Dendritic cells genetically modified with an adenovirus vector encoding the cDNA for a model antigen induce protective and therapeutic antitumor immunity

The role of immunogenic cell death in gastrointestinal cancer immunotherapy (Review)

Modern cancer immunotherapy techniques are aimed at enhancing the responses of the patients' immune systems to fight against the cancer. The main promising strategies include active vaccination of tumor antigens, passive vaccination with antibodies specific to cancer antigens, adoptive transfer of cancer-specific T cells and manipulation of the patient's immune response by inhibiting immune checkpoints. The application of immunogenic cell death (ICD) inducers has been proven to enhance the immunity of patients undergoing various types of immunotherapy. The dying, stressed or injured cells release or present molecules on the cell surface, which function as either adjuvants or danger signals for detection by the innate immune system. These molecules are now termed 'damage-associated molecular patterns'. The term 'ICD' indicates a type of cell death that triggers an immune response against dead-cell antigens, particularly those derived from cancer cells, and it was initially proposed with regards to the effects of anticancer chemotherapy with conventional cytotoxic drugs. The aim of the present study was to review and discuss the role and mechanisms of ICD as a promising combined immunotherapy for gastrointestinal tumors.

Role of the PD-1/PD-L1 Dyad in the Maintenance of Pancreatic Immune Tolerance for Prevention of Type 1 Diabetes

The human pancreas, like almost all organs in the human body, is immunologically tolerated despite the presence of innate and adaptive immune cells that promptly mediate protective immune responses against pathogens in situ. The PD-1/PD-L1 inhibitory pathway seems to play a key role in the maintenance of immune tolerance systemically and within the pancreatic tissue. Tissue resident memory T cells (TRM), T regulatory cells (Treg), macrophages and even β cells exhibit PD-1 or PD-L1 expression that contributes in controlling pancreatic immune homeostasis and tolerance. Dysregulation of the PD-1/PD-L1 axis as shown by animal studies and our recent experience with checkpoint inhibitory blockade in humans can lead to immune dysfunctions leading to chronic inflammatory disease and to type 1 diabetes (T1D) in genetically susceptible individuals. In this review, we discuss the role of the PD-1/PD-L1 axis in pancreatic tissue homeostasis and tolerance, speculate how genetic and environmental factors can regulate the PD-1/PD-L1 pathway, and discuss PD-1/PD-L1-based therapeutic approaches for pancreatic islet transplantation and T1D treatment.

A Novel Anti-PD-L1 Vaccine for Cancer Immunotherapy and Immunoprevention

Dendritic cells (DCs) are potent antigen-presenting cells that play a critical role in activating cellular and humoral immune responses. DC-based tumor vaccines targeting tumor-associated antigens (TAAs) have been extensively tested and demonstrated to be safe and potent in inducing anti-TAA immune responses in cancer patients. Sipuleucel-T (Provenge), a cancer vaccine of autologous DCs loaded with TAA, was approved by the United States Food and Drug Administration (FDA) for the treatment of castration-resistant prostate cancer. Sipuleucel-T prolongs patient survival, but has little or no effect on clinical disease progression or biomarker kinetics. Due to the overall limited clinical efficacy of tumor vaccines, there is a need to enhance their potency. PD-L1 is a key immune checkpoint molecule and is frequently overexpressed on tumor cells to evade antitumor immune destruction. Repeated administrations of PD-L1 or PD-1 antibodies have induced sustained tumor regression in a fraction of cancer patients. In this study, we tested whether vaccinations with DCs, loaded with a PD-L1 immunogen (PDL1-Vax), are able to induce anti-PD-L1 immune responses. We found that DCs loaded with PDL1-Vax induced anti-PD-L1 antibody and T cell responses in immunized mice and that PD-L1-specific CTLs had cytolytic activities against PD-L1⁺ tumor cells. We demonstrated that vaccination with PDL1-Vax DCs potently inhibited the growth of PD-L1⁺ tumor cells. In summary, this study demonstrates for the first time the principle and feasibility of DC vaccination (PDL1-Vax) to actively induce anti-PD-L1 antibody and T cell responses capable of inhibiting PD-L1⁺ tumor growth. This novel anti-PD-L1 vaccination strategy could be used for cancer treatment and prevention.

Fusion Hybrid of Dendritic Cells and Engineered Tumor Cells Expressing Interleukin-12 Induces Type 1 Immune Responses against Tumor

Aims and Background

Dendritic cell (DC)-tumor fusion hybrid vaccinees that facilitate antigen presentation represent a novel powerful strategy in cancer immunotherapy. Preclinical studies have demonstrated that IL-12 promotes specific antitumor immunity mediated by T cells in several types of tumors. In the present study, we investigated the antitumor immunity derived from vaccination of fusion hybrids between DCs and engineered J558/IL-12 myeloma cells secreting Th1 cytokine IL-12.

Methods

The expression vector pcDNA-IL-12 was generated and transfected into J558 myeloma cells and then bone marrow-derived DCs were fused with engineered J558/IL-12 cells. The antitumor immunity derived from vaccination of the fusion hybrid DC/J558/IL-12 was evaluated in vitro and in vivo.

Results

DC/J558/IL-12 cells secreted recombinant IL-12 (1.6 ng/mL), and inoculation of BALB/c mice with DC/J558/IL-12 hybrid induced a Th1 dominant immune response and resulted in tumor regression. Immunization of mice with engineered DC/J558/IL-12 hybrid elicited stronger J558 tumor-specific cytotoxic T lymphocyte (CTL) responses in vitro as well as more potent protective immunity against J558 tumor challenge in vivo than immunization with the mixture of DCs and J558/IL-12, J558/IL-12 and J558, respectively. Furthermore, the antitumor immunity mediated by DC/J558/1L-12 tumor cell vaccination in vivo appeared to be dependent on CD8+ CTL.

Conclusions

These results demonstrate that the engineered fusion hybrid vaccines that combine Th1 cytokine gene-modified tumor cells with DCs may be an attractive strategy for cancer immunotherapy.

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.

Current State of Dendritic Cell-Based Immunotherapy: Opportunities for in vitro Antigen Loading of Different DC Subsets?

Dendritic cell (DC) based cancer immunotherapy aims at the activation of the immune system, and in particular tumor-specific cytotoxic T lymphocytes (CTLs) to eradicate the tumor. DCs represent a heterogeneous cell population, including conventional DCs (cDCs), consisting of cDC1s, cDC2s, plasmacytoid DCs (pDCs), and monocyte-derived DCs (moDCs). These DC subsets differ both in ontogeny and functional properties, such as the capacity to induce CD4+ and CD8+ T-cell activation. MoDCs are most frequently used for vaccination purposes, based on technical aspects such as availability and in vitro expansion. However, whether moDCs are superior over other DC subsets in inducing anti-tumor immune responses, is unknown, and likely depends on tumor type and composition of the tumor microenvironment. In this review, we discuss cellular aspects essential for DC vaccination efficacy, and the most recent findings on different DC subsets that could be used for DC-based cancer immunotherapy. This can prove valuable for the future design of more effective DC vaccines by choosing different DC subsets, and sheds light on the working mechanism of DC immunotherapy.

