Bone marrow-derived dendritic cells serve as potent adjuvants for peptide-based antitumor vaccines

Dendritic Cells and Myeloid Derived Suppressor Cells Fully Responsive to Stimulation via Toll-Like Receptor 4 Are Rapidly Induced from Bone-Marrow Cells by Granulocyte-Macrophage Colony-Stimulating Factor

Dendritic cells (DCs) are commonly generated from bone marrow (BM) progenitor cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) alone or in combination with interleukin 4 (IL-4). These cells are often harvested post day 5, when they acquire maturation markers and can stimulate T cells. Apart from DCs, myeloid derived suppressor cells (MDSCs) are also found within these cultures. However, little is known about the functional characteristics of DCs and MDSCs before day 5. Herein, using a murine model, it is shown that early DCs and MDSCs, even in cultures with GM-CSF alone, upregulate fully maturation and activation surface molecules in response to the toll-like receptor 4 (TLR4) ligand lipopolysaccharide (LPS) stimulation. Despite initially displaying lower marker expression levels, these cells efficiently induced T cell stimulation and cytokine production. Interestingly, Gr-1^int MDSCs increased their T cell co-stimulatory activity upon TLR4 stimulation. Additionally, early DCs and MDSCs exhibited differential endocytic capacity for viral sized nanoparticles and bacterial sized microparticles. DCs internalized both particle sizes, whilst MDSCs only internalized the larger microparticles, with reduced endocytic activity over time in the culture. These findings have unveiled an important role for the rapid initiation of productive immunity by GM-CSF, with promising implications for future vaccine and DC immunotherapy developments.

Trial watch: dendritic cell vaccination for cancer immunotherapy

Dendritic- cells (DCs) have received considerable attention as potential targets for the development of anticancer vaccines. DC-based anticancer vaccination relies on patient-derived DCs pulsed with a source of tumor-associated antigens (TAAs) in the context of standardized maturation-cocktails, followed by their reinfusion. Extensive evidence has confirmed that DC-based vaccines can generate TAA-specific, cytotoxic T cells. Nonetheless, clinical efficacy of DC-based vaccines remains suboptimal, reflecting the widespread immunosuppression within tumors. Thus, clinical interest is being refocused on DC-based vaccines as combinatorial partners for T cell-targeting immunotherapies. Here, we summarize the most recent preclinical/clinical development of anticancer DC vaccination and discuss future perspectives for DC-based vaccines in immuno-oncology.

Antigen cross-presentation and T-cell cross-priming in cancer immunology and immunotherapy

Dendritic cells (DCs) are the main professional antigen-presenting cells for induction of T-cell adaptive responses. Cancer cells express tumor antigens, including neoantigens generated by nonsynonymous mutations, but are poor for antigen presentation and for providing costimulatory signals for T-cell priming. Mounting evidence suggests that antigen transfer to DCs and their surrogate presentation on major histocompatibility complex class I and II molecules together with costimulatory signals is paramount for induction of viral and cancer immunity. Of the great diversity of DCs, BATF3/IRF8-dependent conventional DCs type 1 (cDC1) excel at cross-presentation of tumor cell-associated antigens. Location of cDC1s in the tumor correlates with improved infiltration by CD8+ T cells and tumor-specific T-cell immunity. Indeed, cDC1s are crucial for antitumor efficacy using checkpoint inhibitors and anti-CD137 agonist monoclonal antibodies in mouse models. Enhancement and exploitation of T-cell cross-priming by cDC1s offer opportunities for improved cancer immunotherapy, including in vivo targeting of tumor antigens to internalizing receptors on cDC1s and strategies to increase their numbers, activation and priming capacity within tumors and tumor-draining lymph nodes.

Results of a Pilot Trial of Immunotherapy with Dendritic Cells Pulsed with Autologous Tumor Lysates in Patients with Advanced Cancer

Aims and background

The purpose of the study was to test the immunological and clinical effects of infusions of dendritic cells pulsed with autologous tumor lysate in patients with advanced cancer.

Patients and methods

Peripheral blood mononuclear cells from 15 patients with metastatic cancer (melanoma in 10, lung cancer in 2, renal cell carcinoma in 1, sarcoma in 1, breast cancer in 1) were harvested by leukapheresis after mobilization with GM-CSF (5 μg/kg/day s.c. for 4 days). Mononuclear cells were separated and cultured in GM-CSF (1000 U/ml) and interleukin-4 (1000 U/ml) for 7 days. Phenotype was assessed by 2-color flow cytometry and immunocytochemistry. On day 6, dendritic cells were pulsed with 1 g of fresh autologous tumor lysate for 24 h and infused intravenously. Interleukin-2 (6 million IU), interferon a (4 million IU) and GM-CSF (400 μg) were injected s.c. daily for 10 days beginning on the day of dendritic cell infusion. Treatment was repeated every 21 days for 3 courses.

Results

The morphology, immunocytochemistry and phenotype of cultured cells was consistent with dendritic cells: intense positivity for HLA-DR and CD86, with negativity for markers of other lineages, including CD3, CD4, CD8 and CD14. More than 5 × 107 dendritic cells were injected in all patients. Nine patients developed >5 mm delayed type cutaneous hypersensitivity reactions to tumor lysate ± GM-CSF after the first immunization (larger than GM-CSF in all cases). Median delayed type cutaneous hypersensitivity to lysate + GM-CSF was 3 cm after the third immunization. One melanoma patient with skin, liver, lung and bone metastases had a partial response lasting 8 months (followed by progression in the brain). Seven patients had stable disease for >3 months, and 7 had progression.

Conclusions

Infusion of tumor lysate-pulsed dendritic cells induces a strong cell-mediated antitumor immune reaction in patients with advanced cancer and has some clinical activity.

Neoepitopes as cancer immunotherapy targets: key challenges and opportunities

Over the last half century, it has become well established that cancers can elicit a host immune response that can target them with high specificity. Only within the last decade, with the advances in high-throughput gene sequencing and bioinformatics approaches, are we now on the forefront of harnessing the host's immune system to treat cancer. Recently, some strides have been taken toward understanding effective tumor-specific MHC I restricted epitopes or neoepitopes. However, many fundamental questions still remain to be addressed before this therapy can live up to its full clinical potential. In this review, we discuss the major hurdles that lie ahead and the work being done to address them.

Trial watch: Dendritic cell-based anticancer immunotherapy

Dendritic cell (DC)-based vaccines against cancer have been extensively developed over the past two decades. Typically DC-based cancer immunotherapy entails loading patient-derived DCs with an appropriate source of tumor-associated antigens (TAAs) and efficient DC stimulation through a so-called "maturation cocktail" (typically a combination of pro-inflammatory cytokines and Toll-like receptor agonists), followed by DC reintroduction into patients. DC vaccines have been documented to (re)activate tumor-specific T cells in both preclinical and clinical settings. There is considerable clinical interest in combining DC-based anticancer vaccines with T cell-targeting immunotherapies. This reflects the established capacity of DC-based vaccines to generate a pool of TAA-specific effector T cells and facilitate their infiltration into the tumor bed. In this Trial Watch, we survey the latest trends in the preclinical and clinical development of DC-based anticancer therapeutics. We also highlight how the emergence of immune checkpoint blockers and adoptive T-cell transfer-based approaches has modified the clinical niche for DC-based vaccines within the wide cancer immunotherapy landscape.

