NY-ESO-1 protein formulated in ISCOMATRIX adjuvant is a potent anticancer vaccine inducing both humoral and CD8+ t-cell-mediated immunity and protection against NY-ESO-1+ tumors

The current therapeutic cancer vaccines landscape in non-small cell lung cancer

Currently, conventional immunotherapies for the treatment of non-small cell lung cancer (NSCLC) have low response rates and benefit only a minority of patients, particularly those with advanced disease, so novel therapeutic strategies are urgent deeded. Therapeutic cancer vaccines, a form of active immunotherapy, harness potential to activate the adaptive immune system against tumor cells via antigen cross-presentation. Cancer vaccines can establish enduring immune memory and guard against recurrences. Vaccine-induced tumor cell death prompts antigen epitope spreading, activating functional T cells and thereby sustaining a cancer-immunity cycle. The success of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rendered cancer vaccines a promising avenue, especially when combined with immunotherapy or chemoradiotherapy for NSCLC. This review delves into the intricate antitumor immune mechanisms underlying therapeutic cancer vaccines, enumerates the tumor antigen spectrum of NSCLC, discusses different cancer vaccines progress and summarizes relevant clinical trials. Additionally, we analyze the combination strategies, current limitations, and future prospects of cancer vaccines in NSCLC treatment, aiming to offer fresh insights for their clinical application in managing NSCLC. Overall, cancer vaccines offer promising potential for NSCLC treatment, particularly combining with chemoradiotherapy or immunotherapy could further improve survival in advanced patients. Exploring inhaled vaccines or prophylactic vaccines represents a crucial research avenue.

Adjuvants: Engineering Protective Immune Responses in Human and Veterinary Vaccines

Adjuvants are key components of many vaccines, used to enhance the level and breadth of the immune response to a target antigen, thereby enhancing protection from the associated disease. In recent years, advances in our understanding of the innate and adaptive immune systems have allowed for the development of a number of novel adjuvants with differing mechanisms of action. Herein, we review adjuvants currently approved for human and veterinary use, describing their use and proposed mechanisms of action. In addition, we will discuss additional promising adjuvants currently undergoing preclinical and/or clinical testing.

Cancer nanotechnology: current status and perspectives

Modern medicine has been waging a war on cancer for nearly a century with no tangible end in sight. Cancer treatments have significantly progressed, but the need to increase specificity and decrease systemic toxicities remains. Early diagnosis holds a key to improving prognostic outlook and patient quality of life, and diagnostic tools are on the cusp of a technological revolution. Nanotechnology has steadily expanded into the reaches of cancer chemotherapy, radiotherapy, diagnostics, and imaging, demonstrating the capacity to augment each and advance patient care. Nanomaterials provide an abundance of versatility, functionality, and applications to engineer specifically targeted cancer medicine, accurate early-detection devices, robust imaging modalities, and enhanced radiotherapy adjuvants. This review provides insights into the current clinical and pre-clinical nanotechnological applications for cancer drug therapy, diagnostics, imaging, and radiation therapy.

Using Adjuvants to Drive T Cell Responses for Next-Generation Infectious Disease Vaccines

Using adjuvants to drive features of T cell responses to vaccine antigens is an important technological challenge in the design of new and improved vaccines against infections. Properties such as T helper cell function, T cell memory, and CD8+ T cell cytotoxicity may play critical roles in optimal and long-lived immunity through vaccination. Directly manipulating specific immune activation or antigen delivery pathways with adjuvants may selectively augment desired T cell responses in vaccination and may improve the effectiveness and durability of vaccine responses in humans. In this review we outline recently studied adjuvants in their potential for antigen presenting cell and T cell programming during vaccination, with an emphasis on what has been observed in studies in humans as available.

Ropporin-1 and 1B Are Widely Expressed in Human Melanoma and Evoke Strong Humoral Immune Responses

Antibodies that block immune regulatory checkpoints (programmed cell death 1, PD-1 and cytotoxic T-lymphocyte-associated antigen 4, CTLA-4) to mobilise immunity have shown unprecedented clinical efficacy against cancer, demonstrating the importance of antigen-specific tumour recognition. Despite this, many patients still fail to benefit from these treatments and additional approaches are being sought. These include mechanisms that boost antigen-specific immunity either by vaccination or adoptive transfer of effector cells. Other than neoantigens, epigenetically regulated and shared antigens such as NY-ESO-1 are attractive targets; however, tissue expression is often heterogeneous and weak. Therefore, peptide-specific therapies combining multiple antigens rationally selected to give additive anti-cancer benefits are necessary to achieve optimal outcomes. Here, we show that Ropporin-1 (ROPN1) and 1B (ROPN1B), cancer restricted antigens, are highly expressed and immunogenic, inducing humoral immunity in patients with advanced metastatic melanoma. By multispectral immunohistochemistry, 88.5% of melanoma patients tested (n = 54/61) showed ROPN1B expression in at least 1 of 2/3 tumour cores in tissue microarrays. Antibody responses against ROPN1A and ROPN1B were detected in 71.2% of melanoma patients tested (n = 74/104), with increased reactivity seen with more advanced disease stages. Thus, ROPN1A and ROPN1B may indeed be viable targets for cancer immunotherapy, alone or in combination with other cancer antigens, and could be combined with additional therapies such as immune checkpoint blockade.

Tumor ablation plus co-administration of CpG and saponin adjuvants affects IL-1 production and multifunctional T cell numbers in tumor draining lymph nodes

Background

Tumor ablation techniques, like cryoablation, are successfully used in the clinic to treat tumors. The tumor debris remaining in situ after ablation is a major antigen depot, including neoantigens, which are presented by dendritic cells (DCs) in the draining lymph nodes to induce tumor-specific CD8⁺ T cells. We have previously shown that co-administration of adjuvants is essential to evoke strong in vivo antitumor immunity and the induction of long-term memory. However, which adjuvants most effectively combine with in situ tumor ablation remains unclear.

Methods and results

Here, we show that simultaneous administration of cytidyl guanosyl (CpG) with saponin-based adjuvants following cryoablation affects multifunctional T-cell numbers and interleukin (IL)-1 induced polymorphonuclear neutrophil recruitment in the tumor draining lymph nodes, relative to either adjuvant alone. The combination of CpG and saponin-based adjuvants induces potent DC maturation (mainly CpG-mediated), antigen cross-presentation (mainly saponin-based adjuvant mediated), while excretion of IL-1β by DCs in vitro depends on the presence of both adjuvants. Most strikingly, CpG/saponin-based adjuvant exposed DCs potentiate antigen-specific T-cell proliferation resulting in multipotent T cells with increased capacity to produce interferon (IFN)γ, IL-2 and tumor necrosis factor-α in vitro. Also in vivo the CpG/saponin-based adjuvant combination plus cryoablation increased the numbers of tumor-specific CD8⁺ T cells showing enhanced IFNγ production as compared with single adjuvant treatments.