Efficacy of intracellular immune checkpoint-silenced DC vaccine

BACKGROUND

DC-based tumor vaccines have had limited clinical success thus far. SOCS1, a key inhibitor of inflammatory cytokine signaling, is an immune checkpoint regulator that limits DC immunopotency.

METHODS

We generated a genetically modified DC (gmDC) vaccine to perform immunotherapy. The adenovirus (Ad-siSSF) delivers two tumor-associated antigens (TAAs), survivin and MUC1; secretory bacterial flagellin for DC maturation; and an RNA interference moiety to suppress SOCS1. A 2-stage phase I trial was performed for patients with relapsed acute leukemia after allogenic hematopoietic stem cell transplantation: in stage 1, we compared the safety and efficacy between gmDC treatment (23 patients) and standard donor lymphocyte infusion (25 patients); in stage 2, we tested the efficacy of the gmDC vaccine for 12 acute myeloid leukemia (AML) patients with early molecular relapse.

RESULTS

gmDCs elicited potent TAA-specific CTL responses in vitro, and the immunostimulatory activity of gmDC vaccination was demonstrated in rhesus monkeys. A stage 1 study established that this combinatory gmDC vaccine is safe in acute leukemia patients and yielded improved survival rate. In stage 2, we observed a complete remission rate of 83% in 12 relapsed AML patients. Overall, no grade 3 or grade 4 graft-versus-host disease incidence was detected in any of the 35 patients enrolled.

CONCLUSIONS

This study, with combinatory modifications in DCs, demonstrates the safety and efficacy of SOCS1-silenced DCs in treating relapsed acute leukemia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01956630.

FUNDING

National Institute of Health (R01CA90427); the Key New Drug Development and Manufacturing Program of the "Twelfth Five-Year Plan" of China (2011ZX09102-001-29); and Clinical Application Research of Beijing (Z131107002213148).

Genetic Modification of the Lung Directed Toward Treatment of Human Disease

Genetic modification therapy is a promising therapeutic strategy for many diseases of the lung intractable to other treatments. Lung gene therapy has been the subject of numerous preclinical animal experiments and human clinical trials, for targets including genetic diseases such as cystic fibrosis and α1-antitrypsin deficiency, complex disorders such as asthma, allergy, and lung cancer, infections such as respiratory syncytial virus (RSV) and Pseudomonas, as well as pulmonary arterial hypertension, transplant rejection, and lung injury. A variety of viral and non-viral vectors have been employed to overcome the many physical barriers to gene transfer imposed by lung anatomy and natural defenses. Beyond the treatment of lung diseases, the lung has the potential to be used as a metabolic factory for generating proteins for delivery to the circulation for treatment of systemic diseases. Although much has been learned through a myriad of experiments about the development of genetic modification of the lung, more work is still needed to improve the delivery vehicles and to overcome challenges such as entry barriers, persistent expression, specific cell targeting, and circumventing host anti-vector responses.

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.

Novel dendritic cell-based vaccination in late stage melanoma

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that play an important role in stimulating an immune response of both CD4(+) T helper cells and CD8(+) cytotoxic T lymphocytes (CTLs). As such, DCs have been studied extensively in cancer immunotherapy for their capability to induce a specific anti-tumor response when loaded with tumor antigens. However, when the most relevant antigens of a tumor remain to be identified, alternative approaches are required. Formation of a dentritoma, a fused DC and tumor cells hybrid, is one strategy. Although initial studies of these hybrid cells are promising, several limitations interfere with its clinical and commercial application. Here we present early experience in clinical trials and an alternative approach to manufacturing this DC/tumor cell hybrid for use in the treatment of late stage and metastatic melanoma.

Immunotherapy for Lewis lung carcinoma utilizing dendritic cells infected with CK19 gene recombinant adenoviral vectors

Dendritic cells (DCs) as 'professional' antigen-presenting cells (APCs) initiate and regulate immune responses to various antigens. DC-based vaccines have become a promising modality in cancer immunotherapy. Cytokeratin 19 (CK19) protein is expressed at high levels in lung cancer and many other tumor cells, suggesting CK19 as a potential tumor-specific target for cancer immune therapy. We constructed a recombinant adenoviral vector containing the CK19 gene (rAd-CK19). DCs transfected with rAd-CK19 were used to vaccinate C57BL/6 mice bearing xenografts derived from Lewis lung carcinoma (LLC) cells. The transfected DCs gave rise to potent CK19-specific cytotoxic T lymphocytes (CTLs) capable of lysing LLC cells. Mice immunized with the rAd-CK19-DCs exhibited significantly attenuated tumor growth (including tumor volume and weight) when compared to the tumor growth of mice immunized with rAd-c DCs or DCs during the 24-day observation period (P<0.05). The results revealed that the mice vaccinated with the rAd-CK19-DCs exhibited a potent protective and therapeutic antitumor immunity to LLC cells in the subcutaneous model along with an inhibitive effect on tumor growth compared to the mice vaccinated with the rAd-c DCs or DCs alone. The present study proposes a meaningful mode of action utilizing rAd-CK19 DCs in lung cancer immunotherapy.

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.

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.

Adenovirus-based vaccine with epitopes incorporated in novel fiber sites to induce protective immunity against Pseudomonas aeruginosa

Adenovirus (Ad) vector-based vaccines displaying pathogen-derived epitopes on Ad capsid proteins can elicit anti-pathogen immunity. This approach seems to be particularly efficient with epitopes incorporated into the Ad fiber protein. Here, we explore epitope insertion into various sites of the Ad fiber to elicit epitope-specific immunity. Ad vectors expressing the 14-mer Pseudomonas aeruginosa immune-dominant outer membrane protein F (OprF) epitope 8 (Epi8) in five distinct sites of the Ad5 fiber, loops CD (AdZ.F(CD)Epi8), DE (AdZ.F(DE)Epi8), FG (AdZ.F(FG)Epi8), HI (AdZ.F(HI)Epi8) and C terminus (AdZ.F(CT)Epi8), or the hexon HVR5 loop (AdZ.HxEpi8) were compared in their capacity to elicit anti-P. aeruginosa immunity to AdOprF, an Ad expressing the entire OprF protein. Intramuscular immunization of BALB/c mice with AdZ.F(FG)Epi8 or AdZ.F(HI)Epi8 elicited higher anti-OprF humoral and cellular CD4 and CD8 responses as well as enhanced protection against respiratory infection with P. aeruginosa compared to immunization with AdZ.F(CD)Epi8, AdZ.F(DE)Epi8, AdZ.F(CT)Epi8 or AdZ.HxEpi8. Importantly, repeat administration of the fiber- and hexon-modified Ad vectors boosted the OprF-specific humoral immune response in contrast to immunization with AdOprF. Strikingly, following three doses of AdZ.F(FG)Epi8 or AdZ.F(HI)Epi8 anti-OprF immunity surpassed that induced by AdOprF. Furthermore, in the presence of anti-Ad5 immunity, immunization with AdZ.F(FG)Epi8 or AdZ.F(HI)Epi8, but not with AdOprF, induced protective immunity against P. aeruginosa. This suggests that incorporation of epitopes into distinct sites of the Ad fiber is a promising vaccine strategy.

