Potential Cancer Vaccine Research Articles

A tumor lysate is an effective vaccine antigen for the stimulation of CD4+ T-cell function and subsequent induction of antitumor immunity mediated by CD8+ T cells

To develop a potent cancer vaccine, it is important to study how to prepare highly immunogenic antigens and to identify the most appropriate adjuvants for the antigens. Here we show that a tumor lysate works as an effective antigen to prime CD4+ T-cell help when baculovirus is employed as an adjuvant. When immunized intradermally with the combination (BLP) of baculovirus, a CT26 tumor lysate, and a cytotoxic T-cell epitope peptide before a tumor challenge, 60% of mice rejected tumors. In contrast, all mice vaccinated with baculovirus plus a tumor lysate (BL) developed tumors. In addition, flow cytometry showed that tumor-specific, interferon γ-producing CD8+ cytotoxic T lymphocytes (CTLs) were robustly activated by intradermal immunization with BLP. When BLP was administered therapeutically to tumor-bearing mice, antitumor efficacy was better compared to BL. The established tumor was completely eradicated in 50–60% of BLP-treated mice, and induction of tumor-specific CTLs was observed, suggesting that the antitumor efficacy of BLP is mediated by CD8+ T cells. Numerous CD4+ T cells infiltrated the tumors of BLP-treated mice, whereas the antitumor effect of BLP almost disappeared after removal of the tumor lysate from BLP or after depletion of BLP-immunized mice of CD4+ T cells. Thus, the combination of a peptide, lysate, and baculovirus provides stronger antitumor immunity than does a peptide plus baculovirus or a lysate plus baculovirus; effectiveness of BLP is determined by functioning of CD4+ T cells stimulated with a tumor lysate.

Abstract LB-236: Imprime PGG conjugated directly to protein enables cross-presentation of antigen that generates multifunctional cytotoxic T cells

Abstract Imprime PGG is a soluble yeast-derived β-1,3/1,6 glucan innate immune cell modulator that is in phase 3 and multiple phase 2 clinical trials in combination with complement activating monoclonal antibodies (e.g. bevacizumab, cetuximab). We have previously shown that Imprime binds to complement receptors and modulates the function of a variety of immune cells, including monocytes, neutrophils, and B cells. We have also demonstrated that Imprime PGG binds to various subsets of dendritic cells (DCs) and can cause intermediate upregulation of MHC class II and the co-stimulatory molecules CD80/86 critical for antigen presentation and T cell activation. Based on these findings, we hypothesized that Imprime PGG conjugated to a protein would efficiently deliver antigen to DCs and prime a cytotoxic CD8+ T cell response. To test this hypothesis, we employed the model antigen chicken ovalbumin (OVA) in a C57BL/6 mouse model to examine the generation of OVA-specific CD8+ T cell responses. We covalently linked OVA to Imprime PGG to generate a β-glucan/protein conjugate (Imprime-OVA). Using T cell receptor transgenic OT-I CD8+ T cells to track responses to OVA, we treated mice with Imprime-OVA intravenously and examined the expansion and functional quality of the T cell response 7 days later at the peak of expansion. Following Imprime-OVA treatment, OVA-specific CD8 T cells underwent vigorous expansion, upregulated the transcription factor Tbet, which is central to developing effector functions, and gained the ability to produce the cytokines IFN-γ, TNF-α and IL-2. By comparison, OVA alone did not generate a functional CD8+ T cell response and instead induced anergy. To determine if cross-presenting DCs are required for CD8+ T cell activation, we used mice deficient in the transcription factor Batf3, which selectively eliminates CD8α+ cross-presenting DCs. Following treatment with the Imprime-OVA conjugate in these Batf3-/- mice, the expansion of OVA-specific CD8+ T cells was more than 10-fold reduced compared to that in wild-type mice. Further, these cells failed to develop effector functions, indicating that CD8α+ cross-presenting DCs are crucial for this response. Together, these data show that an Imprime PGG-protein conjugate can effectively elicit the expansion and functional activation of cytotoxic T cells and may have utility as a potential cancer vaccine platform. Citation Format: Ross B. Fulton, Steven Leonardo, Kyle Michel, Lindsay Wurst, Trinda Phelon, Mike Danielson, Keith Gorden. Imprime PGG conjugated directly to protein enables cross-presentation of antigen that generates multifunctional cytotoxic T cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-236. doi:10.1158/1538-7445.AM2015-LB-236