Conclusions

Collectively, these data indicate that co-injection of CpG with saponin-based adjuvants after cryoablation induces an increased amount of tumor-specific multifunctional T cells. The combination of saponin-based adjuvants with toll-like receptor 9 adjuvant CpG in a cryoablative setting therefore represents a promising in situ vaccination strategy.

A Phase 1b Study Evaluating the Safety, Tolerability, and Immunogenicity of CMB305, a Lentiviral-Based Prime-Boost Vaccine Regimen, in Patients with Locally Advanced, Relapsed, or Metastatic Cancer Expressing NY-ESO-1

Preclinical data suggest that a "prime-boost" vaccine regimen using a target-expressing lentiviral vector for priming, followed by a recombinant protein boost, may be effective against cancer; however, this strategy has not been evaluated in a clinical setting. CMB305 is a prime-boost vaccine designed to induce a broad anti-NY-ESO-1 immune response. It is composed of LV305, which is an NY-ESO-1 expressing lentiviral vector, and G305, a recombinant adjuvanted NY-ESO-1 protein. This multicenter phase 1b, first-in-human trial evaluated CMB305 in patients with NY-ESO-1 expressing solid tumors. Safety was examined in a 3 + 3 dose-escalation design, followed by an expansion with CMB305 alone or in a combination with either oral metronomic cyclophosphamide or intratumoral injections of a toll-like receptor agonist (glucopyranosyl lipid A). Of the 79 patients who enrolled, 81.0% had sarcomas, 86.1% had metastatic disease, and 57.0% had progressive disease at study entry. The most common adverse events were fatigue (34.2%), nausea (26.6%), and injection-site pain (24.1%). In patients with soft tissue sarcomas, a disease control rate of 61.9% and an overall survival of 26.2 months (95% CI, 22.1-NA) were observed. CMB305 induced anti-NY-ESO-1 antibody and T-cell responses in 62.9% and 47.4% of patients, respectively. This is the first trial to test a prime-boost vaccine regimen in patients with advanced cancer. This approach is feasible, can be delivered safely, and with evidence of immune response as well as suggestion of clinical benefit.

Novel HLA-A2 restricted antigenic peptide derivatives with high affinity for the treatment of breast cancer expressing NY-ESO-1

Tumor immunotherapy based on specific tumor antigen has become the focus for breast cancer, and research into cancer/testes antigens (CTA) is progressing. As an important member in the CTA, NY-ESO-1 plays a crucial role in the treatment and prognosis of breast cancer. In this study, we aimed to improve the binding ability to MHC by designing and synthesizing stable NY-ESO-1-derived peptides, based on NetMHC 4.0 webserver (http://www.cbs.dtu.dk/services/NetMHC/) and HLP webserver (http://crdd.osdd.net/raghava/hlp/pep_both.htm). Moreover, after modification of the lead compound, affinity of the peptides to human leukocyte antigen-A2 (HLA-A2) was determined by a flow cytometry and an inverted fluorescence microscope in T2 cells that show high expression of HLA-A2. The results demonstrated that the affinity of peptides II-4 and II-10 to HLA-A2 was significantly better when compared to others (II-Lead, II-1 ~ II-3, II-5 ~ II-9, II-11 ~ II-15). Further studies indicated that II-4 and II-10, especially II-4, significantly promoted the maturation of HLA-A2-positive human peripheral blood-derived dendritic cells (DCs) from morphology and surface markers, the activation of CD8 + T lymphocytes, and the type-specific killing effect on HLA-A2⁺/NY-ESO-1⁺ MDA-MB-231 cells. Molecular docking studies suggested a strong interaction between peptide II-4 and HLA-A2, thereby indicating that the II-4 is a promising candidate with antigenic potential in the field of immunotherapy that needs more studies.

Therapeutic ISCOMATRIX™ adjuvant vaccine elicits effective anti-tumor immunity in the TRAMP-C1 mouse model of prostate cancer

Cancer vaccine development has proven challenging with the exception of some virally induced cancers for which prophylactic vaccines exist. Currently, there is only one FDA approved vaccine for the treatment of prostate cancer and as such prostate cancer continues to present a significant unmet medical need. In this study, we examine the effectiveness of a therapeutic cancer vaccine that combines the ISCOMATRIX™ adjuvant (ISCOMATRIX) with the Toll-like receptor 3 agonist, polyinosinic-polycytidylic acid (Poly I:C), and Flt3L, FMS-like tyrosine kinase 3 ligand. We employed the TRAMP-C1 (transgenic adenocarcinoma of the mouse prostate) model of prostate cancer and the self-protein mPAP (prostatic acid phosphatase) as the tumor antigen. ISCOMATRIX™-mPAP-Poly I:C-Flt3L was delivered in a therapeutic prime-boost regime that was consistently able to achieve complete tumor regression in 60% of animals treated and these tumor-free animals were protected upon rechallenge. Investigations into the underlying immunological mechanisms contributing to the effectiveness of this vaccine identified that both innate and adaptive responses are elicited and required. NK cells, CD4⁺ T cells and interferon-γ were all found to be critical for tumor control while tumor infiltrating CD8⁺ T cells became disabled by an immunosuppressive microenvironment. There is potential for broader application of this cancer vaccine, as we have been able to demonstrate effectiveness in two additional cancer models; melanoma (B16-OVA) and a model of B cell lymphoma (Eµ-myc-GFP-OVA).

Innate Immune Stimulation in Cancer Therapy

The innate immune system has evolved as a first line of defense against invading pathogens and acts via classes of germline-encoded receptor systems to respond with proinflammatory cytokines. Innate immune cells, predominantly cells of the myeloid compartment, are capable of providing a potent basis for boosting adaptive immunity in malignant diseases. The authors review their current understanding of the molecular mechanisms whereby innate pattern recognition receptors participate in immunosurveillance of cancer cells. They discuss how innate effector mechanisms are currently being targeted pharmacologically and how improved understanding of the biology of these pathways is leading to novel immunotherapies of cancer.

Co-delivery of human cancer-testis antigens with adjuvant in protein nanoparticles induces higher cell-mediated immune responses

Nanoparticles have attracted considerable interest as cancer vaccine delivery vehicles for inducing sufficient CD8⁺ T cell-mediated immune responses to overcome the low immunogenicity of the tumor microenvironment. Our studies described here are the first to examine the effects of clinically-tested human cancer-testis (CT) peptide epitopes within a synthetic nanoparticle. Specifically, we focused on two significant clinical CT targets, the HLA-A2 restricted epitopes of NY-ESO-1 and MAGE-A3, using a viral-mimetic packaging strategy. Our data shows that simultaneous delivery of a NY-ESO-1 epitope (SLLMWITQV) and CpG using the E2 subunit assembly of pyruvate dehydrogenase (E2 nanoparticle), resulted in a 25-fold increase in specific IFN-γ secretion in HLA-A2 transgenic mice. This translated to a 15-fold increase in lytic activity toward target cancer cells expressing the antigen. Immunization with a MAGE-A3 epitope (FLWGPRALV) delivered with CpG in E2 nanoparticles yielded an increase in specific IFN-γ secretion and cell lysis by 6-fold and 9-fold, respectively. Furthermore, combined delivery of NY-ESO-1 and MAGE-A3 antigens in E2 nanoparticles yielded an additive effect that increased lytic activity towards cells bearing NY-ESO-1⁺ and MAGE-A3⁺. Our investigations demonstrate that formulation of CT antigens within a nanoparticle can significantly enhance antigen-specific cell-mediated responses, and the combination of the two antigens in a vaccine can preserve the increased individual responses that are observed for each antigen alone.

