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Timothy M Clay

Publications and source records attributed to Timothy M Clay.

31 records · Page 2Linked to original sources
PubMed2003

Proteomics for monitoring immune responses to cancer vaccines.

Standardized biomarkers for the detection of clinically significant immunological responses would be extremely valuable in immunotherapy trials. Most available assays measure either the frequency or function of antigen-specific T-cells, or the titers of antibodies or immune complexes. These assays have generally exhibited either inadequate sensitivity or too high a signal-to-noise ratio to reliably detect the low-frequency T-cell responses induced by cancer vaccines. In addition, such assays reflect only one aspect of the immune response rather than the complete picture. Proteomics, the study of proteins within a cell or biological sample, may offer a novel approach to immunological monitoring that complements existing immunological assays. By studying the protein content of T-cells responding to a vaccine or in the serum of vaccinated individuals, it may be possible to develop a metric for quantitating the magnitude of immunological responses. Proteomics could also provide a tool for establishing the quality of the immune response and for obtaining valuable information regarding the underlying regulatory mechanisms and pathways. Advances in miniaturization and automation may also permit characterization of the immune response more rapidly and from smaller amounts of biological material than is possible with existing assay systems.

Animals↗
PubMed2002

Dendritic cell recovery following nonmyeloablative allogeneic stem cell transplants.

Nonmyeloablative allogeneic stem cell transplantation (NMSCT) may destroy some malignancies through a graft-versus-tumor (GVT) effect, but tumor relapse and viral reactivation remain challenges for which immunizations may be helpful. Dendritic cells (DC), particularly DC1 and ex vivo-cultured DC, induce antigen-specific immune responses following viral infections and anti-tumor immunizations. DC2 may be tolerogenic. We hypothesize that successful immunizations following NMSCT will require adequate numbers of functional DC1 or ex vivo-generated DC. We determined the number, phenotype, and function of blood DC1 and DC2 and ex vivo-generated DC obtained from donor-recipient pairs before and up to 90 days after NMSCT. Although the percentage and number of recipient blood Lin(-) HLA-DR(+) CD11c(+) DC1 following NMSCT (median 0.46%, IQR 0.33-0.52%) was lower than donor DC1 (median 0.94%, IQR 0.40-2.2%) this was not significant. In contrast, the percentage and absolute number of blood Lin(-) HLA-DR(+) CD11c(-) CD123(+) DC2 was significantly decreased following the transplant (median 0.01% IQR 0.01-0.01% at day 60 compared with median 0.14%, IQR 0.10-0.38% for the donor before transplantation, p < 0.05). The yield (median 6.0%, IQR 5.5-8.5%) and allostimulatory function of ex vivo-generated DC did not differ significantly at any time point. The donor chimerism of blood and cultured DC reflected that of the overall white blood cells. Ex vivo-generated, donor DC loaded with cytomegalovirus (CMV) antigens were capable of stimulating a CMV-specific immune response in vitro within peripheral blood mononuclear cells of a patient following NMSCT. We conclude that blood DC numbers may be diminished following NMSCT transplant, but that DC1 recovery exceeds DC2 and functional DC may be generated from peripheral blood progenitors at all time points suggesting a possible use in immunization strategies.

Alemtuzumab↗
PubMed2002

The feasibility and safety of immunotherapy with dendritic cells loaded with CEA mRNA following neoadjuvant chemoradiotherapy and resection of pancreatic cancer.

BACKGROUND: Resected pancreatic cancer has a high risk of recurrence and mortality despite the the use of chemoradiotherapy. Because pancreatic cancers express tumor antigens such as carcinoembryonic antigen (CEA), it may be possible to immunize patients to induce tumor antigen-specific immune responses. We hypothesize that high-frequency tumor antigen-specific immune responses will reduce recurrence and increase survival. Autologous dendritic cells (DCs) loaded with tumor antigens are particularly potent at inducing tumor antigen-specific immune responses. METHODS: Three patients with resected pancreatic adenocarcinoma following neoadjuvant chemoradiotherapy received autologous, monocyte-derived DCs loaded with the mRNA encoding CEA monthly for 6 mo. RESULTS: It was feasible to generate an adequate number of DC from these patients and to cryopreserve them for repeated use. The DC demonstrated the typical immature phenotype. The immunizations were well-tolerated without evidence of adverse events. All three developed injection site reactivity. All three are alive without evidence of disease at more than 2 1/2 yr from the original diagnosis. CONCLUSION: The postoperative period following neoadjuvant chemoradiotherapy and pancreaticoduodenectomy for pancreatic cancer is an ideal environment to test novel immune-based therapies. DC-based immunotherapy in this setting is safe and feasible and may lead to prolonged survival.

