Dendritic cells: On the move from bench to bedside

Innate immune cellular therapeutics in transplantation

Successful organ transplantation provides an opportunity to extend the lives of patients with end-stage organ failure. Selectively suppressing the donor-specific alloimmune response, however, remains challenging without the continuous use of non-specific immunosuppressive medications, which have multiple adverse effects including elevated risks of infection, chronic kidney injury, cardiovascular disease, and cancer. Efforts to promote allograft tolerance have focused on manipulating the adaptive immune response, but long-term allograft survival rates remain disappointing. In recent years, the innate immune system has become an attractive therapeutic target for the prevention and treatment of transplant organ rejection. Indeed, contemporary studies demonstrate that innate immune cells participate in both the initial alloimmune response and chronic allograft rejection and undergo non-permanent functional reprogramming in a phenomenon termed "trained immunity." Several types of innate immune cells are currently under investigation as potential therapeutics in transplantation, including myeloid-derived suppressor cells, dendritic cells, regulatory macrophages, natural killer cells, and innate lymphoid cells. In this review, we discuss the features and functions of these cell types, with a focus on their role in the alloimmune response. We examine their potential application as therapeutics to prevent or treat allograft rejection, as well as challenges in their clinical translation and future directions for investigation.

Recent Advances in Cancer Vaccines: Challenges, Achievements, and Futuristic Prospects

Cancer is a chronic disease, and it can be lethal due to limited therapeutic options. The conventional treatment options for cancer have numerous challenges, such as a low blood circulation time as well as poor solubility of anticancer drugs. Therapeutic cancer vaccines emerged to try to improve anticancer drugs' efficiency and to deliver them to the target site. Cancer vaccines are considered a viable therapeutic technique for most solid tumors. Vaccines boost antitumor immunity by delivering tumor antigens, nucleic acids, entire cells, and peptides. Cancer vaccines are designed to induce long-term antitumor memory, causing tumor regression, eradicate minimal residual illness, and prevent non-specific or unpleasant effects. These vaccines can assist in the elimination of cancer cells from various organs or organ systems in the body, with minimal risk of tumor recurrence or metastasis. Vaccines and antigens for anticancer therapy are discussed in this review, including current vaccine adjuvants and mechanisms of action for various types of vaccines, such as DNA- or mRNA-based cancer vaccines. Potential applications of these vaccines focusing on their clinical use for better therapeutic efficacy are also discussed along with the latest research available in this field.

In Vitro Generated Dendritic Cells of Leukemic Origin Predict Response to Allogeneic Stem Cell Transplantation in Patients With AML and MDS

Allogeneic stem cell transplantation (alloSCT) is the treatment of choice for many patients with acute myeloid leukemia (AML) and myelodysplastic syndrome. The presentation of leukemic or allospecific antigens by malignant blasts is regarded as a crucial trigger for an effective allogeneic immune response. Conversely, insufficient stimulatory capacity by the leukemic blasts is thought to be a relevant escape mechanism from cellular immunotherapy (alloSCT). Our purpose was to test, whether the ability of malignant blasts to differentiate in vitro toward dendritic cells of leukemic origin (DCleu) is associated with clinical outcome. We isolated leukemic blasts from peripheral blood or bone marrow of AML and myelodysplastic syndrome patients before alloSCT (n=47) or at relapse after alloSCT (n=22). A panel of 6 different assays was used to generate DCleu in vitro. Results were correlated with clinical outcome. DCleu could be generated from all 69 samples. Significantly higher mean frequencies of DCleu were found in clinical long-term responders versus nonresponders to SCT (76.8% vs. 58.8%, P=0.006). Vice versa, the chance for response to SCT was significantly higher, if a DCleu+/dendritic cells (DC) ratio of >50% could be reached in vitro (P=0.004). Those patients were characterized by a longer time to relapse (P=0.04) and by a higher probability for leukemia-free survival (P=0.005). In vitro generation of DC and DCleu from leukemic blasts correlated with the clinical outcome. This observation may support a role of leukemic antigen presentation by "leukemia-derived DC" for the stimulation of an allogeneic immune response in AML.

Cellular transformers for targeted therapy

Employing natural cells as drug carriers has been a hotspot in recent years, attributing to their biocompatibility and inherent dynamic properties. In the earlier stage, cells were mainly used as vehicles by virtue of their lipid-delimited compartmentalized structures and native membrane proteins. The scope emphasis was 'what cell displays' instead of 'how cell changes'. More recently, the dynamic behaviours, such as changes in surface protein patterns, morphologies, polarities and in-situ generation of therapeutics, of natural cells have drawn more attention for developing advanced drug delivery systems by fully taking advantage of these processes. In this review, we revolve around the dynamic cellular transformation behaviours which facilitate targeted therapy. Cellular deformation in geometry shape, spitting smaller vesicles, activation of antigen present cells, polarization between distinct phenotypes, local production of therapeutics, and hybridization with synthetic materials are involved. Other than focusing on the traditional delivery of concrete cargoes, more functional 'handles' that are derived from the cells themselves are introduced, such as information exchange, cellular communication and interactions between cell and extracellular environment.

Progress in Liver Transplant Tolerance and Tolerance-Inducing Cellular Therapies

Liver transplantation is currently the most effective method for treating end-stage liver disease. However, recipients still need long-term immunosuppressive drug treatment to control allogeneic immune rejection, which may cause various complications and affect the long-term survival of the recipient. Many liver transplant researchers constantly pursue the induction of immune tolerance in liver transplant recipients, immunosuppression withdrawal, and the maintenance of good and stable graft function. Although allogeneic liver transplantation is more tolerated than transplantation of other solid organs, and it shows a certain incidence of spontaneous tolerance, there is still great risk for general recipients. With the gradual progress in our understanding of immune regulatory mechanisms, a variety of immune regulatory cells have been discovered, and good results have been obtained in rodent and non-human primate transplant models. As immune cell therapies can induce long-term stable tolerance, they provide a good prospect for the induction of tolerance in clinical liver transplantation. At present, many transplant centers have carried out tolerance-inducing clinical trials in liver transplant recipients, and some have achieved gratifying results. This article will review the current status of liver transplant tolerance and the research progress of different cellular immunotherapies to induce this tolerance, which can provide more support for future clinical applications.

Therapeutic Cancer Vaccination with Ex Vivo RNA-Transfected Dendritic Cells-An Update

Over the last two decades, dendritic cell (DC) vaccination has been studied extensively as active immunotherapy in cancer treatment and has been proven safe in all clinical trials both with respect to short and long-term side effects. For antigen-loading of dendritic cells (DCs) one method is to introduce mRNA coding for the desired antigens. To target the whole antigenic repertoire of a tumor, even the total tumor mRNA of a macrodissected biopsy sample can be used. To date, reports have been published on a total of 781 patients suffering from different tumor entities and HIV-infection, who have been treated with DCs loaded with mRNA. The majority of those were melanoma patients, followed by HIV-infected patients, but leukemias, brain tumors, prostate cancer, renal cell carcinomas, pancreatic cancers and several others have also been treated. Next to antigen-loading, mRNA-electroporation allows a purposeful manipulation of the DCs’ phenotype and function to enhance their immunogenicity. In this review, we intend to give a comprehensive summary of what has been published regarding clinical testing of ex vivo generated mRNA-transfected DCs, with respect to safety and risk/benefit evaluations, choice of tumor antigens and RNA-source, and the design of better DCs for vaccination by transfection of mRNA-encoded functional proteins.

