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Biomedical subjects

James S Economou

Publications and source records attributed to James S Economou.

At least 19 recordsLinked to original sources
PubMed2006

NK and CD4 cells collaborate to protect against melanoma tumor formation in the brain.

NK cells represent a potent immune effector cell type that have the ability to recognize and lyse tumors. However, the existence and function of NK cells in the traditionally "immune-privileged" CNS is controversial. Furthermore, the cellular interactions involved in NK cell anti-CNS tumor immunity are even less well understood. We administered non-Ag-loaded, immature dendritic cells (DC) to CD8alpha knockout (KO) mice and studied their anti-CNS tumor immune responses. DC administration induced dramatic antitumor immune protection in CD8alpha KO mice that were challenged with B16 melanoma both s.c. and in the brain. The CNS antitumor immunity was dependent on both CD4+ T cells and NK cells. Administration of non-Ag-loaded, immature DC resulted in significant CD4+ T cell and NK cell expansion in the draining lymph nodes at 6 days postvaccination, which persisted for 2 wk. Finally, DC administration in CD8alpha KO mice was associated with robust infiltration of CD4+ T cells and NK cells into the brain tumor parenchyma. These results represent the first demonstration of a potent innate antitumor immune response against CNS tumors in the absence of toxicity. Thus, non-Ag-loaded, immature DC administration, in the setting of CD8 genetically deficient mice, can induce dramatic antitumor immune responses within the CNS that surpass the effects observed in wild-type mice. Our results suggest that a better understanding of the cross-talk between DC and innate immune cells may provide improved methods to vaccinate patients with tumors located both systemically and within the CNS.

Animals↗
PubMed2006

A phase I/II trial testing immunization of hepatocellular carcinoma patients with dendritic cells pulsed with four alpha-fetoprotein peptides.

Alpha-fetoprotein (AFP) is a self protein expressed by fetal liver at high levels, but is transcriptionally repressed at birth. AFP is up-regulated in hepatocellular carcinomas, and patients with active disease could have plasma levels as high as 1 mg/mL. We previously identified four immunodominant HLA-A*0201-restricted peptides [hAFP(137-145) (PLFQVPEPV), hAFP(158-166) (FMNKFIYEI), hAFP(325-334) (GLSPNLNRFL), and hAFP(542-550) (GVALQTMKQ)] derived from human AFP that could stimulate specific T cell responses in healthy donor peripheral blood lymphocytes in vitro. We conducted a phase I/II clinical trial in which HLA-A*0201 patients with AFP-positive hepatocellular carcinoma were immunized with three biweekly intradermal vaccinations of the four AFP peptides pulsed onto autologous dendritic cells (DC). DCs were prepared from adherent peripheral blood mononuclear cells cultured with granulocyte-macrophage colony-stimulating factor and interleukin-4 for 7 days. Sixteen subjects were enrolled and 10 were treated. Peripheral blood lymphocytes were isolated from these patients before, during, and after AFP peptide/DC immunization and were tested ex vivo with MHC tetramer and IFNgamma ELISPOT analysis. Six of 10 subjects expanded statistically significant levels of AFP-specific T cells postvaccine to at least one peptide by MHC tetramer. Also, 6 of 10 subjects increased IFNgamma producing AFP-specific T cell responses to at least one of the peptides postvaccination, by ELISPOT. We conclude that the human T cell repertoire is capable of responding to the AFP self antigen after the administration of AFP peptide-pulsed DC even in an environment of high circulating levels of this oncofetal antigen.

Adult↗
PubMed2006

Immunosensitization of tumor cells to dendritic cell-activated immune responses with the proteasome inhibitor bortezomib (PS-341, Velcade).

