A CpG-loaded tumor cell vaccine induces antitumor CD4+ T cells that are effective in adoptive therapy for large and established tumors

In Ovo Vaccination with Recombinant Herpes Virus of the Turkey-Laryngotracheitis Vaccine Adjuvanted with CpG-Oligonucleotide Provides Protection against a Viral Challenge in Broiler Chickens

Infectious laryngotracheitis (ILT) is an economically important disease in chickens. We previously showed that an in ovo adjuvantation of recombinant herpesvirus of the turkey-Laryngotracheitis (rHVT-LT) vaccine with CpG-oligonucleotides (ODN) can boost vaccine-induced responses in one-day-old broiler chickens. Here, we evaluated the protective efficacy of in ovo administered rHVT-LT + CpG-ODN vaccination against a wild-type ILT virus (ILTV) challenge at 28 days of age and assessed splenic immune gene expression as well as cellular responses. A chicken-embryo-origin (CEO)-ILT vaccine administered in water at 14 days of age was also used as a comparative control for the protection assessment. The results showed that the rHVT-LT + CpG-ODN or the CEO vaccinations provided significant protection against the ILTV challenge and that the level of protection induced by both the vaccines was statistically similar. The protected birds had a significantly upregulated expression of interferon (IFN)γ or interleukin (IL)-12 cytokine genes. Furthermore, the chickens vaccinated with the rHVT-LT + CpG-ODN or CEO vaccine had a significantly higher frequency of γδ T cells and activated CD4+ or CD8+ T cells, compared to the unvaccinated-ILTV challenge control. Collectively, our findings suggest that CpG-ODN can be used as an effective adjuvant for rHVT-LT in ovo vaccination to induce protective immunity against ILT in broiler chickens.

Construction of pH-Sensitive Nanovaccines Encapsulating Tumor Cell Lysates and Immune Adjuvants for Breast Cancer Therapy

The current immunotherapy strategies for triple negative breast cancer (TNBC) are greatly limited due to the immunosuppressive tumor microenvironment (TME). Immunization with cancer vaccines composed of tumor cell lysates (TCL) can induce an effective antitumor immune response. However, this approach also has the disadvantages of inefficient antigen delivery to the tumor tissues and the limited immune response elicited by single-antigen vaccines. To overcome these limitations, a pH-sensitive nanocalcium carbonate (CaCO3 ) carrier loaded with TCL and immune adjuvant CpG (CpG oligodeoxynucleotide 1826) is herein constructed for TNBC immunotherapy. This tailor-made nanovaccine, termed CaCO3 @TCL/CpG, not only neutralizes the acidic TME through the consumption of lactate by CaCO3 , which increases the proportion of the M1/M2 macrophages and promotes infiltration of effector immune cells but also activates the dendritic cells in the tumor tissues and recruits cytotoxic T cells to further kill the tumor cells. In vivo fluorescence imaging study shows that the pegylated nanovaccine could stay longer in the blood circulation and extravasate preferentially into tumor site. Besides, the nanovaccine exhibits high cytotoxicity in 4T1 cells and significantly inhibits tumor growth of tumor-bearing mice. Overall, this pH-sensitive nanovaccine is a promising nanoplatform for enhanced immunotherapy of TNBC.

Harnessing Unconventional T Cells and Innate Lymphoid Cells to Prevent and Treat Hematological Malignancies: Prospects for New Immunotherapy

Unconventional T cells and innate lymphoid cells (ILCs) make up a heterogeneous set of cells that characteristically show prompt responses toward specific antigens. Unconventional T cells recognize non-peptide antigens, which are bound and presented by diverse non-polymorphic antigen-presenting molecules and comprise γδ T cells, MR1-restricted mucosal-associated invariant T cells (MAITs), and natural killer T cells (NKTs). On the other hand, ILCs lack antigen-specific receptors and act as the innate counterpart to the T lymphocytes found in the adaptive immune response. The alteration of unconventional T cells and ILCs in frequency and functionality is correlated with the onset of several autoimmune diseases, allergy, inflammation, and tumor. However, depending on the physio-pathological framework, unconventional T cells may exhibit either protective or pathogenic activity in a range of neoplastic diseases. Nonetheless, experimental models and clinical studies have displayed that some unconventional T cells are potential therapeutic targets, as well as prognostic and diagnostic markers. In fact, cell-mediated immune response in tumors has become the focus in immunotherapy against neoplastic disease. This review concentrates on the present knowledge concerning the function of unconventional T cell sets in the antitumor immune response in hematological malignancies, such as acute and chronic leukemia, multiple myeloma, and lymphoproliferative disorders. Moreover, we discuss the possibility that modulating the activity of unconventional T cells could be useful in the treatment of hematological neoplasms, in the prevention of specific conditions (such as graft versus host disease), and in the formulation of an effective anticancer vaccine therapy. The exact knowledge of the role of these cells could represent the prerequisite for the creation of a new form of immunotherapy for hematological neoplasms.