Development of HPV Vaccines for HPV-associated Head and Neck Squamous Cell Carcinoma

High-risk genotypes of the human papillomavirus (HPV), particularly HPV type 16, are found in a distinct subset of head and neck squamous cell carcinomas (HNSCC). Thus, these HPV-associated HNSCC may be prevented or treated by vaccines designed to induce appropriate HPV virus-specific immune responses. Infection by HPV may be prevented by neutralizing antibodies specific for the viral capsid proteins. In clinical trials, vaccines comprised of HPV virus-like particles (VLPs) have shown great promise as prophylactic HPV vaccines. However, given that capsid proteins are not expressed at detectable levels by infected basal keratinocytes, vaccines with therapeutic potential must target other non-structural viral antigens. Two HPV oncogenic proteins, E6 and E7, are important in the induction and maintenance of cellular transformation and are co-expressed in the majority of HPV-containing carcinomas. Therefore, therapeutic vaccines targeting these proteins may have potential to control HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 is administered in live vectors, in peptides or protein, in nucleic acid form, as components of chimeric VLPs, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. Should they fulfill their promise, these vaccines may prevent HPV infection or control its potentially life-threatening consequences in humans.

Respiratory Syncytial Virus Aggravates Renal Injury through Cytokines and Direct Renal Injury

The purpose of this study was to investigate the relationship between renal injury and reinfection that is caused by respiratory syncytial virus (RSV) and to analyze the mechanism of renal injury. Rats were repeatedly infected with RSV on days 4, 8, 14, and 28, then sacrificed and examined on day 56 after the primary infection. Renal injury was examined by transmission electron microscopy and histopathology. The F protein of RSV was detected in the renal tissue by indirect immunofluorescence. Proteinuria and urinary glycosaminoglycans (GAGs), serum levels of albumin, urea nitrogen, and creatinine, secretion of cytokines, T lymphocyte population and subsets, and dendritic cell (DC) activation state were examined. The results showed that renal injury was more serious in the reinfection group than in the primary infection group. At a higher infection dose, 6 × 10⁶ PFU, the renal injury was more severe, accompanied by higher levels of proteinuria and urinary GAGs excretion, and lower levels of serum albumin. Podocyte foot effacement was more extensive, and hyperplasia of mesangial cells and proliferation of mesangial matrix were observed. The maturation state of DCs was specific, compared with the primary infection. There was also a decrease in the ratio of CD4⁺ to CD8⁺ T lymphocytes, due to an increase in the percentage of CD8⁺ T lymphocytes and a decrease in the percentage of CD4⁺ T lymphocytes, and a dramatic increase in the levels of IL-6 and IL-17. In terms of the different reinfection times, the day 14 reinfection group yielded the most serious renal injury and the most significant change in immune function. RSV F protein was still expressed in the glomeruli 56 days after RSV infection. Altogether, these results reveal that RSV infection could aggravate renal injury, which might be due to direct renal injury caused by RSV and the inflammatory lesions caused by the anti-virus response induced by RSV.

Update on Mucin-1 immunotherapy in cancer: a clinical perspective

INTRODUCTION

Mucin 1 (MUC1) is particularly well suited as a cancer immunotherapy target due to the elevated protein expression and aberrant forms associated with malignancy. A variety of therapeutic strategies have been explored, including antibodies intended to induce cancer cell destruction, and vaccinations with peptides, tumor extracts, and gene expression systems.

AREAS COVERED

MUC1 immunotherapeutic strategies have included vaccination with peptide sequences, glycan molecules, viruses, and dendritic cells, monoclonal antibodies and monoclonal antibody conjugates. Here we review the relevant clinical trials in each field of immunotherapy with particular focus on large and recently published trials.

EXPERT OPINION

Long clinical experience in the trial setting has reduced concerns of immunotherapy associated toxicities and inappropriate immune responses, with the main limitation (common to many experimental approaches) being a lack of clinical efficacy. However, there have been sufficient treatment-associated responses to justify continued pursuit of MUC1 targeted immunotherapies. The focus now should be on application to the relevant cancers under appropriate circumstances and combination with the emerging non-specific immunotherapy approaches such as the PD-1 pathway inhibitors.

Trial watch: Dendritic cell-based anticancer therapy

The use of patient-derived dendritic cells (DCs) as a means to elicit therapeutically relevant immune responses in cancer patients has been extensively investigated throughout the past decade. In this context, DCs are generally expanded, exposed to autologous tumor cell lysates or loaded with specific tumor-associated antigens (TAAs), and then reintroduced into patients, often in combination with one or more immunostimulatory agents. As an alternative, TAAs are targeted to DCs in vivo by means of monoclonal antibodies, carbohydrate moieties or viral vectors specific for DC receptors. All these approaches have been shown to (re)activate tumor-specific immune responses in mice, often mediating robust therapeutic effects. In 2010, the first DC-based preparation (sipuleucel-T, also known as Provenge®) has been approved by the US Food and Drug Administration (FDA) for use in humans. Reflecting the central position occupied by DCs in the regulation of immunological tolerance and adaptive immunity, the interest in harnessing them for the development of novel immunotherapeutic anticancer regimens remains high. Here, we summarize recent advances in the preclinical and clinical development of DC-based anticancer therapeutics.

Trial watch: Dendritic cell-based interventions for cancer therapy

Dendritic cells (DCs) occupy a central position in the immune system, orchestrating a wide repertoire of responses that span from the development of self-tolerance to the elicitation of potent cellular and humoral immunity. Accordingly, DCs are involved in the etiology of conditions as diverse as infectious diseases, allergic and autoimmune disorders, graft rejection and cancer. During the last decade, several methods have been developed to load DCs with tumor-associated antigens, ex vivo or in vivo, in the attempt to use them as therapeutic anticancer vaccines that would elicit clinically relevant immune responses. While this has not always been the case, several clinical studies have demonstrated that DC-based anticancer vaccines are capable of activating tumor-specific immune responses that increase overall survival, at least in a subset of patients. In 2010, this branch of clinical research has culminated with the approval by FDA of a DC-based therapeutic vaccine (sipuleucel-T, Provenge^®) for use in patients with asymptomatic or minimally symptomatic metastatic hormone-refractory prostate cancer. Intense research efforts are currently dedicated to the identification of the immunological features of patients that best respond to DC-based anticancer vaccines. This knowledge may indeed lead to personalized combination strategies that would extend the benefit of DC-based immunotherapy to a larger patient population. In addition, widespread enthusiasm has been generated by the results of the first clinical trials based on in vivo DC targeting, an approach that holds great promises for the future of DC-based immunotherapy. In this Trial Watch, we will summarize the results of recently completed clinical trials and discuss the progress of ongoing studies that have evaluated/are evaluating DC-based interventions for cancer therapy.

Mannan-modified adenovirus encoding VEGFR-2 as a vaccine to induce anti-tumor immunity

PURPOSE

Dendritic cell (DC) vaccines are a promising immunotherapeutic approach for treatment and prevention of cancer. While this methodology is widely accepted, it also has some limitations. Antigen-presenting cells including DCs express the mannan receptor (MR). The delivery of a mannan-modified tumor antigen to the MR has been demonstrated to be efficient. Vascular endothelial growth factor receptor-2 (VEGFR-2) is mainly responsible for angiogenesis and tumor growth. The goal of our study was to deliver VEGFR-2 to DCs by means of mannan-modified adenovirus.

METHODS

VEGFR-2 recombinant adenovirus modified with oxidized mannan was constructed as a tumor vaccine to immunize mice in vivo. IFN-γ in mouse sera and spleen was detected by ELISA and ELISPOT. The killing activity of cytotoxic T lymphocyte (CTL) against VEGFR-2 was measured with a lactate dehydrogenase assay. Vessel densities in tumor tissues were detected by immunohistochemistry. Flow cytometry was used to test CD4(+) and CD8(+) T-cell counts in tumor tissues.

RESULTS

The vaccine exhibited both protective and therapeutic efficacy in the inhibition of tumor growth and markedly prolonged survival in mice. Protection against metastasis was also observed. Furthermore, vaccination led to greater IFN-γ and VEGFR-2-specific CTLs. The specific immunity resulted in the suppression of angiogenesis and an increase in CD8(+) cells in tumor tissues.

