Biomedical subjects

Gregory Lizée

Publications and source records attributed to Gregory Lizée.

9 recordsLinked to original sources

PubMed2006

Intralymphatic dendritic cell vaccination induces tumor antigen-specific, skin-homing T lymphocytes.

PURPOSE: The identification of tumor antigens recognized by cytotoxic and T helper lymphocytes has led to the development of specific cancer vaccines. Immunization with tumor antigen-pulsed dendritic cells has proved effective at eliciting elevated levels of tumor antigen-specific T cells in patient blood, but objective clinical responses remain rare, suggesting that vaccine-induced T cells are not trafficking optimally to site(s) of tumor burden. Accumulating evidence from animal models suggests that route of immunization can have a substantial influence on the subsequent migration of primed, activated T cells in vivo. EXPERIMENTAL DESIGN: In a clinical trial designed to elicit more effective cytotoxic T-cell mediated antitumor responses, metastatic melanoma patients were immunized directly via a peripheral intralymphatic route with autologous dendritic cells pulsed with HLA-A*0201-restricted melanoma-associated peptide antigens derived from MART-1 and gp100. RESULTS: Within 10 days of intralymphatic dendritic cell vaccination, four of six patients developed dramatic and diffuse erythematous rashes in sun-exposed areas of skin that showed extensive T-cell infiltration. CTLs grown from rash biopsies were strongly enriched for tumor antigen-specific T cells that had elevated expression of cutaneous lymphocyte antigen and chemokine receptor-6, consistent with a skin-homing phenotype. Of note, the only patient in the study with cutaneously localized disease showed a significant regression of metastatic lesions following the development of a surrounding rash. CONCLUSIONS: The evidence presented here is consistent with immunization studies in animal models and supports the concept that T cells are "imprinted" in peripheral lymph node sites to express specific ligands and chemokine receptors that allow them to migrate to skin. Furthermore, the preferential migration of the T cells to sun-exposed cutaneous sites suggests that inflammation plays a critical role in this migration. These observations suggest that further study of the effects of immunization route and inflammation on T-cell migration in humans is warranted, and could lead to vaccination approaches that would more reliably direct trafficking of activated T cells to diverse sites of metastatic disease.

Adult↗

PubMed2006

Improving antitumor immune responses by circumventing immunoregulatory cells and mechanisms.

Although numerous immunotherapeutic strategies have been studied in patients with cancer, consistent induction of clinical responses remains a formidable challenge. Cancer vaccines are often successful at generating elevated numbers of tumor-specific T lymphocytes in peripheral blood, however, despite this, tumors usually continue to grow unabated. Recent evidence suggests that endogenous regulatory cells, known to play a major role in the induction of immune tolerance to self and prevention of autoimmunity, as well as suppressive myeloid cells invoked in the tumor-bearing state, may be largely responsible for preventing effective antitumor immune responses. This review will focus on the major regulatory cell subtypes, including CD4(+)CD25(+) T-regulatory cells, type 1 regulatory T cells, natural killer T cells, and immature myeloid cells. Studies in humans and in animal models have shown a role for all of these cells in tumor progression, although the mechanisms by which they act to suppress immunity remain largely undefined. Elucidation of the dominant molecular mechanisms mediating immune suppression in vivo will allow more precise targeting of the relevant regulatory cell populations, as well as the development of novel strategies and clinical reagents that will directly block molecules that induce the suppression of antitumor immunity.

Animals↗

PubMed2006

Immunosuppression in melanoma immunotherapy: potential opportunities for intervention.

Although melanomas are substantially more immunogenic than other tumors, current immunotherapeutic approaches for melanoma patients have met with only limited success. Although melanoma-specific CD8+ T-cell responses can often be generated in patients naturally or through vaccination regimens, tumors frequently continue to grow unabated, suggesting that tumor-specific immune responses may be actively dampened in vivo. Research over the past decade has brought to light several mechanisms used by melanomas and other tumors to suppress tumor-specific immune responses. These include the presence of regulatory immune cells within the tumor microenvironment and draining lymph nodes that serve to shut down effector T-cell function. In addition, melanoma tumors themselves express a number of soluble and membrane-bound molecules that are responsible for inhibiting activated immune cells. The identification of these suppressive mechanisms has provided significant opportunities for designing novel therapeutic interventions that could augment current vaccination and adoptive transfer approaches for treatment of melanoma.

Animals↗

PubMed2005

Tails of wonder: endocytic-sorting motifs key for exogenous antigen presentation.

Antigen-presenting molecules, including MHC I, II and CD1, have central roles in the induction of T cell-mediated immunity against pathogens and tumors and also in the maintenance of tolerance towards self-antigens. The presentation of exogenously derived peptide and lipid antigens to specific T cells by professional antigen-presenting cells (pAPCs) is an essential part of both processes. Exogenous antigen loading takes place mostly within specialized endocytic and phagocytic compartments of pAPCs and targeting of antigen-presenting molecules to these intracellular compartments is mediated by highly conserved cytoplasmic sorting motifs. Recent data have revealed that the cytoplasmic tails of antigen-presenting molecules, by controlling the access of these molecules to exogenously derived antigens, have a crucially important and largely underappreciated role in the generation of tolerance and T-cell mediated immunity.

Amino Acid Motifs↗

PubMed2004

Dendritic cells strongly boost the antitumor activity of adoptively transferred T cells in vivo.

