Surrogate markers of effective anti-tumor immunity.
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Antigens, Neoplasm↗
Biomedical subjects
H K Lyerly
Publications and source records attributed to H K Lyerly.
Direct detection of cellular immune responses to cancer vaccines.
The evaluation of cancer immunotherapy is predicated on the hypothesis that markers of tumor antigen-specific T-cell immunity will cone-late with clinical efficacy. Establishing which candidate vaccines should enter large-scale clinical trials will necessitate optimal application of immunologic monitoring assays. Evidence suggests that available techniques are adequate for the direct detection of clinically significant antigen-specific T-cell responses from tissue specimens. To achieve this goal, it is important to have an understanding of individual methods and their limitations, to include appropriate control antigens in the monitoring strategy, and to incorporate statistical considerations into the design and analysis of such studies.
Cancer Vaccines↗
Molecular basis for cell tropism of CXCR4-dependent human immunodeficiency virus type 1 isolates.
Laboratory isolates of human immunodeficiency virus type 1 (HIV-1) that utilize CXCR4 as a coreceptor infect primary human macrophages inefficiently even though these express a low but detectable level of cell surface CXCR4. In contrast, infection of primary macrophages by primary CXCR4-tropic HIV-1 isolates is readily detectable. Here, we provide evidence suggesting that this difference in cell tropism results from a higher requirement for cell surface CXCR4 for infection by laboratory HIV-1 isolates. Transfected COS7 cells that express a high level of CD4 but a low level of CXCR4 were infected significantly more efficiently by two primary CXCR4-tropic HIV-1 isolates compared to the prototypic laboratory HIV-1 isolate IIIB. More importantly, overexpression of either wild-type or signaling-defective CXCR4 on primary macrophages dramatically enhanced the efficiency of infection by the laboratory HIV-1 isolate yet only modestly enhanced infection by either primary CXCR4-tropic virus. Overexpression of CD4 had, in contrast, only a limited effect on macrophage infection by the laboratory HIV-1, although infection by the primary isolates was markedly enhanced. We therefore conclude that the laboratory CXCR4-tropic HIV-1 isolate exhibits a significantly higher CXCR4 requirement for efficient infection than do the primary CXCR4-tropic isolates and that this difference can explain the poor ability of the laboratory HIV-1 isolate to replicate in primary macrophages. More generally, we propose that the cell tropisms displayed by different strains of HIV-1 in culture can largely be explained on the basis of differential requirements for cell surface CD4 and/or coreceptor expression levels.
Animals↗
Monitoring cellular immune responses to cancer immunotherapy.
Many clinical trials are testing the feasibility of stimulating the immune system to treat cancer. Although the efficacy of this approach will ultimately be determined by clinically relevant endpoints, detection of the magnitude and activity of the immune response is an important intermediate point in the development of these strategies. Assays that predict clinically relevant endpoints are particularly desirable for helping to determine which strategies should ultimately be tested in larger randomized clinical trials. In this review, we will discuss these cellular immunological assays and the current status of their role in clinical trials of immunotherapy.
Animals↗
Assays for monitoring cellular immune responses to active immunotherapy of cancer.
Numerous cancer immunotherapy strategies are currently being tested in clinical trials. Although clinical efficacy will be the final test of these approaches, the long and complicated developmental pathway for these agents necessitates evaluating immunological responses as intermediate markers of the most likely candidates for success. This has emphasized the need for assays that accurately detect and quantitate T cell-mediated, antigen-specific immune responses. This review evaluates the currently used in vivo and in vitro methods of assessing T-cell number and function, including delayed-type hypersensitivity, tetramer analysis, ELISPOT, flow cytometry-based analysis of cytokine expression, and PCR-based detection of T-cell receptor gene usage or cytokine production. We provide examples of how each has been used to monitor recent clinical trials and a discussion of how well each correlates with clinical outcome.
Cytokines↗
Quantitating therapeutically relevant T-cell responses to cancer vaccines.
