In elderly acute myeloid leukemia (AML) patients post-remission treatment options are associated with high comorbidity rates and poor survival. Dendritic cell (DC)-based immunotherapy is a promising ...alternative treatment strategy. A novel allogeneic DC vaccine, DCP-001, was developed from an AML-derived cell line that uniquely combines the positive features of allogeneic DC vaccines and expression of multi-leukemia-associated antigens. Here, we present data from a phase I study conducted with DCP-001 in 12 advanced-stage elderly AML patients. Patients enrolled were in complete remission (CR1/CR2) (
n
= 5) or had smoldering disease (
n
= 7). All patients were at high risk of relapse and ineligible for post-remission intensification therapies. A standard 3 + 3 dose escalation design with extension to six patients in the highest dose was performed. Patients received four biweekly intradermal DCP-001 injections at different dose levels (10, 25, and 50 million cells DCP-001) and were monitored for clinical and immunological responses. Primary objectives of the study (feasibility and safety) were achieved with 10/12 patients completing the vaccination program. Treatment was well tolerated. A clear-cut distinction between patients with and without detectable circulating leukemic blasts during the vaccination period was noted. Patients with no circulating blasts showed an unusually prolonged survival median overall survival 36 months (range 7–63) from the start of vaccination whereas patients with circulating blasts, died within 6 months. Long-term survival was correlated with maintained T cell levels and induction of multi-functional immune responses. It is concluded that DCP-001 in elderly AML patients is safe, feasible and generates both cellular and humoral immune responses.
A striking example of the relationship between regulation of transcription and phenotype is the central role of the Y-chromosomal gene Sry in mammalian sex determination. Sry is the founding member ...of a large family of so-called Sox genes. During murine embryogenesis, the transcriptional activator Sox-4 is expressed at several sites, but in adult mice expression is restricted to immature B and T lymphocytes. Using targeted gene distruption, we have found that SOX-4(-/-) embryos succumb to circulatory failure at day E14. This was a result of impaired development of the endocardial ridges (a specific site of Sox-4 expression) into the semilunar valves and the outlet portion of the muscular ventricular septum. The observed range of septation defects is known as 'common arterial trunk' in man. We studied haemopoiesis in lethally irradiated mice reconstituted with SOX-4(-/-) fetal liver cells and found that a specific block occurred in B-cell development at the pro-B cell stage. In line with this, the frequency and proliferative capacity of IL-7-responsive B cell progenitors in fetal liver were severely decreased in vitro.
Many tumor-associated antigens are derived from nonmutated "self" proteins. T cells infiltrating tumor deposits recognize self-antigens presented by tumor cells and can be expanded in vivo with ...vaccination. These T cells exist in a functionally tolerant state, as they rarely result in tumor eradication. We found that tumor growth and lethality were unchanged in mice even after adoptive transfer of large numbers of T cells specific for an MHC class I-restricted epitope of the self/tumor antigen gp100. We sought to develop new strategies that would reverse the functionally tolerant state of self/tumor antigen-reactive T cells and enable the destruction of large (with products of perpendicular diameters of >50 mm2), subcutaneous, unmanipulated, poorly immunogenic B16 tumors that were established for up to 14 d before the start of treatment. We have defined three elements that are all strictly necessary to induce tumor regression in this model: (a) adoptive transfer of tumor-specific T cells; (b) T cell stimulation through antigen-specific vaccination with an altered peptide ligand, rather than the native self-peptide; and (c) coadministration of a T cell growth and activation factor. Cells, vaccination, or cyto-kine given alone or any two in combination were insufficient to induce tumor destruction. Autoimmune vitiligo was observed in mice cured of their disease. These findings illustrate that adoptive transfer of T cells and IL-2 can augment the function of a cancer vaccine. Furthermore, these data represent the first demonstration of complete cures of large, established, poorly immunogenic, unmanipulated solid tumors using T cells specific for a true self/tumor antigen and form the basis for a new approach to the treatment of patients with cancer.
Heat shock protein gp96 primes class I restricted cytotoxic T cells against antigens present in the cells from which it was isolated. Moreover, gp96 derived from certain tumors functions as an ...effective vaccine, causing complete tumor regressions in in vivo tumor challange protocols. Because tumor-derived gp96 did not differ from gp96 isolated from normal tissues, a role for gp96 as a peptide carrier has been proposed. To test this hypothesis, we analyzed whether such an association of antigenic peptides with gp96 occurs in a well-defined viral model system. Here we present the full characterization of an antigenic peptide that endogenously associates with the stress protein gp96 in cells infected with vesicular stomatitis virus (VSV). This peptide is identical to the immunodominant peptide of VSV, which is also naturally presented by H-2Kb major histocompatibility complex class I molecules. This peptide associates with gp96 in VSV-infected cells regardless of the major histocompatibility complex haplotype of the cell. Our observations provide a biochemical basis for the vaccine function of gp96.