CONCLUSION

Oxidized mannan-modified adenovirus expressing VEGFR-2 could extraordinarily stimulate both protective and therapeutic immune response in a mice model. Our data suggest that the combination of cancer immunity and anti-angiogenesis via modified mannan is a promising strategy in tumor prophylaxis and therapy.

Trial watch: Dendritic cell-based interventions for cancer therapy

Dendritic cells (DCs) occupy a privileged position at the interface between innate and adaptive immunity, orchestrating a large panel of responses to both physiological and pathological cues. In particular, whereas the presentation of antigens by immature DCs generally results in the development of immunological tolerance, mature DCs are capable of priming robust, and hence therapeutically relevant, adaptive immune responses. In line with this notion, functional defects in the DC compartment have been shown to etiologically contribute to pathological conditions including (but perhaps not limited to) infectious diseases, allergic and autoimmune disorders, graft rejection and cancer. Thus, the possibility of harnessing the elevated immunological potential of DCs for anticancer therapy has attracted considerable interest from both researchers and clinicians over the last decade. Alongside, several methods have been developed not only to isolate DCs from cancer patients, expand them, load them with tumor-associated antigens and hence generate highly immunogenic clinical grade infusion products, but also to directly target DCs in vivo. This intense experimental effort has culminated in 2010 with the approval by the US FDA of a DC-based preparation (sipuleucel-T, Provenge®) for the treatment of asymptomatic or minimally symptomatic metastatic castration-refractory prostate cancer. As an update to the latest Trial Watch dealing with this exciting field of research (October 2012), here we summarize recent advances in DC-based anticancer regimens, covering both high-impact studies that have been published during the last 13 mo and clinical trials that have been launched in the same period to assess the antineoplastic potential of this variant of cellular immunotherapy.

Dendritic cell therapy in advanced gastric cancer: a promising new hope?

Advanced gastric cancer carries a very poor prognosis when the tumor becomes unresectable. Even with the best currently available chemotherapy regimens the survival rate remains dismal. A recent breakthrough in the treatment paradigm has been the approval of trastuzumab, a monoclonal antibody, in HER2-positive metastatic gastric cancer. A large number of trials are underway using dendritic cells (DCs) in a number of human malignancies and do show a ray of hope in management of these patients. This review attempts to summarize tumor immunology and the current data regarding use of DCs in gastric cancer therapy.

Combined E7-dendritic cell-based immunotherapy and human sodium/iodide symporter radioiodine gene therapy with monitoring of antitumor effects by bioluminescent imaging in a mouse model of uterine cervical cancer

Using a uterine cervical cancer cell line expressing human papillomavirus (HPV) 16 E7 antigen and bioluminescent imaging (BLI), we evaluated the therapeutic potential of combined immunotherapy using transfected dendritic cells (DC-E7) and human sodium/iodide symporter (hNIS) radioiodine gene therapy in a xenograft animal cancer model. Dendritic cells expressing either E7 antigen (DC-E7) or no-insert (DC-no insert) were made for immunization materials, and murine uterine cervical cancer cell line coexpressing E7, firefly luciferase, hNIS, and EGFP genes (TC-1/FNG) were prepared for the animal tumor model. C57BL/6 mice were divided into five therapy groups (phosphate-buffered saline [PBS], DC-no insert, DC-E7, I-131, and DC-E7+I-131 groups). Single therapy with either DC-E7 or I-131 induced greater retardation in tumor growth compared with PBS or DC-no insert groups, and it resulted in some tumor-free mice (DC-E7 and I-131 groups, 40% and 20%, respectively). Combination therapy with DC-E7 and I-131 dramatically inhibited tumor growth, thus causing complete disappearance of tumors in all mice, and these effects were further confirmed by BLI in vivo. In conclusion, complete disappearance of the tumor was achieved with combined DC-E7 vaccination and hNIS radioiodine gene therapy in a mouse model with E7-expressing uterine cervical cancer, and serial BLIs successfully demonstrated antitumor effects in vivo.

MicroRNA-21 limits in vivo immune response-mediated activation of the IL-12/IFN-gamma pathway, Th1 polarization, and the severity of delayed-type hypersensitivity

An altered balance between Th1 and Th2 cytokines is responsible for a variety of immunoinflammatory disorders such as asthma, yet the role of posttranscriptional mechanisms, such as those mediated by microRNAs (miRs), in adjusting the relative magnitude and balance of Th cytokine expression have been largely unexplored. In this study, we show that miR-21 has a central role in setting a balance between Th1 and Th2 responses to Ags. Targeted ablation of miR-21 in mice led to reduced lung eosinophilia after allergen challenge, with a broadly reprogrammed immunoactivation transcriptome and significantly increased levels of the Th1 cytokine IFN-γ. Biological network-based transcriptome analysis of OVA-challenged miR-21(-/-) mice identified an unexpected prominent dysregulation of IL-12/IFN-γ pathways as the most significantly affected in the lungs, with a key role for miR-21 in IFN-γ signaling and T cell polarization, consistent with a functional miR-21 binding site in IL-12p35. In support of these hypotheses, miR-21 deficiency led dendritic cells to produce more IL-12 after LPS stimulation and OVA-challenged CD4(+) T lymphocytes to produce increased IFN-γ and decreased IL-4. Further, loss of miR-21 significantly enhanced the Th1-associated delayed-type hypersensitivity cutaneous responses. Thus, our results define miR-21 as a major regulator of Th1 versus Th2 responses, defining a new mechanism for regulating polarized immunoinflammatory responses.

Epinephrine-primed murine bone marrow-derived dendritic cells facilitate production of IL-17A and IL-4 but not IFN-γ by CD4+ T cells

Sympathetic activation leading to the release of epinephrine and norepinephrine, is known as an important regulatory circuit related to immune-mediated diseases. However, questions still remain on the behavior of antigen presenting cells (APC) dictated by stress-induced sympathetic neurotransmitters. The purpose of this study was to examine the fate of bone marrow-derived dendritic cell (BMDC)-associated influences on resting CD4(+) T cell activation. We hypothesize that pre-exposure of dendritic cells (DCs) can modify the intensity of cytokine production, leading to preference in resting CD4(+) T cell activation. BMDCs were pre-treated with epinephrine for 2h followed by subsequent treatment of lipopolysaccharide (LPS). Subsequently, BMDCs were cocultured with purified CD4(+) T cells from mouse spleen in the absence or presence of anti-CD3 stimulation in epinephrine-free media. Epinephrine pre-treatment enhanced surface expression of MHCII, CD80 and CD86. Quantitative RT-PCR showed that epinephrine pre-treatment induced a significant transcriptional decrease of IL-12p40 and a significant increase of IL-12p35 and IL-23p19. In addition, β2-adrenergic-blockade was shown to reverse these effects. Epinephrine pre-treatment also induced a significant decrease of IL-12p70 and a significant increase of IL-23 and IL-10 cytokine production. Importantly, these changes corresponded with increased IL-4 and IL-17A, but not IFN-g cytokine production by CD4(+) T cells in a b2-adrenergic receptor-dependent manner. These results suggest that exposure to stress-derived epinephrine dictates dendritic cells to generate a dominant Th2/Th17 phenotype in the context of subsequent exposure to a pathogenic stimulus.

