Comparison of recombinant adenovirus and synthetic peptide for DC-based melanoma vaccination

Cationic nanoparticles enhance T cell tumor infiltration and antitumor immune responses to a melanoma vaccine

In clinical settings, cancer vaccines as monotherapies have displayed limited success compared to other cancer immunotherapeutic treatments. Nanoscale formulations have the ability to increase the efficacy of cancer vaccines by combatting the immunosuppressive nature of the tumor microenvironment. Here, we have synthesized a previously unexplored cationic polymeric nanoparticle formulation using polyamidoamine dendrimers and poly(d,l-lactic-co-glycolic acid) that demonstrate adjuvant properties in vivo. Tumor-challenged mice vaccinated with an adenovirus-based cancer vaccine [encoding tumor-associated antigen (TAA)] and subsequently treated with this nanoparticulate formulation showed significant increases in TAA-specific T cells in the peripheral blood, reduced tumor burden, protection against tumor rechallenge, and a significant increase in median survival. An investigation into cell-based pathways suggests that administration of the nanoformulation at the site of the developing tumor may have created an inflammatory environment that attracted activated TAA-specific CD8+ T cells to the vicinity of the tumor, thus enhancing the efficacy of the vaccine.

ICOSL-augmented adenoviral-based vaccination induces a bipolar Th17/Th1 T cell response against unglycosylated MUC1 antigen

Cellular immunity established via immunotherapy holds the potential to eliminate solid tumors. Yet, cancer vaccines have failed to induce tumor-reactive T cells of sufficient quality to control disease. The inducible T cell costimulator (ICOS) pathway has been implicated in both the selective induction of immunity over tolerance as well as licensing of IL-17-polarized cellular immunity. Herein, we evaluated the ability of ICOS ligand (ICOSL) to augment the immunogenicity of adenoviral-based vaccination targeting the unglycosylated MUC1 peptide antigen. Vaccination disrupted immunotolerance in a transgenic mouse model recognizing human MUC1 as a self-antigen, inducing robust MUC1-specific immunity. Augmenting vaccination with ICOSL induced a bipolar Th17/Th1 effector profile, marked by increased MUC1-specific IL-17A production and RORγt expression in CD4⁺ but not CD8⁺ T cells which predominantly expressed IFNγ/IL-2 and T-bet. The polarization and maintenance of Th17 cells established following ICOSL augmented vaccination was highly durable, with elevated IL-17A and RORγt levels detected in CD4⁺ T cells up to 10 months after initial immunization. Furthermore, provision of ICOSL significantly enhanced MUC1-specific IgG antibody in response to immunization. ICOSL signaling dramatically influenced CD4⁺ T cell phenotype, altering gene expression of transcription factors and regulators of effector function following immunization. Interestingly, ICOSL augmentation failed to alter the transcriptional profile of CD8⁺ T cells following immunization, affecting the magnitude, but not distribution, of gene expression. Collectively, ICOSL supports the induction of durable, antigen-specific Th17/Th1-mediated immunity in vivo, establishing a vaccination platform to enhance CD4⁺ T cell-mediated antitumor immunity and providing a crucial component of an effective cancer vaccine.

Cancer immunotherapy using virally transduced dendritic cells: animal studies and human clinical trials

The immune system uses a process known as 'immunosurveillance' to help prevent the outgrowth of tumors. In cancer immunotherapy, a major goal is for immunity against tumor-associated antigens to be generated or strengthened in patients. To achieve this goal, several approaches have been tested, including the use of highly potent antigen-presenting cells called dendritic cells (DCs), which can activate T cells efficiently. Presentation of peptides derived from tumor antigens on the surface of DCs can stimulate strong antitumor immunity. Using recombinant viral vectors encoding tumor-associated antigens, DCs can be engineered efficiently to express sustained levels of tumor-antigen peptides. This review discusses the effectiveness of virally transduced DCs in treating tumors and generating antigen-specific T-cell responses. It covers mouse and nonhuman primate studies, preclinical in vitro human cell experiments and clinical trials.