Immunization with adenoviral-vectored tick salivary gland proteins (SALPs) in a murine model of Lyme borreliosis

Prior exposure of vertebrate hosts to tick salivary proteins can induce specific immunity to tick infestation, as well as affording protection against tick-transmitted Borrelia burgdorferi infection in the mammalian host. Vaccination using an adenovirus expression system to deliver 4 tick salivary proteins (Ad-Salps) derived from Ixodes scapularis, Salp15, Salp25A, Salp25D, and Isac, was explored. Results indicate that vaccination with tick salivary proteins in an adenoviral vector can be used to modulate a Th1 response in the host and partially control spirochete load in immunized mice after infected tick challenge.

In vitro induction of anterior gradient-2-specific cytotoxic T lymphocytes by dendritic cells transduced with recombinant adenoviruses as a potential therapy for colorectal cancer

Anterior gradient-2 (AGR2) promotes tumor growth, cell migration, and cellular transformation, and is one of the specific mRNA markers for circulating tumor cells in patients with gastrointestinal cancer. We investigated the feasibility of AGR2 as a potent antigen for tumor immunotherapy against colorectal cancer (CRC) cells using dendritic cells (DCs) transduced with a recombinant adenovirus harboring the AGR2 gene (AdAGR2). DCs transduced with a recombinant adenovirus encoding the AGR2 gene (AdAGR2/DCs) were characterized. These genetically-modified DCs expressed AGR2 mRNA as well as AGR2 protein at a multiplicity of infection of 1,000 without any significant alterations in DC viability and cytokine secretion (IL-10 and IL-12p70) compared with unmodified DCs as a control. In addition, AdAGR2 transduction did not impair DC maturation, but enhanced expression of HLA-DR, CD80, and CD86. AdAGR2/DCs augmented the number of IFN-γ-secreting T-cells and elicited potent AGR2-specific cytotoxic T lymphocytes capable of lysing AGR2-expressing CRC cell lines. These results suggest that AGR2 act as a potentially important antigen for immunotherapy against CRC in clinical applications.

Prolonged expression of MHC class I - peptide expression in bone marrow derived retrovirus transfected matured dendritic cells by continuous centrifugation in the presence of IL-4

Background & objectives:

Dendritic cells (DCs) are potent antigen presenting cells which proceed from immature to a mature stage during their differentiation. There are several methods of obtaining long lasting mature antigen expressing DCs and different methods show different levels of antigen expressions. We investigated bone marrow derived DCs for the degree of maturation and genetically engineered antigen presentation in the presence of interleukin-4 (IL-4) as a maturity enhancer.

Methods:

DCs and transfected retrovirus were cultured together in the presence of granulocyte-macrophage colony stimulating factor (GMCSF)-IL4, GMCSF +IL4, lipopolysaccharide (LPS). B 7.1, B7.2 and CD11c were measured by the degree of immune fluorescence using enhanced green fluorescent protein (EGFP) shuttled retrovirus transfected antigen. Degree of MHC class I molecule with antigen presentation of antigen was also evaluated by fluorescence activated cell sorting. The antigen presenting capacity of transfected DCs was investigated. Bone marrow DCs were generated in the presence of GMCSF and IL-4 in vitro. Dividing bone marrow cells were infected with EGFP shuttled retrovirus expressing SSP2 by prolonged centrifugation for three consecutive days from day 5, 6 and 7 and continued to culture in the presence of GMSCF and IL-4 until day 8.

Results:

IL-4 as a cytokine increased the maturation of retrovirus transfected DCs by high expression of B 7-1 and B 7-2. Also, IL-4 induced DC enhanced by the prolonged centrifugation and it was shown by increased antigen presentation of these dendric cells as antigen presenting cell (APC). Cytolytic effects were significantly higher in cytotoxic T cell response (CTLs) mixed with transfected DCs than CTLs mixed with pulsed DCs.

Interpretation & conclusions:

There was an enhanced antigen presentation by prolonged expression of antigen loaded MHC class I receptors in DCs in the presence of IL-4 by prolonged centrifugation.

Virus-receptor mediated transduction of dendritic cells by lentiviruses enveloped with glycoproteins derived from Semliki Forest virus

Lentiviruses have recently attracted considerable interest for their potential as a genetic modification tool for dendritic cells (DCs). In this study, we explore the ability of lentiviruses enveloped with alphaviral envelope glycoproteins derived from Semliki Forest virus (SFV) to mediate transduction of DCs. We found that SFV glycoprotein (SFV-G)-pseudotyped lentiviruses use C-type lectins (DC-SIGN and L-SIGN) as attachment factors for transduction of DCs. Importantly, SFV-G pseudotypes appear to have enhanced transduction towards C-type lectin-expressing cells when produced under conditions limiting glycosylation to simple high-mannose, N-linked glycans. These results, in addition to the natural DC tropism of SFV-G, offer evidence to support the use of SFV-G-bearing lentiviruses to genetically modify DCs for the study of DC biology and DC-based immunotherapy.

Pseudotyping lentiviral vectors with aura virus envelope glycoproteins for DC-SIGN-mediated transduction of dendritic cells

Lentiviral vectors (LVs) pseudotyped with envelope proteins of alphaviruses have recently attracted considerable interest for their potential as gene delivery tools. We report the production of human immunodeficiency virus type 1 (HIV-1)-derived LVs pseudotyped with envelope glycoproteins derived from the Aura virus (AURA). We found that the AURA-glycoprotein-pseudotyped LVs use C-type lectins (DC-SIGN and L-SIGN) as attachment factors. These interactions with DC-SIGN are specific as determined by inhibition assays and appear to facilitate transduction through a pH-dependent pathway. AURA-pseudotyped LVs were used to transduce monocyte-derived dendritic cells (DCs) and the transduction was shown to be DC-SIGN mediated, as illustrated by competitive inhibition with DC-SIGN and L-SIGN antibodies and yeast mannan. Comparisons with LVs enveloped with glycoproteins derived from vesicular stomatitis virus and Sindbis virus suggest that AURA-glycoprotein-bearing LVs might be useful to genetically modify DCs for the study of DC biology and DC-based immunotherapy.

Dendritic cells adenovirally-transduced with full-length mesothelin cDNA elicit mesothelin-specific cytotoxicity against pancreatic cancer cell lines in vitro

Mesothelin (MSLN) is an attractive candidate as a molecular target for pancreatic cancer immunotherapy. The purpose of this study was to demonstrate that cytotoxic T lymphocytes (CTLs) generated from peripheral blood mononuclear cells (PBMCs) by stimulation with genetically-modified dendritic cells (DCs) expressing MSLN could produce specific anti-tumor immunity against pancreatic cancer cells endogenously expressing MSLN. MSLN-specific CTLs were generated from PBMCs of healthy donors by in vitro stimulation with DCs adenovirally-transduced with the full-length MSLN gene (DC-AxCAMSLN). The cytotoxic activity was tested using a 4-h (51)Cr-release assay. The pancreatic cancer cell lines (PK1, CfPAC1, AsPC1), a lymphoblastoid cell lines (LCL) transduced with the MSLN gene, and LCL pulsed with MSLN-epitope peptides were used as target cells. MSLN-specific CTLs induced by in vitro stimulation with DC-AxCAMSLN killed pancreatic cancer cell lines expressing MSLN in an HLA-restricted fashion. These CTLs also showed cytotoxic activity against autologous LCL pulsed with multiple MSLN-derived epitope peptides. In addition, CD8(+) T cells, as well as CD4(+) T cells, sorted from these CTLs showed significant production of interferon-γ when stimulated with DC-AxCAMSLN. The in vitro stimulation of PBMCs with DCs transduced with the full-length MSLN gene elicited a potent MSLN-specific cytotoxic activity against pancreatic cancer cell lines endogenously expressing MSLN by recognizing multiple MSLN epitopes and activating both CD8(+) T cells and CD4(+) helper T cells. These results therefore suggest the potential of developing future clinical applications of the vaccines using genetically-modified DCs expressing MSLN.

