Retrovirally Transduced Human Dendritic Cells Express a Normal Phenotype and Potent T-Cell Stimulatory Capacity

Anti-tumor immunity induced by in vivo adenovirus vector-mediated expression of CD40 ligand in tumor cells

CD40 ligand (CD40L), the ligand for CD40 on antigen-presenting cells, is essential for the initiation of antigen-specific T cell responses, an important component of the immune response to tumors. This study is based on the hypothesis that in vivo genetic modification of tumor cells to express CD40L will trigger CD40 on local antigen-presenting cells to present tumor antigen to the cellular immune systems, thus eliciting anti-tumor immunity to suppress growth of the tumor. To examine this concept, subcutaneous tumors of three different murine tumor models in two strains of mice were infected with a recombinant adenovirus (Ad) vector expressing murine CD40L (AdmCD40L). In the B16 (H-2b, melanoma) and CT26 (H-2d, colon cancer) murine models, injection of AdmCD40L into established subcutaneous tumors resulted in sustained tumor regression and tumor-free status in >60% of animals. Intratumoral injection of AdmCD40L also significantly suppressed the growth of established, weakly immunogenic Lewis lung carcinoma (H-2b) tumors, but to a lesser extent. Ex vivo AdmCD40L-transduced tumor cells implanted in syngeneic hosts induced significant antitumor response against preexisting identical tumors at a distant site. Both in vivo and in vitro AdmCD40L modification of tumors to express CD40L elicited tumor-specific cytolytic T lymphocytes responses, and the transfer of spleen cells from treated mice efficiently protected naive mice against a subsequent tumor challenge. These results support the concept that transduction of tumors with a recombinant CD40L adenovirus vector may be a useful strategy for cancer immunotherapy.

Enhanced therapeutic efficacy of tumor RNA-pulsed dendritic cells after genetic modification with lymphotactin

Pulsing dendritic cells (DCs) with tumor cell-derived mRNA is regarded as an attractive alternative in the development of DC-based tumor vaccines. Our aim is to improve the therapeutic efficacy of DC-based tumor RNA vaccines by augmenting the preferential chemotaxis of DCs to T cells. Mouse bone marrow-derived DCs were genetically modified with lymphotactin (Lptn) by adenovirus vector, which conferred on DCs preferential chemotaxis to CD4+ and CD8+ T cells (Cao et al., 1998). Lptn gene-modified DCs (Lptn-DCs) were pulsed with tumor mRNA and used for vaccination in the tumor models of 3LL lung carcinoma and B16 melanoma. In both tumor models, immunization with 4 X 10(4) tumor RNA-pulsed Lptn-DCs induced more potent CTL activity, compared with their counterparts, specifically against tumor cells and Mut1 or tyrosinase-related protein 2 (TRP-2) peptide-pulsed RMA-S cells, and rendered the immunized mice resistant to tumor challenge much more effectively. CD8+ T cells were necessary and sufficient to generate the protection of Lptn-DC-based RNA tumor vaccines, and CD4+ T cells were required for the induction of tumor rejection. In the preestablished 3LL and B16 tumor models, vaccination with DC-based or LacZ-DC-based tumor RNA vaccines (2 X 10(5) cells) could reduce pulmonary metastasis and extend survival of tumor-bearing mice, but was less effective than the Lptn-DC counterpart (with 60-80% mice surviving). When the immunizing dose was decreased to 4 X 10(4) cells, Lptn-DC-based tumor vaccines rather than their counterparts were still significantly effective. Our studies provide a potential strategy to improve the efficacy of DC-based vaccines, and a new approach to immunological intervention by chemokines.

Bone Marrow and Peripheral Blood Dendritic Cells From Patients With Multiple Myeloma Are Phenotypically and Functionally Normal Despite the Detection of Kaposi’s Sarcoma Herpesvirus Gene Sequences