Near infrared light activation of an injectable whole-cell cancer vaccine for cancer immunoprophylaxis and immunotherapy

Cancer vaccines play a key role in the prevention and treatment of early and recurrent tumors. Although they have been widely studied during the past few decades, designing an efficient and economical cancer vaccine is still challenging. Here, we propose an injectable live cell cancer vaccine (InLCCV) using live tumor cells as immunogenic sources for cancer immunoprophylaxis and immunotherapy. InLCCV is fabricated by loading live mouse breast cancer cells (4T1 cells), gold nanorods (GNRs), and super-low-dose lipopolysaccharide (LPS) into a biocompatible Pluronic F127 in situ hydrogel matrix. After in situ inactivation by the photothermal effect of GNRs upon near-infrared (NIR) laser irradiation, immunogenic cell death (ICD) of 4T1 cells is induced and tumor-associated antigens (TAAs) together with loaded LPS are released subsequently. Therefore, dendritic cells and macrophages are activated accordingly, further stimulating the systemic anti-tumor immune response. After vaccinating with InLCCV, the tumor-free percentage of the mice is 60% and the survival rate during the observation period reaches up to 80%. For lung metastasis, the metastatic foci are 3.9-fold less than those of the control group. The as-developed InLCCV shows much promise as a potential platform for breast cancer immunoprophylaxis and immunotherapy.

Autologous tumor cell vaccine induces antitumor T cell immune responses in patients with mantle cell lymphoma: A phase I/II trial

Here, we report on the results of a phase I/II trial (NCT00490529) for patients with mantle cell lymphoma who, having achieved remission after immunochemotherapy, were vaccinated with irradiated, CpG-activated tumor cells. Subsequently, vaccine-primed lymphocytes were collected and reinfused after a standard autologous stem cell transplantation (ASCT). The primary endpoint was detection of minimal residual disease (MRD) within 1 yr after ASCT at the previously validated threshold of ≥1 malignant cell per 10,000 leukocyte equivalents. Of 45 evaluable patients, 40 (89%) were found to be MRD negative, and the MRD-positive patients experienced early subsequent relapse. The vaccination induced antitumor CD8 T cell immune responses in 40% of patients, and these were associated with favorable clinical outcomes. Patients with high tumor PD-L1 expression after in vitro exposure to CpG had inferior outcomes. Vaccination with CpG-stimulated autologous tumor cells followed by the adoptive transfer of vaccine-primed lymphocytes after ASCT is feasible and safe.

Therapeutic vaccines for aggressive B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive B-cell lymphoma and highly heterogeneous disease. With the standard immunochemotherapy, anti-CD20 antibody rituximab (R-) plus CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy, 30-40% of DLBCLs are refractory to initial immunochemotherapy or experience relapse post-therapy with poor clinical outcomes despite salvage therapies. Mechanisms underlying chemoresistance and relapse are heterogeneous across DLBCL and within individual patients, representing hurdles for targeted therapies targeting a specific oncogenic signaling pathway. In recent years, paradigm-shifting immunotherapies have shown impressive efficacy in various cancer types regardless of underlying oncogenic mechanisms. Vaccines are being developed for DLBCL to build protective immunity against relapse after first complete remission and to promote antitumor immune responses synergizing with immune checkpoint inhibitors to treat refractory/relapsed patients. This article provides a brief review of current progress in vaccine development in DLBCL and discussion on immunologic mechanisms underlying the therapeutic effectiveness and resistance.

Programmable multistage drug delivery to lymph nodes

Therapeutic delivery selectively to lymph nodes has the potential to address a variety of unmet clinical needs. However, owing to the unique structure of the lymphatics and the size-restrictive nature of the lymph node reticular network, delivering cargo to specific cells in the lymph node cortex and paracortex is difficult. Here, we describe a delivery system to overcome lymphatic and intra-lymph node transport barriers by combining nanoparticles that are rapidly conveyed to draining lymph nodes after administration in peripheral tissues with programmable degradable linkers. This platform enables the controlled release of intra-lymph-mobile small-molecular cargo, which can reach vastly more immune cells throughout the lymph node than either the particles or free compounds alone. The release rate can be programmed, allowing access to different lymph node structures and therefore specific lymphocyte subpopulations. We are thus able to alter the subtypes of drugged lymph node cells to improve immunotherapeutic effects.