Proteasome inhibition results in proapoptotic changes in cancer cells, which may make them more sensitive to immune effector cells. We established a murine model to test whether the proteasome inhibitor bortezomib could sensitize established B16 melanoma tumors to dendritic cell (DC)-activated immune effector cells. Day 3-established s.c. B16 tumors had significantly decreased tumor outgrowth when treated with a combination of bortezomib and DC, regardless of whether the DC were loaded or not with a tumor Ag. In vivo Ab-depletion studies demonstrated that the effector cells were NK and CD8+ cells, but not CD4+ cells. NF-kappaB nuclear transcription factor assay and gene-expression profiling of B16 treated with bortezomib was consistent with inhibition of NF-kappaB target genes leading to a proapoptotic phenotype. In vitro lytic assays demonstrated that TNF-alpha, but not perforin, Fas-ligand, or TRAIL, was responsible for bortezomib-sensitized B16 cytotoxicity. In conclusion, the proteasome inhibitor bortezomib can pharmacologically sensitize tumor cells to the lytic effects of DC-activated immune effector cells.

Animals↗
PubMed2006

Definition of an immunologic response using the major histocompatibility complex tetramer and enzyme-linked immunospot assays.

PURPOSE: Define an immunologic response using the tetramer and enzyme-linked immunospot (ELISPOT) assays. EXPERIMENTAL DESIGN: Ten healthy subjects and 21 patients with melanoma (all HLA-A*0201) donated a total of 121 blood samples to determine the lower limit of detection (LLD), analytic coefficient of variation (aCV), and physiologic CV (pCV) of the tetramer and ELISPOT assays. The mean, SD, and reference change value (RCV) were calculated to define changes beyond the assay imprecision, and its application was tested in the monitoring of T-cell expansion after CTLA4 blockade with ticilimumab (CP-675,206). RESULTS: The LLD for the tetramer assay was 0.038% CD8+ cells and seven spots per 10(5) peripheral blood mononuclear cells for the ELISPOT assay. The aCV of the tetramer assay was <10% and was higher for the ELISPOT (24.69-36.32%). There was marked between-subject variability on baseline homeostatic values, which was correlated to prior antigen exposure. An immunologic response was defined as an increase beyond the mean + 3 SD in antigen-specific cells for subjects with baseline levels below the LLD, or beyond the assay RCV for baseline levels above the LLD. In four patients receiving ticilimumab, expansions of antigen-specific T cells beyond the assay variability were noted for EBV and MART1 antigens. CONCLUSIONS: A combined approach of change from negative (below the LLD) to positive (above the LLD) and a percentage change beyond the assay variability using the RCV score can be computed to define which change in circulating antigen-specific T cells represents a response to immunotherapy.

Adult↗
PubMed2005

Broad antitumor protection by dendritic cells administered to CD8alpha knock out mice.

Dendritic cell (DC) administration to CD8alpha knock-out (CD8alphaKO) mice results in a strong antigen-non-specific protection to a B16 murine melanoma tumor challenge. This response is mediated by lytic NK cells and cytokine-producing CD4 cells. We aimed to determine the signals that guide tumor targeting of this response. CD8alphaKO mice in the C57BL/6 background received subcutaneous (s.c.) injections of immature DC. Mice were challenged in vivo or assayed for lytic activity in vitro to a panel of syngeneic tumors with different levels of MHC class I expression. These studies support the following conclusions: (1) DC administration to CD8alphaKO mice results in protective in vivo responses to syngeneic tumors from epithelial, neuroectodermal and hematopoietic origin; in vivo protection is independent of the level of MHC classes I and II expression. (2) The in vitro lytic activity of DC-activated NK cells from CD8alphaKO mice has sensitive and insensitive targets, which is independent of the cell lineage or the level of inhibitory self-MHC surface molecules. (3) In sensitive targets a putative activating NK ligand in DC-stimulated NK cells from CD8alphaKO mice signals directly to PI3-K, but is distinct from NKG2D.

Animals↗
PubMed2005

Natural killer cells play a critical role in the immune response following immunization with melanoma-antigen-engineered dendritic cells.

