PDF file - 72KB, Phenotype of in vitro stimulated T cells.

PDF file - 65KB, Analysis of maturation markers in dendritic cells pulsed with RNA and cultured in maturation cytokine cocktail.

Figure S1 - Schematic illustrating the timeline of tumor implantation, immune reconstitution, and bi-scFv treatment for the U87-MG-EGFRvIII, U87-MG, and D270 efficacy studies shown in Figure 7.

Patient weight distribution and weight-based ATCT infusion counts.

PDF file - 47KB, Patient characteristics.

Ex vivo analysis of CMV pp65-specific CD8+ T cells in circulation before and after immunotherapy.

Table S2 - Glioma cell lines and patient derived tumor samples used for study with the number of EGFRvIII receptors per cell, the number of EGFRwt receptors per cell and the proportion of cells expressing EGFRvIII in the given cell line or tumor sample.

DC vaccination enhances the proportion of CMV pp65-specific CD8+ T cells with multiple effector functions

PDF file - 69KB, Cytokine secretion analysis of CMV pp65-specific T cells co-cultured with primary GBM tumor cells.

Table S1 - Construct design, expression parameters and associated binding kinetic and purification yield outcomes for each of the constructs tested as part of this study.

Abstract Median survival for glioblastoma (GBM) remains <15 months. Human cytomegalovirus (CMV) antigens have been identified in GBM but not normal brain, providing an unparalleled opportunity to subvert CMV antigens as tumor-specific immunotherapy targets. A recent trial in recurrent GBM patients demonstrated the potential clinical benefit of adoptive T-cell therapy (ATCT) of CMV phosphoprotein 65 (pp65)–specific T cells. However, ex vivo analyses from this study found no change in the capacity of CMV pp65-specific T cells to gain multiple effector functions or polyfunctionality, which has been associated with superior antitumor efficacy. Previous studies have shown that dendritic cells (DC) could further enhance tumor-specific CD8+ T-cell polyfunctionality in vivo when administered as a vaccine. Therefore, we hypothesized that vaccination with CMV pp65 RNA-loaded DCs would enhance the frequency of polyfunctional CMV pp65-specific CD8+ T cells after ATCT. Here, we report prospective results of a pilot trial in which 22 patients with newly diagnosed GBM were initially enrolled, of which 17 patients were randomized to receive CMV pp65-specific T cells with CMV-DC vaccination (CMV-ATCT-DC) or saline (CMV-ATCT-saline). Patients who received CMV-ATCT-DC vaccination experienced a significant increase in the overall frequencies of IFNγ+, TNFα+, and CCL3+ polyfunctional, CMV-specific CD8+ T cells. These increases in polyfunctional CMV-specific CD8+ T cells correlated (R = 0.7371, P = 0.0369) with overall survival, although we cannot conclude this was causally related. Our data implicate polyfunctional T-cell responses as a potential biomarker for effective antitumor immunotherapy and support a formal assessment of this combination approach in a larger randomized study. Significance: A randomized pilot trial in patients with GBM implicates polyfunctional T-cell responses as a biomarker for effective antitumor immunotherapy. Cancer Res; 78(1); 256–64. ©2017 AACR.

Abstract Purpose: Conventional therapy for malignant glioma fails to specifically target tumor cells. In contrast, substantial evidence indicates that if appropriately redirected, T cells can precisely eradicate tumors. Here we report the rational development of a fully human bispecific antibody (hEGFRvIII-CD3 bi-scFv) that redirects human T cells to lyse malignant glioma expressing a tumor-specific mutation of the EGFR (EGFRvIII). Experimental Design: We generated a panel of bispecific single-chain variable fragments and optimized design through successive rounds of screening and refinement. We tested the ability of our lead construct to redirect naïve T cells and induce target cell–specific lysis. To test for efficacy, we evaluated tumor growth and survival in xenogeneic and syngeneic models of glioma. Tumor penetrance following intravenous drug administration was assessed in highly invasive, orthotopic glioma models. Results: A highly expressed bispecific antibody with specificity to CD3 and EGFRvIII was generated (hEGFRvIII-CD3 bi-scFv). Antibody-induced T-cell activation, secretion of proinflammatory cytokines, and proliferation was robust and occurred exclusively in the presence of target antigen. hEGFRvIII-CD3 bi-scFv was potent and target-specific, mediating significant lysis of multiple malignant glioma cell lines and patient-derived malignant glioma samples that heterogeneously express EGFRvIII. In both subcutaneous and orthotopic models, well-engrafted, patient-derived malignant glioma was effectively treated despite heterogeneity of EGFRvIII expression; intravenous hEGFRvIII-CD3 bi-scFv administration caused significant regression of tumor burden (P < 0.0001) and significantly extended survival (P < 0.0001). Similar efficacy was obtained in highly infiltrative, syngeneic glioma models, and intravenously administered hEGFRvIII-CD3 bi-scFv localized to these orthotopic tumors. Conclusions: We have developed a clinically translatable bispecific antibody that redirects human T cells to safely and effectively treat malignant glioma. On the basis of these results, we have developed a clinical study of hEGFRvIII-CD3 bi-scFv for patients with EGFRvIII-positive malignant glioma. Clin Cancer Res; 24(15); 3611–31. ©2018 AACR.