Autologous iPSC-Based Vaccines Elicit Anti-tumor Responses In Vivo

Cancer cells and embryonic tissues share a number of cellular and molecular properties, suggesting that induced pluripotent stem cells (iPSCs) may be harnessed to elicit anti-tumor responses in cancer vaccines. RNA sequencing revealed that human and murine iPSCs express tumor-associated antigens, and we show here a proof of principle for using irradiated iPSCs in autologous anti-tumor vaccines. In a prophylactic setting, iPSC vaccines prevent tumor growth in syngeneic murine breast cancer, mesothelioma, and melanoma models. As an adjuvant, the iPSC vaccine inhibited melanoma recurrence at the resection site and reduced metastatic tumor load, which was associated with fewer Th17 cells and increased CD11b+GR1hi myeloid cells. Adoptive transfer of T cells isolated from vaccine-treated tumor-bearing mice inhibited tumor growth in unvaccinated recipients, indicating that the iPSC vaccine promotes an antigen-specific anti-tumor T cell response. Our data suggest an easy, generalizable strategy for multiple types of cancer that could prove highly valuable in clinical immunotherapy.

Immunotherapy with subcutaneous immunogenic autologous tumor lysate increases murine glioblastoma survival

Immunotherapeutic strategies for glioblastoma, the most frequent malignant primary brain tumor, aim to improve its disastrous consequences. On top of the standard treatment, one strategy uses T cell activation by autologous dendritic cells (DC) ex vivo loaded with tumor lysate to attack remaining cancer cells. Wondering whether 'targeting' in vivo DCs could replace these ex vivo ones, immunogenic autologous tumor lysate was used to treat glioma-inoculated mice in the absence of ex vivo loaded DCs. Potential immune mechanisms were studied in two orthotopic, immunocompetent murine glioma models. Pre-tumoral subcutaneous lysate treatment resulted in a survival benefit comparable to subcutaneous DC therapy. Focussing on the immune response, glioma T cell infiltration was observed in parallel with decreased amounts of regulatory T cells. Moreover, these results were accompanied by the presence of strong tumor-specific immunological memory, shown by complete survival of a second glioblastoma tumor, inoculated 100 days after the first one. Finally, in combination with temozolomide, survival of established glioma in mice could be increased. Our results show the potential of immunogenic autologous tumor lysate used to treat murine glioblastoma, which will be worthwhile to study in clinical trials as it has potential as a cost-efficient adjuvant treatment strategy for gliomas.

Targeting CpG Adjuvant to Lymph Node via Dextran Conjugate Enhances Antitumor Immunotherapy

Nucleic acid based adjuvants recognized by Toll-like receptors (TLR) are potent immune system stimulants that can augment the antitumor immune responses in an antigen-specific manner. However, their clinical uses as vaccine adjuvants are limited primarily due to lack of accumulation in the lymph nodes, the anatomic sites where the immune responses are initiated. Here, we showed that chemical conjugation of type B CpG DNA, a TLR9 agonist to dextran polymer dramatically enhanced CpG's lymph node accumulation in mice. Dextran conjugation did not alter CpG ODN's uptake, internalization, and bioactivity in vitro. Delivery of Dextran-CpG conjugate markedly increased the uptake by antigen presenting cells in the lymph nodes and enhanced CD8⁺ T cell responses primed by protein vaccines, leading to improved therapeutic antitumor immunity. Furthermore, immunization with Dextran-CpG mixed with necrotic whole tumor cells induced a protective antitumor response in a murine model, suggesting that this approach was not limited to molecularly defined antigens. This simple method might also be applicable for the delivery of many other nucleic acid based adjuvants in cancer vaccines.

Vaccine strategies for the treatment of lymphoma: preclinical progress and clinical trial update

The clonal B-cell immunoglobulin idiotype found on the surface of lymphomas was the first targeted tumor-specific antigen, and combinations of idiotype with classical and novel adjuvants were shown to stimulate robust humoral and cellular responses, though clinical efficacy was more variable. Cellular and in situ vaccination to help target a wider array of tumor-specific antigens have also been able to stimulate tumor-specific cellular responses, though their clinical success has also been limited. Our growing understanding of the role of regulatory cells and the immunosuppressive tumor microenvironment, along with a wide variety of immunomodulatory agents developed as of late, offer promising adjuvants to potentiate the immune responses elicited by these vaccine protocols and to achieve durable remissions.