Subsets, expansion and activation of myeloid-derived suppressor cells

Tumor cells and microorganisms manipulate the immune system to minimize any counter response in order to survive. Myeloid-derived suppressor cells (MDSC) in the mouse represent activated Gr-1(+) CD11b(+) myeloid precursor cells. Activation may occur through endogenous or exogenous factors leading to the suppression of immune responses. Under steady state conditions the same precursors differentiate into dendritic cells, macrophages and neutrophils. Their linkage to tumor progression and several suppression mechanisms employing the arginine metabolism are well documented, but knowledge of their role in chronic infections, autoimmune diseases and graft-versus-host reactions is just emerging. Several factors have been described to promote MDSC expansion and activation in bone marrow, spleen and tumor sites. New evidence suggests that the Gr-1 antibody itself may differentially trigger myelopoiesis under steady state conditions or induce apoptosis in inflammatory situations after binding to a common epitope expressed on Ly-6C and Ly-6G molecules, respectively. Moreover, two subsets of neutrophil- and monocyte-related MDSC have been described in tumor-bearing and healthy mice. In the present review, we summarize some early work leading to recent findings on these two MDSC subsets, the factors supporting MDSC expansion and activation, as well as novel insights on Gr-1 antibody functions.

Choosing and preparing antigen-presenting cells

The first issue in selecting a system for antigen-presentation experiments is to define the appropriate type of antigen-presenting cell (APC) to study. For some experiments, crude preparations such as splenocytes or peripheral blood mononuclear cells (PBMCs) may suffice to provide APC function for stimulating T cells. This unit develops approaches for preparation of more defined APC populations, including dendritic cells (DCs), macrophages, and B lymphocytes, the three types of "professional" APC. Each of these cell types exists in different stages of differentiation, maturation, and activation, or in some cases different lineages. For example, dendritic cells may be divided into subsets, including myeloid DCs (mDCs) and plasmacytoid DCs (pDCs). Each APC type has an important antigen-presentation function, although they contribute to different aspects of the immune response. Therefore, selection of an APC type for study must include consideration of the stage or aspect of immune response that is to be modeled in the experiment.

Effects of herpes simplex virus amplicon transduction on murine dendritic cells

The herpes simplex virus (HSV)-based amplicon is a versatile vaccine platform that has been preclinically vetted as a gene-based immunotherapeutic for cancer, HIV, and neurodegenerative disorders. Although it is well known that injection of dendritic cells (DCs) transduced ex vivo with helper virus-free HSV amplicon vectors expressing disease-relevant antigens induces antigen-specific immune responses, the cellular receptor(s) by which the amplicon virion gains entry into DCs, as well as the effects that viral vector transduction impinges on the physiological status of these cells, is less understood. Herein, we examine the effects of amplicon transduction on mouse bone marrow-derived DCs. We demonstrate that HSV-1 cellular receptors HveC and HveA are expressed on the cell surface of murine DCs, and that HSV amplicons transduce DCs at high efficiency (>90%) with minimal effects on cell viability. Transduction of dendritic cells with amplicons induces a transient DC maturation phenotype as represented by self-limited upregulation of MHCII and CD11c markers. Mature DCs are less sensitive to HSV amplicon transduction than immature DCs regarding DC-related surface marker maintenance. From this and our previous work, we conclude that HSV amplicons transduce DCs efficiently, but impart differential and transient physiological effects on mature and immature DC pools, which will facilitate fine-tuning of this vaccination platform and further exploit its potential in immunotherapy.

New insights into the regulation of T cells by gamma(c) family cytokines

Common cytokine receptor gamma-chain (gamma(c)) family cytokines have crucial roles in the development, proliferation, survival and differentiation of multiple cell lineages of both the innate and adaptive immune systems. In this Review, we focus on our current understanding of the distinct and overlapping effects of interleukin-2 (IL-2), IL-7, IL-9, IL-15 and IL-21, as well as the IL-7-related cytokine thymic stromal lymphopoietin (TSLP), on the survival and proliferation of conventional alphabeta T cells, gammadelta T cells and regulatory T cells. This knowledge potentially allows for the therapeutic manipulation of immune responses for the treatment of cancer, autoimmunity, allergic diseases and immunodeficiency, as well as for vaccine development.

MicroRNA-21 is up-regulated in allergic airway inflammation and regulates IL-12p35 expression

Allergic airway inflammation is characterized by marked in situ changes in gene and protein expression, yet the role of microRNAs (miRNAs), a new family of key mRNA regulatory molecules, in this process has not yet been reported. Using a highly sensitive microarray-based approach, we identified 21 miRNAs with differential expression between doxycycline-induced lung-specific IL-13 transgenic mice (with allergic airway inflammation) and control mice. In particular, we observed overexpression of miR-21 and underexpression of miR-1 in the induced IL-13 transgenic mice compared with control mice. These findings were validated in two independent models of allergen-induced allergic airway inflammation and in IL-4 lung transgenic mice. Although IL-13-induced miR-21 expression was IL-13Ralpha1 dependent, allergen-induced miR-21 expression was mediated mainly independent of IL-13Ralpha1 and STAT6. Notably, predictive algorithms identified potential direct miR-21 targets among IL-13-regulated lung transcripts, such as IL-12p35 mRNA, which was decreased in IL-13 transgenic mice. Introduction of pre-miR-21 dose dependently inhibited cellular expression of a reporter vector harboring the 3'-untranslated region of IL-12p35. Moreover, mutating miR-21 binding sites in IL-12p35 3'-untranslated region abrogated miR-21-mediated repression. In summary, we have identified a miRNA signature in allergic airway inflammation, which includes miR-21 that modulates IL-12, a molecule germane to Th cell polarization.

Altered lymphocyte homeostasis after oral prion infection in mouse

Transmissible spongiform encephalopathies (TSEs) or prion diseases develop as central nervous system (CNS) disorders characterized by extremely long incubation periods. Although TSEs do not go along with inflammatory infiltrates and/or antibody production against the prion protein (PrP(Sc)), the immune system plays an important role in pathogenesis as long as different lymphoid organs (Peyer's patches, lymph nodes and spleen) may facilitate the accumulation and further spread of prions after peripheral exposure. In this work we investigated the changes in lymphoid and dendritic cell (DC) populations as well as the implications of different cytokines during disease progression after experimental oral inoculation of prions in a transgenic mouse model. At different days post-inoculation (dpi), T and B lymphocytes and DC populations from lymphoid organs, blood and brain were analyzed by flow cytometry and immunohistochemistry. Besides time related variations in lymphoid cell numbers due to the aging of the animals significant changes related with the infection were found in mesenteric lymph nodes, peripheral blood leukocytes (PBLs) as well as in spleen, affecting the CD4/CD8 ratio. In contrast, little or no variation was detected in Peyer's Patches or in thymus either associated with aging or the infection status. At individual time points significant differences between infected and control mice were seen in the CD8, CD4 and DC populations, with less evidence of differences in the B cell compartment. Finally, a pro-inflammatory phenotype occurred at early times in the spleen, where the levels of lymphotoxin-beta mRNA were found augmented with respect to controls. Altogether, these results suggest that normal regulation of lymphocyte populations becomes altered along the progression of a prion infection.

Dendritic cell vaccination

There has been a surge of interest in the use of dendritic cell (DC) vaccination as cellular immunotherapy for numerous cancers. Despite some encouraging results, this therapeutic modality is far from being considered as a therapy for cancer. This review will first discuss preclinical DC vaccination in murine models of cancer, with an emphasis on comparative studies investigating different methods of antigen priming. We will then comment on the various murine DC subsets and how these relate to human DC preparations used for clinical studies. Finally, the methodology used to generate human DCs and some recent clinical trials in several cancers are reviewed.

AML-loaded DC generate Th1-type cellular immune responses in vitro

BACKGROUND

The generation of AML-specific T-lymphocyte responses by leukemia-derived DC has been documented by multiple investigators and is being pursued clinically. An obstacle to widespread use of this strategy is that it has not been possible to generate leukemic DC from all patients, and an alternative approach is needed if the majority of leukemia patients are to receive therapeutic vaccination in conjunction with other treatment protocols.