Multiple myeloma (MM) cells express idiotypic proteins and other tumor-associated antigens which make them ideal targets for novel immunotherapeutic approaches. However, recent reports show the presence of Kaposi’s sarcoma herpesvirus (KSHV) gene sequences in bone marrow dendritic cells (BMDCs) in MM, raising concerns regarding their antigen-presenting cell (APC) function. In the present study, we sought to identify the ideal source of DCs from MM patients for use in vaccination approaches. We compared the relative frequency, phenotype, and function of BMDCs or peripheral blood dendritic cells (PBDCs) from MM patients versus normal donors. DCs were derived by culture of mononuclear cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4. The yield as well as the pattern and intensity of Ag (HLA-DR, CD40, CD54, CD80, and CD86) expression were equivalent on DCs from BM or PB of MM patients versus normal donors. Comparison of PBDCs versus BMDCs showed higher surface expression of HLA-DR (P = .01), CD86 (P = .0003), and CD14 (P = .04) on PBDCs. APC function, assessed using an allogeneic mixed lymphocyte reaction (MLR), demonstrated equivalent T-cell proliferation triggered by MM versus normal DCs. Moreover, no differences in APC function were noted in BMDCs compared with PBDCs. Polymerase chain reaction (PCR) analysis of genomic DNA from both MM patient and normal donor DCs for the 233-bp KSHV gene sequence (KS330233) was negative, but nested PCR to yield a final product of 186 bp internal to KS330233 was positive in 16 of 18 (88.8%) MM BMDCs, 3 of 8 (37.5%) normal BMDCs, 1 of 5 (20%) MM PBDCs, and 2 of 6 (33.3%) normal donor PBDCs. Sequencing of 4 MM patient PCR products showed 96% to 98% homology to the published KSHV gene sequence, with patient specific mutations ruling out PCR artifacts or contamination. In addition, KHSV-specific viral cyclin D (open reading frame [ORF] 72) was amplified in 2 of 5 MM BMDCs, with sequencing of the ORF 72 amplicon revealing 91% and 92% homology to the KSHV viral cyclin D sequence. These sequences again demonstrated patient specific mutations, ruling out contamination. Therefore, our studies show that PB appears to be the preferred source of DCs for use in vaccination strategies due to the ready accessibility and phenotypic profile of PBDCs, as well as the comparable APC function and lower detection rate of KSHV gene sequences compared with BMDCs. Whether active KSHV infection is present and important in the pathophysiology of MM remains unclear; however, our study shows that MMDCs remain functional despite the detection of KSHV gene sequences.

Bone Marrow and Peripheral Blood Dendritic Cells From Patients With Multiple Myeloma Are Phenotypically and Functionally Normal Despite the Detection of Kaposi’s Sarcoma Herpesvirus Gene Sequences

Multiple myeloma (MM) cells express idiotypic proteins and other tumor-associated antigens which make them ideal targets for novel immunotherapeutic approaches. However, recent reports show the presence of Kaposi’s sarcoma herpesvirus (KSHV) gene sequences in bone marrow dendritic cells (BMDCs) in MM, raising concerns regarding their antigen-presenting cell (APC) function. In the present study, we sought to identify the ideal source of DCs from MM patients for use in vaccination approaches. We compared the relative frequency, phenotype, and function of BMDCs or peripheral blood dendritic cells (PBDCs) from MM patients versus normal donors. DCs were derived by culture of mononuclear cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4. The yield as well as the pattern and intensity of Ag (HLA-DR, CD40, CD54, CD80, and CD86) expression were equivalent on DCs from BM or PB of MM patients versus normal donors. Comparison of PBDCs versus BMDCs showed higher surface expression of HLA-DR (P = .01), CD86 (P = .0003), and CD14 (P = .04) on PBDCs. APC function, assessed using an allogeneic mixed lymphocyte reaction (MLR), demonstrated equivalent T-cell proliferation triggered by MM versus normal DCs. Moreover, no differences in APC function were noted in BMDCs compared with PBDCs. Polymerase chain reaction (PCR) analysis of genomic DNA from both MM patient and normal donor DCs for the 233-bp KSHV gene sequence (KS330233) was negative, but nested PCR to yield a final product of 186 bp internal to KS330233 was positive in 16 of 18 (88.8%) MM BMDCs, 3 of 8 (37.5%) normal BMDCs, 1 of 5 (20%) MM PBDCs, and 2 of 6 (33.3%) normal donor PBDCs. Sequencing of 4 MM patient PCR products showed 96% to 98% homology to the published KSHV gene sequence, with patient specific mutations ruling out PCR artifacts or contamination. In addition, KHSV-specific viral cyclin D (open reading frame [ORF] 72) was amplified in 2 of 5 MM BMDCs, with sequencing of the ORF 72 amplicon revealing 91% and 92% homology to the KSHV viral cyclin D sequence. These sequences again demonstrated patient specific mutations, ruling out contamination. Therefore, our studies show that PB appears to be the preferred source of DCs for use in vaccination strategies due to the ready accessibility and phenotypic profile of PBDCs, as well as the comparable APC function and lower detection rate of KSHV gene sequences compared with BMDCs. Whether active KSHV infection is present and important in the pathophysiology of MM remains unclear; however, our study shows that MMDCs remain functional despite the detection of KSHV gene sequences.

High level of retrovirus-mediated gene transfer into dendritic cells derived from cord blood and mobilized peripheral blood CD34+ cells

Dendritic cells (DCs), the most potent antigen-presenting cells, can be generated from CD34+ hematopoietic stem cells and used for generating therapeutic immune responses. To develop immunotherapy protocols based on genetically modified DCs, we have investigated the conditions for high-level transduction of a large amount of CD34+-derived DCs. Thus, we have used an efficient and clinically applicable protocol for the retroviral transduction of cord blood (CB) or mobilized peripheral blood (MPB) CD34+ cells based on infection with gibbon ape leukemia virus (GALV)-pseudotyped retroviral vectors carrying the nls-LacZ reporter gene. Infected cells have been subsequently cultured under conditions allowing their dendritic differentiation. The results show that using a growth factor combination including granulocyte-macrophage colony-stimulating factor plus tumor necrosis factor alpha plus interleukin 4 plus stem cell factor plus Flt3 ligand, more than 70% of DCs derived from CB or MPB CD34+ cells can be transduced. Semiquantitative PCR indicates that at least two proviral copies per cell were detected. Transduced DCs retain normal immunophenotype and potent T cell stimulatory capacity. Finally, by using a semisolid methylcellulose assay for dendritic progenitors (CFU-DCs), we show that more than 90% of CFU-DCs can be transduced. Such a highly efficient retrovirus-mediated gene transfer into CD34+-derived DCs makes it possible to envision the use of this methodology in clinical trials.