Therapeutic response in patients with advanced malignancies treated with combined dendritic cell-activated T cell based immunotherapy and intensity-modulated radiotherapy

Successful cancer immunotherapy is confounded by the magnitude of the tumor burden and the presence of immunoregulatory elements that suppress an immune response. To approach these issues, 26 patients with advanced treatment refractory cancer were enrolled in a safety/feasibility study wherein a conventional treatment modality, intensity modulated radiotherapy (IMRT), was combined with dendritic cell-based immunotherapy. We hypothesized that radiation would lower the tumor burdens, decrease the number/function of regulatory cells in the tumor environment, and release products of tumor cells that could be acquired by intratumoral injected immature dendritic cells (iDC). Metastatic lesions identified by CT (computed tomography) were injected with autologous iDC combined with a cytokine-based adjuvant and KLH (keyhole limpet hemocyanin), followed 24 h later by IV-infused T-cells expanded with anti-CD3 and IL-2 (AT). After three to five days, each of the injected lesions was treated with fractionated doses of IMRT followed by another injection of intratumoral iDC and IV-infused AT. No toxicity was observed with cell infusion while radiation-related toxicity was observed in seven patients. Five patients had progressive disease, eight demonstrated complete resolution at treated sites but developed recurrent disease at other sites, and 13 showed complete response at various follow-up times with an overall estimated Kaplan-Meier disease-free survival of 345 days. Most patients developed KLH antibodies supporting our hypothesis that the co-injected iDC are functional with the capacity to acquire antigens from their environment and generate an adaptive immune response. These results demonstrate the safety and effectiveness of this multimodality strategy combining immunotherapy and IMRT in patients with advanced malignancies.

Production of lentiviral vectors with enhanced efficiency to target dendritic cells by attenuating mannosidase activity of mammalian cells

Background

Dendritic cells (DCs) are antigen-presenting immune cells that interact with T cells and have been widely studied for vaccine applications. To achieve this, DCs can be manipulated by lentiviral vectors (LVs) to express antigens to stimulate the desired antigen-specific T cell response, which gives this approach great potential to fight diseases such as cancers, HIV, and autoimmune diseases. Previously we showed that LVs enveloped with an engineered Sindbis virus glycoprotein (SVGmu) could target DCs through a specific interaction with DC-SIGN, a surface molecule predominantly expressed by DCs. We hypothesized that SVGmu interacts with DC-SIGN in a mannose-dependent manner, and that an increase in high-mannose structures on the glycoprotein surface could result in higher targeting efficiencies of LVs towards DCs. It is known that 1-deoxymannojirimycin (DMJ) can inhibit mannosidase, which is an enzyme that removes high-mannose structures during the glycosylation process. Thus, we investigated the possibility of generating LVs with enhanced capability to modify DCs by supplying DMJ during vector production.

Results

Through western blot analysis and binding tests, we were able to infer that binding of SVGmu to DC-SIGN is directly related to amount of high-mannose structures on SVGmu. We also found that the titer for the LV (FUGW/SVGmu) produced with DMJ against 293T.DCSIGN, a human cell line expressing the human DC-SIGN atnibody, was over four times higher than that of vector produced without DMJ. In addition, transduction of a human DC cell line, MUTZ-3, yielded a higher transduction efficiency for the LV produced with DMJ.

Conclusion

We conclude that LVs produced under conditions with inhibited mannosidase activity can effectively modify cells displaying the DC-specific marker DC-SIGN. This study offers evidence to support the utilization of DMJ in producing LVs that are enhanced carriers for the development of DC-directed vaccines.

Protective immunity against a lethal respiratory Yersinia pestis challenge induced by V antigen or the F1 capsular antigen incorporated into adenovirus capsid

The aerosol form of the bacterium Yersinia pestis causes pneumonic plague, a rapidly fatal disease that is a biothreat if deliberately released. At present, no plague vaccines are available for use in the United States, but subunit vaccines based on the Y. pestis V antigen and F1 capsular protein show promise when administered with adjuvants. In the context that adenovirus (Ad) gene transfer vectors have a strong adjuvant potential related to the ability to directly infect dendritic cells, we hypothesized that modification of the Ad5 capsid to display either the Y. pestis V antigen or the F1 capsular antigen on the virion surface would elicit high V antigen- or F1-specific antibody titers, permit boosting with the same Ad serotype, and provide better protection against a lethal Y. pestis challenge than immunization with equivalent amounts of V or F1 recombinant protein plus conventional adjuvant. We constructed AdYFP-pIX/V and AdLacZ-pIX/F1, E1(-), E3(-) serotype 5 Ad gene transfer vectors containing a fusion of the sequence for either the Y. pestis V antigen or the F1 capsular antigen to the carboxy-terminal sequence of pIX, a capsid protein that can accommodate the entire V antigen (37 kDa) or F1 protein (15 kDa) without disturbing Ad function. Immunization with AdYFP-pIX/V followed by a single repeat administration of the same vector at the same dose resulted in significantly better protection of immunized animals compared with immunization with a molar equivalent amount of purified recombinant V antigen plus Alhydrogel adjuvant. Similarly, immunization with AdLacZ-pIX/F1 in a prime-boost regimen resulted in significantly enhanced protection of immunized animals compared with immunization with a molar-equivalent amount of purified recombinant F1 protein plus adjuvant. These observations demonstrate that Ad vaccine vectors containing pathogen-specific antigens fused to the pIX capsid protein have strong adjuvant properties and stimulate more robust protective immune responses than equivalent recombinant protein-based subunit vaccines administered with conventional adjuvant, suggesting that F1-and/or V-modified capsid Ad-based recombinant vaccines should be considered for development as anti-plague vaccines.

Trends in cancer immunotherapy

Modulation of the immune system for therapeutic ends has a long history, stretching back to Edward Jenner's use of cowpox to induce immunity to smallpox in 1796. Since then, immunotherapy, in the form of prophylactic and therapeutic vaccines, has enabled doctors to treat and prevent a variety of infectious diseases, including cholera, poliomyelitis, diphtheria, measles and mumps. Immunotherapy is now increasingly being applied to oncology. Cancer immunotherapy attempts to harness the power and specificity of the immune system for the treatment of malignancy. Although cancer cells are less immunogenic than pathogens, the immune system is capable of recognizing and eliminating tumor cells. However, tumors frequently interfere with the development and function of immune responses. Thus, the challenge for cancer immunotherapy is to apply advances in cellular and molecular immunology and develop strategies that effectively and safely augment antitumor responses.