P0128 Ubiquitinated proteins collected from tumour cells as a potent cancer vaccine

Introduction We have previously shown that the autophagosome-enriched vaccine DRibble (DRiPs-containing blebs), derived from tumour cells after inhibition of protein degradation, is an efficient antigen carrier for cross-priming of tumour-reactive CD8+ T cells. The anti-tumour efficacy induced by DRibbles is mainly dependent on its contents of ubiquitinated proteins. We sought to detect whether ubiquitinated proteins enriched from tumour cells could be used as a novel cancer vaccine. Methods We used two ubiquitin binding proteins (TUBES and Vx3[A7]) to isolate the ubiquitinated proteins from EL4 and B16-F10 tumour cells after blocking their proteasomal degradation pathway. C57BL/6 mice were vaccinated (intraperitoneal or subcutaneous injection) with different doses of ubiquitin-enriched proteins, DRibbles, ubiquitin-depleted proteins, and whole-cell lysate, separately. The lymphocytes from the vaccinated mice were restimulated with inactivated tumour cells and the levels of IFN- γ in the supernatant were measured by ELISA. Anti-tumour efficacy of vaccination with ubiquitin-enriched proteins was evaluated by monitoring tumour growth in established tumour mice models. Findings Vx3(A7) protein was more effective than TUBEs at purifying ubiquinated proteins from tumour whole-cell lysates. After stimulation with inactivated tumour cells, the lymphocytes from the mice vaccinated with ubiquitin-enriched proteins secreted high levels of IFN- γ in a dose-dependent manner in which intraperitoneal injection induced higher IFN- γ levels than subcutaneous injection. Furthermore, the level of secreted IFN- γ following vaccination with ubiquitin-enriched proteins was markedly higher than that after vaccination with whole-cell lysate and ubiquitin-depleted proteins. We also found that the ubiquitin-enriched proteins vaccine showed an inhibitory effect on tumour growth that regressed after vaccination with ubiquitin-enriched proteins, by contrast with other groups. Interpretation Ubiquitin-enriched proteins could be used in immunotherapy as a potent cancer vaccine.

Enhanced Control of Bladder-Associated Tumors Using Shrimp Anti-Lipopolysaccharide Factor (SALF) Antimicrobial Peptide as a Cancer Vaccine Adjuvant in Mice.

Shrimp anti-lipopolysaccharide factor (SALF) is an antimicrobial peptide with reported anticancer activities, such as suppression of tumor progression. In this study, we prepared a potential cancer vaccine comprised of SALF in conjunction with the cell lysate of inactivated murine bladder carcinoma cells (MBT-2), and evaluated its efficacy in a mouse tumor model. Our study shows that SALF added to cell culture media inhibits growth progression of MBT-2, and that SALF together with inactivated MBT-2 lysate elevates the level of inflammasome activity, and modulates the levels of IL-1β, MCP-1, IL-6, IL-12, and TNF-α in mouse macrophages. Immunization of 7, 14, and 21 day-old mice with the vaccine prevented growth of MBT-2 cell-mediated tumors. The vaccine was found to enhance expression of T-cell, cytotoxic T cells, and NK cells in the immunized mice groups. Recruitment of macrophages, T-helper cells, and NK cells was enhanced, but levels of VEGF were decreased in immunized mice. This report provides empirical evidence that our SALF as vaccine adjuvant enhances antitumor immunity in mice.

Precision cancer immunotherapy: optimizing dendritic cell-based strategies to induce tumor antigen-specific T-cell responses against individual patient tumors.