Large-scale production and directed induction of functional dendritic cells ex vivo from serum-free expanded human hematopoietic stem cells

BACKGROUND

Dendritic cells (DCs) that are derived from hematopoietic stem cells (HSCs) are the most potent antigen-presenting cells and play a pivotal role in initiating the immune response. Hence, large-scale production and direct induction of functional DCs ex vivo from HSCs are crucial to HSC research and clinical potential, such as vaccines for cancer and immune therapy.

METHODS

In a previous study, we developed a serum-free HSC expansion system (SF-HSC medium) to expand large numbers of primitive HSCs ex vivo. Herein, a DC induction and expansion medium (DC medium) was proposed to further generate large numbers of functional DCs from serum-free expanded HSCs, which were developed and optimized by factorial design and the steepest ascent method.

RESULTS

The DC medium is composed of effective basal medium (Iscove's modified Dulbecco's medium [IMDM]) and cytokines (2.9 ng/mL stem cell factor [SCF], 2.1 ng/mL Flt-3 ligand, 3.6 ng/mL interleukin [IL]-1β, 19.3 ng/mL granulocyte-macrophage colony-stimulating factor [GM-CSF] and 20.0 ng/mL tumor necrosis factor-α [TNF-α]). After 10-day culture in DC medium, the maximum fold expansion for accumulated CD1a⁺CD11c⁺ DCs was more than 4000-fold, and the induced DCs were characterized and confirmed by analysis of growth kinetics, surface antigen expression, endocytosis ability, mixed lymphocyte reaction, specific cytokine secretion and lipopolysaccharide stimulation.

DISCUSSION

In conclusion, the combination of DC medium and SF-HSC medium can efficiently induce and expand a large amount of functional DCs from a small scale of HSCs and might be a promising source of DCs for vaccine and immune therapy in the near future.

BCL10 in cell survival after DNA damage

The complex defense mechanism of the DNA damage response (DDR) developed by cells during long-term evolution is an important mechanism for maintaining the stability of the genome. Defects in the DDR pathway can lead to the occurrence of various diseases, including tumor development. Most cancer treatments cause DNA damage and apoptosis. However, cancer cells have the natural ability to repair this damage and inhibit apoptosis, ultimately leading to the development of drug resistance. Therefore, investigating the mechanism of DNA damage may contribute markedly to the future treatment of cancer. The CARMA-BCL10-MALT1 (CBM) complex formed by B cell lymphoma/leukemia 10 (BCL10) regulates apoptosis by activating NF-κB signaling. BCL10 is involved in the formation of complexes that antagonize apoptosis and contribute to cell survival after DNA damage, with cytoplasmic BCL10 entering the nucleus to promote DNA damage repair, including histone ubiquitination and the recruitment of homologous recombination (HR) repair factors. This article reviews the role of BCL10 in cell survival following DNA damage.

Utilizing the nanosecond pulse technique to improve antigen intracellular delivery and presentation to treat tongue squamous cell carcinoma

Background

Tongue squamous cell carcinoma is the most common squamous cell carcinoma of the head and neck. Immunotherapy has great potential in the treatment of tongue squamous cell carcinoma because of its unique advantages. However, the efficacy of immunotherapy is limited by the efficiency of antigen phagocytosis by immune cells.

Material and Methods

We extracted dendritic cells (DCs) from human peripheral blood. Utilizing a nanosecond pulsed electric field (nsPEF), we deliver the tumour lysate protein into DCs and then incubate the DCs with PBMCs to obtain specific T cells to kill tumour cells. The biosafety of nsPEF was evaluated by the ANNEXIN V-FITC/PI kit. The efficacy of lysate protein delivery was evaluated by flow cytometry. The antitumour efficacy was tested by CCK-8 assay.

Results

The nsPEF of the appropriate field strength can significantly improve the phagocytic ability of DCs to tumour lysing proteins and have good biosafety. The tumour cell killing rate of the nsPEF group was higher than the other group (p< 0.05).

Conclusions

Utilizing nsPEF to improve the phagocytic and presenting ability of DCs could greatly activate the adaptive immune cells to enhance the immunotherapeutic effect on tongue squamous cell carcinoma.

Key words:Dendritic cell, nsPEF, immunotherapy, squamous cell carcinoma.

A generic RNA pulsed DC based approach for developing therapeutic intervention against nasopharyngeal carcinoma

The recurrent nasopharyngeal carcinoma of head-and-neck cancers pathology showed unique symptoms and clinical characteristics. The complexity of pathology poses challenges for developing therapeutic interventional approaches against nasopharyngeal carcinoma (NPC). The conventional treatment regimens offer limited local control and survival, which, leads to adverse delayed complications. Our study present a generic monocyte derived dendritic cell (MoDC) vaccine strategy for NPC in which RNA is used as a source of tumor-associated antigens (TAAgs). The RNA extracted from well-characterized highly immunogenic NPC cells (C666-1) was transfected into MoDCs. The formulated and characterized cationic liposomes were used to achieving efficient RNA transfection of immature DCs. Further, DCs were forcibly matured with a cytokine cocktail to achieve greater expression of MHC and co-stimulatory molecules. Moreover, our results did not see any effect of RNA or lipids on MoDCs phenotype or cytokine expression. RNA loaded DCs derived from HLA-A2-positive donors were shown to activate effector memory cytotoxic T lymphocytes (CTLs) specific for TAAg ligand expressed by C666-1 cells. Our results show the comparison of cytotoxic response mounted against RNA-loaded DCs with those directly stimulated by C666-1 tumor cells. Our findings suggest that DCs expressing tumor cell RNA primed naïve T cells show T cells priming with lesser cytotoxicity and cytokine secretion when exposed with with C666-1 tumor cells. These results surface the potential of DCs to deliver RNA in NPCs, sufficient presentation of RNA to provoke perdurable immune responses against nasopharyngeal carcinoma. Our results implies that DC based vaccine approach may be useful to develop therapeutic interventional approach in the form of vaccine to address NPCs.

Multimodality Imaging of Bone Marrow-Derived Dendritic Cell Migration and Antitumor Immunity

Here, we sought to monitor bone marrow–derived dendritic cell (BMDC) migration and antitumor effects using a multimodal reporter imaging strategy in living mice. BMDCs were transduced with retroviral vector harboring human sodium iodide symporter (hNIS, nuclear imaging reporter), firefly luc2 (optical imaging reporter), and thy1.1 (surrogate marker of NIS and luc2) genes (BMDC/NF cells). No significant differences in biological functions, including cell proliferation, antigen uptake, phenotype expression, and migration ability, were observed between BMDC and BMDC/NF cells. Combined bioluminescence imaging and I-124 positron emission tomography/computed tomography clearly revealed the migration of BMDC/NF cells to draining popliteal lymph nodes at day 7 postinjection. Interestingly, marked tumor protection was observed in mice immunized with TC-1 lysate-pulsed BMDC/NF cells. Our findings suggested that multimodal reporter gene imaging of NIS and luciferase could provide insights into the biological behaviors of dendritic cells in living organisms and could be a useful tool for the optimization of DC-based immunotherapy protocols.

