Presentation of tumour antigens by dendritic cells and challenges faced

Neoantigen Identification and Dendritic Cell-Based Vaccines for Lung Cancer Immunotherapy

Immunotherapies can treat many cancers, including difficult-to-treat cases such as lung cancer. Due to its tolerability, long-lasting therapeutic responses, and efficacy in a wide spectrum of patients, immunotherapy can also help to treat lung cancer, which has few treatment choices. Tumor-specific antigens (TSAs) for cancer vaccinations and T-cell therapies are difficult to discover. Neoantigens (NeoAgs) from genetic mutations, irregular RNA splicing, protein changes, or viral genetic sequences in tumor cells provide a solution. NeoAgs, unlike TSAs, are non-self and can cause an immunological response. Next-generation sequencing (NGS) and bioinformatics can swiftly detect and forecast tumor-specific NeoAgs. Highly immunogenic NeoAgs provide personalized or generalized cancer immunotherapies. Dendritic cells (DCs), which originate and regulate T-cell responses, are widely studied potential immunotherapeutic therapies for lung cancer and other cancers. DC vaccines are stable, reliable, and safe in clinical trials. The purpose of this article is to evaluate the current status, limitations, and prospective clinical applications of DC vaccines, as well as the identification and selection of major histocompatibility complex (MHC) class I and II genes for NeoAgs. Our goal is to explain DC biology and activate DC manipulation to help researchers create extremely potent cancer vaccines for patients.

ATP stabilised and sensitised calcium phosphate nanoparticles as effective adjuvants for a DNA vaccine against cancer

Cancer vaccines based on DNA encoding oncogenes have shown great potential in preclinical studies. However, the efficacy of DNA vaccines is limited by their weak immunogenicity because of low cellular internalisation and insufficient activation of dendritic cells (DCs). Calcium phosphate (CP) nanoparticles (NPs) are biodegradable vehicles with low toxicity and high loading capacity of DNA but suffer from stability issues. Here we employed adenosine triphosphate (ATP) as a dual functional agent, i.e. stabiliser for CP and immunological adjuvant, and applied the ATP-modified CP (ACP) NPs to the DNA vaccine. ACP NP-enhanced cellular uptake and improved transfection efficiency of DNA vaccine, and further showed the ability to activate DCs that are critical for them to prime T cells in cancer immunotherapy. As a result, a higher level of antigen-specific antibody with stronger tumour growth inhibition was achieved in mice immunised with the ACP-DNA vaccine. Overall, this one-step synthesised ACP NPs are an efficient nano-delivery system and nano-adjuvant for cancer DNA vaccines.

Mesenchymal Stem Cells Beyond Regenerative Medicine

Mesenchymal stem cells (MSCs) are competent suitors of cellular therapy due to their therapeutic impact on tissue degeneration and immune-based pathologies. Additionally, their homing and immunomodulatory properties can be exploited in cancer malignancies to transport pharmacological entities, produce anti-neoplastic agents, or induce anti-tumor immunity. Herein, we create a portfolio for MSC properties, showcasing their distinct multiple therapeutic utilities and successes/challenges thereof in both animal studies and clinical trials. We further highlight the promising potential of MSCs not only in cancer management but also in instigating tumor-specific immunity - i.e., cancer vaccination. Finally, we reflect on the possible reasons impeding the clinical advancement of MSC-based cancer vaccines to assist in contriving novel methodologies from which a therapeutic milestone might emanate.

Cytolytic Activity of Effector T-lymphocytes Against Hepatocellular Carcinoma is Improved by Dendritic Cells Pulsed with Pooled Tumor Antigens

Cellular immunotherapy is a promising new therapeutic approach for hepatocellular carcinoma (HCC), which has a high recurrence rate, irrespective of the treatment administered. In this study, we attempted to improve the cytolytic activity of effector T-lymphocytes against HCC. T-lymphocytes were activated by monocyte-derived dendritic cells (DCs) pulsed with cell lysate or RNA prepared from HCC cell lines. Monocytes were activated for differentiation into DCs by treatment with the IL4 and GM-CSF. DCs were pulsed with cell lysate or RNA prepared from a single cell line or combinations of two or three HCC cell lines, and then co-cultured with autologous T-lymphocytes with the intent of creating specific cytotoxicity. We discovered that DCs pulsed with total RNA effectuated greater T-lymphocyte function than DCs pulsed with total cell lysate, as evidenced by greater cytolytic activities against HCC target cells. The percentage of Huh7, HepG2, and SNU449 cell apoptosis at effector:target ratio of 10:1 was 42.6 ± 4.5% (p = 0.01), 33.6 ± 3.1% (p = 0.007), and 21.4 ± 1.4% (p < 0.001), respectively. DCs pulsed with pools of antigens prepared from three cell lines improved the cytolytic function of effector T-lymphocytes by approximately two-fold (p < 0.001), which suggests that this approach be further developed and applied for adoptive transfer treatment of HCC.