Most dendritic cell (DC)-based vaccines have loaded the DC with defined antigens, but loading with autologos tumor-derived antigens would generate DCs that activate personalized tumor-specific T-cell responses. We hypothesized that DC matured with an optimized combination of reagents and loaded with tumor-derived antigens using a clinically feasible electroporation strategy would induce potent antitumor immunity. We first studied the effects on DC maturation and antigen presentation of the addition of picibanil (OK432) to a combination of zoledronic acid, tumor necrosis factor-α, and prostaglandin E2. Using DC matured with the optimized combination, we tested 2 clinically feasible sources of autologous antigen for electroloading, total tumor mRNA or total tumor lysate, to determine which stimulated more potent antigen-specific T cells in vitro and activated more potent antitumor immunity in vivo. The combination of tumor necrosis factor-α/prostaglandin E2/zoledronic acid/OK432 generated DC with high expression of maturation markers and antigen-specific T-cell stimulatory function in vitro. Mature DC electroloaded with tumor-derived mRNA [mRNA electroporated dendritic cell (EPDC)] induced greater expansion of antigen-specific T cells in vitro than DC electroloaded with tumor lysate (lysate EPDC). In a therapeutic model of MC38-carcinoembryonic antigen colon cancer-bearing mice, vaccination with mRNA EPDC induced the most efficient anti-carcinoembryonic antigen cellular immune response, which significantly suppressed tumor growth. In conclusion, mature DC electroloaded with tumor-derived mRNA are a potent cancer vaccine, especially useful when specific tumor antigens for vaccination have not been identified, allowing autologous tumor, and if unavailable, allogeneic cell lines to be used as an unbiased source of antigen. Our data support clinical testing of this strategy.

Ubiquitinated proteins enriched from tumor cells by a ubiquitin binding protein Vx3(A7) as a potent cancer vaccine.

BackgroundOur previous studies have demonstrated that autophagosome-enriched vaccine (named DRibbles: DRiPs-containing blebs) induce a potent anti-tumor efficacy in different murine tumor models, in which DRibble-containing ubiquitinated proteins are efficient tumor-specific antigen source for the cross-presentation after being loaded onto dendritic cells. In this study, we sought to detect whether ubiquitinated proteins enriched from tumor cells could be used directly as a novel cancer vaccine.MethodsThe ubiquitin binding protein Vx3(A7) was used to isolate ubiquitinated proteins from EL4 and B16-F10 tumor cells after blocking their proteasomal degradation pathway. C57BL/6 mice were vaccinated with different doses of Ub-enriched proteins via inguinal lymph nodes or subcutaneous injection and with DRibbles, Ub-depleted proteins and whole cell lysate as comparison groups, respectively. The lymphocytes from the vaccinated mice were re-stimulated with inactivated tumor cells and the levels of IFN-γ in the supernatant were detected by ELISA. Anti-tumor efficacy of Ub-enriched proteins vaccine was evaluated by monitoring tumor growth in established tumor mice models. Graphpad Prism 5.0 was used for all statistical analysis.ResultsWe found that after stimulation with inactivated tumor cells, the lymphocytes from the Ub-enriched proteins-vaccinated mice secreted high level of IFN-γ in dose dependent manner, in which the priming vaccination via inguinal lymph nodes injection induced higher IFN-γ level than that via subcutaneous injection. Moreover, the level of secreted IFN-γ in the Ub-enriched proteins group was markedly higher than that in the whole cell lysate and Ub-depleted proteins. Interestingly, the lymphocytes from mice vaccinated with Ub-enriched proteins, but not Ub-depleted proteins and whole cell lysates, isolated from EL4 or B16-F10 tumor cells also produced an obvious level of IFN-γ when stimulated alternately with inactivated B16-F10 or EL4 tumor cells. Furthermore, Ub-enriched proteins vaccine showed a significant inhibitory effect on in vivo growth of homologous tumor, as well as allogeneic tumor, compared with Ub-depleted proteins and tumor cell lysate. Tumor growth was regressed after three times of vaccination with Ub-enriched proteins in contrast to other groups.ConclusionThese results indicated that Ub-enriched proteins isolated from tumor cells may have a potential as a potent vaccine for immunotherapy against cancer.