BCL10 is recruited to sites of DNA damage to facilitate DNA double-strand break repair

Recent studies have found BCL10 can localize to the nucleus and that this is linked to tumor aggression and poorer prognosis. These studies suggest that BCL10 localization plays a novel role in the nucleus that may contribute to cellular transformation and carcinogenesis. In this study, we show that BCL10 functions as part of the DNA damage response (DDR). We found that BCL10 facilitates the rapid recruitment of RPA, BRCA1 and RAD51 to sites of DNA damage. Furthermore, we also found that ATM phosphorylates BCL10 in response to DNA damage. Functionally, BCL10 promoted DNA double-strand breaks repair, enhancing cell survival after DNA damage. Taken together our results suggest a novel role for BCL10 in the repair of DNA lesions.

Direct Delivery of Antigens to Dendritic Cells via Antibodies Specific for Endocytic Receptors as a Promising Strategy for Future Therapies

Dendritic cells (DCs) are the most potent professional antigen presenting cells and are therefore indispensable for the control of immunity. The technique of antibody mediated antigen targeting to DC subsets has been the basis of intense research for more than a decade. Many murine studies have utilized this approach of antigen delivery to various kinds of endocytic receptors of DCs both in vitro and in vivo. Today, it is widely accepted that different DC subsets are important for the induction of select immune responses. Nevertheless, many questions still remain to be answered, such as the actual influence of the targeted receptor on the initiation of the immune response to the delivered antigen. Further efforts to better understand the induction of antigen-specific immune responses will support the transfer of this knowledge into novel treatment strategies for human diseases. In this review, we will discuss the state-of-the-art aspects of the basic principles of antibody mediated antigen targeting approaches. A table will also provide a broad overview of the latest studies using antigen targeting including addressed DC subset, targeted receptors, outcome, and applied coupling techniques.

Improving therapy of chronic lymphocytic leukemia with chimeric antigen receptor T cells

Adoptive cell immunotherapy for the treatment of chronic lymphocytic leukemia (CLL) has heralded a new era of synthetic biology. The infusion of genetically engineered, autologous chimeric antigen receptor (CAR) T cells directed against CD19 expressed by normal and malignant B cells represents a novel approach to cancer therapy. The results of recent clinical trials of CAR T cells in relapsed and refractory CLL have demonstrated long-term disease-free remissions, underscoring the power of harnessing and redirecting the immune system against cancer. This review will briefly summarize T-cell therapies in development for CLL disease. We discuss the role of T-cell function and phenotype, T-cell culture optimization, CAR design, and approaches to potentiate the survival and anti-tumor effects of infused lymphocytes. Future efforts will focus on improving the efficacy of CAR T cells for the treatment of CLL and incorporating adoptive cell immunotherapy into standard medical management of CLL.

Survivin and PSMA Loaded Dendritic Cell Vaccine for the Treatment of Prostate Cancer

Dendritic cell (DC)-based vaccines are a promising therapeutic modality for cancer. Results from recent trials and approval of the first DC vaccine by the U.S. Food and Drugs Administration for prostate cancer have paved the way for DC-based vaccines. A total of 21 hormone refractory prostate cancer (HRPC) patients with a life expectancy >3 months were randomised into two groups. DC loaded with recombinant Prostate Specific Membrane Antigen (rPSMA) and recombinant Survivin (rSurvivin) peptides was administered as an subcutaneous (s.c.) injection (5×10(6) cells). Docetaxel (75 mg/m(2) intravenous (i.v.)) and prednisone (5 mg, bis in die (b.i.d.)) served as control. Clinical and immunological responses were evaluated. Primary endpoints were safety and feasibility; secondary endpoint was overall survival. Responses were evaluated on day 15, day 30, day 60, and day 90. DC vaccination was well tolerated with no signs of grade 2 toxicity. DC vaccination induced delayed-type hypersensitivity reactivity and an immune response in all patients. Objective Response Rate (ORR) by Response Evaluation Criteria in Solid Tumours (RECIST) was 72.7% (8/11) versus 45.4 (5/11) in the docetaxel arm and immune related response criteria (irRC) was 54.5% (6/11) compared with 27.2% (3/11) in the control arm. The DC arm showed stable disease (SD) in 6 patients, progressive disease (PD) in 3 patients, and partial remission (PR) in two patients compared to SD in 5 patients, PD in 6 patients, and PR in none in the docetaxel arm. There was a cellular response, disease stabilization, no adverse events, and partial remission with the rPSMA and rSurvivin primed DC vaccine.

Immunotherapy of rat glioma without accumulation of CD4(+)CD25(+)FOXP3(+) regulatory T cells

Immunotherapy may be used for the treatment of glioblastoma multiforme; however, the induced immune response is inadequate when either T cells or dendritic cells are used alone. In this study, we established a novel vaccine procedure in rats, using dendritic cells pulsed with C6 tumor cell lysates in combination with adoptive transfer of T lymphocytes from syngenic donors. On day 21 after tumor inoculation, all the rats were sacrificed, the brains were harvested for calculation of glioma volume, cytolytic T lymphocyte responses were measured by cytotoxic assay, and the frequency of regulatory T lymphocytes (CD4⁺CD25⁺FOXP3⁺) in the peripheral blood was investigated by flow cytometric analysis. The survival rate of rats bearing C6 glioma was observed. Results showed that the co-immunization strategy had significant anti-tumor potential against the pre-established C6 glioma, and induced a strong cytolytic T lymphocyte response in rats. The frequency of peripheral blood CD4⁺CD25⁺FOXP3⁺ regulatory T lymphocytes was significantly decreased following the combination therapy, and the rats survived for a longer period. Experimental findings indicate that the combined immunotherapy of glioma cell lysate-pulsed dendritic cell vaccination following adoptive transfer of T cells can effectively inhibit the growth of gliomas in rats, boost anti-tumor immunity and produce a sustained immune response while avoiding the accumulation of CD4⁺CD25⁺FOXP3⁺ regulatory T lymphocytes.

MRI tracking of macrophages labeled with glucan particles entrapping a water insoluble paramagnetic Gd-based agent

PURPOSE

This study is aimed at demonstrating the in vivo potential of Gd(III)-loaded glucan particles (Gd-GPs) as magnetic resonance imaging (MRI)-positive agents for labeling and tracking phagocytic cells.

PROCEDURE

GPs were obtained from Saccharomyces cerevisae and loaded with the water-insoluble complex Gd-DOTAMA(C18)2. The uptake kinetics of Gd-GPs by murine macrophages was studied in vitro and the internalization mechanism was assessed by competition assays. The in vivo performance of Gd-GPs was tested at 7.05 T on a mouse model of acute liver inflammation.

RESULTS

The minimum number of Gd-GPs-labeled J774.A1 macrophages detected in vitro by MRI was ca. 300 cells/μl of agar, which is the lowest number ever reported for cells labeled with a positive T1 agent. Intravenous injection of macrophages labeled with Gd-GPs in a mouse model of liver inflammation enabled the MRI visualization of the cellular infiltration in the diseased area.

CONCLUSIONS

Gd-GPs represent a promising platform for tracking macrophages by MRI as a T1 alternative to the golden standard T2-based iron oxide particles.