Tumor antigen gene-modified dendritic cells (DC) generates robust antigen-specific protective antitumor responses. Though the role of CD4 positive and CD8 positive cells in the immunological response to gene-modified DC has been well-characterized, the role of NK cells in this response has been somewhat less clear. Owing to the significant contribution of innate immunity in other model systems, we postulated that NK cells would hold a critical position in the generation of an immune response following immunization with tumor antigen-engineered DC. Immunization with MART-1 melanoma antigen-engineered DC in C57BL/6 mice resulted in the generation of antigen-specific cytotoxic T lymphocytes and in vivo protective responses to the murine B16 melanoma. These responses were dependent on the presence of functional NK cells, although NK cells alone were not sufficient in generating protective responses. Adoptive transfer of NK cells into an NK-deficient but T-cell-competent environment restored the protective response to gene-modified DC immunization. In conclusion, protective immunity after tumor antigen gene-modified DC immunization requires collaboration between CD4+ and CD8+ T cells and NK cells.

Adoptive Transfer↗
PubMed2004

Ionizing radiation affects human MART-1 melanoma antigen processing and presentation by dendritic cells.

Radiation is generally considered to be an immunosuppressive agent that acts by killing radiosensitive lymphocytes. In this study, we demonstrate the noncytotoxic effects of ionizing radiation on MHC class I Ag presentation by bone marrow-derived dendritic cells (DCs) that have divergent consequences depending upon whether peptides are endogenously processed and loaded onto MHC class I molecules or are added exogenously. The endogenous pathway was examined using C57BL/6 murine DCs transduced with adenovirus to express the human melanoma/melanocyte Ag recognized by T cells (AdVMART1). Prior irradiation abrogated the ability of AdVMART1-transduced DCs to induce MART-1-specific T cell responses following their injection into mice. The ability of these same DCs to generate protective immunity against B16 melanoma, which expresses murine MART-1, was also abrogated by radiation. Failure of AdVMART1-transduced DCs to generate antitumor immunity following irradiation was not due to cytotoxicity or to radiation-induced block in DC maturation or loss in expression of MHC class I or costimulatory molecules. Expression of some of these molecules was affected, but because irradiation actually enhanced the ability of DCs to generate lymphocyte responses to the peptide MART-1(27-35) that is immunodominant in the context of HLA-A2.1, they were unlikely to be critical. The increase in lymphocyte reactivity generated by irradiated DCs pulsed with MART-1(27-35) also protected mice against growth of B16-A2/K(b) tumors in HLA-A2.1/K(b) transgenic mice. Taken together, these results suggest that radiation modulates MHC class I-mediated antitumor immunity by functionally affecting DC Ag presentation pathways.

Animals↗
PubMed2004

Enhanced tumor responses to dendritic cells in the absence of CD8-positive cells.

Wild-type mice immunized with MART-1 melanoma Ag-engineered dendritic cells (DC) generate strong Ag-specific immunity that has an absolute requirement for both CD8(+) and CD4(+) T cells. DC administration to CD8 alpha knockout mice displayed unexpectedly enhanced levels of protection to tumor challenge despite this deficiency in CD8(+) T cells and the inability to mount MHC class I-restricted immune responses. This model has the following features: 1) antitumor protection is Ag independent; 2) had an absolute requirement for CD4(+) and NK1.1(+) cells; 3) CD4(+) splenocytes are responsible for cytokine production; 4) lytic cells in microcytotoxicity assays express NK, but lack T cell markers (NK1.1(+) alpha beta TCR(-) CD3(-)); and 5) the lytic phenotype can be transferred to naive CD8 alpha knockout mice by NK1.1(+) splenocytes. Elucidation of the signaling events that activate these effective cytotoxic cells and the putative suppressive mechanisms in a wild-type environment may provide means to enhance the clinical activity of DC-based approaches.

Adenoviruses, Human↗
PubMed2004

Surveillance of the eye and vision in a clinical trial of MART1-transformed dendritic cells for metastatic melanoma.