Dendritic cells (DCs) have been well characterized for their ability to initiate cell-mediated immune responses by stimulating naive T cells. However, the use of DCs to stimulate antigen-activated T cells in vivo has not been investigated. In this study, we determined whether DC vaccination could improve the efficacy of activated, adoptively transferred T cells to induce an enhanced antitumor immune response. Mice bearing B16 melanoma tumors expressing the gp100 tumor antigen were treated with cultured, activated T cells transgenic for a T-cell receptor specifically recognizing gp100, with or without concurrent peptide-pulsed DC vaccination. In this model, antigen-specific DC vaccination induced cytokine production, enhanced proliferation, and increased tumor infiltration of adoptively transferred T cells. Furthermore, the combination of DC vaccination and adoptive T-cell transfer led to a more robust antitumor response than the use of each treatment individually. Collectively, these findings illuminate a new potential application for DCs in the in vivo stimulation of adoptively transferred T cells and may be a useful approach for the immunotherapy of cancer.

Animals↗

PubMed2004

CD4(+) T-cell recognition of mutated B-RAF in melanoma patients harboring the V599E mutation.

The potential of antigen-directed cancer immunotherapy has not been fully realized, perhaps because many commonly targeted tumor associated proteins are not essential to maintaining the malignant cell phenotype. A constitutively activating mutation in the signaling molecule BRAF is expressed frequently in melanomas and may play an important role in the biology of this disease. A 29-mer B-Raf peptide incorporating the V599E mutation was used for in vitro stimulation of lymphocytes derived from melanoma patients, generating MHC class II-restricted CD4(+) T cells specific for this peptide as well as for melanoma cells expressing B-Raf V599E. Mutated B-Raf exemplifies targets that may be ideal for immunotherapy.

Alleles↗

PubMed2004

Lentivirus vector-mediated expression of tumor-associated epitopes by human antigen presenting cells.

Directing the human immune system to recognize and eliminate tumor cells is the ultimate goal of cancer immunotherapy. Vaccinating patients with autologous antigen presenting cells (APC) expressing tumor-associated antigens (TAA) represents a promising approach for activating tumor-reactive T cells in vivo. In addition, APC expressing TAA provide a means of generating tumor-specific T cells in vitro, for therapeutic and diagnostic applications. Lentiviral vectors are attractive vehicles for introducing TAA-encoding genes into APC. In this study, lentiviral vectors expressing the reporter gene GFP or the melanoma-associated antigen tyrosinase were used to transduce three different kinds of human APC: monocyte-derived dendritic cells (DC), CD40L-activated B lymphocytes, and Epstein Barr virus (EBV)-transformed B lymphocytes. Using optimized transduction conditions for each cell type, tyrosinase was expressed at levels sufficient to stimulate antigen-specific major histocompatibility complex (MHC) class I-restricted T cells from melanoma patients. While transduced EBV-B cells demonstrated the highest level of transgene expression, optimal T-cell recognition was achieved with transduced DC. Substituting the CAG promoter for PGK in lentiviral constructs enhanced transgene expression in DC and EBV-B cells, amplifying T cell recognition. Lentiviruses inducing sustained transgene expression with relatively low cellular toxicity and background viral gene expression may be ideal vectors for immunotherapeutic applications.

Antigen-Presenting Cells↗

PubMed2003

Control of dendritic cell cross-presentation by the major histocompatibility complex class I cytoplasmic domain.

Dendritic cells (DCs) can present extracellularly derived antigens in the context of major histocompatibility complex (MHC) class I molecules, a process called cross-presentation. Although recognized to be important for priming of T cell responses to many viral, bacterial and tumor antigens, the mechanistic details of this alternative antigen-presentation pathway are poorly understood. We demonstrate here the existence of an endolysosomal compartment in DCs where exogenously derived peptides can be acquired for presentation to T cells, and show that the MHC class I cytoplasmic domain contains a tyrosine-based targeting signal required for routing MHC class I molecules through these compartments. We also report that transgenic mice expressing H-2K(b) with a tyrosine mutation mount inferior H-2K(b)-restricted cytotoxic T lymphocyte responses against two immunodominant viral epitopes, providing evidence of a crucial function for cross-priming in antiviral immunity.

Animals↗

PubMed2003

Real-time quantitative reverse transcriptase-polymerase chain reaction as a method for determining lentiviral vector titers and measuring transgene expression.

The use of lentiviral vectors for basic research and potential future clinical applications requires methodologies that can accurately determine lentiviral titers and monitor viral transgene expression within target cells, beyond the context of reporter genes typically used for this purpose. Here we describe a quantitative RT-PCR (qRT-PCR) method that achieves both goals using primer sequences that are specific for the woodchuck hepatitis virus posttranscriptional regulatory element (WPRE), an enhancer contained in many retroviral vectors and that is incorporated in the 3' UTR of nascent transgene transcripts. Quantitation of titers of three recombinant lentiviruses, genetically identical except for the transgene, demonstrated consistent differences in titer that were likely due to transgene-associated toxicity in producer cells and target cells. Viruses encoding the tumor-associated antigens tyrosinase and neo-poly(A) polymerase yielded reproducibly lower titers than a virus encoding enhanced green fluorescent protein (GFP) at the viral RNA, integrated DNA, and transgene mRNA levels, as measured by WPRE qPCR. Furthermore, the magnitude of differences in expression of the three transgenes in transduced target cells could not have been predicted by measuring vector DNA integration events. Since transgene expression in target cells is the most common goal of lentiviral transduction, and since methods to quantify transgene expression on the protein level are not always readily available, qRT-PCR based on a nucleotide sequence included in the transcript provides a useful tool for titering novel recombinant lentiviruses.

3' Untranslated Regions↗