaccinated with mature DCs, we observed induction of peptide-specific cytotoxic T cells, as monitored by chromium-release assays, whereas immature DCs failed to induce peptide-specific cytotoxic T cells in the same patients. Instead, FCS-cultured immature DCs induced FCS-specific IgE responses in 1 patient. Our data demonstrate that this novel vaccination protocol is an efficient approach to compare different immunization strategies within the same patient. Thus, our data define FCS-free cultured mature DCs as superior inducers of T-cell responses in melanoma patients.     

Autologous tumor cell vaccination combined with adoptive cellular immunotherapy in patients with Grade III/IV astrocytoma

Summary Brain tumors are highly resistant to treatment. Their diffuse infiltrative nature and the relative inaccessibility of the brain to blood and lymph are barriers to surgical and cytotoxic treatments alike. Preclinical animal studies demonstrated that intravenously administered tumor antigen-specific T lymphocytes will reject tumors growing in the brain. Specifically activated effector T lymphocytes may be generated by in vivo immunization followed by restimulation of antigen-primed T cells with autologous tumor cells in vitro. In order to apply these findings to humans, feasibility studies of combined active immunization and specific adoptive cellular immunotherapy were performed on fifteen patients with recurrent astrocytoma. The objective was to determine whether; 1) T cells could be grown from peripheral blood of patients immunized with autologous tumor cells, and 2) whether stimulated cells could be safely readministered to patients. Patients were immunized with a combination of their own irradiated tumor cells and Bacillus of Calmette and Guerin. Two weeks later, a mononuclear cell-rich fraction of blood was obtained by leukapheresis. Mononuclear cells were cultured with irradiated autologous tumor cells and interleukin-2. Selective expansion of CD4⁺ and CD8⁺ T lymphocytes occurred. Intravenous transfer of stimulated cells to the fifteen patients on twenty-four separate occasions with or without systemic administration of interleukin-2 was tolerated with limited toxicity. The studies established the feasibility of conducting controlled studies of the anti-tumor effects of tumor antigen-specific cellular immunotherapy.     

A pilot study on the immunogenicity of dendritic cell vaccination during adjuvant oxaliplatin/capecitabine chemotherapy in colon cancer patients

Background:

Dendritic cell (DC) vaccination has been shown to induce anti-tumour immune responses in cancer patients, but so far its clinical efficacy is limited. Recent evidence supports an immunogenic effect of cytotoxic chemotherapy. Pre-clinical data indicate that the combination of chemotherapy and immunotherapy may result in an enhanced anti-cancer activity. Most studies have focused on the immunogenic aspect of chemotherapy-induced cell death, but only few studies have investigated the effect of chemotherapeutic agents on the effector lymphocytes of the immune system.

Methods:

Here we investigated the effect of treatment with oxaliplatin and capecitabine on non-specific and specific DC vaccine-induced adaptive immune responses. Stage III colon cancer patients receiving standard adjuvant oxaliplatin/capecitabine chemotherapy were vaccinated at the same time with keyhole limpet haemocyanin (KLH) and carcinoembryonic antigen (CEA)-peptide pulsed DCs.

Results:

In 4 out of 7 patients, functional CEA-specific T-cell responses were found at delayed type hypersensitivity (DTH) skin testing. In addition, we observed an enhanced non-specific T-cell reactivity upon oxaliplatin administration. KLH-specific T-cell responses remained unaffected by the chemotherapy, whereas B-cell responses were diminished.

Conclusion:

The results strongly support further testing of the combined use of specific anti-tumour vaccination with oxaliplatin-based chemotherapy.     

Surgery and adjuvant dendritic cell-based tumour vaccination for patients with relapsed malignant glioma, a feasibility study

Patients with relapsed malignant glioma have a poor prognosis. We developed a strategy of vaccination using autologous mature dendritic cells loaded with autologous tumour homogenate. In total, 12 patients with a median age of 36 years (range: 11-78) were treated. All had relapsing malignant glioma. After surgery, vaccines were given at weeks 1 and 3, and later every 4 weeks. A median of 5 (range: 2-7) vaccines was given. There were no serious adverse events except in one patient with gross residual tumour prior to vaccination, who repetitively developed vaccine-related peritumoral oedema. Minor toxicities were recorded in four out of 12 patients. In six patients with postoperative residual tumour, vaccination induced one stable disease during 8 weeks, and one partial response. Two of six patients with complete resection are in CCR for 3 years. Tumour vaccination for patients with relapsed malignant glioma is feasible and likely beneficial for patients with minimal residual tumour burden.     