PURPOSE: To report the protocol for surveillance of the eye and vision in a clinical trial of MART1-transduced dendritic cells for metastatic melanoma. METHODS: In a phase I/II clinical trial of dendritic cell-based genetic immunotherapy for metastatic cutaneous melanoma, ophthalmic evaluation is performed prior to immunization (Baseline Evaluation), 56+/-7 days after first vaccination (mid-study evaluation), when dendritic cell injections are complete 112+/-7 days after first vaccination (end-study evaluation) and 168+/-7 days after first vaccination (post-study evaluation). RESULTS: The protocol for baseline, mid-study and end-study evaluations of the eye and vision includes ophthalmic history, comprehensive ophthalmic examination, psychophysical and electrophysiological visual function assessment, fundus photography and fluorescein angiography. Post-study evaluation consists of the 25-item visual functioning questionnaire augmented to elicit autoimmune manifestation with complete ophthalmic evaluation if vision-related symptoms or abnormalities are noted during or after the vaccination. CONCLUSION: Limited adverse effects on the eye and vision have been reported in melanoma immunotherapy trials, although this novel mode of therapy has the potential to induce melanoma paraneoplastic syndromes known to severely impair vision. Therefore, surveillance of the eye and vision should be considered in melanoma immunotherapy trials.

Antigens, Neoplasm↗
PubMed2004

Antigen presentation by MART-1 adenovirus-transduced interleukin-10-polarized human monocyte-derived dendritic cells.

Dendritic cells (DC) play critical roles in generating an immune response and in inducing tolerance. Diverse microenvironmental factors can 'polarize' DC toward an immunogenic or non-immunogenic phenotype. Among the various microenvironmental factors, interleukin-10 (IL-10) exhibits a potent immunosuppressive effect on antigen-presenting cells (APC). Here, we show that monocyte-derived DC generated in the presence of IL-10 exhibit a profound down-regulation of many genes that are associated with immune activation and show that the IL-10-grown DC are poor stimulators of CD8(+) T cells in a strictly autologous and major histocompatibility complex (MHC) class I-restricted melanoma antigen recognized by T cells (MART-1) epitope presentation system. However, these IL-10-grown DC can efficiently activate the epitope-specific CD8(+) T cells when they are made to present the epitope following transduction with an adenoviral vector expressing the MART-1 antigen. In addition, we show that the MART-1 protein colocalizes with the MHC class I protein, equally well, in the iDC and in the DC cultured in presence of IL-10 when both DC types are infected with the viral vector. We also show that the vector transduced DC present the MART-1(27-35) epitope for a sustained period compared to the peptide pulsed DC. These data suggest that although DCs generated in the presence of IL-10 tend to be non-immunogenic, they are capable of processing and presenting an antigen when the antigen is synthesized within the DC.

Adenoviridae↗
PubMed2003

T-cell responses to HLA-A*0201 immunodominant peptides derived from alpha-fetoprotein in patients with hepatocellular cancer.

PURPOSE: An existing immunological paradigm is that high concentrations of soluble protein contribute to the maintenance of peripheral tolerance/ignorance to self protein. We tested this hypothesis in a clinical immunotherapy trial using class I-restricted peptide epitopes derived from alpha-fetoprotein (AFP). AFP is a self protein expressed by fetal liver at high levels, but transcriptionally repressed at birth. AFP is de-repressed in a majority of hepatocellular carcinomas (HCCs) and patients with active disease can have plasma levels in the mg/ml range. We previously identified four immunodominant HLA-A*0201-restricted peptides derived from human AFP that could stimulate specific T-cell responses in normal volunteer peripheral blood lymphocytes cultures. We wished to test the hypothesis that AFP peptide-reactive T cells could be expanded in vivo in HCC patients immunized with these four AFP peptides. EXPERIMENTAL DESIGN: We undertook a pilot Phase I clinical trial in which HLA-A*0201 patients with AFP-positive HCC were immunized with three biweekly intradermal vaccinations of the four AFP peptides (100 microg or 500 microg each) emulsified in incomplete Freund's adjuvant. RESULTS: All of the patients (n=6) generated T-cell responses to most or all of the peptides as measured by direct IFNgamma enzyme-linked immunospot (ELISPOT) and MHC class I tetramer assays. CONCLUSIONS: We conclude that the human T-cell repertoire is capable of recognizing AFP in the context of MHC class I even in an environment of high circulating levels of this oncofetal protein.

