Recognition and killing of autologous, primary glioblastoma tumor cells by human cytomegalovirus pp65-specific cytotoxic T cells

Evaluation of JC and Cytomegalo Viruses in Glioblastoma Tissue

Glioblastoma multiforme (GBM) is the most aggressive of the gliomas, a collection of tumors arising from glia in the central nervous system. Possible associations between the human cytomegalovirus (HCMV) and the JC virus with GBM are now attracting interest. Our present aim was to investigate the prevalence of the two viruses in Iranian patients from Kerman’s cities in the south of Iran. In addition, the expression rates of pp65, large T antigen and p53 proteins were assessed and their relation with GBM evaluated using reverse transcription real time PCR (rReal Time PCR) . A total of 199 patients with GBM cancer were enrolled, with mean±SD ages of 50.0±19.5 and 50.7±19.6 years for males and females, respectively. The P53 rate was dramatically low suggesting an aetiological role,. Large T antigen expression was found in JC positive samples, while the PP65 antigen was observed in patients positive for CMV and JC . HCMV products and JC virus with oncogenic potential may induce the development of various tumors including glioblastomas. The JC virus produces an early gene product, T-antigen, which has the ability to associate with and functionally inactivate well-studied tumor suppressor proteins including p53 and pRB .

Tumor antigen-specific T cells for immune monitoring of dendritic cell-treated glioblastoma patients

BACKGROUND AIMS

CD8(+) T cells are part of the adaptive immune system and, as such, are responsible for the elimination of tumor cells. Dendritic cells (DC) are professional antigen-presenting cells (APC) that activate CD8(+) T cells. Effector CD8(+) T cells in turn mediate the active immunotherapeutic response of DC vaccination against the aggressive glioblastoma (GBM). The lack of tumor response assays complicates the assessment of treatment success in GBM patients.

METHODS

A novel assay to identify specific cytotoxicity of activated T cells by APC was evaluated. Tumor antigen-pulsed DCs from HLA-A*02-positive GBM patients were cultivated to stimulate autologous cytotoxic T lymphocytes (CTL) over a 12-day culture period. To directly correlate antigen specificity and cytotoxic capacity, intracellular interferon (IFN)-γ fluorescence flow cytometry-based measurements were combined with anti-GBM tumor peptide dextramer staining. IFN-γ response was quantified by real-time polymerase chain reaction (PCR), and selected GBM genes were compared with healthy human brain cDNA by single specific primer PCR characterization.

RESULTS

Using CTL of GBM patients stimulated with GBM lysate-pulsed DCs increased IFN-γ messenger RNA levels, and intracellular IFN-γ protein expression was positively correlated with specificity against GBM antigens. Moreover, the GBM peptide-specific CD8(+) T-cell response correlated with specific GBM gene expression. Following DC vaccination, GBM patients showed 10-fold higher tumor-specific signals compared with unvaccinated GBM patients.

DISCUSSION

These data indicate that GBM tumor peptide-dextramer staining of CTL in combination with intracellular IFN-γ staining may be a useful tool to acquire information on whether a specific tumor antigen has the potential to induce an immune response in vivo.

Prioritization schema for immunotherapy clinical trials in glioblastoma

BACKGROUND

Emerging immunotherapeutic strategies for the treatment of glioblastoma (GBM) such as dendritic cell (DC) vaccines, heat shock proteins, peptide vaccines, and adoptive T-cell therapeutics, to name a few, have transitioned from the bench to clinical trials. With upcoming strategies and developing therapeutics, it is challenging to critically evaluate the practical, clinical potential of individual approaches and to advise patients on the most promising clinical trials.

METHODS

The authors propose a system to prioritize such therapies in an organized and data-driven fashion. This schema is based on four categories of factors: antigenic target robustness, immune-activation and -effector responses, preclinical vetting, and early evidence of clinical response. Each of these categories is subdivided to focus on the most salient elements for developing a successful immunotherapeutic approach for GBM, and a numerical score is generated.

RESULTS

The Score Card reveals therapeutics that have the most robust data to support their use, provides a reference prioritization score, and can be applied in a reiterative fashion with emerging data.

CONCLUSIONS

The authors hope that this schema will give physicians an evidence-based and rational framework to make the best referral decisions to better guide and serve this patient population.