Dendritic cells derived from pluripotent stem cells: Potential of large scale production

Human pluripotent stem cells (hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, are promising sources for hematopoietic cells due to their unlimited growth capacity and the pluripotency. Dendritic cells (DCs), the unique immune cells in the hematopoietic system, can be loaded with tumor specific antigen and used as vaccine for cancer immunotherapy. While autologous DCs from peripheral blood are limited in cell number, hPSC-derived DCs provide a novel alternative cell source which has the potential for large scale production. This review summarizes recent advances in differentiating hPSCs to DCs through the intermediate stage of hematopoietic stem cells. Step-wise growth factor induction has been used to derive DCs from hPSCs either in suspension culture of embryoid bodies (EBs) or in co-culture with stromal cells. To fulfill the clinical potential of the DCs derived from hPSCs, the bioprocess needs to be scaled up to produce a large number of cells economically under tight quality control. This requires the development of novel bioreactor systems combining guided EB-based differentiation with engineered culture environment. Hence, recent progress in using bioreactors for hPSC lineage-specific differentiation is reviewed. In particular, the potential scale up strategies for the multistage DC differentiation and the effect of shear stress on hPSC differentiation in bioreactors are discussed in detail.

Optimizing dendritic cell-based immunotherapy for cancer

Dendritic cells (DCs) are the most powerful professional antigen-presenting cells and are unique in their capability to initiate, maintain and regulate the intensity of primary immune responses, including specific antitumor responses. Development of practical procedures to prepare sufficient numbers of functional human DCs in culture from the peripheral blood precursors, paved the way for clinical trials to evaluate various DC-based strategies in patients with malignant diseases. However, no definite conclusions regarding the clinical and even immunological efficacy of DC vaccination can be stated, despite the fact that 12 years have passed since the first clinical trial utilizing DCs in cancer patients. Many unanswered questions hamper the development of DC-based vaccines, including the source of DC preparation and protocols for DC generation, activation and loading with tumor antigens, source of tumor antigens, route of vaccine administration and methods of immunomonitoring. Fortunately, in spite of the many obstacles, DC vaccines continue to hold promise for cancer therapy.

Autologous dendritic cell based adoptive immunotherapy of patients with colorectal cancer-A phase I-II study

Dendritic cell-based active immunotherapies of cancer patients are aimed to provoke the proliferation and differentiation of tumor-specific CD4(+) and CD8(+) T-lymphocytes towards protective effector cells. Isolation and in vitro differentiation of circulating blood monocytes has been established a reasonable platform for adoptively transferred DC-based immunotherapies. In the present study the safety and tolerability of vaccination by autologous tumor cell lysates (oncolysate)- or carcinoembriogenic antigen (CEA)-loaded DCs in patients with colorectal cancer was investigated in a phase I-II trial. The study included 12 patients with histologically confirmed colorectal cancer (Dukes B2-C stages). Six of the patients received oncolysate-pulsed, whereas the other six received recombinant CEA-loaded autologous DCs. The potential of the tumor antigen-loaded DCs to provoke the patient's immune system was studied both in vivo and in vitro. The clinical outcome of the therapy evaluated after 7 years revealed that none of the six patients treated with oncolysate-loaded DCs showed relapse of colorectal cancer, whereas three out of the six patients treated with CEA-loaded DCs died because of tumor relapse. Immunization with both the oncolysate- and the CEA-loaded autologous DCs induced measurable immune responses, which could be detected in vivo by cutaneous reactions and in vitro by lymphocyte proliferation assay. Our results show that vaccination by autologous DCs loaded with autologous oncolysates containing various tumor antigens represents a well tolerated therapeutic modality in patients with colorectal cancer without any detectable adverse effects. Demonstration of the efficacy of such therapy needs further studies with increased number of patients.

Combined immunophenotyping and fluorescence in situ hybridization with chromosome-specific DNA probes allows quantification and differentiation of ex vivo generated dendritic cells, leukemia-derived dendritic cells and clonal leukemic cells in patients with acute myeloid leukemia

Antileukemic T-cell responses induced by leukemia-derived dendritic cells (DC(leu)) are variable, due to varying DC/DC(leu) composition/quality. We studied DC/DC(leu) composition/quality after blast culture in four DC media by flow cytometry (FC) and combined fluorescence in situ hybridization/immunophenotyping analysis (FISH-IPA). Both methods showed that DC methods produce variable proportions of DC subtypes. FISH-IPA is an elaborate method to study clonal aberrations in blast/DC cells on slides, however without preselection of distinct cell populations for FISH analysis. FISH-IPA data proved previous FC data: not every clonal/blast cell is converted to DC(leu) (resulting in various proportions of DC(leu)) and not every detectable DC is of clonal/leukemic origin. Preselection of the best of four DC methods for "best" DC/DC(leu) generation is necessary. DC(leu) proportions correlate with the antileukemic functionality of DC/DC(leu)-stimulated T-cells, thereby proving the necessity of studying the quality of DC/DC(leu) after culture. FC is the superior method to quantify DC/DC(leu), since a blast phenotype is available in every given patient, even with low/no proportions of clonal aberrations, and can easily be used to study cellular compositions after DC culture.

Photodynamic therapy-mediated DC immunotherapy is highly effective for the inhibition of established solid tumors

Dendritic cell (DC)-mediated immunotherapy has not been as effective as expected for most solid tumors. This study demonstrates immune responses against solid tumors mediated by DCs charged with photodynamic therapy (PDT)-induced tumor lysates, which contain the heat shock protein (HSP) 70. PDT tumor lysate-pulsed DC (PDT-DC) inhibited the growth of mammary EMT6 tumors to a greater extent than freeze/thawed tumor lysate-pulsed DC (FT-DC) or PDT tumor lysates. PDT-DC also showed significant anti-tumor effects against fully-established (i.e., late-stage) solid tumors. Taken together, these results suggest that PDT-DC vaccination is more effective than conventional DC therapy for the treatment of cancers.

Activation of a glioma-specific immune response by oncolytic parvovirus Minute Virus of Mice infection

Rodent autonomous parvoviruses (PVs) are endowed with oncotropic properties and represent virotherapeutics with inherent oncolytic features. This work aimed to evaluate the capacity of Minute Virus of Mice (MVMp) to act as an adjuvant stimulating a mouse glioblastoma-specific immune response. MVMp was shown to induce cell death through apoptosis in glioma GL261 cells. Antigen-presenting cells (APCs) provide the initial cue for innate and adaptive immune responses, and thus MVMp-infected GL261 cells were tested for their ability to activate dendritic cells (DCs) and microglia (MG), two distinct cell types that are able to act as APCs. MG and discrete DC subsets were activated after co-culture with MVMp-infected glioma GL261 cells, as evidenced by upregulation of specific activation markers (CD80, CD86) and release of proinflammatory cytokines (tumor necrosis factor-α and interleukin-6). The in vivo analysis of immunodeficient and immunocompetent mice revealed a clear difference in their susceptibility to MVMp-mediated tumor suppression. Immunocompetent mice were fully protected from tumor outgrowth of GL261 cells infected ex vivo with MVMp. In contrast, immunodeficient animals were less competent for MVMp-dependent tumor inhibition, with only 20% of the recipients being protected, arguing for an additional immune component to allow full tumor suppression. In keeping with this conclusion, immunocompetent mice engrafted with MVMp-infected glioma cells developed a level of anti-tumor immunity with isolated splenocytes producing elevated levels of interferon-γ. In rechallenge experiments using uninfected GL261 cells, we could show complete protection against the tumor, arguing for the induction of a T-cell-mediated, tumor-specific, long-term memory response. These findings indicate that the anticancer effect of PVs can be traced back not only for their direct oncolytic effect, but also to their ability to break tumor tolerance.