Intra-tumoral dendritic cells increase efficacy of peripheral vaccination by modulation of glioma microenvironment

Pilot data showed that adding intratumoral (IT) injection of dendritic cells (DCs) prolongs survival of patients affected by glioblastoma multiforme (GBM) treated by subcutaneous (SC) delivery of DCs. Using a murine model resembling GBM, we investigated the immunological mechanisms underlying this effect. C57BL6/N mice received brain injections of GL261 glioma cells. Seven days later, mice were treated by 3 SC injections of DCs with or without 1 IT injection of DCs. DC maturation, induced by pulsing with GL261 lysates, was necessary to develop effective immune responses. IT injection of pulsed (pDC), but not unpulsed DCs (uDC), increased significantly the survival, either per se or in combination with SC-pDC (P < .001 vs controls). Mice treated by IT-pDC plus SC-pDC survived longer than mice treated by SC-pDC only (P = .03). Injected pDC were detectable in tumor parenchyma, but not in cervical lymph nodes. In gliomas injected with IT-pDC, CD8+ cells were significantly more abundant and Foxp3+ cells were significantly less abundant than in other groups. Using real-time polymerase chain reaction, we also found enhanced expression of IFN-γ and TNF-α and decreased expression of transforming growth factor-beta (TGF-β) and Foxp3 in mice treated with SC-pDC and IT-pDC. In vitro, pDC produced more TNF-α than uDC: addition of TNF-α to the medium decreased the proliferation of glioma cells. Overall, the results suggest that IT-pDC potentiates the anti-tumor immune response elicited by SC-pDC by pro-immune modulation of cytokines in the tumor microenvironment, decrease of Treg cells, and direct inhibition of tumor proliferation by TNF-α.     

Therapeutic potential of dendritic cell vaccines in sarcoma of the extremities

Sarcomas of the extremities are challenging to treat. They are divided into soft-tissue and bone sarcomas in general, which also have many subtypes, based on their different mesenchymal origins and anatomical locations, respectively. Each of these sarcomas present in different ways, exhibit different behaviors and prognoses, and present unique therapeutic challenges. Dendritic cells (DCs) are the best professional antigen-presenting cells that can induce both the generation and proliferation of specific cytotoxic T lymphocytes and helper T lymphocytes through antigen presentation by MHC class I and class II molecules, respectively. In this review, a series of recently conducted immunotherapy for extremital sarcomas based on DCs are summarized and the potential for therapeutic DC vaccination targeted against these tumors is assessed.     

Tumor-reactive CD8+ T-cell clones in patients after NY-ESO-1 peptide vaccination

A major objective of peptide vaccination is the induction of tumor-reactive CD8+ T-cells. We have shown that HLA-A2 positive cancer patients frequently develop an antigen-specific CD8+ T-cell response after vaccination with NY-ESO-1 peptides p157-165/p157-167. These T-cells are highly reactive with the peptides used for vaccination, but only rarely recognize HLA-matched, NY-ESO-1 expressing tumor cell lines. To address the apparent lack of tumor recognition of vaccine-induced CD8+ T-cell responses, we used autologous tumor cells for in vitro stimulation and expansion of pre- and postvaccine CD8+ T-cells. In contrast to standard presensitization methods with peptide-pulsed antigen-presenting cells, mixed lymphocyte tumor culture favored the selective expansion of low-frequency tumor-reactive T-cells. In four patients, we were able to demonstrate that antigen-specific and tumor-reactive T-cells are detectable and are indeed elicited as a result of NY-ESO-1 peptide vaccination. Further analyses of postvaccine antigen-specific T-cells at a clonal level show that vaccine-induced antigen-specific T-cells are heterogeneous in functional activity. These results suggest that the methods of immunomonitoring are critical to identify the proportion of tumor-reactive T-cells within the population of vaccine-induced antigen-specific effector cells. Our results show that immunization with NY-ESO-1 peptides leads to strong tumor-reactive CD8+ T-cell responses. Our findings suggest that approaches to peptide vaccination may be improved to induce higher numbers of antigen-specific T-cells and to selectively increase the proportion of CD8+ T-cells that have the capacity to recognize and eliminate tumor cells.     