Successful application of active immunotherapy to the treatment of cancer will require stimulation of potent antigen-specific T-cell responses. It is not known how numerous or how potent these T cells must be in order to abrogate tumors, but the levels of immunity needed to control chronic viral infections may provide estimates for comparison. Evaluation of the efficacy of a vaccine strategy in attaining these levels of immunity will depend on the use of assays that create a picture of T-cell number and function that correlates with clinical outcomes. We discuss the currently available in vivo and in vitro T-cell assays and their relevance for detecting therapeutic levels of T-cell activity. We also propose a strategy for efficiently evaluating the immunologic efficacy of cancer vaccines so that the most promising candidates can be brought more rapidly into definitive clinical trials.
Cancer Vaccines↗
Preoperative mobilization of circulating dendritic cells by Flt3 ligand administration to patients with metastatic colon cancer.
PURPOSE: To evaluate preoperative dendritic cell (DC) mobilization and tumor infiltration after administration of Flt3 ligand (Flt3L) to patients with metastatic colon cancer. PATIENTS AND METHODS: Twelve patients with colon cancer metastatic to the liver or lung received Flt3L (20 microg/kg/d subcutaneously for 14 days for one to three cycles at monthly intervals) before attempted metastasectomy. The number and phenotype of DCs mobilized into peripheral-blood mononuclear cells (PBMCs) were evaluated by flow cytometry. After surgical resection, metastatic tumor tissue was evaluated for DC infiltration. In vivo immune responses to recall antigens were measured. RESULTS: After Flt3L administration, on average, the total number of leukocytes in the peripheral blood increased from 5.9 +/- 1.0 x 10(3)/mm(3) to 11.2 +/- 3.8 x 10(3)/mm(3) (mean +/- SD, P: =. 0001). The percentage of CD11c(+)CD14(-) DCs in PBMCs increased from 2.4% +/- 1.8% to 8.8% +/- 4.7% (P: =.004). Delayed-type hypersensitivity (DTH) responses to recall antigens (CANDIDA:, mumps, and tetanus) showed marginally significant increases in reactivity after Flt3L administration (P: =.06, P: =.03, and P: =.08, respectively). An increase in the number of DCs was observed at the periphery of the tumors of patients who received Flt3L compared with those of patients who had not. CONCLUSION: Flt3L is capable of mobilizing DCs into the peripheral blood of patients with metastatic colon cancer and may be associated with increases in DC infiltration in the peritumoral regions. Flt3L mobilization is associated with a trend toward increased DTH responses to recall antigens in vivo. The use of Flt3L to increase circulating DCs for cancer immunotherapy should be considered.
Adjuvants, Immunologic↗
A subset of human monocyte-derived dendritic cells expresses high levels of interleukin-12 in response to combined CD40 ligand and interferon-gamma treatment.
Dendritic cells (DCs) may arise from multiple lineages and progress through a series of intermediate stages until fully mature, at which time they are capable of optimal antigen presentation and T-cell activation. High cell surface expression of CD83 is presumed to correlate with full maturation of DCs, and a number of agents have been shown to increase CD83 expression on DCs. We hypothesized that interleukin 12 (IL-12) expression would be a more accurate marker of functionally mature DCs capable of activating antigen-specific T cells. We used combinations of signaling through CD40, using CD40 ligand trimer (CD40L), and interferon gamma to demonstrate that CD83 expression is necessary but not sufficient for optimal production of IL-12 by DCs. Phenotypically mature DCs could be induced to produce high levels of IL-12 p70 only when provided 2 simultaneous stimulatory signals. By intracellular cytokine detection, we determined that only a subset of cells that express high levels of CD80 and CD83 generate large amounts of IL-12. DCs matured with both signals are superior to DCs stimulated with the individual agents in activating antigen-specific T cell in vitro. These findings have important implications regarding the identification, characterization, and clinical application of functionally mature DCs.
Adjuvants, Immunologic↗
Tumor-specific recognition of human myeloma cells by idiotype-induced CD8(+) T cells.