Adenocarcinoma↗
PubMed2002

Dendritic cell maturation in active immunotherapy strategies.

Dendritic cells (DCs) loaded with tumour antigen have become the centrepiece of clinical trials testing active immunotherapy strategies. Important variables include the source of DCs, the choice of antigens, the method of antigen loading and the route and timing of administration. Recently, the requirement for and the method of, DC maturation have been receiving particular attention. This is due to observations from in vitro studies and animal models demonstrating that mature DCs induce more potent antigen-specific T-cells responses than immature DCs. Furthermore, preliminary observations in human studies suggest that immature DCs might actually downregulate antigen-specific T-cell responses but mature DCs may augment them. Current studies are addressing how to define DC maturation, whether the variety of methods for maturation result in DCs with similar T-cell stimulatory capacity, how to maintain the maturational status and whether maturation in vitro before immunisation, or in vivo, after immunisation, results in better DC function.

Animals↗
PubMed2002

Current status of adoptive immunotherapy of malignancies.

Adoptive immunotherapy involves the transfer of immune effectors with antitumour activity into the tumour bearing host. Early approaches such as lymphokine activator killer (LAK) cells and tumour infiltrating lymphocytes (TILs) have yielded occasional clinical responses. More recently, attempts to stimulate and/or select antigen-specific T-cells in vitro have demonstrated that tumour-specific adoptive immunotherapy is possible. These approaches require complicated and time consuming in vitro stimulation procedures. Therefore, genetic modification of bulk T-cell populations is an attempt to create a large population of T-cells with a single specificity. In addition to work being done to develop the most potent effector, other studies are working on improving T-cell trafficking to tumours and interfering with the tumour-induced immunosuppression that can impair in vivo T-cell activity.

Animals↗
PubMed2002

Redirecting cytotoxic T lymphocyte responses with T-cell receptor transgenes.

In cancer and viral diseases, a great deal of research has focused on generating T-cell responses that might prove therapeutic. These efforts stem from our understanding of the immune system. It is known that the natural immune response can protect or suppress some viral infections and it is hoped that a potent T-cell mediated immune response might also be harnessed to fight cancer. Immunotherapy is a particularly attractive candidate therapy for the treatment of metastatic cancer because of the immune systems capacity for body wide surveillance. Since the generation of T cell clones is a laborious task and it is often impossible to derive T cell clones of the desired specificity and function from many individuals, especially in a timely fashion required for therapeutic interventions, T-cell receptor (TCR) gene transfer has a lot of appeal. TCR gene transfer seeks to transfer the antigen specificity of a T cell clone to other T cells. This article will review the last 15 years of research in TCR gene transfer since the first successful TCR gene transfer experiment, and seeks to give an insight into the areas of investigation currently being pursued to improve on current results and move TCR gene transfer into the clinic.

Animals↗
PubMed2002

Immunoregulatory T cells in cancer immunotherapy.

Many of the tumour antigens targeted by active immunisation strategies are in fact self-antigens. Successful anticancer immunotherapy will therefore require not only potent methods of T cell activation, but also successful interference with mechanisms of immune tolerance that have evolved to prevent tissue destruction by autoreactive T cells. In addition to thymic deletion, anergy and skewing of T cell cytokine expression, a role for immunoregulatory T cells in the maintenance of self-tolerance has been suggested. Suppression of autoreactive T cells by regulatory T cells has been suggested to occur by both cytokine and cell-contact-dependent mechanisms. In murine models, suppression of auto-reactive T cells mediated by cell contact has been attributed to a population of spontaneously occurring CD4+CD25+ T cells. Cells with similar phenotype and function have been found in healthy humans. In murine models, these cells behave as regulatory T cells, counteracting autoimmune and inflammatory reactions, and have a role in tolerance and in peripheral T cell homeostasis. Of interest for cancer immunotherapy is the fact that depleting these cells results in the induction of antitumour immune responses, particularly after tumour specific vaccination. One hypothesis is that depleting these CD4+CD25+ counter-regulatory T cells in humans with cancer will enhance the efficacy of anticancer immunisations.

Animals↗
PubMed2002

Multiple signals are required for maturation of human dendritic cells mobilized in vivo with Flt3 ligand.