Use of antigen-primed dendritic cells for inducing antitumor immune responses in vitro in patients with non-small cell lung cancer

Cancer is associated with a reduction in immature and mature circulating dendritic cells (DCs), and with an impaired migratory capacity, compared with healthy donors. Therefore, modern approaches to the in vitro generation of DCs loaded with tumor antigens and their use for inducing antitumor immune responses in vivo are being investigated. The purpose of the present study was to investigate the phenotypic and functional characteristics of peripheral blood DC subsets in patients with non-small cell lung cancer (NSCLC), and the development of an antitumor cytotoxic response by mononuclear cells (MNCs) from patients using in vitro generated antigen-primed DCs. Heparinized peripheral venous blood samples were obtained from 10 healthy donors and 20 patients with a histologically verified diagnosis of NSCLC. The ability of antigen-activated DCs to stimulate the activity of MNCs against autologous tumor cells was evaluated using a cytotoxic test. Peripheral blood DC subsets from patients with NSCLC were identified to be decreased and to exhibit an impaired ability to mature, compared with healthy donors. Furthermore, DCs generated from MNCs from patients with NSCLC were able to stimulate a specific cytotoxic response when loaded with autologous tumor lysates or RNA and matured, in vitro. A perforin and granzyme B-dependent mode of cytotoxicity was primarily induced. The ability of DCs loaded with tumor antigens to increase the cytotoxic activity of MNCs against NSCLC cells in vitro indicates the effective induction and co-stimulation of T lymphocytes by the generated DCs.

Polymer-Based DNA Delivery Systems for Cancer Immunotherapy

The use of gene delivery systems for the expression of antigenic proteins is an established means for activating a patient’s own immune system against the cancer they carry. Since tumor cells are poor antigen-presenting cells, cross-presentation of tumor antigens by dendritic cells (DCs) is essential for the generation of tumor-specific cytotoxic T-lymphocyte responses. A number of polymer-based nanomedicines have been developed to deliver genes into DCs, primarily by incorporating tumor-specific, antigen-encoding plasmid DNA with polycationic molecules to facilitate DNA loading and intracellular trafficking. Direct in vivo targeting of plasmid DNA to DC surface receptors can induce high transfection efficiency and long-term gene expression, essential for antigen loading onto major histocompatibility complex molecules and stimulation of T-cell responses. This chapter summarizes the physicochemical properties and biological information on polymer-based non-viral vectors used for targeting DCs, and discusses the main challenges for successful in vivo gene transfer into DCs.

Endogenous and tumour-derived microRNAs regulate cross-presentation in dendritic cells and consequently cytotoxic T cell function

Dendritic cells (DCs) are potent antigen presenting cells (APCs). They are also specialized in the induction of cytotoxic T lymphocyte mediated responses against extracellular antigens, including tumour-specific antigens, by presenting peptide-Major Histocompatibility Complex (MHC) I complexes to naïve CD8⁺ T cells in lymphoid tissues, a process called cross-presentation. Emerging evidence suggests that the efficiency of cross-presentation can be influenced by a unique set of microRNAs (miRNAs). Some are differentially expressed in the course of morphological and functional development of DCs while tumorigenic miRNAs (onco-miRs) can be delivered to and inserted into DCs via exosomes. The latter reprogram the miRNA repertoire of DCs, transforming them from effective APCs to negative modulators of immunity, ultimately aiding cancers to evade host immunity. On the other hand, endogenous microRNAs can influence cross-presentation either positively or negatively. In this review, we discuss the possible mechanisms by which specific miRNAs influence cross-presentation as well as the viability of manipulating the expression of miRNAs that regulate DC cross-presentation as a potential cancer immunotherapy intervention.

Cytokine-enhanced maturation and migration to the lymph nodes of a human dying melanoma cell-loaded dendritic cell vaccine

Dendritic cells (DCs) are professional APCs used for the development of cancer vaccines because of their ability to activate adaptive immune responses. Previously, we designed the DC/Apo-Nec vaccine using human DCs loaded with dying melanoma cells that primed Ag-specific cytotoxic T cells. Here, we evaluate the effect of a standard pro-inflammatory cytokine cocktail (CC) and adjuvants on DC/Apo-Nec maturation and migration. CC addition to the vaccine coculture allowed efficient Ag uptake while attaining strong vaccine maturation with an immunostimulatory profile. The use of CC not only increased CCR7 expression and the vaccine chemokine responsiveness but also upregulated matrix metalloproteinase-9 secretion, which regulated its invasive migration in vitro. Neither IL-6 nor prostaglandin E2 had a negative effect on vaccine preparation. In fact, all CC components were necessary for complete vaccine maturation. Subcutaneously injected DC/Apo-Nec vaccine migrated rapidly to draining LNs in nude mice, accumulating regionally after 48 h. The migrating cells of the CC-matured vaccine augmented in proportion and range of distribution, an effect that increased further with the topical administration of imiquimod cream. The migrating proportion of human DCs was detected in draining LNs for at least 9 days after injection. The addition of CC during DC/Apo-Nec preparation enhanced vaccine performance by improving maturation and response to LN signals and by conferring a motile and invasive vaccine phenotype both in vitro and in vivo. More importantly, the vaccine could be combined with different adjuvants. Therefore, this DC-based vaccine design shows great potential value for clinical translation.