Biolistic DNA vaccination against melanoma

We describe here the use of particle-mediated gene transfer for the induction of immune responses against melanoma antigens in murine tumor models using the melanocyte differentiation antigen tyrosinase-related protein 2 (TRP2) as an antigen in a murine B16 melanoma model. We have utilized marker genes such as β-galactosidase (βgal) and EGFP, which can be readily detected, as control antigens to establish the gene delivery and to detect antigen-specific humoral and cellular immune responses. After biolistic DNA vaccination with plasmids encoding the TRP2 gene we observed the induction of TRP2-specific T-cells and antibodies associated with vitiligo-like fur depigmentation and tumor immunity against B16 melanoma cells. Here we describe the preparation of cartridges with DNA-coated gold beads and the in vivo gene transfer into skin using the Helios Gene Gun system. We also describe protocols for the measurement of humoral and cellular immune responses against the melanocyte differentiation antigen TRP2. These protocols can subsequently be adapted to other antigens.

Chapter six--Adenovirus-based immunotherapy of cancer: promises to keep

Progress in vector design and an increased knowledge of mechanisms underlying tumor-induced immune suppression have led to a new and promising generation of Adenovirus (Ad)-based immunotherapies, which are discussed in this review. As vaccine vehicles Ad vectors (AdVs) have been clinically evaluated and proven safe, but a major limitation of the commonly used Ad5 serotype is neutralization by preexistent or rapidly induced immune responses. Genetic modifications in the Ad capsid can reduce intrinsic immunogenicity and facilitate escape from antibody-mediated neutralization. Further modification of the Ad hexon and fiber allows for liver and scavenger detargeting and selective targeting of, for example, dendritic cells. These next-generation Ad vaccines with enhanced efficacy are now becoming available for testing as tumor vaccines. In addition, AdVs encoding immune-modulating products may be used to convert the tumor microenvironment from immune-suppressive and proinvasive to proinflammatory, thus facilitating cell-mediated effector functions that can keep tumor growth and invasion in check. Oncolytic AdVs, that selectively replicate in tumor cells and induce an immunogenic form of cell death, can also be armed with immune-activating transgenes to amplify primed antitumor immune responses. These novel immunotherapy strategies, employing highly efficacious AdVs in optimized configurations, show great promise and warrant clinical exploration.

Potent antitumor immunity generated by a CD40-targeted adenoviral vaccine

In situ delivery of tumor-associated antigen (TAA) genes into dendritic cells (DC) has great potential as a generally applicable tumor vaccination approach. Although adenoviruses (Ad) are an attractive vaccine vehicle in this regard, Ad-mediated transduction of DCs is hampered by the lack of expression of the Ad receptor CAR on the DC surface. DC activation also requires interaction of CD40 with its ligand CD40L to generate protective T-cell-mediated tumor immunity. Therefore, to create a strategy to target Ads to DCs in vivo, we constructed a bispecific adaptor molecule with the CAR ectodomain linked to the CD40L extracellular domain via a trimerization motif (CFm40L). By targeting Ad to CD40 with the use of CFm40L, we enhanced both transduction and maturation of cultured bone marrow-derived DCs. Moreover, we improved transduction efficiency of DCs in lymph node and splenic cell suspensions in vitro and in skin and vaccination site-draining lymph nodes in vivo. Furthermore, CD40 targeting improved the induction of specific CD8(+) T cells along with therapeutic efficacy in a mouse model of melanoma. Taken together, our findings support the use of CD40-targeted Ad vectors encoding full-length TAA for in vivo targeting of DCs and high-efficacy induction of antitumor immunity.

Monitoring of in vivo function of superparamagnetic iron oxide labelled murine dendritic cells during anti-tumour vaccination

Dendritic cells (DCs) generated in vitro to present tumour antigens have been injected in cancer patients to boost in vivo anti-tumour immune responses. This approach to cancer immunotherapy has had limited success. For anti-tumour therapy, delivery and subsequent migration of DCs to lymph nodes leading to effective stimulation of effector T cells is thought to be essential. The ability to non-invasively monitor the fate of adoptively transferred DCs in vivo using magnetic resonance imaging (MRI) is an important clinical tool to correlate their in vivo behavior with response to treatment. Previous reports of superparamagnetic iron oxides (SPIOs) labelling of different cell types, including DCs, have indicated varying detrimental effects on cell viability, migration, differentiation and immune function. Here we describe an optimised labelling procedure using a short incubation time and low concentration of clinically used SPIO Endorem to successfully track murine DC migration in vivo using MRI in a mouse tumour model. First, intracellular labelling of bone marrow derived DCs was monitored in vitro using electron microscopy and MRI relaxometry. Second, the in vitro characterisation of SPIO labelled DCs demonstrated that viability, phenotype and functions were comparable to unlabelled DCs. Third, ex vivo SPIO labelled DCs, when injected subcutaneously, allowed for the longitudinal monitoring by MR imaging of their migration in vivo. Fourth, the SPIO DCs induced the proliferation of adoptively transferred CD4(+) T cells but, most importantly, they primed cytotoxic CD8(+) T cell responses to protect against a B16-Ova tumour challenge. Finally, using anatomical information from the MR images, the immigration of DCs was confirmed by the increase in lymph node size post-DC injection. These results demonstrate that the SPIO labelling protocol developed in this study is not detrimental for DC function in vitro and in vivo has potential clinical application in monitoring therapeutic DCs in patients with cancer.