Dendritic cell/tumor hybrids enhances therapeutic efficacy against colorectal cancer liver metastasis in SCID mice

OBJECTIVE

Colorectal cancer (CRC) is one of the most common malignancies in the western world. More than 60% among patients will develop liver metastases. Although surgical resection is the first choice worldwide, at this point an effective approach for the treatment of patients with liver metastasis and cancer recurrence postoperation has not yet been found. The aim of this study is to investigate the role of the allogeneic dendritomas from fusion of DCs and metastatic colon cancer cells in the activation of anti-tumor immunity against colorectal cancer liver metastases.

MATERIAL AND METHODS

Hybrids were generated by fused allogeneic human peripheral blood dendritic cells with metastatic colon cancer SW620 cells using 50% polyethylene glycol (PEG). Induction of immune responses was assessed by ex vivo ELISPOT assays. A murine model of CRC liver metastasis was used by intrasplenic injection. The validity of the vaccine was observed by Vaccination CRC liver metastasis murine model with DC/tumor hybrids.

RESULTS

The hybrids highly express the major molecules of DCs and tumor cells. The number of hybrids pulsed CTL secreting IFN-gamma was significantly higher when compared to the DC controls (p < 0.01). In a therapeutic setting mice vaccinated with in vitro cultured hybrids produced strong cellular immune responses and significant inhibition of tumor growth, compared to sham vaccinated controls.

CONCLUSIONS

Vaccination with hybrids can induces strong cellular responses and significant protection from challenge in SCID mouse metastatic CRC model.

The evolving role of dendritic cells in cancer therapy

IMPORTANCE OF THE FIELD

Dendritic cells (DC) are a clear choice for use in cancer immunotherapy, and much research has focused on generating DC for clinical use. Although DC therapy has been successful in inducing specific anti-tumour immune responses, these have rarely translated into clinical efficacy.

AREAS COVERED IN THIS REVIEW

We examine some of the components of generating DC for therapy, including their culture, antigen loading and delivery, and discuss why DC therapy has not yet delivered substantial clinical benefit. We also examine more novel approaches, such as the potential for combination DC-based immunomodulatory strategies.

WHAT THE READER WILL GAIN

Given the highly immunosuppressive tumour environment, many of the approaches to DC vaccination are unlikely to result in effective therapy, as even successfully primed T cells may fail to infiltrate tumours or be anergized after entry. Broader approaches against multiple tumour-associated antigens in the context of overcoming tumour immune suppression are likely to prove more successful. The combination of oncolytic viral therapy with DC vaccines may promote an inflammatory tumour environment, inducing optimal DC activation, T cell priming and effective therapy.

TAKE HOME MESSAGE

Evolving DC-based therapeutic strategies addressing multiple components of tumour-immune system interactions may yield substantial benefits for patients.

Photodynamic therapy induces interleukin secretion from dendritic cells

Dendritic cells (DC) pulsed with tumor-derived peptides, proteins, genes, or lysates have been studied as therapeutic cancer vaccines. However, the overall therapeutic efficacy of this approach has been limited, indicating a need to either enhance its potency or combine it with other treatment modalities. Photodynamic therapy (PDT) process consists of injecting a photosensitizer, which selectively accumulates at the lesion site, followed by local illumination of the tumor with a laser of the appropriate wavelength to activate the specific drug. PDT has the potential to create an environment at the tumor site that favors both tumor antigen loading and activation of DCs, key requirements for induction of antitumor immunity. Here, we report that PDT can induce IL-1 and IL-6 and reduce TNF-alpha expression from DCs. This finding has potentially broad clinical implications since these changes are mechanistically involved in the observed effects of PDT on host immune responses. Not all tumors are amenable to PDT, either because of size or location, and one could conceive of an adjuvant use for PDT vaccines in conjunction with other cancer modalities that do not enhance the host antitumor immune response.

Dendritic cells transduced with Rsf-1/HBXAP gene generate specific cytotoxic T lymphocytes against ovarian cancer in vitro

Recently, some studies have indicated that Rsf-1/HBXAP plays a role in chromatin remodeling and transcriptional regulation that may contribute to tumorigenesis in ovarian cancer. The present study demonstrates that using dendritic cells (DCs) from human cord blood CD34(+) cells transduced with Rsf-1/HBXAP DNA plasmids by nucleofection generate specific cytotoxic T lymphocytes (CTL) against ovarian cancer in vitro. After transfection, DCs were analyzed for Rsf-1/HBXAP mRNA expression by RT-PCR and protein expression by Western blot. Then the DC phenotypes, T-cell stimulatory capacity, endocytic activity and migration capacity were explored by flow cytometry analysis, allogeneic mixed lymphocyte reaction, endocytosis and transwell chemotaxis assay, respectively. After transfection, Rsf-1/HBXAP expression was detected at mRNA and protein levels. Allogeneic T-cell proliferation induced by transfected DCs was obviously higher than non-transfected DCs, but the endocytosis capacity and migratory ability were not different. Rsf-1/HBXAP gene-transduced DCs could induce antigen-specific CTL and generate a very potent cytotoxicity to OVCAR3 cells. These data suggest that Rsf-1/HBXAP gene-transduced DCs may be a potential adjuvant immunotherapy for ovarian cancer in clinical applications.

Overexpression of sonic Hedgehog in the lung mimics the effect of lung injury and compensatory lung growth on pulmonary Sca-1 and CD34 positive cells

Cells localized in the bronchioalveolar duct junction of the murine lung have been identified as potential bronchioalveolar stem cells. Based on the surface marker expression, two main phenotypes have been proposed: Sca-1(+), CD34(+), CD45(-), Pecam(-) and Sca-1(low), CD34(-) CD45(-), Pecam(-) cells. An increase in the number of Sca-1(+), CD34(+) CD45(-), Pecam(-) cells and activation of the sonic hedgehog (Shh) pathway was observed following unilateral pneumonectomy and naphthalene-induced airway injury. Overexpression of Shh in the respiratory tract also resulted in an increase of this cell population. Syngeneic transplantation of beta-galactosidase-expressing bone marrow cells demonstrated that the increase of Sca-1(+), CD34(+), CD45(-), Pecam(-) cells in the lung was a result of local proliferation. Intratracheal administration of purified Shh-stimulated Sca-1(+), CD45(-), Pecam(-) cells coexpressing CD34 to syngeneic mice following pneumonectomy resulted in engraftment of these cells predominantly in the airways for up to 3 months, whereas Sca-1(-), CD45(-), Pecam(-) cells did not engraft. This study suggests that local Sca-1(+), CD34(+), CD45(-), Pecam(-) cells are stimulated during compensatory lung growth, following airway injury and overexpression of Shh and have some potential to engraft in the airways, without showing clonal properties in vivo.