Antigenically Modified Human Pluripotent Stem Cells Generate Antigen-Presenting Dendritic Cells

Human pluripotent stem cells (hPSCs) provide a promising platform to produce dendritic cell (DC) vaccine. To streamline the production process, we investigated a unique antigen-loading strategy that suits this novel platform. Specifically, we stably modified hPSCs using tumour antigen genes in the form of a full-length tumour antigen gene or an artificial tumour antigen epitope-coding minigene. Such antigenically modified hPSCs were able to differentiate into tumour antigen-presenting DCs. Without conventional antigen-loading, DCs derived from the minigene-modified hPSCs were ready to prime a tumour antigen-specific T cell response and further expand these specific T cells in restimulation processes. These expanded tumour antigen-specific T cells were potent effectors with central memory or effector memory phenotype. Thus, we demonstrated that immunocompetent tumour antigen-loaded DCs can be directly generated from antigenically modified hPSCs. Using such strategy, we can completely eliminate the conventional antigen-loading step and significantly simplify the production of DC vaccine from hPSCs.

Characterization of T cell repertoire of blood, tumor, and ascites in ovarian cancer patients using next generation sequencing

Tumor-infiltrating lymphocytes (TILs) play an important role in regulating the host immune response and are one of key factors in defining tumor microenvironment. Some studies have indicated that T cell infiltration in malignant ascites is associated with clinical outcome, but few studies have performed detailed characterization of T cell diversity or clonality in malignant effusions. We have applied a next generation sequencing method to characterize T cell repertoire of a set of primary cancers, ascites, and blood from 12 ovarian cancer patients and also analyzed the T cell subtype populations in malignant fluids from 3 ovarian cancer patients. We observed enrichment of certain T cells in tumors and ascites, but most of the enriched T cell receptor (TCR) sequences in tumors and ascites were not common. Moreover, we analyzed TCR sequences of T cell subtypes (CD4⁺, CD8⁺, and regulatory T cells) isolated from malignant effusions and also found clonal expansion of certain T cell populations, but the TCR sequences were almost mutually exclusive among the three subgroups. Although functional studies of clonally expanded T cell populations are definitely required, our approach offers a detailed characterization of T cell immune microenvironment in tumors and ascites that might differently affect antitumor immune response.

DC3-decorated polyplexes for targeted gene delivery into dendritic cells

Dendritic cells (DCs) are a family of specialized antigen presenting cells (APCs) that detect antigens and initiate a wide spectrum of immune responses against them. These characteristics make them promising candidates for immunotherapy manipulations. In this study we designed and synthesized DC-targeted block copolymers composed of linear polyethylenimine (PEI) conjugated to hydrophilic polyethylene glycol (PEG) installed with a DC-targeting peptide (DC3, primary sequence FYPSYHSTPQRP). Two different conjugation procedures (basic and modified) were employed to synthesize the DC3-PEG-b-PEI and the control SCRM-PEG-b-PEI (with a scrambled DC3 peptide sequence) by one-pot synthesis, in two steps. In the first, basic conjugation procedure, PEG with N-hydroxysuccinimide (NHS) ester and maleimide (MAL) groups (NHS-PEG-MAL, 3.5 kDa) was first coupled to linear PEI (25 kDa) via the NHS group to yield the intermediate MAL-PEG-b-PEI, that was then conjugated to N-terminus-cysteine harboring peptides DC3 or SCRM via the MAL double bond to yield the final DC3-PEG-b-PEI or SCRM-PEG-b-PEI copolymers, respectively. In the second, modified conjugation procedure, Fmoc-cysteine harboring DC3 or SCRM peptides were first conjugated to NHS-PEG-MAL via the MAL group followed by coupling to linear PEI via the NHS functional group. Fmoc cleavage yielded the same final product as in the basic procedure. The modified conjugation procedure was capable of yielding block copolymers richer with peptides, as determined by (1)H NMR analysis. Self-assembly of DC3-PEG-b-PEI copolymers and DNA molecules yielded nanosized polyion complexes (polyplexes), with lower surface charge and limited cytotoxicity when compared to the PEI building block. Significant transfection efficiency of the DC-targeted polyplexes by murine dendritic DC2.4 cells was observed only in DC3-PEG-b-PEI/DNA polyplexes synthesized by the modified conjugation procedure. These polyplexes, with higher peptide-load, showed greater transfection capability in DC2.4 cells relative to the control nontargeted SCRM-PEG-b-PEI/DNA polyplexes, but not in endothelial cells. The transfection efficiency was comparable to or higher than that of the PEI/DNA positive control. The results indicate that PEGylated-PEI polyplexes show significant transfection efficiency into DCs when decorated with DC3 peptide, and are attractive candidates for immunotherapy via DCs.