InCVAX – A novel strategy for treatment of late-stage, metastatic cancers through photoimmunotherapy induced tumor-specific immunity

A novel, promising potential cancer vaccine strategy was proposed to use a two-injection procedure for solid tumors to prompt the immune system to identify and systemically eliminate primary and metastatic cancers. The two-injection procedure consists of local photothermal application on a selected tumor intended to liberate whole cell tumor antigens, followed by a local injection of an immunoadjuvant that consists of a semi-synthetic functionalized glucosamine polymer, N-dihydro-galacto-chitosan (GC), which is intended to activate antigen presenting cells and facilitate an increased uptake of tumor antigens. This strategy is thus proposed as an in situ autologous cancer vaccine (inCVAX) that may activate antigen presenting cells and expose them to tumor antigens in situ, with the intention of inducing a systemic tumor specific T-cell response. Here, the development of inCVAX for the treatment of metastatic cancers in the past decades is systematically reviewed. The antitumor immune responses of local photothermal treatment and immunological stimulation with GC are also discussed. This treatment approach is also commonly referred to as laser immunotherapy (LIT).

Antibody-Carbohydrate Recognition from Docked Ensembles Using the AutoMap Procedure.

Carbohydrate-protein recognition is vital to many processes in health and disease. In particular, elucidation of the structural basis of carbohydrate binding is important to the development of oligosaccharides and oligosaccharide mimetics as vaccines for infectious diseases and cancer. Computational structural techniques are valuable for the study of carbohydrate-protein recognition due to the challenges associated with experimental determination of carbohydrate-protein complexes. AutoMap is a computer program that we have developed to study protein-ligand recognition. AutoMap determines the interactions taking place in a set of highly ranked poses obtained from molecular docking and processes these to identify the protein residues most likely to be involved in interactions. In this protocol, we describe the use of AutoMap and illustrate its suitability for studying antibody recognition of the Lewis Y tetrasaccharide, which is a potential cancer vaccine antigen.

Antitumor effect of therapeutic HPV DNA vaccines with chitosan-based nanodelivery systems.

BackgroundCervical cancer is the second-most-common cause of malignancies in women worldwide, and the oncogenic activity of the human papilloma virus types (HPV) E7 protein has a crucial role in anogenital tumors. In this study, we have designed a therapeutic vaccine based on chitosan nanodelivery systems to deliver HPV-16 E7 DNA vaccine, considered as a tumor specific antigen for immunotherapy of HPV-associated cervical cancer. We have developed a Nano-chitosan (NCS) as a carrier system for intramuscular administration using a recombinant DNA vaccine expressing HPV-16 E7 (NCS-DNA E7 vaccine). NCS were characterized in vitro for their gene transfection ability.ResultsThe transfection of CS-pEGFP NPs was efficient in CHO cells and the expression of green fluorescent proteins was well observed. In addition, NCS-DNA E7 vaccine induced the strongest E7-specific CD8+ T cell and interferon γ responses in C57BL/6 mice. Mice vaccinated with NCS-DNA E7 vaccine were able to generate potent protective and therapeutic antitumor effects against challenge with E7-expressing tumor cell line, TC-1.ConclusionsThe strong therapeutic effect induced by the Chitosan-based nanodelivery suggest that nanoparticles may be an efficient carrier to improve the immunogenicity of DNA vaccination upon intramuscular administration and the platform could be further exploited as a potential cancer vaccine candidate in humans.