Delivery route, MyD88 signaling and cross-priming events determine the anti-tumor efficacy of an adenovirus based melanoma vaccine

Adenovirus (Ad)-based vaccines are considered for cancer immunotherapy, yet, detailed knowledge on their mechanism of action and optimal delivery route for anti-tumor efficacy is lacking. Here, we compared the anti-tumor efficacy of an Ad-based melanoma vaccine after intradermal, intravenous, intranasal or intraperitoneal delivery in the B16F10 melanoma model. The intradermal route induced superior systemic anti-melanoma immunity which was MyD88 signaling-dependent. Predominant transduction of non-professional antigen-presenting cells at the dermal vaccination sites and draining lymph nodes, suggested a role for cross-presentation, which was confirmed in vitro. We conclude that the dermis provides an optimal route of entry for Ad-based vaccines for high-efficacy systemic anti-tumor immunization and that this immunization likely involves cross-priming events in the draining lymph nodes.

Dendritic cell-directed lentivector vaccine induces antigen-specific immune responses against murine melanoma

Lentivectors are potential vaccine delivery vehicles because they can efficiently transduce a variety of non-dividing cells, including antigen-presenting cells, and do not cause expression of extra viral proteins. To improve safety while retaining efficiency, a dendritic cell (DC)-specific lentivector was constructed by pseudotyping the vector with an engineered viral glycoprotein derived from Sindbis virus. We assessed the level of anti-tumor immunity conferred by this engineered lentivector encoding the melanoma antigen gp100 in a mouse model. Footpad injection of the engineered lentivectors results in the best antigen-specific immune response as compared with subcutaneous and intraperitoneal injections. A single prime vaccination of the engineered lentivectors can elicit a high frequency (up to 10%) of gp100-specific CD8(+) T cells in peripheral blood 3 weeks after the vaccination and this response will be maintained at around 5% for up to 8 weeks. We found that these engineered lentivectors elicited relatively low levels of anti-vector neutralizing antibody responses. Importantly, direct injection of this engineered lentivector inhibited the growth of aggressive B16 murine melanoma. These data suggest that DC-specific lentivectors can be a novel and alternative vaccine carrier with the potential to deliver effective anti-tumor immunity for cancer immunotherapy.

Recombinant vesicular stomatitis virus transduction of dendritic cells enhances their ability to prime innate and adaptive antitumor immunity

Dendritic cell (DC)-based vaccines are a promising strategy for tumor immunotherapy due to their ability to activate both antigen-specific T-cell immunity and innate immune effector components, including natural killer (NK) cells. However, the optimal mode of antigen delivery and DC activation remains to be determined. Using M protein mutant vesicular stomatitis virus (DeltaM51-VSV) as a gene-delivery vector, we demonstrate that a high level of transgene expression could be achieved in approximately 70% of DCs without affecting cell viability. Furthermore, DeltaM51-VSV infection activated DCs to produce proinflammatory cytokines (interleukin-12, tumor necrosis factor-alpha, and interferon (IFN)alpha/beta), and to display a mature phenotype (CD40(high)CD86(high) major histocompatibility complex (MHC II)(high)). When delivered to mice bearing 10-day-old lung metastatic tumors, DCs infected with DeltaM51-VSV encoding a tumor-associated antigen mediated significant control of tumor growth by engaging both NK and CD8(+) T cells. Importantly, depletion of NK cells completely abrogated tumor destruction, indicating that NK cells play a critical role for this DC vaccine-induced therapeutic outcome. Our findings identify DeltaM51-VSV as both an efficient gene-delivery vector and a maturation agent allowing DC vaccines to overcome immunosuppression in the tumor-bearing host.