Immunotherapy for cancer in the central nervous system: Current and future directions

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults and still remains incurable. Although immunotherapeutic vaccination against GBM has demonstrated immune-stimulating activity with some promising survival benefits, tumor relapse is common, highlighting the need for additional and/or combinatorial approaches. Recently, antibodies targeting immune checkpoints were demonstrated to generate impressive clinical responses against advanced melanoma and other malignancies, in addition to showing potential for enhancing vaccination and radiotherapy (RT). Here, we summarize the current knowledge of central nervous system (CNS) immunosuppression, evaluate past and current immunotherapeutic trials and discuss promising future immunotherapeutic directions to treat CNS-localized malignancies.

Cytomegalovirus and immunotherapy: opportunistic pathogen, novel target for cancer and a promising vaccine vector

Cytomegalovirus (CMV) is a β-herpesvirus that infects most people in the world and is almost always asymptomatic in the healthy host. However, CMV persists for life, requiring continuous immune surveillance to prevent disease and thus, CMV is a frequent complication in immune compromised patients. Many groups have been exploring the potential for adoptive T-cell therapies to control CMV reactivation as well as the progression of solid tumors harboring CMV. In addition, CMV itself is being explored as a vaccine vector for eliciting potent T-cell responses. This review will discuss key features of the basic biology of CMV-specific T cells as well as highlighting unanswered questions and ongoing work in the development of T-cell-based immunotherapies to target CMV.

Preconditioning Vaccine Sites for mRNA-Transfected Dendritic Cell Therapy and Antitumor Efficacy

Messenger RNA (mRNA)-transfected dendritic cell (DC) vaccines have been shown to be a powerful modality for eliciting antitumor immune responses in mice and humans; however, their application has not been fully optimized since many of the factors that contribute to their efficacy remain poorly understood. Work stemming from our laboratory has recently demonstrated that preconditioning the vaccine site with a recall antigen prior to the administration of a dendritic cell vaccine creates systemic recall responses and resultantly enhances dendritic cell migration to the lymph nodes with improved antitumor efficacy. This chapter describes the generation of murine mRNA-transfected DC vaccines, as well as a method for vaccine site preconditioning with protein antigen formulations that create potent recall responses.

Principles of immunotherapy

Gliomas are the most common primary brain tumors of the central nervous system, and carry a grim prognosis. Novel approaches utilizing the immune system as adjuvant therapy are quickly emerging as viable and effective options. Immunotherapeutic strategies being investigated to treat glioblastoma include: vaccination therapy targeted against either specific tumor antigens or whole tumor lysate, adoptive cellular therapy with cytotoxic T lymphocytes, chimeric antigen receptors and bi-specific T-cell engaging antibodies allowing circumvention of major histocompatibility complex restriction, aptamer therapy with aims for more efficient target delivery, and checkpoint blockade in order to release the tumor-mediated inhibition of the immune system. Given the heterogeneity of glioblastoma and its ability to gain mutations throughout the disease course, multifaceted treatment strategies utilizing multiple forms of immunotherapy in combination with conventional therapy will be most likely to succeed moving forward.

Ex vivo generation of dendritic cells from cryopreserved, post-induction chemotherapy, mobilized leukapheresis from pediatric patients with medulloblastoma

Generation of patient-derived, autologous dendritic cells (DCs) is a critical component of cancer immunotherapy with ex vivo-generated, tumor antigen-loaded DCs. An important factor in the ability to generate DCs is the potential impact of prior therapies on DC phenotype and function. We investigated the ability to generate DCs using cells harvested from pediatric patients with medulloblastoma for potential evaluation of DC-RNA based vaccination approach in this patient population. Cells harvested from medulloblastoma patient leukapheresis following induction chemotherapy and granulocyte colony stimulating factor mobilization were cryopreserved prior to use in DC generation. DCs were generated from the adherent CD14+ monocytes using standard procedures and analyzed for cell recovery, phenotype and function. To summarize, 4 out of 5 patients (80%) had sufficient monocyte recovery to permit DC generation, and we were able to generate DCs from 3 out of these 4 patient samples (75%). Overall, we successfully generated DCs that met phenotypic requisites for DC-based cancer therapy from 3 out of 5 (60%) patient samples and met both phenotypic and functional requisites from 2 out of 5 (40%) patient samples. This study highlights the potential to generate functional DCs for further clinical treatments from refractory patients that have been heavily pretreated with myelosuppressive chemotherapy. Here we demonstrate the utility of evaluating the effect of the currently employed standard-of-care therapies on the ex vivo generation of DCs for DC-based clinical studies in cancer patients.