MAGE-A3 With Cell-Penetrating Domain as an Efficient Therapeutic Cancer Vaccine

In conjunction with chemotherapy, immunotherapy with dendritic cells (DCs) may eliminate minimal disease burden by generating cytotoxic T lymphocytes. Enhanced cytosolic bioavailability of tumor-specific antigens improves access to human leukocyte antigen (HLA) class I molecules for more efficient cytotoxic T lymphocyte generation. Various cell-penetrating domains (CPDs) are known to ferry covalently linked heterologous antigens to the intracellular compartment by traversing the plasma membrane. To determine whether generating melanoma antigen family A, 3 (MAGE-A3), a tumor-specific cancer-testis antigen, as a fusion protein with CPD will enhance the cytosolic bioavailability of MAGE-A3. MAGE-A3 was amplified by polymerase chain reaction using complementary DNA from renal tissue and cloned in frame with a CPD (YARKARRQARR) at the amino-terminal end and hexahistidine at the carboxy-terminal end to generate CPD-MAGE-A3 in a pQE-70 expression vector. Cultures were grown in Escherichia coli BL21 Star (DE3-pLysS) cells followed by nickel-nitrilotriacetic acid affinity purification of recombinant proteins. Measurement of DC membrane penetration of CPD-MAGE-A3 vs MAGE-A3 and determination of the effect of CPD-MAGE-A3 pulsing on DC phenotypic expression of cell-surface antigens. Media composition and isopropyl-d-thiogalactosidase induction were optimized to achieve high levels of protein expression followed by purification. Western blot analysis with MAGE-A3 antibodies recognized both MAGE-A3 and CPD-MAGE-A3 proteins, while CPD antibodies recognized only CPD-MAGE-A3. Purified CPD-MAGE-A3 exhibited more efficient DC membrane penetration than did MAGE-A3 alone as confirmed by immunofluorescence analysis. High-level expression of several unique DC markers (CD80, CD83, CD86, and HLA-DR) by flow cytometry was consistent with a mature DC phenotype, indicating that pulsing with CPD-MAGE-A3 did not alter specific cell-surface antigens required for T-cell activation. We have demonstrated for the first time, to our knowledge, that cloning and purification of MAGE-A3 with CPD enhances its cytosolic bioavailability in DCs without altering cell-surface antigens, potentially making it a more potent therapeutic cancer vaccine compared with existing MAGE-A3 protein and peptide vaccines.

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Glycans in immune recognition and response

Glycans at the forefront of cells facilitate immune recognition processes. Cancer cells commonly present altered cell surface glycosylation, especially manifested in the expression of sialic acid at the termini of glycolipids and glycoproteins. Although tumor-associated carbohydrate antigens (TACAs) result in expression of altered-self, most such carbohydrates do not elicit strong humoral responses. Various strategies had been devised to elicit increased immunogenicity of such TACA aiming for potent immunotherapeutic antibodies or cancer vaccines. However some carbohydrates are immunogenic in humans and hold potential for novel glycotherapies. N-Glycolylneuraminic acid (Neu5Gc) is a foreign immunogenic sugar in humans originating from the diet (e.g., red meat) and subsequently expressed on the cell surface, especially accumulating on carcinoma. Consequently, the human immune system detects this non-self carbohydrate generating a broad anti-Neu5Gc antibody response. The co-existence of Neu5Gc/anti-Neu5Gc within humans spurs chronic inflammation mediated disease, including cancer. Concurrently, anti-Neu5Gc antibodies hold potential for novel targeted therapy. αGal is another foreign immunogenic carbohydrate antigen in humans and all humans have circulating anti-Gal antibodies. This review aims to describe the immunogenicity of Neu5Gc and its implications for human diseases, highlighting differences and similarities with αGal and its potential for novel targeted theranostics.