Adult↗
PubMed2003

Regulation of melanoma epitope-specific cytolytic T lymphocyte response by immature and activated dendritic cells, in vitro.

Dendritic cell (DC)-based immunization in cancer has proven to be a promising approach. However, just as DCs are crucial accessory cells in generating immune responses, they also seem to participate in tolerance induction, especially against peripheral "self" antigens. The bulk of the evidence that DCs present peripheral self antigens to induce tolerance has, however, come mostly from studies in transgenic animal models. A tolerogenic function of DCs for peripheral self antigens in a human model has not been critically examined. In this study using the Melan-A/MART-1(27-35) peptide as a model for self but melanoma-associated antigen-against which human hosts often harbor CD8(+) CTL precursors with high frequencies-we confirm that although immature dendritic cells (iDCs) are inefficient antigen presenting cells (APCs), fully activated DCs efficiently activate melanoma epitope-specific CD8(+) CTL precursors, in vitro. We, however, show that in a direct epitope presentation schema, iDCs neither delete nor anergize epitope-specific CD8(+) T cells in primary or secondary stimulation. Interestingly, iDCs and activated DCs can delete a large fraction of the epitope-specific CTLs on tertiary stimulation. The deletion is induced in an epitope-specific manner and through apoptosis. These observations, therefore, have implications on the DC-based cancer vaccine designs and are relevant in the inquiry into the role of DCs on tolerance induction.

Autoantigens↗
PubMed2003

Current developments in cancer vaccines and cellular immunotherapy.

This article reviews the immunologic basis of clinical trials that test means of tumor antigen recognition and immune activation, with the goal to provide the clinician with a mechanistic understanding of ongoing cancer vaccine and cellular immunotherapy clinical trials. Multiple novel immunotherapy strategies have reached the stage of testing in clinical trials that were accelerated by recent advances in the characterization of tumor antigens and by a more precise knowledge of the regulation of cell-mediated immune responses. The key steps in the generation of an immune response to cancer cells include loading of tumor antigens onto antigen-presenting cells in vitro or in vivo, presenting antigen in the appropriate immune stimulatory environment, activating cytotoxic lymphocytes, and blocking autoregulatory control mechanisms. This knowledge has opened the door to antigen-specific immunization for cancer using tumor-derived proteins or RNA, or synthetically generated peptide epitopes, RNA, or DNA. The critical step of antigen presentation has been facilitated by the coadministration of powerful immunologic adjuvants, the provision of costimulatory molecules and immune stimulatory cytokines, and the ability to culture dendritic cells. Advances in the understanding of the nature of tumor antigens and their optimal presentation, and in the regulatory mechanisms that govern the immune system, have provided multiple novel immunotherapy intervention strategies that are being tested in clinical trials.

Animals↗
PubMed2003

Determinant spreading and tumor responses after peptide-based cancer immunotherapy.

Modern immunological assays are very sensitive for detection of antigen-specific T cells. These assays are used to detect increased levels of T cells after peptide-based immunotherapy for cancer in an attempt to describe surrogate endpoints correlated with anti-tumor activity. Recent reports demonstrate that determinant spreading develops in a high frequency of subjects with tumor regression responses after this type of immunotherapy and could be valuable for trial monitoring and the design of more effective vaccines.

Cancer Vaccines↗
PubMed2003

Determinant spreading associated with clinical response in dendritic cell-based immunotherapy for malignant melanoma.