The ligand for the receptor tyrosine kinase fms-like tyrosine kinase 3 (Flt3L) is a growth factor for hematopoietic progenitors and induces expansion of the two distinct lineages of dendritic cells (DC) that have been described in humans. These two lineages, DC1 and DC2, have been described according to their ability to induce naive T cell differentiation to T helper cell type 1 (Th1) and Th2 effector cells, respectively. The immunoregulatory potential of DC1 and DC2 depends on their state of maturation and activation, which can be mediated by several molecules. Because monocyte-derived DC1 produce interleukin-12 (IL-12) when stimulated with CD40 ligand (CD40L), we hypothesized that similar results would be obtained with DC1 mobilized by Flt3L. Unexpectedly, we found that immature DC expanded in vivo by Flt3L treatment could not be stimulated to produce IL-12 in vitro using CD40L and/or interferon-gamma (IFN-gamma) alone. Instead, we found that Flt3L-mobilized DC from cancer patients require a sequence of specific signals for maturation, which included initial treatment with granulocyte macrophage-colony stimulating factor followed by a combination of maturation signals such as CD40L and IFN-gamma. Flt3L-mobilized DC matured in this manner possessed greater T cell-stimulatory function than nonmatured DC. The ability to generate phenotypically mature, IL-12-producing DC1 from peripheral blood mononuclear cells mobilized by Flt3L will have important implications for the development of effective cancer immunotherapy strategies.

Antigens, CD↗
PubMedDate not supplied

Current status of dendritic cell immunotherapy of malignancies.

Because dendritic cells (DC) are central to the induction of antigen-specific T cell responses, their use for the active immunotherapy of malignancies has been of considerable interest. Since clinical trials with DC-based vaccines have been initiated, a number of important developmental issues have become apparent. These include the ideal source and type of DC, the form of antigen and method of loading DC, whether to induce maturation, the route and timing of immunization, and the optimal clinical scenario. Clinical responses such as stability of disease and tumor regressions have been reported in some patients, particularly with melanoma, myeloma, and prostate cancer.

Clinical Trials as Topic↗
PubMedDate not supplied

Redirecting T lymphocyte specificity using T cell receptor genes.

Redirecting T cells by transferring T cell receptor (TCR) genes from tumor-associated antigen (TAA)-reactive T cell clones into human peripheral blood lymphocytes (PBL) has therapeutic potential for the treatment of diseases, including cancer. T cell specificity can be altered using retroviruses encoding TCRalpha and TCRbeta chain genes, or chimeric immunoglobulin (cIg) genes containing signaling domains of CD3 zeta or Fc epsilon RI-gamma. This review evaluates recent studies using TCRs and cIgs to redirect T cell specificity and discusses some of the technical and biological hurdles that need to be addressed before these approaches can be successfully used to treat patients.

Humans↗
PubMedDate not supplied

Dendritic cell-based immunotherapy.

Dendritic cells (DCs) play a crucial role in the induction of antigen-specific T-cell responses, and therefore their use for the active immunotherapy of malignancies has been studied with considerable interest. More than a decade has passed since the publication of the first clinical data of DC-based vaccines, and through this and subsequent studies, a number of important developmental insights have been gleaned. These include the ideal source and type of DCs, the discovery of novel antigens and methods of loading DCs, the role of DC maturation, and the most efficient route of immunization. The generation of immune responses against tumor antigens after DC immunization has been demonstrated, and favorable clinical responses have been reported in some patients; however, it is difficult to pool the results as a whole, and thus the body of data remains inconclusive, in part because of varying DC preparation and vaccination protocols, the use of different forms of antigens, and, most importantly, a lack of rigorous criteria for defining clinical responses. As such, the standardization of clinical and immunologic criteria utilized, as well as DC preparations employed, will allow for the comparison of results across multiple clinical studies and is required in order for future trials to measure the true value and role of this treatment modality. In addition, issues regarding the optimal dose and clinical setting for the application of DC vaccines remain to be resolved, and recent clinical studies have been designed to begin to address these questions.

Antigen Presentation↗
PubMedDate not supplied

Enumerating antigen-specific T-cell responses in peripheral blood: a comparison of peptide MHC Tetramer, ELISpot, and intracellular cytokine analysis.

Detection of the circulating antigen-specific T-cell response to immunization is an important biologic end point in clinical trials of cancer vaccines. Typically employed assays are peptide MHC tetramer, ELISpot, and intracellular cytokine analysis. Although there is no agreement on the definition of a positive response in these assays, many groups have chosen a number of T cells greater than 2 standard deviations above the mean of the negative controls. The authors wished to determine how well this cutoff performed for each of these assays in detecting positive and negative T-cell responses to a model antigen, the immunodominant HLA-A*0201-restricted epitope of cytomegalovirus (CMV) pp65. For each assay, the mean + 2 standard deviations of the response for CMV seronegatives was the point that best separated the two groups. Using this value, each assay had a sensitivity of 87.5% and specificity of 95% to 100% and exhibited a high degree of concordance (kappa 0.76-0.9) with the other two. The authors conclude that currently available immunologic assays perform well in detecting biologically relevant levels of antigen-specific T cells. These assays will better define the quantity and quality of protective immune responses to viral disease and offer insight into the requirements for protective anti-cancer immunity.

Antigens↗