Lymphotactin Gene-Modified Bone Marrow Dendritic Cells Act as More Potent Adjuvants for Peptide Delivery to Induce Specific Antitumor Immunity

Dendritic cells (DC) are regarded as attractive candidates for cancer immunotherapy. Our aim is to improve the therapeutic efficacy of DC-based tumor vaccine by augmenting DC preferential chemotaxis on T cells. Mouse bone marrow-derived DC were transduced with lymphotactin (Lptn) gene by adenovirus vector. The supernatants from Lptn gene-modified DC (Lptn-DC) were capable of attracting CD4+ and CD8+ T cells in a chemotaxis assay, whereas their mock control could not. Lptn expression of Lptn-DC was further confirmed by RT-PCR. Lptn-DC were pulsed with Mut1 peptide and used for vaccination. Immunization with the low dose (1 × 104) of Mut1 peptide-pulsed DC induced weak CTL activity, whereas the same amounts of Mut1 peptide-pulsed Lptn-DC markedly induced specific CTL against 3LL tumor cells. A single immunization with 1 × 104 Mut1 peptide-pulsed Lptn-DC could render mice resistant to a 5 × 105 3LL tumor cell challenge completely, but their counterpart could not. The protective immunity induced by Mut1 peptide-pulsed Lptn-DC depends on both CD4+ T cells and CD8+ T cells rather than NK cells in the induction phase and depends on CD8+ T cells rather than CD4+ T cells and NK cells in the effector phase. Moreover, the involvement of CD28/CTLA4 costimulation pathway and IFN-γ are also necessary. When 3LL tumor-bearing mice were treated with 1 × 104 Mut1 peptide-pulsed Lptn-DC, their pulmonary metastases were significantly reduced, whereas the same low dose of Mut1 peptide-pulsed DC had no obvious therapeutic effects. Our data suggest that Lptn-DC are more potent adjuvants for peptide delivery to induce protective and therapeutic antitumor immunity.

Human Dendritic Cell (DC)-Based Anti-Infective Therapy: Engineering DCs to Secrete Functional IFN-γ and IL-12

An imbalance in the Th1- and Th2-type cytokine responses may allow certain microbes to modify the host response to favor their own persistence. We now show that infection/pulsing of human CD34+ peripheral blood hemopoietic progenitor cell-derived dendritic cells (DCs) with Leishmania donovani promastigotes, Histoplasma capsulatum, and Mycobacterium kansasii impairs the constitutive production of IL-12 from these cells. Thus, strategies aimed at modulating a dysregulated Th1/Th2 response to infection would be of great interest. To both augment the host immune response and deliver potent immunomodulatory cytokines such as IL-12 and IFN-γ, our goal is to develop a therapeutic strategy using genetically modified, microbial Ag-pulsed DCs. Toward developing such immunotherapies, we used retrovirus-mediated somatic gene transfer techniques to engineer human DCs to secrete biologically active IL-12 and IFN-γ. DCs pulsed with microbial antigens (e.g., leishmania and histoplasma Ags) were capable of inducing proliferative responses in autologous CD4+ lymphocytes. CD4+ lymphocytes cocultured with IL-12-transduced autologous DCs had enhanced Ag-specific proliferative responses compared with CD4+ lymphocytes cocultured with nontransduced or IFN-γ- transduced DCs. In this cell culture model system we demonstrate that IL-12 has a negative effect on IL-4 secretion that is independent of its ability to induce IFN-γ secretion. Taken together, these results indicate that IL-12-transduced DCs may be specifically suited in inducing or down-modulating Ag-specific Th1 or Th2 responses, respectively, and thus may be useful as adjunctive therapy in those intracellular infections in which a dominant Th1 response is critical for the resolution of infection.

Experimental vaccine strategies for cancer immunotherapy

Recently, cancer immunotherapy has emerged as a therapeutic option for the management of cancer patients. This is based on the fact that our immune system, once activated, is capable of developing specific immunity against neoplastic but not normal cells. Increasing evidence suggests that cell-mediated immunity, particularly T-cell-mediated immunity, is important for the control of tumor cells. Several experimental vaccine strategies have been developed to enhance cell-mediated immunity against tumors. Some of these tumor vaccines have generated promising results in murine tumor systems. In addition, several phase I/II clinical trials using these vaccine strategies have shown extremely encouraging results in patients. In this review, we will discuss many of these promising cancer vaccine strategies. We will pay particular attention to the strategies employing dendritic cells, the central player for tumor vaccine development.