Dendritic cell migration limits the duration of CD8+ T-cell priming to peripheral viral antigen

CD8(+) T cells (T(CD8(+))) play a crucial role in immunity to viruses. Antiviral T(CD8(+)) are initially activated by recognition of major histocompatibility complex (MHC) class I-peptide complexes on the surface of professional antigen-presenting cells (pAPC). Migration of pAPC from the site of infection to secondary lymphoid organs is likely required during a natural infection. Migrating pAPC can be directly infected with virus or may internalize antigen derived from virus-infected cells. The use of experimental virus infections to assess the requirement for pAPC migration in initiation of T(CD8(+)) responses has proven difficult to interpret because injected virus can readily drain to secondary lymphoid organs without the need for cell-mediated transport. To overcome this ambiguity, we examined the generation of antigen-specific T(CD8(+)) after immunization with recombinant adenoviruses that express antigen driven by skin-specific or ubiquitous promoters. We show that the induction of T(CD8(+)) in response to tissue-targeted antigen is less efficient than the response to ubiquitously expressed antigen and that the resulting T(CD8(+)) fail to clear all target cells pulsed with the antigenic peptide. This failure to prime a fully functional T(CD8(+)) response results from a reduced period of priming to peripherally expressed antigen versus ubiquitously expressed antigen and correlated with a brief burst of pAPC migration from the skin, a requirement for induction of the response to peripheral antigen. These results indicate that a reduced duration of pAPC migration after virus infection likely reduces the amplitude of the T(CD8(+)) response, allowing persistence of the peripheral virus.

Antitumor effects of murine bone marrow-derived dendritic cells infected with xenogeneic livin alpha recombinant adenoviral vectors against Lewis lung carcinoma

Transduction with recombinant, replication-defective adenoviral (rAd) vectors encoding a transgene is an efficient method for gene transfer into dendritic cells (DCs). Livin is a member of the inhibitor of apoptosis protein family. Lung cancer and many other tumors express livin at high levels; whereas, normal fully differentiated cells generally do not. Therefore, livin represents a tumor-specific target for cancer vaccine therapy. Self proteins like livin may not stimulate potent antitumor immune responses due to central immunologic tolerance. Small variations in protein sequence that may exist between homologous proteins of different species can break tolerance to the native antigen. To study immunogenicity of a xenogeneic livin protein, we constructed an recombinant adenoviral vectors containing the human livin alpha genes (rAd-hlivin alpha) and vaccinated C57BL/6 mice with mouse bone marrow dendritic cells (BMDCs) transfected with rAd-hlivin alpha gave rise to potent livin-specific cytotoxic T lymphocyte (CTL) capable of lysing Lewis lung carcinoma (LLC) cells. Moreover, vaccination of mice with rAd-hlivin alpha-transduced DCs (rAd-hlivin alpha DCs) induced a potent protective and therapeutic anti-tumor immunity to LLC in a subcutaneous model along with prolonged survival compared to mice vaccinated with control recombinant adenovirus-transduced DCs(rAd-c DCs) or DCs alone. Therefore, xenogeneic differences between human and murine sequences might be exploited to develop immunogenic tumor vaccines.

Indirect recruitment of a CD40 signaling pathway in dendritic cells by B7-DC cross-linking antibody modulates T cell functions

The human IgM B7-DC XAb protects mice from tumors in both therapeutic and prophylactic settings. Its mechanism of action is mediated by its binding to B7-DC/PD-L2 molecules on the surface of dendritic cells (DCs) to induce a multimolecular cap and subsequent activation of signaling cascades that determine a unique combination of DC phenotypes. One such phenotype, the B7-DC XAb-induced antigen accumulation in mTLR-matured DCs, has been linked to signaling through TREM-2, but the signals required for other DC phenotypes critical for the therapeutic effects in animal models remain unclear. Here, FRET and co-immunoprecipitation studies show that CD40 is recruited to the multi-molecular complex by B7-DC XAb. Signals emanating from CD40 are important, as CD40^−/− DCs treated with B7-DC XAb (DC^XAb) activated DAP12, but failed to activate NFκB, and were not protected from cell death upon cytokine withdrawal or treatment with Vitamin D₃. CD40^−/− DC^XAb also failed to secrete IL-6 and were unable to support the conversion of T regulatory cells into IL-17+ effector T cells in vitro. Importantly, the expression of CD40 was required for the overall ability of B7-DC XAb to induce anti-tumor CTL, to provide protection from a number of tumor types, and for DC^XAb to be effective anti-tumor vaccines in vivo. These results indicate that B7-DC XAb modulation of DC phenotypes is through its ability to indirectly recruit common signaling molecules and elements of their endogenous signaling pathways through targeted binding to a cell-specific surface determinant.

alpha-Galactosylceramide-loaded, antigen-expressing B cells prime a wide spectrum of antitumor immunity

Most of the current tumor vaccines successfully elicit strong protection against tumor but offer little therapeutic effect against existing tumors, highlighting the need for a more effective vaccine strategy. Vaccination with tumor antigen-presenting cells can induce antitumor immune responses. We have previously shown that NKT-licensed B cells prime cytotoxic T lymphocytes (CTLs) with epitope peptide and generate prophylactic/therapeutic antitumor effects. To extend our B cell vaccine approach to the whole antigen, and to overcome the MHC restriction, we used a nonreplicating adenovirus to transduce B cells with antigenic gene. Primary B cells transduced with an adenovirus-encoding truncated Her-2/neu (AdHM) efficiently expressed Her-2/neu. Compared with the moderate antitumor activity induced by vaccination with adenovirus-transduced B cells (B/AdHM), vaccination with alpha-galactosylceramide-loaded B/AdHM (B/AdHM/alpha GalCer) induced significantly stronger antitumor immunity, especially in the tumor-bearing mice. The depletion study showed that CD4(+), CD8(+) and NK cells were all necessary for the therapeutic immunity. Confirming the results of the depletion study, B/AdHM/alpha GalCer vaccination induced cytotoxic NK cell responses but B/AdHM did not. Vaccination with B/AdHM/alpha GalCer generated Her-2/neu-specific antibodies more efficiently than B/AdHM immunization. More importantly, B/AdHM/alpha GalCer could prime Her-2/neu-specific cytotoxic T cells more efficiently and durably than B/AdHM. CD4(+) cells appeared to be necessary for the induction of antibody and CTL responses. Our results demonstrate that, with the help of NKT cells, antigen-transduced B cells efficiently induce innate immunity as well as a wide range of adaptive immunity against the tumor, suggesting that they could be used to develop a novel cellular vaccine.

Phase I/II study of vaccination with electrofused allogeneic dendritic cells/autologous tumor-derived cells in patients with stage IV renal cell carcinoma

In the present study, we assessed the feasibility, toxicity, immunologic response, and clinical efficacy of vaccination with allogeneic dendritic cell (DC)/tumor fusions in patients with metastatic renal cell carcinoma (RCC). Patients with stage IV RCC with accessible tumor lesions or independent therapeutic indications for nephrectomy were eligible for enrollment. Tumors were processed into single cell suspensions and cryopreserved. DCs were generated from adherent peripheral blood mononuclear cells isolated from normal volunteers and cultured with granulocyte macrophage colony-stimulating factor, interleukin-4, and tumor necrosis factor-alpha. DCs were fused to patient derived RCC with serial electrical pulses. Patients received up to 3 vaccinations at a fixed dose of 4x10(7) to 1x10(8) cells administered at 6-week intervals. Twenty-four patients underwent vaccination. Twenty-one and 20 patients were evaluable for immunologic and clinical response, respectively. DCs demonstrated a characteristic phenotype with prominent expression of HLA class II and costimulatory molecules. A mean fusion efficiency of 20% was observed, determined by the percent of cells coexpressing DC and tumor antigens. No evidence of significant treatment related toxicity or auto-immunity was observed. Vaccination resulted in antitumor immune responses in 10/21 evaluable patients as manifested by an increase in CD4 and/or CD8 T-cell expression of interferon-gamma after ex vivo exposure to tumor lysate. Two patients demonstrated a partial clinical response by Response Evaluation Criteria in Solid Tumors criteria and 8 patients had stabilization of their disease. Vaccination of patients with RCC with allogeneic DC/tumor fusions was feasible, well tolerated, and resulted in immunologic and clinical responses in a subset of patients.