METHODS

In the present study, we generated DC from CD14-selected monocytes isolated from healthy donor PBPC and loaded them with a total cell lysate from AML patient blasts.

RESULTS

Immature in vitro-derived DC exhibited robust phagocytic activity, and mature DC demonstrated high expression of CD80, CD83, CD86 and the chemokine receptor CCR7, important for DC migration to local lymph nodes. Mature, Ag-loaded DC were used as APC for leukemia-specific cytotoxic T-lymphocyte (CTL) induction and demonstrated cytotoxic activity against leukemic targets. CTL lysis was Ag-specific, with killing of both allogeneic leukemic blasts and autologous DC loaded with allogeneic AML lysate. HLA-matched controls were not lysed in our system.

DISCUSSION

These data support further research into the use of this strategy as an alternative approach to leukemia-derived DC vaccination.

Dendritic cells differentiated in the presence of IFN-β and IL-3 are potent inducers of an antigen-specific CD8+T cell response

Dendritic cells (DC) are professional antigen-presenting cells that are used in vaccine approaches to cancer. Classically, mature monocyte-derived DC are generated in vitro in the presence of interleukin (IL)-4, granulocyte macrophage-colony stimulating factor, and inflammatory cytokines (G4-DC). Recently, it has been described that DC can also be generated in the presence of IL-3 and interferon (IFN)-beta and that these DC are efficiently matured using polyriboinosinic polyribocytidylic acid (I3-DC). In this study, a series of in vitro experiments was performed to compare side-by-side I3-DC and G4-DC as vaccine adjuvants. Phenotypic characterization of the DC revealed differences in the expression of the monocyte marker CD14 and the maturation marker CD83. Low expression of CD14 and high expression of CD83 characterized G4-DC, whereas I3-DC displayed intermediate expression of CD14 and CD83. Both types of DC were as potent in the induction of allogeneic T cell proliferation. Upon CD40 ligation, G4-DC produced lower amounts of IFN-alpha and pulmonary and activation-regulated chemokine, similar amounts of IL-6, macrophage-inflammatory protein (MIP)-1alpha, and MIP-1beta, and higher amounts of IL-12 p70, tumor necrosis factor alpha, and MIP-3beta than I3-DC. We further evaluated whether the DC could be frozen/thawed without loss of cell number, viability, phenotype, and function. After freezing/thawing, 56.0% +/- 9.0% of I3-DC and 77.0% +/- 3.0% of G4-DC (n=9) were recovered as viable cells, displaying the same phenotype as their fresh counterparts. Finally, in vitro stimulations showed that fresh and frozen peptide-loaded I3-DC are more potent inducers of Melan-A-specific CD8(+) T cell responses than G4-DC. The antigen-specific T cells were functional as shown in cytotoxicity and IFN-gamma secretion assay.

Targeting the innate immune response with improved vaccine adjuvants

Despite two centuries of vaccine use, only a few adjuvants and delivery systems are licensed for human use. This is partly because traditional vaccines based on attenuated live organisms already have them--their invasiveness provides efficient delivery to antigen-presenting cells and various naturally occurring components of the pathogens stimulate the innate immune system. But consideration of these immune potentiators and delivery systems has become important to the development of new subunit vaccines consisting of isolated antigens. Here we consider rational approaches to the discovery and development of immunostimulatory compounds and vaccine formulations that target innate immune responses.

Direct intralymphatic injection of peptide vaccines enhances immunogenicity

Research to enhance the efficiency of vaccines focuses mainly on improving either the adjuvant or the type and form of the antigen. This study evaluates the influence of the administration route on the efficiency of a peptide-based vaccine. Peptide vaccines are generally administered subcutaneously or intradermally, from where they must reach secondary lymphatic organs to induce an immune response. We analyzed the efficacy of peptide vaccines administered directly into a lymph node. Using a MHC class I-binding peptide from lymphocytic choriomeningitis virus, we found that intralymphatic injection enhanced immunogenicity by as much as 10(6) times when compared to subcutaneous and intradermal vaccination. Intralymphatic administration induced CD8 T cell responses with strong cytotoxic activity and IFN-gamma production that conferred long-term protection against viral infections and tumors. These results should have immediate implications for clinical immunotherapy of infectious disease and cancer.

Reduced antigen concentration and costimulatory blockade increase IFN-gamma secretion in naive CD8+ T cells

CD8+ T cells are killer cells but also major producers of IFN-gamma. We have investigated the effects of peptide antigen titration and costimulatory blockade on IFN-gamma production and proliferation by naive CD8+ T cells. Mature dendritic cells (DC) pulsed with high amounts of agonist peptide triggered proliferation but little IFN-gamma secretion in individual T cells. In contrast, immature DC pulsed with similar amounts of peptide induced IFN-gamma secretion in a larger fraction of T cells but triggered less proliferation. Blocking B7.2 or lowering the amount of peptide on mature DC led to a response similar to that induced by immature DC, suggesting that differences in stimulatory strength were responsible for the different responses. Using splenic antigen-presenting cells (APC) we demonstrate that reducing the amount of peptide in combination with B7 blockage enhanced IFN-gamma secretion and decreased proliferation in naive CD8+ T cells in an additive way. Our data suggest that IFN-gamma secretion and proliferation are independently and inversely controlled by stimulatory strength in naive CD8+ T cells. This may enable CD8+ T cells to respond with IFN-gamma secretion to immature APC with few peptide ligands consistent with an early immunoregulatory role of CD8+ T cells.

Challenges facing adjuvants for cancer immunotherapy

An adjuvant is defined as a product that increases or modulates the immune response against an antigen (Ag). Based on this general definition many authors have postulated that the ideal adjuvant should increase the potency of the immune response, while being non-toxic and safe. Although dozens of different adjuvants have been shown to be effective in preclinical and clinical studies, only aluminium-based salts (Alum) and squalene-oil-water emulsion (MF59) have been approved for human use. However, for the development of therapeutic vaccines to treat cancer patients, the prerequisites for an ideal cancer adjuvant differ from conventional adjuvants for many reasons. First, the patients that will receive the vaccines are immuno-compromised because of, for example, impaired mechanisms of antigen presentation, non-responsiveness of activated T cells and enhanced inhibition of self-reactivity by regulatory T cells. Second, the tumour Ag are usually self-derived and are, therefore, poorly immunogenic. Third, tumours develop escape mechanisms to avoid the immune system, such as tumour editing, low or non-expression of MHC class I molecules or secretion of suppressive cytokines. Thus, adjuvants for cancer vaccines need to be more potent than for prophylactic vaccines and consequently may be more toxic and may even induce autoimmune reactions. In summary, the ideal cancer adjuvant should rescue and increase the immune response against tumours in immuno-compromised patients, with acceptable profiles of toxicity and safety. The present review discusses the role of cancer adjuvants at the different phases of the generation of antitumour immunity following vaccination.

Preventative and therapeutic vaccines for cervical cancer

"High-risk" genotypes of the human papillomavirus (HPV), most commonly HPV genotype 16, are the primary etiologic agents of cervical cancer. Indeed HPV DNA is detected in 99% of cervical carcinomas. Thus, cervical cancer and other HPV-associated malignancies might be prevented or treated by the induction of the appropriate viral-antigen-specific immune responses. Transmission of papillomavirus may be prevented by the generation of antibodies to capsid proteins L1 and L2 that neutralize viral infection. HPV L1 virus-like particles (VLPs) show great promise as prophylactic HPV vaccines in ongoing clinical trials but L2-based preventative vaccines have yet to be tested in patients. Since the capsid proteins are not expressed at detectable levels by infected basal keratinocytes or in HPV-transformed cells, therapeutic vaccines generally target the nonstructural early viral antigens. Two HPV oncogenic proteins, E6 and E7, are critical to the induction and maintenance of cellular transformation and are co-expressed in the majority of HPV-containing carcinomas. Although other early viral antigens show promise for vaccination against papillomas, therapeutic vaccines targeting E6 and E7 may provide the best opportunity to control HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 are administered in live vectors, as peptides or proteins, in nucleic acid form, as components of chimeric VLPs, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. Should this new generation of HPV preventative and therapeutic vaccines function in patients as demonstrated in animal models, oncogenic HPV infection and its associated malignancies could be controlled by vaccination. Importantly, recent advances in HPV detection and continued improvements in screening further enhance our opportunities to systematically eradicate HPV-associated malignancy.