Immunoglobulin secreted by myeloma cells contains a unique antigenic determinant (idiotype [Id]) that may serve as a tumor-specific antigen. Although Id-protein-specific T-cell responses have been reported in patients with myeloma, it is not known whether primary myeloma tumor cells can present naturally processed Id peptides on their surface as a target. We immunized 2 healthy human stem-cell donors with Id proteins from their recipients. T cells from the immunized donors released high levels of T-helper 1-type cytokines in response to stimulation with myeloma cells from their recipients. The T-cell-mediated cytokine response to tumor cells was blocked by a major histocompatibility complex (MHC) class I monoclonal antibody, whereas the response to soluble Id protein was dependent on MHC class II. To investigate whether Id-specific CD8(+) T cells can recognize and kill autologous myeloma cells, we generated T cells from peripheral blood mononuclear cells from a third patient with myeloma by means of in vitro stimulation with autologous dendritic cells pulsed with Id protein. Tumor-specific lysis of myeloma cells was demonstrated by the lack of killing of autologous nonmalignant B cells or natural killer-sensitive K562 cells. Lysis of autologous myeloma targets was restricted by MHC class I molecules. These data represent the first report of class I-restricted T-cell recognition of fresh autologous myeloma targets and formally demonstrate that human myeloma cells can serve as targets of an Id-specific T-cell response. (Blood. 2000;96:2828-2833)
Adult↗
Optimizing dendritic cell function by genetic modification.
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Animals↗
Effect of highly active antiretroviral therapy and thymic transplantation on immunoreconstitution in HIV infection.
The purpose of this study was to determine whether thymic transplantation in addition to highly active antiretroviral therapy (HAART) will restore T cell function in HIV infection. Eight treatment-naive HIV-infected patients with CD4+ T cell counts of 200-500/mm3 were randomized into thymic transplantation and control arms. All patients received HAART (zidovudine, lamivudine, and ritonavir) for 6 weeks prior to transplantation. Thymic transplantation was done without immunosuppression, using postnatal HLA-unmatched cultured allogeneic thymus tissue. Patients were immunized every 6 months with the neoantigen keyhole limpet hemocyanin (KLH) and the recall antigen tetanus toxoid (TT). T cell phenotype and function and T cell receptor rearrangement excision circles (TRECs) were assessed. Thymic allografts were biopsied at 2 months. Six HIV-infected patients completed the study. Four patients received cultured allogeneic postnatal thymic grafts, two others were controls. CD4+ T cell counts increased and T cell-proliferative responses to Candida antigen and TT normalized in all patients. Proliferative responses to KLH developed in three of four transplant recipients and one of two controls. Patients responding to KLH after secondary immunization had greater TREC increases compared with the patients who did not respond. All thymic allografts were rejected within 2 months. In summary, four of six patients developed T cell-proliferative responses to the neoantigen KLH over the first 2 years of HAART. The transplanted thymus tissue, however, was rejected. There was no clear difference in restoration of T cell function in the transplant recipients compared with the controls. Increases in TRECs after initiation of HAART may correlate with improved immune function.
Adult↗
Induction of tumor immunity and cytotoxic T lymphocyte responses using dendritic cells transfected with messenger RNA amplified from tumor cells.
Unique patient-specific tumor antigens may constitute the dominant antigens in the antitumor immune response. Hence, vaccination with the patient's own repertoire of tumor antigens may offer a superior strategy to elicit protective immunity. We have shown previously that dendritic cells transfected with mRNA isolated from tumor cells stimulate potent CTL responses and engender protective immunity in tumor-bearing mice. In the current study, we demonstrate that tumor mRNA, isolated from murine tumor cell lines or from primary human tumor cells microdissected from frozen tissue sections, can be amplified without loss of function. This study provides the foundations for an effective and broadly applicable treatment that does not require the characterization of the relevant antigenic profile in each patient and will not be limited by tumor tissue availability for antigen preparation.
Animals↗
Dendritic cell-based immunization for cancer therapy.
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Animals↗
Blocking the initiation of coagulation by RNA aptamers to factor VIIa.
The tissue factor/factor VIIa complex is thought to be the primary initiator of most physiologic blood coagulation events. Because of its proximal role in this process, we sought to generate new inhibitors of tissue factor/factor VIIa activity by targeting factor VIIa. We employed a combinatorial RNA library and in vitro selection methods to isolate a high affinity, nuclease-resistant RNA ligand that binds specifically to coagulation factor VII/VIIa. This RNA inhibits the tissue factor-dependent activation of factor X by factor VIIa. Kinetic analyses of the mechanism of action of this RNA suggest that it antagonizes factor VIIa activity by preventing formation of a functional factor VII/tissue factor complex. Furthermore, this RNA significantly prolongs the prothrombin time of human plasma in a dose dependent manner, and has an in vitro half-life of approximately 15 h in human plasma. Thus, this RNA ligand represents a novel class of anticoagulant agents directed against factor VIIa.