In vitro-induced response patterns of antileukemic T cells: characterization by spectratyping and immunophenotyping

Myeloid leukemic cells can be induced to differentiate into leukemia-derived dendritic cells (DCleu) regaining the stimulatory capacity of professional DCs while presenting the leukemic antigen repertoire. But so far, the induced antileukemic T-cell responses are variable both in specificity and in efficacy. In an attempt to elucidate the underlying causes of different T-cell response patterns, T-cell receptor (TR) Vβ chain rearrangements were correlated with the T cells corresponding immunophenotypic profile, as well as their proliferative response and cytolytic capacities. In three different settings, donor T cells, either human leukocyte antigen matched or mismatched (haploidentical), or autologous T cells were repeatedly stimulated with myeloid blasts or leukemia-derived DC/DCleus from the corresponding patients diseased from acute myeloid leukemia (AML). Although no significant differences in T-cell proliferation were observed, the T-cell-mediated cytolytic response pattern varied considerably and even caused blast proliferation in two cases. Spectratyping revealed a remarkable restriction (>75% of normal level) of the CD4+ or CD8+-TR repertoire of blast- or DC/DCleu-stimulated T cells. Although in absolute terms, DC/DCleu stimulation induced the highest grade of restriction in the CD8+ T-cell subset, the CD4+ T-cell compartment seemed to be relatively more affected. But most importantly, in vitro stimulation with DC/DCleu resulted into an identical TR restriction pattern (β chain) that could be identified in vivo in a patient sample 3 months after allo-SCT. Thus, in vitro tests combining functional flow cytometry with spectratyping might provide predictive information about T cellular response patterns in vivo.

Spontaneous rejection of intradermally transplanted non-engineered tumor cells by neutrophils and macrophages from syngeneic strains of mice

It is not surprising that tumors arising spontaneously are rarely rejected by T cells, because in general they lack molecules to elicit a primary T-cell response. In fact, cytokine-engineered tumors can induce granulocyte infiltration leading to tumor rejection. In the present study, we i.d. injected seven kinds of non-engineered tumor cells into syngeneic strains of mice. Three of them (i.e. B16, KLN205, and 3LL cells) continued to grow, whereas four of them (i.e. Meth A, I-10, CL-S1, and FM3A cells) were spontaneously rejected after transient growth or without growth. In contrast to the i.d. injection of B16 cells into C57BL/6 mice, which induces infiltration of TAMs into the tumors, the i.d. injection of Meth A cells into BALB/c mice induced the invasion of cytotoxic inflammatory cells, but not of TAMs, into or around the tumors leading to an IFN-γ-dependent rejection. On day 5, the cytotoxic activity against the tumor cells reached a peak; and the effector cells were found to be neutrophils and macrophages. The i.d. Meth A or I-10 cell-immunized, but not non-immunized, mice rejected i.p.- or i.m.-transplanted Meth A or I-10 cells without growth, respectively. The main effector cells were CTLs; and there was no cross-sensitization between these two kinds of tumor cells, suggesting specific rejection of tumor cells by CTLs from i.d. immunized mice. These results indicate that infiltration of cytotoxic myeloid cells (i.e. neutrophils and macrophages, but not TAMs) into or around tumors is essential for their IFN-γ-dependent spontaneous rejection.

Decisions about dendritic cells: past, present, and future

A properly functioning adaptive immune system signifies the best features of life. It is diverse beyond compare, tolerant without fail, and capable of behaving appropriately with a myriad of infections and other challenges. Dendritic cells are required to explain how this remarkable system is energized and directed. I frame this article in terms of the major decisions that my colleagues and I have made in dendritic cell science and some of the guiding themes at the time the decisions were made. As a result of progress worldwide, there is now evidence of a central role for dendritic cells in initiating antigen-specific immunity and tolerance. The in vivo distribution and development of a previously unrecognized white cell lineage is better understood, as is the importance of dendritic cell maturation to link innate and adaptive immunity in response to many stimuli. Our current focus is on antigen uptake receptors on dendritic cells. These receptors enable experiments involving selective targeting of antigens in situ and new approaches to vaccine design in preclinical and clinical systems.

Combination therapy of renal cell carcinoma or breast cancer patients with dendritic cell vaccine and IL-2: results from a phase I/II trial

Background

Ten cancer patients (Six renal cell carcinoma and four breast cancer patients) were treated in a phase I/II study with a vaccine composed of autologous dendritic cells (DCs) and IL-2 to evaluate the DC vaccine-related toxicity and antigen-specific immune alteration.

Methods

Cancer patients were treated twice with autologous CD34⁺ hematopoietic stem cell-derived, GM-CSF/IFN-γ-differentiated DCs pulsed with autologous tumor lysate and KLH, by 4-week interval. Following each subcutaneous injection of therapeutic DCs, low-dose (200 MIU) IL-2 was introduced for 14 consecutive days as an immune adjuvant. To determine the DC vaccine-induced immunological alterations, the KLH-specific lymphocyte proliferation, number of IFN-γ secreting T cells (ELISPOT assay), NK activity and the cytokine modulation were measured.

Results

Cultured-DCs expressing HLA-DR, CD11c, CD83, and B7.1/B7.2 produced IL-12p70. After vaccination, the patients tolerated it. Clinical response was observed in one RCC patient as stable disease. However DC-vaccine related antigen-specific immune responses including peripheral blood lymphocyte proliferation and the number of IFN-r secreting cells were induced in six patients without clear correlation with clinical responses. Also NK activity was induced significantly in six patients after vaccination. DC vaccine-related decrease of TGF-β level or increase of IL-12p70 level and decline of CD4⁺CD25⁺ T cells were observed in three patients. However only in the RCC patient whose disease stabilized, combination of stimulatory as well as inhibitory immune alterations including induction of IFN-γ secreting T cell with reduction of CD4⁺ CD25⁺ T cell were correlated with clinical responses.

Conclusion

Data indicated that DC vaccine combined with IL-2 is well tolerated without major side effects. DC vaccine induced the specific immunity against introduced antigen. Combinatorial alterations of immunological parameters indicating antigen-specific immune induction along with reduction of inhibitory immunity were correlated with clinical responses in DC vaccine treated patients.

Cancer nanotheranostics: improving imaging and therapy by targeted delivery across biological barriers

Cancer nanotheranostics aims to combine imaging and therapy of cancer through use of nanotechnology. The ability to engineer nanomaterials to interact with cancer cells at the molecular level can significantly improve the effectiveness and specificity of therapy to cancers that are currently difficult to treat. In particular, metastatic cancers, drug-resistant cancers, and cancer stem cells impose the greatest therapeutic challenge for targeted therapy. Targeted therapy can be achieved with appropriately designed drug delivery vehicles such as nanoparticles, adult stem cells, or T cells in immunotherapy. In this article, we first review the different types of nanotheranostic particles and their use in imaging, followed by the biological barriers they must bypass to reach the target cancer cells, including the blood, liver, kidneys, spleen, and particularly the blood-brain barrier. We then review how nanotheranostics can be used to improve targeted delivery and treatment of cancer cells. Finally, we discuss development of nanoparticles to overcome current limitations in cancer therapy.