A Bacterial Flagellin in Combination With Proinflammatory Cytokines Activates Human Monocyte-derived Dendritic Cells to Generate Cytotoxic T Lymphocytes Having Increased Homing Signals to Cancer

Flagellin, the cognate ligand for toll-like receptor 5, has potent adjuvant activity in various vaccines. However, its efficacy in generating dendritic cells (DCs) remains contentious. This study assessed how efficaciously Vibrio vulnificus FlaB (v-FlaB) could be used in generating a potent DC to induce antigen-specific cytotoxic T lymphocytes (CTLs). Mature DCs (mDCs) induced by the combination of v-FlaB/TNFα/IFNα were significantly more potent in inducing specific anticancer immune responses compared with the standard DCs that were maturated by the conventional cytokine cocktail of TNFα/IL-1β/IL-6/PGE(2). The potent mDCs produced a higher level of interleukin (IL)-12p70 and polarized naive CD4(+) T cells more towards Th1-type cells, markedly increased antigen-specific CD8(+) T-cell number and significantly enhanced the induction of lytic enzymes in antigen-specific CD8(+) CTLs and sensitized CD3(+) T cells to produce higher number of interferon (IFN)γ-secreting cells. As a result, the mDCs produced more potent antigen-specific CTLs against the MART-1 and expressed higher levels of homing receptors CCR5 and CXCR3. More importantly, the v-FlaB/TNFα/IFNα-DCs generated from melanoma patients produced strong autologous CTLs with efficient cytotoxic activities. In conclusion, v-FlaB combined with tumor necrosis factor (TNF)α and IFNα can generate potent DCs which produce functionally active CTLs and that may have potential as a potent cancer vaccine.

Dendritic cell-based therapeutic cancer vaccines: past, present and future.

Dendritic cells (DCs) are professional antigen presenting cells, which play a pivotal role in antigen-specific (Ag-specific) T cell immunity. Malignancies have the capacity to inactivate DCs and effector T cells or to evade circulating antitumor immunity by expressing immune inhibitory molecules and/or secreting immunosuppressive cytokines. For this reason, ex-vivo-generated DCs [1] or in-vivo-DC-targeting [2] has been studied intensively over the past decade or development as a potential therapeutic cancer vaccine. Understanding how DCs induce, regulate, and maintain T cell immunity is essential for the design of novel cancer vaccines with improved clinical efficacy. Once activated, antigen-pulsed DCs are geared toward the launching of Ag-specific immunity, leading to T cell proliferation and differentiation into effector T cells. DCs are also important in triggering humoral immunity partly due to their capacity to directly interact with B cells and to present unprocessed antigens. There are examples of DC-based tumor vaccines being used successfully in clinical practice. Sipuleucel-T, the first Food and Drug Administration (FDA)-approved DC vaccine (Dendreon Corp.) has been found to be somewhat effective in the treatment of human prostate cancer [3]. As of 2014, 289 clinical studies of DC-based cancer vaccines are registered and under investigation (2014, http://www.clinicaltrials.gov). Among the 289 cases, 2 are in phase IV, 6 in phase III, 3 in phase II & III, 74 in phase II, 76 in phase I & II, 109 in phase I, and 3 in phase 0, underscoring the potential clinical significance of this therapy. In this editorial, we will discuss the evolution of DC-based cancer vaccine strategy, and future implications, with an emphasis on the efficacy and limitations of DC-based vaccine. Better understanding of DC biology and manipulation of activated DCs will allow DC scientists to produce the next generation of highly efficient cancer vaccines for cancer patients.

Oncolytic viruses as therapeutic cancer vaccines

Oncolytic viruses (OVs) are tumor-selective, multi-mechanistic antitumor agents. They kill infected cancer and associated endothelial cells via direct oncolysis, and uninfected cells via tumor vasculature targeting and bystander effect. Multimodal immunogenic cell death (ICD) together with autophagy often induced by OVs not only presents potent danger signals to dendritic cells but also efficiently cross-present tumor-associated antigens from cancer cells to dendritic cells to T cells to induce adaptive antitumor immunity. With this favorable immune backdrop, genetic engineering of OVs and rational combinations further potentiate OVs as cancer vaccines. OVs armed with GM-CSF (such as T-VEC and Pexa-Vec) or other immunostimulatory genes, induce potent anti-tumor immunity in both animal models and human patients. Combination with other immunotherapy regimens improve overall therapeutic efficacy. Coadministration with a HDAC inhibitor inhibits innate immunity transiently to promote infection and spread of OVs, and significantly enhances anti-tumor immunity and improves the therapeutic index. Local administration or OV mediated-expression of ligands for Toll-like receptors can rescue the function of tumor-infiltrating CD8+ T cells inhibited by the immunosuppressive tumor microenvironment and thus enhances the antitumor effect. Combination with cyclophosphamide further induces ICD, depletes Treg, and thus potentiates antitumor immunity. In summary, OVs properly armed or in rational combinations are potent therapeutic cancer vaccines.