PURPOSE: The purpose of this study was to determine the toxicity and immunological effects of three different doses and two routes of administration of autologous dendritic cells (DCs) pulsed with the MART-1(27-35) immunodominant epitope. EXPERIMENTAL DESIGN: Eighteen HLA-A*0201-positive subjects with stage III-IV melanoma received three biweekly i.v. or intradermal injections of ex vivo generated myeloid DCs pulsed with MART-1(27-35) epitope. Repeated blood samples were processed to obtain peripheral blood mononuclear cells for immunological analysis using IFN-gamma ELISPOT, MHC class I tetramer, intracellular cytokine staining, and microcytotoxicity assays. RESULTS: The frequency of MART-1/Melan-A (MART-1) antigen-specific T cells in peripheral blood increased in all dose levels as assessed by ELISPOT and MHC class I tetramer assays, but without a clear dose-response effect. The intradermal route generated stronger MART-1 immunity compared with the i.v. route. MART-1-specific immunity did not correlate with clinical outcome in any of the four immunological assays used. However, analysis of determinant spreading to other melanoma antigens was noted in the only subject with complete response to this single-epitope immunization. CONCLUSIONS: Intradermal immunization with MART-1 peptide-pulsed DCs results in an increase in circulating IFN-gamma-producing, antigen-specific T cells. The frequency of these cells did not correlate with response. In contrast, spreading of immune reactivity to other melanoma antigens was only evident in a subject with a complete response, suggesting that determinant spreading may be an important factor of clinical response to this form of immunotherapy.

Adult↗
PubMed2002

Immunosuppressive effects of interleukin-12 coexpression in melanoma antigen gene-modified dendritic cell vaccines.

Genetic immunotherapy with tumor antigen gene-modified dendritic cells (DC) generates robust immunity, although antitumor protection is not complete in all models. Previous experience in a model in which C57BL/6 mice immunized with DC transduced with adenoviral vectors expressing MART-1 demonstrated a 20-40% complete protection to a tumor challenge with B16 melanoma cells. Tumors that did develop in immunized mice had slower growth kinetics compared to tumors implanted in naïve mice. In the present study, we wished to determine if the supraphysiological production of the Th1-skewing cytokine interleukin-12 (IL-12) could enhance immune activation and antitumor protection in this model. In a series of experiments immunizing mice with DC cotransduced with MART-1 and IL-12, antitumor protection and antigen-specific splenocyte cytotoxicity and interferon gamma production inversely correlated with the amount of IL-12 produced by DC. This adverse effect of IL-12 could not be explained by a direct cytotoxic effect of natural killer cells directed towards DC, nor the production of nitric oxide leading to down-regulation of the immune response - the two mechanisms previously recognized to explain immune-suppressive effects of IL-12-based vaccine therapy. In conclusion, in this animal model, IL-12 production by gene-modified DC leads to a cytokine-induced dose-dependent inhibition of antigen-specific antitumor protection.

Animals↗
PubMed2002

Cancer immunotherapy using gene-modified dendritic cells.

Gene-engineered dendritic cells (DC) are being tested in cancer immunotherapy. DC are the best equipped antigen-presenting cells (APC) to overcome tolerance/ignorance to self antigens presented by cancer cells. Genetic immunotherapy with DC engineered to express tumor antigens has the potential advantages of endogenous epitope presentation by both major histocompatibility complex (MHC) class I and II molecules. DC can also be gene-modified to express immunostimulatory molecules that further enhance their antigen-presenting function. Review of the literature provided 52 manuscripts where gene-modified DC were being tested in murine models of immunotherapy for cancer. Review of the antitumor effects of gene-modified DC in these preclinical studies provides valuable information on the optimal methods of gene transfer into DC, the schedule of administration, the route, dose and the underlying immunological mechanisms of the antitumor effects. These data may help in the translation of this promising approach to the clinic.

Adenoviridae↗