Base Sequence↗
Clinical applications of dendritic cell vaccines.
Dendritic cells play a central role in the presentation of antigen to naïve T-cells and the induction of primary immune responses. Preclinical studies have established that dendritic cells loaded with antigens ex vivo induce potent antitumor and antiviral immune responses in vitro and in vivo. This has lead to a proliferation of clinical trials testing their effectiveness in humans, particularly with advanced malignancies. The few reported studies suggest that clinically relevant immune responses may be induced against some types of malignancies. Many questions regarding the best type of dendritic cell, degree of maturity, choice of antigen, route and schedule of administration, targeting to lymphoid tissue and use of additional adjuvants will need to be answered in preclinical and clinical studies as the field of dendritic cell-based immunotherapy progresses.
Adjuvants, Immunologic↗
Induction of carcinoembryonic antigen (CEA)-specific cytotoxic T-lymphocyte responses in vitro using autologous dendritic cells loaded with CEA peptide or CEA RNA in patients with metastatic malignancies expressing CEA.
The application of dendritic cells (DC) to the active immunotherapy of cancer currently relies on the generation of potent DC capable of presenting tumor antigens such as carcinoembryonic antigen (CEA). It is unknown whether the T cells of patients with advanced malignancies can be reliably stimulated against tumor antigens by their autologous DC. In this study, starting with the peripheral blood mononuclear cells (PBMC) of patients with metastatic malignancies expressing CEA, autologous DCs were generated in vitro in serum-free media supplemented with GM-CSF and IL-4. The DCs from HLA A2 positive patients were loaded with the CEA peptide CAP-1 and the DCs from HLA A2 negative patients were depleted of bystander lymphocytes and loaded with mRNA encoding CEA. The DC preparations were tested to determine their phenotype and were used to stimulate autologous PBMC twice, separated by 10-14 days. The stimulated cells were then tested for their ability to lyse CEA-expressing target cells. We successfully generated an adequate number of DC for a clinical trial from all patients. The harvested DC preparations contained 49% DC and 87% DC if depleted of bystander lymphocytes. Phenotypic analysis showed the typical pattern of CD11c+ CD40+ CD86+ HLA-DR+ CD80(low) CD83(low) CD14(low). All preparations but one were able to stimulate CEA-specific cytotoxic T-lymphocyte (CTL) activity, suggesting that the majority of patients are not anergic to CEA and possess functional DC. The CTL activity was similar for the CEA peptide and CEA RNA-loaded DC.
Carcinoembryonic Antigen↗
Migration of human dendritic cells after injection in patients with metastatic malignancies.
Present clinical studies of active immunotherapy for malignancies using dendritic cells (DCs) require elucidation of the sites where DCs localize after injection. We evaluated the pattern of distribution of in vitro-generated, antigen-loaded, human DCs labeled with indium-111 oxyquinoline after i.v., s.c., and intradermal injection. Whereas the DCs injected i.v. localized in the lungs and then redistributed to the liver, spleen, and bone marrow, they were not detected in lymph nodes or tumors. A small percentage of DCs injected intradermally migrated rapidly to the regional lymphatics in some individuals. No lymph node activity was detected after s.c. injection. Our results demonstrate that DC distribution to sites of lymphoid tissue is dramatically affected by the mode of administration.
Cell Movement↗
Cellular and biological therapies of gastrointestinal tumors: overview of clinical trials.
Because of the high relapse rate of resected gastrointestinal malignancies and the modest responses of metastatic disease to currently available therapies, biologic agents that harness host-tumor immunologic interactions have received increased attention. Based on promising preclinical data, current clinical trials in cellular and biologic therapies are evaluating the safety and efficacy of passive immunotherapy with tumor-reactive lymphocytes activated ex vivo and active immunotherapy with peptide, viral vector, and cellular vaccines. This review will describe the background, rationale, and experimental approach of these clinical trials. Although equally promising, antibodies, gene therapies, and antiangiogenic strategies will not be discussed.
Adoptive Transfer↗