Dendritic cell biology and the application of dendritic cells to immunotherapy of multiple myeloma

Dendritic cells (DCs) are extremely efficient antigen-presenting cells that are potent stimulators of both B and T cell immune responses. Although DCs are normally present in extremely small numbers in the circulation, recent advances in DC biology have made it possible to generate DCs in culture. DCs can be generatedin vitro from various cellular sources including bone marrow, cord blood and peripheral blood. Although culture conditions are extremely diverse, the majority of protocols grow DCs in GM-CSF and either TNF-alpha and/or IL-4. The addition of other growth factors such as SCF and Flt-3 ligand can dramatically enhance DC recovery. It is important to appreciate that DC subsets have been identified. Thus, DC at different stages of maturation, based on phenotype and capacity to capture antigen, can be obtained depending on culture conditions. For clinical applications, DCs can be generated in serum-free media and cryopreserved for future clinical applications. The ability to obtain DCs in numbers suitable for manipulating immune responses has pushed DC-based immunotherapies into the spotlight for treatment of various malignancies, including multiple myeloma, a B cell malignancy that is presently incurable. Although high-dose chemotherapy and transplantation have improved complete remission rates and overall survival in myeloma, immunotherapeutic strategies are needed for the additional cytoreduction needed to achieve a cure. Because DCs specialize in antigen capture and are extremely potent at stimulating T cell responses, they are ideally suited for generating anti-myeloma T cell responsesin vivo. Several studies have demonstrated that myeloma protein, also called idiotype (Id), is sufficiently immunogenic and can be used to generatein vivo T cell responses in myeloma patients. Clinical trials using Id-pulsed DCs as a vaccine to treat minimal residual disease or relapsed myeloma are currently underway. Feasibility studies indicate that antigen-pulsed autologous DCs can be used to elicitin vivo Id-specific T cell responses. Additional studies are needed to optimize current DC vaccination protocols and determine clinical benefits associated with this approach. It is hoped that, following conventional therapies, a combination of adoptive immunotherapeutic modalities such as DCs together with myeloma-specific T cells may lead to improved clinical responses in multiple myeloma, and ultimately lead to complete remission and cure.     

膀胱肿瘤抗原致敏的树突状细胞诱导 T 淋巴细胞抗肿瘤效应的研究

目的：研究经膀胱肿瘤抗原致敏后的树突状细胞（Dc）对T淋巴细胞的激活、增殖作用及对T24膀胱肿瘤细胞的抑癌效应。方法：分离健康供血者外周血单个核细胞及T淋巴细胞，联合应用粒／巨噬细胞集落刺激因子（GM—CSF）及白介素-4（IL-4）从单个核细胞中培养出Dc，以人膀胱癌细胞系T24肿瘤细胞裂解物刺激Dc，检测经膀胱肿瘤抗原致敏后的DC对T淋巴细胞的细胞增殖动力学影响并用M1rr显色法测定致敏Dc诱导的T淋巴细胞对T24膀胱肿瘤细胞体外的抗肿瘤效应。结果：膀胱癌细胞裂解物致敏的Dc可诱导T淋巴细胞强烈的增殖反应，与对照组比较具有显著性差异（P〈0．01）；增殖后的T淋巴细胞对T24膀胱肿瘤细胞有明显的细胞毒作用。结论：经膀胱肿瘤抗原致敏的Dc能诱导产生显著的T淋巴细胞增殖，在体外有明显的抑癌效应。     

Induction of antigen-specific CD4- and CD8-mediated T-cell responses by fusions of autologous dendritic cells and metastatic colorectal cancer cells