Induced pluripotent stem cells: challenges and opportunities for cancer immunotherapy

Despite recent advances in cancer treatment over the past 30 years, therapeutic options remain limited and do not always offer a cure for malignancy. Given that tumor-associated antigens (TAA) are, by definition, self-proteins, the need to productively engage autoreactive T cells remains at the heart of strategies for cancer immunotherapy. These have traditionally focused on the administration of autologous monocyte-derived dendritic cells (moDC) pulsed with TAA, or the ex vivo expansion and adoptive transfer of tumor-infiltrating lymphocytes (TIL) as a source of TAA-specific cytotoxic T cells (CTL). Although such approaches have shown some efficacy, success has been limited by the poor capacity of moDC to cross present exogenous TAA to the CD8⁺ T-cell repertoire and the potential for exhaustion of CTL expanded ex vivo. Recent advances in induced pluripotency offer opportunities to generate patient-specific stem cell lines with the potential to differentiate in vitro into cell types whose properties may help address these issues. Here, we review recent success in the differentiation of NK cells from human induced pluripotent stem (iPS) cells as well as minor subsets of dendritic cells (DCs) with therapeutic potential, including CD141⁺XCR1⁺ DC, capable of cross presenting TAA to naïve CD8⁺ T cells. Furthermore, we review recent progress in the use of TIL as the starting material for the derivation of iPSC lines, thereby capturing their antigen specificity in a self-renewing stem cell line, from which potentially unlimited numbers of naïve TAA-specific T cells may be differentiated, free of the risks of exhaustion.

Antigen cross-presentation of immune complexes

The ability of dendritic cells (DCs) to cross-present tumor antigens has long been a focus of interest to physicians, as well as basic scientists, that aim to establish efficient cell-based cancer immune therapy. A prerequisite for exploiting this pathway for therapeutic purposes is a better understanding of the mechanisms that underlie the induction of tumor-specific cytotoxic T-lymphocyte (CTL) responses when initiated by DCs via cross-presentation. The ability of humans DC to perform cross-presentation is of utmost interest, as this cell type is a main target for cell-based immunotherapy in humans. The outcome of a cross-presentation event is guided by the nature of the antigen, the form of antigen uptake, and the subpopulation of DCs that performs presentation. Generally, CD8α⁺ DCs are considered to be the most potent cross-presenting DCs. This paradigm, however, only applies to soluble antigens. During adaptive immune responses, immune complexes form when antibodies interact with their specific epitopes on soluble antigens. Immunoglobulin G (IgG) immune complexes target Fc-gamma receptors on DCs to shuttle exogenous antigens efficiently into the cross-presentation pathway. This receptor-mediated cross-presentation pathway is a well-described route for the induction of strong CD8⁺ T cell responses. IgG-mediated cross-presentation is intriguing because it permits the CD8⁻ DCs, which are commonly considered to be weak cross-presenters, to efficiently cross-present. Engaging multiple DC subtypes for cross-presentation might be a superior strategy to boost CTL responses in vivo. We here summarize our current understanding of how DCs use IgG-complexed antigens for the efficient induction of CTL responses. Because of its importance for human cell therapy, we also review the recent advances in the characterization of cross-presentation properties of human DC subsets.

Autologous dendritic cells combined with cytokine-induced killer cells synergize low-dose chemotherapy in elderly patients with acute myeloid leukaemia

OBJECTIVES

To investigate the possibility of culturing dendritic cells (DCs) and cytokine-induced killer (CIK) cells, obtained at initial diagnosis of AML in elderly patients, and to investigate the safety and efficacy of treatment with autologous DCs and CIK cells when administered to these patients in combination with low-dose chemo therapy.

METHODS

DCs and CIK cells obtained at initial diagnosis of AML in elderly patients were cultured and used in combination with low-dose chemo therapy to treat these patients (immunotherapy group). Elderly patients with AML treated only with low-dose chemotherapy served as the control. Before treatment and on day 7 after treatment with autologous DCs and CIK cells, T cell subsets and cytokine levels were evaluated in the immunotherapy group.

RESULTS

A total of 21 elderly patients with AML were included in the immunotherapy group and 23 in the control group. The clinical efficacy in the immunotherapy group was greater than in the control group. The percentages of T cell subsets and cytokine levels after immunotherapy treatment were significantly higher than before the treatment.

CONCLUSION

Immuno therapy with autologous DCs and CIK cells was found to be a promising candidate for treatment of AML in elderly patients.

Optimized adoptive T-cell therapy for the treatment of residual mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive B-cell neoplasm with few patients achieving long-term survival with current treatment regimens. High-dose therapy is effective in reducing the tumor burden; however, patients eventually relapse due to minimal residual disease. Having demonstrated efficacy in other malignancies, the effectiveness of dendritic cell-based immunotherapy for minimal residual MCL was examined. We demonstrated that dendritic cells (DC) primed with MCL antigens stimulated the activation of MCL-specific T cells that recognized and destroyed both MCL cell lines and primary MCL in vitro. In addition, in vivo studies demonstrated that adoptively transferred MCL-specific T cells were able to significantly inhibit tumor growth in mice with minimal residual MCL. Subsequently, when combined with CHOP chemotherapy, adoptive T-cell therapy was able to significantly extend the survival of the mice by further reducing the tumor burden. These results clearly show that MCL-specific cellular immunotherapy is effective in treating minimal residual MCL, paving the way for future clinical studies.