Tumor-directed immunotherapy can generate tumor-specific T cell responses through localized co-stimulation

The most important goals for the field of immuno-oncology are to improve the response rate and increase the number of tumor indications that respond to immunotherapy, without increasing adverse side effects. One approach to achieve these goals is to use tumor-directed immunotherapy, i.e., to focus the immune activation to the most relevant part of the immune system. This may improve anti-tumor efficacy as well as reduce immune-related adverse events. Tumor-directed immune activation can be achieved by local injections of immune modulators in the tumor area or by directing the immune modulator to the tumor using bispecific antibodies. In this review, we focus on therapies targeting checkpoint inhibitors and co-stimulatory receptors that can generate tumor-specific T cell responses through localized immune activation.

Long-term outcomes of helper peptide vaccination for metastatic melanoma

OBJECTIVE

The objective of this study was to compare the long-term outcome of patients with metastatic melanoma vaccinated with 6MHP to that of a group of unvaccinated historical controls.

BACKGROUND

A multipeptide vaccine (6MHP), designed to induce helper T cells against melanocytic and cancer-testis antigens, has been shown to induce specific Th1-dominant CD4+ T cell responses.

METHODS

The 6MHP vaccine was administered to patients with metastatic melanoma. Circulating CD4+ T cell responses were measured by proliferation or direct IFN-gamma ELIspot assay. Overall survival of vaccinated patients was compared to a group of clinically comparable historical controls using multivariable Cox regression analysis and Kaplan-Meier survival analysis, taking into account age, metastatic site, and resection status.

RESULTS

Across 40 vaccinated patients and 87 controls, resection status (HR 0.54, P = 0.004) and vaccination (HR 0.24, P < 0.001) were associated with improved overall survival. Forty pairs of vaccinated patients and controls were matched by metastatic site, resection status, and age within 10 years. Median survival was significantly longer for vaccinated patients (5.4 vs 1.3 years, P < 0.001). Among the vaccinated patients, the development of a specific immune response after vaccination was associated with improved survival (HR 0.35, P = 0.040).

CONCLUSIONS

Helper peptide vaccination is associated with improved overall survival among patients with metastatic melanoma. These data support a randomized prospective trial of the 6MHP vaccine.

Interleukin-28B Plays a Therapeutic Role on Mouse U14 Cervical Cancer Cells by Down-Regulating CD4+CD25+FoxP3+Regulatory T Cells In Vivo

AIM

To investigate the immunotherapeutic effectiveness of adenoviral vector expressing mouse interleukin (IL)-28B (Ad-mIL-28B) against cervical cancer and its mechanism.

METHOD

U14 cervical cancer cell-bearing mice were treated with Ad-mIL-28B. Meanwhile, whole cell vaccine was prepared by repeated freezing and thawing U14 cells. Then CD4⁺CD25⁺FoxP3⁺regulatory T (Treg) cells were evaluated by flow cytometry. Tumor volume and metastasis in BALB/c and C57BL/6j mice were detected.

RESULTS

Ad-mIL-28B treatment significantly decreased the number of CD4⁺CD25⁺FoxP3⁺Treg cells. Subsequently, there was a significant decrease in the size of tumor tissue and the numbers of heteromorphic tumor cells. The tumor metastasis in the lung and liver of the Ad-mIL-28B group also decreased. However, there was no therapeutic effect observed for whole cell vaccine on U14 tumor-bearing mice.

CONCLUSION

Interleukin-28B can inhibit the growth and metastasis of cervical cancer in U14 tumor-bearing mice by down-regulating Treg cells.

Lymphoma Immunotherapy: Current Status

The rationale to treat lymphomas with immunotherapy comes from long-standing evidence on their distinctive immune responsiveness. Indolent B-cell non-Hodgkin lymphomas, in particular, establish key interactions with the immune microenvironment to ensure prosurvival signals and prevent antitumor immune activation. However, reports of spontaneous regressions indicate that, under certain circumstances, patients develop therapeutic antitumor immunity. Several immunotherapeutic approaches have been thus developed to boost these effects in all patients. To date, targeting CD20 on malignant B cells with the antibody rituximab has been the most clinically effective strategy. However, relapse and resistance prevent to cure approximately half of B-NHL patients, underscoring the need of more effective therapies. The recognition of B-cell receptor variable regions as B-NHL unique antigens promoted the development of specific vaccines to immunize patients against their own tumor. Despite initial promising results, this strategy has not yet demonstrated a sufficient clinical benefit to reach the regulatory approval. Several novel agents are now available to stimulate immune effector functions or counteract immunosuppressive mechanisms, such as engineered antitumor T cells, co-stimulatory receptor agonist, and immune checkpoint-blocking antibodies. Thus, multiple elements can now be exploited in more effective combinations to break the barriers for the induction of anti-lymphoma immunity.