Melanoma: tumor microenvironment and new treatments

In the recent past years, many discoveries in the tumor microenvironment have led to changes in the management of melanoma and it is rising up hopes, specially, to those in advanced stages. FDA approved seven new drugs from 2011 to 2014. They are: Vemurafenib, Dabrafenib and Trametinib, kinases inhibitors used for patients that have BRAFV600E mutation; Ipilimumab (anti-CTLA4), Pembrolizumab (anti-PD-1) and Nivolumab (anti-PD-1), monoclonal antibodies that stimulate the immune system; and Peginterferon alfa-2b, an anti-proliferative cytokine used as adjuvant therapy. In this article, we will review the molecular bases for these new metastatic melanoma therapeutic agents cited above and also analyze new molecular discoveries in melanoma study, as Cancer-Testis antigens (CT). They are capable of induce humoral and cellular immune responses in cancer patients and because of this immunogenicity and their restrict expression in normal tissues, they are considered an ideal candidate for vaccine development against cancer. Among CT antigens, NY-ESO-1 is the best characterized in terms of expression patterns and immunogenicity. It is expressed in 20-40% of all melanomas, more in metastatic lesions than in primary ones, and it is very heterogeneous inter and intratumoral. Breslow index is associate with NY-ESO-1 expression in primary cutaneous melanomas, but its relation to patient survival remains controversial.

A pilot study of peripheral blood BDCA-1 (CD1c) positive dendritic cells pulsed with NY-ESO-1 ISCOMATRIX™ adjuvant

AIM

Pilot clinical trial of NY-ESO-1 (ESO) protein in ISCOMATRIX™ adjuvant pulsed onto peripheral blood dendritic cells (PBDC), to ascertain feasibility, evaluate toxicity and assess induction of ESO-specific immune responses.

PATIENTS & METHODS

Eligible participants had resected cancers expressing ESO or LAGE-1 and were at high risk of relapse. PBDC were produced using CliniMACS^®plus, with initial depletion of CD1c⁺ B cells followed by positive selection of CD1c⁺ PBDC. Patients received three intradermal vaccinations of ESO/IMX-pulsed PBDC at 4-week intervals.

RESULTS

The process was feasible and safe. No vaccine-induced immune responses were detected. Assays of immunomodulatory cells did not correlate with outcomes. One patient had a long lasting complete remission.

CONCLUSION

This method was feasible and safe but was minimally immunogenic.

Saponin-based adjuvants induce cross-presentation in dendritic cells by intracellular lipid body formation

Saponin-based adjuvants (SBAs) are being used in animal and human (cancer) vaccines, as they induce protective cellular immunity. Their adjuvant potency is a factor of inflammasome activation and enhanced antigen cross-presentation by dendritic cells (DCs), but how antigen cross-presentation is induced is not clear. Here we show that SBAs uniquely induce intracellular lipid bodies (LBs) in the CD11b+ DC subset in vitro and in vivo. Using genetic and pharmacological interference in models for vaccination and in situ tumour ablation, we demonstrate that LB induction is causally related to the saponin-dependent increase in cross-presentation and T-cell activation. These findings link adjuvant activity to LB formation, aid the application of SBAs as a cancer vaccine component, and will stimulate development of new adjuvants enhancing T-cell-mediated immunity.

Saponin-based adjuvants are being explored as vaccine components as they induce high levels of antigen cross-presentation, but it is unknown how. Here the authors show that these adjuvants enhance cross-presentation by driving production of lipid bodies inside CD11b dendritic cells.

Recombinant Lactobacillus plantarum induces immune responses to cancer testis antigen NY-ESO-1 and maturation of dendritic cells

Given their safe use in humans and inherent adjuvanticity, Lactic Acid Bacteria may offer several advantages over other mucosal delivery strategies for cancer vaccines. The objective of this study is to evaluate the immune responses in mice after oral immunization with Lactobacillus (L) plantarum WCFS1 expressing a cell-wall anchored tumor antigen NY-ESO-1. And to investigate the immunostimulatory potency of this new candidate vaccine on human dendritic cells (DCs). L. plantarum displaying NY-ESO-1 induced NY-ESO-1 specific antibodies and T-cell responses in mice. By contrast, L. plantarum displaying conserved proteins such as heat shock protein-27 and galectin-1, did not induce immunity, suggesting that immune tolerance to self-proteins cannot be broken by oral administration of L. plantarum. With respect to immunomodulation, immature DCs incubated with wild type or L. plantarum-NY-ESO-1 upregulated the expression of co-stimulatory molecules and secreted a large amount of interleukin (IL)-12, TNF-α, but not IL-4. Moreover, they upregulated the expression of immunosuppressive factors such as IL-10 and indoleamine 2,3-dioxygenase. Although L. plantarum-matured DCs expressed inhibitory molecules, they stimulated allogeneic T cells in-vitro. Collectively, the data indicate that L. plantarum-NY-ESO-1 can evoke antigen-specific immunity upon oral administration and induce DC maturation, raising the potential of its use in cancer immunotherapies.

Blockade of CTLA-4 promotes the development of effector CD8+ T lymphocytes and the therapeutic effect of vaccination with an attenuated protozoan expressing NY-ESO-1

The development of cancer immunotherapy has long been a challenge. Here, we report that prophylactic vaccination with a highly attenuated Trypanosoma cruzi strain expressing NY-ESO-1 (CL-14-NY-ESO-1) induces both effector memory and effector CD8(+) T lymphocytes that efficiently prevent tumor development. However, the therapeutic effect of such a vaccine is limited. We also demonstrate that blockade of Cytotoxic T Lymphocyte Antigen 4 (CTLA-4) during vaccination enhances the frequency of NY-ESO-1-specific effector CD8(+) T cells producing IFN-γ and promotes lymphocyte migration to the tumor infiltrate. As a result, therapy with CL-14-NY-ESO-1 together with anti-CTLA-4 is highly effective in controlling the development of an established melanoma.

Effective inhibition of melanoma tumorigenesis and growth via a new complex vaccine based on NY-ESO-1-alum-polysaccharide-HH2

Background

A safe and effective adjuvant plays an important role in the development of a vaccine. However, adjuvants licensed for administration in humans remain limited. Here, for the first time, we developed a novel combination adjuvant alum-polysaccharide-HH2 (APH) with potent immunomodulating activities, consisting of alum, polysaccharide of Escherichia coli and the synthetic cationic innate defense regulator peptide HH2.