'Multicopy multivalent' glycopolymer-stabilized gold nanoparticles as potential synthetic cancer vaccines.

Mucin-related carbohydrates are overexpressed on the surface of cancer cells, providing a disease-specific target for cancer immunotherapy. Here, we describe the design and construction of peptide-free multivalent glycosylated nanoscale constructs as potential synthetic cancer vaccines that generate significant titers of antibodies selective for aberrant mucin glycans. A polymerizable version of the Tn-antigen glycan was prepared and converted into well-defined glycopolymers by Reversible Addition–Fragmentation chain Transfer (RAFT) polymerization. The polymers were then conjugated to gold nanoparticles, yielding ‘multicopy-multivalent’ nanoscale glycoconjugates. Immunological studies indicated that these nanomaterials generated strong and long-lasting production of antibodies that are selective to the Tn-antigen glycan and cross-reactive toward mucin proteins displaying Tn. The results demonstrate proof-of-concept of a simple and modular approach toward synthetic anticancer vaccines based on multivalent glycosylated nanomaterials without the need for a typical vaccine protein component.

Dendritic cell derived exosomes need to activate both T and B cells to induce antitumor immunity (P4250)

Abstract Exosomes are secreted membrane nanovesicles of endosomal origin and are considered as potential cancer vaccine vectors. Phase I clinical trials have been successfully conducted with tumor peptide-loaded exosomes derived from dendritic cells (dexosomes) and a phase II clinical trial is currently ongoing. However, much is still unknown regarding the in vivo role of dexosomes and if the immunogenicity of dexosomes can be enhanced. We have previously reported that dexosomes induce CD4+ T cell responses in a B cell dependent manner, suggesting that immunizing with dexosomes only carrying T cell peptides induce suboptimal immune responses. Here we show that CD8+ T cell responses were induced in vivo when mice were immunized with protein, but not peptide, loaded dexosomes. We could also show that the cytotoxic T cell response was totally dependent on CD4+ T cells and, interestingly, also on B cells. Mice deficient in complement activation and antigen shuttling by B cells have lower responses to protein-loaded dexosomes showing involvement of these B cell mediated mechanisms. Finally, protein-loaded dexosomes were superior in protecting against tumor growth. In conclusion, proper activation of CD4+ T and B cells need to be considered when designing cancer vaccines to ensure full potential of the treatment.