MyD88 inhibition amplifies dendritic cell capacity to promote pancreatic carcinogenesis via Th2 cells

The transition of chronic pancreatic fibroinflammatory disease to neoplasia is a primary example of the paradigm linking inflammation to carcinogenesis. However, the cellular and molecular mediators bridging these entities are not well understood. Because TLR4 ligation can exacerbate pancreatic inflammation, we postulated that TLR4 activation drives pancreatic carcinogenesis. In this study, we show that lipopolysaccharide accelerates pancreatic tumorigenesis, whereas TLR4 inhibition is protective. Furthermore, blockade of the MyD88-independent TRIF pathway is protective against pancreatic cancer, whereas blockade of the MyD88-dependent pathway surprisingly exacerbates pancreatic inflammation and malignant progression. The protumorigenic and fibroinflammatory effects of MyD88 inhibition are mediated by dendritic cells (DCs), which induce pancreatic antigen-restricted Th2-deviated CD4(+) T cells and promote the transition from pancreatitis to carcinoma. Our data implicate a primary role for DCs in pancreatic carcinogenesis and illustrate divergent pathways in which blockade of TLR4 signaling via TRIF is protective against pancreatic cancer and, conversely, MyD88 inhibition exacerbates pancreatic inflammation and neoplastic transformation by augmenting the DC-Th2 axis.

The role of antigen cross-presentation from leukemia blasts on immunity to the leukemia-associated antigen PR1

Cross-presentation is an important mechanism by which exogenous tumor antigens are presented to elicit immunity. Because neutrophil elastase (NE) and proteinase-3 (P3) expression is increased in myeloid leukemia, we investigated whether NE and P3 are cross-presented by dendritic cells (DC) and B cells, and whether the NE and P3 source determines immune outcomes. We show that NE and P3 are elevated in leukemia patient serum and that levels correlate with remission status. We demonstrate cellular uptake of NE and P3 into lysosomes, ubiquitination, and proteasome processing for cross-presentation. Using anti-PR1/human leukocyte antigen-A2 monoclonal antibody, we provide direct evidence that B-cells cross-present soluble and leukemia-associated NE and P3, whereas DCs cross-present only leukemia-associated NE and P3. Cross-presentation occurred at early time points but was not associated with DC or B-cell activation, suggesting that NE and P3 cross-presentation may favor tolerance. Furthermore, we show aberrant subcellular localization of NE and P3 in leukemia blasts to compartments that share common elements of the classic major histocompatibility class I antigen-presenting pathway, which may facilitate cross-presentation. Our data demonstrate distinct mechanisms for cross-presentation of soluble and cell-associated NE and P3, which may be valuable in understanding immunity to PR1 in leukemia.

Developing Phytocompounds from Medicinal Plants as Immunomodulators

Imbalance or malfunction of the immune systems is associated with a range of chronic diseases including autoimmune diseases, allergies, cancers and others. Various innate and adaptive immune cells that are integrated in this complex networking system may represent promising targets for developing immunotherapeutics for treating specific immune diseases. A spectrum of phytochemicals have been isolated, characterized and modified for development and use as prevention or treatment of human diseases. Many cytotoxic drugs and antibiotics have been developed from phytocompounds, but the application of traditional or new medicinal plants for use as immunomodulators in treating immune diseases is still relatively limited. In this review, a selected group of medicinal herbs, their derived crude or fractionated phytoextracts and the specific phytochemicals/phytocompounds isolated from them, as well as categorized phytocompound groups with specific chemical structures are discussed in terms of their immunomodulatory bioactivities. We also assess their potential for future development as immunomodulatory or inflammation-regulatory therapeutics or agents. New experimental approaches for evaluating the immunomodulatory activities of candidate phytomedicines are also discussed.

Cancer immunotherapy: a paradigm shift for prostate cancer treatment

Prostate cancer remains a significant health problem for men in the Western world. Although treatment modalities are available, these do not confer long-term benefit and are accompanied by deleterious side effects. Immunotherapy represents a valuable alternative to conventional treatments by inducing tumour-specific immune responses that control the growth of cancer cells. Sipuleucel-T is approved by the FDA as an immunotherapeutic agent for the treatment of patients with asymptomatic or minimally symptomatic castration-resistant prostate cancer (CRPC). Although this approval has raised cost-versus-benefit issues, it has provided proof of concept for the therapeutic potential of active immunotherapy approaches for metastatic CRPC. Numerous clinical studies have demonstrated clinical benefit using immunotherapy compared to traditional chemotherapy and several active immunotherapy approaches (at various developmental stages)have demonstrated the potential to change the face of prostate cancer treatment.