Methods

The adjuvant effects of APH were examined using NY-ESO-1 protein-based vaccines in prophylactic and therapeutic models. We further determined the immunogenicity and anti-tumor effect of NY-ESO-1-APH (NAPH) vaccine using adoptive cellular/serum therapy in C57/B6 and nude mice. Cell-mediated and antibody-mediated immune responses were evaluated.

Results

The APH complex significantly promoted antigen uptake, maturation and cross-presentation of dendritic cells and enhanced the secretion of TNF-α, MCP-1 and IFN-γ by human peripheral blood mononuclear cells compared with individual components. Vaccination of NAPH resulted in significant tumor regression or delayed tumor progression in prophylactic and therapeutic models. In addition, passive serum/cellular therapy potently inhibited tumor growth of NY-ESO-1-B16. Mice treated with NAPH vaccine produced higher antibody titers and greater antibody-dependent/independent cellular cytotoxicity. Therefore, NAPH vaccination effectively stimulated innate immunity, and boosted both arms of the adaptive humoral and cellular immune responses to suppress tumorigenesis and growth of melanoma.

Conclusions

Our study revealed the potential application of APH complex as a novel immunomodulatory agent for vaccines against tumor refractory and growth.

Evolving role of tumor antigens for future melanoma therapies

ABSTRACT: 

Human tumor rejection antigens recognized by T lymphocytes were first defined in the early 1990s and the identification of shared tumor-restricted antigens sparked hopes for the development of a therapeutic vaccination to treat cancer, including melanoma. Despite decades of intense preclinical and clinical research, the success of anticancer vaccines based on these antigens has been limited. While melanoma is a highly immunogenic tumor, the ability to prime immunity with vaccines has not generally translated into objective disease regression. However, with the development of small molecules targeting oncogenic proteins, such as V600-mutated BRAF, and immune checkpoint inhibitors with demonstrable long-lasting clinical benefit, new opportunities for antigen-targeted directed therapies are emerging.

Applications of nanotechnology for immunology

Nanotechnology uses the unique properties of objects that function as a unit within the overall size range of 1-1,000 nanometres. The engineering of nanostructure materials, including nanoparticles, nanoemulsions or nanotubules, holds great promise for the development of new immunomodulatory agents, as such nanostructures can be used to more effectively manipulate or deliver immunologically active components to target sites. Successful applications of nanotechnology in the field of immunology will enable new generations of vaccines, adjuvants and immunomodulatory drugs that aim to improve clinical outcomes in response to a range of infectious and non-infectious diseases.

Serum cytokine profiles associated with specific adjuvants used in a DNA prime-protein boost vaccination strategy

In recent years, heterologous prime-boost vaccines have been demonstrated to be an effective strategy for generating protective immunity, consisting of both humoral and cell-mediated immune responses against a variety of pathogens including HIV-1. Previous reports of preclinical and clinical studies have shown the enhanced immunogenicity of viral vector or DNA vaccination followed by heterologous protein boost, compared to using either prime or boost components alone. With such approaches, the selection of an adjuvant for inclusion in the protein boost component is expected to impact the immunogenicity and safety of a vaccine. In this study, we examined in a mouse model the serum cytokine and chemokine profiles for several candidate adjuvants: QS-21, Al(OH)3, monophosphoryl lipid A (MPLA) and ISCOMATRIX™ adjuvant, in the context of a previously tested pentavalent HIV-1 Env DNA prime-protein boost formulation, DP6-001. Our data revealed that the candidate adjuvants in the context of the DP6-001 formulation are characterized by unique serum cytokine and chemokine profiles. Such information will provide valuable guidance in the selection of an adjuvant for future AIDS vaccine development, with the ultimate goal of enhancing immunogenicity while minimizing reactogenicity associated with the use of an adjuvant. More significantly, results reported here will add to the knowledge on how to include an adjuvant in the context of a heterologous prime-protein boost vaccination strategy in general.

A cancer vaccine induces expansion of NY-ESO-1-specific regulatory T cells in patients with advanced melanoma

Cancer vaccines are designed to expand tumor antigen-specific T cells with effector function. However, they may also inadvertently expand regulatory T cells (Treg), which could seriously hamper clinical efficacy. To address this possibility, we developed a novel assay to detect antigen-specific Treg based on down-regulation of surface CD3 following TCR engagement, and used this approach to screen for Treg specific to the NY-ESO-1 tumor antigen in melanoma patients treated with the NY-ESO-1/ISCOMATRIX^TM cancer vaccine. All patients tested had Treg (CD25^bright FoxP3⁺ CD127^neg) specific for at least one NY-ESO-1 epitope in the blood. Strikingly, comparison with pre-treatment samples revealed that many of these responses were induced or boosted by vaccination. The most frequently detected response was toward the HLA-DP4-restricted NY-ESO-1_157–170 epitope, which is also recognized by effector T cells. Notably, functional Treg specific for an HLA-DR-restricted epitope within the NY-ESO-1_115–132 peptide were also identified at high frequency in tumor tissue, suggesting that NY-ESO-1-specific Treg may suppress local anti-tumor immune responses. Together, our data provide compelling evidence for the ability of a cancer vaccine to expand tumor antigen-specific Treg in the setting of advanced cancer, a finding which should be given serious consideration in the design of future cancer vaccine clinical trials.

A novel HLA-B18 restricted CD8+ T cell epitope is efficiently cross-presented by dendritic cells from soluble tumor antigen

NY-ESO-1 has been a major target of many immunotherapy trials because it is expressed by various cancers and is highly immunogenic. In this study, we have identified a novel HLA-B*1801-restricted CD8⁺ T cell epitope, NY-ESO-1_88–96 (LEFYLAMPF) and compared its direct- and cross-presentation to that of the reported NY-ESO-1_157–165 epitope restricted to HLA-A*0201. Although both epitopes were readily cross-presented by DCs exposed to various forms of full-length NY-ESO-1 antigen, remarkably NY-ESO-1_88–96 is much more efficiently cross-presented from the soluble form, than NY-ESO-1_157–165. On the other hand, NY-ESO-1_157–165 is efficiently presented by NY-ESO-1-expressing tumor cells and its presentation was not enhanced by IFN-γ treatment, which induced immunoproteasome as demonstrated by Western blots and functionally a decreased presentation of Melan A_26–35; whereas NY-ESO-1_88–96 was very inefficiently presented by the same tumor cell lines, except for one that expressed high level of immunoproteasome. It was only presented when the tumor cells were first IFN-γ treated, followed by infection with recombinant vaccinia virus encoding NY-ESO-1, which dramatically increased NY-ESO-1 expression. These data indicate that the presentation of NY-ESO-1_88–96 is immunoproteasome dependent. Furthermore, a survey was conducted on multiple samples collected from HLA-B18⁺ melanoma patients. Surprisingly, all the detectable responses to NY-ESO-1_88–96 from patients, including those who received NY-ESO-1 ISCOMATRIX™ vaccine were induced spontaneously. Taken together, these results imply that some epitopes can be inefficiently presented by tumor cells although the corresponding CD8⁺ T cell responses are efficiently primed in vivo by DCs cross-presenting these epitopes. The potential implications for cancer vaccine strategies are further discussed.