Human metastatic colorectal carcinomas (CRCAs) express carcinoembryonic antigen (CEA) and/or MUC1 tumor-associated antigens as potential targets for the induction of active specific immunity. In the present study, freshly isolated metastatic CRCA cells were successfully fused with immature autologous human monocyte-derived dendritic cells (DCs). The created heterokaryons (DC/CRCA) coexpress the CRCA-derived CEA and MUC1 antigens and DC-derived MHC class II and costimulatory molecules. The fusion cells were functional in stimulating the proliferation of autologous T cells. In addition, both CD4(+) and CD8(+) T cells were activated by fusion cells, as demonstrated by the production of high levels of IFN-gamma. More importantly, coculture of fusion cells with patient-derived peripheral blood mononuclear cells (PBMCs) resulted in the induction of antigen-specific cytotoxic T lymphocytes (CTLs). CTLs were effective at lysis of not only autologous CRCA cells but also the CEA and/or MUC1-positive and HLA partially matched target cells. Antigen-specific CTL responses were confirmed by tetrameric analysis. Coculture of PBMCs with fusion cells resulted in increased frequency of CEA- and MUC1-specific CTLs simultaneously. Taken together, these results indicate that freshly isolated human metastatic CRCA cells expressing the CEA and/or MUC1 may represent a potential partner for the creation of DC/tumor fusion cells targeting induction of antigen-specific CTL responses. Our report demonstrates the simultaneous induction of CRCA-specific CTL responses restricted by HLA-A2 and -A24.     

膀胱肿瘤抗原致敏的树突状细胞诱导T淋巴细胞抗肿瘤效应的研究

目的：研究经膀胱肿瘤抗原致敏后的树突状细胞（Dc）对T淋巴细胞的激活、增殖作用及对T24膀胱肿瘤细胞的抑癌效应。方法：分离健康供血者外周血单个核细胞及T淋巴细胞，联合应用粒／巨噬细胞集落刺激因子（GM—CSF）及白介素-4（IL-4）从单个核细胞中培养出Dc，以人膀胱癌细胞系T24肿瘤细胞裂解物刺激Dc，检测经膀胱肿瘤抗原致敏后的DC对T淋巴细胞的细胞增殖动力学影响并用M1rr显色法测定致敏Dc诱导的T淋巴细胞对T24膀胱肿瘤细胞体外的抗肿瘤效应。结果：膀胱癌细胞裂解物致敏的Dc可诱导T淋巴细胞强烈的增殖反应，与对照组比较具有显著性差异（P〈0．01）；增殖后的T淋巴细胞对T24膀胱肿瘤细胞有明显的细胞毒作用。结论：经膀胱肿瘤抗原致敏的Dc能诱导产生显著的T淋巴细胞增殖，在体外有明显的抑癌效应。     

肿瘤源性血管内皮细胞RNA转染树突细胞体外诱导特异性CTL的研究

目的:探讨转染肿瘤血管内皮细胞RNA的树突细胞(DC)能否诱导特异性的细胞毒性T淋巴细胞(CTL)。方法:采用肿瘤细胞的培养上清诱导人脐静脉内皮细胞(HUVEC)增殖,从而制备肿瘤源性血管内皮细胞(Td-EC)。用RT-PCR检测肿瘤内皮标志1(TEM1)在Td-EC上的表达。制备Td-EC的总RNA,转染从人外周血中扩增的未成熟DC,用流式细胞仪检测DC表型的变化,用LDH法检测DC诱导的CTL对Td-EC、HUVEC和人脐静脉内皮细胞株CRL-1730的杀伤率。结果:Td-EC特异性表达TEM1。转染RNA的DC组CD83、CD86表达率分别为(85.22±7.73)%和(88.38±8.02)%,而未成熟DC组CD83、CD86表达率分别为(51.58±9.49)%和(61.77±2.91)%,两组差异有统计学意义,P<0.05。在效靶比为20∶1、10∶1和5∶1时,CTL对Td-EC的杀伤率分别为(34.15±1.14)%、(27.02±1.31)%和(13.12±1.63)%;CTL对HUVEC杀伤率分别为(11.35±0.97)%、(8.24±0.37)%和(5.30±0.73)%;CTL对CRL-1730杀伤率分别为(13.24±1.76)%、(8.41±0.91)%和(5.31±0.94)%;CTL对Td-EC杀伤率均显著高于对HUVEC和CRL-1730的杀伤率,P<0.05。结论:转染Td-EC RNA的DC可在体外诱导CTL特异性地杀伤Td-EC。     

Numerical defect of circulating dendritic cell subsets and defective dendritic cell generation from monocytes of patients with advanced melanoma

The behaviour of circulating dendritic cells (DCs) and DC generation from monocytes in melanoma patients during the progression of disease have not been described.     