Vaccination strategies in lymphoproliferative disorders: Failures and successes

Anti-tumor vaccines in lymphoproliferative disorders hold out the prospect of effective tumor therapies with minimal side effects. The addition of immunotherapy to old and new chemotherapy regimens has improved both response rates and disease-free survival, leading in many cases to an extended overall survival. Ideally, an antigen that is used for vaccination would be specifically expressed in the tumor; it must have an important, causal part in the multifactorial process that leads to cancer, and it must be expressed stably even after it is attacked by the immune system. Immunotherapies, which aim to activate the immune system to kill cancer cells, include strategies to increase the frequency or potency of antitumor T cells, to overcome suppressive factors in the tumor microenvironment, and to reduce T-cell suppression systemically. In this review, we focus on the results of clinical trials of vaccination in lymphoma, and discuss potential strategies to enhance the efficacy of immunotherapy in the future.

Vaccines, Adjuvants, and Dendritic Cell Activators--Current Status and Future Challenges

Cancer vaccines offer a low-toxicity approach to induce anticancer immune responses. They have shown promise for clinical benefit with one cancer vaccine approved in the United States for advanced prostate cancer. As other immune therapies are now clearly effective for treatment of advanced cancers of many histologies, there is renewed enthusiasm for optimizing cancer vaccines for use to prevent recurrence in early-stage cancers and/or to combine with other immune therapies for therapy of advanced cancers. Future advancements in vaccine therapy will involve the identification and selection of effective antigen formulations, optimization of adjuvants, dendritic cell (DC) activation, and combination therapies. In this summary we present the current practice, the broad collection of challenges, and the promising future directions of vaccine therapy for cancer.

Ibrutinib enhances the antitumor immune response induced by intratumoral injection of a TLR9 ligand in mouse lymphoma

We have designed a novel therapeutic approach for lymphoma that combines targeted kinase inhibition with in situ vaccination. Intratumoral injection of an unmethylated cytosine guanine dinucleotide (CpG)-enriched oligodeoxynucleotide, an agonist for the toll-like receptor 9 (TLR9), induces the activation of natural killer cells, macrophages, and antigen presenting cells that control tumor growth at the local site. Ibrutinib, an irreversible inhibitor of Bruton's tyrosine kinase, a key enzyme in the signaling pathway downstream of B-cell receptor, is an effective treatment against many types of B-cell lymphomas. The combination of intratumoral injection of CpG with systemic treatment by ibrutinib resulted in eradication of the tumors not only in the injected site, but also at distant sites. Surprisingly, this combinatorial antitumor effect required an intact T-cell immune system since it did not occur in nude, severe combined immunodeficiency, or T-cell depleted mice. Moreover, T cells from animals treated with intratumoral CpG and ibrutinib prevented the outgrowth of newly injected tumors. This result suggests that ibrutinib can induce immunogenic cell death of lymphoma cells and that concomitant stimulation of antigen-presenting cells in the tumor microenvironment by toll-like receptor ligands can lead to a powerful systemic antitumor immune response.

Tumor ablation by intratumoral Ra-224-loaded wires induces anti-tumor immunity against experimental metastatic tumors

INTRODUCTION

The current systemic anti-metastatic treatment is chemotherapy. Chemotherapy reacts mostly against replicating cells, which makes this therapy not specific. Moreover, resting cancer cells will not be destroyed. A better alternative is an engagement of the host immune system to react against tumor-associated antigens. An efficient immune-stimulating technique is an ablation of the tumor that results in the release of tumor antigens. Our ablation strategy is an innovative alpha-radiation-based technology, diffusing alpha-emitters radiation therapy (DaRT), which efficiently destroys local tumors and provides thereby an antigenic supply for antigen-presenting cells to stimulate T cells.