Trypanosoma cruzi adjuvants potentiate T cell-mediated immunity induced by a NY-ESO-1 based antitumor vaccine

Immunological adjuvants that induce T cell-mediate immunity (TCMI) with the least side effects are needed for the development of human vaccines. Glycoinositolphospholipids (GIPL) and CpGs oligodeoxynucleotides (CpG ODNs) derived from the protozoa parasite Trypanosoma cruzi induce potent pro-inflammatory reaction through activation of Toll-Like Receptor (TLR)4 and TLR9, respectively. Here, using mouse models, we tested the T. cruzi derived TLR agonists as immunological adjuvants in an antitumor vaccine. For comparison, we used well-established TLR agonists, such as the bacterial derived monophosphoryl lipid A (MPL), lipopeptide (Pam3Cys), and CpG ODN. All tested TLR agonists were comparable to induce antibody responses, whereas significant differences were noticed in their ability to elicit CD4(+) T and CD8(+) T cell responses. In particular, both GIPLs (GTH, and GY) and CpG ODNs (B344, B297 and B128) derived from T. cruzi elicited interferon-gamma (IFN-γ) production by CD4(+) T cells. On the other hand, the parasite derived CpG ODNs, but not GIPLs, elicited a potent IFN-γ response by CD8(+) T lymphocytes. The side effects were also evaluated by local pain (hypernociception). The intensity of hypernociception induced by vaccination was alleviated by administration of an analgesic drug without affecting protective immunity. Finally, the level of protective immunity against the NY-ESO-1 expressing melanoma was associated with the magnitude of both CD4(+) T and CD8(+) T cell responses elicited by a specific immunological adjuvant.

ISCOMATRIX: a novel adjuvant for use in prophylactic and therapeutic vaccines against infectious diseases

The ISCOMATRIX adjuvant has antigen delivery and presentation properties as well as immunomodulatory capabilities, which combine to provide enhanced and accelerated immune responses. The responses are broad, including a range of subclasses of antibodies as well as CD4(+) and CD8(+) T-cells. A range of ISCOMATRIX vaccines (ISCOMATRIX adjuvant combined with antigen) have now been tested in clinical trials and have been shown to be generally safe and well tolerated as well as immunogenic, generating both antibody (Ab) and T-cell responses. The mechanisms by which ISCOMATRIX adjuvant facilitates its immune effects are the scope of significant study and indicate that ISCOMATRIX adjuvant (i) rapidly traffics antigen into the cytosol of multiple dendritic cell subsets, (ii) induces the induction of an array of cytokines and chemokines and (iii) links the innate and adaptive immune responses in vivo in a Toll-like-receptor-independent but MyD88-dependent manner. These data highlight the clinical utility of ISCOMATRIX adjuvant in the development of prophylactic and therapeutic vaccines for infectious disease.

Trypanosoma cruzi as an effective cancer antigen delivery vector

One of the main challenges in cancer research is the development of vaccines that induce effective and long-lived protective immunity against tumors. Significant progress has been made in identifying members of the cancer testis antigen family as potential vaccine candidates. However, an ideal form for antigen delivery that induces robust and sustainable antigen-specific T-cell responses, and in particular of CD8(+) T lymphocytes, remains to be developed. Here we report the use of a recombinant nonpathogenic clone of Trypanosoma cruzi as a vaccine vector to induce vigorous and long-term T cell-mediated immunity. The rationale for using the highly attenuated T. cruzi clone was (i) the ability of the parasite to persist in host tissues and therefore to induce a long-term antigen-specific immune response; (ii) the existence of intrinsic parasite agonists for Toll-like receptors and consequent induction of highly polarized T helper cell type 1 responses; and (iii) the parasite replication in the host cell cytoplasm, leading to direct antigen presentation through the endogenous pathway and consequent induction of antigen-specific CD8(+) T cells. Importantly, we found that parasites expressing a cancer testis antigen (NY-ESO-1) were able to elicit human antigen-specific T-cell responses in vitro and solid protection against melanoma in a mouse model. Furthermore, in a therapeutic protocol, the parasites expressing NY-ESO-1 delayed the rate of tumor development in mice. We conclude that the T. cruzi vector is highly efficient in inducing T cell-mediated immunity and protection against cancer cells. More broadly, this strategy could be used to elicit a long-term T cell-mediated immunity and used for prophylaxis or therapy of chronic infectious diseases.

Melanoma vaccines: developments over the past 10 years

Decades of preclinical evaluation and clinical trials into melanoma vaccines have yielded spectacular progress in our understanding of melanoma antigens and the immune mechanisms of tumor rejection. Key insights and the results of their clinical evaluation are reviewed in this article. Unfortunately, durable clinical benefit following vaccination remains uncommon. Two recent clinical advances that will impact on melanoma vaccine development are trials with inhibitors of CTLA-4 and oncogenic BRAF. Long-term therapeutic control of melanoma will require integration of specific active immunotherapy with these emerging successful therapies from the disparate fields of immune regulation and signal transduction.

ISCOMATRIX vaccines mediate CD8+ T-cell cross-priming by a MyD88-dependent signaling pathway

Generating a cytotoxic CD8⁺ T-cell response that can eradicate malignant cells is the primary objective of cancer vaccine strategies. In this study we have characterized the innate and adaptive immune response to the ISCOMATRIX adjuvant, and the ability of vaccine antigens formulated with this adjuvant to promote antitumor immunity. ISCOMATRIX adjuvant led to a rapid innate immune cell response at the injection site, followed by the activation of natural killer and dendritic cells (DC) in regional draining lymph nodes. Strikingly, major histocompatibility complex (MHC) class I cross-presentation by CD8α⁺ and CD8α⁻ DCs was enhanced by up to 100-fold when antigen was formulated with ISCOMATRIX adjuvant. These coordinated features enabled efficient CD8⁺ T-cell cross-priming, which exhibited prophylactic and therapeutic tumoricidal activity. The therapeutic efficacy of an ISCOMATRIX vaccine was further improved when co-administered with an anti-CD40 agonist antibody, suggesting that ISCOMATRIX-based vaccines may combine favorably with other immune modifiers in clinical development to treat cancer. Finally, we identified a requirement for the myeloid differentiation primary response gene 88 (MyD88) adapter protein for both innate and adaptive immune responses to ISCOMATRIX vaccines in vivo. Taken together, our findings support the utility of the ISCOMATRIX adjuvant for use in the development of novel vaccines, particularly those requiring strong CD8⁺ T-cell immune responses, such as therapeutic cancer vaccines.

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.