Off-the-shelf adenoviral-mediated immunotherapy via bicistronic expression of tumor antigen and iMyD88/CD40 adjuvant

Recent modest successes in ex vivo dendritic cell (DC) immunotherapy have motivated continued innovation in the area of DC manipulation and activation. Although ex vivo vaccine approaches continue to be proving grounds for new DC manipulation techniques, the intrinsic limits of ex vivo therapy, including high cost, minimal standardization, cumbersome delivery, and poor accessibility, incentivizes the development of vaccines compatible with in vivo DC targeting. We describe here a method to co-deliver both tumor-specific antigen (TSA) and an iMyD88/CD40 adjuvant (iMC), to DCs that combines toll-like receptor (TLR) and CD40 signaling. In this study, we demonstrate that simple TSA delivery via adenoviral vectors results in strong antitumor immunity. Addition of iMC delivered in a separate vector is insufficient to enhance this effect. However, when delivered simultaneously with TSA in a single bicistronic vector (BV), iMC is able to significantly enhance antigen-specific cytotoxic T-cell (CTL) responses and inhibit established tumor growth. This study demonstrates the spatial-temporal importance of concurrent DC activation and TSA presentation. Further, it demonstrates the feasibility of in vivo molecular enhancement of DCs necessary for effective antitumor immune responses.

Dual antigen target-based immunotherapy for prostate cancer eliminates the growth of established tumors in mice

AIMS

We have previously shown that immunization with an adenovirus vector carrying an individual antigen induces antigen-specific CD8 T cells actively engaged in the destruction of tumor cells expressing the cognate antigen. In order to expand the range of antitumor responses beyond an individual antigen, we designed a recombinant adenovirus type 5 (rAd5) carrying a fusion construct of two full-length antigens. We used this adenovirus vector to test the concept that multiantigenic effector T cells could be generated simultaneously following a single immunization.

METHOD

To perform the rAd5 constructs, we selected a combination of prostate-specific antigen (PSA) and prostate stem cell antigen (PSCA) genes based on their restricted distribution within the prostate tissue and their association with the development and progression of prostate cancer.

RESULTS

Immunization of mice with rAd5 vector carrying a fusion construct of PSA and PSCA (Ad5-PSA/PSCA) simultaneously induced the expansion of anti-PSA and anti-PSCA CD8 T cells, as measured by intracellular cytokine staining for IFN-γ. The antigen-specific T-cell responses that developed were efficient in eliminating the target cells expressing cognate antigens measured by an in vivo cytotoxic T-cell assay. The in vivo tumor growth study showed that immunization of mice with Ad5-PSA/PSCA vaccine induced strong antitumor immunity when challenged with mouse prostate tumor cell lines (RM11) expressing human PSA (RM11/PSA). To further analyze the impact on therapeutic efficacy of Ad5-PSA/PSCA vaccine against the tumor cells expressing PSA and PSCA (RM11-PSA/PSCA) antigens, we injected mice with Ad5-PSA/PSCA vaccine. The vaccine inhibited the growth of established tumors with 80% of the mice becoming tumor free. These data provide useful information that antigen-specific effector T cells can be generated simultaneously and that their additive antitumor effect has the potential to eliminate the growth of established tumors. Therefore, the immunotherapy approach of using the simultaneous targeting of dual antigens associated with prostate cancer may have important implications for human clinical trials.

Targeting Dendritic Cells in vivo for Cancer Therapy

Monoclonal antibodies that recognize cell surface molecules have been used deliver antigenic cargo to dendritic cells (DC) for induction of immune responses. The encouraging anti-tumor immunity elicited using this immunization strategy suggests its suitability for clinical trials. This review discusses the complex network of DC, the functional specialization of DC subsets, the immunological outcomes of targeting different DC subsets and their cell surface receptors, and the requirements for the induction of effective anti-tumor CD4 and CD8 T cell responses that can recognize tumor-specific antigens. Finally, we review preclinical experiments and the progress toward targeting human DC in vivo.

Cross-presentation of tumour antigens by human induced pluripotent stem cell-derived CD141(+)XCR1+ dendritic cells

Monocyte-derived dendritic cells (moDC) have been widely used in cancer immunotherapy but show significant donor-to-donor variability and low capacity for the cross-presentation of tumour-associated antigens (TAA) to CD8(+) T cells, greatly limiting the success of this approach. Given recent developments in induced pluripotency and the relative ease with which induced pluripotent stem (iPS) cell lines may be generated from individuals, we have succeeded in differentiating dendritic cells (DC) from human leukocyte antigen (HLA)-A(*)0201(+) iPS cells (iPS cell-derived DC (ipDC)), using protocols compliant with their subsequent clinical application. Unlike moDC, a subset of ipDC was found to coexpress CD141 and XCR1 that have been shown previously to define the human equivalent of mouse CD8α(+) DC, in which the capacity for cross-presentation has been shown to reside. Accordingly, ipDC were able to cross-present the TAA, Melan A, to a CD8(+) T-cell clone and stimulate primary Melan A-specific responses among naïve T cells from an HLA-A(*)0201(+) donor. Given that CD141(+)XCR1(+) DC are present in peripheral blood in trace numbers that preclude their clinical application, the ability to generate a potentially unlimited source from iPS cells offers the possibility of harnessing their capacity for cross-priming of cytotoxic T lymphocytes for the induction of tumour-specific immune responses.

How to connect an IgE-driven response with CTL activity?