The Ludwig Institute for Cancer Research Melbourne Melanoma Cell Line Panel

We established a range of melanoma cell lines from patient material (Table 1) termed Ludwig-Melbourne-Melanoma (LM-MEL-) followed by a unique number (method: Anaka et al., 2012). These lines have been human leucocyte antigen (HLA)-typed, their mutational status for common mutated genes in melanoma determined using the Sequenom MelCarta panel, and their transcriptomes profiled. All lines are tested for mycoplasma, and ethical approval for research purposes has been granted by the Austin Health Human Research Ethics Committee (HREC). Therapeutic options for advanced stage melanoma are limited, and despite the recent success with inhibitors of mutant v-raf murine sarcoma viral oncogene homolog B1 (BRAF) activity, long-lasting responses remain rare (Chapman et al., 2011). Immunotherapy may help overcome treatment failure, and there has been some success in the clinic with immunotherapy agents (Hodi et al., 2010). Knowledge of the antigen presenting major histocompatibility complex (MHC) class I HLA-types and antigenic proteins expressed by model systems is crucial for the preclinical testing of immunological interventions such as therapeutic cancer vaccines. Cancer-testis antigens (CTAg) and differentiation-antigens [mainly regulated by the microphtalmia-associated transcription factor (MITF)], represent two of the most studied families of potential cancer vaccine targets in melanoma (Caballero and Chen, 2009); and show various degrees of tissue-restriction and immunogenicity. The expression levels of some of these ‘immune-targetable’ genes premelanosome protein (PMEL), melan-A(MLANA), tyrosinase (TYR) and members of the melanoma antigen family (MAGE) in the LM-MEL cell lines are shown as an example in Figure 1. The complete gene-expression data and available additional clinical data of the here presented cell line panel are accessible online at ArrayExpress (http://www.ebi.ac.uk/arrayexpress/experiments/E-MTAB-1496/) and in Table S1. All cell lines are available upon request for a small handling fee or on a collaborative basis and slides for IHC from matched patient tumors and matched PBMCs/sera are accessible for some lines in limited quantities. AB is supported by a fellowship from the Cure Cancer Australia Foundation. JC and AB are supported by a grant from the Melanoma Research Alliance (MRA) and JC is supported by a practitioner fellowship from the Nation Health and Medical Research Council (NHMRC). This research was supported in part by the Cancer Council Victoria (CCV), the Austin Medical Research Foundation (AHMRF) and Operational Infrastructure Support Program Funding of the Victorian State Government. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Dendritic Cell–Derived Exosomes Need To Activate Both T and B Cells To Induce Antitumor Immunity

Exosomes are secreted membrane nanovesicles of endosomal origin and are considered potential cancer vaccine vectors. Phase I clinical trials have been successfully conducted with tumor peptide-loaded exosomes derived from dendritic cells (dexosomes), and a phase II clinical trial is ongoing. However, much is still unknown regarding the in vivo role of dexosomes and whether their immunogenicity can be enhanced. We previously reported that dexosomes induce CD4(+) T cell responses in a B cell-dependent manner, suggesting that immunization with dexosomes carrying only T cell peptides induce suboptimal immune responses. In this study, we show that CD8(+) T cell responses were induced in vivo when mice were immunized with protein-loaded, but not peptide-loaded, dexosomes. We also show that the cytotoxic T cell response was totally dependent on CD4(+) T cells and, interestingly, also on B cells. Mice deficient in complement activation and Ag shuttling by B cells have lower responses to protein-loaded dexosomes, showing involvement of these B cell-mediated mechanisms. Finally, protein-loaded dexosomes were superior in protecting against tumor growth. In conclusion, proper activation of CD4(+) T and B cells needs to be considered when designing cancer vaccines to ensure full potential of the treatment.

One-pot multi-enzyme (OPME) chemoenzymatic synthesis of sialyl-Tn-MUC1 and sialyl-T-MUC1 glycopeptides containing natural or non-natural sialic acid

A series of STn-MUC1 and ST-MUC1 glycopeptides containing naturally occurring and non-natural sialic acids have been chemoenzymatically synthesized from Tn-MUC1 glycopeptide using one-pot multienzyme (OPME) approaches. In situ generation of the sialyltransferase donor cytidine 5′-monophosphate-sialic acid (CMP-Sia) using a CMP-sialic acid synthetase in the presence of an extra amount of cytidine 5′-triphosphate (CTP) and removal of CMP from the reaction mixture by flash C18 cartridge purification allow the complete consumption of Tn-MUC1 glycopeptide for quantitative synthesis of STn-MUC1. A Campylobacter jejuni β1–3GalT (CjCgtBΔ30-His6) mutant has been found to catalyze the transfer of one or more galactose residues to Tn-MUC1 for the synthesis of T-MUC1 and galactosylated T-MUC1. Sialylation of T-MUC1 using Pasteurella multocida α2–3-sialyltransferase 3 (PmST3) with Neisseria meningitidis CMP-sialic acid synthetase (NmCSS) and Escherichia coli sialic acid aldolase in one pot produced ST-MUC1 efficiently. These glycopeptides are potential cancer vaccine candidates.