Enhancement of dendritic cells as vaccines for cancer

Dendritic cells are the most potent antigen-presenting cells known; owing to their ability to stimulate antigen-specific cytolytic and memory T-cell responses, their use as cancer vaccines is rapidly increasing. While clinical trials provide evidence that dendritic cells vaccines are safe and elicit immunological responses in most patients, few complete tumor remissions have been reported and further technological advances are required. An effective dendritic cell vaccine must possess and maintain several characteristics: it must migrate to lymph nodes, have a mature, Th1-polarizing phenotype expressed stably after infusion and present antigen for sufficient time to produce a T-cell response capable of eliminating a tumor. While dendritic cells are readily matured ex vivo, their phenotype and fate after infusion are rarely evaluable; therefore, strategies to ensure that dendritic cells access lymphoid tissues and retain an immunostimulatory phenotype are required. In order to best exploit dendritic cells as vaccines, they may require genetic modification and combination with other strategies including adoptive T-cell transfer, inhibition of regulatory T cells or modulation of inflammatory pathways.

NY-ESO-1 protein glycosylated by yeast induces enhanced immune responses

Vaccine strategies that target dendritic cells to elicit potent cellular immunity are the subject of intense research. Here we report that the genetically engineered yeast Saccharomyces cerevisiae, expressing the full-length tumour-associated antigen NY-ESO-1, is a versatile host for protein production. Exposing dendritic cells (DCs) to soluble NY-ESO-1 protein linked to the yeast a-agglutinin 2 protein (Aga2p) protein resulted in protein uptake, processing and MHC class I cross-presentation of NY-ESO-1-derived peptides. The process of antigen uptake and cross-presentation was dependent on the glycosylation pattern of NY-ESO-1-Aga2p protein and the presence of accessible mannose receptors. In addition, NY-ESO-1-Aga2p protein uptake by dendritic cells resulted in recognition by HLA-DP4 NY-ESO-1-specific CD4(+) T cells, indicating MHC class II presentation. Finally, vaccination of mice with yeast-derived NY-ESO-1-Aga2p protein led to an enhanced humoral and cellular immune response, when compared to the bacterially expressed NY-ESO-1 protein. Together, these data demonstrate that yeast-derived full-length NY-ESO-1-Aga2p protein is processed and presented efficiently by MHC class I and II complexes and warrants clinical trials to determine the potential value of S. cerevisiae as a host for cancer vaccine development.

An ISCOM vaccine combined with a TLR9 agonist breaks immune evasion mediated by regulatory T cells in an orthotopic model of pancreatic carcinoma

Vaccines based on immune stimulatory complexes (ISCOM) induce T-cell responses against tumor antigen (Ag). However, immune responses are impaired in pancreatic cancer patients. We investigated the efficacy of an ISCOM vaccine in a murine pancreatic carcinoma model. Panc02 cells expressing OVA as a model Ag were induced subcutaneously or orthotopically in the pancreas of C57BL/6 mice. Treatment consisted of an OVA containing ISCOM vaccine, either used alone or in combination with the TLR9 agonist CpG. The ISCOM vaccine effectively induced Ag-specific CTL capable of killing tumor cells. However, in mice with established tumors CTL induction by the vaccine was inefficient and did not affect tumor growth. Lack of efficacy correlated with increased numbers of Treg. Depletion of Treg with anti-CD25 mAb restored CTL induction and prolonged survival. Adding low-dose CpG to the ISCOM vaccine reduced Treg numbers, enhanced CTL responses and induced regression of pancreatic tumors in a CD8(+) T cell-dependent manner. Mice cured from the primary tumor mounted a memory T-cell response against wild-type Panc02 tumors, indicative of epitope spreading. Combining ISCOM vaccines with TLR agonists is a promising strategy for breaking tumor immune evasion and deserves further evaluation for the treatment of pancreatic carcinoma.

Cancer-testis antigen expression in primary cutaneous melanoma has independent prognostic value comparable to that of Breslow thickness, ulceration and mitotic rate

To determine the effect of Cancer-Testis Antigen (CTAg) expression on the natural history of primary cutaneous melanoma we compared its impact on prognosis with that of known prognostic factors and its relationship with other clinicopathologic characteristics. The immunohistochemical expression of three CTAgs (MAGE-A1, MAGE-A4 and NY-ESO-1) in 348 cases of stage I and stage II primary cutaneous melanoma was analysed and correlated with clinicopathologic characteristics, relapse free survival (RFS) and overall survival (OS). A Cox proportional hazards regression model was used to analyse factors which independently predicted RFS. All three CTAgs were significantly co-expressed with each other (p < 0.001). The median RFS for patients with CTAg-negative tumours and CTAg-positive tumours was 72 months and 45 months, respectively, (P = 0.008). Univariate analysis demonstrated that the impact of CTAg expression on RFS was comparable in magnitude to that of Breslow thickness, ulceration and tumour mitotic rate. Multivariate Cox regression analysis indicated that CTAg expression was a powerful independent predictor of RFS (risk ratio (RR) = 1.715, 95% confidence interval (CI) = 0.430-0.902, P = 0.010). In contrast, CTAg expression was demonstrated to have no prognostic impact on overall survival. This study demonstrates that CTAg expression in primary cutaneous melanoma is a strong independent predictor of RFS and it is comparable to other known important prognostic factors. CTAg expression has no relationship with overall survival, suggesting anti-melanoma immunity directed towards CTAg expression may contribute to the natural history of the disease. In view of these results, further investigation of the function of CTAgs and their potential use in therapeutic targeting is warranted.

Cancer-germline antigen vaccines and epigenetic enhancers: future strategies for cancer treatment

IMPORTANCE OF THE FIELD

Immunotherapy holds great potential for disseminated cancer, and cancer-germline (CG) antigens are among the most promising tumor targets. They are widely expressed in different cancer types and are essentially tumor-specific, since their expression in normal tissues is largely restricted to immune-privileged sites. Although the therapeutic potential of these antigens may be compromised by their highly heterogeneous expression in many tumors and low frequency in some cancers, recent developments suggest that tumor-cell-selective enhancement of CG antigen gene expression can be achieved using epigenetic modifiers.

AREAS COVERED IN THIS REVIEW

We provide an overview of the potential of CG antigens as targets for cancer immunotherapy, including advantages and disadvantages. We also discuss the current state of development of CG antigen vaccines, and the potential synergistic effect of combining CG antigen immunotherapeutic strategies with epigenetic modifiers.

WHAT THE READER WILL GAIN

The reader will gain an overview of the past, present and future role of CG antigens in cancer immunotherapy.

TAKE HOME MESSAGE

Chemoimmunotherapy using epigenetic drugs and CG antigen vaccines may be a useful approach for treating cancer.

Linear and branched glyco-lipopeptide vaccines follow distinct cross-presentation pathways and generate different magnitudes of antitumor immunity

BACKGROUND

Glyco-lipopeptides, a form of lipid-tailed glyco-peptide, are currently under intense investigation as B- and T-cell based vaccine immunotherapy for many cancers. However, the cellular and molecular mechanisms of glyco-lipopeptides (GLPs) immunogenicity and the position of the lipid moiety on immunogenicity and protective efficacy of GLPs remain to be determined.