Tolerogenic dendritic cells and rheumatoid arthritis: current status and perspectives

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by the influxation of synovia and synovial compartments with immune cells including dendritic cells (DCs). DCs that induce autoimmune tolerance are called tolerogenic DCs (tolDCs). As a promising immunotherapeutic strategy for RA, tolDCs have received increasing attention. In this review, we first introduce the significant role of tolDCs in autoimmune regulation and then describe the manipulation strategies to generate tolDCs; next, we summarize recent progress in the experimental application of tolDCs for RA therapy, and finally we discuss the perspectives of tolerogenic vaccination for the treatment for RA in clinic.

Antigen-presenting cell (APC) subsets in ovarian cancer

The major human antigen-presenting cells (APCs) include monocytes/macrophages, myeloid dendritic cells (mDC), plasmacytoid dendritic cells (pDC), and B cells. These APC subsets have been observed in ovarian tumor environments. Their phenotypes and functionalities are subjected to alteration by multiple factors in the tumor environment. In this review, we summarize the nature, cellular interactions, and prognostic significance of the main APC populations in ovarian cancer, and discuss the relevance of manipulating APC subsets for patient treatment.

Dendritic Cells (DC) Facilitate Detachment of Squamous Carcinoma Cells (SCC), While SCC Promote an Immature CD16(+) DC Phenotype and Control DC Migration

In the inflammatory mucosal microenvironment of head and neck SCC (HNSCC), DC express CD16 and are usually in direct contact with tumor cells. Mucosal and inflammation-associated DC develop from monocytes, and monocyte-derived DC are used in HNSCC immunotherapy. However, beyond apoptotic tumor cell uptake and presentation of tumor antigens by DC, HNSCC cell interactions with DC are poorly understood. Using co-cultures of monocyte-derived DC and two established HNSCC cell lines that represent well- and poorly-differentiated SCC, respectively, we found that carcinoma cells induced significant increases in CD16 expression on DC while promoting a CD1a(+)CD86(dim) immature phenotype, similar to that observed in HNSCC specimens. Moreover, HNSCC cells affected steady-state and CCL21-induced migration of DC, and these effects were donor-dependent. The CCL21-induced migration directly correlated with HNSCC-mediated effects on CCR7 and CD38 expression on DC-SIGN-high DC. The dominant pattern seen in six out of nine donors was the increase in steady-state and CCL21-induced DC migration in co-cultures with HNSCC, while the reverse pattern, i.e., decreased DC migration in co-cultures with SCC, was identified in two donors. A split in migratory DC behavior, i.e. increase with one HNSCC cell line and a decrease with the second cell line, was observed in one donor. Remarkably, the numbers of live detached HNSCC cells were orders of magnitude higher in DC-HNSCC co-cultures than in parallel HNSCC cell cultures without DC. This study provides novel insights into the effects of DC-HNSCC interactions relevant to the tumor microenvironment.

Comparative study of clinical grade human tolerogenic dendritic cells

BACKGROUND

The use of tolerogenic DCs is a promising therapeutic strategy for transplantation and autoimmune disorders. Immunomodulatory DCs are primarily generated from monocytes (MDDCs) for in vitro experiments following protocols that fail to fulfil the strict regulatory rules of clinically applicable products. Here, we compared the efficacy of three different tolerance-inducing agents, dexamethasone, rapamycin and vitamin D3, on DC biology using GMP (Good Manufacturing Practice) or clinical grade reagents with the aim of defining their use for human cell therapy.

METHODS

Tolerogenic MDDCs were generated by adding tolerogenic agents prior to the induction of maturation using TNF-α, IL-β and PGE2. We evaluated the effects of each agent on viability, efficiency of differentiation, phenotype, cytokine secretion and stability, the stimulatory capacity of tol-DCs and the T-cell profiles induced.

RESULTS

Differences relevant to therapeutic applicability were observed with the cellular products that were obtained. VitD3-induced tol-DCs exhibited a slightly reduced viability and yield compared to Dexa-and Rapa-tol-DCs. Phenotypically, while Dexa-and VitD3-tol-DCs were similar to immature DCs, Rapa-tol-DCs were not distinguishable from mature DCs. In addition, only Dexa-and moderately VitD3-tol-DCs exhibited IL-10 production. Interestingly, in all cases, the cytokine secretion profiles of tol-DCs were not modified by a subsequent TLR stimulation with LPS, indicating that all products had stable phenotypes. Functionally, clearly reduced alloantigen T cell proliferation was induced by tol-DCs obtained using any of these agent. Also, total interferon-gamma (IFN-γ) secretion by T cells stimulated with allogeneic tol-DCs was reduced in all three cases, but only T cells co-cultured with Rapa-tol-DCs showed impaired intracellular IFN-γ production. In addition, Rapa-DCs promoted CD4+ CD127 low/negative CD25high and Foxp3+ T cells.

CONCLUSIONS

Our results demonstrate contrasting influences of different clinical-grade pharmacological agents on human tol-DC generation. This should be taken into account for decisions on the use of a specific agent for the appropriate cellular therapy in the context of a particular disease.

Generation and characterisation of therapeutic tolerogenic dendritic cells for rheumatoid arthritis

OBJECTIVES

Tolerogenic dendritic cells (tolDCs) constitute a promising experimental treatment for targeting autoreactive T cells in autoimmune diseases, including rheumatoid arthritis (RA). The authors' goal is to bring tolDC therapy for RA to the clinic. Here the authors address key translational issues related to the manufacturing of tolDCs from RA patients with current good manufacturing practice (cGMP)-compliant reagents, the stability of tolDCs, and the selection of suitable quality control markers.

METHODS

Human monocyte-derived tolDCs were established from RA patients and healthy controls (HCs) using the immunosuppressive drugs dexamethasone and vitamin D₃, and the cGMP-grade immunomodulator, monophosphoryl lipid A, in the cGMP-compliant medium, CellGroDC. The functionality of tolDCs and tolDC-modulated autologous CD4 T cells was determined by flow cytometry, [³H]thymidine incorporation and ELISA.

RESULTS

Clinical-grade tolDCs established from patients with RA exhibit a typical tolerogenic phenotype of reduced costimulatory molecules, low production of proinflammatory cytokines and impaired stimulation of autologous antigen-specific T cells, comparable to HC tolDCs. Toll-like receptor 2 (TLR-2) was highly expressed by tolDCs but not mature DCs. Furthermore, tolDCs suppressed mature DC-induced T cell proliferation, interferon γ and interleukin 17 production, and rendered T cells hyporesponsive to further stimulation. Importantly, tolDCs were phenotypically stable in the absence of immunosuppressive drugs and were refractory to further challenge with proinflammatory mediators.

CONCLUSIONS

tolDCs established from patients with RA are comparable to those derived from healthy donors. TLR-2 was identified as an ideal marker for quality control of tolDCs. Potently tolerogenic and highly stable, these tolDCs are a promising cellular therapeutic for tailored immunomodulation in the treatment of RA.

