Vaccination of B-CLL patients with autologous dendritic cells can change the frequency of leukemia antigen-specific CD8+ T cells as well as CD4+CD25+FoxP3+ regulatory T cells toward an antileukemia response

Changing paradigms in the treatment of chronic lymphocytic leukemia

Progress in our understanding of chronic lymphocytic leukemia and its treatment has resulted in a more tailored approach to patient management, with different therapeutic regimens for different patient populations. The current standard of care has evolved from single-agent therapy with chlorambucil or cyclophosphamide, through the introduction of purine analogs to the more recent introduction of chemoimmunotherapy. Selection of appropriate initial therapy should be based primarily on patient characteristics such as age, performance status and the expected clinical course of the leukemia based on established risk factors. Achieving a complete and durable response is the major goal for fit patients; chemoimmunotherapy with fludarabine, cyclophosphamide and rituximab would be advantageous. Alternatively, in unfit patients, controlling symptoms is the essential treatment goal and a regimen with a more favorable toxicity profile should be applied. This manuscript reviews the data that has lead to current treatment choices, advises on tailored therapies and discusses emerging trends. Data for this review was identified by a search of electronic information including Medline and PubMed databases, conference proceedings and trial registers. Critical analysis of extracted data was undertaken with attention to trial phase, treatment schedules and end points, including response rates, follow-up times, progression-free survival and overall survival.

Peptide vaccines for patients with acute myeloid leukemia

The majority of patients with acute myeloid leukemia (AML) under 60 years of age reach a complete hematological remission after intensive chemotherapy. However, only 20-40% of all patients with AML achieve a disease-free survival of more than 5 years. The graft-versus-leukemia effect observed after allogeneic stem cell transplantation and donor lymphocyte infusions strongly suggests that T lymphocytes play a major role in the rejection of leukemic cells. Vaccination with leukemia-associated antigen (LAA) peptides might constitute a way to augment the graft-versus-leukemia effect. Peptide vaccination causes no major side effects, which is of particular note as most AML patients are people over 60 years of age, often suffering from concomitant disease. This review summarizes approaches to define appropriate LAAs as targets of a T-cell-based vaccine immunotherapy. Current clinical LAA peptide vaccination protocols targeting Wilms' tumor gene, proteinase-3 and the receptor for hyaluronan-mediated motility are reviewed and an outlook to dendritic cells, adjuvants and short oligodenucleotides is given.

Immune responses in patients with metastatic renal cell carcinoma treated with dendritic cells pulsed with tumor lysate

Patients with metastatic renal cell carcinoma (mRCC) have a limited life expectancy but still a subset of these patients develop immune and clinical responses after immunotherapy including dendritic cell (DC) vaccination. In a recently published phase I/II trials, fourteen HLA-A2 negative patients with progressive mRCC were vaccinated with autologous DC pulsed with allogeneic tumour lysate. Low-dose IL-2 administered subcutaneously was given concomitantly. In this study, we analysed lysate specific proliferation of PBMCs from these patients together with the TH1/TH2 balance of the responding T cells. Also, serum concentrations of IL-10, IL-12, IL-15, IL-17 and IL-18 from these patients and additional thirteen HLA-A2 positive mRCC patients treated with autologous DC pulsed with survivin and telomerase peptides were analysed during vaccination to identify systemic immune responses and potential response biomarkers. In HLA-A2 negative mRCC patients a spontaneous predominance of TH1 secreting tumour lysate specific T cells was observed prior to vaccination in patients attaining stable disease (SD) during treatment whereas patients with continued progressive disease (PD) had a mixed TH1/TH2 response. The TH1/TH2 balance was unchanged during vaccination also when tumour lysate specific T cell responses increased. An increase in IL-12, IL-17 and IL-18 serum concentrations was observed during vaccination but no difference between patients with SD and PD was observed. IL-10 or IL-15 was not measurable in serum.

Lymphoma immunotherapy: vaccines, adoptive cell transfer and immunotransplant

Therapy for non-Hodgkin lymphoma has benefited greatly from basic science and clinical research such that chemotherapy and monoclonal antibody therapy have changed some lymphoma subtypes from uniformly lethal to curable, but the majority of lymphoma patients remain incurable. Novel therapies with less toxicity and more specific targeting of tumor cells are needed and immunotherapy is among the most promising of these. Recently completed randomized trials of idiotype vaccines and earlier-phase trials of other vaccine types have shown the ability to induce antitumor T cells and some clinical responses. More recently, trials of adoptive transfer of antitumor T cells have demonstrated techniques to increase the persistence and antitumor effect of these cells. Herein, we discuss lymphoma immunotherapy clinical trial results and what lessons can be taken to improve their effect, including the combination of vaccination and adoptive transfer in an approach we have dubbed 'immunotransplant'.