A systematic strategy to optimize ex vivo expansion medium for human hematopoietic stem cells derived from umbilical cord blood mononuclear cells

OBJECTIVE

In this study, a serum-free, stroma-free, and chemically defined medium for hematopoietic stem cell (HSC) expansion was systematically developed and optimized using factorial design and the steepest ascent method.

MATERIALS AND METHODS

Mononuclear cells (MNCs) were isolated from umbilical cord blood (UCB). HSCs were stimulated to proliferate ex vivo in the MNC culture system with variable serum substitutes, cytokines, and basal media according to experimental design. The expanded cells were assessed for cellular characteristics by surface antigen analysis, colony-forming cell assay (CFC assay), and long-term culture-initiating cell assay (LTC-IC assay).

RESULTS

The optimal compositions of serum substitutes and the cytokine cocktail for HSC expansion in the MNC culture system were BIT (4 g/L BSA, 0.71 microg/mL insulin, and 27.81 microg/mL transferrin), and CC-9 (5.53 ng/mL TPO, 2.03 ng/mL IL-3, 16 ng/mL SCF, 4.43 ng/mL FL, 2.36 ng/mL IL-6, 1.91 ng/mL G-CSF, 1.56 ng/mL GM-CSF, 2.64 ng/mL SCGF, and 0.69 ng/mL IL-11) in the Iscove's modified Dulbecco's medium. After 6-day culture, the absolute fold expansions for white blood cells, CD34+ cells, CD34+CD38- cells, CFC, and LTC-IC were 1.4-, 30.4-, 63.9-, 10.7-, 2.8-fold, respectively.

CONCLUSION

Using the statistic methodology to develop HSC medium, our formula had lower cytokine concentrations comparing to other literatures and commercial media, but had superior or comparable expansion ability on HSC growth.

IL-4 confers NK stimulatory capacity to murine dendritic cells: a signaling pathway involving KARAP/DAP12-triggering receptor expressed on myeloid cell 2 molecules

Dendritic cells (DC) regulate NK cell functions, but the signals required for the DC-mediated NK cell activation, i.e., DC-activated NK cell (DAK) activity, remain poorly understood. Upon acute inflammation mimicked by LPS or TNF-alpha, DC undergo a maturation process allowing T and NK cell activation in vitro. Chronic inflammation is controlled in part by Th2 cytokines. In this study, we show that IL-4 selectively confers to DC NK but not T cell stimulatory capacity. IL-4 is mandatory for mouse bone marrow-derived DC grown in GM-CSF (DC(GM/IL-4)) to promote NK cell activation in the draining lymph nodes. IL-4-mediated DAK activity depends on the KARAP/DAP12-triggering receptor expressed on myeloid cell 2 signaling pathway because: 1) gene targeting of the adaptor molecule KARAP/DAP12, a transmembrane polypeptide with an intracytoplasmic immunoreceptor tyrosine-based activation motif, suppresses the DC(GM/IL-4) capacity to activate NK cells, and 2) IL-4-mediated DAK activity is significantly blocked by soluble triggering receptor expressed on myeloid cell 2 Fc molecules. These data outline a novel role for Th2 cytokines in the regulation of innate immune responses through triggering receptors expressed on myeloid cells.

A novel phosphoprotein is induced during bone marrow commitment to dendritic cells

Dendritic cells (DCs) play an important role in vertebrate immunity, but little is known of the molecular events associated with their development from bone marrow (BM). This report describes induction of a signature protein marking BM commitment to DCs. Using a standard procedure, DCs were generated from BM by cultivation in vitro. Appropriate phenotypic monitoring was done primarily by immunofluorescence, and polyclonal antibody reagents were developed against immature DC lysates. Using one specific antibody reagent, we identified, purified, and sequenced a unique cytosolic phosphoprotein DP58 that occurs within 30 min during BM commitment to DCs. Its sequence matches with a computationally predicted Riken cDNA (GenBank Accession No. XP_138799), and a specific anti-DP58 peptide antibody was developed for further characterization. The study suggests that DP58 induction signals distinct pathway(s) leading to early DC progenitors that may be generated and propagated for a short period in vitro.

CpG-ODN-stimulated dendritic cells act as a potent adjuvant for E7 protein delivery to induce antigen-specific antitumour immunity in a HPV 16 E7-associated animal tumour model

We previously reported that both E7 and CpG-oligodeoxynucleotide (ODN) are required for protecting animals from human papillomavirus (HPV) 16 E7-associated tumour challenge. Here we investigate dendritic cells (DC)-based approach in this protection. In the study, we isolated bone marrow-derived DC and stimulated DC with E7 and ODN. In vitro stimulation of DC with E7 plus ODN resulted in more production of interleukin-12, as compared to that with E7 or ODN alone. Further injection with E7+ODN-stimulated DC resulted in more significant tumour protection, as compared to stimulation with E7 or ODN alone. We further evaluated the levels of immune responses induced by DC stimulated with E7+ODN. We observed little enhancement of E7-specific antibody and T helper cell proliferative responses by E7+ODN stimulation, as compared to E7 stimulation. However, there was some enhancement of interferon-gamma (IFN-gamma) production from CD4+ T cells and a more significant production of IFN-gamma from CD8+ T cells by E7+ODN stimulation, as compared to E7 stimulation alone. This was consistent with intracellular IFN-gamma staining levels of CD8+ T cells. Tumour protection further appeared to be mediated by CD8+ T cells, as determined by in vivo T-cell depletion. Thus, these data suggest that upon ODN stimulation DC might function as a potent adjuvant for E7 protein delivery for induction of protective cellular immunity against HPV E7-associated tumour challenge.

Enhancement of antigen-presenting capacity and antitumor immunity of dendritic cells pulsed with autologous tumor-derived RNA in mice

Dendritic cells (DCs) are antigen-presenting cells that play an important role in antitumor immunity. Several studies have reported that DCs pulsed with RNA from tumor cells have the ability to suppress tumors, but the details regarding the function and the immune-mechanism of DCs transfected with RNA remain to be elucidated. In this study, we investigated the transfection efficiency of RNA into DCs, and the functional modification and the antitumor efficacy of DCs pulsed with tumor-derived RNA. After the transfection of tumor-derived RNA into DCs cultured from the bone marrow of mice, pulsed DCs exhibited a high expression of both MHC antigens and CD86 on the cell surface as well as cultured DCs, and had a stronger ability both to present antigen on the MHC antigens and to stimulate T cells compared with DCs without transfection. DCs could sufficiently translate luciferase encoding RNA into luciferase proteins, and luciferase protein was expressed up to 12 hours in pulsed DCs. The DCs pulsed with tumor-derived RNA could elite a potent induction of cytotoxic T lymphocytes against autologous tumors, but not lysis against syngeneic normal cells. RNA-pulsed DCs exhibited a significant antitumor immunity in animal model. In conclusion, DCs could sufficiently uptake exogenous tumor-derived RNA, and consequently grow to be an intermediate maturate type, and induce potent T-cell stimulation and fully cause an antitumor effect in vivo. Therapy with DCs pulsed with tumor-derived RNA is sufficiently effective and safe, and thus it is considered to be clinically useful for tumor-immunotherapy.