自体热休克凋亡细胞负载树突状细胞治疗大肠癌的疗效观察

目的：探讨自体热休克凋亡细胞负载的树突状细胞（dendritic cells,DC）治疗大肠癌的临床疗效。方法：采用酶消化法从手术切除的14例大肠癌新鲜组织获得单细胞悬液,热休克处理后用桦脂酸诱导其凋亡制备成细胞抗原;采集外周静脉血,分离单个核细胞,经GM-CSF与IL-4体外诱导成未成熟树突状细胞,负载细胞抗原后制备成DC肿瘤疫苗;对14例大肠癌患者进行4个疗程的DC免疫治疗,观察患者不良反应、敏感程度、生存质量、生存时间、癌胚抗原等临床指标。结果：DC治疗大肠癌未出现明显不良反应,5例患者的DTH检测阳性;14例患者的平均CEA水平由治疗前的99.5ng/ml降至治疗后的71.4ng/ml（P〈0.05）;治疗后血清中IL-2、IL-12及IFN-γ浓度均显著高于治疗前,具有统计学差异（P〈0.05）;所有患者均生存1年,其中1例患者出现了短暂的后腹膜淋巴结缩小,持续3个月,第2年由于肿瘤的进展生存率下降,由80%降至20%;患者的KPS评分上升,与治疗前比较有所改善（P〈0.05）。结论：自体热休克凋亡细胞负载的DC治疗大肠癌在临床治疗中具较高安全性,可改善患者免疫功能,临床观察显示患者近期临床效果明显;为大肠癌的临床综合治疗提供了一种新方法。     

自体热休克凋亡细胞负载树突状细胞治疗大肠癌的疗效观察

目的:探讨自体热休克凋亡细胞负载的树突状细胞(dendritic cells,DC)治疗大肠癌的临床疗效。方法:采用酶消化法从手术切除的14例大肠癌新鲜组织获得单细胞悬液,热休克处理后用桦脂酸诱导其凋亡制备成细胞抗原;采集外周静脉血,分离单个核细胞,经GM-CSF与IL-4体外诱导成未成熟树突状细胞,负载细胞抗原后制备成DC肿瘤疫苗;对14例大肠癌患者进行4个疗程的DC免疫治疗,观察患者不良反应、敏感程度、生存质量、生存时间、癌胚抗原等临床指标。结果:DC治疗大肠癌未出现明显不良反应,5例患者的DTH检测阳性;14例患者的平均CEA水平由治疗前的99.5ng/ml降至治疗后的71.4ng/ml(P<0.05);治疗后血清中IL-2、IL-12及IFN-γ浓度均显著高于治疗前,具有统计学差异(P<0.05);所有患者均生存1年,其中1例患者出现了短暂的后腹膜淋巴结缩小,持续3个月,第2年由于肿瘤的进展生存率下降,由80%降至20%;患者的KPS评分上升,与治疗前比较有所改善(P<0.05)。结论:自体热休克凋亡细胞负载的DC治疗大肠癌在临床治疗中具较高安全性,可改善患者免疫功能,临床观察显示患者近期临床效果明显;为大肠癌的临床综合治疗提供了一种新方法。     

Bcap37完全细胞抗原冲击树突状细胞诱导特异性抗乳腺癌免疫实验研究

目的　研究 Bcap37完全细胞抗原冲击树突状细胞 (DC)能否诱导特异性抗肿瘤免疫 ,探索乳腺癌的免疫治疗方法。方法　从人外周血分离单核细胞 ,用 GM- CSF和 IL - 4诱导出 DC,反复冻融制备 Bcap37完全细胞抗原 ,将此抗原冲击的 DC与 T细胞共培养 ,以 7天后分离的 T细胞为效应细胞 ,与肿瘤细胞混合培养 ,MTT法测定对肿瘤细胞的抑制作用。结果　单核细胞经细胞因子诱导 8天 ,形态、表型及功能鉴定为成熟 DC;完全细胞抗原冲击 DC诱导的 T细胞对肿瘤细胞具有明显的抑制作用。结论　 Bcap37完全细胞抗原冲击 DC可有效诱导特异性抗肿瘤免疫     