The ELISpot assay prevails as one of the most sensitive and meaningful assays for the detection of antigen-specific, effector immune responses. Acquisition of cellular analyte for ELISpot analysis is typically not problematic when derived from tissues enriched in lymphocytes (e.g., lymphoid organs and blood); however, cell processing becomes more difficult when lymphocytes represent only a very minor population relative to the source tissue, especially when the source tissue is in limited supply (e.g., small mouse tumors). Traditional enzymatic-based methods for dissociating tumors often result in poor yields, inconsistent lymphocyte enrichment, and can have deleterious effects on lymphocyte phenotype and function. To address these limitations, we have developed an enzyme-free protocol for processing tumor infiltrating lymphocytes (TILs) from small mouse tumors, which enables the enumeration of antigen-specific effector lymphocytes using ELISpot analysis. This procedure is predicated on the dissociation of tumor tissue using gentle agitation with a paddle blender followed by a brief in vitro culture period to remove adherent cells, as well as to revive lymphocytes from a non-responsive state. Although this method is demonstrated with mouse intracerebral tumors, we have found that this protocol is applicable to peripheral tumors and may likely extend to alternative tissue sources wherein lymphocytes exist in low numbers.

We evaluated circulating levels of immunosuppressive regulatory T cells (Tregs) and other lymphocyte subsets in patients with newly diagnosed medulloblastoma (MBL) undergoing surgery compared to a control cohort of patients undergo craniectomy for correction of Chiari malformation (CM) and further determined the impact of standard irradiation and chemotherapy on this cell population.

Abstract Purpose: Patients with glioblastoma have less than 15-month median survival despite surgical resection, high-dose radiation, and chemotherapy with temozolomide. We previously demonstrated that targeting cytomegalovirus pp65 using dendritic cells (DC) can extend survival and, in a separate study, that dose-intensified temozolomide (DI-TMZ) and adjuvant granulocyte macrophage colony-stimulating factor (GM-CSF) potentiate tumor-specific immune responses in patients with glioblastoma. Here, we evaluated pp65-specific cellular responses following DI-TMZ with pp65-DCs and determined the effects on long-term progression-free survival (PFS) and overall survival (OS). Experimental Design: Following standard-of-care, 11 patients with newly diagnosed glioblastoma received DI-TMZ (100 mg/m2/d × 21 days per cycle) with at least three vaccines of pp65 lysosome–associated membrane glycoprotein mRNA-pulsed DCs admixed with GM-CSF on day 23 ± 1 of each cycle. Thereafter, monthly DI-TMZ cycles and pp65-DCs were continued if patients had not progressed. Results: Following DI-TMZ cycle 1 and three doses of pp65-DCs, pp65 cellular responses significantly increased. After DI-TMZ, both the proportion and proliferation of regulatory T cells (Tregs) increased and remained elevated with serial DI-TMZ cycles. Median PFS and OS were 25.3 months [95% confidence interval (CI), 11.0–∞] and 41.1 months (95% CI, 21.6–∞), exceeding survival using recursive partitioning analysis and matched historical controls. Four patients remained progression-free at 59 to 64 months from diagnosis. No known prognostic factors [age, Karnofsky performance status (KPS), IDH-1/2 mutation, and MGMT promoter methylation] predicted more favorable outcomes for the patients in this cohort. Conclusions: Despite increased Treg proportions following DI-TMZ, patients receiving pp65-DCs showed long-term PFS and OS, confirming prior studies targeting cytomegalovirus in glioblastoma. Clin Cancer Res; 23(8); 1898–909. ©2017 AACR.

Regulatory B cells that secrete IL-10 (IL-10 + B regs ) represent a suppressive subset of the B cell compartment with prominent anti-inflammatory capacity, capable of suppressing cellular and humoral responses to cancer and vaccines. B lymphocyte stimulator (BLyS) is a key regulatory molecule in IL-10 + B reg biology with tightly controlled serum levels. However, BLyS levels can be drastically altered upon chemotherapeutic intervention. We have previously shown that serum BLyS levels are elevated, and directly associated, with increased antigen-specific antibody titers in patients with glioblastoma (GBM) undergoing lymphodepletive temozolomide chemotherapy and vaccination. In this study, we examined corresponding IL-10 + B reg responses within this patient population and demonstrate that the IL-10 + B reg compartment remains constant before and after administration of the vaccine, despite elevated BLyS levels in circulation. IL-10 + B reg frequencies were not associated with serum BLyS levels, and ex vivo stimulation with a physiologically relevant concentration of BLyS did not increase IL-10 + B reg frequency. However, BLyS stimulation did increase the frequency of the overall B cell compartment and promoted B cell proliferation upon B cell receptor engagement. Therefore, using BLyS as an adjuvant with therapeutic peptide vaccination could promote humoral immunity with no increase in immunosuppressive IL-10 + B regs . These results have implications for modulating humoral responses in human peptide vaccine trials in patients with GBM.