Signaling network of dendritic cells in response to pathogens: a community-input supported knowledgebase

Background

Dendritic cells are antigen-presenting cells that play an essential role in linking the innate and adaptive immune systems. Much research has focused on the signaling pathways triggered upon infection of dendritic cells by various pathogens. The high level of activity in the field makes it desirable to have a pathway-based resource to access the information in the literature. Current pathway diagrams lack either comprehensiveness, or an open-access editorial interface. Hence, there is a need for a dependable, expertly curated knowledgebase that integrates this information into a map of signaling networks.

Description

We have built a detailed diagram of the dendritic cell signaling network, with the goal of providing researchers with a valuable resource and a facile method for community input. Network construction has relied on comprehensive review of the literature and regular updates. The diagram includes detailed depictions of pathways activated downstream of different pathogen recognition receptors such as Toll-like receptors, retinoic acid-inducible gene-I-like receptors, C-type lectin receptors and nucleotide-binding oligomerization domain-like receptors. Initially assembled using CellDesigner software, it provides an annotated graphical representation of interactions stored in Systems Biology Mark-up Language. The network, which comprises 249 nodes and 213 edges, has been web-published through the Biological Pathway Publisher software suite. Nodes are annotated with PubMed references and gene-related information, and linked to a public wiki, providing a discussion forum for updates and corrections. To gain more insight into regulatory patterns of dendritic cell signaling, we analyzed the network using graph-theory methods: bifan, feedforward and multi-input convergence motifs were enriched. This emphasis on activating control mechanisms is consonant with a network that subserves persistent and coordinated responses to pathogen detection.

Conclusions

This map represents a navigable aid for presenting a consensus view of the current knowledge on dendritic cell signaling that can be continuously improved through contributions of research community experts. Because the map is available in a machine readable format, it can be edited and may assist researchers in data analysis. Furthermore, the availability of a comprehensive knowledgebase might help further research in this area such as vaccine development. The dendritic cell signaling knowledgebase is accessible at http://tsb.mssm.edu/pathwayPublisher/DC_pathway/DC_pathway_index.html.

Crosstalk between PKA and Epac regulates the phenotypic maturation and function of human dendritic cells

The cAMP-dependent signaling pathways that orchestrate dendritic cell (DC) maturation remain to be defined in detail. Although cAMP was previously thought to signal exclusively through protein kinase A (PKA), it is now clear that cAMP also activates exchange protein activated by cAMP (Epac), a second major cAMP effector. Whether cAMP signaling via PKA is sufficient to drive DC maturation or whether Epac plays a role has not been examined. In this study, we used cAMP analogs to selectively activate PKA or Epac in human monocyte-derived DCs and examined the effect of these signaling pathways on several hallmarks of DC maturation. We show that PKA activation induces DC maturation as evidenced by the increased cell-surface expression of MHC class II, costimulatory molecules, and the maturation marker CD83. PKA activation also reduces DC endocytosis and stimulates chemotaxis to the lymph node-associated chemokines CXCL12 and CCL21. Although PKA signaling largely suppresses cytokine production, the net effect of PKA activation translates to enhanced DC activation of allogeneic T cells. In contrast to the stimulatory effects of PKA, Epac signaling has no effect on DC maturation or function. Rather, Epac suppresses the effects of PKA when both pathways are activated simultaneously. These data reveal a previously unrecognized crosstalk between the PKA and Epac signaling pathways in DCs and raise the possibility that therapeutics targeting PKA may generate immunogenic DCs, whereas those that activate Epac may produce tolerogenic DCs capable of attenuating allergic or autoimmune disease.

Synthesis of pyridyl disulfide-functionalized nanoparticles for conjugating thiol-containing small molecules, peptides, and proteins

Previously we reported emulsion polymerization of propylene sulfide with Pluronic F127 as an emulsifier, yielding nanoparticles (NPs) in the 25 nm size range. Immunologically functional NPs were prepared by adding an antigen-Pluronic conjugate to the polymerization mixture ( Reddy , S. T. , et al. ( 2007 ) Nat. Biotechnol. 25, 1159 ). We sought a more flexible scheme for conjugation of antigens and other biomolecules to the NP surfaces that would allow for milder reaction conditions than achievable during the polymerization step. Here, we present the synthesis of such functionalizable NPs in the form of NPs that carry thiol-reactive groups, to which thiol-containing antigens (peptide or protein) or other biomolecules can be conjugated under mild conditions to yield immunofunctional NPs. The Pluronic-stabilized poly(propylene sulfide) (PPS) NPs with thiol-reactive pyridyl disulfide groups are prepared in two steps by (1) emulsion polymerization of propylene sulfide in the presence of a carboxylate-Pluronic and (2) reaction of the carboxylic acid groups on the NP surface with cysteamine pyridyl disulfide and a water-soluble carbodiimide reagent. We choose pyridyl disulfide groups to have a reduction-sensitive disulfide bond linking the antigen to the NP surface, allowing efficient release of antigen inside the cell in response to the reductive conditions within the endosome. The functionalizable NPs are characterized by proton NMR, dynamic light scattering (DLS), UV/vis spectroscopy, and transmission electron microscopy (TEM). Conjugation of small molecules and protein to the NP surface is presented.

Quality of T-cells after stimulation with leukemia-derived dendritic cells (DC) from patients with acute myeloid leukemia (AML) or myeloid dysplastic syndrome (MDS) is predictive for their leukemia cytotoxic potential

Myeloid leukemic cells can differentiate into leukemia-derived dendritic cells (DC(leu)), presenting known/unknown leukemic-antigens. Induced anti-leukemic T-cell-responses are variable. To further elicit DC/DC(leu)-induced T-cell-response-patterns we performed (functional)flow-cytometry/fluorolysis-assays before/after mixed lymphocyte cultures (MLC) of matched (allogeneic) donor-T-cells (n=6), T-cells prepared at relapse after stem cell transplantation (n=4) or (autologous) patients'-T-cells (n=7) with blast-containing-mononuclear-cells ('MNC') or DC(leu)-containing DC ('DC'). Compared to 'MNC' 'DC' were better mediators of anti-leukaemic T-cell-activity, although not in every case effective. We could define cut-off proportions of mature DC, DC(leu), proliferating, CD4(+), CD8(+) and non-naive T-cells after 'MNC'- or 'DC'-stimulation, that were predictive for an anti-leukemic-activity of stimulated T-cells as well as a response to immunotherapy. Interestingly especially ratios >1 of CD4:CD8 or CD45RO:CD45RA T-cells were predictive for anti-leukemic function after DC-stimulation. In summary the composition and quality of DC and T-cells after a MLC-stimulating-phase is predictive for a successful ex-vivo and in-vivo anti-leukemic response, especially with respect to proportions of proliferating, CD4(+) and CD45RO(+) T-cells. Successful cytotoxicity and the development of a T-cell-memory after 'DC'-stimulation could be predictive for the clinical course of the disease and may pave the way to develop adoptive immunotherapy, especially for patients at relapse after SCT.