METHODS

Mice bearing weakly immunogenic DA3 adenocarcinoma or highly immunogenic CT26 colon carcinoma were treated by DaRT. Anti-tumor immune responses following tumor destruction were evaluated by (1) the resistance to a tumor challenge; (2) scanning by a CT imaging device for elimination of lung metastases; (3) improved tumor control when combining DaRT with an immunoadjuvant (CpG).

RESULTS

CT26 model: 63-77 % of DaRT-treated mice became resistant to a re-inoculated tumor compared to 29-33 % resistant mice in the control. DA3 model: (1) The growth rate of challenge tumors was the lowest in mice which their primary tumor was treated by DaRT. (2) Most (93 %) mice in the control group developed lung metastases compared to 56 % in the DaRT group. (3) Combining DaRT with CpG resulted in a better control of the primary tumor. Our study offers a technique to eliminate local and distant malignant cells, regardless of their replication status, by stimulating specific anti-tumor immunity through the supply of tumor antigens from the destroyed tumor.

Artificial Antigen Presenting Cells: An Off the Shelf Approach for Generation of Desirable T-Cell Populations for Broad Application of Adoptive Immunotherapy

Adoptive transfer of antigen specific T-cells can lead to eradication of cancer and viral infections. The broad application of this approach has further been hampered by the limited availability of adequate numbers of T-cells for treatment in a timely manner. This has led to efforts for the development of efficient methods to generate large numbers of T-cells with specificity for tumor or viral antigens that can be harnessed for use in cancer therapy. Recent studies have demonstrated that during encounter with tumor antigen, the signals delivered to T-cells by professional antigen-presenting cells can affect T-cell programming and their subsequent therapeutic efficacy. This has stimulated efforts to develop artificial antigen-presenting cells that allow optimal control over the signals provided to T-cells. In this review, we will discuss the cellular artificial antigen-presenting cell systems and their use in T-cell adoptive immunotherapy for cancer and infections.

An autologous leukemia cell vaccine prevents murine acute leukemia relapse after cytarabine treatment

Acute leukemias with adverse prognostic features carry a high relapse rate without allogeneic stem cell transplantation (allo-SCT). Allo-SCT has a high morbidity and is precluded for many patients because of advanced age or comorbidities. Postremission therapies with reduced toxicities are urgently needed. The murine acute leukemia model C1498 was used to study the efficacy of an intravenously administered vaccine consisting of irradiated leukemia cells loaded with the natural killer T (NKT)-cell agonist α-galactosylceramide (α-GalCer). Prophylactically, the vaccine was highly effective at preventing leukemia development through the downstream activities of activated NKT cells, which were dependent on splenic langerin(+)CD8α(+) dendritic cells and which led to stimulation of antileukemia CD4(+) and CD8(+) T cells. However, hosts with established leukemia received no protective benefit from the vaccine, despite inducing NKT-cell activation. Established leukemia was associated with increases in regulatory T cells and myeloid-derived suppressor cells, and the leukemic cells themselves were highly suppressive in vitro. Although this suppressive environment impaired both effector arms of the immune response, CD4(+) T-cell responses were more severely affected. When cytarabine chemotherapy was administered prior to vaccination, all animals in remission posttherapy were protected against rechallenge with viable leukemia cells.

TLR9 is critical for glioma stem cell maintenance and targeting

Understanding supports for cancer stem-like cells in malignant glioma may suggest therapeutic strategies for their elimination. Here, we show that the Toll-like receptor TLR9 is elevated in glioma stem-like cells (GSC) in which it contributes to glioma growth. TLR9 overexpression is regulated by STAT3, which is required for GSC maintenance. Stimulation of TLR9 with a CpG ligand (CpG ODN) promoted GSC growth, whereas silencing TLR9 expression abrogated GSC development. CpG-ODN treatment induced Frizzled4-dependent activation of JAK2, thereby activating STAT3. Targeted delivery of siRNA into GSC was achieved via TLR9 using CpG-siRNA conjugates. Through local or systemic treatment, administration of CpG-Stat3 siRNA to silence STAT3 in vivo reduced GSC along with glioma growth. Our findings identify TLR9 as a functional marker for GSC and a target for the delivery of efficacious therapeutics for glioma treatment. Cancer Res; 74(18); 5218-28. ©2014 AACR.

Covalent modification of cell surfaces with TLR agonists improves & directs immune stimulation

We present a primary example of a cell surface modified with a synergistic combination of agonists to tune immune stimulation. A model cell line, Lewis Lung Carcinoma, was covalently modified with CpG-oligonucleotides and lipoteichoic acid, both Toll-like receptor (TLR) agonists. The immune-stimulating constructs provided greater stimulation of NF-κB in a model cell line and bone marrow-derived dendritic cells than the components unconjugated in solution.