Optimization of vaccine responses with an E1, E2b and E3-deleted Ad5 vector circumvents pre-existing anti-vector immunity

Recombinant serotype 5 adenovirus (Ad5) vectors lacking E1 expression induce robust immune responses against encoded transgenes in preclinical models, but have muted responses in human trials due to wide spread pre-existing anti-adenovirus immunity. Attempts to circumvent Ad5 specific immunity by using alternative serotypes or modifying capsid components have not yielded profound clinical improvement. To address this issue, we explored a novel alternative strategy, specifically reducing the expression of structural Ad5 genes by creating E1 and E2b deleted recombinant Ad5 vectors. Our data demonstrate that [E1−, E2b−]vectors retaining the Ad5 serotype are potent immunogens in pre-clinical models despite the presence of significant Ad5 specific immunity, in contrast to [E1−] vectors. These preclinical studies with E1 and E2b deleted recombinant Ad5 vectors suggest that anti-Ad immunity will no longer be a limiting factor and that clinical trials to evaluate their performance are warranted.

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.

Adenovirus efficiently transduces plasmacytoid dendritic cells resulting in TLR9-dependent maturation and IFN-alpha production

BACKGROUND

Recombinant replication-deficient adenoviral vectors (recAd) are attractive candidates for DNA vaccination approaches because they are able to activate the innate and adaptive immune systems. Here we explore the ability of recAd to transduce and activate subsets of dendritic cells, namely plasmacytoid dendritic cells (pDC) and conventional dendritic cells (cDC).

METHODS

DC were derived from bone marrow precursors in vitro with the help of FLT3-ligand. Sorted populations of pDC and cDC were infected with recAd at various multiplicities of infection. Transduction efficiency, phenotypic maturation and production of IFN-alpha as well as IL-6 were assessed. Additionally, activation of DC and induction of cytotoxic T lymphocytes (CTL) were determined in vivo. The role of Toll-like receptor (TLR) 9 in recAd recognition was investigated as it has previously been shown that DNA viruses are recognized via this receptor.

RESULTS

RecAd can efficiently transduce pDC as well as cDC in vitro. Both DC subsets mature and produce IFN-alpha upon interaction with recAd. In the absence of TLR9, activation and cytokine production was only detected in cDC but not in pDC. Importantly, induction of CD8+ CTL following in vivo injection of recAd was similar in TRL9-deficient mice when compared with wildtype controls.

CONCLUSIONS

RecAd can efficiently transduce and activate both pDC and cDC. pDC required TLR9 to detect the presence of recAd whereas cDC also recognized recAd independently of TLR9. These unique immunostimulatory properties support the future development of recombinant Ad as a vector for DNA vaccine approaches.

Centrifugation enhances integrin-mediated transduction of dendritic cells by conventional and RGD-modified adenoviral vectors

The level of antigen loading can impact on the capacity for dendritic cells (DC) to activate T cell responses. Several different approaches to adenoviral (Ad)-based transduction were therefore assessed for their effect on both transgene expression and T cell activation. While a conventional E1(-)/E3Delta Ad vector (Ad/GFP) produced a concentration-dependent expression of GFP, a modified vector expressing Arginine-Glycine-Aspartic Acid (RGD) sequence on its fiber knob (Ad-RGD/GFP) enhanced transgene expression by 9-20-fold at each MOI. The addition of centrifugal force (2000xg) during DC transduction with Ad/GFP also increased expression up to 20-fold. However, combining centrifugation with the Ad-RGD/GFP vector produced no effect on transduction rate and only a 1.5- to 2-fold increase in GFP expression, suggesting overlapping mechanisms of action. Consistent with this, exogenous RGD peptide blocked transduction regardless of the vector used, or the addition of centrifugal force, and transduction was primarily limited to DC expressing the CD51 integrin receptor. Ad vectors expressing ovalbumin (OVA) were used to assess transduced DC for their capacity to activate OVA-specific T cells. We observed a significant relationship between transgene expression and the capacity for T cell activation regardless of whether transgene expression was increased by using a higher MOI, an RGD-modified vector, or by employing centrifugal force. Furthermore, combining these approaches produced synergistic effects on T cell activation. We conclude that RGD-modified vectors and centrifugation both enhance DC transduction by increasing entry via integrin receptors and that the capacity for T cell activation can be optimized by combining approaches to achieve the highest possible level of transgene expression.