NKT and CD8 lymphocytes mediate suppression of hepatocellular carcinoma growth via tumor antigen-pulsed dendritic cells

Dendritic cells (DCs) are antigen presenting cells that play a role in T-cell activation. Liver-associated natural killer T lymphocytes (NKTs) are a unique subset of lymphocytes that may be important in antitumor immunity. Hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) expresses hepatitis B virus surface antigen (HBsAg) on its cell surface and may serve as a tumor-associated antigen. The aim of the study was to evaluate the antitumor effect of DC pulsed with tumor or viral-associated antigens in HBV-expressing HCC in mice and to determine the role of NKT lymphocytes in this process. Balb/c mice were sublethally irradiated and transplanted with Hep3b HCC cell line, followed by transplantation of naive splenocytes. DCs were separated using CD11c beads and pulsed with HBV-enveloped proteins (group A), HCC cell lysate (group B), or BSA (control group C). Mice were followed for survival and tumor size. To determine the mechanism of the antitumor effect, intrasplenic and intrahepatic lymphocyte subpopulations were analyzed by FACS for NKT, CD4 and CD8 markers. Tumor-associated antigens-specific IFNgamma ELISPOT, T-cell proliferation assays and serum cytokine analysis were performed. Treatment with tumor-associated antigen-pulsed DC significantly improved survival (40% and 50% as compared with 0% in groups A, B, and control group C, respectively; p < 0.005). Tumor size decreased to 12.8 +/- 0.4 and 0 from 60.4 +/- 0.9 mm(3) in groups A, B, and control group C, respectively (p < 0.005). Adoptive transfer of HBV or Hep3b-associated antigens-pulsed DC induced a 6-fold increase in peripheral CD8(+) lymphocytes (from 1% in control mice to 6% and 5.5% in groups A and B, respectively), along with a decrease in CD4(+) lymphocytes (from 3.5% in controls to 1.4% and 2.3% in A and B, respectively; p < 0.005). The CD8(+)/CD4(+) ratio increased from 0.28 in controls to 4.28 and 2.39 in groups A and B, respectively (p < 0.005). Intrasplenic NKT cells increased from 7% in control mice to 7.98% and 14.6% in groups A and B, respectively. In contrast, an opposite shift was observed inside the liver. Intrahepatic lymphocyte analysis showed a marked increase in CD4(+) and a decrease in CD8(+) lymphocytes in treated groups. The intrahepatic CD4(+) number increased from 0.5% in controls to 2.15% and 25.8% in groups A and B, respectively (p < 0.005). In contrast, a significant decrease in the intrahepatic CD8(+) numbers was observed (from 7% in controls to 1.0% and 2.4% in groups A and B, respectively; p < 0.005). A significant increase was noted in HBV-specific IFNgamma spot-forming T-cell colonies from 0.0 to 8.8 +/- 1.7 and 1.8 +/- 2.9 in groups C, A, and B, respectively (p < 0.005). Similarly, a significant increase in the HBV-specific T-cell stimulation index, from 0.8 +/- 0.2 to 7.2 +/- 0.4, in groups C and B, respectively, was noted (p < 0.002). IFNgamma and IL12 serum levels increased significantly in treated groups. IFNgamma and IL12 serum levels increased to 380 +/- 30 and 400 +/- 20, and 960 +/- 40 and 760 +/- 60 in groups A and B, compared with 150 +/- 16 and 490 +/- 40 pg/ml in control mice (p < 0.005). Tumor antigen-pulsed DCs effectively suppressed the growth of hepatocellular carcinoma in mice. This effect was associated with enhanced NKT and CD8(+) lymphocyte function and augmentation of the antitumor/antiviral-specific IFNgamma production.