Brain tumor immunotherapy: seeing the brain in the body

Brain tumor immunotherapy is often interpreted in terms of immune privilege and the blood-brain barrier (BBB), but a broader view is warranted. The delicate regulatory balance of the immune system is relevant at any site, as are the heterogeneity and plasticity of tumor growth. Criteria for tumor antigens, and often the antigens themselves, cut across tumor types. Here, this broader view, complemented by current understanding of privilege and the BBB, provides the context for review. Future success is likely to exploit simplified methods, used in combination; and similarities - more than differences - between the brain and other sites.

NKT cell adjuvant-based tumor vaccine for treatment of myc oncogene-driven mouse B-cell lymphoma

Immunomodulators are effective in controlling hematologic malignancy by initiating or reactivating host antitumor immunity to otherwise poorly immunogenic and immune suppressive cancers. We aimed to boost antitumor immunity in B-cell lymphoma by developing a tumor cell vaccine incorporating α-galactosylceramide (α-GalCer) that targets the immune adjuvant properties of NKT cells. In the Eμ-myc transgenic mouse model, single therapeutic vaccination of irradiated, α-GalCer-loaded autologous tumor cells was sufficient to significantly inhibit growth of established tumors and prolong survival. Vaccine-induced antilymphoma immunity required NKT cells, NK cells, and CD8 T cells, and early IL-12-dependent production of IFN-γ. CD4 T cells, gamma/delta T cells, and IL-18 were not critical. Vaccine treatment induced a large systemic spike of IFN-γ and transient peripheral expansion of both NKT cells and NK cells, the major sources of IFN-γ. Furthermore, this vaccine approach was assessed in several other hematopoietic tumor models and was also therapeutically effective against AML-ETO9a acute myeloid leukemia. Replacing α-GalCer with β-mannosylceramide resulted in prolonged protection against Eμ-myc lymphoma. Overall, our results demonstrate a potent immune adjuvant effect of NKT cell ligands in therapeutic anticancer vaccination against oncogene-driven lymphomas, and this work supports clinical investigation of NKT cell-based immunotherapy in patients with hematologic malignancies.

CpG plus radiotherapy: a review of preclinical works leading to clinical trial

Studies performed three decades ago in our laboratory supported the hypothesis that radiation efficacy may be augmented by bacterial extracts that stimulate non-specific systemic antitumor immune responses. Application to the clinic was halted by unacceptable side effects and toxicities resulting from exposure to whole bacterial pathogens. Later scientific advances demonstrated that DNA isolated from bacteria was immunostimulatory and could be reproduced with synthetic oligodeoxynucleotides (ODNs), thus fueling the transition from bugs to drugs. Unmethylated CpG motifs within bacterial DNA induce activation of Toll-like receptor 9 and subsequently activate antigen-specific cellular immune responses. CpG ODNs have demonstrated favorable toxicity profiles in phase I clinical trials. We showed that this potent immunoadjuvant can be used in combination with radiation therapy to enhance local and systemic responses of several murine tumors. Studies demonstrated that enhanced tumor response is mediated in part by the host immune system. Antitumor efficacy was diminished in immunocompromised mice. Animals cured by combination of radiation and CpG ODN were resistant to subsequent tumor rechallenge. This body of work contributes to our understanding of the dynamic interplay between tumor irradiation and the host immune system and may facilitate translation to clinical trials.

Cytotoxic chemotherapy and CD4+ effector T cells: an emerging alliance for durable antitumor effects

Standard cytotoxic chemotherapy can initially achieve high response rates, but relapses often occur in patients and represent a severe clinical problem. As increasing numbers of chemotherapeutic agents are found to have immunostimulatory effects, there is a growing interest to combine chemotherapy and immunotherapy for synergistic antitumor effects and improved clinical benefits. Findings from recent studies suggest that highly activated, polyfunctional CD4+ effector T cells have tremendous potential in strengthening and sustaining the overall host antitumor immunity in the postchemotherapy window. This review focuses on the latest progresses regarding the impact of chemotherapy on CD4+ T-cell phenotype and function and discusses the prospect of exploiting CD4+ T cells to control tumor progression and prevent relapse after chemotherapy.