Progression of immature CD4(-)CD8(-) thymocytes beyond the beta-selection checkpoint to the CD4(+)CD8(+) stage requires activation of the pre-TCR complex; however, few of the DNA-binding proteins ...that serve as molecular effectors of those pre-TCR signals have been identified. We demonstrate in this study that members of the early growth response (Egr) family of transcription factors are critical effectors of the signals that promote this developmental transition. Specifically, the induction of three Egr family members (Egr1, 2, and 3) correlates with pre-TCR activation and development of CD4(-)CD8(-) thymocytes beyond the beta-selection checkpoint. Enforced expression of each of these Egr factors is able to bypass the block in thymocyte development associated with defective pre-TCR function. However, Egr family members may play somewhat distinct roles in promoting thymocyte development, because there are differences in the genes modulated by enforced expression of particular Egr factors. Finally, interfering with Egr function using dominant-negative proteins disrupts thymocyte development from the CD4(-)CD8(-) to the CD4(+)CD8(+) stage. Taken together, these data demonstrate that the Egr proteins play an essential role in executing the differentiation program initiated by pre-TCR signaling.
Signaling through the pre-TCR is essential for early T cell development and is severely impaired in mice lacking the CD3γ chain of the pre-TCR. We here address the molecular mechanisms underlying ...this defect. Impaired pre-TCR signaling is shown to be associated with a profound increase in the number of apoptotic CD4
−CD8
− (DN) thymocytes. Introduction of p53 deficiency into CD3γ-deficient mice completely reverses the cell survival defect in CD3γ-deficient DN thymocytes and rescues the block in pre-T cell differentiation. In addition, the CD4
+CD8
+ (DP) compartment is expanded to its normal size. These findings suggest that the pre-TCR regulates progression through the DNA-damage checkpoint of the DN to DP transition by inactivating p53.
E12 and E47 are two helix-loop-helix transcription factors that arise by alternative splicing of the E2A gene. Both have been implicated in the regulation of immunoglobulin gene expression. We have ...now generated E2A (-/-) mice by gene targeting. E2A-null mutant mice fail to generate mature B cells. The arrest of B cell development occurs at an early stage, since no immunoglobulin DJ rearrangements can be detected in homozygous mutant mice. While immunoglobulin germline I mu RAG-1, mb-1, CD19, and lambda 5 transcripts are dramatically reduced in fetal livers of E2A (-/-) mice, B29 and mu degrees transcripts are present, but at lower levels. In addition, we show that Pax-5 transcripts are significantly reduced in fetal livers of E2A (-/-) mice. These data suggest a crucial role for E2A products as central regulators in early B cell differentiation.
The embryonic thymic microenvironment provides the necessary elements for T cell lineage commitment, but the precise role of individual stromal cell components remains to be determined. Here we ...address the question of which stromal cell types are required for initiation of V–DJ rearrangements of the TCR-β and TCR-δ locus in CD117
+CD45
+ uncommitted fetal liver progenitors. We show that fetal thymic stroma alone is necessary and sufficient for induction of TCR-β and TCR-δ rearrangements. Furthermore, the ability to induce this T cell commitment step is confined to a subset of MHC class II–positive epithelial cells. Thymic stroma derived from mice with a targeted deletion in the IL-7 gene, however, lacks this ability. These findings set the stage for a further definition of the nature of the thymic stromal cell support in the regulation of T cell commitment.
Experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, is primarily mediated by CD4 T cells specific for Ags in the CNS. Using MHC class II tetramers, we assessed ...expansion and phenotypic differentiation of polyclonal self-reactive CD4 T cells during EAE after primary and secondary challenge with the specific Ag. After EAE induction in SJL mice with proteolipid protein 139-151, CNS-specific T cells up-regulated activation markers and expanded in the draining lymph nodes and in the spleen. Less than 20% of total autoreactive T cells entered the CNS simultaneously with Th cells of other specificities. Almost all tetramer-positive cells in the CNS were activated and phenotypically distinct from the large peripheral pool. When EAE was induced in Ag-experienced mice, disease symptoms developed earlier and persisted longer; autoreactive T cells were more rapidly activated and invaded the CNS earlier. In striking contrast to specific CTLs that respond after secondary viral challenge, the absolute numbers of autoreactive CD4 T cells were not increased, indicating that the accelerated autoreactivity in Ag-experienced mice is not related to higher frequencies of autoreactive CD4 T cells.
The role of memory T cells during the immune response against random antigenic variants has not been resolved. Here, we show by simultaneous staining with two tetrameric major histocompatibility ...complex (MHC)-peptide molecules, that the polyclonal CD8(+) T cell response against a series of natural variants of the influenza A nucleoprotein epitope is completely dominated by infrequent cross-reactive T cells that expand from an original memory population. Based on both biochemical and functional criteria, these cross-reactive cytotoxic T cells productively recognize both the parental and the mutant epitope in vitro and in vivo. These results provide direct evidence that the repertoire of antigen-specific T cells used during an infection critically depends on prior antigen encounters, and indicate that polyclonal memory T cell populations can provide protection against a range of antigenic variants.
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