Poor survival in glioblastoma patients is associated with early signs of immunosenescence in the CD4 T-cell compartment after surgery

Patients with glioblastoma multiforme (GBM) are immunosuppressed and have a broad range of immunological defects in both innate and adaptive immune responses. GBMs are frequently infected with human cytomegalovirus (HCMV), a virus capable of causing immunosuppression. In 42 HCMV-positive GBM patients in a clinical trial (VIGAS), we investigated T-cell phenotypes in the blood and assessed their relation to survival. Blood was collected before and 3, 12, and 24 weeks after surgery, and the frequency of T-cell subsets was compared with that in 26 age-matched healthy controls. GBM patients had lower levels of CD3 cells than the controls, but had significantly higher levels of CD4⁺CD28^- T cells before and 3 and 12 weeks after surgery and increased levels of CD4⁺CD57⁺ and CD4⁺CD57⁺CD28⁺ T cells at all-time points. These T-cell subsets were associated with both immunosenescence and HCMV infection. GBM patients also had higher levels of γδ T cells at all-times after surgery and lower levels of CD4⁺CD25⁺ cells before and 3 weeks after surgery than healthy controls. Overall survival was significantly shorter in patients with higher levels of CD4⁺CD28^- T cells (p = 0.025), CD4⁺CD57⁺ T (p = 0.025) cells, and CD4⁺CD28^-CD57⁺CD28^- T cells (p < 0.0004) at 3 weeks after surgery. Our findings indicate that signs of immunosenescence in the CD4⁺ compartment are associated with poor prognosis in patients with HCMV-positive GBMs and may reflect the HCMV activity in their tumors.

Cytomegalovirus in human brain tumors: Role in pathogenesis and potential treatment options

During the last years increasing evidence implies that human cytomegalovirus (CMV) can be attributed to human malignancies arising from numerous tissues. In this perspective, we will review and discuss the potential mechanisms through which CMV infection may contribute to brain tumors by affecting tumor cell initiation, progression and metastasis formation. Recent evidence also suggests that anti-CMV treatment results in impaired tumor growth of CMV positive xenografts in animal models and potentially increased survival in CMV positive glioblastoma patients. Based on these observations and the high tumor promoting capacity of this virus, the classical and novel antiviral therapies against CMV should be revisited as they may represent a great promise for halting tumor progression and lower cancer deaths.

Severe adverse immunologic reaction in a patient with glioblastoma receiving autologous dendritic cell vaccines combined with GM-CSF and dose-intensified temozolomide

Therapeutic vaccination of patients with cancer-targeting tumor-associated antigens is a promising strategy for the specific eradication of invasive malignancies with minimal toxicity to normal tissues. However, as increasingly potent modalities for stimulating immunologic responses are developed for clinical evaluation, the risk of inflammatory and autoimmune toxicities also may be exacerbated. In this report, we describe the induction of a severe (grade 3) immunologic reaction in a patient with newly diagnosed glioblastoma (GBM) receiving autologous RNA-pulsed dendritic cell (DC) vaccines admixed with GM-CSF and administered coordinately with cycles of dose-intensified temozolomide. Shortly after the eighth administration of the admixed intradermal vaccine, the patient experienced dizziness, flushing, conjunctivitis, headache, and the outbreak of a disseminated macular/papular rash and bilateral indurated injection sites. Immunologic workup of patient reactivity revealed sensitization to the GM-CSF component of the vaccine and the production of high levels of anti-GM-CSF autoantibodies during vaccination. Removal of GM-CSF from the DC vaccine allowed continued vaccination without incident. Despite the known lymphodepletive and immunosuppressive effects of temozolomide, these observations demonstrate the capacity for the generation of severe immunologic reactivity in patients with GBM receiving DC-based therapy during adjuvant dose-intensified temozolomide.