Disparate functions of immature and mature human myeloid dendritic cells: implications for dendritic cell-based vaccines

Although antigen-loaded dendritic cells (DC) are being investigated as antitumor vaccines, which DC differentiation state is most effective is not clear. Three DC functions that may be critical for immunization potential are expression of CD80/86, cytokine production following CD40 engagement, and migration to chemokine receptor 7-binding chemokines. We therefore examined highly purified human monocyte-derived immature and mature DC for these properties from normal donors and cancer patients. Although high expression of CD80/86 and migration to 6Ckine + macrophage-inflammatory protein-3beta were properties of mature DC, cytokine production following CD40 ligation was superior by immature DC. Loss of cytokine secretion occurred with multiple maturation conditions, was not apparently reversible, and was also seen with lipopolysaccharide stimulation in correlation with down-regulated Toll-like receptor expression. Our results suggest that the functions thought to contribute to optimal T cell priming are not coexpressed by the same DC population and that immature and mature DC likely possess distinct CD40-mediated signaling events.

Current developments in cancer vaccines and cellular immunotherapy

This article reviews the immunologic basis of clinical trials that test means of tumor antigen recognition and immune activation, with the goal to provide the clinician with a mechanistic understanding of ongoing cancer vaccine and cellular immunotherapy clinical trials. Multiple novel immunotherapy strategies have reached the stage of testing in clinical trials that were accelerated by recent advances in the characterization of tumor antigens and by a more precise knowledge of the regulation of cell-mediated immune responses. The key steps in the generation of an immune response to cancer cells include loading of tumor antigens onto antigen-presenting cells in vitro or in vivo, presenting antigen in the appropriate immune stimulatory environment, activating cytotoxic lymphocytes, and blocking autoregulatory control mechanisms. This knowledge has opened the door to antigen-specific immunization for cancer using tumor-derived proteins or RNA, or synthetically generated peptide epitopes, RNA, or DNA. The critical step of antigen presentation has been facilitated by the coadministration of powerful immunologic adjuvants, the provision of costimulatory molecules and immune stimulatory cytokines, and the ability to culture dendritic cells. Advances in the understanding of the nature of tumor antigens and their optimal presentation, and in the regulatory mechanisms that govern the immune system, have provided multiple novel immunotherapy intervention strategies that are being tested in clinical trials.

Induction of specific antitumor immunity in the mouse with the electrofusion product of tumor cells and dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells capable of inducing primary T-cell responses. Several immunotherapy treatment strategies involve manipulation of DCs, both in vivo and ex vivo, to promote the immunogenic presentation of tumor-associated antigens. In this study, an electrofusion protocol was developed to induce fusion between tumor cells and allogeneic bone marrow-derived DCs. Preimmunization with irradiated electrofusion product was found to provide partial to complete protection from tumor challenge in the murine Renca renal cell carcinoma model and the B16 and M3 melanoma models. Vaccinated survivors developed specific immunological memory and were able to reject a subsequent rechallenge with the same tumor cells but not a syngeneic unrelated tumor line. Antitumor protection in the B16 model was accompanied by the development of a polyclonal cytotoxic T-lymphocyte response against defined melanoma-associated antigens. The therapeutic potential of this type of approach was suggested by the ability of a Renca-DC electrofusion product to induce tumor rejection in a substantial percentage of hosts (60%) bearing pre-established tumor cells. These results indicate that treatment with electrofused tumor cells and allogeneic DCs is capable of inducing a potent antitumor response and could conceivably be applied to a wide range of cancer indications for which tumor-associated antigens have not been identified.

Antitumor immunopreventive and immunotherapeutic effect in mice induced by hybrid vaccine of dendritic cells and hepatocarcinoma in vivo

AIM: To develop atumor vaccine by fusion of H22 hepatocarcinoma cells and DC, and to study its protective and therapeutical effect against H22 cell.

METHODS: H22-DC vaccine was produced by PEG fusion of H22 and DC induced by cytokine released from splenic mononuclear cells, sorted by CD11c magnetic microbead marker. It was injected through the tail vein of the mice and the H₂₂-DC oncogenesis was detected in the liver, spleen and lung. In order to study the therapeutical and protective effect of H₂₂-DC against tumor H₂₂, two groups were divided: immune group and therapeutic group. Immune group was further divided into P, D, HD and H subgroups, immunized by PBS, DC, H₂₂-DC and inactivated H₂₂, respectively, and attacked by H₂₂ cell. The tumor size, tumor weight, mice survival time and tumor latent period were recorded and statistically analyzed; Therapeutical group was divided into three subgroups of P, D and HD, and attacked by H₂₂, then treated with PBS, DC, and H₂₂-DC, respectively. Pathology and flow cytometry were also applied to study the mechanism how the H₂₂-DC vaccine attacked on the H₂₂ cell.

RESULTS: 1. No oncogenesis was found in spleen, lung and liver after H22-DC injection. 2. Hybrid vaccine immunized mice had strongest CTL activity. 3. In the immune group, latent period was longer in HD subgroup than that in P, H and D subgroup; and tumor size and weight were smaller in HD subgroup than that in P, H and D subgroup. 4. In therapeutic group, tumor size was smaller in HD subgroup than that in P, D subgroup.

CONCLUSION: 1. H22-DC tumor vaccine is safe without oncogenesis in vivo. 2. Hybrid vaccine can stimulate potent specific CTL activity against H22. 3. H22-DC vaccine has distinctive prophylatic effect on tumor H22 and can inhibit the tumor growth.

Immune escape mechanisms of childhood ALL and a potential countering role for DC-like leukemia cells

BACKGROUND

Pre-B ALL cells generally elicit a weak immune host response, due to poor expression of co-stimulatory molecules and/or suppression of immune function. A possible way to enhance immunogenicity of pre-B ALL cells is to convert them to DC-like cells.

METHODS

To study the effect of ALL cells on T-cell function, ALL cells were incubated with T adult cells activated by OKT3 MAb. Liquid culture of de novo pre-B ALL cells for 7 days, in a medium containing IL-1alpha, IL-3, IL-7, Flt 3 ligand (L) and tumor-necrosis factor alpha (TNF-alpha) produced DC-like cells. These were evaluated for morphology, viability, phenotype, as measured by flow cytometry, and function, including MLR.

RESULTS

Pre-B ALL cell-lines NALM-6, BALM and de novo pre-B ALL cells failed to stimulate T cells, but suppressed stimulated T cells. The DC-like cells displayed characteristic features of DCs: filiform cytoplasmic projections, and phenotypic expression of co-stimulatory molecules CD80/86, MHC Class I and II molecules, CD83 and CD1a. Genetic monoclonality study confirmed their leukemic origin. In a 5-day MLR culture, the DC-like cells potently activated allogeneic adult and cord CD4+ and CD8+ T cells. Furthermore, both CD4+ and CD8+ T cells were primed towards a Type I. No such effect was seen with unmanipulated de novo pre-B ALL cells.

DISCUSSION

DC-like cells can be generated from childhood pre-B ALL cells and are potent stimulators of adult and naïve cord CD8+ T cells via CD4+ cells. These cells may form part of an immunotherapy strategy to overcome tolerance to ALL cells.