METHODS/PRINCIPAL FINDINGS

We have constructed two structural analogues of HER-2 glyco-lipopeptide (HER-GLP) by synthesizing a chimeric peptide made of one universal CD4(+) epitope (PADRE) and one HER-2 CD8(+) T-cell epitope (HER(420-429)). The C-terminal end of the resulting CD4-CD8 chimeric peptide was coupled to a tumor carbohydrate B-cell epitope, based on a regioselectively addressable functionalized templates (RAFT), made of four alpha-GalNAc molecules. The resulting HER glyco-peptide (HER-GP) was then linked to a palmitic acid moiety, attached either at the N-terminal end (linear HER-GLP-1) or in the middle between the CD4+ and CD8+ T cell epitopes (branched HER-GLP-2). We have investigated the uptake, processing and cross-presentation pathways of the two HER-GLP vaccine constructs, and assessed whether the position of linkage of the lipid moiety would affect the B- and T-cell immunogenicity and protective efficacy. Immunization of mice revealed that the linear HER-GLP-1 induced a stronger and longer lasting HER(420-429)-specific IFN-gamma producing CD8(+) T cell response, while the branched HER-GLP-2 induced a stronger tumor-specific IgG response. The linear HER-GLP-1 was taken up easily by dendritic cells (DCs), induced stronger DCs maturation and produced a potent TLR- 2-dependent T-cell activation. The linear and branched HER-GLP molecules appeared to follow two different cross-presentation pathways. While regression of established tumors was induced by both linear HER-GLP-1 and branched HER-GLP-2, the inhibition of tumor growth was significantly higher in HER-GLP-1 immunized mice (p<0.005).

SIGNIFICANCE

These findings have important implications for the development of effective GLP based immunotherapeutic strategies against cancers.

Processing and cross-presentation of individual HLA-A, -B, or -C epitopes from NY-ESO-1 or an HLA-A epitope for Melan-A differ according to the mode of antigen delivery

The ability of dendritic cells (DCs) to cross-present protein tumor antigens to cytotoxic T lymphocytes (CTLs) underpins the success of therapeutic cancer vaccines. We studied cross-presentation of the cancer/testis antigen, NY-ESO-1, and the melanoma differentiation antigen, Melan-A by human DC subsets. Monocyte-derived DCs (MoDCs) efficiently cross-presented human leukocyte associated (HLA)-A2-restricted epitopes from either a formulated NY-ESO-1/ISCOMATRIX vaccine or when either antigen was mixed with ISCOMATRIX adjuvant. HLA-A2 epitope generation required endosomal acidification and was proteasome-independent for NY-ESO-1 and proteasome-dependent for Melan-A. Both MoDCs and CD1c(+) blood DCs cross-presented NY-ESO-1-specific HLA-A2(157-165)-, HLA-B7(60-72)-, and HLA-Cw3(92-100)-restricted epitopes when formulated as an NY-ESO-1/ISCOMATRIX vaccine, but this was limited when NY-ESO-1 and ISCOMATRIX adjuvant were added separately to the DC cultures. Finally, cross-presentation of NY-ESO-1(157-165)/HLA-A2, NY-ESO-1(60-72)/HLA-B7, and NY-ESO-1(92-100)/HLA-Cw3 epitopes was proteasome-dependent when formulated as immune complexes (ICs) but only proteasome-dependent for NY-ESO-1(60-72)/HLA-B7-restricted cross-presentation facilitated by ISCOMATRIX adjuvant. We demonstrate, for the first time, proteasome-dependent and independent cross-presentation of HLA-A-, B-, and C-restricted epitopes within the same full-length tumor antigen by human DCs. Our findings identify important differences in the capacities of human DC subsets to cross-present clinically relevant, full-length tumor antigens and how vaccine formulation impacts CTL responses in vivo.

Immunomodulation in endometrial cancer

Endometrial cancer is the most frequent gynecological cancer and the fourth most common cancer in women in the developed world. Over the last decade, immunotherapy has been the focus of intense investigation as a form of cancer treatment whereby the treatment initiates a host immune response ultimately eradicating the tumor. It has been suggested that in endometrial cancer and many other forms of cancer, immunosuppression poses a significant obstacle at inducing antitumor immunity by immunotherapy. This review will look at the different studies that have identified immunomodulation of T cells, cytokines and macrophages, and regulation of apoptotic and angiogenic factors in endometrial cancer patients that may contribute to the inefficiency of immunotherapy.

Promises and Limitations of Murine Models in the Development of Anticancer T-Cell Vaccines

Murine models have been instrumental in defining the basic mechanisms of antitumor immunity. Most of these mechanisms have since been shown to operate in humans as well. Based on these similarities, active vaccination strategies aimed at eliciting antitumor T-cell responses have been elaborated and successfully implemented in various mouse models. However, the results of human antitumor vaccination trials have been rather disappointing thus far. This review summarizes the different experimental approaches used in mice to induce antitumor T-cell responses and identifies some critical parameters that should be considered when evaluating results from murine models.

The Tat-conjugated N-terminal region of mucin antigen 1 (MUC1) induces protective immunity against MUC1-expressing tumours

Mucin antigen 1 (MUC1) is overexpressed on various human adenocarcinomas and haematological malignancies and has long been used as a target antigen for cancer immunotherapy. Most of the preclinical and clinical studies using MUC1 have used the tandem repeat region of MUC1, which could be presented by only a limited set of major histocompatibility complex haplotypes. Here, we evaluated N-terminal region (2-147 amino acids) of MUC1 (MUC1-N) for dendritic cell (DC)-based cancer immunotherapy. We used Esherichia coli-derived MUC1-N that was fused to the protein transduction domain of human immunodeficiency virus Tat protein for three reasons. First, mature DCs do not phagocytose soluble protein antigens. Secondly, tumour cells express underglycosylated MUC1, which can generate epitopes repertoire that differs from normal cells, which express hyperglycosylated MUC1. Finally, aberrantly glycosylated MUC1 has been known to impair DC function. In our study, Tat-MUC1-N-loaded DCs induced type 1 T cell responses as well as cytotoxic T lymphocytes efficiently. Furthermore, they could break tolerance in the transgenic breast tumour mouse model, where MUC1-positive breast cancers grow spontaneously. Compared with DCs pulsed with unconjugated MUC1-N, DCs loaded with Tat-conjugated MUC1-N could delay tumour growth more effectively in the transgenic tumour model as well as in the tumour injection model. These results suggest that the recombinant N-terminal part of MUC1, which may provide a diverse epitope repertoire, could be utilized as an effective tumour antigen for DC-based cancer immunotherapy.