Cytomegalovirus as a novel target for immunotherapy of glioblastoma multiforme

Progress in the treatment of glioblastoma multiforme (GBM) over the last few decades has remained marginal and GBM is still universally fatal with short survival times after initial diagnosis. Much research is focused on finding new therapeutics for GBM and immune-based approaches have shown great promise. The detection of cytomegalovirus (CMV) antigens in malignant cells has suggested that treatment strategies based on immunological intervention, such as adoptive transfer of antiviral T cells or vaccination with viral epitopes, could be exploited as cancer therapy. Here, we review the rationale for using CMV as a therapeutic target and discuss the first clinical evidence for safety and efficacy of CMV-specific cellular immunotherapy for GBM.

Immunoglobulin GM Genes, Cytomegalovirus Immunoevasion, and the Risk of Glioma, Neuroblastoma, and Breast Cancer

Human cytomegalovirus (HCMV), a common herpes virus, has been reported to be a risk factor for many diseases, including malignant diseases such as glioma, neuroblastoma, and breast cancer. Some of the HCMV-associated diseases (e.g., glioma) are rare. The question arises: how could a common virus be associated with uncommon diseases? Interactions between a major gene complex of the human immune system and a viral immunoevasion strategy – a probable mechanism of their co-evolutionary adaptation – may shed light on this paradox. To ensure its survival, HCMV has evolved sophisticated immunoevasion strategies. One strategy involves encoding decoy Fcγ receptors (FcγR), which may enable the virus to evade host immunosurveillance by avoiding the Fcγ-mediated effector consequences of anti-HCMV IgG antibody binding. Immunoglobulin G1 proteins expressing GM (γ marker) alleles 3 and 17 have differential affinity to the HCMV TRL11/IRL11-encoded FcγR, and thus act as effect modifiers of HCMV-associated malignancies. The high affinity GM 3 allele has been shown to be a risk factor for neuroblastoma, glioma, and breast cancer. Additional studies involving other viral FcγRs as well as GM alleles expressed on other IgG subclasses are warranted.

Metabolic therapy: a new paradigm for managing malignant brain cancer

Little progress has been made in the long-term management of glioblastoma multiforme (GBM), considered among the most lethal of brain cancers. Cytotoxic chemotherapy, steroids, and high-dose radiation are generally used as the standard of care for GBM. These procedures can create a tumor microenvironment rich in glucose and glutamine. Glucose and glutamine are suggested to facilitate tumor progression. Recent evidence suggests that many GBMs are infected with cytomegalovirus, which could further enhance glucose and glutamine metabolism in the tumor cells. Emerging evidence also suggests that neoplastic macrophages/microglia, arising through possible fusion hybridization, can comprise an invasive cell subpopulation within GBM. Glucose and glutamine are major fuels for myeloid cells, as well as for the more rapidly proliferating cancer stem cells. Therapies that increase inflammation and energy metabolites in the GBM microenvironment can enhance tumor progression. In contrast to current GBM therapies, metabolic therapy is designed to target the metabolic malady common to all tumor cells (aerobic fermentation), while enhancing the health and vitality of normal brain cells and the entire body. The calorie restricted ketogenic diet (KD-R) is an anti-angiogenic, anti-inflammatory and pro-apoptotic metabolic therapy that also reduces fermentable fuels in the tumor microenvironment. Metabolic therapy, as an alternative to the standard of care, has the potential to improve outcome for patients with GBM and other malignant brain cancers.

Cellular immunotherapy directed against human cytomegalovirus as a novel approach for glioblastoma treatment

Glioblastoma multiforme (GBM) has a very poor prognosis, despite multimodal therapy including surgery, radiation and chemotherapy. A novel adoptive immunotherapy that exploits the presence of cytomegalovirus antigens in malignant brain cancer cells has been shown to be safe and elicit potential clinical benefit for the treatment of recurrent GBM.

Immunological targeting of cytomegalovirus for glioblastoma therapy

Human cytomegalovirus (CMV) is purportedly present in glioblastoma (GBM) while absent from the normal brain, making CMV antigens potentially ideal immunological anti-GBM targets. We recently demonstrated that patient-derived CMV pp65-specific T cells are capable of recognizing and killing autologous GBM tumor cells. This data supports CMV antigen-directed immunotherapies against GBM.