Immunotherapy of cancer with dendritic cells loaded with tumor antigens and activated through mRNA electroporation

Since decades, the main goal of tumor immunologists has been to increase the capacity of the immune system to mediate tumor regression. Considerable progress has been made in enhancing the efficacy of therapeutic anticancer vaccines. First, dendritic cells (DCs) have been identified as the key players in orchestrating primary immune responses. A better understanding of their biology and the development of procedures to generate vast amounts of DCs in vitro have accelerated the development of potent immunotherapeutic strategies for cancer. Second, tumor-associated antigens have been identified which are either selectively or preferentially expressed by tumor cells and can be recognized by the immune system. Finally, several studies have been performed on the genetic modification of DCs with tumor antigens. In this regard, loading the DCs with mRNA, which enables them to produce/process and present the tumor antigens themselves, has emerged as a promising strategy. Here, we will first overview the different aspects that must be taken into account when generating an mRNA-based DC vaccine and the published clinical studies exploiting mRNA-loaded DCs. Second, we will give a detailed description of a novel procedure to generate a vaccine consisting of tumor antigen-expressing dendritic cells with an in vitro superior capacity to induce anti-tumor immune responses. Here, immature DCs are electroporated with mRNAs encoding a tumor antigen, CD40 ligand (CD40L), CD70, and constitutively active (caTLR4) to generate mature antigen-presenting DCs.

Dendritic cell immunotherapy for HIV infection: from theory to reality

Knowledge concerning the immunology of dendritic cells (DCs) accumulated over the last few decades and the development of methodologies to generate and manipulate these cells in vitro has made their therapeutic application a reality. Currently, clinical protocols for DC-based therapeutic vaccine in HIV-infected individuals show that it is a safe and promising approach. Concomitantly, important advances continue to be made in the development of methodologies to optimize DC acquisition, as well as the selection of safe, immunogenic HIV antigens and the evaluation of immune response in treated individuals.

Recent advances in multivalent self adjuvanting glycolipopeptide vaccine strategies against breast cancer

Breast cancer (BrCa) is the second leading cause of cancer-related deaths for women worldwide. Evidence from both patients and mouse cancer models suggests that the simultaneous induction of BrCa-specific CD4(+) T cells, CD8(+) cytotoxic T cells, and antibodies is crucial for providing immune resistance. However, almost all current vaccines address only a single arm of the immune system, which may explain their lack of efficacy. We believe that the correct response to monovalent vaccines' "failure" is to increase our knowledge about antitumor protective immunity and to develop a multivalent vaccine molecule that can simultaneously induce multiple arms of the immune system. We highlight here recent advances in anti-BrCa peptide-based vaccine strategies with an emphasis on the self adjuvanting multivalent glycolipopeptide vaccine strategy recently developed in our laboratory and which showed promising results in both immunotherapeutic and immunoprophylactic settings.

Mutual helper effect in copulsing of dendritic cells with 2 antigens: a novel approach for improvement of dendritic-based vaccine efficacy against tumors and infectious diseases simultaneously

To develop an efficient dendritic cell (DC)-based immunotherapy protocol, we examined whether simultaneous pulsing of DCs with a given antigen and a third-party antigen could enhance their antigen presentation capacity. Purified splenic DCs of Balb/c mice were pulsed separately with immunoglobulin G, ovalbumin, conalbumin, P15 peptide of Mycobacterium tuberculosis, and prostate-specific antigen or double combinations of the aforementioned antigens. In some settings, DCs pulsed with 1 antigen were mixed equally with those pulsed with another antigen. Antigen-pulsed DCs were injected into the footpad of syngeneic mice and proliferation of whole, CD4 and CD8 depleted lymph node cells was measured after restimulation with cognate antigen. Antigen-specific production of interferon-gamma (IFNgamma) was tested in culture supernatants. Frequency of responding lymph node cells was determined by IFNgamma enzyme-linked immunosorbent spot assay. Our results showed that copulsing of DCs with 2 unrelated antigens increased the capacity of DCs to induce antigen-specific T-cell proliferation against both antigens up to 16-fold. Injection of 2 populations of DCs each pulsed with a different antigen, increased proliferation of primed T cells significantly as well. Both CD4 and CD8 depleted populations showed vigorous proliferative response in copulsing system. In addition, copulsing of DCs with 2 antigens resulted in higher frequency of antigen-specific responding cells and significantly more IFNgamma production. Our results clearly showed that unrelated peptides and proteins could be used to enhance efficacy of DC-based vaccines and in this system, each antigen served to help the other one, a condition that we termed as "mutual helper effect."

Myeloid dendritic cells from human cutaneous squamous cell carcinoma are poor stimulators of T-cell proliferation

To determine the phenotype and function of myeloid dendritic cells (DCs) from human cutaneous squamous-cell carcinoma (SCC), we studied their surface marker expression and allo-stimulatory potential ex vivo. There were abundant CD11c(+) myeloid DCs, as well as TNF and inducible nitric oxide synthase (iNOS)-producing DCs, in and around SCC tumor nests. Although myeloid DCs from SCC, adjacent non-tumor-bearing skin, and normal skin, were phenotypically similar by flow cytometry, and there was a pronounced genomic signature of mature DCs in SCC, they showed different T-cell stimulatory potential in an allogeneic mixed leukocyte reaction. Myeloid DCs from SCC were less potent stimulators of allogeneic T-cell proliferation than DCs from non-tumor-bearing skin. Culture with a DC-maturing cytokine cocktail (IL-1beta, IL-6, TNF-alpha, and PGE(2)) enhanced stimulatory potential in DCs from non-tumor-bearing skin, whereas SCC-associated DCs remained poor stimulators of T-cell proliferation. The microenvironment associated with SCC showed expression of TGF-beta, IL-10, and VEGF-A, factors capable of suppressing the DC function. These findings indicate that CD11c(+)/HLA-DR(hi) DCs from SCC are mature, but are not potent stimulators of T-cell proliferation compared with phenotypically similar DCs isolated from non-tumor-bearing skin. Identification of mechanisms responsible for suppression of tumor-associated DCs may provide insight into the evasion of immunosurveillance by SCC.

In vitro use of autologous dendritic cells improves detection of T cell responses to hepatitis B virus (HBV) antigens

T lymphocyte responses to hepatitis B virus (HBV) core antigen (HBcAg) are vigorous and easily detectable in vitro during recovery from acute hepatitis B but significantly weaker in patients with chronic HBV infection. In contrast, T cell responses to hepatitis B surface antigen (HBsAg) are almost undetectable during infection and even in a substantial fraction of subjects receiving vaccination with HBsAg. The aim of this study was to investigate whether the use of dendritic cells (DCs) in an in vitro assay could increase the detection of HBV-specific T cells in these conditions. Autologous monocyte-derived DCs, compared to direct HBsAg addition to the cultures, increased the stimulation of HBs- specific T cells. These were detected in 73% of healthy subjects who had recently received hepatitis B vaccine and in 43% of patients recovering from acute hepatitis B. Likewise, proliferation in response to DC-presented HBcAg was detected in both CD4(+) and CD8(+) T cells from the majority of chronic hepatitis B patients. A longitudinal evaluation of HBc-specific T cell responses during and after a 1-year treatment with pegylated interferon (IFN)-alpha showed that HBc-specific CD4(+) T cell responses had no correlation with sustained virus suppression whereas CD8(+) T cell responses were more frequently detected in patients able to control HBV replication after therapy interruption. The use of autologous DCs as antigen-presenting cells appears applicable to clinically relevant in vitro evaluation of T cell responses, particularly in those conditions characterized by low frequency of circulating antigen-specific cells and suboptimal in vivo activation.