One of the goals of cell-based immune therapy in cancer is the induction of tumor-specific cytotoxic T-lymphocyte (CTL) responses. To achieve this objective, the ability of dendritic cells (DC) to cross-present tumor antigens can be exploited. One of the most efficient pathways for the induction of CTLs by cross-presentation is mediated by immunoglobulins of the IgG class, which are used by DCs to sample antigen in the form of immune complexes via Fc-gamma receptors. Could DCs use an IgE-mediated cross-presentation mechanism in a comparable manner to induce CTLs? We here discuss the potential of two human IgE Fc receptors, FcεRI and FcεRII, to serve as antigen uptake receptors for IgE-mediated cross-presentation. We conclude that the existence of an IgE-mediated cross-presentation pathway would provide a direct link between IgE-driven immune responses and CTL activity.

Modification of human embryonic stem cell-derived dendritic cells with mRNA for efficient antigen presentation and enhanced potency

AIM

Dendritic cell (DC)-based vaccines are designed to exploit the intrinsic capacity of these highly effective antigen presenting cells to prime and boost antigen-specific T-cell immune responses. Successful development of DC-based vaccines will be dependent on the ability to utilize and harness the full potential of these potent immune stimulatory cells. Recent advances to generate DCs derived from human embryonic stem cells (hESCs) that are suitable for clinical use represent an alternative strategy from conventional approaches of using patient-specific DCs. Although the differentiation of hESC-derived DCs in serum-free defined conditions has been established, the stimulatory potential of these hESC-derived DCs have not been fully evaluated.

METHODS

hESC-derived DCs were differentiated in serum-free defined culture conditions. The delivery of antigen into hESC-derived DCs was investigated using mRNA transfection and replication-deficient adenoviral vector transduction. hESC-derived DCs modified with antigen were evaluated for their capacity to stimulate antigen-specific T-cell responses with known HLA matching. Since IL-12 is a key cytokine that drives T-cell function, further enhancement of DC potency was evaluated by transfecting mRNA encoding the IL-12p70 protein into hESC-derived DCs.

RESULTS

The transfection of mRNA into hESC-derived DCs was effective for heterologous protein expression. The efficiency of adenoviral vector transduction into hESC-derived DCs was poor. These mRNA-transfected DCs were capable of stimulating human telomerase reverse transcriptase antigen-specific T cells composed of varying degrees of HLA matching. In addition, we observed the transfection of mRNA encoding IL-12p70 enhanced the T-cell stimulation potency of hESC-derived DCs.

CONCLUSION

These data provide support for the development and modification of hESC-derived DCs with mRNA as a potential strategy for the induction of T-cell-mediated immunity.

Clinical evaluation of cellular immunotherapy in acute myeloid leukaemia

Immunotherapy is currently under active investigation as an adjuvant therapy to improve the overall survival of patients with acute myeloid leukaemia (AML) by eliminating residual leukaemic cells following standard therapy. The graft-versus-leukaemia effect observed following allogeneic haematopoietic stem cell transplantation has already demonstrated the significant role of immune cells in controlling AML, paving the way to further exploitation of this effect in optimized immunotherapy protocols. In this review, we discuss the current state of cellular immunotherapy as adjuvant therapy for AML, with a particular focus on new strategies and recently published results of preclinical and clinical studies. Therapeutic vaccines that are being tested in AML include whole tumour cells as an autologous source of multiple leukaemia-associated antigens (LAA) and autologous dendritic cells loaded with LAA as effective antigen-presenting cells. Furthermore, adoptive transfer of cytotoxic T cells or natural killer cells is under active investigation. Results from phase I and II trials are promising and support further investigation into the potential of cellular immunotherapeutic strategies to prevent or fight relapse in AML patients.

ISCOMATRIX adjuvant combines immune activation with antigen delivery to dendritic cells in vivo leading to effective cross-priming of CD8+ T cells

Cancer vaccines aim to induce CTL responses against tumors. Challenges for vaccine design are targeting Ag to dendritic cells (DCs) in vivo, facilitating cross-presentation, and conditioning the microenvironment for Th1 type immune responses. In this study, we report that ISCOM vaccines, which consist of ISCOMATRIX adjuvant and protein Ag, meet these challenges. Subcutaneous injection of an ISCOM vaccine in mice led to a substantial influx and activation of innate and adaptive immune effector cells in vaccine site-draining lymph nodes (VDLNs) as well as IFN-γ production by NK and NKT cells. Moreover, an ISCOM vaccine containing the model Ag OVA (OVA/ISCOM vaccine) was efficiently taken up by CD8α(+) DCs in VDLNs and induced their maturation and IL-12 production. Adoptive transfer of transgenic OT-I T cells revealed highly efficient cross-presentation of the OVA/ISCOM vaccine in vivo, whereas cross-presentation of soluble OVA was poor even at a 100-fold higher concentration. Cross-presenting activity was restricted to CD8α(+) DCs in VDLNs, whereas Langerin(+) DCs and CD8α(-) DCs were dispensable. Remarkably, compared with other adjuvant systems, the OVA/ISCOM vaccine induced a high frequency of OVA-specific CTLs capable of tumor cell killing in different tumor models. Thus, ISCOM vaccines combine potent immune activation with Ag delivery to CD8α(+) DCs in vivo for efficient induction of CTL responses.