ISCOMs and ISCOMATRIX

Immunostimulatory complexes (ISCOMs) are particulate antigen delivery systems composed of antigen, cholesterol, phospholipid and saponin, while ISCOMATRIX is a particulate adjuvant comprising cholesterol, phospholipid and saponin but without antigen. The combination of an antigen with ISCOMATRIX is called an ISCOMATRIX vaccine. ISCOMs and ISCOMATRIX combine the advantages of a particulate carrier system with the presence of an in-built adjuvant (Quil A) and consequently have been found to be more immunogenic, while removing its haemolytic activity of the saponin, producing less toxicity. ISCOMs and ISCOMATRIX vaccines have now been shown to induce strong antigen-specific cellular or humoral immune responses to a broad range of antigens of viral, bacterial, parasite origin or tumor in a number of animal species including non-human primates and humans. These vaccines produced by well controlled and reproducible processes have also been evaluated in human clinical trials. In this review, we summarize the recent progress of ISCOMs and ISCOMATRIX, including preparation technology as well as their application in humans and veterinary vaccine designs with particular emphasis on the current understanding of the properties and features of ISCOMs and ISCOMATRIX vaccines to induce immune responses. The mechanisms of adjuvanticity are also discussed in the light of recent findings.

Development of prophylactic and therapeutic vaccines using the ISCOMATRIX adjuvant

Adjuvants are components that when added to subunit antigen (Ag) vaccines boost their immunogenicity and thus immune efficacy. However, there are few adjuvants that are approved for clinical use resulting in a critical need for the development of safe and effective adjuvants for use in both prophylactic and therapeutic vaccines. The paucity of appropriate adjuvants is more chronic for the development of therapeutic vaccines for cancer and chronic infectious disease, which need to induce cytotoxic T-cell responses via cross-presentation of the vaccine Ag by dendritic cells. The ISCOMATRIX adjuvant represents a unique adjuvant system that facilitates Ag delivery and presentation as well as immunomodulation to provide enhanced and accelerated immune responses. The immune responses generated are of broad specificity to the vaccine Ag, and include robust antibody responses of multiple subclasses as well as both CD4(+) and CD8(+) T-cell responses. Here we discuss our understanding of the mechanisms of action by which ISCOMATRIX adjuvant may facilitate these integrated immune responses and touch on insights gained through its clinical experience.

ISCOMATRIX adjuvant induces efficient cross-presentation of tumor antigen by dendritic cells via rapid cytosolic antigen delivery and processing via tripeptidyl peptidase II

Cancer vaccines aim to induce antitumor CTL responses, which require cross-presentation of tumor Ag to CTLs by dendritic cells (DCs). Adjuvants that facilitate cross-presentation of vaccine Ag are therefore key for inducing antitumor immunity. We previously reported that human DCs could not efficiently cross-present the full-length cancer/testis Ag NY-ESO-1 to CTL unless formulated as either an immune complex (NY-ESO-1/IC) or with ISCOMATRIX adjuvant. We now demonstrate that NY-ESO-1/ICs induce cross-presentation of HLA-A2- and HLA-Cw3-restricted epitopes via a proteasome-dependent pathway. In contrast, cross-presentation of NY-ESO-1/ISCOMATRIX vaccine was proteasome independent and required the cytosolic protease tripeptidyl peptidase II. Trafficking studies revealed that uptake of ICs and ISCOMATRIX vaccine by DCs occurred via endocytosis with delivery to lysosomes. Interestingly, ICs were retained in lysosomes, whereas ISCOMATRIX adjuvant induced rapid Ag translocation into the cytosol. Ag translocation was dependent on endosomal acidification and IL-4-driven differentiation of monocytes into DCs. This study demonstrates that Ag formulation determines Ag processing and supports a role for tripeptidyl peptidase II in cross-presentation of CTL epitopes restricted to diverse HLA alleles.

Nanoparticles for nasal vaccination

The great interest in mucosal vaccine delivery arises from the fact that mucosal surfaces represent the major site of entry for many pathogens. Among other mucosal sites, nasal delivery is especially attractive for immunization, as the nasal epithelium is characterized by relatively high permeability, low enzymatic activity and by the presence of an important number of immunocompetent cells. In addition to these advantageous characteristics, the nasal route could offer simplified and more cost-effective protocols for vaccination with improved patient compliance. The use of nanocarriers provides a suitable way for the nasal delivery of antigenic molecules. Besides improved protection and facilitated transport of the antigen, nanoparticulate delivery systems could also provide more effective antigen recognition by immune cells. These represent key factors in the optimal processing and presentation of the antigen, and therefore in the subsequent development of a suitable immune response. In this sense, the design of optimized vaccine nanocarriers offers a promising way for nasal mucosal vaccination.

Antitumor activity of a self-adjuvanting glyco-lipopeptide vaccine bearing B cell, CD4+ and CD8+ T cell epitopes

Molecularly defined synthetic vaccines capable of inducing both antibodies and cellular anti-tumor immune responses, in a manner compatible with human delivery, are limited. Few molecules achieve this target without utilizing external immuno-adjuvants. In this study, we explored a self-adjuvanting glyco-lipopeptide (GLP) as a platform for cancer vaccines using as a model MO5, an OVA-expressing mouse B16 melanoma. A prototype B and T cell epitope-based GLP molecule was constructed by synthesizing a chimeric peptide made of a CD8(+) T cell epitope, from ovalbumin (OVA(257-264)) and an universal CD4(+) T helper (Th) epitope (PADRE). The resulting CTL-Th peptide backbones was coupled to a carbohydrate B cell epitope based on a regioselectively addressable functionalized templates (RAFT), made of four alpha-GalNAc molecules at C-terminal. The N terminus of the resulting glycopeptides (GP) was then linked to a palmitic acid moiety (PAM), obviating the need for potentially toxic external immuno-adjuvants. The final prototype OVA-GLP molecule, delivered in adjuvant-free PBS, in mice induced: (1) robust RAFT-specific IgG/IgM that recognized tumor cell lines; (2) local and systemic OVA(257-264)-specific IFN-gamma producing CD8(+) T cells; (3) PADRE-specific CD4(+) T cells; (4) OVA-GLP vaccination elicited a reduction of tumor size in mice inoculated with syngeneic murine MO5 carcinoma cells and a protection from lethal carcinoma cell challenge; (5) finally, OVA-GLP immunization significantly inhibited the growth of pre-established MO5 tumors. Our results suggest self-adjuvanting glyco-lipopeptide molecules as a platform for B Cell, CD4(+), and CD8(+) T cell epitopes-based immunotherapeutic cancer vaccines.

Dendritic cell-based cancer vaccination: quo vadis?

Dendritic cells (DCs) play a central role in the initiation and regulation of primary immune responses. DCs loaded with tumor-associated antigens induce anti-tumoral cytotoxic T cells in vitro and in vivo. However, clinical trials using ex vivo-generated DCs have failed to demonstrate clinical efficacy. This review summarizes recent advances in concepts and techniques that are providing new impulses to DC-based cancer vaccination. Improvements in protocols for ex vivo-generation of DCs, innovations in immunomonitoring, strategies to overcome tumor-induced immunosuppression and insights into the mutual beneficial effects of vaccines and chemotherapy are all considered. Furthermore, we highlight novel developments in cell-free vaccines targeting DCs in vivo.