Human dendritic cells transfected with allergen-DNA stimulate specific immunoglobulin G4 but not specific immunoglobulin E production of autologous B cells from atopic individuals in vitro

Atopic/allergic diseases are characterized by T helper 2 (Th2)-dominated immune responses resulting in immunoglobulin E (IgE) production. DNA-based immunotherapies have been shown to shift the immune response towards Th1 in animal models. In further studies we showed that human dendritic cells (DC) transfected with allergen-DNA are able to stimulate autologous CD4(+) T cells from atopic individuals to produce Th1 instead of Th2 cytokines and to activate interferon-gamma (IFN-gamma)-producing CD8(+) T cells. The aim of this study was to analyse whether DC transfected with allergen-DNA are also able to influence immunoglobulin production of B cells from atopic donors. For this purpose, human monocyte-derived DC from grass-pollen allergic donors were transfected with an adenovirus encoding the allergen Phleum pratense 1 and cocultured with B cells, autologous CD4(+) T cells, and CD40 ligand-transfected L-cells. B cells receiving help from CD4(+) T cells stimulated with allergen-transfected dendritic cells produced more allergen-specific IgG4 compared to stimulation with allergen protein pulsed DC or medium, while total IgG4 production was not affected. In contrast, specific IgE production was not enhanced by stimulation with allergen-DNA transfected DC compared to medium and inhibited compared to allergen protein-pulsed DC with similar effects on total IgE production in vitro. Allergen-DNA transfected dendritic cells are able to direct the human allergic immune response from Th2-dominance towards Th1 and Tc1 also resulting in decreased IgE and increased IgG4 production.

Protective immunity to pseudomonas aeruginosa induced with a capsid-modified adenovirus expressing P. aeruginosa OprF

This study focuses on the development of a new clinical vaccine candidate (AdOprF.RGD.Epi8) against Pseudomonas aeruginosa using an E1(-) E3(-) adenovirus (Ad) vector expressing OprF (AdOprF.RGD.Epi8) and modifications of the Ad genome providing two capsid changes: (i) modification of the Ad hexon gene to incorporate an immune-dominant OprF epitope (Epi8) into loop 1 of the hexon, enabling repeat administration to boost the anti-OprF immune response, and (ii) modification of the fiber gene to incorporate an integrin-binding RGD sequence to enhance gene delivery to antigen-presenting cells. Western analysis confirmed that AdOprF.RGD.Epi8 expresses OprF, contains Epi8 in the hexon protein, and enhances gene transfer to dendritic cells compared to AdOprF, a comparable Ad vector expressing OprF with an unmodified capsid. Intramuscular immunization of C57BL/6 mice with AdOprF.RGD.Epi8 resulted in the generation of anti-OprF antibodies at comparable levels to those induced following immunization with AdOprF, but immunization with AdOprF.RGD.Epi8 was associated with increased CD4 and CD8 gamma interferon T-cell responses against OprF as well as increased survival against lethal pulmonary challenge with agar-encapsulated P. aeruginosa. Importantly, repeat administration of AdOprF.RGD.Epi8 resulted in boosting of the humoral anti-OprF response as well as increased protection, whereas no boosting could be achieved with repeat administration of AdOprF. This suggests that the capsid-modified AdOprF.RGD.Epi8 vector is a more effective immunogen compared to a comparable wild-type Ad capsid, making it a good candidate for an anti-P. aeruginosa vaccine.

Immune cell recruitment and cell-based system for cancer therapy

Immune cells, such as cytotoxic T lymphocytes, natural killer cells, B cells, and dendritic cells, have a central role in cancer immunotherapy. Conventional studies of cancer immunotherapy have focused mainly on the search for an efficient means to prime/activate tumor-associated antigen-specific immunity. A systematic understanding of the molecular basis of the trafficking and biodistribution of immune cells, however, is important for the development of more efficacious cancer immunotherapies. It is well established that the basis and premise of immunotherapy is the accumulation of effective immune cells in tumor tissues. Therefore, it is crucial to control the distribution of immune cells to optimize cancer immunotherapy. Recent characterization of various chemokines and chemokine receptors in the immune system has increased our knowledge of the regulatory mechanisms of the immune response and tolerance based on immune cell localization. Here, we review the immune cell recruitment and cell-based systems that can potentially control the systemic pharmacokinetics of immune cells and, in particular, focus on cell migrating molecules, i.e., chemokines, and their receptors, and their use in cancer immunotherapy.

Alphaviral vector-transduced dendritic cells are successful therapeutic vaccines against neu-overexpressing tumors in wild-type mice

While dendritic cell (DC) vaccines can protect hosts from tumor challenge, their ability to effectively inhibit the growth of established tumors remains indeterminate. Previously, we have shown that human DCs transduced with Venezuelan equine encephalitis virus replicon particles (VRPs) were potent stimulators of antigen-specific T cells in vitro. Therefore, we investigated the ability of VRP-transduced DCs (VRP-DCs) to induce therapeutic immunity in vivo against tumors overexpressing the neu oncoprotein. Transduction of murine DCs with VRPs resulted in high-level transgene expression, DC maturation and secretion of proinflammatory cytokines. Vaccination with VRP-DCs expressing a truncated neu oncoprotein induced robust neu-specific CD8(+) T cell and anti-neu IgG responses. Furthermore, a single vaccination with VRP-DCs induced the regression of large established tumors in wild-type mice. Interestingly, depletion of CD4(+), but not CD8(+), T cells completely abrogated inhibition of tumor growth following vaccination. Taken together, our results demonstrate that VRP-DC vaccines induce potent immunity against established tumors, and emphasize the importance of the generation of both CD4(+) T cell and B cell responses for efficient tumor inhibition. These findings provide the rationale for future evaluation of VRP-DC vaccines in the clinical setting.

Epitopes expressed in different adenovirus capsid proteins induce different levels of epitope-specific immunity

On the basis of the concept that the capsid proteins of adenovirus (Ad) gene transfer vectors can be genetically manipulated to enhance the immunogenicity of Ad-based vaccines, the present study compared the antiantigen immunogenicity of Ad vectors with a common epitope of the hemagglutinin (HA) protein of the influenza A virus incorporated into the outer Ad capsid protein hexon, penton base, fiber knob, or protein IX. Incorporation of the same epitope into the different capsid proteins provided insights into the correlation between epitope position and antiepitope immunity. Following immunization of three different strains of mice (C57BL/6, BALB/c, and CBA) with either an equal number of Ad particles (resulting in a different total HA copy number) or different Ad particle numbers (to achieve the same HA copy number), the highest primary (immunoglobulin M [IgM]) and secondary (IgG) anti-HA humoral and cellular CD4 gamma interferon and interleukin-4 responses against HA were always achieved with the Ad vector carrying the HA epitope in fiber knob. These observations suggest that the immune response against an epitope inserted into Ad capsid proteins is not necessarily dependent on the capsid protein number and imply that the choice of incorporation site in Ad capsid proteins in their use as vaccines needs to be compared in vivo.