Lung cancer-derived galectin-1 mediates dendritic cell anergy through inhibitor of DNA binding 3/IL-10 signaling pathway

Lung cancer, one of the leading causes of death worldwide, is often associated with a state of immune suppression, but the molecular and functional basis remains enigmatic. Evidence is provided in this paper supporting the role of lung cancer-derived soluble lectin, galectin-1, as a culprit in dendritic cell (DC) anergy. We have shown that galectin-1 is highly expressed in lung cancer cell lines, together with the serum and surgical samples from lung cancer patients. Functionally, lung cancer-derived galectin-1 has been shown to alter the phenotypes of monocyte-derived DCs (MdDCs) and impair alloreactive T cell response, concomitant with the increase of CD4(+)CD25(+)FOXP3(+) regulatory T cells. The regulatory effect of galectin-1 is mediated, in part, through its ability to induce, in an Id3 (inhibitor of DNA binding 3)-dependent manner, the expression of IL-10 in monocytes and MdDCs. This effect is inhibited by the addition of lactose, which normalizes the phenotypic and functional alterations seen in MdDCs. Of note, significant upregulation of IL-10 was seen in tumor-infiltrating CD11c(+) DCs in human lung cancer samples. This was also noted in mice transplanted with lung cancer cells, but not in those receiving tumor cells with galectin-1 knockdown. Furthermore, a significant reduction was noted in lung cancer incidence and in the levels of IL-10-expressing, tumor-infiltrating DCs, in mice receiving galectin-1-silenced tumor cells. These results thus suggest that the galectin-1/IL-10 functional axis may be crucial in lung cancer-mediated immune suppression, and that galectin-1 may serve as a target in the development of lung cancer immunotherapy.

E6 and E7 fusion immunoglobulin from human papilloma virus 16 induces dendritic cell maturation and antigen specific activation of T helper 1 response

Human papilloma virus (HPV) 16 causes cervical cancer. Induction of oncogenesis by HPV 16 is primarily dependent on the function of E6 and E7 proteins, which inactivate the function of p53 and pRB, respectively. Thus, blocking the activity of the E6 and E7 proteins from HPV 16 is critical to inhibiting oncogenesis during infection. We have expressed and purified soluble HPV 16 E6 and E7 fusion immunoglobulin (Ig), which were combined with the constant region of an Ig heavy chain, in a mammalian system. To assess whether soluble E6 and E7 fusion Igs induce effective cellular immune responses, immature dendritic cells (DCs) were treated with these fusion proteins. Soluble E6 and E7 fusion Igs effectively induced maturation of DCs. Furthermore, immunization with soluble E6 and E7 fusion Igs in mice resulted in antigen-specific activation of T helper 1 (Th1) cells. This is the first comprehensive study to show the molecular basis of how soluble HPV 16 E6 or E7 fusion Igs induces Th1 responses through the maturation of DCs. In addition, we show that DC therapy using soluble HPV E6 and E7 fusion Igs may be a valuable tool for controlling the progress of cervical cancer.

An integrated approach to epitope analysis II: A system for proteomic-scale prediction of immunological characteristics

Background

Improving our understanding of the immune response is fundamental to developing strategies to combat a wide range of diseases. We describe an integrated epitope analysis system which is based on principal component analysis of sequences of amino acids, using a multilayer perceptron neural net to conduct QSAR regression predictions for peptide binding affinities to 35 MHC-I and 14 MHC-II alleles.

Results

The approach described allows rapid processing of single proteins, entire proteomes or subsets thereof, as well as multiple strains of the same organism. It enables consideration of the interface of diversity of both microorganisms and of host immunogenetics. Patterns of binding affinity are linked to topological features, such as extracellular or intramembrane location, and integrated into a graphical display which facilitates conceptual understanding of the interplay of B-cell and T-cell mediated immunity.

Patterns which emerge from application of this approach include the correlations between peptides showing high affinity binding to MHC-I and to MHC-II, and also with predicted B-cell epitopes. These are characterized as coincident epitope groups (CEGs). Also evident are long range patterns across proteins which identify regions of high affinity binding for a permuted population of diverse and heterozygous HLA alleles, as well as subtle differences in reactions with MHCs of individual HLA alleles, which may be important in disease susceptibility, and in vaccine and clinical trial design. Comparisons are shown of predicted epitope mapping derived from application of the QSAR approach with experimentally derived epitope maps from a diverse multi-species dataset, from Staphylococcus aureus, and from vaccinia virus.

Conclusions

A desktop application with interactive graphic capability is shown to be a useful platform for development of prediction and visualization tools for epitope mapping at scales ranging from individual proteins to proteomes from multiple strains of an organism. The possible functional implications of the patterns of peptide epitopes observed are discussed, including their implications for B-cell and T-cell cooperation and cross presentation.

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.

Cross-priming in health and disease

Cross-priming is an important mechanism to activate cytotoxic T lymphocytes (CTLs) for immune defence against viruses and tumours. Although it was discovered more than 25 years ago, we have only recently gained insight into the underlying cellular and molecular mechanisms, and we are just beginning to understand its physiological importance in health and disease. Here we summarize current concepts on the cross-talk between the immune cells involved in CTL cross-priming and on its role in antimicrobial and antitumour defence, as well as in immune-mediated diseases.