Application of Interleukin-12 Expressing Dendritic Cells for the Treatment of Animal Model of Leukemia

Residual cancer cells appearing in blood circulation reduce the effects of radiotherapy or chemotherapy in cancer patients. It has been well documented that cultured dendritic cells can be used as a powerful tool to induce immune response. In this study, we administered different manipulations of dendritic cells (DCs), including DCs pulsed with tumor cell lysate (TCL), transfected with adenoviral IL-12 vector (AdIL-12) and transfected with AdIL-12 after being pulsed with TCL, to determine whether improved DCs based immunotherapy can specifically suppress the metastasis of tumor cells. The results demonstrated that administration of engineered DCs that transfected with AdIL-12 after being pulsed with TCL to mice with leukemia had a better protective effect than that of DCs either pulsed with TCL or transfected with AdIL-12. Moreover, depletion of CD8+ cells in the engineered DCs administered leukemia mice reduced the protective effect. These results suggest that DCs modified with TCL and AdIL-12 can prolong survival time by enhancing the activity of cytotoxic T cells. Although more studies on the mechanisms are needed, cytokine genes engineered DCs provide a promising therapeutic potential on the murine model of leukemia.

SCID mice model in vivo evaluation of autologous and allogeneic dendritic cells activity on B-cell chronic lymphocytic leukemia

In the present study we investigated in vivo therapeutic potential of DCs vaccines in B-cell chronic lymphocytic leukemia (B-CLL). On the day 0 the SCID mice were intraperitoneally inoculated with peripheral blood mononuclear cells (PBMC) of B-CLL patients at a dose of 10-30 x 10(6) and left untreated (controls) or i.p. injected on the day 7 with 0.2 - 14.0 x 10(6) dendritic cells. DCs were generated in vitro from peripheral blood monocytes of B-CLL donors (autologous DCs) or healthy donors (allogeneic cells) and pulsed with B-CLL antigens. On the day 14, the effect of implanted cells interactions was evaluated by a counting of CD19+CD5+ human leukemic cells and human T cells in the peritoneal fluid of mice. We found, that mean numbers of CD19+CD5+ leukemic cells as well as human T cells were lowered in peritoneal fluid of mice treated with allogeneic APCs. However, we did not observe similar effects with autologous DCs.

Vaccine therapy and chronic lymphocytic leukaemia

B-cell chronic lymphocytic leukaemia (CLL) should be an ideal target for immune-mediated responses. CLL arises from B cells that can act as antigen-presenting cells (APCs), expresses unique tumour antigens, and has been shown to be a target of the allogeneic T cells which mediate a graft-versus-leukaemia effect. Despite these potential benefits, immune responses against CLL cells have been difficult to elicit. CLL induces immune defects in the host, the tumour cells are inefficient APCs, and therapies given to patients with CLL are themselves immunosuppressive. Successful vaccination approaches in this disease will require steps to overcome these difficulties, including identification of the targets of immune responses in this disease to enable monitoring of the immune response after vaccination, improved presentation of antigens, and steps to improve the immune defects that accompany this disease.

Development of a dendritic cell-based vaccine for chronic lymphocytic leukemia

Evidence for the existence of CLL-specific antigens recognized by the immune system can be gathered from the observation that many patients display monoclonal or oligoclonal expansions and skewed repertoire of T cells. In vitro functional studies have shown that tumor-specific T-cells are able to lyse the leukemic cells. Antileukemic cellular immunity may be boosted in vivo using dendritic cell-based immunotherapy. Our preclinical studies provide evidence that DC that had endocytosed apoptotic CLL cells (Apo-DC) were superior to fusion hybrids, tumor lysate or RNA in eliciting antileukemic T-cell responses in vitro. We have validated a method for enriching the small number of monocyte precursors present in the peripheral blood of CLL patients and utilize them for generating individualized, Apo-DC cellular vaccines. In most cases, a minimum of 50 x 10(6) Apo-DC could be generated, beginning with immunomagnetically enriched monocytes from a single leukapheresis product containing at least 1% CD14+ cells. Cryopreservation and thawing did not affect the phenotype or the T cell stimulatory function of Apo-DC. A phase I/II, open label clinical trial examining the feasibility, safety and immunogenicity of Apo-DC vaccination has been initiated. CLL patients receive 10(7) Apo-DC for at least five immunizations and monitored clinically and immunologically for 52 weeks. Three cohorts are accrued stepwise. Cohort I receives Apo-DC alone; Cohort II: Apo-DC+ repeated doses of low-dose GM-CSF; Cohort III: low-dose cyclophosphamide followed by Apo-DC + GM-CSF.