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.

Abstract Purpose: Despite aggressive conventional therapy, glioblastoma (GBM) remains uniformly lethal. Immunotherapy, in which the immune system is harnessed to specifically attack malignant cells, offers a treatment option with less toxicity. The expression of cytomegalovirus (CMV) antigens in GBM presents a unique opportunity to target these viral proteins for tumor immunotherapy. Although the presence of CMV within malignant gliomas has been confirmed by several laboratories, its relevance as an immunologic target in GBM has yet to be established. The objective of this study was to explore whether T cells stimulated by CMV pp65 RNA-transfected dendritic cells (DC) target and eliminate autologous GBM tumor cells in an antigen-specific manner. Experimental Design: T cells from patients with GBM were stimulated with autologous DCs pulsed with CMV pp65 RNA, and the function of the effector CMV pp65-specific T cells was measured. Results: In this study, we demonstrate the ability to elicit CMV pp65-specific immune responses in vitro using RNA-pulsed autologous DCs generated from patients with newly diagnosed GBM. Importantly, CMV pp65-specific T cells lyse autologous, primary GBM tumor cells in an antigen-specific manner. Moreover, T cells expanded in vitro using DCs pulsed with total tumor RNA demonstrated a 10- to 20-fold expansion of CMV pp65-specific T cells as assessed by tetramer analysis and recognition and killing of CMV pp65-expressing target cells. Conclusion: These data collectively demonstrate that CMV-specific T cells can effectively target glioblastoma tumor cells for immunologic killing and support the rationale for the development of CMV-directed immunotherapy in patients with GBM. Clin Cancer Res; 20(10); 2684–94. ©2014 AACR.

BACKGROUND: Immunotherapy promises an exquisitely precise therapeutic approach, and substantial evidence suggests that activated T cells can eradicate large tumors, even within the “immunologically privileged” brain. EGFRvIII and isocitrate dehydrogenase 1 (IDH1) mutations are two of the only consistent tumor-specific mutations that have been described. IDH1 is an evolutionarily-conserved enzyme essential to cell function. Greater than 90% of all IDH1 mutations occur from a substitution of histidine for arginine at codon 132, resulting in the highly conserved and tumor-specific mutation, IDH1R132H. IDH1R132H is homogeneously expressed in all tumor cells in tumors that express this mutation, including single infiltrating tumor cells but is absent in normal cells. The high frequency, specificity, and homogeneous expression of the IDH1 mutation make it an ideal target for therapeutic intervention. METHODS: To assess IDH1R132H as an immunotherapeutic target, we have developed a series of peptides of various lengths that span the IDH1R123H mutation and that are homologous in mice and humans. The murine homologue of IDH1R123H was cloned and transfected into murine glioma lines to be used as a therapeutic target. For immunogenicity experiments mice received 3 weekly intradermal immunizations with 100 µg of peptide. One week following the third vaccination spleen cells were analyzed for interferon gamma (IFN-γ) production by ELISPOT. Adjuvants investigated included CFA/IFA/IFA, IFA x3, IFA + GM-CSF, and IFA x3 following pretreatment with Imiquimod. For efficacy experiments C57BL/6 mice received three i.d. vaccinations with PEPIDH1M in IFA every seven days or no treatment. Seven days after the third vaccination, mice received IC implantation of 5x104 IDH1R132H positive KR158B tumor cells. RESULTS: Lymphocytes from mice immunized with peptides of various lengths containing the IDH1R123H mutation produced IFN-γ by ELISPOT in response to stimulation with the mutant peptide, PEPIDH1M but not wild type. This was true for four different strains of mice and transgenic HLA-A2 mice. The 25mer PEPIDH1M induced the most robust immune response. Lymphocytes derived from PEPIDH1M immunized mice co-cultured with IDH1R132H positive glioma secrete significantly higher levels of IFN-γ than lymphocytes co-cultured with IDH1R132H negative tumor cells. Mice immunized with the 25mer PEPIDH1M mixed with GM-CSF or after treating the skin site with Imiquimod produce a greater IFN-γ response to PEPIDH1M alone. Mice immunized with 25mer PEPIDH1M and challenged 7 days later with KR158B-IDH1R132H tumors showed a statically significant increase in median survival (P = 0.0385, Wilcoxon). CONCLUSIONS: The 25mer PEPIDH1M is capable of inducing a therapeutically effective immune response against intracranial tumors. SECONDARY CATEGORY: Preclinical Experimental Therapeutics.