Gene therapy for pancreatic cancer

Gene transfer technology has the potential to revolutionize cancer treatment. Developments in molecular biology, genetics, genomics, stem cell technology, virology, bioengineering, and immunology are accelerating the pace of innovation and movement from the laboratory bench to the clinical arena. Pancreatic adenocarcinoma, with its particularly poor prognosis and lack of effective traditional therapy for most patients, is an area where gene transfer and immunotherapy have a maximal opportunity to demonstrate efficacy. In this review, we have discussed current preclinical and clinical investigation of gene transfer technology for pancreatic cancer. We have emphasized that the many strategies under investigation for cancer gene therapy can be classified into two major categories. The first category of therapies rely on the transduction of cells other than tumor cells, or the limited transduction of tumor tissue. These therapies, which do not require efficient gene transfer, generally lead to systemic biological effects (e.g., systemic antitumor immunity, inhibition of tumor angiogenesis, etc) and therefore the effects of limited gene transfer are biologically "amplified." The second category of gene transfer strategies requires the delivery of therapeutic genetic material to all or most tumor cells. While these elegant approaches are based on state-of-the-art advances in our understanding of the molecular biology of cancer, they suffer from the current inadequacies of gene transfer technology. At least in the short term, it is very likely that success in pancreatic cancer gene therapy will involve therapies that require only the limited transduction of cells. The time-worn surgical maxim, "Do what's easy first," certainly applies here.

Immune response by host after allogeneic chondrocyte transplant to the cartilage

Chondrocytes constitutively express class I and, in some species, class II major histocompatibility complex (MHC). It is also possible that they possess specific differentiation antigen(s). Furthermore, lymphocytic cells, corresponding to NK cells, display spontaneous cytotoxic activity against chondrocytes. Studies on articular cartilage repair by transplants of allogeneic chondrocytes were mainly done on non-inbred animals, such as rabbits and hens. Surprisingly, only in single instances these transplants were rejected. In inbred rats, allogeneic chondrocytes transplanted into full-thickness defects in articular cartilage immediately after isolation evoked systemic immunological reaction and produced cartilage was rejected. Combined immunosuppression with cyclosporin A and cladribine did not prevent rejection of such transplants. Mechanical separation of transplants from bone marrow prevented sensitization of recipients and rejection of the produced cartilage. Successful allogeneic chondrocyte transplants in rabbits and hens could be tentatively explained by a certain degree of inbreeding among experimental animals, by the use of chondrocytes cultivated before grafting in artificial scaffolds and thus protected by matrix produced in vitro, and also by creation of a temporary mechanical barrier between transplant and bone marrow by tissues damaged during preparation of the defect.

Increased generation of dendritic cells from myeloid progenitors in autoimmune-prone nonobese diabetic mice

Aberrant dendritic cell (DC) development and function may contribute to autoimmune disease susceptibility. To address this hypothesis at the level of myeloid lineage-derived DC we compared the development of DC from bone marrow progenitors in vitro and DC populations in vivo in autoimmune diabetes-prone nonobese diabetic (NOD) mice, recombinant congenic nonobese diabetes-resistant (NOR) mice, and unrelated BALB/c and C57BL/6 (BL/6) mice. In GM-CSF/IL-4-supplemented bone marrow cultures, DC developed in significantly greater numbers from NOD than from NOR, BALB/c, and BL/6 mice. Likewise, DC developed in greater numbers from sorted (lineage(-)IL-7Ralpha(-)SCA-1(-)c-kit(+)) NOD myeloid progenitors in either GM-CSF/IL-4 or GM-CSF/stem cell factor (SCF)/TNF-alpha. [(3)H]TdR incorporation indicated that the increased generation of NOD DC was due to higher levels of myeloid progenitor proliferation. Generation of DC with the early-acting hematopoietic growth factor, flt3 ligand, revealed that while the increased DC-generative capacity of myeloid-committed progenitors was restricted to NOD cells, early lineage-uncommitted progenitors from both NOD and NOR had increased DC-generative capacity relative to BALB/c and BL/6. Consistent with these findings, NOD and NOR mice had increased numbers of DC in blood and thymus and NOD had an increased proportion of the putative myeloid DC (CD11c(+)CD11b(+)) subset within spleen. These findings demonstrate that diabetes-prone NOD mice exhibit a myeloid lineage-specific increase in DC generative capacity relative to diabetes-resistant recombinant congenic NOR mice. We propose that an imbalance favoring development of DC from myeloid-committed progenitors predisposes to autoimmune disease in NOD mice.

Characterization of an early dendritic cell precursor derived from murine lineage-negative hematopoietic progenitor cells

OBJECTIVE

We define characteristics of a dendritic cell (DC) precursor generated from murine lineage-negative (Lin(-)) Sca1(+) hematopoietic progenitor cells (HPC).

MATERIALS AND METHODS

Lin(-)Sca1(+) HPC cultured 9 days in 100 ng/mL stem cell factor (SCF), 20 ng/mL interleukin-3 (IL-3), 50 ng/mL monocyte colony-stimulating factor (M-CSF), 5 ng/mL granulocyte-monocyte colony-stimulating factor (GM-CSF), and 25 ng/mL FLT3-ligand (FLT3-L) proliferate 387-fold and differentiate into DC precursors. Switch to > or =100 ng/mL GM-CSF + 1500 U/mL IL-4 or 500 U/mL tumor necrosis factor-alpha (TNF-alpha) for 3 days induces development into immature DC that are responsive to bacterial lipopolysaccharide (LPS)-induced maturation.

RESULTS

Lin(-)Sca1(+) HPC in the first 9 days of culture differentiate into DC precursors expressing surface CD11b(bright), CD11c(mod), CD86(low-mod), major histocompatibility class II antigen (MHC) II(low), DEC 205(low), but are surface CD40(-) and contain high levels of intracellular MHC II. Unlike immature DC described by others, these DC precursors are refractory to maturation with LPS and minimally stimulate allogeneic T lymphocytes in mixed leukocyte reactions (MLR). Switch to high-dose GM-CSF alone with IL-4 or TNF-alpha differentiates these DC precursors into immature DC. LPS treatment of the immature DC results in mature DC that express surface CD40(high) and CD86(high), secrete IL-1beta and IL-12, and strongly stimulate MLR.

CONCLUSIONS

These studies define a distinct DC precursor derived from murine HPC that precedes development of immature and mature DC.

Increased dendritic cell number and function following continuous in vivo infusion of granulocyte macrophage-colony-stimulating factor and interleukin-4

Dendritic cells (DCs) are rare antigen-presenting cells that play a central role in stimulating immune responses. The combination of recombinant granulocyte macrophage-colony-stimulating factor (rGM-CSF) and recombinant interleukin-4 (rIL-4) provides an important stimulus for generating DCs from murine bone marrow precursors in vitro. Using miniature osmotic pumps, we now demonstrate that continuous infusion of these cytokines for 7 days had a similar effect in vivo, increasing the number and function of splenic DCs. Administration of rGM-CSF/rIL-4 (10 microg/d each) increased the concentration of CD11(+) DCs by 2.7-fold and the absolute number of splenic DCs by an average of 5.7-fold. DC number also increased in peripheral blood and lymph nodes. The resultant DCs exhibited a different phenotype and function than those in control mice or mice treated with rGM-CSF alone. rGM-CSF/IL-4 increased both the myeloid (CD11c(+)/CD11b(+)) and the lymphoid (CD11c(+)/CD8alpha(+)) subpopulations, whereas rGM-CSF increased only myeloid DCs. DCs were highly concentrated in the T-cell areas of white pulp after rGM-CSF/IL-4 administration, whereas they were diffusely distributed throughout white pulp, marginal zones, and red pulp in mice treated with rGM-CSF alone. rGM-CSF/rIL-4 also significantly increased the expression of major histocompatibility complex (MHC) class I and MHC class II on CD11c(+) cells and increased their capacity to take up antigens by macropinocytosis and receptor-mediated endocytosis. Splenic DCs generated in response to rGM-CSF/rIL-4 were functionally immature in terms of allostimulatory activity, but this activity increased after short-term in vitro culture. Systemic treatment with rGM-CSF/rIL-4 enhanced the response to an adenoviral-based vaccine and led to antigen-specific retardation in the growth of established tumor. We conclude that systemic therapy with the combination of rGM-CSF/rIL-4 provides a new approach for generating DCs in vivo.