Tumor suppressive efficacy through augmentation of tumor-infiltrating immune cells by intratumoral injection of chemokine-expressing adenoviral vector

Our goal in the present study was to evaluate antitumor effects and frequency of tumor-infiltrating immune cells upon intratumoral injection of RGD fiber-mutant adenoviral vector (AdRGD) encoding the chemokines CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1, and CX3CL1. Among eight kinds of chemokine-expressing AdRGDs, AdRGD-CCL19 injection most efficiently induced infiltration of T cells into established B16BL6 tumor parenchyma, whereas most of these T cells were perforin-negative in immunohistochemical analysis. Additionally, the growth of AdRGD-CCL19-injected tumors decreased only slightly as well as that of other tumors treated with each chemokine-expressing AdRGD, which indicated that accumulation of naive T cells in tumor tissue does not effectively damage the tumor cells. Tumor-bearing mice, in which B16BL6-specific T cells were elicited by dendritic cell-based immunization, demonstrated that intratumoral injection of AdRGD-CCL17, -CCL22, or -CCL27 could considerably suppress tumor growth and attract activated T cells. On the other hand, AdRGD-CCL19-injection in the immunized mice showed slight increase of tumor-infiltrating T cells compared to treatment using control vector. Collectively, although AdRGD-mediated chemokine gene transduction into established tumors would be very useful for augmentation of tumor-infiltrating immune cells, a combinational treatment that can systemically induce tumor-specific effector T cells is necessary for satisfactory antitumor efficacy.

Interaction of Pneumocystis carinii with dendritic cells and resulting host responses to P. carinii

To assess the interaction of Pneumocystis carinii with dendritic cells (DCs), and the consequences of the response of the host immune system to P. carinii antigens when DC are pulsed with P. carinii, murine DC were pulsed with P. carinii, and the resultant P. carinii host responses assessed in vitro and in vivo. P. carinii interacted with murine bone marrow-derived DC in vitro in part via mannose receptors. DC pulsed with P. carinii did not demonstrate increased expression of the cell surface markers MHC II, CD40, CD54, CD80 (B7.1), and CD86 (B7.2). The release of interleukin (IL)-4 was increased, but there was no increase in the release of interleukin (IL)-12p40, IL-10, tumor necrosis factor-alpha, IL-6, and nitrite compared with naive DC. In vivo administration of DC pulsed with P. carinii induced a P. carinii-specific response, generating CD4+ cells that proliferated and released IL-4, but not interferon-gamma, in response to P. carinii-pulsed DC in vitro. In vivo administration of DC pulsed with P. carinii also induced P. carinii-specific immunoglobulin (Ig)G1, IgG2a, and IgG2b, but not IgG3, antibodies in serum, and lung lavage fluid. Finally, CD4+ depleted mice immunized with DC pulsed with P. carinii demonstrated suppression of lung growth of P. carinii after intratracheal challenge with P. carinii at 3 and 16 weeks after immunization. These observations provide insight into DC-P. carinii interactions, and support the concept that a vaccine that includes DC pulsed with P. carinii can mount a humoral and T helper 2-type cellular response to P. carinii sufficient to suppress the growth of P. carinii in the lung.

Mannan-modified adenovirus as a vaccine to induce antitumor immunity

Tumor vaccine is a useful strategy for cancer therapy. However, priming of the immune system requires the relevant antigen to be presented by antigen-presenting cells (APCs). Here, we employed telomerase reverse transcriptase as a model antigen to explore the feasibility of using mannan-modified adenovirus as a tumor vaccine. We found that tumor immunogene therapy with the vaccine was effective at protective antitumor immunity in mice. The antigen-specific cytotoxic T lymphocytes were found in in vitro cytotoxicity assay. The elevation of the killing activity could be abrogated by anti-CD8 or anti-major histocompatibility complex-I antibodies. Adoptive transfer of purified CD8+ cells, and CD4+ cells to a less extent, was effective at antitumor activity. In vivo antitumor activity could be abrogated by depleting CD4+ T lymphocytes. A possible explanation for the antitumor effects may be the antigen was transferred to APCs in the presence of mannan. These observations provide insights into the design of novel vaccine strategies and might be important for the future application of antigens identified in other diseases.

Cotransduction of CCL27 gene can improve the efficacy and safety of IL-12 gene therapy for cancer

Interleukin-12 (IL-12) is a potent antitumoral cytokine, but high doses are toxic. Herein, we demonstrate that combinational transduction of IL-12 and CC-chemokine ligand-27 (CCL27) genes into pre-existing murine OV-HM ovarian carcinoma and Meth-A fibrosarcoma, by using RGD fiber-mutant adenoviral vectors, could induce tumor regression and relieve systemic side effects more effectively than either treatment alone. The antitumor activity of the IL-12 and CCL27 combination treatment was T-cell-dependent, and development of long-term specific immunity was confirmed in rechallenge experiments. Immunohistochemical analysis of tumors transduced with CCL27 gene alone or cotransduced with IL-12 and CCL27 genes showed significant increases in numbers of infiltrating CD3(+) T cells, which included both CD4(+) and CD8(+) cells. Additionally, cotransduction with IL-12 and CCL27 genes could more efficiently activate tumor-infiltrating immune cells than transduction with CCL27 alone, as determined by the frequency of perforin-positive cells and expression levels of IFN-gamma. Furthermore, mice treated with the IL-12 and CCL27 combination compared with those treated with IL-12 alone showed milder pathological changes, for example, lymphocyte infiltration and extramedullary hematopoiesis, in lung, liver and spleen. Our data provide evidence that combinational in vivo transduction with IL-12 and CCL27 genes is a promising approach for the development of cancer immunogene therapy that can simultaneously recruit and activate tumor-infiltrating immune cells.

Dendritic cell vaccination in patients with malignant gliomas: current status and future directions

OBJECTIVE

Despite recent advances in neurosurgical resection techniques, radiation therapy, and chemotherapy, malignant gliomas continue to have a dismal prognosis because relapses are unavoidable.

METHODS

Dendritic cell vaccination has recently emerged as a promising type of active immunotherapy that aims to induce rather than transfer specific antitumor immune responses in patients. Active immunotherapy is the only type of immunotherapy able to induce immunological memory.

RESULTS

Although an increasing number of small clinical trials show safety, feasibility, and immunological and clinical responses, this technology requires further clarification of some critical basic and clinical issues before its presumed place in the treatment of malignant gliomas can be specified. This article addresses the basic and clinical pitfalls that, more than with conventional therapies, may interfere with the potential benefits of this approach.

CONCLUSION

Considering the particular mechanisms involved in the immune modulation of tumor biology using dendritic cell-based vaccinations, the authors summarize the arguments in favor of a further, appropriate assessment of this technology.