Conjugation of lymphoma idiotype to CD40 antibody enhances lymphoma vaccine immunogenicity and antitumor effects in mice

Personalized immunotherapy of lymphoma based on tumor idiotype (Id) has shown anti-idiotype humoral immune responses in 40%-50% and cellular immune responses in 50%-75% of follicular lymphoma patients, indicating that this therapy can be clinically successful. We have developed a novel vaccine against lymphoma consisting of an anti-CD40 Ab (ADX40) chemically conjugated to the tumor idiotype A20 and tested it in a murine lymphoma model. BALB/c mice were immunized with 2 doses of immunogen alone or in conjunction with additional adjuvants before tumor challenge. ADX40-Id vaccination resulted in significantly retarded tumor growth and reduced mouse morbidity. Moreover, similar mouse survival was obtained with 2 injections of ADX40-Id as with 8 injections using the standard therapy of keyhole limpet hemocyanin Id + GM-CSF. Co-administration of ADX40-Id with 3-O-deacyl-4'-monophosphoryl lipid A further significantly enhanced vaccine efficacy, resulting in an increased overall survival. Anti-Id-specific Abs were detected at elevated levels after ADX40-Id immunization; however, in vivo depletion of CD4 and/or CD8 T cells before challenge showed that CD8 effector T cells were the major mediators of tumor protection. The results of the present study show that the ADX40-Id conjugate vaccine is a potential candidate as a stand-alone vaccine or in combination with currently licensed adjuvants for lymphoma immunotherapy.

Adoptive cell therapy for lymphoma with CD4 T cells depleted of CD137-expressing regulatory T cells

Adoptive immunotherapy with antitumor T cells is a promising novel approach for the treatment of cancer. However, T-cell therapy may be limited by the cotransfer of regulatory T cells (T(reg)). Here, we explored this hypothesis by using 2 cell surface markers, CD44 and CD137, to isolate antitumor CD4 T cells while excluding T(regs). In a murine model of B-cell lymphoma, only CD137(neg)CD44(hi) CD4 T cells infiltrated tumor sites and provided protection. Conversely, the population of CD137(pos)CD44hi CD4 T cells consisted primarily of activated T(regs). Notably, this CD137(pos) T(reg) population persisted following adoptive transfer and maintained expression of FoxP3 as well as CD137. Moreover, in vitro these CD137(pos) cells suppressed the proliferation of effector cells in a contact-dependent manner, and in vivo adding the CD137(pos)CD44(hi) CD4 cells to CD137(neg)CD44(hi) CD4 cells suppressed the antitumor immune response. Thus, CD137 expression on CD4 T cells defined a population of activated T(regs) that greatly limited antitumor immune responses. Consistent with observations in the murine model, human lymphoma biopsies also contained a population of CD137(pos) CD4 T cells that were predominantly CD25(pos)FoxP3(pos) T(regs). In conclusion, our findings identify 2 surface markers that can be used to facilitate the enrichment of antitumor CD4 T cells while depleting an inhibitory T(reg) population.

Adjuvants for enhancing the immunogenicity of whole tumor cell vaccines

Whole tumor cell lysates can serve as excellent multivalent vaccines for priming tumor-specific CD8(+) and CD4(+) T cells. Whole cell vaccines can be prepared with hypochlorous acid oxidation, UVB-irradiation and repeat cycles of freeze and thaw. One major obstacle to successful immunotherapy is breaking self-tolerance to tumor antigens. Clinically approved adjuvants, including Montanide™ ISA-51 and 720, and keyhole-limpet proteins can be used to enhance tumor cell immunogenicity by stimulating both humoral and cellular anti-tumor responses. Other potential adjuvants, such as Toll-like receptor agonists (e.g., CpG, MPLA and PolyI:C), and cytokines (e.g., granulocyte-macrophage colony stimulating factor), have also been investigated.

CD4 T cell dependent tumor immunity stimulated by dendritic cell based vaccine

CD8 CTLs have been accountable for the major effector cells responsible for the rejection of tumor cells. And CD40 signaling and IL-12 have been shown to be the essential pathways involved in the activation process. Immunizing mice with dendritic cells transduced with an adenovirus expressing the human melanoma antigen gp 100, an immunization strategy of xenoimmunization, stimulated potent tumor protection dependent on effective CD4 T cells in the absence of CD8 T cells. Further studies revealed that neither CD40 signaling nor IL-12 was indispensable for the activation of dendritic and CD4 T cells in this model. Stimulation of effective antitumor immunity targeting the self-antigen did not elicit autoimmunity. The implications of this study were discussed.